The Chena Hot Springs 400kW Geothermal Power Plant: Experience Gained During the First Year of Operation

Abstract

In July 2006, Chena Hot Springs Resort installed the first of two 200kW Organic Rankine Cycle (ORC) power plant modules designed and built by United Technologies Corporation (UTC) at their Hartford, Connecticut research facility. The second unit was brought online the following December. The modules were designed based on the PureCycle 200 product released by UTC in 2004 and designed to operate off industrial waste heat applications. The PureCycle 200 uses components and hardware from the Carrier Refrigeration line, which is a division of UTC, in over 90% of the system. This greatly reduces the upfront cost of the equipment since air-conditioning equipment has a cost structure significantly lower than traditional power generation equipment. This is significant because Chena Hot Springs is a moderate temperature geothermal resource with a maximum produced water temperature of only 165ºF. For this reason, any ORC designed to generate power from the Chena resource is saddled with an inherently a low thermal efficiency. Low efficiency requires increased power plant equipment size (turbine, condenser, pump and boiler) that can ordinarily become cost prohibitive. One of the main goals for the Chena project was to reduce the equipment cost of these UTC designed PureCycle modules to $1300 per kW. This paper describes the site preparation, installation and operation of the two PureCycle 200 units, and experience gained as the first anniversary of the installation approaches. This paper does not focus on the design of the system, which has already been covered in two previous papers presented at the 2005 (Joost, Biederman, Holdmann) and 2006 (Cogswell) GRC Annual Meeting.