Low temperature solar thermal energy system for energy generation and desalination

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On our planet, solar energy is an abundant renewable resource. The conversion of solar into thermal energy is currently the most efficient way to use this resource. Concentrated Solar Power plants, which use mirrors to focus the solar energy to generate high temperatures, are however costly, and require large installations. Flat plate collectors, which today have efficiencies of 50% at a temperature of 120C, are potentially a cost effective solution. The problem here lies in the conversion of this low-grade heat into usable energy. At Southampton University, we recently developed the condensing engine (CE) - a heat engine which employs water as working fluid with an operating temperature of 100C. The engine uses the condensation of steam and the arising vacuum as driving force, rather than the pressure of steam. It operates at atmospheric pressure, so that safety issues are minimal. The use of steam expansion gives an efficiency of 10% or more. In combination with flat plate collectors, the CE has the potential for the development of a simple, cost-effective, modular solar thermal system, which produces electricity as well as fresh water from the condensation process. In this project, we will develop a theoretical framework for a solar thermal system for electricity production and desalination with the aim to assess its overall productivity. For the key component, the condensing engine, a theoretical model will be developed.as basis for its optimisation. Based on the results, an experimental 100 Watt engine will be built and tested. Recent theoretical work suggests that through heat recovery from the condensation process, the power output can be increased by 30-35%, and the water production by 70 to 80%. This would lead to a novel, 2-stage energy conversion cycle and would improve the cost-effectiveness of the system substantially. The heat-recovery condensation process will be developed, modelled, and tested in the laboratory.The project will result in an optimised solar thermal energy and desalination system with novel, efficient and cost-effective components. The project runs in cooperation with Synext Ltd., Delft/Netherlands. The simplicity of the system, and its modular character mean that it would also be well suited for deployment in developing countries where there is an urgent need for both energy and clean water. This aspect will also be explored in cooperation with synext Ltd.