Need identification and approach
PRACTICA recognizes the need for affordable solar pumps in developing countries. From its experience, the presently availably solar PV pumps are too expensive and the solar panels are prone to theft. To achieve low cost, PRACTICA has taken up the development of solar thermal conversion to drive water pumps. This is done through the Rankine cycle, using steam as the working fluid.
All the R&D work by PRACTICA is done against the background of the conditions in developing countries in terms of affordability, performance requirements, maintenance infrastructure etc.
Solar steam engine
Although thermal conversion has the potential to be much cheaper, the challenge is to design a small steam engine that operates with a high efficiency. Early on in the R&D process, PRACTICA identified the phenomenon of “entrance condensation” as the main cause of low efficiency for small reciprocal steam engines and consequently much research has been directed at reducing this loss. This resulted in a new engine design making optimum use of modern synthetic materials. This new engine has achieved an overall efficiency as high as 50% on the test bench, requires little maintenance is and simple and cheap to produce.
Solar steam generator
To generate the steam for the engines, PRACTICA has developed three types of solar collectors i.e. a vacuum tube collector, a linear Fresnel collector and a parabolic dish collector. All three have been extensively tested on overall efficiency, instantaneous efficiency and steam production.
An important aspect of a solar collector to generate steam is that the boiler is properly designed to optimize heat transfer and steam-water separation.
At this stage, the parabolic dish is giving the best performances against the lowest costs
Manufacture and marketing
In 2012, PRACTICA has made a start to set up production of the pumps in Ethiopia. Opportunities are being explored to start production of kits or complete pumps in India as well.
Branding and marketing of the solar steam pump has been started under the name Sunflower pump – check www.sunflowerpump.org.
