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In this study a commercial evacuated tube solar hotwater system was modified to be used as a thermal-power source for a thermodynamic engine. Commercial hot-water systems are meant to operate at temperatures that are close to the boiling point of water. Single-tube non-imaging concentrators were built in order to increase the input solar-radiation per tube and therefore supply thermal-power at temperatures of 180 − 220 • C. Simulations and experiments show that it is possible to use concentrators to increase the temperature range of thermal power extracted from a commercial evacuated tube system and use this modified system to increase the efficiency of solar-thermal energy generation.

This paper focuses on the design of a Stirling engine for distributed solar thermal applications. In particular, we design for the low temperature differential that is attainable with distributed solar collectors and the low cost that is required to be competitive in this space. We will describe how these considerations drive the core design, the methodology for improving the design, and summarize progress made in fabrication of the engine for experimentation.Stirling engines can have broad significance and technological advantages for distributed renewable energy applications. A key advantage of a solar thermal system is that they can incorporate thermal energy storage in a cost-effective manner. In addition, Stirling engine systems are fuel-flexible with respect to the source of thermal energy and unprocessed waste heat can be harvested for CHP purposes as well. The ability to extract unconverted thermal energy for waste heat applications greatly improves the overall thermal efficiency of the system.

This paper describes initial stage of experimentation on a 2.5 kW Stirling engine designed for distributed solar thermal electric and combined heat applications. Experimentation conducted over this period include testing of the integrated permanent magnet alternator, testing of various losses such as flow friction and running losses, heat exchanger fluid flow characteristics, while driven in reverse as a heat pump. This paper will include a brief description of the intended design and applications, a description of the experiments thus far, and a comparison with prior analysis from the design phase.