NUMERICAL OPTIMIZATION OF A COGENERATING PARABOLIC SOLAR COLLECTOR RECEIVER

摘要

The motivation for this study comes from the need for a clean, renewable energy source, which is greater now more than ever to reduce the country's dependence on fossil fuels. Cogenerating solar systems can provide heat and electricity for many industrial applications such as power generation and absorption refrigeration systems. For example, data centers that run on conventional refrigeration systems are one of the largest electricity consumers in the nation, accounting for 1.2% of the total electricity consumption in 2005. This electricity consumption, almost half of which is used to run the data center's air conditioning units, translates to $2.7 billion in electricity costs for that year. Using cogenerating solar systems for these types of applications could represent a significant amount of savings in electricity costs.The objective of this paper is to numerically optimize a receiver for a cogenerating photovoltaic and thermal parabolic solar collector that will produce both heat and electricity. The solar cogeneration system studied will convert solar energy into both heat and electricity by using a combination of photovoltaic cells, a parabolic trough thermal collector, and water as the liquid heat exchanger on the photovoltaic cells. The peak electrical efficiency of the multi-junction gallium arsenide Spcctrolab photovoltaic cells used in this study is about 32%, with the rest of the solar energy being absorbed as heat. These temperature gains in the cells can lead to a decrease in efficiency. However, in cogencraling systems, water is used as a working fluid to remove heat from the photovoltaic cells, thus aiding in increasing the electrical efficiency of the photovoltaic system as well as increasing the thermal energy gained from the solar thermal collector.The numerical analysis for this project will use Flothcrm, a CFD tool used to solve fluid and thermal problems. A single-phase water cooled square duct receiver subjected to non-uniform heating will be analyzed in Flotherm to determine the optimal parameters for the best convection heat transfer between the working fluid and the photovoltaic cells. To enhance the heat transfer between photovoltaic cells and working fluid, the inner surface of the receiver tube receiving the heat flux will be improved by adding fins to increase heat transfer and induce turbulent flow. The initial receiver design will be compared with other receivers to determine the optimal design. Results will be presented parametrically for a range of flow rates and receiver geometry.