Summary
Solar Thermal technology offers the promise for carbon free generation, but not without dealing with issues common to large central generation sources and some unique to the technology: 1. the need to demonstrate the technology 2. transmission access 3. water supply 4. low capacity factors 5. the need for complimentary storage technologies
Analysis
The recent article “Solar thermal projects gather steam -- and opposition” points up some of the promise of solar thermal technologies to produce electricity from non-carbon emitting sources. The article addresses some of the challenges facing the technology but misses some of the basic issues.
First, this is not an established technology with the all of the manufacturing facilities in place to support growth. There are only a few working plants worldwide with limited operating experience. While the technology is very promising it will still undergo the kind of start-up problems and set backs that all emerging technologies are subject to. Incentives and development support will be necessary to move the technology to commercial viability.
As with any central generating plant operation, solar thermal plants will need access to the transmission system. Siting for transmission lines is often a lengthy and contentious process. Solar thermal plants will not be immune to this fact.
The technology discussed in the article referred to a process where solar energy is used to supply the heat source to drive a traditional steam turbine. The article did not touch on the need to provide a water source to supply the turbine. In markets like California, where access to large water supplies is increasingly competitive, this may be a limiting factor to development. Environmental issues associated with water use will not go away just because the generating source is solar.
Annual capacity factors are still only estimated in the 25 to 50% range. This means like wind and other intermittent sources of generation, solar thermal generation will only be available part of the time and will require other generation capacity to fill the gap.
Because solar energy is not available 24 hours-a-day, there will be a need to compliment solar thermal technologies with some type of energy storage system. Some of the solar thermal designs do this by incorporating molten salt storage systems into their design. Others will be depended on system storage such as hydroelectric pumped storage or compressed air energy storage (CAES). Pumped storage plants (the most commercially mature of the storage technologies) take years to design and build. Their development will also be a factor in the development of multiple solar thermal projects. Regardless of the storage mechanism, the electrical system as a whole will need to balance the generation from the solar thermal sources.
Solar thermal generation is a promising technology in the demonstration phase of development. Like other renewable sources of electrical power it will grow based on a combination of research and development funding, government incentives and a supportive regulatory environment. Even with this support it will still need to deal with the issues common to any central generating facility.
