| Title | Binary Power Plant Modelling and Sensitivity Analysis for Electricity Generation from an Enhanced Geothermal System |
|---|---|
| Authors | Aaron Hochwimmer, Rory Coventry, and Sam Pearce |
| Year | 2013 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Power Generation, Organic Rankine Cycle, Enhanced Geothermal System, Numerical Modeling, Economic Assessment |
| Abstract | A numerical model of a geothermal well field and subcritical binary Organic Rankine Cycle (ORC) power plant is presented. This model allows the performance of different plant heat rejection systems (i.e. dry air cooling, evaporative wet cooling, once through wet cooling) to be analysed and the equipment to be sized. The model uses NIST REFPROP as source of thermodynamic data, which allows for the performance of commercially available binary working fluids to be readily evaluated and compared. Of note the model is designed to allow the plant ‘off-design’ power output to be evaluated across a range of geothermal resource and ambient temperatures in order to estimate the annualised net generation for prospective geothermal projects. As part of a broader feasibility study for power generation from an Enhanced Geothermal System (EGS) site in Europe, the model is used to compare and contrast performance from different heat rejection options for a brine fed binary power plant. A direct heat cascade use has also been considered. A sensitivity analysis is presented for each plant option including variation of ambient conditions, monthly ambient data, geothermal brine flow, and geothermal brine temperature. The performance of each plant design for alternative working fluids is presented, as are the water supply requirements. The environmental impacts and site requirements for major equipment are discussed. Capital and operational cost estimates (+/- 40%, 2012 basis) have been derived as an input to financial modelling. The return on investment for different options is presented to help inform option evaluation of power plant technologies. |