Sunil Indora’s research while affiliated with Indian Institute of Technology Delhi and other places

A framework to estimate the potential of solar cooking for institutional level applications is presented. Using the weather data of a given location (such as solar radiation, ambient temperature, and wind speed), the proposed framework estimates the number of days in a year when solar cooking is feasible and consequently the amount of useful energy saved. Around 57% of the annual useful energy required for cooking (5475 TJ/year out of 9562 TJ/year) in the institution-types considered in this study can be met with solar energy. The adoption of solar cooking in these institution-types is expected to save 197 thousand tonnes of LPG annually. The corresponding annual amount of CO2 emissions mitigation is estimated at 592 thousand tonnes. Amongst the six institution-types considered in the study, cooking of mid-day meal (MDM) in government schools of India has the maximum potential of solar cooking. The annual potential of useful energy savings with the use of solar energy for cooking of MDM is estimated at 3881 TJ out of a gross requirement of 6960 TJ/year. The framework developed and approach used in the study can be used for assessment of potential of institutional solar cooking as well as identification of niche areas for immediate intervention in any other country as well.

A framework to estimate the extent of various incentives required to ensure financial attractiveness of institutional solar cooking is presented with typical examples from India. Incentives considered are capital subsidy/viability gap funding, accelerated depreciation, interest subsidy, and investment tax credit have been considered for three commercially available designs of solar cookers that can be used for institutional cooking (SK-23, Scheffler dish (direct), and Scheffler dish (steam)). Depending on the location, the extent of viability gap funding (VGF) for Scheffler dish (steam) solar cooking system varies from 18.7% to 66.5% of the capital cost, while the same for SK-23 and Scheffler dish (direct) varies from 8.7% to 82.9%, and 33.4%–94.5% respectively. From the government point of view, the provision of accelerated depreciation for incentivising institutional solar cooking is found to be the least cost option followed by viability gap funding, investment tax credit and interest subsidy in the order of increasing cost to the government. At locations in the cold and cloudy climatic zone of India, there is invariably a need to provide a combination of incentives (as the current provision of 30% capital subsidy is not adequate) to ensure a breakeven condition.

An assessment of the financial attractiveness of using Scheffler dish for solar steam cooking at institutional/community level in India is presented. Three sizes of institutional kitchens, i.e. small (200 persons), medium (500 persons) and large (1000 persons) have been considered. Aperture area of solar energy collection, the investment required and consequently the values of several measures of financial performance for small, medium, and large-sized Scheffler dish based institutional solar steam cooking systems have been estimated. The assessment of the annual amount of steam generation has been carried out at over thirty different locations in the country (capital city of each state of India). The annual amount of steam generated is estimated to vary between 583 and 1072 kg per m ² of the aperture area of the Scheffler dish. As expected, the financial attractiveness of the Scheffler dish based solar steam cooking system changes with the locations. The lowest values of the estimated discounted payback period are 9, 7 and 6 years respectively, for small, medium and large-sized institutional kitchens. Large-sized solar steam cooking systems are financially more attractive essentially due to the economy of scale in the capital cost of these system.

Financial appraisal of two solar cookers (SK-23 and Scheffler dish) that may be used for institutional/community cooking is presented. For each solar cooker type, three different categories in terms of performance and cost as prevailing in the market have been considered. Annual numbers of solar cooked meals and consequently the values of several measures of financial performance are estimated for three locations in India with varying climatic conditions. As per the estimates obtained in this study a SK-23 solar cooker can cook from 39% to 60% of the meals during the year while, the corresponding range for Scheffler dish based solar cooker is from 59% to 85% at these locations. The discounted payback for SK-23 varies 6.2–9.2 years while the same for Scheffler dish varies from 9.5 to 11.7 years. The financial attractiveness of SK-23 is adversely affected by its poor performance in high wind, while the relatively higher capital cost of the Scheffler direct cooker apparently makes it financially unattractive. Thus, there is an urgent need to encourage research and development on solar cookers to reduce their cost and also to improve performance.

A review on various aspects of institutional solar cooking is presented. Starting with an overview of energy requirement for cooking, the review includes cooking technologies developed for institutional solar cooking, polices and programs for their promotion and case studies reported in the literature on field level application. State of the art concentrating solar technologies suitable for institutional level cooking includes Parabolic dish, Scheffler dish and ARUN® dish. Design, construction and operational details of both direct and indirect types of concentrating solar cookers have been discussed. The case studies, mainly from India, included provide useful feedback on the experiences of using large scale institutional solar cooking systems. A Few installations of each type of solar cooker have been reviewed and major findings and observations on various aspects of the same are reported.

An assessment of the financial feasibility of using solar pre-heated water in institutional cooking applications in India is made. Use of solar heated water to reduce fuel requirement for institutional cooking applications is being proposed as the existing solar cooking options have not yet been acceptable. For example, hot water delivered by solar water heating systems (SWHS) installed in government schools can be used for cooking Mid Day Meal (MDM) to be served to school children. As an illustrative example, for 35 locations in India, spread all over the country, annual amount of useful thermal energy likely to be delivered by SWHS have been estimated using System Advisor Model (SAM) and the same has been used to estimate the annual fuel savings. Financial feasibility of the proposed approach has been assessed in terms of payback period, net present value, benefit to cost ratio and the internal rate of return of the incremental investment on SWHS. The annual amount of LPG saved varies in the range of 111 to 178 kg for a system for cooking of 100 MDM per day translating to annual LPG saving of 13200 – 21360 tonnes for about 120 million MDM beneficiary students in India. The payback period at all locations is found to be much lower than useful life of SWHS. Even with the consideration of the fact that the solar heated water would not be used on school holidays, the proposed approach of using solar pre-heated water for cooking appears to be financially attractive for all locations considered in the study.