ABSTRACT:
The conceptual design and economic assessment of a sodium-cooled, solar central receiver repowering system for Texas Electric Service Company's Permian Basin Steam Electric Plant Unit No. 5 has been completed. A repowering system is one in which a central receiver tower, surrounded by a field of mirrors, is placed adjacent to an existing electric utility power plant, and supplies steam to the turbine at the same condition as that provided by the existing boiler. When sunshine is available, energy is provided from the solar system, and the amount of fuel consumed is proportionally reduced. Successful construction and operation of a repowered unit during 1985 is projected. Environmental or institutional problems associated with the construction and operation of the Permian Plant Unit No. 5 are minimal. The estimated construction cost of this project is $111.6 x 10^6 in January 1, 1980 dollars; and the utility company's estimate of its equivalent plant investment is $12.5 x 10^6 in January 1,1980 dollars.

As expected, the economic assessment of the specific concept for this site indicates that the cost of energy is greater than that resulting from the burning of natural gas alone in the existing plant (principally, as a result of the current cost of heliostats and the scheduled retirement date of Unit No. 5). Favorable economics for similar types of plants can be projected for the future. The annual fuel savings are equivalent to 236,900 barrels of oil, with a total dollar value of $21.5 x 106 and $93.6 x 10^6 for a 7-year life and a 25-year life, respectively. However, it has also been found, from separate studies, that favorable interpretations of the Fuel Use Act will be necessary for this economic viability to be reached. In particular, a program to reduce the cost of heliostats to $100/m will be needed.