Computer aided design and economic analysis of a solar water heating system

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Domestic water heating is important for sanitation in urban African households. Currently, the common sources of energy for water heating are grid electricity, gas and biomass form of firewood and charcoal). Solar water heating can greatly supplement energy required for domestic water heating. Solar energy is a free and environmentally friendly renewable energy resource. This thesis has dealt with a computer aided design of a solar water heating system based on heating load, weather conditions and economic scenarios of the location where it is going to be installed A review of solar water heating technology was made, and mathematical equations for sizing and computing thermal and economic performance were generated. From the mathematical equations generated, a programme was coded in Matlab to design and perform system’s long-term thermal and economic performance The programme uses f-chart correlation method, and P1 and P2 method to compute thermal performance and optimum collector size, respectively while the economic performance is given in terms of fuel savings, solar savings, operating costs, life cycle solar savings and payback period. The programme was used to design the solar water heating system for the College of Engineering Guesthouse of Kwame Nkrumah University of Science and Technology as a case study. Dynamic performance of the designed system was simulated using the TRNSYS software. The Guesthouse has an annual heating load of 62 GJ. The programme gives a collector area of 24.367 mm2 with modules connected in parallel and a storage rank capacity of 1828 litres. The system has an annual solar fraction and collector efficiency of 0.867 and 0.33. respectively. The total capital investment of the system is 6,733 US$, giving a simple payback period of 7 years which can he reduced to less than 5 years if the capital investment is less than 4,880 US$ or the unit cost of electricity is 9 cents/kWh. A sensitivity analysis on optimum collector area reveals that the area is more sensitive to optical efficiency (FR (τα)) than to the rate of thermal losses (FRUL). Long-term thermal and economic performance results of the designed system show that the system is worthy of installation.
A thesis submitted to the school of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, in partial fulfillment of the requirement for the award of the degree of Master of Science in Mechanical Engineering, 2005