Analysis of Lifecycle Water Requirements of Energy and Transportation Fuels: Electricity from Geothermal Resources – Model Description
Electricity from geothermal resources could play a significant role in the United States over the next few decades; A 2006 study by MIT (Tester, Anderson et al. 2006) considers a capacity of 100GWe by 2050 as feasible; approximately 10% of the total U.S. electricity generating capacity. The growth will come largely from enhanced geothermal resources (EGS) and across a range of temperature conditions. However, there is limited research on the water requirements and impacts of generating electricity from geothermal resources – conventional as well as enhanced.
Our model “Analysis of lifecycle water requirements of energy and transportation fuels: electricity from geothermal resources” establishes a baseline for water requirements of geothermal electricity. It estimates water requirements for electricity from various forms of geothermal resources – wet steam and hot water hydrothermal resources, and enhanced geothermal systems (EGS). Electricity can be generated using flash or binary (organic Rankine cycle) technology depending upon the temperature and pressure of geothermal fluid. Power plants may use three different types of cooling technologies – wet re-circulating, dry systems, and hybrid cooling systems. Requirements are calculated separately for freshwater, degraded water and geothermal fluid.
This document describes the methodology, assumptions, and data sources for the spreadsheet-based model, which is available at http://pubs.its.ucdavis.edu/publication_detail.php?id=1426 .
The model is part of a series exploring the water footprint of future transportation fuels including bio-fuels and electricity. Other models currently under development examine the lifecycle water requirements of ethanol from corn grain and crop residue, and electricity from concentrated solar power, and biodiesel from soybean.