So lar C o o l ing

Tec hno lo g ies The challenge of off-grid cooling

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TYPES OF SOLAR COOLING

Solar Energy

Electrical Energy Photovoltaic

Peltier cooler Vapor compression cooler

Thermal energy Solar collector

Open systems (air conditioning)

Desiccant evaporative cooling (DEC)

Closed systems (cold water)

Liquid sorbent

Absorption Water + LiBr

Ammonia + Water

Solid sorbent

Adsorption

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SOLAR POWER – PHOTOVOLTAIC

• Photovoltaic module: converts sunlight

to electricity

• Pros:

• Electricity can be used for many

things (even producing hot water)

• Cons:

• Low efficiency (below 20%)

• Electricity stored in expensive and

short-lived batteries

• Get stolen often

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http://www.solar-wind.co.uk/pv_solar_panels.html

SOLAR POWER – SOLAR COLLECTOR

• Solar collector: uses sunlight to heat water

• Regular Flat Plate collector (FP): 50 – 70 °C

• High performance FP: 70 – 90 °C

• Evacuated Tube Collector: 90 – 150 °C

• Pros:

• High efficiency (up to 80%)

• Hot water can be stored easily

• Cons:

• Only produces hot water

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http://www.apricus.com/flat-plate-solar-

collectors-3

http://www.tlcp.co.uk/products/solar/evacuated-tube-

solar-collectors.html

COEFFICIENT OF PERFORMANCE

Vapor

Compression Absorption

LiBr + H2O Absorption

H2O + Ammonia Adsorption

Cooling temperature > -80 °C > 6 °C > -30 °C > 6 °C

COP 1 – 5 0.6 – 0.8 0.3 – 0.7 0.5 – 0.7

PER - off-grid on-grid (Germany)

0.2 – 0.8 0.4 – 2.1

0.4 – 0.6 1.2 – 1.6

0.2 – 0.5 0.6 – 1.4

0.4 – 0.5 1.0 – 1.4

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C o n d e n s e r

E v a p o r a t o r

VAPOR COMPRESSION

REFRIGERATION

Q absorbed

Cold Storage

Wcompressor

Throttle Valve

Vapor Compression

↓P

↑P

Q rejected Warm Environment

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VAPOR COMPRESSION

REFRIGERATION

• Components: evaporator, condenser, throttle valve, compressor

• Refrigerants: PFC, HFC, ammonia, CO2, hydrocarbons

• Pros:

• High COP

• Plug & play with electrical grid

• Cons:

• Difficult to use without stable electrical power supply

• Complex recycling

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C o n d e n s e r

E v a p o r a t o r

ADSORPTION COOLING

Q absorbed

Cold Storage

Throttle Valve

Adsorption

Cycle

↓P G e n e r a t o r /

A d s o r b e r

Q out

Q in

Q rejected Warm Environment

↑P

↓P

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ADSORPTION COOLING

• Components: evaporator, condenser, throttle valve, at least 1 sorber

• Refrigerants: water, ammonia, ethanol, methanol

• Pros:

• Simple designs possible

• Lowest electrical energy consumption (down to zero)

• Works with heat (warm water, gas, electricity)

• Lowest driving temperatures

• Cons:

• Oscillating cooling capacity

• Lower COP than compression and water absorption cycles

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C o n d e n s e r

E v a p o r a t o r

ABSORPTION COOLING

Q absorbed

Cold Storage

Wpump

Throttle Valve

Absorption

Cycle

↓P

G e n e r a t o r

A b s o r b e r

To solar

collector

Q in

↑

↓

Q rejected Warm Environment

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L i B r / H 2 O L i t h i u m b r o m i d e

Tin = 75 – 100 °C

Tout = 25 - 35 °C

Tchilled = 6 – 20 °C

N H 3 / H 2 O A m m o n i a

Tin = 75 – 150 °C

Tout = 25 - 50 °C

Tchilled = -30 – +20 °C

Solar Collectors Evacuated Tube Collector 90 – 150°C High Performance FP 70 – 90 °C Regular Flat Plate 50 – 70 °C

WORKING FLUIDS

ABSORPTION COOLING

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ABSORPTION COOLING

• Components: evaporator, condenser, 2 throttle valves; at least 1 absorber, 1

desorber, 1 pump

• Refrigerants: water/LiBr, ammonia

• Pros:

• High thermal COP (LiBr/water)

• Low electrical energy consumption

• Works with heat (warm water, gas , electricity)

• Cons:

• Low COP (water/ammonia)

• Very complex especially using water/ammonia

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OBJECTIVE

P r o v i d e s o l u t i o n s f o r p e o p l e a f f e c t e d b y c l i m a t e c h a n g e

Current project: solar thermal air conditioning system used for

preserving vegetables

14 World Resources Institute: http://chartsbin.com/view/1030

IMPACT

Post harvest losses

• Affects food sovereignty

• Economic losses for farmers

• Ecological footprint

¼ o f g l o b a l c u l t i v a t i o n a r e a i s l o s t

1.3 billion ton. of food

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https://www.scoopwhoop.com/The-Problem-Of-Food-Wastage-In-India

CAUSES OF POST HARVEST LOSSES

• Lack of refrigeration facilities

• High running costs

• Unreliable or non existent grid

connection in rural areas

P o s t h a r v e s t l o s s e s i n I n d i a

u p t o 4 0 %

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LOCATION

Location: West Bengal, India.

Problematic:

• Only 6% of harvested vegetables are

refrigerated

• Growth rate of 70%

• Unreliable electricity grid

• Interest in regenerative solutions

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PARTNERS

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EXPERIENCE IN INDIA

Meeting with partner organization Shiksha Niketan 19

EXPERIENCE IN INDIA

Interview with the local farmers 20

EXPERIENCE IN INDIA

Interview with locals at the market 21

EXPERIENCE IN INDIA

Road conditions from farms to local market 22

EXPERIENCE IN INDIA

Visit to the Faculty of Agricultural Engineering in West Bengal 23

EXPERIENCE IN INDIA

Meeting with potential suppliers 24

Traditional market in India 25

MODULAR SYSTEM

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• Solar thermal air conditioning system

• Cold storage facility • Off-grid system • Low running costs

ADVANTAGES OF SOLAR COOLING

• Not depending on electrical grid

• Heat used for food post-processing

• Heat recovery processes

• Storage

• Storage tank vs. battery

• Less electrical energy requirements

• Compressor vs. pump

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Any Questions?

Thank You!

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ABSORPTION CYCLE

Steam

Steam

Strong

Solution

Weak Solution

Pump Pump

Solar Collectors

Harvest Cooling

Re-cooling

Vacuum

Condenser

Evaporator

Absorber

LiBr + H2O

Generator

Solution Heat

Exchanger

Pure LiBr