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.
The concept of this engine has been applied so far to prototypes of three different pump models i.e. the Volanta pump, a micro solar suction pump and a small deep well irrigation pump.
The prototypes are presently being tested in the PRACTICA laboratory in the Netherlands and at the PRACTICA field offices in Ethiopia and Burkina Faso.
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.
All three collector models have their specific advantages and draw-backs and will be matched with the different types of solar pumps.
Manufacture and marketing
After completion of the field testing, PRACTICA will facilitate the manufacture in a suitable low cost country (e.g. India or China) and work with the producer to establish a supply chain to the end user. The aim is to get the customer price as low as possible (extreme affordability).
Volanta Thermal Solar prototype, Burkina Faso
Volanta Thermal Solar prototype running in Burkina Faso
