The geothermal analog of pumped storage for electrical demand load following
A 6 day cycle Load-Following Experiment, conducted in July 1995 at the Fenton Hill Hot Dry Rock (HDR) test site in New Mexico, has verified that an HDR geothermal reservoir has the capability for a significant, rapid increase in thermal power output upon demand. The objective was to study the behavior of the HDR reservoir in a high-production- backpressure (2200 psi) baseload operating condition when there was superimposed a demand for significantly increased power production for a 4 hour period each day. In practice, this enhanced production, an increase of 65%, was accomplished by a programmed decrease in the production well backpressure over 4 hours, from an initial 2200 psi down to 500 psi. The rapid depressurization of the wellbore during the period of enhanced production resulted in the draining of a portion of the fluid stored in the pressure dilated joints surrounding the production well. These joints were then gradually reinflated during the following 20-hour period of high backpressure baseload operation. In essence, the HDR reservoir was acting as a fluid capacitor, being discharged for 4 hours and then slowly recharged during the subsequent 20 hours of baseload operation. In this mode, there would be no increase in the reservoir size of number of wells (the {ital in situ} capital investment) for a significant amount of peaking power production for a few hours each day. Thus, one of the advantages of geothermal load following over utility options such as pumped storage or compressed air storage is that the HDR power plant would be operated during off-peak hours in a baseline mode, with an augmented return on investment compared to these other peaking systems which would normally not be operated during off-peak periods. The surface power plant and the geofluid reinjection pumps would need to be sized for the peak rate of thermal energy production, adding somewhat to the overall HDR system capital costs when compared to a simple baseload power plant design.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 286057
- Report Number(s):
- LA-UR--96-2088; CONF-9609209--1; ON: DE96012647
- Country of Publication:
- United States
- Language:
- English
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Experimental verification of the load-following potential of a Hot Dry Rock geothermal reservoir
Experimental verification of the load-following potential of a hot dry rock geothermal reservoir