Solar heating and cooling solutions for buildingsStephen White

July 2017

ENERGY FLAGSHIP

Solar cooling

Using solar radiation to drive a cooling process.

Displacing the use of fossil fuel derived electricity that would otherwise be used in a conventional vapour

compression airconditioner.

Solar thermal heat driving a thermal cooling process

Solar photovoltaics driving a conventional vapour

compression cooling process

Cooling Demand Matches Solar Availability

Why solar cooling? - Policy perspective

1. Reduce greenhouse gas emissions

2. Lower energy costs/ benefit the electricity system (higher load factor/ lower tariffs)

De

ma

nd

(M

W)

Time of Day

Why solar cooling? – Owner perspective

1. Reduce greenhouse gas emissions/ lower energy costs

2. Increase asset value• Access to environmentally aware (CSR)

tenants• Point of sale rating disclosure

3. Response to government policy• Compliance with minimum renewable

energy targets (development permission)• Eligibility for incentives

20102008 2011 2012 20142009

Year of Study

2013

Per

cen

tage

incr

ease

in s

ale

pri

ce f

or

gree

n b

uild

ings

co

mp

ared

wit

h c

on

ven

tio

nal

co

de

-co

mp

lian

t b

uild

ings

(%

)

-15%

-10%

0%

-20%

10%

-5%

20%

-5%

25%

35%

15%

30%

IPEEC, 2014

Mugnier, & Jakob, 2012

Solar cooling marketTota

l am

oun

t of

insta

lled

Sola

r C

oolin

g s

yste

ms in E

uro

pe &

the

Worl

d

Source: Solem Consulting / TECSOL

IEA Roadmap vision of solar heating and cooling (2012)

Solar cooling accounts for ~17% of TFE cooling in 2050

Technology Approach

ENERGY FLAGSHIP

Routes to delivering solar heat

Solar ElectricSolar Thermal

Transpired Glazed air heater Solar PVRoof cavity

Mechanical heat pump

• Split system

• DX Unit

Combi System

Thermal heat

pump

Combi-systems beget solar cooling systems?

Solar collector

panels

Thermal

storage tank

Backup

heater

Hot water

Thermally

Activated

Cooling Machine

Solar PV or solar thermal – integration and backup

Routes to delivering active solar cold

Solar ElectricSolar Thermal

Evacuated Tube Parabolic Trough Solar PVFlat Plate Parabolic Dish

Mechanical compressor driven

• Split system

• DX Unit

• Chiller

Double- effect

absorption chiller

Single- effect

absorption chiller

Rankine Cycle

Desiccant

dehumidification

Adsorption chiller

Stirling cycle

“Solar [thermal/vapour compression] hybrid” cooling?

Free (Solar?) Cooling

ENERGY FLAGSHIP

Free cooling approaches

• Economizer cycle

• Economizer cycle with direct or indirect evaporative cooling

• Night purge ventilation

• Evaporatively cooled water circulation

• Night sky radiant cooling

• Geo-exchange

Wate

rA

ir

? Sealed well insulated buildings

? Ventilated adaptive comfort

Dew point coolerGives enthalpy reduction; not just sensible - latent switch

Source: Oxycom

Extending the economy cycle season

PerthBrisbane

Dew point coolers entering the market

Implications

• Smaller temperature differentials = larger air flows

• Better suited to applications such as• Tempered air

• Underfloor cooling

• Chilled beams/ceilings (for evaporatively cooled water)

• What level of duplication of infrastructure is required for peak demand?

Solar PV Driven Cooling

ENERGY FLAGSHIP

Systems emerging on the market

Some indicative (only) information

Adapted from Mugnier and Mopty, IEA Task 53, 2016

Separate PV and AC (grid acting as buffer)

vs Connected PV and AC (off-grid/ self consumption)?

Is this “Solar Airconditioning” or ”Solar AND Airconditioning” ?

Potential benefits (beyond simple energy savings)Electricity system

benefit

100% off grid solar PV/AC with separate AC backup

• Reduced peak demand

• No reverse power flow

• Safety• Voltage

• Slow ramp rates

100% Solar PV self consumption with grid backup

• Reduced peak demand

• No reverse power flow

Solar PV self consumption with grid export/import

Reduced peak demand

Consumer benefit

Residential: • leave it permanently

on = guilt free luxuryCommercial• Solar cooling efficiency

increase at part load

I don’t need to inform my electricity utility

I don’t need to inform my electricity utility

Get full value for electricity

Disadvantages

• Wasted electricity if airconditioning is not required

• Needs batteries to manage fluctuations

Wasted electricity if airconditioning is not required

Lack of advantages

Solar thermal driven cooling

ENERGY FLAGSHIP

Solar thermal technology options (By heat source temperature)

Perf

orm

ance

Wa

ter

at

Patm

Solar thermal collector efficiency

Absorption chillers (predominantly LiBr/water)

(Mature technology, chilled water output)

ChillerCoefficient of

Performance (COP)

Required Heat

Source TemperatureAvailability

Single Stage 0.6-0.75 80-120ºC Good. Also ammonia

Two Stage 1-1.3 160-180ºC Large systems (>100kW)

Three Stage 1.6-1.8 200-240ºC limited

Broad

Carrier

Thermax York

Century

Kawasaki Shuangliang

Yazaki, Japan

(35 - 175 kW)Robur, Italy

(35 - 88 kW)

EAW, Germany

(30 - 200 kW)

AGO, Germany

(50 - 500 kW)

NH3 /water

Adsorption Chillers

Sortech (8 - 15 kW)Invensor (7 - 10 kW)

Mayekawa (50 - 350 kW)

Mitsubishi Plastics

(10,5 kW)

Bryair (35 - 1180 kW)

Desiccant dehumidification

Electric heater or Gas heater

Suitable for solar pre-heat

35°C

14g/kg

60°C

7.0 g/kg

35°C

14g/kg

56°C

21g/kg

80°C

~2

00P

a

Selection considerations

Absorption Adsorption Desiccant

Hazards Corrosive fluid Crystallization

Inert solid media Inert solid media

Performance Best COP Poor at low

temperatures

Works at lower temperature

Lower COP

Works at lower temperature

Free part load cooling ? Depends on conditions

Heat rejection

Cooling tower ? Cooling tower preferred

No cooling tower

Size/weight More compact Bulky and heavy ? Bulky but light

Maintenance Solution chemistry Cooling tower

Easy Cooling tower

Atmospheric pressure Robust

Cost Comparable with conventional (at scale)

Expensive ? Probably most economic

Co-benefits ? Ventilation

Some likely combos

Air collectors → - Heating and desiccant dehumidification

Flat plate collectors → - Desiccant or adsorption system

Evacuated tubes → - Single effect absorption chiller

Concentrating collectors → - Double effect absorption chiller

- Air cooled food refrigeration

Indicative Performance

1 unit of Sun

Driving Energy

Cold (heat)

Electric ThermalLow Efficiency

(air cooled)High Efficiency(water cooled)

Low Efficiency (single effect)

High Efficiency (double effect)

0.2 0.2 0.5 0.5

0.6 (0.8) 1.2 (1.4) 0.35 (0.85) 0.6 (1.1)

Thermal systems are ideally integrated

Large Hotel

2%

14%

1%

29%54% Air Conditioning

Lighting

Laundry

Other

Hot w ater

Large Office Buidling

13%

37%

49%1%

Air Conditioning

Lighting

Office equipment

Other

Medium Size Hospital

18%8%

15%

39%20% Air Conditioning

Lighting

Laundry

Other

Hot w ater

Cost competitiveness (example installed systems)

Neyer, Mugnier and White, 2015

Cost of energy savings compared with PV

Hotel in Madrid (3050 m2 floor area), “advanced” flat plate

collectors and single effect absorption chiller

Sensitivity to buffer tank size , collector area and chiller size

Technical Integration

ENERGY FLAGSHIP

Average Hobart diurnal profile

WinterSummer

Average Townsville diurnal profile

WinterSummer

But every day and every hour is differentStorage and/or backup required

Generic flow-sheet for matching an intermittent heat source and a variable demand for cooling

Solar

Collector

Evaporator

(+possible backup AC)

Cooling

Tower

Ten Key Principles

Principle 1: Choose applications where high annual solar utilization can be achieved

• Is there a load in the shoulder season?

• Can solar be the lead with conventional peaking?

Principle 2: Avoid using fossil fuels as a backup for single effect ab/adsorption chillers

Principle 3: Design to run the absorption chiller in long bursts

• If in doubt oversize the field not the chiller

Principle 4: Use a wet cooling tower where possible

The Key Principles (con)

Principle 5: Select solar collectors that achieve temperature even at modest radiation levels

Principle 6: Keep the process flowsheet simple and compact

Principle 7: Match storage temperature and hydraulics with the application

Principle 8: Minimise parasitic power

Principle 9: Minimise heat losses

Principle 10: Apply appropriate resources to design, monitoring and commissioning

Building Integration

ENERGY FLAGSHIP

Bolt on or fabric integrated?

• Reduced materials duplication

• Improved aesthetics

• Achieving core building functionality

• Maintaining performance

• Diverse product range

Lichtblau et al 2010

IEA Task41 categorization

Farkas, 2013

Source: Monier

Source: SOLID

And other functions

IEA Task41

Transpired air collectors

The attic- To suck or blow? That is the question

Impacts of orientation and tilt angle

Output per kW of panel purchased vs

Output per m2 floor plate area

Near horizontal panels don’t care about orientation

Precinct Integration

ENERGY FLAGSHIP

Zero Energy Precinct Example

• 151 Units

• 11kV connection

– Private network

– No backflow

• Residential demand

– 550 kVA peak demand

– 780 MWh/annum

• PV potential from available roof area

– 2740 MWh/annum

Norm

alis

ed P

ow

er

Norm

alis

ed P

ow

er

Winter

• Nett daily shortfall

• Export at midday is approximately

the same as average demand

Summer

• Nett daily surplus

• Exporting (shifting to my neighbours)

around 3 times more electricity

than average demand at midday E

xport

Needs to be transported

somewhere or stored

? More generation capacity , Add battery storage, or Shift demand

Going 100% solar electricity

Examples

ENERGY FLAGSHIP

SolaMate air heater example

BlueScope PV/T example

SW Orientation

NE Orientation

Sproul and Farschimonfared, 2016

CSIRO residential hot water, heating and cooling product

Provides cooling even when the sun is not shining

Low temperature heat source requirement

No cooling tower required (but does require water)

Positive pressurization of building

Observations: Rowes Bay operating by itself

Observations: Operating in tandem with peak smart

Around the cities

Total

solution

as isP

art

ial/hybrid c

oolin

g

Total comfort solution

(% of hours)

Large ESCO systems make economic sense

• Wide variety of reported capital cost numbers- lets say ~US$2,500 / kWcooling installed

• Even better when there is a high DHW load

United World College,

Singapore

• 1575kW single effect

absorption chiller

• 3900m2 flat plate collectors

with transparent teflon sheet

• 60m3 storage at ~88°C

• ESCO financingS.O.L.I.D

.

=2.5 m2/kW

=15 L/m2

Some absorption chiller installations in Australia

Source: ECS

District heating and cooling

Building A : 11 000 m² - offices and shops

Building B : 10 600 m² with 167 dwellings

Montpellier Heating and System net utilities => System owner

TECSOL: engineering company

Buildings situation

AXIMA : Company in charge of the works

SERM building, Montpellier (France), 2010

• 900 kW gas heating

• 700 kW chiller

System selection

Selection

- 240 m² double glazed flat plate collectors (Block A, limited by roof area)

- solar circuit in drainback mode (with water glycol + HX)

- 35 kW absorption chiller

- 1500 liter hot buffer storage tank for the chiller (Block A)

- + 10 m3 DHW storage capacity in Building B for dwellings)

Application

- Hot water preheat (all year round)

- Autonomous solar cooling (when

hot water temperature is high enough)

=6.9 m2/kW

=43 L/m2

Schematic

Hot water gives year round solar utilization

Month

Sola

r H

eat C

olle

cte

d/

DH

W H

eat D

em

and

Solar Irradiation

(kWh)

Collected solar heat

(kWh)

Solar DHW Production

(kWh)

Solar Cooling

Production (kWh)

Parasitic electricity

consumption (kWh)

Electrical Seasonal

Performance Factor* (-)

Jan-14 14,214 4,092 3,734 0 190 19.7

Feb-14 21,409 6,789 6,435 0 218 29.5

Mar-13/14 37,977 13,153 12,504 0 308 40.6

Apr-13 33,255 12,236 11,588 0 290 40.0

May-13 47,124 17,350 16,478 0 380 43.4

Jun-13 53,349 13,236 7,497 2,765 902 13.4

Jul-13 55,769 16,639 11,311 3,983 1190 13.6

Aug-13 48,656 12,467 8,628 1,970 840 14.2

Sep-13 37,744 10,513 9,316 676 554 18.9

Oct-13 24,645 8,541 7,843 0 240 32.7

Nov-13 17,309 5,133 4,789 0 220 21.8

Dec-13 15,164 4,341 3,851 0 157 24.6

TOTAL 406,616 124,490 103,974 9,394 5,489 21.5

Case study performance

TAFE commercial kitchens demonstration• Unique solar desiccant cooling design

• Flat plate/ 2-rotor desiccant cooling• Solar hot water

• Worlds largest solar desiccant cooling system • 80 kWth

• 400m2 collectors, 9000 litres

=5 m2/kW =23 L/m2

Preheating water and precooling airPre-cooled

air out

Ambient air in

Novel two wheel intercooled desiccant wheel system

Solar hot water heating contribution

• Preheating cant

heat the ring main

Solar space heating and cooling contribution

• Evaporative

cooling not

included/ valued (despite doing the

bulk of the cooling)

• Temperature not

always available

to run the DEC

Conclusion

• Solar cooling makes intuitive supply/demand sense

• It can add to the value of the building asset

• Solar PV driven systems are emerging on the market but manufacturers and electricity utilities need to work together

• A wide variety of thermal technologies and solar thermal collectors have been demonstrated but work best satisfying integrated building thermal needs

Conclusion• 10 Principles for good integration

• Year round solar utilization

• Integration with backup systems

• Good quality solar collectors

• Energy only economics are ok at large scale and for hot water lead

• Desiccant cooling has cost, maintenance and part load advantages, but is probably not well suited to providing a 100% solution (but nor would you expect a 100% solution from intermittent solar)

• But don’t forget low-cost building-integrated solar air heating options too

ENERGY TECHNOLOGY

Thank youEnergy TechnologyStephen WhiteEnergy for Buildings Manager

t +61 2 4960 6070e stephen.d.white@csiro.auw www.csiro.au/