The Advanced Direct-Contact Condenser

NREL recently licensed to Alstom an advanced direct-contact condenser (ADCC) that uses sophisticated geometric shapes to provide optimal surface area for condensing spent steam. The ADCC earned an R&D Magazine 1999 R&D 100 award for NREL's Desikan Bharathan and his team, including employees of Alstom and Pacific Gas and Electric Company. Bharathan also received the Technology Transfer from Federal Laboratory to Industry Award from the Colorado Technology Transfer Society for his work on ADCC technology. The technology has been employed at Unit #11 at The Geysers, where it has improved production efficiency by 5% and has cut the chemical cost for emission abatement in half. Because the condenser had been the limiting factor for Unit #11, the refurbishment increased total power generation potential by 17%.

Condensation of spent steam is a key part of the power cycle in electricity-generating plants. Direct-contact condensers mix cooling water with spent steam in an open chamber to condense the steam rather than running the steam around sealed coolant pipes, as in surface condensers. Most existing direct-contact condensers have only perforated plates to provide surface area for condensation; ADCCs, however, have sophisticated geometric shapes to provide optimal surface area for condensing spent steam. In addition to providing surface area, these "packing structures" channel the steam and water for maximum contact with each other.

While developing this technology, NREL researchers created a computer model to evaluate the thermal performance of potential packing structures. This software now allows for the rapid identification of the optimal packing for a particular condenser and power plant. The program also models chemical reactions in the spent steam and cooling water.

ADCCs can replace direct-contact condensers and surface condensers in many of the world's 200 geothermal plants. Owners will recover installation costs within two years. Recovery of first costs is even better for new installations.

ADCC also can be used for fossil-fuel power plants and for food processing or any other industrial process in which steam is condensed.