The Solar Engine Irrigation System (SEIS) is a solar powered irrigation system based around combining the mechanical output of a heat engine with a fluid pump. The heat engine is a free-piston variant of a Stirling/Ericsson cycle engine based on a thermomechanical generator developed at Harwell by Ted Cooke-Yarborough (see patent US 4,345,437) and further developed by others (see patent GB2298903). The thermomechanical generator has only one moving part and is designed so that it has no surfaces undergoing mechanical wear leading to an extremely reliable and long lasting mechanism. One version of the TMG recorded the the longest service-free design life for any engine and lasted 90,000 hours before service intervention was required. The SEIS uses the upper diaphragm on the TMG to act as the moving component and is coupled to the pump. Two pump type options (both positive displacement) are proposed to offer additional site-specific opportunities - such as differing well depths and levels of water contamination. Their designs have been chosen to provide good lift, dry running and self-priming characteristics, tolerance to grit and sludge and high efficiency. The heat source for the engine is provided by a very low cost solar reflector designed to capture ambient light over a range of solar elevations. Optionally other heat sources could be used. The work is to be undertaken by the combined capabilities of Azur Innovation, Bowman Process Technology and the water charity Practical Action with technical advice from Nottingham University.