An Investigation into the Seasonal Economic and Energy Performance of CO2 Plume Geothermal (CPG) Power Plants

Abstract

CO2 Plume Geothermal (CPG) energy production is a renewable form of energy that combines geothermal technology with CO2 sequestration, using the CO2 as the working fluid in naturally permeable thermal reservoirs. In this thesis, we compare the energy and economic performance of an electricity production only CPG plant, as well as CPG plants with that of a combined heat and power (CHP) and district heating cooling (DHC). Initially, the monthly economic parameters of electricity-only CPG power plants are modeled for six cities: Williston, ND, Dallas, TX, New Orleans, LA, Houston, TX, Sacramento, CA, and Williamsport, PA. Meteorological data for each city are used to determine energy production and electric power is assumed to be sold in a competitive market. The monthly economic performance of each plant is compiled over 20 years, the assumed lifetime of a CPG plant, and used to determine each plant's potential for profit. It is found that it is crucial to consider location when determining the economic potential of CPG plants. Cool climates tend to result in higher electricity production as a result of a higher thermodynamic plant efficiency; however, it is also necessary to consider the economic environment, as electricity prices can have just as much of an impact, if not more, on a plant's financial performance. CPG power plants are also found to be economically competitive with other renewable energy options at the same capacity level and current CO2 sequestration and tax incentives can make unfavorable CPG power plants profitable. Next, CPG CHP DHC plants are considered, and three cases of heat production are investigated. Case 1 assumes the system meets peak winter heat demand, Case 2 assumes that some form of thermal storage is available and the system meets average monthly heat demand, and Case 3 assumes that all possible heat produced during winter months is sold. Electricity and heat are assumed to be sold in a competitive market. Six cities are considered, Williston, ND, Dallas, TX, New Orleans, LA, Houston, TX, Sacramento, CA, and Williamsport, PA, spanning 4 of the 5 US climate zones (Zones 1, 2, 3, and 5). Meteorological data are used to estimate energy production and heat demand. CPG is found to produce CO2 at high enough temperatures to be used in a district heating system. Case 1 most closely matches actual demand ratios for power vs heat in the various cities. CPG CHP/DHC plants in cities located in Zone 1 and Zone 2 climates have a higher net present value (NPV) than electricity-only plants. Case 2 and Case 3 CPG CHP/DHC plants in Zone 3 and Zone 5 can have a higher NPV than electricity only, but more consideration must be given to heat demand to ensure profit is increased. In all cities considered, tax credits and CO2 sequestration benefits can increase financial performance of CPG CHP/DHC plants.