Solarification of IIT Roorkee Campus Page 81 6. Solar Steam Cooking System Fig 6.1: The Solar steam cooking system at Shantikunj, Hardwar 6.1 Introduction In most of the cooking activities, LPG or diesel is used as a fuel. The cost of these fuels is rising daily and their contribution to global warming is increasing at a rapid rate too. The labour and time involved in conventional cooking is immense and there is a chance of fouling up of the food due to direct or indirect contact with the fuel. The solution to these problems is in the form of a solar steam cooking system which uses the thermal energy of the sun to produce steam for cooking. The Solar Steam Cooking systems developed for community cooking application provide an eco-friendly solution to the increasing energy demand of the community kitchen/cooking in India. The Government is also providing a number of subsidies to enhance the popularity of such systems. The cooker is useful for residential schools, institutional kitchens (viz. industrial and administrative canteens), religious ashrams, hotels, hospitals, police and armed forces kitchens, etc. As described in chapter x, the basic technology involves concentration of sun’s rays on to a smaller area for achieving higher temperatures for faster cooking. The community solar cookers are concentrating dishes of aperture area of the order of 10 square meters or higher are useful for steam cooking applications for very large kitchens such as a hostel mess. In this chapter the technical details of and the benefits expected to accrue from the installation of a solar steam generation system in the messes of IIT Roorkee are discussed fuels are rising day by day beyond prohibitive limits. In addition to this, generation of carbon dioxide is unavoidable. In fact it will
Solarization of IIT Roorkee Campus6. Solar Steam Cooking
System
Fig 6.1: The Solar steam cooking system at Shantikunj,
Hardwar
6.1 Introduction
In most of the cooking activities, LPG or diesel is used as a fuel.
The cost of these fuels is rising daily and their contribution to
global warming is increasing at a rapid rate too. The labour and
time involved in conventional cooking is immense and there is a
chance of fouling up of the food due to direct or indirect contact
with the fuel. The solution to these problems is in the form of a
solar steam cooking system which uses the thermal energy of the sun
to produce steam for cooking. The Solar Steam Cooking systems
developed for community cooking application provide an eco-friendly
solution to the increasing energy demand of the community
kitchen/cooking in India. The Government is also providing a number
of subsidies to enhance the popularity of such systems. The cooker
is useful for residential schools, institutional kitchens (viz.
industrial and administrative canteens), religious ashrams, hotels,
hospitals, police and armed forces kitchens, etc. As described in
chapter x, the basic technology involves concentration of sun’s
rays on to a smaller area for achieving higher temperatures for
faster cooking. The community solar cookers are concentrating
dishes of aperture area of the order of 10 square meters or higher
are useful for steam cooking applications for very large kitchens
such as a hostel mess. In this chapter the technical details of and
the benefits expected to accrue from the installation of a solar
steam generation system in the messes of IIT Roorkee are discussed
fuels are rising day by day beyond prohibitive limits. In addition
to this, generation of carbon dioxide is unavoidable. In fact it
will
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6.2 Solar Steam Generation System: Salient features
Besides the benefits they bestow on the environment, solar steam
cooking systems are advantageous in many other ways as well:
• Cooking possible in the kitchen- Since it is an indirect cooking
system with the steam produced outside and brought into the kitchen
via standard piping, there is no requirement of cooking in the sun.
The existing kitchen can be used with very few modifications.
• No need to stand in the heat of the sun- The cooking can be done
in the existing kitchen, with only the apparatus outside.
• Once set in the morning, tracks sun automatically- One operator
is required to align the dishes once in the morning.
• Cooks faster than other types of solar cookers- The very high
temperatures produced result in faster cooking as compared to other
solar cooking technologies.
• User friendly, easy to move and clean • Safe to operate and
durable • Effectively useful from one hour after sunrise to one
hour before sunset • Uses highly reflective surface to increase
efficiency • Useful for urban, rural as well as tribal areas for
use in community kitchen, hostels,
hotels, remote camps and the like- These features make it ideal for
usage in the messes of IIT Roorkee.
6.3 Distribution of students dining in messes
Fig 6.2: Mess student distribution
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The total number of students dining in the messes is 5405 and they
take three meals per day. Out of these three meals, two (lunch and
dinner) involve preparation of items like rice, daal, vegetables
which can be cooked/are being cooked using steam cooking
technology. In the breakfast, boiling of milk is possible using
steam.
Fig 6.3: Mess cooking area
Some messes have hot water heater which produces hot water for dish
washing purposes. This very same purpose can be achieved via the
excess steam which is produced by the steam cooking system. Also,
most messes already have steam boilers for preparation of rice etc.
and they can serve the purpose of backup boilers in the steam
cooking arrangement.
The messes, in general have large shade free area available on
their roofs.
Fig 6.4: Ganga mess rooftop
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From the above mentioned site data and the large mess utilization
it is clearly observed that there is huge potential for application
of solar steam cooking technology in the messes of IIT Roorkee.
Especially with the subsidies available and the potential for
savings, it becomes a financially viable proposition.
6.4 Technical Specifications
Fig 6.5: Relevant components of system
The solar steam generating system comprises of automatically
tracked parabolic concentrators with steam header/ tank assemblies
and receivers, steam pipelines, feed water piping, steel structures
and civil works, instrumentation like pressure gauges and
temperature indicators, steam separators, steam traps etc. It is
hooked up with conventional steam backup system, viz. LPG based
cooking system. The details of the major components of the system
are as below: i) Parabolic concentrators- Each parabolic
concentrator of the system has a reflector frame fitted with
reflecting mirrors, rotating support and a stand. The concentrators
are installed in such a way that they focus sunlight on to the
receivers while in operation which will be attached to a steam
header/ tank. The concentrators may be installed in series and
parallel combination connected to different steam headers/ tanks
depending on the size of the system. The tracking arrangement is
such that once adjusted in the morning with the help of drive
motor, the
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concentrators automatically track the sun at least in one direction
i.e. in East-West, thereby focusing all the sun light exactly on
the receivers connected to the header. ii) Steam header assembly
& instrumentation- Each steam header assembly connected to a
group of concentrators consists of a steam header/ tank connected
to receiver (circular in shape), pressure reducing station, steam
and feel water pipelines and necessary valves. The receivers work
on thermo- siphon principle and the water stored in the header is
slowly converted into steam when the system is put into operation.
The pressure reducing station is designed to reduce the pressure of
steam generated in the header from 10 Kg/cm2 to 1-2 Kg/cm 2 so as
to ensure safety of the user while using the steam. The system
pipelines, receivers and steam header are insulated with glass
wool/ rock wool covered by aluminium cladding to minimize heat
losses. A Feed water tank of suitable capacity, instrumentation
e.g. pressure gauze and water level and temperature indicators,
level controller, safety valves, steam separators is installed with
the system. iii) Support structure and civil work- Necessary steel
structure is provided to support steam header/ tank, stands for
concentrators, steam and feed water pipelines, pressure reducing
valves, feed water tank etc. iv) Steam backup system (if not
existing earlier)- The steam backup system comprises of
conventional boiler, utensils ,water softening plant, pumps,
necessary instrumentation & valves etc. 6.5 Methodology The
survey of all the messes was carried out for evaluating the
suitability of the rooftop area for rooftop installation. Both the
rooftop and the kitchen area were measured and evaluated in order
to determine the piping route, the placement of the collectors and
other components like feed water tanks and cooking vessels. The
instrumentation and the details of the piping are not shown on the
map. Only the basic pipeline path terminating in the cooking area
is shown.
The strategy used to decide the number of collectors to be placed
is based on the fact that due to the heavy mess utilization, all of
the steam produced can be utilized; if not for cooking, then as hot
water for dish washing. Hence the idea is to place as many
collectors as can be accommodated on the rooftop.
6.5.1 System performance criteria
The performance of Solar System depends upon the following
factors:
• Solar irradiation : The system requires a minimum average 500-600
w/m2 of solar radiation for effective operation with
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• No of days of sunlight considered per year: 300 days per year. •
Cleaning of the mirror faces is essential to prevent loss in mirror
efficiency • Shadow free area at the concentrator site. • Water
Quality: The performance of the system depends heavily on the
quality of
water. Parameters like Hardness, O2 content, pH value, Free CO2,
TDS and temperature of the water must be considered.
In order to satisfy all the performance criteria, the mess roof was
carefully scanned for shading and only the areas un-shaded by trees
and structures were considered for installation. Roorkee has close
to 300 sunny days per year and a high amount of insolation which
guarantees effective performance of the system. Besides, a
demonstration system in operation at the Shantikunj Ashram has been
very successful. Given the climatic similarity between the two
towns, the system will work effectively in Roorkee as well.
The water quality report has been obtained from a certified
authority to ascertain the quality of water. The parameters are
mentioned herewith:
6.5.2 Water Quality Report
As per the water quality report attached along with the report, the
quality of water is found good enough for the system to be
implemented unhindered. The pH is within limits and the total
hardness is well with the desired limit. Hence the system can be
installed without any issue of water damage.
6.5.3 Reflector Area requirement
Based on the specifications provided by manufacturers, the
reflector area that would fulfil the cooking needs of an average
community dining system has been obtained. It is presented for the
various messes as follows:
Mess Name Students dining in mess Reflector area required
(m2)
Ganga 567 90.7 RKB/Cautley 1531 245.0 Rajendra 800 128.0 Azad 499
79.8 Ravindra 509 81.4 Govind 606 97.0 Jawahar 642 102.7 Sarojini
251 40.2 Total 5405 864.8
Table 1.1: Reflector area requirement per mess
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6.5.4 System ground area requirement
The data for the amount of area occupied by the system components,
i.e. the concentrator, the feed water tanks, cooking vessels and
framework has been taken from the feasibility study of the steam
cooking system at Shantikunj. The details are explained in the
feasibility report (Section 6.8: Appendix).
6.6 Results
After sizing the system and carrying out the roof survey, the
layout plans for the various messes were drawn. Some of them have
been outlined below:
• DRG M-1: For the Radhakrishnan Bhawan/ Cautley mess, 12
collectors could be installed along with the required piping. The
spacing left between the collectors is adequate to prevent shading
between concentrator rows.
• DRG M-2: For the Ganga Bhawan Mess, sufficient area is available
for setup all the concentrators. The cooking vessels are placed in
the kitchen and accordingly the piping has been drawn
6.6.1 System selection
In order to optimally use the limited roof area and reduce the
number of components, it is proposed to deploy the 16m2 reflector
which makes the installation of a sleeping dish optional. The
number of concentrators required has been determined accordingly.
However, not all the concentrators required can be placed on the
roof due to area considerations. Hence, the actual number of
concentrators required is somewhat lower:
Mess Name No of concentrators to be installed (16 m2)
No of concentrators that can be actually
installed (16 m2) Ganga 7 7 RKB/Cautley 16 12 Rajendra 8 8 Azad 5 5
Ravindra 6 6 Govind 7 7 Jawahar 7 7 Sarojini 3 3
Total 58 54 Table 1.2: No. of concentrators required
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6.6.2 Energy Production
The proposed installation would produce heat energy in the form of
steam which would replace an equivalent amount of LPG. The heat
production per system is as follows:
Fig 6.6: Heat energy produced per day per system (Mcal/day)
6.6.3 LPG Savings
The usage of solar energy for cooking helps in saving a significant
amount of LPG per day. These savings, coupled with the fact that
under the JNNSM large government subsidies are available, make the
system financially feasible.
The LPG cylinders saved per day have been calculated by estimating
the amount of LPG required to produce an equivalent heat output as
above on burning. The combustion efficiency is assumed to be 85%
for LPG, with a calorific value of 11900 kCal/kg ( as specified by
Indane). A standard LPG cylinder contains 14.2 kg of LPG. The net
LPG savings per day per bhawan mess are as shown:
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Fig 6.7: LPG cylinders saved per day per bhawan
The total LPG savings achieved per day is of 12 cylinders.
6.6.4 Component List
After deciding on the number of dishes required per mess, the
detailed list of components required for the project is:
A) Parabolic dish: The various components that make up the
parabolic dish are:
• Frame assembly • Structure • Mirror • Stand • Receiver • Tracking
system • Feed water pump • Steam header with instrumentation and
control. • Automatic pump controller
Except feed water pump and tank, these components vary as per the
number of dishes installed.
B) Steam cooking vessels: The vessels required are of two types,
direct and jacketed. 2-3 of these are required per mess
C) MS piping ½”: The piping is one of the most essential components
of the system. The relevant piping includes insulation and
aluminium cladding.
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6.7 Conclusion
With savings of up to 12 cylinders per day possible, the solar
steam cooking system has the potential to save a huge amount of LPG
and thus, the country’s energy per day. Although this system
requires some maintenance, it can be easily taken care of by an
annual maintenance contract. With its tracking feature, this type
of system can use a lot of solar energy and thus is highly
efficient. Although the efficiency of the mirrors, receivers etc.
degrade with time, it can be remedied with a proper maintenance
contract as mentioned above.
Overall, with large subsidies being provided by various
governmental agencies and good savings possible, the system turn
out to be highly feasible. The complete economic analysis of the
solar steam cooking system is carried out in the chapter on
economic analysis.
6.8 Appendix: Feasibility study
In order to determine the feasibility of solar steam systems for
regular use, a feasibility study of the technology was carried out
for the system installed at Shantikunj Haridwar. The details are as
follows;
Shantikunj Feasibility Study:
To analyze the feasibility of Solar Steam Cooking implementation of
IIT Roorkee campus, an operating Steam Cooking system was studied
and analysed.
Feasibility Study Solar Steam Cooking
Location Haridwar
Total no. of dishes 10
Capacity of cooking vessel 50kg
Time taken to cook 45kg rice 20minutes
Time of aligning the dishes in the morning 8 am
Time period of full fledge operation 10 am – 6 pm
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Fig 6.8: Shantikunj rooftop
Concentrator Dish:
The concentrator dish is very large in size and consists of many
small mirror modules connected on a large frame. The dishes have to
be aligned once in the morning and then dealigned at night. The
approximate time at which the dishes are aligned at Shanti Kunj is
9am and the system starts full fledge operation by 11am. This
operation of the Concentrated Solar System continues till evening 5
– 6 pm after which the backup LPG system is used to heat the
preheated steam of the system.
No. of Dishes installed: 10
Fig. 6.9: Concentrator
Area occupied by each dish: 4m X 4m
The Receiver Module:
The receiver module contains an iron plate where the sunlight is
incident and this module is responsible for absorbing this incident
heat. The module’s iron plate has to be painted approximately once
in two to three days to maintain its high heat absorption.
Fig.6.10: Reciever
The tracking module:
The tracking module consists of an arrangement of ropes, pulleys
and motors which track the sunlight throughout the day and enable
high performance and high concentration. The dishes have to be
aligned with the sun, once in the morning and then the automatic
tracking takes over.
Fig. 6.11: Tracking Ropes
The reflectors are placed as an array and each reflector covers a
4m X 4m area on the roof top. The collector module and the steam
transfer pipe are placed at a distance of 3m from the reflector.
The reflectors need not be in one single array as observed at
Shanti Kunj and can be places as parallel arrays of 4, 3 or even a
single collector. Moreover, the water storage system and the
control systems use very less space and can be situated in shady
areas. In this case particularly, the motors used for auto-tracking
were placed in shadowy area under the dishes.
The Piping Connections:
The piping done at Shanti Kunj consisted of a large variety of
pipes, all which were highly insulated to prevent heat loss and
also to prevent burns on touching them. The diameter of the largest
pipe was measured approximately to be 60cm (0.6m).
Fig. 6.12: Piping
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The place of generation of steam and the place of consumption (the
kitchen) were located at a large distance and the piping was also
very large. Due to the good insulation the heat losses are kept
minimum.
Fig. 6.13: Piping to kitchen
The water reservoir:
As can be seen from the picture, the water reservoir did not occupy
a lot of space.
The actual dimensions of the water reservoir are:
Height = 1.3m
Diameter=1m
The cooking vessels:
The steam in used to boil water in a heat exchanger and then the
cooking vessels use this hot water. The cooking vessels have a
capacity of 50kg of rice, but Shanti Kunj kitchen uses them to cook
only 45kg at one time. The average cooking time was reported to be
20 minutes for 45kg of rice. Potato and vegetables can also be
cooked in this system.
Fig. 6.15: Steam Cooking Vessels