Solar-powered Stirling engine
A solar powered Stirling engine is a heat engine powered by a temperature gradient generated by the sun. It was patented by Roelf J. Meijer in 1987. His invention relates a heat engine, such as a Stirling cycle engine, with a solar dish collector in order to produce electricity. This apparatus consists of a large dish aimed at the sun to reflect the rays into the focus point, which is located at the center of the dish. Solar energy is then collected in the form of heat to fuel a Stirling cycle engine,  which operates by letting heat flow from a hot source to a cold sink in order to do work. The work output of the Stirling cycle is then used to drive a generator and create electric power. Moreover, in Meijer’s solar-powered engine, it is important that the dish always be pointed directly at the sun so that no shadows would be present in the solar dish collector, hence optimizing heat collection. This is where he ran into some issues because, in order for the apparatus to have a complete range of motion, lubrication and rotational systems would be necessary and may compromise structural stability.
A second type of solar-powered Stirling engine was patented by NASA on August 3, 1976 which employed the use of solar energy in order to freely pump water from a river, lake, or stream. The purpose of this apparatus is to “provide a low-cost, low-technology pump having particular utility in irrigation systems employed in underdeveloped arid regions of the earth…[using] the basic principles of the Stirling heat engine 
Recently, a company called Sunvention Solar Energy created a device very similar to what NASA came up with in 1976 that can pump 100,000 gallons per day purely off of solar energy and usage of the Stirling cycle costing only US$1,250  This apparatus, much like the others, uses a large solar dish to collect heat from the sun creating a high temperature source and also employs the low temperature water it collects from a nearby stream as its low temperature source allowing for a great range in temperature which in turn allows for more work to be done  The work done in Sunvention’s apparatus is used to pump the water into nearby crop fields allowing for a “low-cost, low-technology pump having particular utility in irrigation systems employed in underdeveloped arid regions of the earth”. 
- 4,707,990, Meijer, Roelf, "Solar-powered Stirling engine", published November 24, 1987
- Moran, Michael (2011), Fundamentals of Engineering Thermodynamics, Hoboken NJ, pp. 72–73
- 3,972,651, Fletcher, James & Charles Kirsten, "Solar-powered pump", published August 3, 1976
- Ardron, Mitra (October 28, 2010), Sunvention Sunpulse Water (PDF), retrieved April 10, 2012.
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