Direct Steam Generation could hold the secret to reaching higher steam temperatures and simplifying balance of plant configurations for large-scale concentrated solar thermal power projects.

As the Concentrating Solar Power industry moves forward into an era of large-scale development in the United States the ability to reach higher operational temperatures to improve the efficiency of solar thermal power production is at the forefront of R&D efforts. In a recent interview with CSP Today, Juergen Peterseim of Eckrohrkessel GmBH, emphasized the advantages of direct steam generation when compared to conventional heat transfer systems.

Experts argue that a key advantage of using direct steam as a heat transfer fluid is that it would allow for operational temperatures in excess of 500°C, at which steam turbines are more efficient and well developed for current industrial type applications. Specialist also argue that replacing oil with water in the HTF process will reduce the environmental risks in Concentrating Solar Power, as well as simplify overall plant configuration for lowered investment and O&M costs. Peterseim also stated that “there is no need to circulate a second fluid which in turn reduces pumping power and parasitic losses”.

However, despite this potential, maintaining a stable fluid flow is the main challenge presented by direct steam generation. Peterseim went on to say that this challenge “is mainly caused by cloud covering of sections of the solar field”, explaining that “a reduced heat flux in one part of the plant can affect the water circulation to certain areas or reduce water access to others”. Therefore, hot spots that occur on absorber tubes as a result of this flow stratification would cause damage to balance of plant components and lead to extended plant downtime. He explained that to combat this “it is crucial to maintain a stable flow to ensure permanent cooling of the absorber tubes, and this can only be achieved by a very precise water circulation design”.

Peterseim will be discussing the advantages of Direct Steam Generation at the 2nd CSP Plant Optimization Summit later this year in San Francisco (7-8 September). The event is aimed at those looking to optimize plant efficiency and drive down LCOE in Concentrating Solar Power, and will bring together leading developers, EPC groups and technology providers throughout the United States. For