The heater saves about 17 MJ of energy per day. There are 300 clear days in a year at Jodhpur and, therefore, solar water heater can be used for 300 days per year, accordingly, calculations have been made of energy savings per year in relation to different fuels, and payback periods have been computed. The economic evaluation and payback periods have been computed by considering interest rate = 10%; maintenance cost = 5% of cost of the solar heater, and inflation rate in fuel prices and maintenance cost = 5 % per year. Cost of the heater is Rs. 8,000.00 (Euro 1.0 = Rs

60.0) . The cash flow of the heater with respect to different fuels has been carried out and it has been found that the cash flow is maximum with respect to fuel coal and minimum with respect to kerosene. The payback period is least, i. e. 1.42 yr, with respect to coal and maximum, i. e. 3.72 yr, with respect to kerosene (The cost of kerosene is highly subsidised). The payback periods are in increasing order with respect to fuel: coal, electricity, firewood, LPG, and kerosene. The estimated life of this solar water heater is more than 15 years. The shorter payback periods suggests that the use of ICS solar water heater is economical. The use of integrated collector storage solar water heater will conserve substantial amounts of commercial and non-commercial fuels, which are consumed for obtaining hot water.

4. Conclusion

Integrated collector storage (ICS) type solar water heater can provide 100 litres of hot water at an average temperature of 57.3o C that can be retained to 43.0o C till next day morning when cold water temperature was 17.0o C. The efficiency of the heater has been found to be 61.3%. The heater saves about 17 MJ of energy per day. Cost of the heater is Rs. 8,000.00 (Euro 1.0 = Rs

60.0) . The cash flow of the heater with respect to different fuels has been carried out and it has been found that the cash flow is maximum with respect to fuel coal and minimum with respect to kerosene. The payback period is least, i. e. 1.42 yr, with respect to coal and maximum, i. e. 3.72 yr, with respect to kerosene (The cost of kerosene is highly subsidised). The payback periods are in increasing order with respect to fuel: coal, electricity, firewood, LPG, and kerosene. The estimated life of this solar water heater is more than 15 years. The shorter payback periods suggests that the use of ICS solar water heater is economical. The use of integrated collector storage solar water heater will conserve substantial amounts of commercial and non-commercial fuels, which are consumed for obtaining hot water.

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