ASTM E974-21

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E974 − 21
Standard Guide for
Specifying Thermal Performance of Geothermal Power
1
Systems
This standard is issued under the fixed designation E974; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The following sections describe a guide for determining the thermodynamic excellence of
geothermal power systems. This guide may be used to establish and compare performance levels of
alternative geothermal plant designs using any resource conditions and is intended as a means for
supplying information in support of geothermal plant optimization.
It is also the purpose of this guide to encourage the common use of pertinent comparison criteria
for geothermal power systems, and to discourage the use of certain criteria which may range from less
useful to misleading.
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1. Scope power plants. Evaluation of geothermal systems using similar
definitions of thermal efficiency and heat rate is inappropriate,
1.1 This guide covers power plant performance terms and
except for plants which operate on a cycle, such as binary
criteria for use in evaluation and comparison of geothermal
plants. A utilization efficiency, defined as the ratio of net work
energy conversion and power generation systems. The special
output to the ideal work available from the geofluid, provides
nature of these geothermal systems makes performance criteria
a more equitable basis for evaluation of the thermodynamic
commonly used to evaluate conventional fossil fuel-fired
excellence of geothermal systems.
systems of limited value. This guide identifies the limitations
of the less useful criteria and defines an equitable basis for
3. Calculations
measuring the quality of differing thermal cycles and plant
3.1 Fossil Fuel-fired Power Plants—Thermal efficiency and
equipment for geothermal resources.
heat rate are useful and valid criteria for evaluation and
1.2 This standard does not purport to address all of the
comparison of fossil fuel-fired power plants. Thermal effi-
safety concerns, if any, associated with its use. It is the
ciency is the ratio of net work generated to the heat that is
responsibility of the user of this standard to establish appro-
theoretically available from the fuel. Conventional usage
priate safety, health, and environmental practices and deter-
within the electric generating industry defines thermal effi-
mine the applicability of regulatory limitations prior to use.
ciency (in dimensionless form) as:
1.3 This international standard was developed in accor-
η 5 3600/HR (1)
t
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
where:
Development of International Standards, Guides and Recom-
3600 = kJ equivalent of 1 kWh, and
mendations issued by the World Trade Organization Technical
HR = heat rate, the ratio of thermal energy supplied to the
Barriers to Trade (TBT) Committee.
net electrical output, kJ/kWh.
3.1.1 Forfossilfuel-firedpowerplantsheatrateisexpressed
2. Significance and Use
as:
2.1 Thermal efficiency and heat rate are frequently utilized
˙
to evaluate the thermodynamic quality of fossil fuel-fired
HR 5 m˙ 3FC⁄WHR (2)
f
where:
1
This guide is under the jurisdiction of ASTM Committee E44 on Solar,
m˙ = fuel flow rate, kg/h,
f
Geothermal and OtherAlternative Energy Sources and is the direct responsibility of
SubcommitteeE44.15onGeothermalFieldDevelopment,UtilizationandMaterials.
Current edition approved April 1, 2021. Published April 2021. Originally
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approved in 1983. Last previous edition approved in 2006 as E974 - 00 (2006) Kestin, J., DiPippo, R., Khalifa, H. E., and Ryley, D. J., “Source Book on the
which was withdrawn in January 2015 and reinstated in April 2021. DOI: Production of Electricity From Geothermal Energy,” DoE/RA/28320-2, U.S. De-
10.1520/E0974-21. partment of Energy, 1980, pp. 243–257.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E974 − 21
significant differences in auxiliary power requirements, and
FC = fuel higher heating value, kJ/kg, and
differing methods of providing auxiliary power, in the cases
W = net electrical output, kW.
being evaluated. This applies particularly to auxiliary power
3.1.2 Thermal efficiency and heat rate are applicable to
allowancesforventinggasesorfortransportingworkingfluids.
plants which operate on a cycle
...