Small Hybrid Solar Power System

This paper introduces a novel concept of mini-hybrid solar power plant integrating a field of solar concentrators, two superposed Organic Rankine -CyclesIORC) and a (bio)Diesel engine. Turbines for the Organic Rankine Cycles are hermetic scroll expandergenerators. Sun tracking solar collectors are composed of rows of flat mirroi bands (CEP) arranged in a plane, which focus the solar energy onto a collector tube similar to those used in SEGS plant in California. The waste heat from both the exhaust gases and block cooling of the thermal engine are also heat sources for the ORCs. Such units are considered to meet electricity, cooling and pumping needs of remote settlements in the sun belt areas or on special sites requiring low temperature heating such as swimming pools or greenhouses. The thermal engine guaranties a minimum level of both power and heat availabiliV at night or during cloudy periods. Laboratory tests, made with the superposed ORCs only, confirmed adequate operational characteristics with good performances over a broad range of conditions. A fewpreliminary tests on the site of the solar power plant when coupled with the engine confirmed a reasonable behavior and the interest of the concept èuen at part load or duying sharp variations of the thermal supply. The performancès are satisfactory for a hybrid solar plant of this power range (10 to 25 kWe) and working so far with rather low temperature solar supply (165"C). First Law electric efficieniies of conversion referred to the fossil fuel supply only (total electricity produced/fuel supply) are of the order of 35% at part load and up to 47% with peak solar radiation. These results are encouraging particularly when one considers that excellent prospects exist for further increasing the supply temperature. However further in-situ testi are required to fully explore the behavior and performance of the complete power plant over a broad range of conditions.