Energy Power Plan Generating Resources Advisory Committee Past meetings

Draft New Resource Characterization for the Fifth Power Plan:
Natural Gas Simple-cycle Gas Turbine Power Plants

May 20, 2002

This paper describes the technical characteristics and cost and performance assumptions to be used by the Northwest Power Planning Council for assessments involving new natural gas simple-cycle gas turbine power plants. The intent is to characterize a typical facility, recognizing that actual facilities will differ from these assumptions in the particulars. We anticipate using these assumptions in our price forecasting and system reliability models.  The assumptions may also be used in analyzing the issue of maintaining adequate system reliability. Others may use the Council's technology characterizations for their own purposes.

Gas (?combustion?) turbine power plants are based on aircraft jet engine technology. A gas turbine power plant consists of a gas compressor, fuel combustors and a gas expansion turbine. Air is compressed in the gas compressor. Energy is added to the compressed air by combusting liquid or gaseous fuel in the combustor. The hot, compressed air is expanded through the gas turbine. The gas turbine drives both the compressor and an electric power generator. Gas turbine power plants are available as heavy-duty ?frame? machines specifically designed as stationary engines, or as aeroderivative machines - aircraft engines adapted to stationary applications. Aeroderivative machines tend to be more thermally efficient than frame machines, but more costly to purchase and operate. Stationary gas turbine technology development is strongly driven by gas turbine applications in the military and aerospace industries.

The principal environmental concerns associated with simple-cycle gas turbines have been emissions of nitrogen oxides (NOx) and carbon monoxide (CO). Noise has been a concern at sites near residential and commercial areas. Fuel oil operation may produce sulfur dioxide. Like other fossil fuel power plants, gas turbines produce carbon dioxide. Within the past decade, the commercial introduction of ?low-NOx? combustors and high temperature selective catalytic controls for NOx and CO, has enabled the control of NOx and CO emissions from simple-cycle gas turbines to levels comparable to combined-cycle power plants.

Because of the ability of the Northwest hydropower system to supply short-term peaking capacity, simple-cycle gas turbines have been a minor element of the regional power system. As of January 2000, about 900 megawatts of simple-cycle gas turbine capacity was installed in the Northwest, comprising less than 2% of system capacity. The power price excursions, threats of shortages and abnormally poor hydro conditions of 2000 and 2001 sparked a renewed interest in simple-cycle turbines as a hedge against high power prices, shortages and poor water. About 360 megawatts of simple-cycle gas turbine capacity has been installed in the region since 2000, primarily by large industrial consumers exposed to wholesale power prices and by utilities with direct exposure to hydropower uncertainty (including Bonneville slice customers).

The proposed reference plant is generally based on the 47 megawatt (nominal) General Electric LM6000PC Sprint gas turbine generator. Aeroderivative gas turbines such as the LM6000 have been the predominant type of simple-cycle machine installed in response to last year's price excursions, both in the Northwest as well as elsewhere on the western grid. Fuel is assumed to be pipeline natural gas. A firm gas transportation contract with capacity release capability is assumed, in lieu of backup fuel. Air emission controls include water injection plus selective catalytic reduction for NOx control and an oxidation catalyst for CO control. The machine is assumed to be located at an existing gas-fired power plant site and would therefore not require development of site infrastructure.

Issues:

• Is the assumption of firm gas transportation in lieu of backup fuel such as fuel oil or propane reasonable?
• We are assuming emission control levels comparable to those required of permanently sited simple-cycle units in California. Are these reasonable, or unrealistically stringent for the Northwest?  Would capital or O&M costs change significantly with less stringent environmental controls?
• The proposed forced outage assumption is much lower than those reported in the Generation Availability Data System. The average age of units represented in the GADS data is greater than 20 years and not believed to be representative of new units. The proposed forced outage assumption is based on monitoring of newer units (LM6000s). 
• In general, the proposed assumptions are those needed by the Council for its analytical efforts. Is there additional information that might be useful to others that we should include for this and other technologies?
• We have not assessed the availability of sites (i.e. potential capacity limits) because earlier capacity addition studies show little development of simple-cycle gas turbines.  However, simple-cycle gas turbines may be an economical approach to maintaining system reliability. How should we approach the issue of site availability and infrastructure requirements?    
• The capital cost estimate is based on a limited number of published cost reports. Can we assume that these ?Press release? costs are a reasonable basis for generic capital costs?

Table 1:  Resource characterization: Natural gas simple-cycle gas turbinepower plants