Performance Indicators for Geothermal Power Plants

Three performance indicators are needed to describe the technical performance of a geothermal power facility. All performance indicators are dimensionless and can be expressed as per cent. They are:

• Capacity factor
• Load factor
• Availability factor

The definitions of the technical performance indicators are:

 

Both the capacity and the load factor are needed. Where the capacity factor is approximately the same as the load factor, this is an indication that the installed capacity matches both the field conditions and the market conditions. On the other hand, where the capacity factor is significantly lower than the load factor, this is a sign that the installed capacity is too large either for the geothermal field or the market.

Due to the importance of highlighting the effects of Planned/Forced Outages, two separate Availability Factors must be determined, including or excluding the time lost during the Planned Outage with respect to the actual operating hours. 

The unavailability (%) of the plant (100 – availability factor) is split into two categories:

• Planned outage – An outage scheduled well in advance (at least two weeks) of theactual outage.
• Forced outage - Unplanned outage that requires the plant to be taken out of serviceimmediately or before the next planned outage.  

 

An alternative definition of Steam Availability Factor could derive from the following consideration: some generation may be lost due to a shortfall in steam supplied from the steam-field; measuring the steam supply at the turbine inlet (t/h), it is possible to define:

The Safety Accident Rate is defined as the number of accidents for all utility personnel permanently assigned to the Geothermal Power Facility, per 1,000,000 man-hours worked.
The Production Loss Control is the number of Forced Outage events per period per generating facility. Target and actual figures are reported on a monthly basis and summarized in the annual plant report.