study of medium temperature solar thermal applications
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Solar EnergyTRANSCRIPT
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Review Paper
Study of Medium Temperature Solar Thermal Applications
Authors:
1Parimal S. Bhambare*, 2Dr. G. V. Parishwad
Address For correspondence:
1Mechanical Engineering Department, MIT Academy of Engineering, Alandi(D), Pune
2Mechanical Engineering Department, College of Engineering, Pune
Abstract— Solar energy is widely used for a variety of
process heat and electricity generation applications. It is
essential to apply solar energy for a wide variety of
applications and provide energy solutions by modifying the
energy proportion, improving energy stability, increasing energy sustainability, conversion reduction and hence enhance
the system efficiency. In the work presented here, a brief
study of a few medium temperature solar thermal applications
up to 2400C pertaining to domestic and industrial applications
has been considered. Typical applications in the range
included here are water heating, air drying and dehydration,
refrigeration and air conditioning, steam generation system
and solar cookers.
A brief description about the solar thermal technology utilised,
fundamentals and applications in industry has been presented
here.
Keywords — Medium temperature, concentrator, collector,
process heating.
I. INTRODUCTION
Solar thermal energy is used as process heat for different
domestic and industrial applications [1,2] in medium and
medium to high temperature ranges. These applications
includes: hot water supply, desalination, sterilization,
pasteurization, drying, space heating and cooling,
refrigeration, distillation, washing and cleaning and
polymerization. All these applications lies in temperature range between 60 to 2800C [3]. Solar thermal collectors are
used for harnessing this solar energy. These collectors are
special type of heat exchangers, which absorb the solar
radiations, and convert it to heat which is further transferred to
the fluid flowing through the collector. These are of two types:
concentrating or sun tracking (Single and two axis) and non-
concentrating or stationery type (Refer Table 1). A non-
concentrating collector has the same area for intercepting and
for absorbing solar radiation, whereas a sun-tracking concentrating solar collector usually has concave reflecting
surfaces to intercept and focus the sun’s beam radiation to a
smaller receiving area, thereby increasing the radiation flux. A
detailed review of these collectors is presented by Soterius
Kaliogirou, 2004 [4]. Non-concentrating or stationery
collectors are suitable for low (Flat Plate, FPC and Advanced
Flat Plate Collector, AFP) to medium (Evacuated tube, ETC
and Compound Parabolic, CPC) temperature applications
while concentrating type are suitable for medium (Parabolic
trough (PTC), Fresnel, Scheffler and Cylindrical trough) to
high temperature (Paraboloid and Heliostat) applications as
they produce higher temperature [4, 5]. This paper presents a comprehensive review of the current
status of utilization of solar energy in industrial and domestic
applications. TABLE I Type of solar collectors [3]
Motion Collector Type Absorber
Type
Concentration
Ratio
Indicative
Temperature
Range
Stationary Flat Plate Collectors (FPC) Flat 1 30-80
Evacuated Tube Collector (ETC) Flat 1 50-200
Compound parabolic collector (CPC) Tubular 1-5 60-240
Single-axis
tracking
Linear Fresnel reflector (LFR) Tubular 10-40 60-250
Parabolic trough collector (PTC) Tubular 15-45 60-300
Cylindrical trough collector (CTC) Tubular 10-50 60-300
Two-axes
tracking
Parabolic dish reflector (PDR) Tubular 100-1000 100-500
Heliostat field collector (HFC) Tubular 100-1500 150-2000
Note: Concentration ratio is defined as the aperture area divided by the receiver/absorber
area of the collector
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Fig. 1 shows the optimum collector area for different type of
solar collectors with demand temperature ranges.
Fig. 1 Optimum collector area for different collectors and demand
temperatures [3]
II. SOLAR THERMAL CONVERSION SYSTEM
A Solar thermal conversion system can be of direct or
indirect type. Direct heating system heats up the heat transfer
fluid (HTF) utilizing solar irradiation, which is further to the
application as process heat. HTF forms the working fluid for
the system. On the contrary an indirect system has two
working fluids used in the system. As shown in Fig.1, a
typical indirect heating system consists of mainly five major components namely, solar collector, HTF storage tank, boiler,
pump for circulating the HTF and a heat engine to convert
heat to mechanical energy [4, 6]. The efficiency of a solar
thermal conversion system is about 70% when compared to a
solar electrical direct conversion system which has an
efficiency of 17% [7].
Fig. 2 Schematic of Indirect Solar Thermal Conversion System [4]
Thus solar thermal conversion system plays a very
important role in domestic as well as industrial sector [7].
System shown in Fig. 2 is used for producing power from
solar energy. For process heat applications boiler and the heat engine will be replaced by the respective application system.
III. INDUSTRIAL ENERGY SYSTEM
An Industrial system composed of four major components
namely: power supply, production plant, energy recovery and
cooling systems [6, 8]. Fig. 3 shows the block diagram of the
industrial energy system. Power supply provides energy to the
system with use of either electrical, gas, coal or gas. This
energy is utilized to run different subsystems, controller units,
switches, etc. in the system for its operation. Solar thermal
energy can be utilized directly as a source of energy, partly or
completely, for running a process in the system.
Fig. 3 Block diagram of typical industrial energy system [6, 8]
IV. SOLAR THERMAL APPLICATIONS
Solar thermal systems not only harness solar irradiations
but also store and provide, heat to HTF (usually air or water)
used in domestic and industrial applications. Table II gives an
overview of solar energy applications, system technologies
and type of systems commonly used in industry.
Industry utilizes fossil fuels for satisfying their thermal
energy requirements partially or completely. About 13% of
thermal industrial applications require low temperatures
thermal energy up to 1000C, 27% up to 2000C and the
remaining applications need high temperature in steel, glass
and ceramic industry [6]. Table III shows few of potential
industrial processes and the required temperatures for their operations.
Industrial energy analysis shows that solar thermal energy
has enormous applications in low (i.e. 20–2000C), medium
and medium-high (i.e. 80–2400C) temperature levels [3].
Almost all industrial processes require heat in some parts of
their processes. Most common applications for solar thermal
energy used in industry are the solar water heaters, solar
dryers, space heating and cooling systems and water
desalination.
With solar thermal energy replacing the fossil fuels for
industrial processes not only reduces dependency on conventional fuels but also minimizes greenhouse emissions
such as CO2, SO2, NOx [8]. Nevertheless, there are some
challenges for integration of solar heat into a wide variety of
industrial processes due to the periodic, dilute and variable
nature of solar irradiation [9].
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TABLE II Solar energy applications, system technologies and type of
systems commonly used in industry [3]
Solar Energy
applications
Solar system technology Type of system
SWH Thermo syphon systems Passive
Integrated collector storage Passive
Direct circulation Active
Indirect water heating systems Active
Air systems Active
Space heating and
cooling
Space heating and service hot water Active
Air systems Active
Water systems Active
Heat pump systems Active
Absorption systems Active
Adsorption systems Active
Mechanical systems Active
Solar refrigeration Adsorption units Active
Absorption units Active
Industrial heat
demand process
Industrial air and water systems Active
Steam generation Active
Solar desalination Solar stills Passive
Multi stage flash (MSF) Active
Multi effect boiling (MEF) Active
Vapor compression Active
Solar thermal power
systems
Parabolic trough collector systems Active
Parabolic tower systems Active
Parabolic dish systems Active
Solar furnaces Active
Solar chemistry systems Active
All solar thermal applications in industry can be classified
in following manner [6], 1. Hot water or steam demand process
2. Drying and dehydration process
3. Preheating
4. Concentration
5. Pasturization and sterilization
6. Washing and cleaning
7. Chemical reactions
8. Industrial space heating
9. Textile
10. Food
11. Building 12. Plastic
13. Chemistry
14. Business establishment
A. Solar Water Heating (SWH) System
SWH system provides an effective technology for
converting solar energy into thermal energy.
Flat plate collectors are the central component of any solar
water heating system. The efficiency of the system depends on
the performance of the flat plate collector.
TABLE III Heat demand in industries with temperature ranges [6]
Industry
Process
Temperature (oC)
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
Textile Bleaching, dyeing 60-90
Drying, degreasing 100-130
Dyeing 70-90
Fixing 160-180
Pressing 80-100
Paper Cooking, drying 60-80
Boiler feed water 60-90
Bleaching 130-150
Chemical Soaps 200-250
Synthetic rubber 150-200
Processing heat 120-180
Pre-heating water 60-90
Meat Washing, sterilization 60-90
Cooking 90-100
Beverages Washing, sterilization 60-80
Pasteurization 60-70
Flours and by-products Sterilization 60-80
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
Plastics Preparation 120-140
Distillation 140-150
Separation 200-220
Extension 140-160
Drying 180-200
Blending 120-140
Hence all the research in SWH is focussed on performance
improvement of flat plate collectors [7]. The flat plate
collector absorbs solar radiations and converts it into heat
energy. This heat is then absorbed by HTF flowing through
the tubes of the collector. This heat can be then stored or used
directly.
In solar water heating systems, potable water can either be
heated directly in the collector (direct systems) or indirectly
by a heat transfer fluid that is heated in the collector, passes through a heat exchanger to transfer its heat to the domestic or
service water (indirect systems). Fig. 5 and Fig. 6 show both
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the systems [3]. The heat transfer fluid is transported either
naturally (passive systems) or by forced circulation (active
systems). Natural circulation occurs by natural convection
(thermosyphoning), whereas for the forced circulation systems pumps or fans are used. Except for thermosyphon and
integrated collector storage (ICS) systems, which need no
control, solar domestic and service hot water systems are
controlled using differential thermostats. Fig. 4 shows a
typical SWH system [3].
Five types of solar energy systems can be used to heat
domestic and service hot water: thermosyphon, ICS, direct
circulation, indirect, and air. The first two are called passive
systems as no pump is employed, whereas the others are
called active systems because a pump or fan is employed in
order to circulate the fluid [4].
Most of the industries use low pressure hot water for different applications below 1000C depending on their heat
requirements. When temperatures above 1000C is required
pressurized system is required which makes system cost to
increase. For medium temperature applications (above 1000C)
mineral oils are used. However, higher cost, tendency of
cracking and oxidation are few issues associated with such
systems [9].
Fig. 4 Block diagram of SWH system [5]
SWH systems are used in textile industries to supply hot
water up to 800C for dyeing, bleaching and washing purposes
[6]. Built in storage type solar water heaters are introduced in
Pakistan textile industries’ saving about 17.13 MJ of fossil
fuel energy and subsequently improving the performance [10].
Balaji Foods and Feeds Industry from India installed a
1MW SWH system with thermal energy storage system for getting about 11000 litre/day of hot water for an egg powder
making plant.
The process consists of washing, pasteurizing, fermenting
and maintaining a room at 550C. The temperature requirement
of hot water varies between 40 to 800C at different stages of
process.
Fig. 5 Direct circulation SWH system, DT: Differential Thermometer [4]
Fig. 6 Indirect circulation SWH system, DT: Differential Thermometer [4]
The system saved about 261 kL of furnace oil per year. The
system saved environment from emissions gasses viz., 9.45
tons of SO2, 675 tons of CO2, and 562.5 tons of CO produced
from burning of furnace oil annually [12]. The system is
shown in Fig. 9.
Fig. 7 Solar-oil integrated heating plant, S: storage tank, C: solar collector
bank [11]
SWH systems supply hot water for washing and cleaning of bottles in bottle washing plant. Fig. 8 shows a process layout
of the plant with temperature ranges [8].
Active SWH systems has been used in dairy industries for
washing and cleaning, pasteurization, boiler feed water (60–
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850C), sterilization (130–1500C) and even for drying milk to
produce powder. In the production, milk and whey are spray-
dried in huge towers with air, which is heated from 1200C to
1800C [3, 13 &14]. Fig. 10 shows the layout out of SWH system for dairy application.
Domestic SWH systems are used for supplying hot water
for washing clothes, dishwashing, bathing and other cleaning
processes with temperature up to 650C.
Fig. 8 System layout of bottle washing plant [8]
Fig. 8 System layout of bottle washing plant [8]
Fig. 9 Control system layout, Balaji Foods and Feeds Industry, India [12]
India holds about 3.53 million square metres of SWH
systems are installed till June 2010 as per MNRE statistics [15]. Compared to world total SWH installations in 2005 was
about 2.1% of world installations and India has way to go
ahead in this area [16].
Fig. 10 Dairy plant with SWH [13]
B. Solar Air Drying and Dehydration
Drying (or dewatering) is a simple process of excess water
(moisture) removal from a natural or industrial product in order to reach the standard specification moisture content. It is
an energy intensive operation. Moisture content of foodstuff is
around 25–80%, but generally for agricultural products it is
around 70% [17, V Belesolis]. Moisture content of the food
stuff is reduced to increase its longer shelf life. Another case
of drying (or dewatering) is the total removal of moisture until
food has no moisture at all. Dehydrated food, when ready to
use, is re-watered and almost regains its initial conditions.
Convective drying, i.e. drying by flowing heated air
circulating either over the upper side, bottom side or both, or
across its mass is the widest among drying methods used
worldwide. Hot air heats up the product and conveys released moisture to atmosphere.
Two basic moisture transfer mechanisms are involved in
drying [17]:
1. Migration of moisture from the mass inside to the
surface.
2. Transfer of the moisture from the surface to the
surrounding air, in the form of water vapour.
Agricultural products drying using solar energy is the oldest
method used by mankind for preserving them. Generally these
methods can be classified into two categories:
(a) Direct, or open-air sun drying, the direct exposure to the sun.
(b) Indirect solar drying or convective solar drying.
Temperature is one of the major factor that affect taste,
colour, flavour, texture or nutritional values of the product.
Few products require pre-treatment before solar drying to
keep their flavour and texture.
Drying rate is an important factor for agricultural and other
food products drying. Fig. 11 shows the drying rate curve for
agricultural products. This shows three phases of drying: AB
is the time spent to heat up the material until drying
temperature is attained, BC is the constant-rate drying, CE the
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falling rate drying where mass flow of moisture from interior
is decreased continuously. C is the critical point where surface
is not any more saturated and the falling rate period starts. In
point E there is still moisture inside the product, moisture content movement takes place slowly by diffusion and drying
can stop e.g. at point D when the final moisture content is
reached [17].
Fig. 11 Drying rate curve for phase I, II and III [17]
Direct or open air solar drying technique is used for
millennia by mankind for preserving food and agricultural
products. This is a simple technique with few major
disadvantages such as uncontrolled and slow rate of operation,
environmental and weather condition dependency,
contamination, dusting, fermentation, attacks by birds and
insects and other unfavourable conditions. On the other hand
indirect air heating has only disadvantage as higher initial cost. It involves some thermal energy collecting devices and
dryers of special techniques. Higher drying rate, controlled
drying, increased productivity; no losses at all in terms of
quality are the few advantages of the technique to mention
[17].
Temperature plays important role in solar drying processes.
Average temperature of agricultural product drying is around
600C but it may reach to about 800C for a few. Table IV
shows drying data before and after solar drying for few
agricultural and food products with drying air temperature
[18].
Table IV Drying data for few agricultural products before and after solar
drying [18]
Product Moisture Percent (wb) Drying Air
Temperature (oC) Initial Final
Bananas 80 15 70
Barley 18-20 11-13 40-82
Beets 75-85 10-14 -
Cardamom 80 10 45-50
Cassava 62 17 70
Chilies 90 20 35-40
Coffee seeds 65 11 45-50
Copra 75 5 35-40
Com 28-32 10-13 43-82
Cotton 25-35 5-7 --
French beans 70 5 75
Garlic 80 4 55
Grapes 74-78 18 50-60
Green forages 80-90 10-14 --
Hay 30-60 12-16 35-45
Longan 75 20 --
Medicinal plants 85 11 35-50
Oats 20-25 12-13 43-82
Onions 80-85 8 50
Peanuts 45-50 13 35
Pepper 80 10 55
Potato 75-85 10-14 70
Pyrethrum 70 10-13 --
Rice 25 12 43
Rye 16-20 11-13 --
Sorghum 30-35 10-13 43-82
Soybeans 20-25 11 61-67
Spinach leaves 80 10 --
Sweet potato 75 7 75
Tea 75 5 50
Virgin Tobacco 85 12 35-70
Wheat 18-20 11-14 43-82
Solar dryers can be classified into different categories. Fig.
12 shows the different types [19]. Literature reviewed shows
numerous types of solar dryers have been designed and
implemented for drying of agricultural and food drying
applications. A brief review of them has been presented by Arun Mujumdar [18] and A.A. El-Sebaii et.al [19].
Fig. 12 Classification of solar dryer [17]
Solar energy for wastewater sludge drying is another area
of application for solar drying. Both direct and indirect
methods of solar drying are used for the process. Fig. 13
shows the schematic of solar assisted wastewater sludge dryer
[20].
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Fig. 13 Schematic of covered solar assisted wastewater sludge dryer [20]
A silk cocoon solar assisted drying has been presented by
Panna Lal Singh [21]. The optimum temperature for the
process is about 60-800C. The tenacity of the silk thread
obtained for solar dried cocoon and electrical dried cocoon
were about 0.77 N and 0.75 N respectively. The NPV (net
present value) of solar dryer is found to be more stable as
against the escalation rate in electricity as compared to the
same for electrical dryer. Fig. 14 shows the schematic of the
system.
Industries which involve drying process usually use hot air
or gas with a temperature range between 1400C and 2200C. Solar thermal systems can be integrated with conventional
energy supplies in an appropriate way to meet the system
requirements. Heat storage seems to be necessary when
system is required to work in the periods of day when there is
no irradiation [3].
Fig. 14 Schematic of forced convection solar assisted silk cocoon dryer [20]
C. Solar Refrigeration and Air Conditioning
With solar thermal energy absorption, adsorption, solid and
liquid desiccant and solar-electrical technologies are used for solar refrigeration and air conditioning system. The main
advantages of solar cooling systems concern the reduction of
peak loads for electricity utilities, the use of zero ozone
depletion impact refrigerants, the decreased primary energy
consumption and decreased global warming impact [22]
though reduction of green house gases up to 50% [23].
Absorption refrigeration systems are adopted most
frequently for solar cooling over other systems. It requires
very low or no electrical input and for the same cooling
capacity, the physical dimensions of an absorption
refrigeration system are usually smaller than that of an
adsorption refrigeration system due to the high heat and mass transfer coefficient of the absorbent. In addition, the fluidity of
the absorbent gives greater flexibility in realizing a more
compact and/or efficient system [24]. It was counted that
about 59% of the solar cooling systems in Europe were solar
absorption cooling systems. In China, almost all the large-
scale solar cooling demonstration projects during the last
twenty years were based upon absorption systems [22].
The most usual combinations of fluids include lithium
bromide-water (LiBr–H2O) where water vapour is the
refrigerant and ammonia–water (NH3–H2O) systems where
ammonia is the refrigerant. Fig. 15 shows the basic principle of operation for absorption refrigeration system.
The NH3–H2O system is more complicated than the LiBr–
H2O system. The NH3–H2O system requires generator
temperatures in the range of 125–1700C with air-cooled
absorber and condenser and 95–1200C when water-cooling is
used. The coefficient of performance (COP), which is defined
as the ratio of the cooling effect to the heat input, is between
0.6 and 0.7 [4]. The LiBr–H2O system operates at a generator
Fig.15 Basic principle of absorption refrigeration system [4]
Temperature in the range of 70–950C with water used as a
coolant in the absorber and condenser and has COP higher
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than the NH3–H2O systems. The COP of this system is
between 0.6 and 0.8. A disadvantage of the LiBr–H2O systems
is that their evaporator cannot operate at temperatures much
below 50C since the refrigerant is water vapour. Commercially available chillers for air conditioning systems, use LiBr-H2O
absorption systems with hot water or steam as the heat source.
In market two types of chillers are available, the single and
double effect. Single effect chillers operate with pressurized
hot water temperature ranging from 80 to 1500C. The COP of
the system varies little with heat source. On the other hand
double effect chillers operate with higher temperature of heat
source which ranges from 155-2050C. COP of double effect
chillers is higher and it is about 0.9-1.2 [4]. Fig. 16 shows a
single-effect absorption cooling system
Fig. 16 Single-effect absorption cooling system[22]
Storing cool energy during sunshine hours in a cool thermal
energy storage tank, either in a sensible heat form or in a
latent heat using Cool Thermal Energy Storage (CTES) is
used in industries for process cooling, food preservation and
building air conditioning systems [25]. Fig. 18 shows the solar
absorption chiller system with storage tank.
Compared to absorption, adsorption refrigeration system
shows advantages like no distillation (NH3-H2O system),
corrosion or crystallization (Li-Br system) problem, lower equipment cost and more effective when lower grade energy
such as solar energy is used. Zhang et al. [26] presented a
simulation study of silica gel-water solar adsorption
refrigeration system using MATLAB Simulink as tool. Fig. 19
Fig. 17 Solar absorption chiller with storage tank [25]
shows the structure of silica gel-water adsorption chiller
system. Hot water temperature is in the range of about 40-
850C but below 1000C to prevent degradation of silica gel.
Fig. 18 Structure of silica gel-water adsorption chiller [26]
Fig. 19 Solar assisted air conditioning system [27]
Solar assisted air conditioning systems generally based on
solar absorption refrigeration. Sabina et al. [27] from their
performance evaluation study shown that integrating chilled
water storage tanks with the solar assisted air conditioning
system it is possible to save 30% of water consumption, 20%
of electrical consumption and about 1.7 tons of CO2
throughout the summer period. Schematic of the system is
shown in Fig. 19.
A variety of solar collectors are used in the solar
refrigeration system. Flat plate collectors are sufficient to
achieve temperatures below 1000C. But for temperatures above 1000C evacuated tube collectors, compound parabolic
collectors or concentrating collectors are used. Table V shows
the details of the collectors, storage method and applications
for the solar refrigeration systems.
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Table V Stages and options in solar cooling technologies [25] Source Conversion Thermal
storage
(hot
energy)
Production
of cool
energy
Thermal
storage
(cool
energy)
Applications
Sun Solar Thermal
1. Flat plate
collector
2. Evacuated
tube collector
3. Concentrated
collector
1. Sensible
2. Latent
3. Thermo-
Chemical
1. Absorption
2. Adsorption
3. Desiccant
4. Ejector
1. Sensible
2. Latent
3. Thermo-
Chemical
1. Air conditioning
( i) office
(ii) Hotel
(iii) Building
(iv) Laboratory
2. Food
preservation
(i) Vegetables
(ii) Fruits
(iii) Meat and Fish
3. Process
industries
(i) Dairy
(ii) Pharmaceutical
(iii) Chemical
Solar PV
(electrical)
1. Vapor
Compression
2. Thermo-
electric
D. Solar Steam Generation Systems
Low temperature is used in industrial applications,
sterilization, and for powering desalination evaporations.
Parabolic trough collectors (PTC) are mainly employed for
solar steam generation. Three concepts are used to produce
solar steam namely, the steam flash, In-situ or direct and
unfired boiler. In steam flash method, pressurized hot water from collector is flashed in separate vessel to produce steam.
In direct or in situ method two phase flow is passed in the
collector to produce steam. Unfired boiler system uses heat
transfer fluid which passes through the collector, is transferred
to an unfired boiler where steam is generated by heat
exchange to water [4]. Figs. 20, 21 and 22 shows the
schematic of above systems.
Fig. 20 Schematic of steam flash system [4]
E. Solar Cookers
Solar cooker is an age old technology used worldwide for
cooking food. Principally solar cookers and ovens absorb solar
energy and convert it to heat which is captured inside an
enclosed area. This absorbed heat is used for cooking or
baking various kinds of food. In solar cookers internal box
temperatures can be achieved up to 3000C. Solar cookers
Fig. 21 Schematic of Direct or in situ steam generation system [4]
Fig. 22 Schematic of unfired boiler steam generation system [4]
come in many shapes and sizes, etc., but all cookers trap heat
in some form of insulated compartment [28, 29]. In most of
these designs the sun actually strikes the food for cooking.
Fig. 23 Classification of solar cookers [29]
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As shown in Fig.23 solar cookers are broadly classified into
solar cookers with storage and without storage. Solar cookers
without storage are further classified into direct and indirect
solar cookers depending upon heat transfer mechanism to the cooking pot. Direct type make use of solar energy directly in
cooking process while indirect type uses heat transfer fluid to
transfer heat from collector to cooking pot [29].
Direct type cookers are broadly classified into box type and
concentrating type cookers. Fig. 24 summarises different types
of box type cookers while Fig. 25 summarises different types
of concentrating type solar cookers.
Fig. 24 Box type cooker: (a) without reflector, (b) with single reflector, (c)
with double reflector, (d) with three reflectors (e) with four reflectors, (f) with
eight reflector [29]
Fig. 25 Concentrating type cooker: (a) panel cooker, (b) funnel cooker, (c)
spherical reflector, (d) parabolic reflector, (e) Fresnel concentrator and (f)
cylindro-parabolic concentrator [29].
In indirect type solar cookers, heat transfer fluid is being
used to collect heat and transfer it to the cooking pot. Solar cookers with flat plate collector, evacuated tube collector and
concentrating type collector are commercially available
cookers under this category. The various types of indirect type
solar cookers are shown in Fig. 25.
Solar cookers with thermal storage use thermal energy storage
material to store thermal energy. This stored heat can be used
to cook the food in case of cloudy environment or cooking
indoors or cooking off sunshine hours. Both sensible and
latent heat storage materials are used for storing the thermal
energy. Engine oil, vegetable oil or sand, granular carbon are
some of the common thermal energy storage material used for
sensible heat storage. While acetamide, stearic acid, acetanilide, coconut oil, polyethylene, salt hydrate, etc. are the
examples of few latent heat storage material or phase change
materials (PCM) used in solar cookers for thermal energy
storage [28, 29].
Fig. 26 Indirect type solar cooker: (a) with flat plate collector, (b) with
evacuated tube collector, (c) parabolic concentrators at Tirumala Tirupathi
Devasthanam and (d) spherical reflectors at Auroville [29].
V. CONCLUSION
A brief overview of different solar thermal application in
medium temperature applications has been presented here to
elaborate the extent of the applicability of solar thermal
energy to industrial applications. Solar heat for industrial
processes has a great potential to curb the demand for
conventional energies which reduce our dependence on
imported fuels and to reduce CO2 emissions. However, the
overall efficiency depends on the proper integration of the
different systems and appropriate design of the solar
concentrators/collectors. Efforts in the direction of improvement in the efficiencies of
the solar collecting systems such as reducing the top loss
coefficient by introducing aerofoil design shape for glass
covers for SWH systems, system design with minimum
number of components, utilization of less energy intensive
materials for manufacturing of the system, etc. should be
employed to make the system more cost effective (reducing
pay-back period) and environmental friendly in terms of
reduction in terms of CO2 emissions in order to penetrate in
the industries.
System design engineers, manufacturers, solution providers,
service engineers and material providers should consider solar installations as a sustainable energy development. Besides,
government should encourage utilisation of solar thermal
International Journal of Applied Research and Studies (iJARS)
ISSN: 2278-9480 Volume 2, Issue 5 (May - 2013)
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systems in industries through their policies commensurate
with its large potential.
REFERENCES
[1] F. Kreith, R Davenport and J. Feustel, “Status Review and Prospectus
for Solar Industrial Process Heat (SIPH)”, Journal of Solar
Engineering, Nov 1983, Vol. 105, pp. 385-400.
[2] A report on “Solar Industrial Process Heat”, European Solar Thermal
Federation, August 2006.
[3] Kalogirou S., “The potential of solar industrial process heat
applications”, Applied Energy, 2003, 76(4), pp. 337–61.
[4] Kalogirou Soteris A., “Solar thermal collectors and applications”,
Progress in Energy and Combustion Science, 2004, 30(3), pp. 231–95.
[5] A. Munir, O. Hensel and W. Scheffler, “Design principle and
calculations of a Scheffler fixed focus concentrator for medium
temperature applications”, Solar Energy, 84 (2010), pp. 1490–1502.
[6] S. Mekhilef, R. Saidur and A. Safari, “A review on solar energy use in
industries”, Renewable and Sustainable Energy Reviews, 15 (2011),
pp. 1777–1790.
[7] S. Jaisankar, J. Ananth, S. Thulasic, S.T. Jayasuthakar and K.N.
Sheeba, “A comprehensive review on solar water heaters”, Renewable
and Sustainable Energy Reviews, 15 (2011), pp. 3045– 3050.
[8] Hans Schnitzer, Christoph Brunner and Gernot Gwehenberger,
“Minimizing greenhouse gas emissions through the application of solar
thermal energy in industrial processes”, Journal of Cleaner Production,
15 (2007), pp. 1271-1286.
[9] Kulkarni Govind N, Kedare Shireesh B and Bandyopadhyay Santanu.
“Design of solar thermal systems utilizing pressurized hot water
storage for industrial applications”, Solar Energy, 2008, 82(8), pp.
686–99.
[10] Muneer T, Maubleu S and Asif M., “Prospects of solar water heating
for textile industry in Pakistan”, Renewable and Sustainable Energy
Reviews, 2006, 10(1), pp. 1–23.
[11] D. Proctor and R. N. Morse, “Solar Energy for the Australian food
industry”, Solar Energy, 1977(19), pp. 63-77.
[12] J. Nagaraju, S.S. Garud, K. Ashok Kumar and M. Ramakrishna Rao,
“1 MWth Industrial solar hot water system”, Solar Energy, 1999, 66(6),
pp. 491-497.
[13] José Antonio Quijera, María González Alriols and Jalel Labidi,
“Integration of a solar thermal system in a dairy process”, Renewable
Energy, 36 (2011), pp. 1843-1853.
[14] Michaelis Karagiorgas and Aristotelis Botzios-Valaskakis, A report on
Solar systems applications in dairy industry, CRES.
[15] Morapakala Srinivas, “Domestic solar hot water systems:
Developments, evaluations and essentials for “viability” with a special
reference to India”, Renewable and Sustainable Energy Reviews, 15
(2011), pp. 3850–3861.
[16] S.C. Bhattacharya and Chinmoy Jana, “Renewable energy in India:
Historical developments and prospects”, Energy, 34 (2009), pp. 981–
991.
[17] V. Belessiotis and E. Delyannis, “Solar drying”, Solar Energy, 85
(2011), pp. 1665–1691.
[18] Arun S. Mujumdar, “Handbook of Industrial Drying”, Third edition,
Taylor and Francis, 2006.
[19] A.A. El-Sebaii and S.M. Shalaby, “Solar drying of agricultural
products: A review”, Renewable and Sustainable Energy Reviews, 16
(2012), pp. 37– 43.
[20] Lyes Bennamoun, “Solar drying of wastewater sludge: A review”,
Renewable and Sustainable Energy Reviews, 16 (2012), pp. 1061–
1073.
[21] Panna Lal Singh, “Silk cocoon drying in forced convection type solar
dryer”, Applied Energy 88 (2011), pp. 1720–1726.
[22] X. Q. Zhai, M. Qu, Yue. Li and R.Z. Wang, “A review for research and
new design options of solar absorption cooling systems”, Renewable
and Sustainable Energy Reviews, 15 (2011), pp. 4416– 4423.
[23] N. Molero-Villar, J.M. Cejudo-Lopez, F. Domınguez-Munoz, and A.
Carrillo-Andre´s, “A comparison of solar absorption system
configurations”, Solar Energy, 86 (2012), pp. 242–252.
[24] S.M. Xu, X.D. Huang and R. Du, “An investigation of the solar
powered absorption refrigeration system with advanced energy storage
technology”, Solar Energy, 85 (2011), pp. 1794–1804.
[25] L.A. Chidambarama, A.S. Ramanab, G. Kamaraja and R. Velraj,
“Review of solar cooling methods and thermal storage options”,
Renewable and Sustainable Energy Reviews, 15 (2011), pp. 3220–
3228.
[26] G. Zhang, D.C. Wang, J.P. Zhang, Y.P. Han and Wanchao Sun,
“Simulation of operating characteristics of the silica gel–water
adsorption chiller powered by solar energy”, Solar Energy, 85 (2011),
pp. 1469–1478.
[27] Sabina Rosiek and Francisco Javier Batlles Garrido, “Performance
evaluation of solar-assisted air-conditioning system with chilled water
storage (CIESOL building)”, Energy Conversion and Management, 55
(2012), pp. 81–92.
[28] Abhishek Saxena, Varun, S.P. Pandey and G. Srivastav, A
thermodynamic review on solar box type cookers, Renewable and
Sustainable Energy Reviews, 15 (2011), pp. 3301– 3318
[29] R.M. Muthusivagami, R. Velraj *, R. Sethumadhavan, Solar cookers
with and without thermal storage—A review, Renewable and
Sustainable Energy Reviews, 14 (2010), pp. 691–701.
*Authors Copy