Concentrating Solar Power

DESCRIPTION Concentrating Solar Power (CSP), also referred to as solar thermal power, uses mirrors to concentrate the sun's rays to heat a fluid that is then used to generate electricity, often using conventional steam turbines. There are three primary CSP technologies: parabolic trough, solar tower, and dish engine. The most common CSP system is the parabolic trough, which uses curved mirrors with single-axis tracking to concentrate sunlight on a receiver tube or collection element that contains a heat transfer fluid, such as synthetic oil, molten salt or steam. The heated fluid is passed through a heat exchanger to produce steam, which then drives a turbine to generate electricity. CSP tower systems employ a field of mirrors to concentrate sunlight on a receiver at the top of a tower. Tower systems typically achieve higher operating temperatures, which in turn allows for increased energy storage. Dish engine systems use parabolic reflectors that concentrate solar energy on a receiver located at the focal point of the reflector. The receiver includes a Stirling engine or small gas turbine that generates electricity. Unlike photovoltaic installations, solar thermal facilities can store energy in molten salt or other medium, allowing them to dispatch energy to the grid even after the sun has gone down. Solar thermal power requires about 3 to 8 acres per MW of installed capacity, depending on the technology and amount of thermal storage. COST Installed cost for parabolic trough systems in 2011 ranged from $4.6 million/MW for systems with no thermal storage to $9.8 million/MW for systems with up to 6 hours of thermal storage. For solar tower systems, installed costs ranged from $6.3 million/MW (6 hours of storage) to $10.5 million/MW (up to 15 hours of storage). Fixed O&M costs were estimated at $20 to $35 per MWh. CAPACITY FACTOR Capacity factor for a parabolic trough system with no storage is estimated to be around 25%. For CSP systems with 6 hours of thermal storage, a capacity factor of 40% to 50% is realistic. Land acquisition and permitting are the most significant time constraints for CSP. Once those hurdles have been overcome, physical construction can generally be completed within 2 to 3 years, depending on the size of the facility. NOTES Abengoa is currently constructing what is billed as the world's largest CSP facility near Gila Bend, AZ. The Solana Generating Station is a 280 MW parabolic trough installation estimated to cost …