DRAFT

Northwest Power Planning Council
New Resource Characterization for the Fifth Power Plan

Reciprocating Engine Generators for Peaking and Emergency Service

May 16, 2002

This paper describes the technical characteristics and cost and performance assumptions to be used by the Northwest Power Planning Council for assessments involving reciprocating engine generators for peaking and emergency service. 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 price forecasting and system reliability assessment 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.

Reciprocating engine-generator sets are a mature technology, extensively used in transportation and remote power supply applications. The basic technology has been central to the automotive industry for a century. The automotive industry has driven significant improvements in the power density, efficiency and emissions characteristics of reciprocating engines in recent decades.

The role of reciprocating engine-generator sets in the western electricity grid has been limited until recently. Engine-generators have been used for standby and peaking power service in scattered locations, for power production using landfill and other biogases and for small combined heat and power (CHP) applications. The latter are fairly common in areas such as California with historically high retail rates and CHP incentives. The prominence of reciprocating technology increased significantly during the 2000 - 2001 power price excursions as utilities and large retail users sought alternative sources of power by installation of modular generation   Most of these installations consisted of batteries of reciprocating engine-generator sets. Though many installations were temporarily permitted and were dismantled once power prices moderated, some were developed as permanent installations.

Reciprocating engine-generator sets include compression ignition (diesel) units and spark-ignition machines designed to operate on natural gas.  Compression-ignition machines generally operate on liquid fuels, principally distillate fuel oil, though large low-speed machines can operate on residual fuel oils. Spark-ignition machines are designed to operate on gaseous fuels including natural gas, propane, refinery and other industrial waste gasses, biogases and synthetic gasses. Though based on the same basic block as compression-ignition engines, spark-ignition designs operate at a lower compression ratio. This reduces the power density, resulting in somewhat greater cost per unit output. Low-cost gen-sets based on automotive engines are available for limited-duty applications. Machines intended for continuous duty are based on more costly, heavier railroad and marine engines. Because tuning for optimal efficiency and for minimum emissions is not coincidental, machines are often available in separate high-efficiency and low emission configurations.

We propose to characterize two types of facilities:  One type of facility consists of compression-ignition units fuelled by distillate fuel oil stored on site. This configuration could be used at interconnection locations remote from natural gas service, and for applications requiring short development time. The second type of facility consists of spark-ignition units fuelled by pipeline natural gas. This configuration could be used at interconnection points near to natural gas service and in areas where air quality is of particular concern.

Issues:

• Need to determine if low-sulfur premium should be attached to base case fuel oil price forecast.
• We are assuming no future improvement in thermal efficiency or cost.  Is this a reasonable assumption?
• O&M costs are based on limited information and may not include the cost of SCR NOx control. Do the assumed costs need to be modified?

References:

Caterpillar (1996):  Caterpillar. Generator Set 3516B Continuous Power. 1996.

EPA (2002):  US Environmental Protection Agency. Technology Characterization:  Reciprocating Engines.  February 2002.  Prepared by Energy Nexus Group.

Table 1:  Resource characterization: Reciprocating Engine Generators for Peaking and Emergency Service