Solar heat can be converted into shaft power by use of the Organic Rankine Cycle Engine (ORCE). The efficiency of the ORCE to convert the solar heat to shaft power varies from 7 or 8 percent for an ORCE heated by low temperature flat plate collectors at 200 F, to near 15 percent when heated by intermediate temperature collectors (300 F), and up to 25 percent with high temperature concentrating collectors (600 F). Barber-Nichols designed, built, and tested its first solar heated ORCE in 1973, which produced three tons of air conditioning. Since that time, the three-ton unit has reached its fourth iteration on the development path to production; a 77-ton water chiller was installed at LASL; two ORCE drives for 100-ton water chillers were delivered to Honeywell; seven 25-ton water Chillers were delivered to DOE demonstration sites; and a 25-hp ORCE for irrigation pumping was installed in Willard, N.M. Photographs, design details, and the measured performance of these units are presented herein as examples. The cost of solar power systems using an ORCE is also presented which shows that for the current $150 to $200/m2 cost of cencentrating collectors, the system cost would be in excess of $2500/kw peak. The ORCE is approximately 25 percent of this cost or $600/kw. Consequently, while reductions in the cost and improvements in the performance of the ORCE can and should be made in the development process, the cost competitiveness of a solar power system is largely dependent on developing low cost concentrating collectors which can be sold for 1/2 to 1/3 of today’s price.

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