Electricity production at low powers by direct steam generation with parabolic troughs

It is possible to generate electricity by direct steam generation (DSG) in parabolic troughs. Saturated steam at 165 degrees C and 6.89 bar can be supplied to a 2.24 kW steam Stuart Swan motor of the two piston engine type in order to produce mechanical energy, as well as electric energy through a generator, using the recirculation process concept to produce steam. Four modules, with 2.5 m of aperture and 14.5 m long, were connected in series and can produce over 100 kg h(-1) of rated steam. The first, second and third modules have 3.81 cm nominal diameter copper pipe absorbers covered with black chrome, while the fourth module has a 2.54 cm nominal diameter mild steel pipe absorber which is also covered with black chrome. The copper pipes eliminate the bend due to thermal stress when two-phase how goes through them. In this way solar-electricity has been produced with an efficiency of about 3%. (C) 1998 Elsevier Science Ltd. All rights reserved.