nmorel-honours project
TRANSCRIPT
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Energy Independent Wooden House
Author: Nicolas Morel Supervisor: Mr. Dylan Ryan
Matriculation: 40175752 Second Reader: Mr. Colin McGill
Edinburgh Napier University Beng (Hons) Degree in Energy Engineering
School of Engineering and Built Environment
April 2016
2016
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Acknowledgements
I would like to first thank my supervisor Mr. Dylan Ryan for his disponibility which made
regular meetings possible and for his guidance during the completion of this final year
project.
Besides my supervisor, I would like to thank Mr. Tariq Muneer who also provided me
technical aid.
My sincere thanks also goes to Abdullah Miqdad, Hannah Wade for their suggestions
and Remi Chataing who challenged my ideas.
Finally, my thanks go to my family: my parents and sister, for their constant support
throughout life and without whom, none of this would have been possible.
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Abstract
A 30 m2 typical secondary wooden chalet is localized in Villard-de-Lans, in the French
Alps. Being far from the urban area, the house is not supplied in electricity neither in any
other sources of energy except a wood stove burner considered as a back-up solution. It
is consequently uninhabitable as no system is able to insure space or domestic water
heating necessary to provide the occupants with vital needs.
The solar power, clean and abundant resource especially at this location, is commonly
used for this purpose. It can be utilised in different ways of which the ground (warmed by
the sun), the thermal for heating space and water, and the photovoltaic for producing
electricity required to run different systems as it is the case of an off-grid installation.
In order to complete the tasks as well as possible, the feasibility of these three techniques
and their cost will be studied in this report, based on the analysis of heat losses of the
house and the needs in hot water and electricity.
As a first option, a solar photovoltaic (PV) system will be combined with a solar thermal
installation providing hot water, and an electric system for space heating. In the second
option, the PV system is combined with a ground source heat pump which allows both
types space and water heating.
After sizing adequately the different heating systems, it results that the second option was
the least electrically demanding over the year. It allowed four persons to live in the house
at any time between the months of February and October, inducing an investment of
about £15,000.
For £3,000 cheaper, the other option made the inhabitation possible from April to
September. As a notice, the wood strove burner could add two more months to the period
in each case.
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Table of Contents
1 Chapter One: Introduction ........................................................................................ 9
2 Chapter Two: Literature Review ............................................................................. 11
2.1 Solar Thermal Energy ...................................................................................... 11
2.2 Solar Photovoltaic Energy ................................................................................ 14
2.3 Solar data ......................................................................................................... 18
2.4 Ground Source Heat pump .............................................................................. 20
3 Chapter Three: Implementation .............................................................................. 24
3.1 House Characteristics And Dimensions ........................................................... 24
3.2 Solar Collecting Data ....................................................................................... 27
3.3 Analysis of the Needs ...................................................................................... 30
3.4 Solar Thermal Study ........................................................................................ 41
3.5 Ground Source Heat Pump Study .................................................................... 44
3.6 Solar Photovoltaic Study .................................................................................. 50
4 Chapter Four: Results and Findings ....................................................................... 54
4.1 Needs Analysis ................................................................................................ 54
4.2 Solar Thermal Study ........................................................................................ 57
4.3 Ground Source Heat Pump Study .................................................................... 60
4.4 Solar Photovoltaic Study .................................................................................. 62
4.5 Economic Analysis ........................................................................................... 70
5 Chapter five: Conclusion ......................................................................................... 73
5.1 Analysis ............................................................................................................ 73
5.2 Limitations ........................................................................................................ 75
5.3 Further work ..................................................................................................... 75
6 Bibliography ............................................................................................................ 76
7 Appendix A – House Solar Gains and Heat Losses ...........................................................78
8 Appendix B – Solar Thermal System Elements (1) .............................................................79
9 Appendix C - Solar Thermal System Elements (2) .............................................................80
10 Appendix D – GSHP Circuit Elements (1) ......................................................................81
11 Appendix E - GSHP Circuit Elements (2) .......................................................................82
12 Appendix F – PV Systems Elements (1) ........................................................................83
13 Appendix G – PV Systems Elements (2) .......................................................................84
14 Appendix E – Biowatt Energie Mail Exchange ...............................................................85
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Abbreviations
PV PhotoVoltatic
Ah Ampere hours
DC Direct Current
AC Alternative Current
DoD Depth of Discharge
GSHP Ground Source Heat Pump
MPPt Maximum Power Point tracker
Symbols
p – n postive – negative
C20 Battery capacity for a discharge over 20 hours
G Monthly-averaged daily solar radiation (kWh/m²/day)
k Thermal conductivity (W/m.K)
𝐼𝐺 Global solar irradiation hourly values (W/m²)
𝐼𝐷 Diffuse solar irradiation hourly values (W/m²)
𝐼𝐸 Extra-terrestrial irradiation hourly values (W/m²)
𝐼𝑏𝑒𝑎𝑚 Direct solar irradiation (W/m²)
𝐼𝑠𝑘𝑦 𝑑𝑖𝑓𝑓 Sky diffuse solar irradiation (W/m²)
𝐼𝑔𝑟𝑜𝑢𝑛𝑑 𝑟𝑒𝑓 Ground reflected solar irradiation (W/m²)
𝑇𝜃 Light glass transmission
𝜏𝑔𝑟𝑜𝑢𝑛𝑑 𝑟𝑒𝑓 Glass transmission coefficient of the ground reflected light
𝜏𝑠𝑘𝑦 𝑑𝑖𝑓𝑓 Glass transmission coefficient of the sky diffused light
�̅� Monthly-averaged diffuse ratio
𝑘𝑇̅̅̅̅ Monthly-averaged clearness index
𝑇𝜃 Transmission a pane of glass
𝑞𝑐𝑜𝑛𝑑 Rate of heat transfer by conduction (W)
𝑞𝑐𝑜𝑛𝑣 Rate of heat transfer by convection (W)
𝑒 Thickness (m)
𝑇𝑓 Film temperature (K)
ρ Density (kg/m3)
Cp Specific heat (J/kg.K)
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µ Dynamic viscosity (Pa.s)
ν Kinematic viscosity (m2/s)
α Thermal diffusity (m2/s)
β Volumetric thermal expansion coefficient (K-1)
𝑅𝑎 Rayleigh number
𝑅𝑒 Reynold number
𝑁𝑢 Nusselt number
ℎ𝑖 Internal heat transfer coefficient (W/m2.K)
U Thermal transmittance (W/m²K)
𝑅𝑐𝑜𝑛𝑑 Conduction resistance (W/m.K)
𝑅𝑐𝑜𝑛𝑣 Convection resistance (W/m.K)
Q Heat losses rate
g Gravitational acceleration (m/s2)
𝜀ℎ Hemispherical emissivity
ℎ𝑟 Internal radiation heat transfer coefficient (W/m2.K)
ℎ𝑟0 External radiation heat transfer coefficient (W/m2.K)
σ Stefan-Boltzmann constant (W/m2.K-*4)
n Air change rate per hour
𝑚 ̇ Mass flow rate (kg/s)
𝑞 Volume flow rate (m3/s)
m Mass (kg)
V Volume (L or m3)
𝑣 Velocity (m/s)
𝑅𝑅 Relative roughness
𝑅𝑠 Surface roughness
𝑓 Friction factor
ℎ Head losss (m)
𝐷𝑖 Internal diameter (m)
𝐷𝑒 External diameter (m)
𝑃𝑜𝑢𝑡 Pump hydraulic output (W)
I Current intensity (A)
V Current voltage (V)
P Power (W)
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List of Figures
FIGURE 1. FLAT PLATE COLLECTOR ........................................................................................................................................ 11 FIGURE 2. EVACUATED TUBE COLLECTOR ............................................................................................................................... 12 FIGURE 3. SOLAR THERMAL SYSTEM ..................................................................................................................................... 13 FIGURE 4. SOLAR ELECTRIC CYLINDER .................................................................................................................................... 14 FIGURE 5. TWIN COIL CYLINDER ........................................................................................................................................... 14 FIGURE 6. PHOTOVOLTAIC PANEL ON-ROOF MOUNTED ............................................................................................................ 14 FIGURE 7. PHOTOVOLTAIC CELL ........................................................................................................................................... 15 FIGURE 8. GENERATION SYSTEM SCHEME .............................................................................................................................. 16 FIGURE 9. MPPT BLUESOLAR............................................................................................................................................. 16 FIGURE 10. INVERTER MULTIPLUS ....................................................................................................................................... 17 FIGURE 11. SOLAR BATTERY RBS-1860 ............................................................................................................................... 17 FIGURE 12. COMPONENTS OF THE SOLAR RADIATION ............................................................................................................... 19 FIGURE 13. GROUND SOURCE HEAT PUMP AND ITS REFRIGERANT CYCLE ...................................................................................... 21 FIGURE 14. WOODEN HOUSE SCHEME .................................................................................................................................. 24 FIGURE 15. WALL MATERIAL COMPOSITION (TO SCALE 1/10) ................................................................................................... 25 FIGURE 16. ROOF MATERIAL COMPOSITION (TO SCALE 1/10) ................................................................................................... 25 FIGURE 17. THERMAL CONDUCTIVITIES OF THE MATERIALS (WIKIPEDIA, 2016) ............................................................................ 25 FIGURE 18. NASA WEBSITE SCREENSHOT .............................................................................................................................. 27 FIGURE 19. HEAT TRANSFER PHENOMENA THROUGH THE WALL ................................................................................................. 32 FIGURE 20. TEMPERATURE PROFILE THROUGH THE WALL.......................................................................................................... 33 FIGURE 21. MONTHLY AVERAGE TEMPERATURES .................................................................................................................... 36 FIGURE 22. HEAT TRANSFER THROUGH THE DOOR ................................................................................................................... 36 FIGURE 23. ROOF 𝜃 ANGLE SKETCH ...................................................................................................................................... 36 FIGURE 24. HEAT TRANSFER THROUGH A WINDOW ................................................................................................................. 37 FIGURE 25. TEMPERATURE PROFILE THROUGH A WINDOW........................................................................................................ 37 FIGURE 26. EXAMPLE OF THERMAL BRIDGES AT WALL/FLOOR JUNCTION ...................................................................................... 38 FIGURE 27. HEAT LOSSES OF A TRADITIONAL HOUSE (ADEME, 2016) ....................................................................................... 39 FIGURE 28. GROUND TEMPERATURE OVER THE YEAR ACCORDING TO THE DEPTH, IN FRANCE (COLLECTEURDEROSEE, 2015) ................. 44 FIGURE 29. PV INSTALLATION SCHEME ................................................................................................................................. 50 FIGURE 30.TOTAL ENERGY GAINED INSIDE THE HOUSE BY MONTH .............................................................................................. 55 FIGURE 31. TOTAL ENERGY LOST BY MONTH .......................................................................................................................... 56 FIGURE 32. ENERGY REQUIRED BY THE IMMERSION HEATER TO PRODUCE THE REST ........................................................................ 58 FIGURE 33. VOLUME OF HOT WATER PRODUCED OVER THE VOLUME REQUIRED, PER DAY (%) .......................................................... 58 FIGURE 34. PERCENTAGE OF THE LOAD COVERED .................................................................................................................... 65 FIGURE 35. PV SYSTEM ELECTRIC INDICATIONS ....................................................................................................................... 66 FIGURE 36. PV SYSTEMS NUMBER OF AUTONOMY DAYS ........................................................................................................... 68 FIGURE 37. FINAL PV DESIGN OVERVIEW .............................................................................................................................. 69
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List of Tables
TABLE 1. SPREADSHEET "CALC4-09" SCREENSHOT .................................................................................................................. 27 TABLE 2. SPREADSHEET CALC4-10 SCREENSHOT ..................................................................................................................... 29 TABLE 3. SLOPE BEAM (W/M²): ASPECT=180° - TILT=90° ...................................................................................................... 30 TABLE 4. SKY DIFFUSE/GROUND REFLECTION (W/M²): ASPECT=180° - TILT=90° ........................................................................ 31 TABLE 5. VALUES OF T (Θ) - ASPECT=180° - TILT=90° ............................................................................................................ 31 TABLE 6. GLASS AREAS AND TRANSMISSION COEFFICIENTS OF RADIATION ..................................................................................... 32 TABLE 7. GLOBAL AND DIFFUSE RADIATIONS (W/M²) FOR EACH MONTH OF THE YEAR AT VILLARD-DE-LANS ....................................... 41 TABLE 8. SLOPE GLOBAL AT VILLARD-DE-LANS (W/M²) - ASPECT=180° - TILT=30° ...................................................................... 41 TABLE 9. HOT WATER PRODUCTION (EXAMPLE) IN L//M² COLLECTOR ......................................................................................... 42 TABLE 10. LISTING OF TEMPERATURES OVER THE YEAR ............................................................................................................. 45 TABLE 11. HOUSE ELECTRIC LOAD ANALYSIS ........................................................................................................................... 51 TABLE 12. ENERGY ENTERING IN THE BUILDING IN KWH, DAILY .................................................................................................. 54 TABLE 13. ENERGY GAINED FROM HUMAN OCCUPATION .......................................................................................................... 54 TABLE 14. OVERALL HEAT LOSSES OF THE HOUSE .................................................................................................................... 55 TABLE 15. HEAT LOSSES, COLDEST DAY SCENARIO 3/1/1971 ................................................................................................... 55 TABLE 16. YEAR AVERAGE HEAT LOSSES REPARTITION (%) ........................................................................................................ 56 TABLE 17. HEAT LOST - HEAT GAINED PER DAY, OVERVIEW ....................................................................................................... 56 TABLE 18. CALCULATION OF THE ENERGY NEEDED FOR HEATING WATER ...................................................................................... 57 TABLE 19. HOURLY PRODUCTION OF HOT WATER (L) ACCORDING TO THE HEAT PRODUCED BY 3M2 COLLECTOR (W) - SOUTH ............... 57 TABLE 20. THERMAL COLLECTOR SPECIFICATIONS .................................................................................................................... 59 TABLE 21. CIRCULATING PUMP SIZING .................................................................................................................................. 59 TABLE 22. GSHP ENERGY PRODUCTION ................................................................................................................................ 60 TABLE 23. CIRCULATING PUMP SIZING .................................................................................................................................. 60 TABLE 24. GSHP SIZING CALCULATIONS ............................................................................................................................... 61 TABLE 25. ELECTRICAL APPLIANCES LOAD ANALYSIS (HEATING SYSTEM NOT INCLUDED) ................................................................... 62 TABLE 26. OPTION 2, TOTAL ELECTRICAL LOAD ANALYSIS (KWH/DAY) ......................................................................................... 63 TABLE 27. OPTION 1, TOTAL ELECTRICAL LOAD ANALYSIS (KWH/DAY) ......................................................................................... 63 TABLE 28. POWER DEMAND ANALYSIS (KW) .......................................................................................................................... 63 TABLE 29. PV SYSTEM EFFICIENCIES ..................................................................................................................................... 64 TABLE 30. PV ENERGY PRODUCTION ANALYSIS ....................................................................................................................... 64 TABLE 31. POWER PRODUCED BY THE PANELS ........................................................................................................................ 66 TABLE 32. BATTERY BANK SIZING ......................................................................................................................................... 67 TABLE 33. NUMBER OF DAYS OF AUTONOMY FOR BOTH OPTIONS ............................................................................................... 68 TABLE 34. THERMAL SYSTEM COST ANALYSIS ......................................................................................................................... 70 TABLE 35. PV SYSTEM COST ANALYSIS .................................................................................................................................. 71 TABLE 36. GROUND SOURCE HEAT PUMP COST ANALYSIS.......................................................................................................... 72 TABLE 37. TOTAL COST OF EACH OPTION ............................................................................................................................... 72
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1 Chapter One: Introduction
Solar energy is being used by humans since thousands years ago. Antique cultures used
it for starting fires to keep warm, and their buildings were designed so that the walls and
floors could collect solar heat during the day and release it at night.
The world we live in is constantly in a state of advancement. Technology is often changing
for the better.
Nowadays, the sun - the cleanest and most abundant renewable energy source, can be
converted into thermal or electrical energy so as to provide a comfortable interior
environment and heating water for domestic or other uses.
Theoretically, the sun can allow house energy independence depending on the home’s
consumption. Consumption which must be minimized by human lifestyle changes. If the
house is to be built, super-insulating material and efficient appliances must be chosen,
and passive solar heating must be envisaged.
According to Webster’s dictionary, the word “independent” means to be self-governing,
showing self-reliance, while “energy” is defined as the capacity to perform work.
Aiming at providing a house with full energy independence all over the year is a challenge.
Even more if this is of typical construction, not energy-optimized since the first step of its
design.
The aim of this study is to evaluate two options which are, each, a combination of energy
sources used for providing space and domestic water heating, and electricity. The
importance of identifying the most energy efficient system is imperative so as to determine
which one of the two options allows the longest period of time, during which four persons
can live in a fully energy-independent house.
The literature review focuses on building information from research in order to provide a
better understanding of the technologies the author will be working with. More specifically,
information detailing an overview of solar thermal and photovoltaic systems, and ground
source heat pump installations.
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The implementation focuses on the methodology used to undertake the calculations.
It details at first instance, the way the solar data were collected. Following, the
identification of the heat gains and losses according to the characteristics of the house
and finally, the feasibility studies and sizing of the different installations.
A CD-ROM associated with this report contains an excel file related to this work which
allowed the realisation of this project.
The next chapter is where the outcomes of the calculations will be presented. The
analysis of the findings will be detailed as well as the comparisons of data between, to
aid in the formulation of a conclusion.
The final chapter of this report covers a discussion on the findings in order to answer the
research question, ending by highlighting any limitations discovered during the whole
project and any areas of future work that can be expected.
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2 Chapter Two: Literature Review
2.1 Solar Thermal Energy
Solar water heating uses heat from the sun to provide hot water for space heating and/or
for personal hygiene and other domestic uses. The present study will be based solely on
the needs corresponding to personal uses.
The most solar energy available is in the sun’s rays from a clear sky however it is also
possible to collect heat on cloudy days. The use of this solar energy is required during
the heating season for space heating, yet it is not needed in the winter. Nevertheless, the
same quantity of water is needed throughout the full year. As there is less energy
availability during winter compared with summer, a very large collector would be needed
to supply all of the hot water requirements; making the collector greatly oversized in
summer. Consequently domestic water solar heating systems are then usually designed
to provide most, or all, of the hot water required in summer and only a part in winter.
This system is constituted of two parts: one is the solar collector that transfers energy to
the water flowing through it, and the other is a system which permits the transfer of this
heat to the water stored in the domestic tank. (Nicholls, 2008)
Types of solar collectors
Flat plate
The flat plate solar collector is composed of a black
coated surface under a glass cover, insulated to
the rear and sides. The transparent upper layer
allows the solar radiation to pass through to the
collector and reduces the heat losses by
convection. A heat transfer fluid, water or glycol
solution, circulates through the panel to transport
the energy collected away to where it will be used. Figure 1. Flat plate collector
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The container of these components is a frame made of steel or aluminium, holding the
components in place so that the structure can be mounted suitably south-facing.
(ViridianSolar, 2014)
Evacuated tube collectors
A dark-coloured absorber element is contained within an
evacuated glass tube, designed to concentrate radiation
to a central receiver; through which the solar fluid
circulates in a coaxial manner. A vacuum is also held in
the tube, providing an excellent thermal insulation to the
absorber.
One collector includes several glass tubes mounted in
rows into a manifold, the fluid passes by this last and
transports the heat away to the solar cylinder.
This type of collector is aesthetically difficult to integrate
and more suitable for industrial applications, so the flat plate collector which is cheaper,
is more adapted to this case study. (CIBSE Journal, 2016)
Figure 2. Evacuated tube collector
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System integration
Overview
When heat is to be collected from the panel, a solar controller activates the pump, which
pushes the heat transfer fluid over the circuit, this carries the heat produced in the
collector to the solar cylinder. The fluid is 40% propylene glycol with water ensuring freeze
protection down to -28 C and thermal stability at high temperature.
When the circulator switches off, the fluid flows back by gravity filling an expansion vessel.
This is a protection of the fluid from extreme temperature in winter and during stagnation
in summer. (EcoHiSolar, 2011)
Types of cylinder
The twin coil cylinder (Figure. 4 below) contains a solar heat exchange coil at the bottom
and another one above it, allowing both the boiler and the solar thermal system to heat
the water by convection. It is appropriate when an existing boiler is already installed in
the house.
Figure 3. Solar thermal system
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The solar electric cylinder (Figure. 5) comprises an indirect solar coil and an electric
immersion heater which can be powered by electricity generated by solar photovoltaic
panels. This cylinder is more suitable for the current project. (Gasappliance, 2013)
2.2 Solar Photovoltaic Energy
Solar photovoltaic panels are a clean way to produce electricity for use in buildings. The
power produced by a solar cell is directly proportional to the energy it receives. Although
solar array can be yielded and provide green electricity on dull days, more power will be
produced when there is more light coming from the sky.
Figure 6. Photovoltaic panel on-roof mounted
Figure 5. Twin coil cylinder Figure 4. Solar electric cylinder
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This is why it is important to minimise any obstructions which might overshadow the
panels; ensuring they are mounted in a space from which the sun is clearly visible will do
this. Ideally, the panels should face due south to ensure optimum light is received through-
out the year, however, this is dependent on application. In the case of roof-mounting, the
facing is entirely dependent on the position of the roof; nonetheless, an angle within 45
degrees of due south will provide satisfactory results in addition to a pitch comprised
between 20 and 50 degrees.
When sizing a system, energy consumption of the building and its occupants must be
assessed together with considerations on how to reduce consumption to minimum. (Hall
& Nicholls, 2008)
Photovoltaic cell operating
The simple structure of a photovoltaic cell is shown on the
figure. 7. The central element are crystals of silicon,
grouped together to form a panel of which the size ranges
from few watts to over 3 kW in terms of power.
Due to its atomic structure, an electric charge moves
naturally inside the crystal. Two types of silicon are joined
together; one is made by adding arsenic and acts as a
negative terminal and the other is made by adding boron
and acts as a positive terminal. In this manner the current
is influenced to flow in one direction. As the sunlight falls
on the p – n junction, more electrons are released increasing the electric current available
for collection. (Nicholls, 2008)
Types of cell
Two main types of PV cells are used for buildings; polycrystalline and monocrystalline.
Both types are made from silicon ingots, difference exists through a polycrystalline cell
consisting in multiple crystal structures whereas a monocrystalline cell contains a single
crystal. The purity of this monocrystalline cell is higher, inducing a better efficiency at a
bigger cost. (Renogy, 2015)
Figure 7. Photovoltaic cell
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Electricity generation system
PV panels mounted together form part of an entire electricity generation system
comprising charge controllers, inverters and batteries for off-grid systems which is the
case of this study.
MPPT
The electricity produced by a PV panel is dependent on the amount of energy hitting its
surface and its efficiency. The actual efficiency of a single crystal covers between 15%
and 18%, which may be further reduced by poor installation practice.
To overcome this and increase the global efficiency of the installation,
MPPT (maximum power point tracking) controllers are used. These
devices constantly check and sweep to find the maximum open
voltage of the PV array instead of having a fixed voltage dictated by
the battery. In this manner a higher voltage is permitted in the
installation, improving performance. (Dankoff, 2001)
Figure 8. Generation system scheme
Figure 9. MPPT BlueSolar
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Inverter
Solar panels produce direct current (DC) electricity at low voltage; DC is the type of
electricity that projects from the battery for the case of off-grid installations. By contrast,
the main electricity supplies are alternative current (AC), requiring an extra step between
PVs and the electricity wiring, covered by an inverter.
This device uses solid state electronics to turn low voltage DC into
high voltage AC at an appropriate frequency for the electricity
supply, 50 hertz in France. Care must be taken when sizing the
inverter according to the installation as it presents minimum and
maximum values of intensity and voltage input, and a maximum
intensity output.
Although the voltage increases, there is no concurrent production of electricity. As a result
of the increase in voltage, the available current decreases, so while the PV array produces
high current DC, the output of the inverter is at a lower current AC. (Dankoff, 2001)
Batteries
For off-grid systems, a battery solution for storage is
necessary when the electricity is not required at the time of
generation. Lead-acid batteries are now the most pragmatic
way of storing, still a storage of power as hydrogen gas is
currently developing and should become interesting in the
next couple of decades.
Deep-cycle lead-acid batteries
This type of battery is used for off-grid solar and wind power systems. They are designed
by the manufacturers to be able to charge with a small amount of current, taking
advantage of any available energy and having a good efficiency from 90 to 95%.
A starter battery can finish between 50 and 150 deep discharges whereas a deep-cycle
battery is able to complete around 1200 deep discharges cycles. As the worldwide price
Figure 11. Solar battery RBS-1860
Figure 10. Inverter MultiPlus
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of lead is high, the deep-cycle batteries are significantly more expensive than the others
due to the fact that they use more lead in their manufacture.
The amount of energy a battery can store is expressed in Amp hours (Ah), and this
capacity varies according to the period the battery will be discharged over. For most deep-
cycle batteries, the manufacturers provide a capacity rate over 20 or 100 hours meaning
that, for a battery rated at “200 Ah @ C20”, it is able to provide 200 Ah over 20 hours (at
constant 10 amps load). (CarbonNeutral, 2013)
For off-grid systems, the battery bank is sized relatively to the daily loads of the house. In
order to optimise the lifetime, a percentage of depth of discharge (DoD) rarely below 50%
is considered. This ratio gives several reserve days to the system, enough to prepare for
overcast days, in addition to the days of autonomy, which sizing also considers.
Deep-cycle batteries are manufactured in 2 volt cells. To provide the correct voltage
required by the installation they are assembled together in series. Similarly, if needed, the
capacity can be increased by joining parallel strings of batteries together (i.e. 2 parallel
strings of 6 x 2V, 1000 Ah batteries in series = 24V, 2000 Ah battery bank).
(CarbonNeutral, 2013)
2.3 Solar data
Solar energy or daylight utilisation at any location is dependent on the quantity of the
available flux which endures monthly and diurnal variations. Many locations in the world
have reliable and long-term measurements of the energy received from the sun, on
horizontal and sloped surfaces.
When undertaking solar thermal and photovoltaic studies, solar data must be collected in
order to find out the final power available for utilisation and to calculate the passive gains
in the building.
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Composition of solar radiation
The solar radiation filling the sky can be direct, diffuse or reflected.
The direct radiation defines the energy traveling on a straight line from the sun to the
surface of the earth.
The diffuse radiation is the sunlight which has been scattered by molecules and particles
present in the atmosphere.
The reflected radiation is sunlight that has been reflected by everything non-atmospheric,
such as the ground. (Watson, 2011)
Direct and Diffuse Irradiations
When the sun is high in a clear sky, direct radiation represents the large majority of the
global irradiation. As the sun descends, the amount of diffuse radiation increases to a
maximum of 40% of total radiation. Moreover, atmospheric conditions such as clouds and
pollution are factors increasing the amount of diffuse light. (T Muneer & Kambedezis,
2007)
Figure 12. Components of the solar radiation
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Global Irradiation
The global irradiation is the sum of direct, diffuse and ground reflected components of
sunlight; these can be collected from the NASA website for the wanted location. Precisely,
it is the monthly-averaged daily horizontal global irradiation G on a horizontal surface,
expressed in kWh/m²/day. This value can be disaggregated to produce hourly set,
allowing accurate solar collecting data according to the time of the day.
The energy hitting the surface of an object varies according to the time, location, its aspect
and tilt. The spreadsheets “calc4-09” and “4-10” available on the CD-ROM consider these
conditions and permit the decomposition of the solar radiation into its different
components. (Watson, 2011)
Different Study Considerations
When solar radiation passes through a window, each component is influenced in a
different manner; that is why the decomposition is useful and the procedure of calculating
solar gains in the building will be explained later.
When it comes to find out the power received by a solar panel, it is sufficient to consider
the slope global computed in the “calc4-10”, which is the final power received. (Muneer,
2000)
2.4 Ground Source Heat pump
Operation
Heat pumps use the refrigeration cycle to transfer heat from a source, to an internal space
through a heat distribution circuit. For the current study, the source of heat will be the
ground.
An antifreeze liquid is pumped through underground pipes, called ground loops, being
colder than the ground, the liquid absorbs energy which raises the temperature a few
degrees.
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At a given point of the circuit, the liquid passes through a heat exchanger; an evaporator
(see figure. 13). The heat is transferred from the liquid to a refrigerant circulating in
another circuit and causes its evaporation.
The vapour is now at low temperature and pressure and moves to a compressor to reach
high pressure as a result of the work completed by the compressor.
Then, the refrigerant gas enters a condenser where it releases heat, usually to a hot water
tank which then feeds heating and hot water systems.
Following, the refrigerant which is still in the form of a gas reduced in temperature and
pressure, moves to an expansion valve. This element lowers the pressure and
temperature again before the cycle starts again and repeats keeping the evaporator coil
constantly cold and the condenser coil constantly warm. (Hall & Nicholls, 2008)
These three components; compressor, condenser and evaporator are all contained in a
unit called heat pump.
Figure 13. Ground source heat pump and its refrigerant cycle
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Types of collector
The most common way to collect the heat from the ground is by using closed loop and
indirect circulation. A circulating pump circulates a mixture of water and antifreeze through
a closed loop of pipe.
After, the mixture passes through the heat pump where the heat absorbed in the ground
is extracted.
Alternatively, heat can be collected using “direct circulation”. In this case the heat pump
refrigerant is directly circulated through a copper pipe in the ground. This method doesn’t
require any circulating pump, however, a large volume of refrigerant is needed. For
ecological reasons, this type of collector is not of the most common, the refrigerant is
exposed to cause environmental damages due to its location in the circuit.
(QuelleEnergie, 2016)
Burial
The ground pipe is buried either horizontally in a shallow trench at depth comprised in
between 1 and 2 m, or vertically in a borehole, this is dependent on the area available for
the workings and the ground conditions.
Horizontal collectors require large areas and a soil depth of about 1.5 m. They are
particularly suitable for in rural locations where the properties are larger. (EnergyAgency,
2015)
In urban areas, the installation size can be limited and that is why it is wise to use vertical
collectors which can be buried up to 30m depth. Vertical collectors have an increased
price than horizontal collectors due to the amplified costs of trenching and drilling to a
deeper depth. However, vertical collectors have a better thermal efficiency as the ground
is warmer at escalated depth; and as a result, require less length of pipe.
(EnergySavingTrust, 2016)
23
Sizing
The length of the pipe required and the size of the pump depend on the building loads, it
is important that they are designed together. The ground loop must be sized to meet the
peak thermal power load. The thermal power load that a loop can extract is expressed in
W/m and is dependent on the temperature difference the fluid and the ground
temperatures.
The more pipe used, the greater the amount of energy collected but the more expensive
is the installation. Oversizing is uneconomical. (HeatPumpAssociation, 2015)
24
3 Chapter Three: Implementation
3.1 House Characteristics And Dimensions
The dimensions were assumed for the internal walls to be 4.5 x 6.5 x 2.7 m, for each
window 0.8 x 1 m and the door 0.88 x 1.86 m.
The door is wood made of spruce with a 6 cm thickness; the windows are argon-filled
double glazed, each pane of glass is 4 cm thick.
EAST
Figure 14. Wooden house scheme
25
The walls are composed by an internal wood cladding in pine, a wood wool insulation, a
thin weather grille and an external cladding made in spruce. The thicknesses are
indicated in cm on both figures below. The total thickness is 25.5 cm.
The roof makes a 30° angle with the horizontal. It is covered by a steel sheet from the
outside and the insulation is slightly thicker. Its total thickness is 31.5 cm, the composition
is shown below (figure. 15). The thermal conductivity of each material is also given on
figure 16.
From the house dimensions, the volume and areas have been calculated.
The length (a), and (b) shown in the house scheme were obtained using basic
trigonometric equations:
a =5.1/2
Cos (30°) 𝑎𝑛𝑑 𝑏 = 𝑎 ∗ sin (30°)
The internal volume of the house is:
In In Out Out
Pine Spruce Weather grille Steel Wood wool Glass
k (W/m.K) 0.13 0.14 0.09 50 0.038 1
Figure 15. Wall material composition (to scale 1/10)
Figure 16. Roof material composition (to scale 1/10)
Figure 17. Thermal conductivities of the materials (Wikipedia, 2016)
26
𝑉ℎ𝑜𝑢𝑠𝑒 = 4.5 ∗ 2.7 ∗ 6.5 + (2.25 ∗ 1.45) = 82.23 𝑚3
Assuming that the roof is 30 cm protruding on each side, the south-facing roof area is:
𝐴𝑟𝑜𝑜𝑓 𝑆 = (2.89 + 0.3) ∗ (7.01 + 2 ∗ 0.3) = 24.05 𝑚2
The internal area of the west-facing wall is:
𝐴𝑤𝑎𝑙𝑙 𝑊 = 4.5 ∗ 2.7 + (1.47 − 2.25) = 15.46 𝑚2
Internal area of the east-facing wall:
𝐴𝑤𝑎𝑙𝑙 𝐸 = 𝐴𝑤𝑎𝑙𝑙 𝑊 − (0.8 ∗ 1) = 14.54 𝑚2
Internal area of the north-facing wall:
𝐴𝑤𝑎𝑙𝑙 𝑁 = 6.5 ∗ 2.7 = 17.55 𝑚2
Internal area of the south-facing wall:
𝐴𝑤𝑎𝑙𝑙 𝑆 = 𝐴𝑤𝑎𝑙𝑙 𝑁 − (2 ∗ (0.8 ∗ 1) + (1.86 ∗ 0.88) = 14.07 𝑚2
These areas and volume will serve later in the calculations of heat losses for example.
27
3.2 Solar Collecting Data
A CD-ROM associated with the book “Windows in Building” (Muneer, 2000) contains
three excel spreadsheets which allowed, as a first step, the collection of the solar data.
Hourly values of global and diffuse irradiations
The first step was to obtain the daily-averaged solar radiation G from the NASA website
(NASA, 2016) searching by the location of Villard- de-Lans, for each month of the year.
By entering this value on the excel spreadsheet “calc4-09” (table 1), the number of the
month studied and the latitude of the location, the disaggregation of this global radiation
into hourly values from 5:30 to 11:30 am was obtained for each month.
Table 1. Spreadsheet "calc4-09" screenshot
Figure 18. NASA website screenshot
Calc4-09 Decomposition of averaged-daily irradiation into hourly values
Month Latitude G Hour Hourly values, W/m2
kWh/m2
IG
1 45.078 1.36 11.5 195
10.5 176
9.5 142
8.5 98
7.5 52
6.5 11
5.5 0
Daily totals 1350
28
For the rest of the day (from 12:30 to 6:30 pm), a symmetric image of these values is
considered.
Knowing the global solar radiation emitted at each hour allows an accurate solar daily
study to be done afterward.
The diffuse irradiation 𝐼𝐷 for every hour is calculated using the three following equations
(Muneer et al, 2014):
𝑘𝑇̅̅ ̅ =𝐼𝐺
𝐼𝐸
�̅� = 𝐼𝐷𝐼𝐺
�̅� = 0.89𝑘𝑇̅̅ ̅2− 1.185𝑘𝑇̅̅ ̅ + 0.95
Hence, 𝐼𝐷 = �̅̅� ∗ 𝐼𝐺
Where 𝑘𝑇̅̅ ̅ and �̅� are the monthly-averaged clearness index and diffuse ratio given in the
article. 𝐼𝐺 and 𝐼𝐷 are the global and diffuse radiations on a horizontal surface expressed
in W/m². 𝐼𝐸 is defined as the extra-terrestrial radiation received under the absence of any
atmosphere (W/m²) (T Muneer & Kambedezis, 2007).
When calculating the production of a solar thermal or PV panel, the data required as the
“power received” in the calculations is called slope global (W/m²). It is a function of the
direct, diffuse and reflected radiations.
When calculating the solar gains through a window, each of the three components: direct
diffuse and reflected are influenced differently from the others, a coefficient will be then
applied to each of them.
29
Hence, a complete solar data base is needed including the direct radiation (named as
slope beam in this study), sky diffuse, ground reflection and slope global for each hour of
the day and for each month. These are components of the global irradiation expressed in
W/m² and are obtained from the excel spreadsheet “calc4-10” (table 2). The solar angle
incidence will also be necessary to relieve (shown below as “solar inc”).
When using this excel file, the following primary information have to be entered:
Villard-de-Lans latitude/longitude: 45.078 N / 5.5514 E
Year: 2015
Month number: according to the month during which the solar data are collected.
Calc4-10 Slope irradiance
SURFACE
LAT 45.1 North=+ve Aspect 180
LONG 5.55 West=+ve Tilt 90
LSM 0 West=+ve Rho 0.2
Year 2015
Month 1
Day Hour IG ID EOT DEC Cor. Solar Solar Solar IDN ERAD Slope Sky Ground Slope
W/m2 W/m2 term alt. azim. inc. - W/m2 beam diffuse reflect. global
16 1 0 0 -0.16 -21.0 0.53 -65.2 16.9 113.7 16 0 0 0 0 0
16 2 0 0 -0.16 -21.0 0.53 -59.7 45.0 110.9 16 0 0 0 0 0
16 3 0 0 -0.16 -21.0 0.53 -51.0 64.5 105.7 16 0 0 0 0 0
16 4 0 0 -0.16 -21.0 0.53 -40.9 78.6 98.6 16 0 0 0 0 0
16 5 0 0 -0.16 -21.0 0.53 -30.4 90.0 90.0 16 0 0 0 0 0
16 6 0.0 0.0 -0.16 -21.0 0.53 -19.9 100.2 80.4 16 0 0 0 0 0
16 7 11.4 0.0 -0.16 -21.0 0.53 -9.6 110.1 70.2 16 0 0 0 1 1
16 8 52.3 33.0 -0.16 -21.0 0.53 2.2 123.1 56.9 16 55 0 20 5 26
16 9 98.0 57.8 -0.16 -21.0 0.53 8.5 131.5 49.1 16 209 178 73 10 260
16 10 141.8 89.6 -0.16 -21.0 0.53 15.7 143.8 39.0 16 381 150 74 14 238
16 11 176.2 113.5 -0.16 -20.9 0.53 20.9 157.5 30.3 16 502 152 84 18 254
16 12 195.2 126.3 -0.16 -20.9 0.53 23.6 172.4 24.8 16 565 156 90 20 266
16 13 195.2 126.3 -0.16 -20.9 0.53 23.6 187.6 24.8 16 565 156 90 20 266
16 14 176.2 113.5 -0.16 -20.9 0.53 20.9 202.5 30.3 16 503 152 84 18 253
16 15 141.8 89.7 -0.16 -20.9 0.53 15.7 216.2 39.0 16 382 150 74 14 238
16 16 98.0 57.9 -0.16 -20.9 0.53 8.6 228.5 49.1 16 210 176 72 10 258
16 17 52.3 32.6 -0.16 -20.9 0.53 2.2 237.0 57.0 16 55 0 20 5 26
16 18 11.4 0.0 -0.16 -20.9 0.53 -9.6 249.9 70.2 16 0 0 0 1 1
16 19 0.0 0.0 -0.16 -20.9 0.53 -19.8 259.9 80.5 16 0 0 0 0 0
16 20 0 0 -0.16 -20.9 0.53 -30.3 270.1 90.1 16 0 0 0 0 0
16 21 0 0 -0.16 -20.9 0.53 -40.8 281.5 98.7 16 0 0 0 0 0
16 22 0 0 -0.16 -20.9 0.53 -50.9 295.7 105.9 16 0 0 0 0 0
16 23 0 0 -0.16 -20.9 0.53 -59.5 315.2 111.1 16 0 0 0 0 0
16 24 0 0 -0.16 -20.8 0.53 -65.0 343.2 113.9 16 0 0 0 0 0
Table 2. Spreadsheet calc4-10 screenshot
30
Surface:
Aspect: the angle in degree according to the orientation of the window or panel.
Tilt: the angle in degree of the surface with horizontal.
For example, for collecting solar radiations data on a south-oriented vertical window: the
aspect is 180° and the tilt, 90°.
Rho: 0.2 is an assumed value of the coefficient of reflectivity of the surrounding. (Muneer,
2000)
Day: 16, taken in the middle of the month for the study to be the most representative
possible.
The hourly values of 𝐼𝐺 and 𝐼𝐷 obtained previously can then be entered in the columns
designed for that purpose (filled in green on previous table), and all the solar radiation
components and angles data can be collected.
3.3 Analysis of the Needs
Passive gains
Solar gains through windows
Two windows of 0.8 m² area each are facing south and another of 0.8 m² is facing east.
Accordingly, two sets of solar components have been collected respectively for a 180°
and 90° aspect and both for a 90° tilt (vertical surfaces). The tables of solar data collected
for the south-facing windows are presented below as examples.
Table 3. Slope beam (W/m²): Aspect=180° - Tilt=90°
Hours January February March April May June July August September October November December
5.5 0 0 0 0 0 0 0 0 0 0 0 0
6.5 0 0 0 0 0 0 0 0 11 0 0 0
7.5 0 0 55 27 5 0 0 25 53 58 0 0
8.5 179 111 106 68 43 32 45 73 103 100 106 0
9.5 151 160 156 108 81 69 87 119 152 143 143 147
10.5 152 199 197 140 110 98 120 155 191 179 176 178
11.5 156 221 220 157 127 114 138 175 212 199 194 196
12.5 156 221 220 157 126 114 138 175 212 199 194 196
13.5 152 199 197 139 110 98 120 156 191 179 176 178
14.5 150 159 156 107 80 69 87 120 152 144 144 147
15.5 177 110 105 67 43 32 45 74 103 101 107 0
16.5 0 0 54 27 5 0 0 26 54 60 0 0
17.5 0 0 0 0 0 0 0 0 0 0 0 0
18.5 0 0 0 0 0 0 0 0 0 0 0 0
31
The hourly power admitted through a vertical window is given by:
𝐼𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑤𝑖𝑛𝑑𝑜𝑤 = ((𝐼𝑏𝑒𝑎𝑚 ∗ 𝑇(𝜃)) + (𝐼𝑠𝑘𝑦 𝑑𝑖𝑓𝑓 ∗ 𝜏𝑠𝑘𝑦 𝑑𝑖𝑓𝑓) + (𝐼𝑔𝑟𝑜𝑢𝑛𝑑 𝑟𝑒𝑓 ∗ 𝜏𝑔𝑟𝑜𝑢𝑛𝑑 𝑟𝑒𝑓)) ∗ 𝑔𝑙𝑎𝑧𝑒𝑑 𝑎𝑟𝑒𝑎 (W)
With 𝑇(𝜃) = 1.018 ∗ 𝑇0 ∗ (cos 𝜃 + sin3𝜃 ∗ cos 𝜃)
Where 𝐼𝑏𝑒𝑎𝑚, 𝐼𝑠𝑘𝑦 𝑑𝑖𝑓𝑓 and 𝐼𝑔𝑟𝑜𝑢𝑛𝑑 𝑟𝑒𝑓 are the slope beam, the sky diffuse and the ground
reflected radiations in W/m². 𝑇𝜃 is the transmission of a pane of glass at a given solar
angle of incidence 𝜃 in radians (= degrees * π
180).
𝑇0 is the glass transmission coefficient at normal incidence and is taken as 0.54
considering that the glazing’s are double coated. The coefficient is given in the book
“Windows in Building” (Tariq Muneer, 2000, p. 115) in the column solar radiant heat direct.
𝜏𝑔𝑟𝑜𝑢𝑛𝑑 𝑟𝑒𝑓 and 𝜏𝑠𝑘𝑦 𝑑𝑖𝑓𝑓 are the glass transmission coefficients of the ground reflected and
sky diffuse radiations, both equal to 𝑇(𝜃) at a 60° solar angle incidence.
A table listing the values of 𝑇(𝜃) for each aspect was added to the database before the
calculation, as the example below shows:
Table 4. Sky diffuse/Ground reflection (W/m²): Aspect=180° - Tilt=90°
Hours Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref. Sky diff. Grd ref.
5.5 3 1 14 6 23 10 21 10 14 4
6.5 1 10 3 23 10 36 16 45 21 44 21 32 15 19 6
7.5 20 5 18 5 48 13 61 20 71 27 69 33 70 34 71 27 57 17 33 7 6 2
8.5 72 10 64 14 89 24 97 32 106 39 111 44 116 47 111 40 97 29 67 16 47 9 20 6
9.5 74 14 99 23 128 35 131 42 138 50 143 55 151 58 149 52 135 40 100 25 76 16 67 12
10.5 84 18 127 30 158 44 157 50 163 58 167 63 179 67 178 61 165 49 125 32 99 21 89 17
11.5 90 20 143 34 175 49 171 55 176 62 180 67 193 72 193 65 181 53 140 36 112 25 101 20
12.5 90 20 143 34 175 49 171 55 176 62 180 67 193 72 193 65 181 53 140 36 112 25 101 20
13.5 84 18 127 30 158 44 157 50 163 58 167 63 179 67 178 61 165 49 126 32 99 21 89 17
14.5 74 14 99 23 127 35 131 42 138 50 143 55 151 58 149 52 135 40 100 25 76 16 67 12
15.5 72 10 64 14 89 24 97 32 106 39 111 44 116 47 111 40 97 29 67 16 48 9 20 6
16.5 20 5 18 5 48 13 61 20 71 27 69 33 70 34 71 27 57 17 33 7 6 2
17.5 1 10 3 23 10 36 16 45 21 44 21 32 15 19 6
18.5 3 1 14 6 23 10 21 10 14 4
OctoberJanuary February March April November DecemberMay June July August September
Hours January February March April May June July August September October November December
5.5 0.18 0.07 -0.08 -0.20 -0.33 -0.36 -0.34 -0.26 -0.05 0.02 0.15 0.21
6.5 0.34 0.32 0.13 -0.04 -0.16 -0.21 -0.18 -0.08 0.07 0.27 0.32 0.36
7.5 0.48 0.40 0.30 0.15 0.03 -0.03 0.00 0.11 0.25 0.37 0.46 0.49
8.5 0.52 0.49 0.42 0.31 0.19 0.13 0.16 0.27 0.39 0.47 0.51 0.52
9.5 0.53 0.53 0.49 0.41 0.31 0.25 0.28 0.37 0.47 0.52 0.53 0.53
10.5 0.54 0.53 0.52 0.46 0.38 0.33 0.35 0.44 0.51 0.53 0.54 0.54
11.5 0.54 0.54 0.53 0.48 0.41 0.36 0.39 0.46 0.52 0.53 0.54 0.54
12.5 0.54 0.54 0.53 0.48 0.41 0.36 0.39 0.46 0.52 0.53 0.54 0.54
13.5 0.54 0.53 0.52 0.46 0.38 0.33 0.35 0.44 0.51 0.53 0.54 0.54
14.5 0.53 0.52 0.49 0.41 0.31 0.25 0.28 0.38 0.47 0.52 0.53 0.53
15.5 0.52 0.49 0.42 0.30 0.19 0.13 0.16 0.27 0.39 0.47 0.51 0.52
16.5 0.48 0.40 0.30 0.15 0.02 -0.03 0.00 0.11 0.26 0.37 0.46 0.49
17.5 0.34 0.32 0.13 -0.04 -0.16 -0.21 -0.18 -0.08 0.07 0.27 0.32 0.36
18.5 0.18 0.07 -0.08 -0.21 -0.33 -0.36 -0.34 -0.26 -0.05 0.02 0.15 0.21
Table 5. Values of T (θ) - Aspect=180° - Tilt=90°
32
As well as another listing of the glazed areas and transmission coefficients:
The power admitted can now be calculated using the previous formula for each hour of
the day of each month. Daily summing these hourly powers gives an energy gains in
Wh/day which can be converted in kWh/day, most explicit.
Sensible heat emission of humans
Due to their metabolic activity, the human bodies lose heat to the surrounding contributing
to the passive gains in the house.
Assuming that four people occupy the house during 12 hours a day, with a small degree
of activity which could be qualified as “seated, very light work”, their heat emission would
be equal to 70 W each. (ASHRAE, 2001)
The total energy gained in the house per day is calculated by:
𝐸 = 𝑂𝑐𝑐𝑢𝑝𝑎𝑛𝑡𝑠 𝑛𝑢𝑚𝑏𝑒𝑟 ∗ 𝑜𝑐𝑐𝑢𝑝𝑎𝑛𝑐𝑦 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (ℎ) ∗ ℎ𝑒𝑎𝑡 𝑒𝑚𝑖𝑠𝑠𝑖𝑜𝑛 (𝑊) (𝑊ℎ
𝑑𝑎𝑦)
Heat losses analysis
General methodology
The overall thermal losses studies have been done
separately on the roof, windows, door and each wall
using the same procedure each time even though,
depending on the element, few steps can be added or
removed.
The inside temperature is considered to be maintained
18°C all over the year insuring a thermal comfort for the
occupants.
Table 6. Glass areas and transmission coefficients of radiation
Figure 19. Heat transfer phenomena through the wall
Area (m² ) Ϯs. diff Ϯground ref
Window sclear coated (South) 1.6
Window clear coated (East) 0.80.45 0.45
33
For each component, the heat transfer occurs via an internal convection, several
conductions through the element and an external convection releasing heat to the
environment (figure 19).
Taking the wall as an example, the approach consists in first
assuming an internal surface temperature 𝑇𝑖𝑖 (visible on
figure 20); this allows, after few calculations related to fluid
mechanics and which will be detailed later, to find out an
approximation of how much heat is transferred by the first
convection.
Considering a steady state, meaning that the energy
transferred by each heat flux is equal, it is admitted: 𝑞𝑐𝑜𝑛𝑣 1 =
𝑞𝑐𝑜𝑛𝑑1 = 𝑞𝑐𝑜𝑛𝑑2 = 𝑞𝑐𝑜𝑛𝑑3 = 𝑞𝑐𝑜𝑛𝑑4 = 𝑞𝑐𝑜𝑛𝑣 2
In this manner, a value of 𝑇𝑤𝑖 can be found by isolation using
the conduction heat transfer relation: 𝑞 =𝑘
𝑒∗ (𝑇𝑖𝑖 − 𝑇𝑤𝑖)
Where k and e are the thermal conductivity and the
thickness of the material known from previously.
All other intermediate temperatures at each contact point between materials 𝑇𝑤𝑖𝑖, 𝑇𝑤0′ and
𝑇𝑤0 are found the same way.
Now again, another series of calculations is done to obtain the external convection heat
transfer between 𝑇𝑤𝑜 and 𝑇𝑜𝑢𝑡.
So each heat loss by convection has been calculated regarding different temperatures,
the first one: 𝑇𝑖𝑛 and 𝑇𝑖𝑖 ; the second one 𝑇𝑤𝑜 and 𝑇𝑜𝑢𝑡. In theory and since the system
was assumed to be in a steady state, they should be equal but it is not the case as 𝑇𝑖𝑖 is
only an approximation. That is where the “goal seek function” available in “Excel” takes
place, looking at a 0 value for the relation 𝑄𝑐𝑜𝑛𝑣 1 − 𝑄𝑐𝑜𝑛𝑣 2 by changing the internal
surface temperature of the element which then becomes the exact value.
Figure 20. Temperature profile through the wall
34
The complete procedure is detailed below:
𝑇𝑖𝑖 is assumed, slightly lower than the inside temperature
The film temperature is calculated by 𝑇𝑓 =(𝑇𝑖,𝑖+𝑇𝑖𝑛𝑠𝑖𝑑𝑒)
2 (𝐾) allowing to find the air
properties: ρ, 𝐶𝑝, µ, ν, α and 𝑃𝑟 (defined below) at this same temperature.
Then the first set of calculations which will permit to find the coefficient of
convection is as follow:
𝛽 =1
𝑇𝑓 (𝐾−1)
Rayleigh number:
𝑅𝑎𝐿 =𝑔𝛽(𝑇𝑠𝑢𝑟𝑓𝑎𝑐𝑒,𝑖 − 𝑇𝑖𝑛𝑠𝑖𝑑𝑒)𝐿
3
𝜈𝛼
where ν is the kinematic viscosity in m²/s
α is the thermal diffusivity in m²/s
g is the gravitational acceleration in m/s²
β is the volumetric thermal expansion coefficient in K-1
L is the height of the surface studied
Nusselt number: 𝑁𝑢𝐿 =
(
0.8250 +0.387 𝑅𝑎𝐿
16
[1+(0.492/𝑃𝑟)916]
827
)
2
The coefficient of convection ℎ𝑖 can now be calculated, using ℎ𝑖 = 𝑁𝑢𝐿𝑘
𝐿 (W/m².K)
And the final value of the first convection heat transfer per 𝑚2: 𝑞𝑐𝑜𝑛𝑣1 =
ℎ𝑖 (𝑇𝑖𝑛𝑠𝑖𝑑𝑒 − 𝑇𝑖𝑖) (W/𝑚2)
In a steady state, 𝑞𝑐𝑜𝑛𝑣1 is equal to 𝑞𝑐𝑜𝑛𝑑1, so as to find 𝑇𝑤𝑖:
𝑞𝑐𝑜𝑛𝑑1 = 𝑞𝑐𝑜𝑛𝑣1 (W
𝑚2) =
𝑘
𝑒∗ (𝑇𝑖𝑖 − 𝑇𝑤𝑖) <=> 𝑇𝑤𝑖 = 𝑇𝑖𝑖 −
𝑒 ∗ 𝑞𝑐𝑜𝑛𝑣1
𝑘(𝐾)
Where k is the thermal conductivity in W/m.K and e the material thickness
in m.
And so on for the calculations of 𝑇𝑤𝑖𝑖, 𝑇𝑤0′ and 𝑇𝑤0 using the same relation.
At this stage, the focus is on the last convection.
A new film temperature (new air properties) is calculated considering, this time,
𝑇𝑤𝑜 and 𝑇𝑜𝑢𝑡. The following calculations are the same as above: 𝛽, 𝑅𝑎𝐿, 𝑁𝑢𝐿,
35
according to the new 𝑇𝑓 are determined and permit to obtain the external
convection coefficient ℎ0, and then 𝑞𝑐𝑜𝑛𝑣2.
All transfers were determined, the aim is now to define the right internal surface
temperature of the wall. As 𝑇𝑖𝑖 is an assumption at the beginning and serves to
calculate everything else: both 𝑞𝑐𝑜𝑛𝑣 found are not equal.
The “goal seek” function is used finding the correct 𝑇𝑖𝑖 for Δ q = 𝑞𝑐𝑜𝑛𝑣1 − 𝑞𝑐𝑜𝑛𝑣2 =
0. The heat losses can be calculated.
To find out the quantity of heat lost through the wall, the thermal transmittance U
is needed:
𝑈 =1
𝑅𝑐𝑜𝑛𝑣 1+𝑅𝑐𝑜𝑛𝑑1,2,3,4+𝑅𝑐𝑜𝑛𝑣 2 (W/𝒎𝟐.K)
With 𝑅𝑐𝑜𝑛𝑣 =1
ℎ and 𝑅𝑐𝑜𝑛𝑑 =
𝑒
𝑘 (𝒎𝟐.K/W)
The thermal losses are finally found using 𝑄 = 𝑈𝐴(𝑇𝑖𝑛 − 𝑇𝑜𝑢𝑡) (W)
Where A is the wall area in 𝑚2
And so on for the other walls of which only the area differs.
The outside temperature 𝑇𝑜 is always taken as the average temperature of the month
corresponding (figure 21) obtained from the NASA website (NASA, 2016).
The methodology is the same for every element. Some can have more or less conduction
heat transfers through themselves: the door induces only one of them (figure 22).
36
Difference in the approach for the roof
The roof can be compared to a sloping wall making an angle θ with the vertical as shown
in the figure 20. It induces the inclusion of cos(θ) in the calculation of the Rayleigh number
for both convections.
Hence, the equation becomes:
𝑅𝑎𝐿 =𝑔𝛽 cos(θ) (𝑇𝑠𝑢𝑟𝑓𝑎𝑐𝑒,𝑖 − 𝑇𝑖𝑛𝑠𝑖𝑑𝑒)𝐿
3
𝜈𝛼
Difference in the approach for the windows
Changes occur the most in the procedure when calculating the heat transfer through the
windows.
As it can be seen on the figure 24, there are three transfers by convection combined with
radiation, and conductions. According to “CIBSE guide C” (CIBSE, 2007), this implies the
use of some more radiation formulas.
Figure 22. Heat transfer through the door
Θ = 60°
Figure 23. Roof 𝜃 angle sketch
Taverage (°C)
January -0.8
February 0.3
March 3.7
April 6.7
May 11.8
June 15.6
July 18.2
August 17.9
September 13.5
October 9.2
November 3.3
December 0.3
Figure 21. Monthly average temperatures
37
During the calculation of the first convection heat transfer, an
internal radiation heat transfer coefficient ℎ𝑟𝑖 (W/𝒎𝟐.K) must be
added to ℎ𝑖 which becomes:
ℎ𝑖 = 𝑁𝑢𝐿𝑘
𝐿+ ℎ𝑟𝑖 𝑤𝑖𝑡ℎ ℎ𝑟𝑖 = 5.3 ×
𝜀ℎ0.83
(W/𝒎𝟐. K)
Where 𝜀ℎ is the hemispherical emissivity of a coated surface
equal to 0.88.
The first conduction occurs the same way as previously.
Again, another internal radiation heat transfer coefficient is considered during the transfer
2 (shown on the figure 24), calculated differently this time:
ℎ𝑟2 =4 ∗ σ ∗ 𝑇𝑓
3
1𝜀ℎ + 1
+1
𝜀ℎ − 1
𝑎𝑛𝑑 ℎ2 =𝑁𝑢𝐿𝑘
𝐿+ ℎ𝑟2 (W/𝒎𝟐. K)
Where σ is the Stefan-Boltzmann constant equal to 5.67 x 10 -8 W/m2/K4.
The heat transferred by “Conv 2 + Rad 2” between the two panes of
glass has just been calculated. But here, the inside surface
temperature of the second pane of glass 𝑇𝑤𝑜 can’t be calculated as
the transfer did not occur by conduction (so the relation 𝑞 =𝑘
𝑒∗ (𝑇𝑤𝑖 −
𝑇𝑤𝑜) can’t be used as it was before).
Thus, a second assumption of temperature for 𝑇𝑤𝑜 is made so 𝑇𝑤𝑜𝑜
can be calculated.
For the external transfer, the heat transfer coefficient is given by:
ℎ2 =𝑁𝑢𝐿𝑘
𝐿+ 𝐸 × ℎ𝑟𝑜 𝑤𝑖𝑡ℎ ℎ𝑟𝑜 = 5.3 ×
𝜀ℎ0.83
(W/𝒎𝟐. K)
Where the emissivity factor 𝐸 is the product of the view factor equal to 0.81 and the
emissivity of the surface 𝜀ℎ.
Figure 24. Heat transfer through
a window
Figure 25. Temperature profile through a window
38
All heat transfers can be determined and after that, the goal seek function can look at the
exact values for 𝑇𝑖𝑖 and 𝑇𝑤𝑜 working on both Δ q = 𝑞𝑐𝑜𝑛𝑣+𝑟𝑎𝑑 1 − 𝑞𝑐𝑜𝑛𝑣+𝑟𝑎𝑑 2 and Δq =
𝑞𝑐𝑜𝑛𝑣+𝑟𝑎𝑑 2 − 𝑞𝑐𝑜𝑛𝑣+𝑟𝑎𝑑 3 , simultaneously.
The U-value (thermal transmittance) and thermal losses can finally be calculated as
explained in the general method.
The thermal losses through the frame are also considered and are determined with the
same manner as the door.
Ventilation
The house is naturally ventilated. The outside air infiltrates through small gaps and
contributes to the ventilation as well as the window openings do.
The whole house air volume is assumed to be renewed every 2 hours, inducing an air
change rate n = 0.5/h.
The thermophysical properties of the air can be worked out for the average temperature
between the outside and inside which depends on the month studied. Thus, the air density
ρ (kg/ m3) and specific heat capacity 𝐶𝑝 (kJ/kg.K) are determined and the heat lost is
found:
𝑄 = 𝑛 ∗ 𝑚 ̇ 𝐶𝑝 ∆𝑇 (𝑊) 𝑤𝑖𝑡ℎ 𝑚 ̇ =𝑉ℎ𝑜𝑢𝑠𝑒3600
∗ ρ
Where 𝑚 ̇ is the mass flow rate in kg/s and ∆𝑇 is the temperature difference between inside
(18˚C) and outside the house.
Thermal bridges and floor
In order to quantify the heat lost by the areas which are not as
well insulated as their surroundings - the thermal bridges (figure
26), they are assumed to be the cause of 5 % of the overall
heat losses (ADEME, 2016).
Similarly for the floor through which usually; as it can be seen
on the figure 27, between 7 and 10 % of the heat is lost. 9% is
considered in this study. Figure 26. Example of
thermal bridges at wall/floor junction
39
The following figure is taken from a French website and gives indicatives percentages of
heat lost for each element:
Hence, the losses through the thermal bridges and the floor are given by:
𝑄 = (% 𝑤𝑎𝑛𝑡𝑒𝑑
100 −% ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑡𝑊+𝐷+𝑊+𝑅+𝑉) ∗ (
100 −% ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑡𝑊+𝐷+𝑊+𝑅+𝑉% ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑡𝑊+𝐷+𝑊+𝑅+𝑉
) ∗ ℎ𝑒𝑎𝑡 𝑙𝑜𝑠𝑡𝑊+𝐷+𝑊+𝑅+𝑉
Summing all these losses through each element obtained so far, gives the global heat
power loss of the house.
The daily quantity of energy lost in Wh is obtained by multiplying this power by 24 hours
and by subtracting the passive gains from them.
Also, a simulation of the heat lost during the coldest day that the city of Villard-de-Lans
has ever known will be done. This happened the 3rd of January 1971, and the temperature
went down to -27.1 ˚C (Wikipedia, 2016). The data obtained from it are really important
for sizing the energetic installations afterward.
Figure 27. Heat losses of a traditional house (ADEME, 2016)
Thermal bridges
40
Hot water demand
The domestic hot water used for showers, hot water taps and others, is assumed to be
50 L per day and per person; and remains constant throughout the year.
Hence, the requirements for four persons are V = 200 L = 0.2 𝑚3 corresponding to a mass
𝑚 = 𝑉 ∗ 𝜌𝑤𝑎𝑡𝑒𝑟 with 𝜌𝑤𝑎𝑡𝑒𝑟 = 996 𝑘𝑔/𝑚3 , the water density.
Considering that this water has to be heated up from 15 to 65˚C (temperature of
deliveration), the energy required to meet the needs is calculated as follows:
𝑄𝑑𝑒𝑚𝑎𝑛𝑑 = 𝑚 𝐶𝑝𝑤𝑎𝑡𝑒𝑟 ∆𝑇 (𝐽) = 𝑚 𝐶𝑝𝑤𝑎𝑡𝑒𝑟∆𝑇
3600(𝑊ℎ)
Where 𝐶𝑝 is the water specific heat capacity equal to 4185 J/kg.K
The needs having been analysed, the procedure focuses now on the way they will be
met. In the first instance, the consideration is that the heat losses of the house found
earlier are compensated by an electric heating system. The feasibility of a solar thermal
system to meet the load in hot water is now studied (option 1).
41
3.4 Solar Thermal Study
As said previously in the part “solar collecting data”, the data required in the calculation
of the solar thermal panel production is the slope global (W/m²).
The hourly values of 𝐼𝐺 and 𝐼𝐷 for each month were listed as the table below shows:
From them, the hourly values of the slope global were found.
The study has been done in the case where the collectors would cover the south-facing
roof area.
Therefore, the slope global was found via the spreadsheet “calc4-10” for a 180˚ aspect
for each month
Moreover, the roof making a 30˚ angle with the horizontal, 30˚ tilt was entered.
As obvious, the other information enounced previously remain the same.
The values of slope global were listed this way:
HOURS January February March April May June July August September October November December
5.5 0 0 0 6.5 80.7 139.9 135.9 24.7 0.0 0 0 0
6.5 0.15285376 0 17.9 92.9 162.9 218.9 219.6 145.3 48.9 0 0 0
7.5 32.3 31.7 83.9 170.1 247.0 302.7 309.0 230.9 122.1 42.5 11.6 0
8.5 52.9 80.9 155.9 247.2 328.6 383.9 396.0 316.0 197.8 84.5 50.6 34.8
9.5 81.8 128.7 222.4 315.8 399.9 454.4 471.9 391.3 266.6 136.6 90.3 69.6
10.5 103.5 150.6 273.6 367.3 452.8 506.5 528.2 447.6 318.9 177.1 121.4 98.7
11.5 115.2 172.8 301.6 395.0 481.1 534.3 558.2 477.8 347.2 199.2 138.5 114.8
12.5 115.2 172.9 301.7 395.1 481.1 534.3 558.2 477.7 347.1 199.1 138.5 114.8
13.5 103.6 151.0 273.9 367.5 452.9 506.6 528.1 447.4 318.6 176.8 121.4 98.7
14.5 81.9 128.8 222.9 316.1 400.1 454.4 471.8 391.0 266.1 136.1 90.2 69.6
15.5 53.0 81.0 156.5 247.5 328.8 384.0 395.8 315.6 197.3 83.9 50.5 34.827813
16.5 32.0 31.9 84.6 170.4 247.2 302.8 308.8 230.5 121.5 42.3 11.6 0
17.5 0.2 0 18.0 93.1 162.9 218.9 219.5 145.1 37.1 0.0 0 0
18.5 0 0 0 6.5 80.4 139.8 136.2 24.7 0.0 0 0 0
HOURS Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2) Ig (W/m2) Id (W/m2)
5.5 0.0 0.0 0.0 0.0 0.0 8.1 6.8 59.5 39.8 103.2 63.9 96.6 58.7 40.3 25.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
6.5 11.4 0.0 0.0 0.0 26.1 18.8 97.6 63.6 159.8 100.7 209.3 126.3 211.0 124.9 147.3 89.3 60.9 39.0 0.0 0.0 0.0 0.0 0.0 0.0
7.5 52.3 33.0 50.2 33.2 128.6 81.0 204.5 127.7 274.0 166.7 326.7 193.0 338.9 196.3 271.3 159.9 170.0 104.1 70.5 46.6 16.6 12.2 0.0 0.0
8.5 98.0 57.8 140.5 88.6 243.7 147.1 317.4 192.3 390.7 232.0 444.5 258.2 467.9 266.8 399.8 230.6 288.8 171.3 159.9 101.6 85.1 55.5 55.9 36.2
9.5 141.8 89.6 230.7 140.9 354.0 207.9 421.5 250.0 496.2 289.6 549.5 315.3 583.3 329.3 516.9 294.1 400.4 232.5 247.6 152.7 155.6 98.9 119.5 76.3
10.5 176.2 113.5 303.5 181.6 440.8 254.8 501.7 293.7 576.3 332.8 628.4 358.0 670.4 376.3 606.3 342.2 487.4 279.4 317.6 192.1 213.4 133.0 172.6 108.1
11.5 195.2 126.3 344.1 203.9 488.6 280.4 545.3 317.2 619.5 356.0 670.8 380.8 717.3 401.6 654.7 368.2 535.0 304.9 356.4 213.6 245.8 151.7 202.6 125.7
12.5 195.2 126.3 344.1 203.9 488.6 280.4 545.3 317.2 619.5 356.0 670.8 380.8 717.3 401.6 654.7 368.2 535.0 304.8 356.4 213.6 245.8 151.7 202.6 125.7
13.5 176.2 113.5 303.5 181.6 440.8 254.8 501.7 293.7 576.3 332.8 628.4 358.0 670.4 376.3 606.3 342.1 487.4 279.3 317.6 192.1 213.4 132.9 172.6 108.1
14.5 141.8 89.7 230.7 141.0 354.0 208.0 421.5 250.1 496.2 289.6 549.5 315.3 583.3 329.3 516.9 294.0 400.4 232.4 247.6 152.6 155.6 98.8 119.5 76.3
15.5 98.0 57.9 140.5 88.8 243.7 147.2 317.4 192.4 390.7 232.0 444.5 258.2 467.9 266.8 399.8 230.6 288.8 171.1 159.9 101.4 85.1 55.4 55.9 36.2
16.5 52.3 32.6 50.2 33.3 128.6 81.2 204.5 127.9 274.0 166.8 326.7 193.0 338.9 196.3 271.3 159.7 170.0 103.9 70.5 46.4 16.6 12.2 0.0 0.0
17.5 11.4 0.0 0.0 0.0 26.1 18.9 97.6 63.8 159.8 100.8 209.3 126.4 211.0 124.9 147.3 89.1 60.9 38.8 0.0 0.0 0.0 0.0 0.0 0.0
18.5 0.0 0.0 0.0 0.0 0.0 0.0 8.1 6.8 59.5 39.9 103.2 63.9 96.6 58.6 40.3 25.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0
DecemberJanuary February March April May June July August September October November
Table 7. Global and diffuse radiations (W/m²) for each month of the year at Villard-de-Lans
Table 8. Slope global at Villard-de-Lans (W/m²) - Aspect=180° - Tilt=30°
42
Calculations of production
For each hour of the day in each month, the heat production per m²collector is found by:
𝑄𝑐𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟 = 𝑆𝑙𝑜𝑝𝑒 𝑔𝑙𝑜𝑏𝑎𝑙 ∗ % 𝑐𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟 𝑒𝑓𝑓𝑖𝑒𝑛𝑐𝑦 ( W/m²)
This power corresponds to the heat that 1 m² of collector can transfer to the solar fluid
circulating through.
The objective now is to determine a reasonable area to meet the requirements. As said
in the literature review, the collectors can’t be sized to meet the 200 L hot water needs in
winter, they would be oversized in summer.
The hot water production in litres at terms of each hour of the sunshine duration, for a
typical day of each month, can be determined this way:
𝑉ℎ𝑜𝑡 𝑤𝑎𝑡𝑒𝑟𝑚2𝑐𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟
=𝑄𝑐𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟𝑄𝑑𝑒𝑚𝑎𝑛𝑑200
(𝐿
m2)
Where 𝑄𝑐𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟 is the power provided by the collector during an hour which makes it an
amount of energy in Wh, and 𝑄𝑑𝑒𝑚𝑎𝑛𝑑/200 is the energy needed to heat 1 L of water.
An example of table presenting the volume of hot water
produced according to the collector production is shown on
the table 9.
In this manner, the quantity of water heated up over the day
can be seen accurately so as to be aware of when enough
hot water is available for use. Plus, summing these quantitites
gives the total water volume heated up at the end of the day
for 1 m² collector.
The collector area required in m² is finally found by:
𝐴𝑛𝑒𝑒𝑑𝑒𝑑 =𝑉𝐷𝑎𝑖𝑙𝑦 ℎ𝑜𝑡 𝑤𝑎𝑡𝑒𝑟 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑/m² (𝐿)
𝑉𝐻𝑜𝑡 𝑤𝑎𝑡𝑒𝑟 𝑤𝑎𝑛𝑡𝑒𝑑 (𝐿)
For the month studied
W/m² prod L hot water prod
5.5 0.0 0.0
6.5 0.0 0.0
7.5 0.0 0.0
8.5 20.0 0.3
9.5 130.0 2.2
10.5 140.0 2.4
11.5 170.0 2.9
12.5 180.0 3.1
13.5 180.0 3.1
14.5 170.0 2.9
15.5 140.0 2.4
16.5 130.0 2.2
17.5 20.0 0.3
18.5 0.0 0.0
Total (L/m²) 22.11
January
Table 9. Hot water production (example) in L//m² collector
43
Once the collector area is chosen, the total daily hot water produced for each month is
known, so the amount of energy needed by another source to heat up the rest is
calculated monthly with:
𝑄𝑛𝑒𝑒𝑑𝑒𝑑 =((200 − 𝑉𝐷𝑎𝑖𝑙𝑦 ℎ𝑜𝑡 𝑤𝑎𝑡𝑒𝑟 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑) ∗ 𝜌𝑤𝑎𝑡𝑒𝑟 ∗ 𝐶𝑝𝑤𝑎𝑡𝑒𝑟 ∗ ∆𝑇)
3600(𝑊ℎ)
Both studies with different aspects can then be compared in terms of hot water production
and energy required from the photovoltaic system to meet the rest of the load.
Pump sizing
The system requires a circulating pump to insure the flow rate through the collector of
which the size is dependent on different factors and has to be calculated.
First of all, the velocity of the fluid circulating is:
𝑣 =𝑞
𝑆=
𝑞
(𝜋4 ∗ 𝐷𝑖
2)
Where q is the rated volume flow rate of fluid in 𝑚3/𝑠 given by the collector manufacturer
and 𝐷𝑖 the internal diameter of pipe in m.
The number of Reynold is found:
𝑅𝑒 =𝜌𝑉𝐷𝑖
2
µ
Where ρ = 1013 𝑘𝑔/𝑚3 and µ = 7.85 ∗ 10−5 𝑘𝑔/𝑚. 𝑠 are the fluid density and dynamic
viscosity found at 65˚C for a 40% propylene-glycol mixture.
The relative roughness:
𝑅𝑅 =𝑅𝑆𝐷𝑖
Where 𝑅𝑆 is the roughness of the pipe material which is equal to 1.5 ∗ 10−5 𝑚 for stainless
steel.
44
The friction factor can be determined f, as well as the head loss h:
𝑓 =1.325
(ln (𝑅𝑆
3.7 ∗ 𝐷𝑖+5.74𝑅𝑒0.9
))2 ℎ =
𝑓𝑙𝑣2
2𝑔𝐷𝑖
Where 𝑙 is the pipe length in m and 𝑔 = 9.81 𝑚/𝑠2 is the acceleration of gravity.
The pump hydraulic output required is finally:
𝑃𝑜𝑢𝑡 = 𝜌𝑔(ℎ + 𝐻) ∗ 𝑞 (W)
Where H is the net height (m) difference between the collector and the water tank.
3.5 Ground Source Heat Pump Study
In this part, the focus will be on sizing the ground source heat pump in order to meet the
biggest load of the year (coldest month) in space heating and hot water.
Figure 28. Ground temperature over the year according to the depth, in France (Collecteurderosee, 2015)
45
The quantity of heat collected for a given length of pipe is very dependent on the ground
temperature at the location.
The ground loops are usually buried at a depth comprised between 1 and 2 m, the
temperature at 1.5 m below the ground surface will be considered in this study.
The temperatures shown on the figure 28 are listed below as well as the temperatures at
which the fluid enters the ground heat exchanger for each month. These depend on the
ambient outside air temperature and have to be assumed.
A parameter to take into account is that the fluid used is a 13% glycol-ethylene mixture
offering relatively good performances with an acceptable freezing point at -4˚C.
Determination of the rate of heat absorption
The aim of the procedure explained here is to define the rate of heat absorption per meter
of underground pipe which will allow afterward, to size the pipe length necessary to meet
the load.
First, an outlet fluid temperature (temperature at which the fluid leaves the ground
exchanger) has to be assumed so as to determine the film temperature which in turn,
allows to determine the thermophysical fluid properties used in the calculations. This
outlet temperature reasonably assumed regarding the ground temperature, is redefined
theoretically later. Also, the volumetric flow rate is assumed to be 𝑞 = 6. 10−4𝑚3/𝑠.
𝑇𝑓 =𝑇𝑖𝑛𝑙𝑒𝑡 + 𝑇𝑜𝑢𝑡𝑙𝑒𝑡
2
The film temperature is entered in the excel file “Ethylene Glycol Thermophysical
properties” available on Moodle, the corresponding properties are found and the Reynold
number can be calculated:
𝑅𝑒 =𝜌𝑣𝐷𝑖
2
µ 𝑤𝑖𝑡ℎ 𝑣 =
𝑞
(𝜋4 𝐷𝑖
2)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ground temperature at 1.5 m (˚C) 6 4 4 5.5 6.5 9 12 14 16 16 12 7
Fluid inlet temperature (˚C) 1 1 1 3 3 3 5 5 5 3 2 1
Table 10. Listing of temperatures over the year
46
Where ρ and µ are the fluid density and dynamic viscosity at 𝑇𝑓, 𝑣 is the fluid velocity in
m/s and 𝐷𝑖 is the internal pipe diameter.
The friction factor:
𝑓 =1.325
(ln (𝑅𝑆
3.7 ∗ 𝐷𝑖+5.74𝑅𝑒0.9
))2
Where 𝑅𝑆 = 3. 10−6 is the surface roughness of the polypropylene constituting the pipe
coil.
The Nusselt number:
𝑁𝑢 = 0.023 ∗ 𝑅𝑒45 ∗ 𝑃𝑟0.4
With Pr the Prandt number found at 𝑇𝑓.
𝑁𝑢 allows the calculation of the pipe internal heat transfer coefficient ℎ𝑖:
ℎ𝑖 =𝑁𝑢 ∗ 𝑘
𝐷𝑖 (𝑊
𝑚2. 𝐾)
Where k is fluid thermal conductivity at 𝑇𝑓 in W/m.k.
The total rate of heat absorption in W/m pipe is given by:
𝑄𝑇 =𝑈𝐴
𝐿 𝐿𝑀𝑇𝐷 ; 𝑤𝑖𝑡ℎ 𝐿𝑀𝑇𝐷 =
𝛥𝑇𝑖 − 𝛥𝑇𝑜
ln (𝛥𝑇𝑖𝛥𝑇𝑜
)
𝐴𝑛𝑑 𝐿
𝑈𝐴=
1
𝜋 ∗ 𝐷𝑖ℎ𝑖+ln (𝐷𝑒𝐷𝑖)
2𝜋𝑘𝑝𝑖𝑝𝑒+
ln(2𝑅𝐷𝑒)
2𝜋𝑘𝑔𝑟𝑜𝑢𝑛𝑑
Where 𝐷𝑒 is the external pipe diameter in m, 𝑘𝑝𝑖𝑝𝑒 = 0.45 𝑊/𝑚.𝐾 and 𝑘𝑔𝑟𝑜𝑢𝑛𝑑 =
1.2 𝑊/𝑚.𝐾 are the thermal conductivities of the pipe and the ground and R is the slinky
radius R = 1 m given by the pipe manufacturer.
The rate of heat absorption in W/m is now known, the following approach is to determine
the length of pipe as to deliver the heat demanded.
47
Determination of the required pipe length
The potential rate of heat delivery from the ground is:
𝐻𝑒𝑎𝑡 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑦 = 𝑄 (𝑊
𝑚) ∗ 𝐿 + (
1
𝐶𝑂𝑃 − 1∗ 𝑄 (
𝑊
𝑚) ∗ 𝐿) (𝑊)
Where COP is the performance coefficient of the heat pump, also given by the
manufacturer.
Plus, the energy available for each month is:
𝐸𝑛𝑒𝑟𝑔𝑦 𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑖𝑙𝑖𝑡𝑦 = 𝐻𝑒𝑎𝑡 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑦 ∗ 24 ∗ 𝑁𝑑 (𝑊ℎ/𝑚𝑜𝑛𝑡ℎ)
Where 24 is the number of hours in a day and 𝑁𝑑 the number of days in the month
studied.
Even when the load is the biggest, the energy available must be equal to the energy
demand in space heating and hot water:
𝐸𝑛𝑒𝑟𝑔𝑦 𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑖𝑙𝑖𝑡𝑦 = 𝐿𝑜𝑎𝑑 (𝑤𝑎𝑡𝑒𝑟 + ℎ𝑒𝑎𝑡𝑖𝑛𝑔) = 𝐻𝑒𝑎𝑡 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑦 ∗ 24 ∗ 𝑁𝑑
Where the load is the sum of the energy needed for space heating and providing hot
water, monthly.
Hence, 𝐸𝑛𝑒𝑟𝑔𝑦 𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑖𝑙𝑖𝑡𝑦 = 𝐿𝑜𝑎𝑑 = (𝑄 ∗ 𝐿 + (1
𝐶𝑂𝑃−1∗ 𝑄 ∗ 𝐿)) ∗ (24 ∗ 𝑁𝑑)
The length of pipe necessary to meet the load is finally found by isolation:
𝐿 =𝐿𝑜𝑎𝑑
(1 +1
𝐶𝑂𝑃 − 1) ∗ 𝑄 ∗ 24 ∗ 𝑁𝑑
48
Reiterations and pumps sizing
For a given pipe length L, 𝑇𝑜𝑢𝑡𝑙𝑒𝑡 assumed earlier in the procedure is recalculated by:
𝑇𝑜𝑢𝑡𝑙𝑒𝑡 = (𝑄 ∗ 𝐿
�̇� ∗ 𝐶𝑝) + 𝑇𝑖𝑛𝑙𝑒𝑡 (˚C) 𝑤𝑖𝑡ℎ 𝑄 =
𝑈𝐴𝛥𝑇
𝐿(𝑊
𝑚)𝑎𝑛𝑑 𝛥𝑇 = 𝑇𝑔𝑟𝑜𝑢𝑛𝑑 − 𝑇𝑓𝑙𝑢𝑖𝑑 𝑖𝑛𝑙𝑒𝑡
�̇� (𝑘𝑔
𝑠) = 𝑞 (
𝑚3
𝑠) ∗ 𝜌𝑓𝑙𝑢𝑖𝑑𝑒(
𝑘𝑔
𝑚3) is the mass flow rate of the fluid, 𝐶𝑝 is its specific heat
capacity in J/kg.K at 𝑇𝑓, and 𝑈𝐴
𝐿=
1
𝐿/𝑈𝐴 calculated previously.
The new outlet temperature allows to find a new 𝑇𝑓 for the determination of the fluid
thermophysical properties which differ slightly from before. The procedure is reiterated
from the beginning until another and final 𝑇𝑜𝑢𝑡𝑙𝑒𝑡 is found; and considered in the new
calculation of the total rate of heat absorption 𝑄𝑇. Going through the other formulas, a
new length is determined.
The circulating pump which ensures the flow rate through the circuit must also be sized.
The hydraulic pump output required is:
𝑃𝑜𝑢𝑡 = 𝜌𝑔𝐻 ∗ 𝑞 (𝑊) 𝑤𝑖𝑡ℎ 𝐻 =𝑓𝑙𝑣2
2𝑔𝐷𝑖
Where 𝑔 = 9.81 𝑚/𝑠2 is the acceleration of gravity, 𝐻 is the pump head loss and 𝑙 is the
pipe length, both in m.
Once the pump is chosen, the realistic flow rate circulated must be revised as the power
output won’t exactly be equal to the theoretical one:
𝑞𝑟𝑒𝑎𝑙 =𝑃𝑜𝑢𝑡𝜌𝑔𝐻
𝑖𝑛 𝑚3/𝑠
Thanks to the flow rate, a new fluid velocity is determined and the whole process is
repeated for finding a more accurate and final length of pipe.
The pipe was sized to provide the energy necessary for heating space and water, now
the heat pump must be also able to provide enough power when the load is at its biggest
(W).
49
The heating power demanded from the GSHP is the total energy required divided by the
time over which the heat is supplied:
𝑄ℎ𝑒𝑎𝑡𝑖𝑛𝑔 =𝐸𝑤𝑎𝑡𝑒𝑟 ℎ𝑒𝑎𝑡𝑖𝑛𝑔 (𝑊ℎ)
𝑡𝑤𝑎𝑡𝑒𝑟 ℎ𝑒𝑎𝑡𝑖𝑛𝑔 (ℎ)+𝐸𝑠𝑝𝑎𝑐𝑒 ℎ𝑒𝑎𝑡𝑖𝑛𝑔 (𝑊ℎ)
𝑡𝑠𝑝𝑎𝑐𝑒 ℎ𝑒𝑎𝑡𝑖𝑛𝑔 (ℎ) (𝑊)
It is considered that the water for domestic use should be heated over 10 hours (could be
overnight). For space heating, the power can be assumed to be delivered over 24 hours.
The longer the time, the smaller the pump required.
The COP in a way, corresponds to the pump efficiency. For a given heating power, the
electrical power required is:
𝑄𝑒𝑙𝑒𝑐 =𝑄ℎ𝑒𝑎𝑡𝑖𝑛𝑔
𝐶𝑂𝑃 (𝑊)
50
3.6 Solar Photovoltaic Study
Electric load analysis
When undertaking a photovoltaic feasibility study, first of all,
the daily electric load of the house must be analysed for each
month.
In the case where the PV is combined with a GSHP for water
and space heating, the energy that the PV must supply to the
ground source heat pump is:
𝐸𝐺𝑆𝐻𝑃 =𝐷𝑎𝑖𝑙𝑦 𝑙𝑜𝑎𝑑 (𝑤𝑎𝑡𝑒𝑟 + ℎ𝑒𝑎𝑡𝑖𝑛𝑔)
𝐶𝑂𝑃𝐺𝑆𝐻𝑃 (𝑊ℎ)
For the option in which the PV is combined with a thermal
installation and an electric heating system, the energy which
is to supply to compensate the heat losses equals to the total
heat lost power of the house calculated previously multiplied
by 24 hours.
The energy consumption of each electrical appliance of the
house is added in each option:
𝐸𝑒𝑞𝑢𝑖𝑝𝑚𝑒𝑛𝑡 = 𝑃 ∗ 𝑡
Where P is the power (W) of the device and t is its running
time per day (h).
Figure 29. PV installation scheme
51
According to the period of the year the total energy demand is analysed. Few differences
appear depending on the period and obviously whether the PV runs a GHSP or an electric
heating combined with thermal system.
The listing above shows several devices assumed to be in the house and their
corresponding daily running time.
The lights are supposed to be left on for longer in winter than in summer, their
consumption is higher. Inversely, the fridge would run for a shorter time in winter.
The consumptions missing in the table can be determined only after the sizing of the
installations.
In the option 1, an immersion heater in the water tank is needed to complete the water
heating, as the thermal can only do a part of it.
Furthermore, the photovoltaic installation must support peaks of power (W) as it can
occur in winter which is why a coldest day scenario was simulated. The installation must
theoretically be able to supply the power demanded by the all the appliances, plus the
water and space heating systems in the “coldest day”, all of them powered
simultaneously.
The compensation of the heat losses being the most important part of the electric load
and varying greatly over the year, the load will then be analysed monthly.
Quantity Power (W) Max hours/day W.h/day Max hours/day W.h/day
Living room/kitchen lights 3 21 4 84 2 42
Bathroom light 1 7 1.5 10.5 1 7
Light bedroom 1 1 12 1 12 0.5 6
Fridge 1 100 6.5 650 8 800
Laptop 1 60 2 120 2 120
Phone charger 1 5 2 10 2 10
Radio alarm 1 2 24 48 24 48
Either Option 1: PV + Thermal and electric heating systems
Thermal circulating pump 1 - 10 - 14 -
Water electric heater 1 - 0.5 - 0.5 -
Electric heating system 1 - 24 - 0.5 -
Or Option 2: PV + GSHP systems
GSHP 1 - 24 9
GSHP circulating pump 1 - 24 - 9 -
Winter Summer
Table 11. House electric load analysis
52
Production of the panels
The load was determined, the focus is now the electricity that the system will be able to
produce.
As for the thermal part, the slope global was relieved in a table for a 180˚ aspect and 30˚
tilt.
For each hour of the day in each month, the power produced per m² panel is:
𝑄𝑃𝑉 = 𝑆𝑙𝑜𝑝𝑒 𝑔𝑙𝑜𝑏𝑎𝑙 ∗ % 𝑝𝑎𝑛𝑒𝑙 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 ( W/m²)
The sum of all these hourly 𝑄𝑃𝑉 gives the energy finally produced at the end of the day.
The real energy available per m² panel is obtained by:
𝐸𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒 = 𝐸𝑃𝑉 ∗ %𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑃𝑉 𝑒𝑙𝑒𝑚𝑒𝑛𝑡𝑠 ( Wh/m²)
Where %𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑃𝑉 𝑒𝑙𝑒𝑚𝑒𝑛𝑡𝑠 is the multiplication of the MPPt, batteries and inverter
efficiencies.
According to both the load and production found and to the available roof area, the surface
of the panels can be chosen; and the part of the load covered monthly can be analysed.
MPPt and inverter choice
The electricity coming out of the MPPt must be under the same operating voltage as the
battery bank which must be chosen regarding the power demand (W). The higher the
demand, the higher the voltage in order to help reduce the intensity required in the
system.
A rated intensity (A) is given by the manufacturer so the power that the MPPt can let pass
through is:
𝑃 = 𝐼𝑟𝑎𝑡𝑒𝑑 ∗ 𝑉𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 (𝑊)
Ideally, the product above must be superior or equal to the maximum power produced by
the collectors. The MPPt device must be well chosen according to its rated intensity so it
does not reduce the energy going to be stored in the batteries.
The inverter must be selected regarding the battery voltage and the specification of its
peak power load that it can handle.
53
Battery bank sizing
The capacity storage must be sized according to the load in energy.
The required system electrical storage capacity is calculated by:
𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 =𝐷𝑎𝑖𝑙𝑦 𝑙𝑜𝑎𝑑 ∗ 𝑁𝑏𝑑𝑎𝑦𝑠 𝑎𝑢𝑡𝑜𝑛𝑜𝑚𝑦
%𝐷𝑜𝐷𝑚𝑎𝑥 ∗ 𝑆𝑦𝑠𝑡𝑒𝑚 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 (𝐴ℎ)
Where 𝑁𝑏𝑑𝑎𝑦𝑠 𝑎𝑢𝑡𝑜𝑛𝑜𝑚𝑦 is the autonomy allowed to the installation to prevent from days
when the production is low, for example, on dull and cloudy days.
%𝐷𝑜𝐷𝑚𝑎𝑥 is the maximum depth of discharge of the batteries accorded to preserve their
lifetime. The daily load in Wh taken for batteries sizing is the biggest load of the year
obtained from previously.
The number of batteries in series (additive voltage) and the number of series strings
(additive capacity) must be determined according to the capacity and operating voltage
selected before.
𝑁𝑏𝑠𝑒𝑟𝑖𝑒 =𝑆𝑦𝑠𝑡𝑒𝑚 𝑣𝑜𝑙𝑡𝑎𝑔𝑒
𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑎𝑛𝑑 𝑁𝑏𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙𝑒 𝑠𝑡𝑟𝑖𝑛𝑔𝑠 =
𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦
𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦
For the 𝑁𝑏𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙𝑒 𝑠𝑡𝑟𝑖𝑛𝑔𝑠, the nearest whole number to the value found is taken in account.
Thus, the exact number of batteries is known and the rated capacity can be recalculated.
54
4 Chapter Four: Results and Findings
The hourly values of 𝐼𝐺, 𝐼𝐷 and all the components as the slope global, slope beam, diffuse
and direct radiations needed for the calculations are registered in the excel file on the CD-
ROM provided with this report, as well as the calculations themselves.
4.1 Needs Analysis
Passive gains
Solar gains through windows
The hourly results of the solar gains for a typical day in each month of the year are given
in appendix A.
An overview is presented in the following table:
Sensible heat from humans
Between 2 and 3 kWh/day average energy gained over the year with a slight peak during the hot
period, as expected.Sensible heat emissions of humans
January February March April May June July August September October November December
South 1.67 1.96 2.25 1.90 1.79 1.79 1.97 2.15 2.29 1.94 1.65 1.37
East 0.36 0.45 0.72 0.88 1.07 1.22 1.32 1.11 0.89 0.53 0.33 0.22
Total 2.03 2.41 2.97 2.78 2.86 3.01 3.28 3.26 3.18 2.47 1.97 1.59
Table 12. Energy entering in the building in kWh, daily
Occupancy time 12 h
Heat emitted per occupants 70 W
Number of occupants 4
Total energy gained 3.36 kWh/dayTable 13. Energy gained from human occupation
55
Heat losses
Energy lost
Taverage (°C) Walls Door + windows Roof Ventilation Thermal bridges (5%) Floor (9%) Total Total (kWh/day)
January -0.8 201.1 154.3 199.3 265.5 47.7 85.8 953.7 22.9
February 0.3 188.8 144.5 187.0 250.0 44.8 80.6 895.7 21.5
March 3.7 151.5 114.6 149.4 202.0 35.9 64.6 718.0 17.2
April 6.7 118.3 89.2 116.6 159.6 28.1 50.6 562.4 13.5
May 11.8 63.0 46.5 61.7 87.6 15.0 27.1 300.9 7.2
June 15.6 22.7 16.7 22.4 33.9 5.6 10.0 111.3 2.7
July 18.2 0 0 0 0 0 0 0 0
August 17.9 0 0 0 0 0 0 0 0
September 13.5 44.4 32.8 43.9 63.6 10.7 19.3 214.7 5.2
October 9.2 90.4 67.1 89.5 124.3 21.6 38.9 431.7 10.4
November 3.3 155.3 117.9 153.8 207.6 36.9 66.4 737.9 17.7
December 0.3 188.8 144.5 187.0 250.0 44.8 80.6 895.7 21.5
Heat losses (W)
Coldest day case scenario - 3/1/1971
Energy lost
Tmin (°C) Walls Door + Windows Roof Ventilation Thermal bridges Floor Total kWh/day
-27.1 493.1 394.30 498.30 639.90 117.6 211.7 2354.9 56.5
Heat loss (W)
Table 15. Heat losses, coldest day scenario 3/1/1971
Table 14. Overall heat losses of the house
Figure 30.Total energy gained inside the house by month
56
A table of losses repartition which appears to be quite similar as the indicative values
seen in the implementation. A complete table of repartition for each month is given in
appendix A.
Finally, the total energy loss of the house:
The tendency over the year can be visualised below:
The losses are more important during December and January with 16.5 and 17.5 kWh
per day. It is the period which the study aims at sizing the installations according to.
January February March April May June July August September October November December
Heat lost (kWh) 22.9 21.5 17.2 13.5 7.2 2.7 0.0 0.0 5.2 10.4 17.7 21.5
Heat gains (kWh) 5.4 5.8 6.3 6.1 6.2 6.4 6.6 6.6 6.5 5.8 5.3 5.0
Total heat lost (kWh) 17.5 15.7 10.9 7.4 1.0 0 0 0 0 4.5 12.4 16.5
Table 17. Heat lost - heat gained per day, overview
Figure 31. Total energy lost by month
Walls Door + windows Roof Ventilation Thermal bridges Floor
20.9% 15.8% 20.7% 28.6% 5.0% 9.0%
Table 16. Year average heat losses repartition (%)
57
Hot water demand
11.6 kWh/day for heating water all year represents the third of the total daily load in winter.
From this, the collector area required can be found and its corresponding production over
the year, evaluated.
4.2 Solar Thermal Study
Collector production
Table 18. Calculation of the energy needed for heating water
Table 19. Hourly production of hot water (L) according to the heat produced by 3m2 collector (W) - South
Panel area (m2) Efficiency
3 76%
W L W L W L W L W L W L
122.3 2.1 56.2 1.0 0 0 0 0 0 0 0 0
376.1 6.5 281.2 4.9 141.4 2.4 0 0 0 0 0 0
700.7 12.1 599.1 10.3 427.6 7.4 226.0 3.9 26.6 0.5 0 0
1034.6 17.9 935.6 16.2 746.4 12.9 472.6 8.2 323.1 5.6 80.6 1.4
1337.3 23.1 1246.6 21.5 1050.6 18.1 717.7 12.4 524.1 9.1 455.7 7.9
1567.6 27.1 1486.1 25.7 1289.6 22.3 914.9 15.8 691.7 11.9 611.4 10.6
1692.1 29.2 1616.5 27.9 1421.2 24.5 1025.0 17.7 786.5 13.6 700.6 12.1
1692.2 29.2 1616.7 27.9 1421.4 24.6 1025.2 17.7 786.7 13.6 700.6 12.1
1567.8 27.1 1486.5 25.7 1290.3 22.3 915.6 15.8 692.2 12.0 611.5 10.6
1337.6 23.1 1247.2 21.5 1051.6 18.2 718.7 12.4 525.1 9.1 455.9 7.9
1034.9 17.9 936.4 16.2 747.5 12.9 473.9 8.2 324.6 5.6 80.5 1.4
701.0 12.1 599.8 10.4 428.8 7.4 227.8 3.9 26.6 0.5 0.0 0.0
376.2 6.5 281.4 4.9 142.4 2.5 0 0 0 0 0 0
122.1 2.1 56.0 1.0 0 0 0 0 0 0 0 0
236.0 215.0 175.5 116.0 81.3 63.9
November DecemberJuly August September October
HOURS W L W L W L W L W L W L
5.5 0 0 0 0 0 0 14.7 0.3 82.7 1.4 133.1 2.3
6.5 0 0 0 0 40.9 0.7 197.1 3.4 296.1 5.1 371.8 6.4
7.5 74.5 1.3 72.9 1.3 347.9 6.0 466.5 8.1 578.5 10.0 667.3 11.5
8.5 462.4 8.0 449.3 7.8 661.7 11.4 759.3 13.1 875.9 15.1 969.2 16.7
9.5 507.5 8.8 707.9 12.2 966.3 16.7 1034.2 17.9 1149.2 19.9 1241.8 21.4
10.5 581.0 10.0 917.6 15.8 1208.0 20.9 1248.0 21.6 1359.0 23.5 1448.6 25.0
11.5 625.7 10.8 1034.8 17.9 1341.6 23.2 1364.9 23.6 1472.9 25.4 1560.3 27.0
12.5 625.6 10.8 1034.5 17.9 1341.4 23.2 1364.7 23.6 1472.8 25.4 1560.3 27.0
13.5 580.5 10.0 916.9 15.8 1207.4 20.9 1247.6 21.5 1358.7 23.5 1448.6 25.0
14.5 506.6 8.8 706.8 12.2 965.3 16.7 1033.6 17.9 1148.9 19.8 1241.7 21.4
15.5 460.1 7.9 447.8 7.7 660.4 11.4 758.6 13.1 875.5 15.1 969.2 16.7
16.5 73.8 1.3 73.3 1.3 346.5 6.0 465.8 8.0 578.1 10.0 667.2 11.5
17.5 0 0 0 0 41.1 0.7 196.8 3.4 296.0 5.1 371.8 6.4
18.5 0 0 0 0 0 0 14.7 0.3 82.9 1.4 133.1 2.3
Total (in L): 77.7 109.9 157.7 175.6 200.8 220.8
January February March April May June
HOURS W L W L W L W L W L W L
5.5 0 0 0 0 0 0 14.7 0.3 82.7 1.4 133.1 2.3
6.5 0 0 0 0 40.9 0.7 197.1 3.4 296.1 5.1 371.8 6.4
7.5 74.5 1.3 72.9 1.3 347.9 6.0 466.5 8.1 578.5 10.0 667.3 11.5
8.5 462.4 8.0 449.3 7.8 661.7 11.4 759.3 13.1 875.9 15.1 969.2 16.7
9.5 507.5 8.8 707.9 12.2 966.3 16.7 1034.2 17.9 1149.2 19.9 1241.8 21.4
10.5 581.0 10.0 917.6 15.8 1208.0 20.9 1248.0 21.6 1359.0 23.5 1448.6 25.0
11.5 625.7 10.8 1034.8 17.9 1341.6 23.2 1364.9 23.6 1472.9 25.4 1560.3 27.0
12.5 625.6 10.8 1034.5 17.9 1341.4 23.2 1364.7 23.6 1472.8 25.4 1560.3 27.0
13.5 580.5 10.0 916.9 15.8 1207.4 20.9 1247.6 21.5 1358.7 23.5 1448.6 25.0
14.5 506.6 8.8 706.8 12.2 965.3 16.7 1033.6 17.9 1148.9 19.8 1241.7 21.4
15.5 460.1 7.9 447.8 7.7 660.4 11.4 758.6 13.1 875.5 15.1 969.2 16.7
16.5 73.8 1.3 73.3 1.3 346.5 6.0 465.8 8.0 578.1 10.0 667.2 11.5
17.5 0 0 0 0 41.1 0.7 196.8 3.4 296.0 5.1 371.8 6.4
18.5 0 0 0 0 0 0 14.7 0.3 82.9 1.4 133.1 2.3
Total (in L): 77.7 109.9 157.7 175.6 200.8 220.8
January February March April May June
Water V (L) Tin (˚C) Tout (˚C) ΔT
200.0 15 65 50.0
Water V (m3) ρwater m (kg) Cp (J/kg.K) Q (kJ) Q (kWh)
0.2 996.0 199.2 4185.0 41683 11.6
Total energy
needed:
58
Thanks to the tables above, the production of hot water can be monitored at each hour of
the day in each month of the year. It is noticed that there is always availability for use in
the evening.
The graphs showing the hot water produced and the energy required to complete the
heating are given below.
0.0
20.0
40.0
60.0
80.0
100.0
120.0
%
Figure 32. Energy required by the immersion heater to produce the rest
Figure 33. Volume of hot water produced over the volume required, per day (%)
59
3 m2 of solar thermal collectors south-oriented seems reasonable so that there is no
overproduction in summer. Though, the theoretical production is a bit higher than required
in summer which can be considered as a margin. The collector area is sufficiently
important to meet 100% of the needs from May to September and can supply about the
half during the rest of the year. As shown on the figure 33, about 60% of the energy
required to heat the water must be supplied by the heater during the coldest months of
the year.
Pump sizing
The thermal panel chosen is a Clearline V30 of which the spreadsheet is given in
appendix B. The pump was sized according to its rated flow indicated in the specifications.
The pump needed is a low cost small motor.
Absorber area 3.0 m²
Aperture area 3.1 m²
Efficiency 76 %
Rated flow 150 l/h
4E-05 m3/s
Clearline V30 panel
Pipe disc surface 7.85E-05 m²
Velocity 5E-01 m/s
Re 36319.3
S roughness 1.50E-05
Relat. Roughness 1.50E-03
Friction factor 2.66E-02
Head losses 0.762 m
Poutput required 2.4 W
Circulating pump sizing
Table 20. Thermal collector specifications Table 21. Circulating pump sizing
60
4.3 Ground Source Heat Pump Study
Production
The lowest rate of heat absorption and therefore, the lowest production of energy occurs
in February due to the low ground temperature. For this reason and even though the load
is not maximum at this period, it is the month over which the demand requires the highest
value of pipe length, in order to be fully covered. Thus, the pipe coil was sized according
to this fact and found equal to 155 m.
The results demonstrate that the system can insure the heating all over the year with a
certain margin in winter and could theoretically produce up to eight times more energy in
summer, when the demand only corresponds to the domestic hot water production.
Sizing of the pumps
Circulating pump
The theoretical power output of the circulating
pump was estimated at 24.5 W.
A 40 W “Grundfos” pump providing a 30 W
actual power output (75% efficiency) was
chosen (appendix D) so the actual flow rate
had been revised and the energy production
calculations, reiterated according to it.
Pipe coil length: 155 m
Month J F M A M J J A S O N D
(Space + water heating) load (kWh/month) 901.5 791.8 696.8 568.1 389.9 347.4 347.4 347.4 347.4 499.3 718.6 871.8
Rate of heat absorption (W/m) 8.4 5.1 5.1 4.2 5.9 10.1 11.8 15.2 18.6 21.9 16.9 10.1
Rate of heat absorption (kW) 1.3 0.8 0.8 0.7 0.9 1.6 1.8 2.4 2.9 3.4 2.6 1.6
Potential rate of heat delivery (kW) 1.8 1.1 1.1 0.9 1.2 2.1 2.5 3.2 3.9 4.6 3.6 2.1
Energy availability (kWh/month) 1325.7 795.7 795.7 663.6 927.8 1588.3 1855.6 2387.1 2924.9 3443.9 2657.6 1588.3
% of the load covered 147% 100% 114% 117% 238% 457% 534% 687% 842% 690% 370% 182%
Table 22. GSHP energy production
Basic flow rate 0.0006 m3/s
Relative roughness 0.0001
Friction factor 0.3065
Head loss 4.1 m
Poutput required 24.5 W
Electrical rating 40 W
Efficiency 75 %
Actual Poutput 30 W
Revised flow rate 0.00073 m3/s
Circulating pump sizing
Table 23. Circulating pump sizing
61
GSHP
The ground source heat pump “Kensa” of which the specifications sheet is given in
appendix D has a COP which can be averaged to 4 over the year. It means that during a
typical day in January (month representing the biggest load), it would need 0.5 kW of
electrical power to insure the space and water heating over 24 and 10 hours respectively.
To envisage a very cold day, the pump must be able to provide 3.3 kW of heating power,
inducing an electrical power consumption of 0.8 kW that the PV system must make
available.
The GSHP chosen is in fact of 3 kW electrical power meaning that the energy required in
a typical day can be delivered over a period more than six times shorter than assumed,
which implies the circulating pump to run also during a shorter time, saving some energy.
Table 24. GSHP sizing calculations
Space Water
17.5 11.6
/ time (h) 24 10
Heating output (kW) 0.7 1.16
Tot. heating Output (kW)
COP
Electrical Pintput (kW) 0.5
January typical day
Heating load (kWh)
4
1.9
Space Water
51.1 11.6
/ time (h) 24 10
Heating output (kW) 2.1 1.16
Tot. heating Output (kW)
COP
Electrical Pintput (kW)
Heating load (kWh)
Coldest day
3.3
4
0.8
62
4.4 Solar Photovoltaic Study
Electric load analysis
As a first step, the energy consumption of each electrical appliance (heating system not
included) was analysed in summer and in winter as well as the power that they would
demand if they were all running simultaneously.
In the option (1), it is logically considered that the circulating pump would be powered for
a period of time corresponding to the sunshine duration in a day, which differs according
to the period of the year. Also, the fridge runs longer in summer and so is the cause of a
higher energy consumption at this period.
In the option (2), the 3 kW GSHP could theoretically provide enough in energy to meet
the biggest load (January) in less than 3 hours but the heating time was maximally
assumed keeping a margin for the estimation of the circulating pump energy
consumption.
The second step was to analyse the total electric load by month including the consumption
of the water and space heating systems in both cases.
Table 25. Electrical appliances load analysis (heating system not included)
Quantity Power (W) Max hours/day W.h/day Max hours/day W.h/day
Living room/kitchen lights 3 21 4 84 2 42
Bathroom light 1 7 1.5 10.5 1 7
Light bedroom 1 1 12 1 12 0.5 6
Fridge 1 100 6.5 650 8 800
Laptop 1 60 2 120 2 120
Phone charger 1 5 2 10 2 10
Radio alarm 1 2 24 48 24 48
(1) Thermal circulating pump 1 2.4 10 24 14 33.6
(2) GSHP circulating pump 1 40 7 280 5 214.4
(1) Total 209.4 958.5 Wh/day 1066.6 Wh/day
(2) Total 247 1214.5 Wh/day 1247.4 Wh/day
Winter Summer
63
The most important electric load occurs in January for both options. The sizing must be
undertaken in a way that the production is enough to meet the needs at this period.
In the first option compared to the second, the demand is lower in summer as the water
heating is insured without using any electric source of energy. Inversely in winter, the load
in the option 2 is widely lower thanks to the GSHP coefficient of performance.
The values indicated on the table above for the heating systems are the powers that they
would require to compensate the heat losses in a day as the coldest one simulated earlier.
The power provided by the electric heating system is equal to the heat lost power. The
GSHP demands 3 kW of electrical power in any case.
To complete the domestic water heating in the option 1, a 3 kW immersion heater is
included in the cylinder chosen (appendix E). The selection is explained later in the
economic part.
The PV system must be sized so that it can supply the power required in the case where
all the elements would be powered simultaneously (total shown on table 29).
Option 1 Option 2
Immersion heater 3 -
Heating system 2.4 3
Electrical applicances 0.21 0.25
Total 5.6 3.3
Table 27. Option 1, total electrical load analysis (kWh/day)
Table 26. Option 2, total electrical load analysis (kWh/day)
Table 28. Power demand analysis (kW)
Month J F M A M J J A S O N D
Total heating load 29.1 27.3 22.5 18.9 12.6 11.6 11.6 11.6 11.6 16.1 24.0 28.1
GSHP electrical load 7.3 6.8 5.6 4.7 3.1 2.9 2.9 2.9 2.9 4.0 6.0 7.0
Electrical applicances load 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2
Total electric load 8.5 8.0 6.8 6.0 4.4 4.1 4.1 4.1 4.1 5.2 7.2 8.2
Month J F M A M J J A S O N D
Space heating load 17.5 15.7 10.9 7.4 1.0 0.0 0.0 0.0 0.0 4.5 12.4 16.5
Immersion heater load 7.1 5.2 2.4 1.4 0 0 0 0 1.4 4.9 6.9 7.9
Electrical appliances load 1.0 1.0 1.0 1.1 1.1 1.1 1.1 1.1 1.1 1.0 1.0 1.0
Total electric load 25.6 21.9 14.3 9.9 2.1 1.1 1.1 1.1 2.5 10.4 20.3 25.4
64
Production of the panels
Knowing the energy received, the PV production per m² was estimated assuming, at the
beginning, the efficiency of the panel. Hence, it was found that the most PV area possible,
according to the surface of the roof available, should be installed as in any case the load
would not be fully covered all year. Once the panel and the other elements constituting
the whole system were chosen, the realistic PV production and energy available were
recalculated taking the given efficiencies into account.
The PV panel suggested is the “Clearline PV 16/250” of which the specifications are given
in appendix F. Its efficiency is 15.6 %, global area: 1.63 m² allowing 1.6 m² to absorb the
sunlight.
24.05 m² of roof area permits the installation of 12 of them in the first option due to the
thermal system already having some space allocated, and 14 in the other one.
The solar energy being abundant with a load being the lowest from April to September,
the needs in electricity can be fully covered during this period in both options. The
theoretical energy available could even be up to about 15 times what is necessary in the
Battery losses 95%
Cabling losses 94%
MPPt 96%
Inverter 95%
Total 81%
Due to
Table 29. PV system efficiencies
Table 30. PV energy production analysis
Panels efficiency: 15.6 % January February March April May June July August September October November December
Energy received (kWh/m2/day) 2.0 2.8 4.0 4.5 5.1 5.6 6.0 5.5 4.5 2.9 2.1 1.6
PV production (kWh/m2/day) 0.3 0.4 0.6 0.7 0.8 0.9 0.9 0.9 0.7 0.5 0.3 0.3
Option 1 : Thermal + electric heating system - 12 panels = 19.2 m² absorber area
Total PV production (kWh/day) 5.9 8.4 12.0 13.4 15.3 16.8 17.9 16.3 13.3 8.8 6.2 4.9
Real energy available (kWh/day) 4.8 6.8 9.8 10.9 12.4 13.7 14.6 13.3 10.9 7.2 5.0 4.0
House electric load (kWh/day) 25.6 21.9 14.3 9.9 2.1 1.1 1.1 1.1 2.5 10.4 20.3 25.4
% load covered 19% 31% 68% 110% 603% 1282% 1370% 1248% 437% 69% 25% 16%
Option 2: GSHP - 14 panels = 22.4 m² absorber area
Total PV production (kWh/day) 6.9 9.8 14.0 15.6 17.8 19.6 20.9 19.1 15.6 10.3 7.2 5.7
Real energy available (kWh/day) 5.6 7.9 11.4 12.7 14.5 16.0 17.1 15.5 12.7 8.4 5.9 4.6
House electric load (kWh/day) 8.5 8.0 6.8 6.0 4.4 4.1 4.1 4.1 4.1 5.2 7.2 8.2
% load covered 66% 100% 167% 211% 330% 385% 416% 379% 306% 161% 82% 56%
65
option 1 and 4 times in the option 2, during the hottest month – July. Though, it will be
seen later that the energy can only be stored to a certain extend.
During the rest of the year, using a GSHP combined with a PV system makes the
difference.
In February, March and October, this system allows a complete energy independence of
the house contrary to the option 1 case.
With this last, about 70 to 80 % of the load is covered which remains acceptable, in March
and October, whereas the same situation occurs in January and November with the other
option. Moreover, for the months of November, December, January and February, the
percentage of the demand covered is about 3 times higher.
0%
20%
40%
60%
80%
100%
120%
140%
160%
180%
January February March October November December
Thermal + elec. heating GSHP
Figure 34. Percentage of the load covered
66
MPPt and inverter selection
The maximum slope global received and therefore the maximum power production of the
panels occurs in a day of July at 11:30am. This corresponds to the power going to the
batteries passing through the MPPt.
Moreover, the maximum power load being quite high in both options (3.3 and 5.6 kW as
seen before), a battery bank under 48 V is suitable, lowering the current in the installation.
This has also been confirmed by a supplier of PV system elements working for “Biowatt
Energie” (email exchange shown in appendix E).
Consequently, the MPPt was chosen regarding its rated current – 70 A, so that it does
not reduce the power transmitted from the panels to the batteries.
The specifications sheet of the “MPPt Blue Solar 150/70” selected for both options is in
the appendix G.
July (11:30am)
Slope global (W/m²) 742.2
Pmax produced opt. 1 2778.7
Pmax produced opt. 2 2408.2W
Table 31. Power produced by the panels
Figure 35. PV system electric indications
67
Also, the maximum solar input power accepted – 4 kW for this device, had to be checked
to be higher than the one produced.
According to the load, the inverters selected are the “Vicron Multiplus 48/5000/70” for the
option 1 and “48/3000/70” for the other (spreadsheets in appendix G). They respectively
allow 5 kW and 3 kW of continuous power output with peaks of up to 10 and 6 kW.
Battery bank sizing
The capacity required was calculated to be able to store the equivalent of the energy
necessary for 4 days, with a 𝐷𝑜𝐷𝑚𝑎𝑥 = 60% chosen to preserve the battery life.
For the option 1, the sizing was first evaluated in January when the load is the biggest. It
results that it would need about twice more batteries than in March, inducing a cost twice
more important for a storage at a period during which the panels are able to produce only
the fourth of the load.
Consequently, it appeared reasonable to adapt the storage for March when 68 % of the
load is covered. The real capacity is slightly lower than the theoretical one so the storage
would equal a little less than 4 days of autonomy for the system in March.
Option 2
January March January
Load (kWh) 25.6 14.3 9.1
No days autonomy
System voltage (V)
DoDmax (%)
Capacity required (Ah) 3555.6 1986.1 1263.9
Number of batt. in series string
Number of // strings 1.9 1.1 1
Realistic number // strings 2 1 1
Tot. number of batteries 48 24 24
Rated capacity (Ah) 3720 1860 1860
Option 1
4
48
60
24
Battery model RBS - Capacity: 1860 Ah ; Voltage: 2 V
Table 32. Battery bank sizing
68
In the second option, the system finally allows a storage of almost 6 days of the biggest
energy demand (January). Both storage solutions require a bank of 24 batteries.
The datasheet of the battery chosen is given in appendix F and was selected according
to economic criteria as it can be seen on the excel sheet “PV sizing”.
The exact number of autonomy days of the PV system and a tendency are given below,
by month and for each option:
January February March April May June July August September October November December
Option 1 2.1 2.4 3.7 5.4 25.9 50.2 50.2 50.2 21.5 5.2 2.6 2.1
Option 2 6.3 6.7 7.8 8.9 12.2 12.9 13.1 13.1 12.9 10.3 7.4 6.5
Table 33. Number of days of autonomy for both options
Figure 36. PV systems number of autonomy days
69
Design overview
An overview of the final PV system design is presented above.
Each panel having a maximum voltage of 30.4 V and current of 8.2 A, the choice of
mounting them in 6 or 7 parallel strings (according to the option) of 2 panels in series
gives the above indicated maximum current and voltage output. It seems to be the best
combination, given the system operating intensity and voltage.
The MPPt starts its function when the PV voltage reaches 55 V (battery voltage + 7 V).
MPPt
Inverter 230 V
I depending on the demand
60.8 V
48 V
48 V
57.4 A 49.2 A
70 A
Option 1 : 6 // strings of 2 panels in series
Option 2 : 7 // strings of 2 panels in series
Figure 37. Final PV design overview
70
4.5 Economic Analysis
The description/specifications sheet and cost of each element cited below is given in their
respective appendix.
Solar thermal installation
Most of the elements were found on the Viridian catalogue presenting very competitive
prices. The solar electric cylinder comprises a coil allocated to the thermal system circuit
to exchange the heat and an immersed water heater as explained in the second chapter.
A device controlling the fluid pressure of the installation as well as some temperature
sensors to insure the smooth running of the system. The pipe correspond are the
connection between the different elements.
The cost due to maintenance is negligible. The labour costs usually represent 30% of the
total installation cost depending on the roof surface covered and the size of the panels.
Denomination Brand/Reference Indications Source Cost (£)
Thermal collector Clearline V30 250 Wp Viridian catalogue 929.38
Solar electric cylinder Steflow 210 DS 210 L, heater 3 kW Viridian catalogue 873.82
Expansion vessel Solar plus 18 L Advancedwater.co.uk 48.22
Pressure controller Clearline V210R Viridian catalogue 150
Temperature sensors Clearline V228 Viridian catalogue 22
Solar fluid Clearline V225 40% prop. Glycol Viridian catalogue 33.88
Pre-insulated pipe Clearline V5110 L = 10 m, Di = 10 cm Viridian catalogue 149.61
Circulating pump Brushless Banggood.com 14.22
Labour 1000
Total £3,221Table 34. Thermal system cost analysis
71
Solar photovoltaic installation
The first option requires an inverter 5 kW costing about £800 more than the 3 kW one
used in the second option. As a compensation, two panels less are used which balances
the final costs. The fact that this installation is off-grid makes it expensive, the batteries
being part of more than 50% of the total cost.
On the excel sheets “PV sizing” for both options, it can be seen that the economic analysis
of several PV panels, MPPts and batteries was carried out, the selection of each device
is underlined in green.
Table 35. PV system cost analysis
Qty Denomination Brand/Reference Source Cost (£)
1 MPPt Blue Solar 150/70 windandsun.co.uk 485.52
24 Battery Rolls S-1860Ah windandsun.co.uk 6670.9
12 PV collector Clearline PV16/250 Viridian catalogue 2592
1 Inverter Victron Multiplus 5000 windandsun.co.uk 1748.88
14 PV collector Clearline PV16/250 Viridian catalogue 3024
1 Inverter Victron Multiplus 3000 windandsun.co.uk 1096.2
Labour 300
Total Option 1: £11,797
Option 2: £11,577
1 st option
2nd option
72
Ground source heat pump installation
The ground source heat pump represents the half of the price. To keep an optimal thermal
exchange, it is advised to replace the fluid every 5 years. It is also important to monitor
the pressure in the installation and to set up a regular checking which can be under the
form of a few years contract.
The cylinder is typical for heat pump comprising a coil for exchanging the heat from the
ground with the domestic water, and an immersed heater for boost and emergency back-
up.
The total costs for both options are finally given below:
Slightly more than £3,000 supplementary to invest in the second option, offering better
advantages. Is that worth it? The next part of this report will help answer this question,
among other.
Denomination Brand/Reference Indications Source Cost (£)
GSHP Kensa 3 kW kensaheatpumps.com 2950
Circulating pump Grandfos 40 W anchorpumps.com 77.5
HP cylinder Gledhill TEC210-HP 210 L plumbnation.co.uk 1208.34
GSHP fluid Thermox DTX20 To replace every 5 years hydratech-shop.co.uk 60.6
Pipe coil BHF L = 250 m ebay.co.uk 400
Labour 2000
Installation checking every 3 years 100
Total £6,796Table 36. Ground source heat pump cost analysis
Table 37. Total cost of each option
Option 1: PV + Thermal systems £15,018
Option 2: PV + GSHP systems £18,373
73
5 Chapter five: Conclusion
5.1 Analysis
A quite constant amount of heat is gained into the house with a 4 to 6.5 kWh/day range
over the year. Similar fact for the 11.6 kWh/day required for heating domestic water.
However, the overall heat lost is very fluctuating due to temperatures variation that the
different systems must handle.
The ground temperature being the lowest in February, it is the month during which the
GSHP installation requires the maximum length of pipe coil – 155 m, to meet the heating
demand even though this last is only the third biggest of the year. This length then insures
enough heat to be removed from the ground for the needs to be fully covered at all time
of the year.
The 3 kW electrical power of the GSHP is more than enough to provide the energy
necessary during a typical day of January as well as to envisage a very cold day scenario
as happened in 1971 when the temperature went down to -27.1 °C.
Talking about the other option, 3 m² of solar thermal collector is enough to provide all the
hot water desired from April to September without overproducing and so, going over the
capacity of the water tank. A bigger cylinder and collector area could have been imagined
but this would affect the capacity of the PV system to produce electricity by reducing the
roof space available.
During the rest of the year, the system allows the acceptable production of about the half
of what is needed. A 3 kW water immersed heater would complete the task when needed.
Also, the water being heated up over the sunshine duration and even though some hot
water use can occur during the day, a large amount of hot water is available from around
6pm in summer allowing showers to be taken and other important consumptions.
In winter, thanks to the COP, the GSHP allows the electrical load to be about three times
lower than with using electric and solar thermal heating systems. In summer, the load is
in turn superior as only the domestic water must be heated, which is done by electric
means contrary to the other option case.
74
Still thanks to the COP, the maximal power load to envisage is also lower with 3.3 against
5.6 kW. In both cases, a 48 V operating voltage was chosen to help reduce the current
needed in the installation to meet the load, and according to which two different inverters
to include in the PV system were selected.
With 19.2 and 22.4 m² of PV panel absorbing areas, the maximum peak power produced
may occur in July with 2.4 and 2.8 kW. These values being close to each other, the MPPt
able to cope with it remains common in both installations.
The water and space heating systems were sized and optimised for meeting their task in
both options while the ability of the PV system to complete its own differs.
In the option 1, the house can be electrically completely independent during the 6 warmest
months of the year while in the option 2, it is the case for a 9 months period (February to
October).
However, the house could be inhabited for 2 months supplementary in each case. In
effect, during the period when three quarters of the load would be covered, the power of
the space heating systems could be reduced and the wood stroke burner which was
considered as a back-up solution so far, could complete the heating. A study must be
done so as to obtain confirmation of the suitability.
Thanks to the 24 batteries storage solution, the option 2 system has a greater autonomy
over the year with about 7 days in winter against 3 for the other option. This is a very
significant parameter to take into account. In mountain, several dull or cloudy days in a
row is not rare, especially during winter.
Around £18,000 against £15,000, the heat pump installation induces the cost to be £3,000
higher for the second option, more performant. The deal seems balanced. Though, if the
investment has for objective to make the house inhabitable mostly during summer, then
the cheapest option is sufficient. If the investment aims at spending winter time in the
house which is most likely the case in view of the location, it is advised to choose the
other option.
75
5.2 Limitations
The heat losses representing the main part of the demand, the sizing of the installations
was mostly based on it. Consequently, it was really important to identify them properly
and a lot of time was spent on it due to the complex methodology of calculation.
Additionally, a sufficient amount of time needs to be allocated in order to fully understand
the scientific theory behind the GSHP study.
Furthermore, a delicate fact to deal with was that everything is linked together which
means that if a parameter changes somewhere due to recalculation, a lot of elements
already found may be affected and procedures may need to be reiterated.
5.3 Further work
The ground source heat pump feasibility was studied considering the pipe coil horizontally
buried which requires a certain availability of space. To increase the system performance,
the ground heat exchanger could be envisaged to be vertically buried even though the
cost would neatly increase.
Also in order to push the study further, the way of laying out the different elements of the
installations could be looked at. The battery bank is quite bulky, the location and manner
the batteries are settled together so as to save some space is a significant factor.
Similarly for the different elements constituting the solar thermal system remaining
numerous. The height separating them and the way they are connected together
according to the house shape would give more information of fluid pressure and would
allow more accurate results.
Finally, the space could be studied to be heated by means of other sources of energy
such as biomass, the natural resources being abundant at the house localisation.
The wind power is also a possible solution for providing electrical energy in this case. The
feasibility study of a hybrid system combining PV and hydro turbine seems to have the
potential to show good performances.
76
6 Bibliography ADEME, 2016. Isolation de la maison. [Online]
Available at: http://franche-comte.ademe.fr/contenu.php?id=327
[Accessed March 2016].
ASHRAE, H., 2001. Fundamentals. [Online]
Available at: http://www.cambeep.eng.cam.ac.uk/References/internalheat
[Accessed February 2016].
Biowatt, 2016. [Interview] (29 February 2016).
CarbonNeutral, 2013. Deep-Cycle Batteries for Off-Grid & Remote Power Systems. [Online]
Available at: http://www.solar-wind.co.uk/deep-cycle-dryfit-batteries-battery-uk.html
[Accessed December 2015].
CIBSE Journal, Y. E., 2016. Solar thermal – solar hot water heating. [Online]
Available at: http://www.cibsejournal.com/cpd/modules/2009-02/
[Accessed October 2015].
CIBSE, 2007. CIBSE guide c, s.l.: CIBSE.
Collecteurderosee, 2015. Température du sol en fonction de la profondeur. [Online]
Available at:
http://www.collecteurderosee.fr/evolution%20temperature%20du%20sol/evolution%20temperat
ure%20du%20sol.html
[Accessed February 2016].
Dankoff, W., 2001. How to choose an inverter for an independent Energy System.
EcoHiSolar, 2011. Solar Thermal Systems. [Online]
Available at: http://www.ecohisolar.co.uk/solar-thermal/
[Accessed November 2015].
EnergyAgency, 2015. Ground source Heat pump. [Online]
Available at: http://www.energyagency.org.uk/en/ground-source-heat-pump_46650/
[Accessed February 2016].
EnergySavingTrust, 2016. Ground source heat pumps. [Online]
Available at: http://www.energysavingtrust.org.uk/domestic/ground-source-heat-pumps
[Accessed February 2016].
Gasappliance, 2013. Domestic Hot Water Cylinders Explained. [Online]
Available at:
http://www.gasapplianceguide.co.uk/Direct%20and%20Indirect%20Cylinders%20Explained.htm
#Categories_of_hot_water_cylinder_
[Accessed November 2015].
Hall, K. & Nicholls, R., 2008. Green Building Bible, Volume 1. 4th ed. Llandsyul: Green Building
Press.
77
HeatPumpAssociation, 2015. Heat pump data. [Online]
Available at:
http://www.heatpumps.org.uk/PdfFiles/HeatPumpGroundToWaterDataSheetNo.2Domestic.pdf
[Accessed February 2016].
Muneer et al, 2014. Monthly-averaged, k - kt relationship. Journal of Building Services
Engineering Research & Technology.
Muneer, T., 2000. Windows in buildings. Oxford: Architectural Press.
NASA, 2016. EOSWEB. [Online]
Available at: https://eosweb.larc.nasa.gov/cgi-
bin/sse/retscreen.cgi?&[email protected]&p
Nicholls, R., 2008. Green Building Bible, Volume 2. 4th ed. Llandsyul: Green Building Press.
QuelleEnergie, 2016. Pompe à chaleur géothermique. [Online]
Available at: http://www.quelleenergie.fr/economies-energie/pompe-chaleur-geothermique/
[Accessed February 2016].
Renogy, 2015. Monocrystalline v. Polycrystalline: What Difference?. [Online]
Available at: http://renogy.com/monocrystalline-v-polycrystalline-what-difference/
[Accessed December 2015].
T Muneer, T. C. G. & Kambedezis, H., 2007. Solar radiation and daylight models. 2nd 2007 ed.
s.l.:United Kingdom : MyiLibrary.
Tariq Muneer, 2000. Glazing daylight and solar radiation transmission. In: Windows in buildings.
s.l.:Oxford : Architectural Press , p. 115.
ViridianSolar, 2014. Different Types of Solar Panel. [Online]
Available at: http://www.viridiansolar.co.uk/Solar_Energy_Guide_3_2.htm
[Accessed October 2015].
Watson, D. E., 2011. Direct, Diffuse and Reflected Radiation. [Online]
Available at: http://www.ftexploring.com/solar-energy/direct-and-diffuse-radiation.htm
[Accessed December 2015].
Wikipedia, 2016. Climat de l'Isère. [Online]
Available at: https://fr.wikipedia.org/wiki/Climat_de_l%27Is%C3%A8re
[Accessed February 2016].
Wikipedia, 2016. List of thermal conductivities. [Online]
Available at: https://en.wikipedia.org/wiki/List_of_thermal_conductivities
[Accessed December 2015].
78
7 Appendix A – House Solar Gains and Heat Losses
HOURS January February March April May June July August September October November December
5.5 1.9 9.0 14.9 13.8 7.9
6.5 0.5 5.5 14.6 23.3 29.7 29.5 20.9 12.2
7.5 11.6 10.2 43.8 40.9 44.3 45.6 46.7 46.9 46.5 39.7 3.6
8.5 129.1 89.6 95.6 78.8 73.4 74.0 80.1 87.6 96.6 84.7 79.3 11.5
9.5 120.0 138.9 150.1 121.8 109.2 106.3 118.6 134.9 149.9 130.3 117.3 114.1
10.5 127.3 177.2 193.4 157.7 140.8 135.6 153.1 175.1 192.6 165.9 148.1 143.1
11.5 133.1 198.0 216.8 177.7 159.1 152.7 173.0 197.6 215.9 185.2 165.4 159.9
12.5 133.1 197.9 216.7 177.7 159.0 152.7 173.0 197.7 216.0 185.3 165.5 160.0
13.5 127.1 176.9 193.1 157.5 140.7 135.6 153.2 175.3 192.9 166.2 148.4 143.2
14.5 119.6 138.4 149.7 121.5 109.0 106.2 118.7 135.2 150.3 130.7 117.8 114.2
15.5 128.1 89.0 95.1 78.5 73.3 74.0 80.2 87.9 97.0 85.2 80.0 11.5
16.5 11.5 10.2 43.4 40.8 44.3 45.6 46.7 47.0 46.9 40.4 3.6
17.5 0.5 5.5 14.6 23.4 29.7 29.5 20.9 11.4
18.5 1.9 9.1 14.9 13.7 7.9
GAINS 1.7 2.0 2.3 1.9 1.8 1.8 2.0 2.1 2.3 1.9 1.6 1.4
(kWh/day)
HOURS January February March April May June July August September October November December
5.5 1.9 90.7 134.8 148.4 8.6
6.5 0.5 5.8 114.8 138.0 167.9 185.2 166.3 124.8
7.5 12.8 10.7 134.1 148.3 168.4 191.2 210.7 195.1 158.8 101.1 3.7
8.5 147.0 119.7 160.0 165.7 181.7 198.3 218.1 207.2 177.3 120.2 93.6 11.5
9.5 88.9 119.6 156.5 158.7 170.3 181.3 198.3 191.5 168.6 119.0 90.7 80.8
10.5 59.1 93.1 121.8 126.0 135.5 142.8 153.9 147.9 130.1 93.6 70.2 61.2
11.5 38.5 61.4 81.9 90.6 99.8 105.5 110.6 103.3 88.1 63.6 46.4 39.2
12.5 29.0 48.2 66.9 75.4 84.9 91.2 96.6 88.5 72.9 50.3 35.4 29.3
13.5 26.1 42.8 60.7 69.6 79.3 85.7 90.5 82.1 66.7 45.1 30.9 25.1
14.5 20.8 33.0 49.3 59.1 68.7 75.3 79.0 70.4 55.3 35.6 22.8 17.6
15.5 13.7 20.5 34.6 45.1 54.8 61.4 63.8 54.9 40.4 23.5 12.7 11.6
16.5 12.7 10.7 18.8 29.7 39.1 45.6 46.7 37.8 24.3 10.6 3.7
17.5 0.5 5.8 14.6 23.4 29.7 29.5 20.9 9.0
18.5 1.9 9.1 14.9 13.7 7.9
GAINS 0.4 0.4 0.7 0.9 1.1 1.2 1.3 1.1 0.9 0.5 0.3 0.2
(kWh/day)
Hourly solar gains in W/ 𝑚² - Aspect=180 (South), Windows area=1.6 𝑚²
Hourly solar gains in W/ 𝑚² - Aspect=90 (East), Window area=0.8 𝑚²
Walls Door + windows Roof Ventilation Thermal bridges (5%) Floor (9%)
January 21.1% 16.2% 20.9% 27.8% 5.0% 9.0%
February 21.1% 16.1% 20.9% 27.9% 5.0% 9.0%
March 21.1% 16.0% 20.8% 28.1% 5.0% 9.0%
April 21.0% 15.9% 20.7% 28.4% 5.0% 9.0%
May 20.9% 15.5% 20.5% 29.1% 5.0% 9.0%
June 20.4% 15.0% 20.1% 30.5% 5.0% 9.0%
July - - - - - -
August - - - - - -
September 20.7% 15.3% 20.4% 29.6% 5.0% 9.0%
October 20.9% 15.5% 20.7% 28.8% 5.0% 9.0%
November 21.0% 16.0% 20.8% 28.1% 5.0% 9.0%
December 21.1% 16.1% 20.9% 27.9% 5.0% 9.0%
Heat losses (%)
Heat loss repartition, by month (%)
79
8 Appendix B – Solar Thermal System Elements (1)
Circulating pump Clearline collector V30 Specifications
Solar electric cylinder
80
9 Appendix C - Solar Thermal System Elements (2)
Expansion vessel
Pre-insulated pipe
Controller and temperature sensors
81
10 Appendix D – GSHP Circuit Elements (1)
Ground Source Heat Pump
GSHP fluid Circulating pump
82
11 Appendix E - GSHP Circuit Elements (2)
Water cylinder 210 L
Underground pipe coil 250 m
83
12 Appendix F – PV Systems Elements (1)
PV16/250 Specifications Battery RBS1860 specifications
84
13 Appendix G – PV Systems Elements (2)
Maximum Power Point tracker
Inverter specifications
85
14 Appendix E – Biowatt Energie Mail Exchange