“The brainchild of rocket scientists and a private equity group specialized in renewable energies, SolarReserve, the solar energy development company, is primed to be a winner in the concentrated solar power sector.
United Technology subsidiary, Pratt & Whitney Rocketdyne, has combined its liquid rocket engine heat transfer technology and molten salt handling expertise to develop a unique tower receiver technology with thermal storage capabilities – for which SolarReserve is the exclusive license holder.
Another key ingredient is SolarReserve’s founding partner – the US Renewables Group, a US$575 million private equity firm exclusively focused on renewable power and clean fuel projects.
And finally: the team. SolarReserve’s blend of professionals from the energy, technology and finance industries are proving to be a knockout combination.” [Source: CSP TODAY].
Parabolic troughs, which have been in operation since the mid-1980′s, are currently the most commercial technology and hence the main competitor for any solar thermal technology. Parabolic trough plants have proven a maximum efficiency of 21% (with an average of 12% to 15%) for the conversion of direct solar radiation into grid electricity. While the plants in California uses synthetic oil as heat transfer fluid in the collectors, efforts to achieve direct steam generation within the absorber tubes in order to reduce costs further did not achieve a viable system so far.
Another option is the approximation of the parabolic trough by segmented mirrors according to the principle of Fresnel. Although this will reduce efficiency, it shows a considerable potential for cost reduction. The close arrangement of the mirrors requires less land and provides a partially shaded, useful space below.
Despite improvements in performance of the parabolic troughs new generations, the cost of electricity with solar only is relatively high. Hence lower limit of costs (through Feed-In-Tariff (FIT) or competition) will not enable this technology to be competitive for the long run. For larger scale power generation, Central receivers, which utilize a collection of heliostats – mirrors which track the sun and concentrate the radiation onto a central receiver located at the top of a tower – hold out a huge potential for lower costs. Concentrating the sunlight enables heating a heat transfer fluid up to 1200ºC and higher. Today, molten salt or air or water is used to absorb the heat in the receiver. The heat may be used for steam generation or making use of the full potential of this high-temperature technology – to drive gas turbines. For gas turbine operation, the air to be heated must pass through a pressurized solar receiver with a solar window. Combined cycle power plants (like Aora’s) require about 30% less collector area than equivalent steam cycle.
Another option is based on Parabolic Dish, which are relatively small concentrators that have a motor-generator or a turbo-generator in the focal point of the reflector. This generator may be based on Stirling engine or a gas turbine. Because of their size, they are particularly suited for decentralized electricity supply and remote stand alone systems. Dishes up to 400m² have been built and other even larger are being currently designed. Although significant progress has been made on most major components including the high performance dish, it is too early to determine whether the promises of developing a simple, low cost and very reliable engine will be realized by new designs. Moreover, this technology is inherently nondispatchable without storage or fuel backup, so can not reach utility’s dispatch requirements.