Transcript
Solar Thermal Technology for Rural India
Rural Energy Technology
Dr. Basudev 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.
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
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
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
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
Sectors - Thermal Needs and Applications
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
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
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
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
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
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
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
Solar Thermal Conversion Devices and Utilization
Solar Thermal Collectors
Flat Plate Collector(FPC)
Spherical Parabolic Concentrating Collector
Linear Cylidrical Parabolic Concentrating Collector(CPC)
Evacuated Tubular Collector(ETC)
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
Flat Plate Collector(FPC)
How Does it Work?
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
FPC - Section
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
Evacuated Tubular Collector(ETC)
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
ETC in heat pipe mode
ETC in Heat-pipe Mode
Glass-Glass Evacuated tube System
Heat Pipe System
ETC in U-tube water mode
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
Concentrating Collector
Compound Parabolic Concentrating (CPC) collector
θc
• Concentration Ratio• Highest for the given
Acceptance Angle• Needs less tracking
• Temperature ~150oC
• Limitation:CR~10
Cylindrical Parabolic Trough (CPT) collectors
Receiver tube
Glass cover
Receiver detail
Receiver
Sun rays
Tracking mechanism
Parabola
Schematic
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
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
Solar Bowl Concentrator
•HIGHEST ACHIEVABLE TEMP=260oC
•AUROVILLE (Pondicherry)
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
Solar Water Heater
Solar Water Heater
Solar Water Heat
Solar Water Heating
A thermosyphon system
A double-cycle system with forced circulation with a conventional boilerfor back-up heating
A solar district heating system
Solar Water Heater(Forced Circulation)
Industrial Solar Thermal Process Heat System(Forced Circulation)
Solar Cooking
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
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
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
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
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
Box-type
Boiling type cooking
Low temperature cooking
Nutrition value maintained
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.
Box type cooker
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
SCHEFFLER COOKER FOR COMMUNITY COOKING AT SHIRDI
Also at Tirupati Balajee Temple, Tamilnadu and PrajapitaBrhmakumari, Mount Abu, Gujarat
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)
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.
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.
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
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.
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
The Solar Pond
BIRD’S EYE VIEWS
Storage Zone temperature
Reflectivity=0.3
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)
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.
Passive Solar
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
Solar crop drying
Solar kilnsHeating and drying of products on a large scale, like tea, corn, fruits, timber, etc is done using solar energy.
Solar kilns
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
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
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
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
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
Patent & Periodical Research Results
Beneficial Ideas Troughs
Water height < 2 cm
Mirrors
Beneficial Information Asymmetrical superior to
other designs
30% more efficient
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®
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
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