Gas turbines / mikro turbines

Examples

Clean and efficient microturbines are state of the art for onsite power generation technology that can use natural gas, renewable or “waste” fuel gases to produce electricity and useful heat. Generally a gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. Microturbines are low maintenance efficient clean energy solutions. They are well suited for the smaller source of coal mine methane (30 kW to 250 kW) as they provide a modular approach to generating electricity close to the source gas, making beneficial use of other wise capped or vented methane and can reduce mine ventilation costs. Microturbines are commercially available and operate at 20% to 35% electrical efficiency for natural gas. Generally they are applicable for methane concentrations in the range from 40 – 100% and are able to convert more than 99% of the methane during operation of the gas turbine. Commercially available microturbines need a constant caloric value. Microturbines for fluctuating caloric values of CMM are commercially not available. Moreover, as gas turbines need compressed gas as fuel, CMM has to be compressed from nearly atmospheric conditions to operation pressure (6 to 20 bar). Therefore a compressor station is needed incl. all secondary structure like drying, dust removal and cooling system. Compared to reciprocating engines, microturbines have a very high power to weight ratio and are smaller when providing the same power rating. Moreover, they move in only one direction causing less vibration than a reciprocating engine and have fewer moving parts. Other benefits are the low operating pressures, the high operation speeds and the low lubricating oil cost and consumption.

Examples of use

• In Dortmund (Germany) at RAG Mine Gneisenau, a CMM-Turbine was set in operation in 1987 and after some damages and the closure of the mine shutdown several years later. The turbine utilized gas with a caloric value of 4.2 kWh/m3 and operated at a gas pressure of 12,5 bar leading out a power production of 3.285 kWbrutto and 2.672 kWnetto.

• City of Burbank Landfill, Burbank, California

City of Burbank Renewable Portfolio Standard requirement of 20% of power used by Burbank’s residents and businesses to come from renewable sources by 2017.

Further reading on microturbines

1. Joe Catina, “Beneficial Use and Reduced Emissions of Mine Methane, by Microturbine Power Generation”, 9/27/2006 http://www.epa.gov/cmop/docs/cmm_conference_sep06/ingersoll_rand_cmm.pdf

2. „GENERATING ELECTRICITY WITH COAL MINE METHANE-FUELED MICRO TURBINES”, EPA Coalbed Methane Outreach Program Technical Options Series, revised draft March 2004 http://www.epa.gov/cmop/docs/microturbine.pdf (2009-12-04)

3. „GENERATING ELECTRICITY WITH COAL MINE METHANE-FUELED TURBINES”, EPA Coalbed Methane Outreach Program Technical Options Series, draft November 1998 http://www.epa.gov/cmop/docs/018red.pdf