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Solar Thermal Technology for Rural India Rural Energy Technology Dr. Basudev Pradhan
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Page 1: Solar thermal tech pradhan

Solar Thermal Technology for Rural India

Rural Energy Technology

Dr. Basudev Pradhan

Page 2: Solar thermal tech pradhan

Solar Thermal is a clean, highly efficient means of using renewable energy from the sun to provide hot water for domestic, commercial and industrial process . Put in simple terms, if you place a container full of liquid in the garden on a sunny day, in a short time the contents of the container become warm. Solar Collectors work in much the same way, but are very more efficient.

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Classification of Solar Thermal Systems

(A) On the basis of Achievable Temperature

(i) Low Temp.T<100oC

(ii) Medium Temp100o≤ T ≤ 300oC

(iii) High TempT>300oC

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Classification of Solar Thermal Systems

(B) On the basis ofConcentration Type

ConcentratingCPT, CPC, CRS, DRS, Solar Cooker,

Parboloid

Non-Concentrating or FPC Type

FPC, Solar Pond, Basin Type Still,ETC

Imaging

CPC, DRS, Paraboloid

Non-Imaging

Solar Cooker, CRS, CPC

Line Focusing

CPT, Linear Fresnel

Point Focusing

Parboloidal Dish, Fresnel Lens

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Solar Heating Applications and Systems

Temperature Applications Systems Imaging Systems

Low Temperature

T<100oC

Water heating, Space heating,Drying, Distillation

FPC, Solar Pond, Solar StillAir Dryer

Nil

Medium Temperature

100o≤ T ≤ 300oC

Cooking, Air heating, Refrigeration and AC, Distillation

FPC, CPC, Solar Cooker, ETC, Honeycomb CSD, Linear Fresnel

Nil

High Temperature

T>300oC

Process heat, Power

CPT, Central Receiver system, Distributed Receiver System, Paraboloid

Paraboloid

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S.N. Sector Conventional Resources Used

Temperature Range

1 Household Biomass, Coal, Oil, Natural Gas

Low, Medium

2 Transportation Oil, Natural Gas --

3 Industry Coal, Oil, Natural Gas Low. Medium, High

4 Agriculture Oil, Animal Power, Biomass

Low, Medium

5 Commerce Coal, Oil, Natural Gas, Biomass

Low, Medium

Thermal Energy Utilization Sectors/Resources

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Sectors - Thermal Needs and Applications

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Household SectorBasic Needs Energy Activity Temp Range

Drinking Water Water distillation/purification Low

Food Cooking Low, Medium

Crop drying Low

Milk Pasteurization Low

Comfort Space heating Low

Water heating Low

Active space cooling and refrigeration

Medium

Passive space heating, cooling and lighting

Low

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Industry Process Temperature (◦ C)

Dairy Pressurization 60–80

Sterilization 100–120

Drying 120–180

Concentrates 60–80

Boiler feed water 60–90

Tinned food Sterilization 110–120

Pasteurization 60–80

Cooking 60–90

Bleaching 60–90

Flours and by-products Sterilization 60–80

Tea Pre-heating 80-90

Drying 110-120

Industrial Sector : Food Industry-1

Mekhilef et al, Renewable and Sustainable Energy Reviews 15 (2011) 1777–1790

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Industry Process Temperature (◦ C)

Meat Washing, sterilization 60–90

Cooking 90-100

Fish Washing, Sterlization 60-90

Drying 80-90

Beverages Washing, sterilization 60–80

Pasteurization 60–70

Industrial Sector : Food Industry-2

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Industry Process Temperature (◦ C)

Textile Bleaching, dyeing 60–90

Drying, degreasing 100–130

Dyeing 70–90

Fixing 160–180

Pressing 80-100

Paper Pulp cooking, drying 60–80

Boiler feed water 60–90

Bleaching 130–150

Industrial Sector : Paper and Textile

Mekhilef et al, Renewable and Sustainable Energy Reviews 15 (2011) 1777–1790

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Industry Process Temperature (◦ C)

Chemical Soaps 200–260

Synthetic rubber 150–200

Processing heat 120–180

Pre-heating water 60–90

Plastics Preparation 120–140

Distillation 140–150

Separation 200–220

Extrusion 140–160

Drying 180–200

Blending 120–140

Industrial Sector : Chemical Industry

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Industry Process Temperature (◦ C)

Timber by-products Thermo diffusion beams 80–100

Drying 60–100

Pre-heating water 60–90

Preparation pulp 120-170

Bricks and blocks Curing 60–140

Industrial Sector : Building Materials

Mekhilef et al, Renewable and Sustainable Energy Reviews 15 (2011) 1777–1790

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Item/Detail Process Temperature (◦ C)

Food grain Drying 80–100

Parboiling60–100

Fruit Drying 60-80

Pulp processing100-110

Sericulture Cocoon processing100

Pisciculture(Cold region) Reproduction/Growth40-50

Poultry Chick brooding Growth30-40

Plant conditioning Growth/quality40-50

Agriculture: Crop/fruit

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Solar Thermal Conversion Devices and Utilization

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Solar Thermal Collectors

Flat Plate Collector(FPC)

Spherical Parabolic Concentrating Collector

Linear Cylidrical Parabolic Concentrating Collector(CPC)

Evacuated Tubular Collector(ETC)

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Collector

SystemDetailed

Temperature

Range

FPC Flat Plate Collectors Low

Flat Plate Collectors with double glazing Medium

SP Solar Pond Low

ETC Evacuated Tubular Collectors Medium

CPC Compound Parabolic Concentrators Medium

CPT Cylindrical Parabolic Trough(linear) Medium-High

Cylindrical Parabolic Trough(Surface of revolution)

High

CRS Central Receiver System High

Solar Thermal Conversion Collectors

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Flat Plate Collector(FPC)

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How Does it Work?

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FPC It can easily achieve a temperature 60-80oC above ambient

temperature. It uses both beam and diffuse radiation. Does not require tracking. Requires little maintenance. Efficiency: ~ 45% at 80oC Applications: air heating,

water heating,industrial process heating,

passive air conditioning 15 % of all the thermal requirements are in this range*

* Mekhilef et al, Renewable and Sustainable Energy Rev. 15 (2011) 1777–1790

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FPC - Section

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Major parts of FPC A metallic flat absorber plate (cu, steel, aluminium

and having black coated( 0.5 mm to 1 mm)

Tube or channels are soldered to the absorber plate

A transparent toughened glass of 5 mm

Fibre glass insulation of thickness 2.5 cm to 8 cm

A container encloses the whole assembly in a box made metallic sheet or fibre glass

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Evacuated Tubular Collector(ETC)

Page 25: Solar thermal tech pradhan

ETC It can easily achieve a temperature 80-120oC above ambient

temperature.

It uses both beam and diffuse radiation.

Does not require tracking.

Requires little maintenance.

Mode: Heat pipe; U tube water; Integrated Collector/storage

Efficiency: ~ 55% at 80oC(for water heating)

Applications: air heating,

water heating,

industrial process heating,

passive air conditioning

27 % of all the thermal requirements are in this range*

*Mekhilef et al, Renewable and Sustainable Energy Rev. 15 (2011) 1777–1790

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ETC in heat pipe mode

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ETC in Heat-pipe Mode

Glass-Glass Evacuated tube System

Heat Pipe System

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ETC in U-tube water mode

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ETC performance

• Efficiency of ETC in heat pipe mode is better but pay back period of U-tube/water in glass is very short.

• Evacuated tube of 58 mm ED is standard with centre to centre spacing of 75 mm.

• Solar water heaters performance parameter Efficiency in terms of ratio of tank volume to collector area ratio suggests that it is highest(58%) for the ratio 75 L/m .

• Shorter tube 1800mm performed better than longer 2100mm due to stagnation at the bottom.

• Angle has little influence on the thermal performance i.e. can be installed vertically as well.

Zhang et al, Energy Conversion and Management, 2014

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Concentrating Collector

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Compound Parabolic Concentrating (CPC) collector

θc

• Concentration Ratio• Highest for the given

Acceptance Angle• Needs less tracking

• Temperature ~150oC

• Limitation:CR~10

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Cylindrical Parabolic Trough (CPT) collectors

Receiver tube

Glass cover

Receiver detail

Receiver

Sun rays

Tracking mechanism

Parabola

Schematic

Page 33: Solar thermal tech pradhan

Cylindrical Parabolic Trough (CPT) collectors

• Concetration Ratio ~10-80

• Needs one axis continuous tracking based on mounting

• Higher the concentration ratio more is the tracking requirement

• Temp~400oCSun rays

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Parabolic Trough

The largest ‘solar thermal-electric’ installation of its kind in the world,the Luz project in California’s Mojave Desert, has a peak output of some350 megawatts and occupies several square kilometers of land

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Solar Bowl Concentrator

•HIGHEST ACHIEVABLE TEMP=260oC

•AUROVILLE (Pondicherry)

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Fresnel lens collector

Made of an acrylic plastic sheet, flat on one side, fine longitudinal grooves on the other sideAngle of grooves~ line focusCR ~ 10 to 80Temp~ 150 to 400o C

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Solar Water Heater

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Solar Water Heater

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Solar Water Heat

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Solar Water Heating

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A thermosyphon system

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A double-cycle system with forced circulation with a conventional boilerfor back-up heating

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A solar district heating system

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Solar Water Heater(Forced Circulation)

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Industrial Solar Thermal Process Heat System(Forced Circulation)

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Solar Cooking

Page 47: Solar thermal tech pradhan

Benefits of Solar Cooking Consumes no fuels/wood

No loss of trees & habitat

Trees sequester carbon

Generates no air pollution

Generates no greenhouse gases

Produces no smoke Cooking smoke kills over 1.6

million people each year, mostly women & children, according to a recent report

Eliminates fire dangers

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More Benefits of Solar Cooking Eliminates work

No daily search for firewood 2 Billion people rely on

wood for cooking fuel!

No risks to women and children

Frees time for other activities

No need to stir food

Helps to liberate women

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More Benefits of Solar Cooking• Cooks foods slowly and

thoroughly• Preserves nutrients • Foods will not burn• Pots are easy to clean;

less clean water is needed

• Use for canning vegetables

• Use for dried fruit• Kill insects in dry grains

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Solar CookingHow Long Does it Take?

Vegetables: 1.5 hrs

Rice/wheat: 1.5-2 hrs

Beans: 2-3 hrs

Meats: 1-3 hrs

Bread: 1-1.5 hrs

Page 51: Solar thermal tech pradhan

SOLAR COOKERS

Three types of cookers

1. Box type: for boiling type cooking

2. Concentrator type: for boiling, frying,

baking, roasting

3. Advanced type: for indoor cooking

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Box-type

Boiling type cooking

Low temperature cooking

Nutrition value maintained

Page 53: Solar thermal tech pradhan

Box type Double walled box with insulator in between. The inner

box is metallic and is inclined at 45 deg and coated blackon top. Which cooking pots (coated black outside) are keptover the inner box. Booster mirror.

50 cm x 50 cm x 14 cm

Covered with two clear window glasses(70cm x 70 cm)fixed in a frame hinged on one side of the box.

Over 10 lakh such cookers distributed in India.

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Box type cooker

Page 55: Solar thermal tech pradhan

Concentrating type

Boiling, frying possible Out of various types, the

paraboloid concentratorsolar cooker(PCC) can meetthat demand by deliveringpower up to 0.6kW whichcan boil 3-4 litres of water inabout half an hour.

CONCENTRATOR TYPE

0.70 m2 area700 W

Page 56: Solar thermal tech pradhan

SCHEFFLER COOKER FOR COMMUNITY COOKING AT SHIRDI

Also at Tirupati Balajee Temple, Tamilnadu and PrajapitaBrhmakumari, Mount Abu, Gujarat

Page 57: Solar thermal tech pradhan

Solar Power Tower

In 1995 Solar One was converted into Solar Two, by adding a second ringof 108 larger 95 m² (1,000 ft²) heliostats around the existing Solar One, totaling 1926 heliostats with a total area of 82,750 m² (891,000 ft²)

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Solar Dish

Stirling Energy Systems‘ solar dish technology is the world’s most efficientdevice for the conversion of solar energy to grid-delivered electricity,nearly twice as efficient as any alternative solar technology.

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Solar Pond

Top layer at ambient temp, whereas bottom layer temp 60°- 85°C

surface convection zone

2.concentration gradient zone

3. Lower convective zone

Artificially designed pond filled with salty water maintaining a define concentration gradient is called a “Solar Pond”

Three basic zones: 1. surface convective zone(SCZ)(thickness 10-20 cm), 2. Non-convective zone(NCZ) (half the depth of the pond, as insulator layer)3. Lower convective zone(LCZ)(nearly same as NCZ, constant temp. and conc.

Page 61: Solar thermal tech pradhan

Salt Gradient Solar Pond1. There are 3 distinct layers of water in the pond:

a) The top SCZ layer, which has a low salt content. b) The bottom LCZ/SZ layer , which has a high salt content. c) An intermediate insulating NCZ/GZ layer with a salt gradient,

which establishes a density gradient that prevents heat exchange by natural convection

2. Solar collector-cum-storage system

3. Average storage temperature ~ 80oC

4. Large collection and storage capacity, Efficiency ~ 14%

5. The lowest thermal energy cost amongst all solar & conventional technologies.

6. Applications: water purification, water heating, space heating, refrigeration, power

7. Drawbacks: low temperature, instability, environmental problems

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ElPasoSolar Pond, Texas

The El Paso Solar Pond project is a research, development, and demonstration project initiated by the University of Texas at El Paso in 1983. It has operated since May 1986 and has successfully shown that process heat, electricity, and fresh water can be produced in the southwestern United States using solar pond technology. An organic Rankine-cycle engine generator was installed on site in 1986, making it the first in the U.S. to generate grid connected power, producing up to 70kW. Most of this power has been delivered to Bruce Foods Corporation for peak power shaving. This demonstrates one of the primary benefits of solar ponds: power on demand --even at night or after long periods of cloudy weather.

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Solar pond Largest solar pond: Bet ha Arava in Israel, area 250,000m2

generate 5 Mwe of electrical power with an organic fluid working rankine cycle principle

India 1st solar pond: area 1200 m2 was built at Central salt Research Institute, Bhavnagar in 1973,

6000 m2 , built at Bhuj(Gujarat), 2nd largest in world, it provides daily 90,000 litres of hot water at 80c as process heat for can sterilization, -temp 99C, capable of generating 150 kW of power

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The Solar Pond

BIRD’S EYE VIEWS

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Storage Zone temperature

Reflectivity=0.3

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This picture of the Solar pond at Pyramid Hill (near Kerang in Northern Victoria) shows the mesh of pipes running down the wall of the pond. These run across the bottom of the pond and up the other side. Fresh water (or radiator coolant) is circulated through them, and is heated by the saline pond water. This hot fluid is then used to heat glass houses, boil refrigerant in a rankine engine to make electricity, or (in the case of Pyramid Hill) used to heat air to flash dry gourmet salt products.

(The plastic rings visible on the surface of the water are used to reduce water movement caused by wind)

Page 67: Solar thermal tech pradhan

Passive Solar

Passive Solar is accommodated in the design of some homes where living rooms are south facing with large windows and floors and sometimes walls have a large thermal mass.

While it is necessary to use the solar to heat in winter overheating in summer has to be avoided, this is normally done by having a roof overhang which blocks the high summer sun but not the low winter sun.

While it can provide some free heat it doesn’t supply hot water and there are design constraints.

The key is designing a passive solar home to best take advantage of your local climate.

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Passive Solar

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Solar crop drying

Air inside is heated and natural air circulation starts

Temperature inside ranges from 50 to 75C

Drying time for products like: dates, grapes, apricots, Cashew nuts and chillies from 2 to 4 days

Large scale drying: seasoning of timber, corn drying, Tea processing, tobacco curing, fish and fruit drying

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Solar crop drying

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Solar kilnsHeating and drying of products on a large scale, like tea, corn, fruits, timber, etc is done using solar energy.

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Solar kilns

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Solar Distillation Arid, semiarid and costal area

Salt works, Bhavnagar, capacity: 1000 m3/day, Evaporating area: 350 m2 for drinking water for workers in salt works sea water

Page 74: Solar thermal tech pradhan

World Water Resources

Salt Water

Fresh Water The Worlds Water

97% Sea Water

3% Fresh Water

California Coastline

http://www.windycityart.com/californiawallpaper/ocean%20wallpaper.jpg

Solar Powered Desalination

Page 75: Solar thermal tech pradhan

World Fresh Water Resources

Ice

Ground Water

Riparian Areas

The Worlds Fresh

Water

77% Ice

22% Ground Water

1% Rivers, Lakes and

Streams

Solar Powered Desalination

Page 76: Solar thermal tech pradhan

Desalination

The separation and removal of

ions, salts and other dissolved

solids from water.

Heat Based

Membrane Based

Evaporation pool (Saudi Arabia)

http://www.cea.fr/gb/publications/Clefs44/an-clefs44/clefs4481a.html

Solar Desalination

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Water Distillation Process that removes impurities & contaminants

How?

Heat water to point of vaporization

Water vapor condenses on cooler surfaces

Condensate runs off into collection bin

Page 78: Solar thermal tech pradhan

Patent & Periodical Research Results

Beneficial Ideas Troughs

Water height < 2 cm

Mirrors

Beneficial Information Asymmetrical superior to

other designs

30% more efficient

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Market SearchRainmaker 550TM

•Unit Cost - $479.00•Estimated cost $400-$600

•Built & supplied by aid organization

El Paso Solar Energy Association (EPSEA) Aid Project

•Not currently in production

•Very low output

The Water Cone®

Page 81: Solar thermal tech pradhan

Looking Towards The Future

Due to the impending global water scarcity crisis,

many human rights organizations are funding

research on desalination in order to provide

people with adequate drinking water.

Everyone need water

http://news.bbc.co.uk