Solar Thermal Electric Program\\
Source: National Renewable Energy Laboratory
Date: 1/1/95    Record No.: 10093
Contact: Tom Williams, 303-275-3602; Mark Bohn, 303-275-3605

Solar Thermal Electric Program\\

Working closely with industry, the program goals go beyond R&D to facilitate and lower obstacles to commercialization, keeping a clear distinction between long-term technology prospects, and near-term deployment opportunities. NREL provides technical expertise for testing, evaluation, simulation and analysis of systems.

Three main technologies are being pursued: Troughs, central receiver (power tower), and dish stirling engine.

Though Luz went out of business several years ago, the 350 MW of solar trough plants in S. California are continuing to operate under the ownership of 3 separate IPPs. Other ventures are planning commercial trough projects for Mexico and elsewhere (NREL isn't involved).

Central/power tower has been demonstrated at Solar I, which is now being refurbished as Solar II to use molten salt instead of steam at the receiver. NREL has filed a patent on a new "hybrid" concept, described below.

Dish Stirling is aimed at smaller, remote applications, and is getting closer to a commercial reality through a program by SAIC Cummins Power Generation, with support from NREL and Sandia. NREL in particular is testing stretched membrane mirrors for the system.

NREL's current technical niche is in developing advanced optical materials for all three solar thermal technologies, in providing collector design assistance, and in reducing near-term manufacturing costs. The Lab anticipates expanding its work in components. A major effort concentrates on commercialization and new concepts, such as the Hybrid/Combined Cycle Solar Thermal Electric concept.

Solar II introduces a molten salt loop between the receiver and the steam generator. The Hybrid concept is to introduce a gas turbine between the salt loop and the steam system, with an air heat exchanger to take heat from the molten salt and preheat the combustion air for the GT. The solar energy thus becomes a "fuel saver" for the GT, which can be operated conventionally at other times.

Though "impure" as renewable energy, this approach offers advantages of reduced CO2 emissions and the ability to deploy solar at orders of magnitude lower financial risk. Solar thermal power could be introduced at a far lower premium to fossil systems than a stand-alone solar plant approach would require. (Estimates for a stand-alone plant are in the vicinity of $1 billion, where a small hybrid installation would cost less than $40 million over the cost of the GT.) NREL is actively seeking interested parties. A number of technical papers are available, detailing the concept and the economics. (DU, Distributed Utility)