The innovative dual loop CSP system design takes advantage of the proven reliability of Dow’s Dowtherma A heat transfer fluid and the high temperature capabilities of molten salt to produce “approximately 10% more electricity than a conventional CSP system with the same size solar field”. The company therefore estimates that “overall thermal efficiency is increased from 38% to over 42%”.
The company explains that as Dowtherm A fluid is used in the main loop and molten salt is confined to a smaller circuit in the system design, the risk of total plant shutdown is minimised compared to other new CSP concepts using molten salt or other technologies. The main loop can continue to supply superheated steam to power plant turbines and generators even if the salt loop must be shut down for maintenance or repair.
Dow says the overall reliability of the system can make it “an attractive choice to investors”. According to Clint Schmidt, Dow global strategic market manager, the use of Dowtherm A technology is encouraging to financial institutions and governments who underwrite the cost of CSP plant costs. “Because they know the plant can continue to operate reliably to repay their investment, they can be comfortable providing financing without the need to first build a pilot scale demonstration plant.”
Schmidt said “Dow is an established market leader in CSP heat transfer fluids. This latest technology enhances Dow’s approach which includes world-scale production capacity, robust supply chain and logistics capabilities, in depth technical support services and fluid regeneration opportunities.”
The Dow Chemical Company describes itself as a “leader in the CSP market for heat transfer fluids”. These fluids transfer the heat collected in receivers in a CSP plant’s solar field (predominantly parabolic trough receivers) to a power generating station. The transported heat converts water to steam which in turn drives turbines to make electricity. Dowtherm A is a mixture of special fluids that have the high temperature stability required to collect, transport, and store heat effectively for CSP plants.
The American multinational – one of the most important chemical companies in the world – offers a “wide range of support services to ensure the state of the fluid is controlled and maintained, thereby guaranteeing the maximum efficiency of the system and minimum maintenance and downtimes”.
Dow’s heat transfer fluids have been used to fill several flagship CSP plants such as Nevada Solar 1 in the US and the Andasol complex in Spain. Dow announced back in October that it had been awarded additional contracts to supplyDowtherm A to key projects in the CSP market. These recent projects, which include Termosolar Guzman, Astexol-2 (Elecnor), Aste 1A (Elecnor), Aste 1B (Elecnor), Extresol 3,Orellana, Africa Solar and Termosolar Borges are slated to begin in late 2011 and 2012 and are expected to bring approximately 375 MW of power.
“These newest contracts demonstrate Dow’s continued market leadership in CSP solar power applications, Clint Schmidt, Strategic Marketing Manager for Dow stated. “These key contracts will propel Dow to once again achieve record supply volumes of DOWTHERM™ A for solar power applications.”
As of September 2011, Dow has filled 22 plants. These plants will provide power for the equivalent of approximately 650,000 homes and save 2.5 million metric tons of carbon dioxide emissions per year.
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