6. solar steam cooking system - ahec
TRANSCRIPT
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
Solarification of IIT Roorkee Campus Page 82
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
Solarification of IIT Roorkee Campus Page 83
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
Solarification of IIT Roorkee Campus Page 84
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
Solarification of IIT Roorkee Campus Page 85
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
Solarification of IIT Roorkee Campus Page 86
• 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
Solarification of IIT Roorkee Campus Page 87
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
Solarification of IIT Roorkee Campus Page 88
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:
Solarification of IIT Roorkee Campus Page 89
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.
Solarification of IIT Roorkee Campus Page 90
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
Solarification of IIT Roorkee Campus Page 91
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
Solarification of IIT Roorkee Campus Page 93
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
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
Solarification of IIT Roorkee Campus Page 82
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
Solarification of IIT Roorkee Campus Page 83
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
Solarification of IIT Roorkee Campus Page 84
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
Solarification of IIT Roorkee Campus Page 85
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
Solarification of IIT Roorkee Campus Page 86
• 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
Solarification of IIT Roorkee Campus Page 87
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
Solarification of IIT Roorkee Campus Page 88
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:
Solarification of IIT Roorkee Campus Page 89
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.
Solarification of IIT Roorkee Campus Page 90
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
Solarification of IIT Roorkee Campus Page 91
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
Solarification of IIT Roorkee Campus Page 93
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