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Title: Solar Field Optical Characterization at Stillwater Geothermal/Solar Hybrid Plant

Abstract

Concentrating solar power (CSP) can provide additional thermal energy to boost geothermal plant power generation. For a newly constructed solar field at a geothermal power plant site, it is critical to properly characterize its performance so that the prediction of thermal power generation can be derived to develop an optimum operating strategy for a hybrid system. In the past, laboratory characterization of a solar collector has often extended into the solar field performance model and has been used to predict the actual solar field performance, disregarding realistic impacting factors. In this work, an extensive measurement on mirror slope error and receiver position error has been performed in the field by using the optical characterization tool called Distant Observer (DO). Combining a solar reflectance sampling procedure, a newly developed solar characterization program called FirstOPTIC and public software for annual performance modeling called System Advisor Model (SAM), a comprehensive solar field optical characterization has been conducted, thus allowing for an informed prediction of solar field annual performance. The paper illustrates this detailed solar field optical characterization procedure and demonstrates how the results help to quantify an appropriate tracking-correction strategy to improve solar field performance. In particular, it is found that an appropriatemore » tracking-offset algorithm can improve the solar field performance by about 15%. The work here provides a valuable reference for the growing CSP industry.« less

Authors:
 [1];  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G)
OSTI Identifier:
1342371
Report Number(s):
NREL/JA-5500-67541
Journal ID: ISSN 0199-6231
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Solar Energy Engineering
Additional Journal Information:
Journal Volume: 139; Journal Issue: 3; Journal ID: ISSN 0199-6231
Publisher:
ASME
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 47 OTHER INSTRUMENTATION; concentrating solar power; geothermal energy; parabolic trough; optical characterization; optical error; hybrid system

Citation Formats

Zhu, Guangdong, and Turchi, Craig. Solar Field Optical Characterization at Stillwater Geothermal/Solar Hybrid Plant. United States: N. p., 2017. Web. doi:10.1115/1.4035518.
Zhu, Guangdong, & Turchi, Craig. Solar Field Optical Characterization at Stillwater Geothermal/Solar Hybrid Plant. United States. doi:10.1115/1.4035518.
Zhu, Guangdong, and Turchi, Craig. Fri . "Solar Field Optical Characterization at Stillwater Geothermal/Solar Hybrid Plant". United States. doi:10.1115/1.4035518. https://www.osti.gov/servlets/purl/1342371.
@article{osti_1342371,
title = {Solar Field Optical Characterization at Stillwater Geothermal/Solar Hybrid Plant},
author = {Zhu, Guangdong and Turchi, Craig},
abstractNote = {Concentrating solar power (CSP) can provide additional thermal energy to boost geothermal plant power generation. For a newly constructed solar field at a geothermal power plant site, it is critical to properly characterize its performance so that the prediction of thermal power generation can be derived to develop an optimum operating strategy for a hybrid system. In the past, laboratory characterization of a solar collector has often extended into the solar field performance model and has been used to predict the actual solar field performance, disregarding realistic impacting factors. In this work, an extensive measurement on mirror slope error and receiver position error has been performed in the field by using the optical characterization tool called Distant Observer (DO). Combining a solar reflectance sampling procedure, a newly developed solar characterization program called FirstOPTIC and public software for annual performance modeling called System Advisor Model (SAM), a comprehensive solar field optical characterization has been conducted, thus allowing for an informed prediction of solar field annual performance. The paper illustrates this detailed solar field optical characterization procedure and demonstrates how the results help to quantify an appropriate tracking-correction strategy to improve solar field performance. In particular, it is found that an appropriate tracking-offset algorithm can improve the solar field performance by about 15%. The work here provides a valuable reference for the growing CSP industry.},
doi = {10.1115/1.4035518},
journal = {Journal of Solar Energy Engineering},
number = 3,
volume = 139,
place = {United States},
year = {Fri Jan 27 00:00:00 EST 2017},
month = {Fri Jan 27 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
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  • The Stillwater Power Plant is the first hybrid plant in the world able to bring together a medium-enthalpy geothermal unit with solar thermal and solar photovoltaic systems. Solar field and power plant models have been developed to predict the performance of the Stillwater geothermal / solar-thermal hybrid power plant. The models have been validated using operational data from the Stillwater plant. A preliminary effort to optimize performance of the Stillwater hybrid plant using optical characterization of the solar field has been completed. The Stillwater solar field optical characterization involved measurement of mirror reflectance, mirror slope error, and receiver position error.more » The measurements indicate that the solar field may generate 9% less energy than the design value if an appropriate tracking offset is not employed. A perfect tracking offset algorithm may be able to boost the solar field performance by about 15%. The validated Stillwater hybrid plant models were used to evaluate hybrid plant operating strategies including turbine IGV position optimization, ACC fan speed and turbine IGV position optimization, turbine inlet entropy control using optimization of multiple process variables, and mixed working fluid substitution. The hybrid plant models predict that each of these operating strategies could increase net power generation relative to the baseline Stillwater hybrid plant operations.« less
  • Ormat Energy Systems, Inc., announced it has received a construction loan for the Stillwater Geothermal I Project near Fallon, Nevada. The 17-megawatt, gross, air-cooled power plant is expected to be in full operation by the second quarter of 1989, and selling power to Sierra Pacific Power Company under a 30-year contact.
  • The feasibility of a geothermal-coal hybrid power cycle was studied in comparison to a strictly geothermal and a coal-fired plant in the Chalk Creek area, Chaffee County, Colorado. The geothermal reservoir in this area is postulated to be liquid dominated with a temperature ranging from 150/sup 0/C to 200/sup 0/C (Pearl 1978). The thermal waters are very low in dissolved solids (250mg/l), and, therefore, corrosion problems should be minimal in steam turbines. Development of the geothermal resource in the Chalk Creek area has been limited so far to direct use in greenhouses, swimming pools, and residential space heating. This papermore » considers the possibility of generating approximately 50 MW of power using the available geothermal energy in a hybrid or geothermal cycle as an alternative to producing electricity from a straight coal-fired plant.« less
  • Distributed temperature sensing (DTS) systems provide near real-time data collection that captures borehole spatiotemporal temperature dynamics. For this study, temperature data was collected in an observation well at an active geothermal site for a period of eight days under geothermal production conditions. Collected temperature data showcase the ability of DTS systems to detect changes to the location of the steam-water interface, visualize borehole temperature recovery — following injection of a coldwater “slug” — and identify anomalously warm and/or cool zones. The high sampling rate and spatial resolution of DTS data also shows borehole temperature dynamics that are not captured bymore » traditional pressure-temperature survey tools. Inversion of thermal recovery data using a finite-difference heat-transfer model produces a thermal-diffusivity profile that is consistent with laboratorymeasured values and correlates with identified lithologic changes within the borehole. Used alone or in conjunction with complementary data sets, DTS systems are useful tools for developing a better understanding of both reservoir rock thermal properties as well as within and near borehole fluid movement.« less