Holistic Design Approach for Geothermal Binary Power Plants with Optimized Net Electricity Provision

Abstract

The contribution of geothermal binary power plants to the energy system is based on the provision of net electricity. That is defined by the produced gross electricity from which the auxiliary power to run power consuming components in the different parts of the plant must be deduced. In contrast to other thermal power plants the ratio of auxiliary power to gross electricity can significantly vary in geothermal binary power plants depending on site-specific conditions. It typically lies between 30 to 50 % but can be also higher depending on the site-specific energetic effort to deliver the geothermal fluid from the reservoir or the effort for the recooling of the conversion cycle. In order to optimize the provision of net electricity at a specific site it is hence important to consider the different characteristics of gross electricity production and auxiliary power consumption. The paper will therefore introduce a geothermal-specific, holistic design approach in which not only parameters, which characterize the quality of single plant components, but also site-specific reservoir and ambient conditions are considered. A case study will show that maximizing the installed electrical capacity, which is typical in other power plant applications, does not result in an optimum net electricity output. With the presented methodology, in contrast, it is possible to realize geothermal binary power plants with a higher net electricity output based on existing technology.