An Alaska case study: Diesel generator technologies

Abstract

Diesel generators are the main source of electrical generation in remote Alaska communities; they also help to maintain grid frequency and voltage. In an analysis of key performance metrics for diesel generators in Alaska, we found that the size of the installed system directly affects capital costs, that is, larger systems are more cost-effective per kilowatt. However, appropriately sizing a system for a community is more cost-effective overall than significantly oversizing the system. Capacity factors range from below 5% to over 25%. The low values are typically for diesel-hydroelectric hybrid systems, for which this measure is not entirely accurate. In addition, rural diesel plants may have low capacity factors since typically there are three to four generators in-house. These generators are sized so that one to two generators provide power at any given time; the remaining generators are available as backup. Generators of this size can be expected to operate for approximately 60 000–100 000 h, with larger engine blocks tending to have longer lifespans. An appropriately maintained generator operating for 35% of the time will last approximately 20 years, or 60,000 hours. The technology continues to see advances in power output, efficiency, noise reduction, and emission control. The shapes of combustion chambers in newer engines are designed to maximize the combustion rate of fuel, thus increasing output power and fuel efficiency. The common-rail fuel system can maintain high pressure from the fuel tank to injection, which allows for finer vaporization of fuel and more complete combustion. Nitrous oxide can be reduced through exhaust gas recirculation and selective catalytic reduction. Control systems have also seen advancement. Mechanical control systems have been slowly phased out in favor of electronic control systems, which allow for offsite monitoring of a system and reduction in the number of necessary service calls. Diesel generators in rural Alaska communities remain difficult to maintain to the degree necessary for smooth operation. Additionally, supervisory control and data acquisition systems with remote control capabilities require continuous Internet connection, which is not always available in rural communities.