d esign and validation of a s olar d omestic h ot w ater h eating s imulator department of...
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DESIGN AND VALIDATION OF A SOLAR DOMESTIC HOT WATER HEATING SIMULATOR
Department of Mechanical EngineeringBaylor University
Thomas Cemo
April 29, 2009
OUTLINE
Introduction
Background
Assumptions
Theory
Apparatus
Results
Conclusions
INTRODUCTION:GOALS
To accurately simulate efficiency ratings provided by the Solar Rating and Certification Corporation (SRCC).
To create a platform for testing modifications to domestic solar hot water heating systems.
BACKGROUND:DOMESTIC HOT WATER HEATING
The home is the second largest non-commercial consumer of energy, behind transportation.
14% to 25% of domestic energy is demanded by water heating.
Solar thermal water heating has a tremendous opportunity to reduce this demand.
BACKGROUND:SOLAR RATING AND CERTIFICATION
CORPORATION (SRCC)
Arab Oil Embargo of the 1970s Federal tax credits motivated a rush to hastily
install solar thermal systems. The market was flooded with poor designs and
craftsmanship.
Solar Rating and Certification Corporation (SRCC) Founded in 1980 Reassures consumers of quality products. Efficiency ratings will be used to validate our
hardware simulation.
BACKGROUND:DOUBLE TANK SYSTEMS
Double Tank System
Water is heated as it is circulated through a collector.
Energy is transferred to thermal storage and auxiliary heating if necessary.
Hot water is then drawn for domestic uses such as dishwashing.
ASSUMPTIONS: SOLAR DAY
How to accurately model the energy available during a typical day?
Standardized weather profile provided by the SRCC.
All calculations occur in an adjusted time frame known as Solar Time.
Solar Night Solar Day Solar Night
Insolation (Whr/m2)
THEORY: SOLAR ENERGY FACTOR
auxpar
del
QSEF
Qdel : Thermal energy delivered to the domestic hot water load.
Qpar : Energy required by parasitic devices such as pumps and controllers.
Qaux : Energy required by auxiliary resistive heating elements.
Average SEF:2.0 - 5.0
THEORY: QDEL DELIVERED ENERGY
Solar ‘Day’ Draw Schedule
THEORY:SOLAR FRACTION
SEF
EFSF 1
SF: Portion of hot water provided by solar energy.
EF: Energy factor for a conventional electric hot water heater (0.9).
SEF: Solar Energy Factor.
Average Solar Fractions:0.50 - 0.75
APPARATUS
Mains Chiller
Auxiliary Storage Tank
Solar Storage Tank
Solar Thermal Collector Simulator
APPARATUS: SOLAR THERMAL COLLECTOR SIMULATOR
(STCS)
Simulates thermal collector absorbing insolation during a solar day within 10% accuracy.
LabVIEW Control Software calculates the useful power from the simulated collector array.
Modified Seisco on-demand hot water heater.
Resistive heating elements deliver power to circulated water.
APPARATUS:LABVIEW CONTROL SOFTWARE
APPARATUS:LABVIEW CONTROL SOFTWARE
APPARATUS:MAINS CHILLER
Test conditions require 14°C.
Baylor water mains temperaturerange from 15°C to 22°C.
Closed loop that circulated water through 60ft of copper submerged in an ice bath.
19 gallons were cooled to 14°C in approximately 25 min.
Temperatures maintained within 0.4°C.
Pump controls
Ice bath
Chiller tank
RESULTS:DOUBLE TANK CONFIGURATION
Test SEF Difference
SRCC 3.0
Test 1 2.44 -18.6 %
Test 2 2.84 -5.5 %
Average 2.64 ± 0.043 -12 %
Solene Double Tank Drainback System
RESULTS:DOUBLE TANK CONFIGURATION
Test Parasitic (kJ) Time (hr) Auxiliary (kJ) Time (hr)
Test 1 3564 7.4 13,732 1.25
Test 2 3456 7.19 11,767 1.1
•Average Solar Fraction of 0.65•Solar Savings =30,155 kJ/day
•8.3 kWh/day•Average Electricity cost $0.13/kwh*
Yearly Savings: $388
auxpar
del
QSEF
* Average Retail Price of Electricity to Ultimate Customers by End-Use Sector, by State, EIA
RESULTS:DOUBLE TANK CONFIGURATION
Double Tank TestSolar Tank Temperatures vs. Time
30
35
40
45
50
55
60
0 5 10 15 20
Time from start of test (hr)
Tan
k T
emps
(°C
)
Tlow in
Ttop suf
Solar Day
RESULTS:DOUBLE TANK CONFIGURATION
Double Tank TestAuxiliary Tank Temperature vs. Time
40
45
50
55
60
65
0 5 10 15 20
Time From Start (hr)
Tan
k T
emp
erat
ure
(°C
)
Solar Day
CONCLUSIONS
Constructed a test platform for future research into solar domestic water heating.
Calculated accurate and repeatable results verified by SRCC data.
Test SRCC BU
Double SEF 3.0 2.64 ± 0.043 -12 %
RECOMMENDATIONS
Incorporate a Differential Temperature Controller
Utilize location specific weather data
Construct an array of thermocouples to be inserted into the tanks.
ACKNOWLEDGMENTS
Departments of Mechanical and Electrical Engineering for providing the means to continue this research.
Dr. Van Treuren, Dr. Gravagne, and Dr. Lehr
Mr. Ashley Orr and Mr. Dan Hromadka
QUESTIONS?