Regarding the May 2007 article, “A Fuel Whose Time Has (Not Yet) Arrived”, you state that the technology has not yet arrived to utilize landfill gas as an energy source. That is simply not correct, the technology exists; it is the economics that have not yet fully arrived.
Although the issues brought up in the article about siloxanes are real and are problematic, they can be overcome. Landfill gas to electrical production is currently a very viable renewable energy source that is being used vastly and continues to become more and more prevalent every year. According to the U.S. EPA there are 284 landfills that are producing power from landfill gas in reciprocating engines, gas turbines or microturbines with a combined total output of over 1,000 MW. The top two reciprocating engine manufacturer’s have an installed base of over 300 reciprocating engines operating on landfill gas in the U.S. If you include No. 3 and 4 manufacturers there are well over 350 reciprocating engines operating on landfill gas.
The real issue that we find in the market is that in many parts of the country power is relatively inexpensive and landfill gas-to-energy projects have minimal subsidies to help offset the cost involved with installing these small scale power plants. Everybody wants their power to be inexpensive and when the competition is a nuclear power plant or a coal-fired power plant, landfill gas projects just are not economically competitive. In places where the price of power is high, which typically coincides with regions that rely on natural gas for a large portion of their power, that is where you will find a large percentages of the landfill gas being utilized to provide power into the grid. As the push for renewable energy continues and more states enact a renewable portfolio standards, you will see the push for the majority of landfills to utilize their gas.
Aaron Tasin, Operations Manager
Nixon Energy Solutions
I have drawn different conclusions from the same facts you presented in your editorial in the May 2007 issue regarding alternative gas “A Fuel Whose Time Has (Not Yet) Arrived. It may well be accurate to say that if one is burning alternative gas, turbosuperchargers and gas turbine’s time has not yet arrived. But naturally aspirated internal combustion engines have been burning coke oven gas since the 19th century.
I would recommend to your readers that if alternative gas becomes available to them, they go to the used engine market, because as Mr. Drees correctly pointed out, high maintenance is unavoidable. The appropriate conclusion is that new engines are not competitive. Also as Mr. Drees pointed out, clean gas is important. Turbosuperchargers should be replaced with systems like liquid ring compressors which can deliver clean gas.
My conclusions are reinforced by my company’s successful operation since 1992 of externally supercharged engines burning plant vent gas containing the objectionable impurities you and Mr. Drees mention. These engines generate electricity and replace an unsightly and inefficient flare.
If one takes an alternative gas-centered view rather than trying to force alternative gas into equipment designed for natural gas, one will find that alternative gas is quite competitive in today’s market.
Andrew K. Schwartz, Jr., Chairman
Keeshan & Bost Chemical Co.
A recent article, “Wind Turbines: Designing with Maintenance in Mind” (May 2007), points out three key points: namely problems with generator, gear boxes and human aspects of maintenance.
Gear box failure, if due to marginal design of large sun gear, can be easily upgraded with better components or materials used to make such components. My experience is that many gear box failures occur due to contamination and possibly poor or insufficient filtration.
I have worked with a few wind turbine manufacturers and they preferred to install two filters at the gearbox. Normally, they were small filters (properly sized for flow and pressure but possibly not for its contamination retained capacity) and they were 200 feet from the ground. I used to preach that if these filters were slightly larger to reduce change-out frequency and if they were brought to ground level then many problems associated with gearbox failures could either be eliminated or reduced.
The human aspect of maintenance is always a problem. Most people like to do their best, but if a person has to climb 200 feet 50 times it is not difficult to imagine that this person would be tired and that maintenance would suffer. That is why the idea of an elevator is a good one and laudable. Here, too, if the filters and pump/motor unit were brought to ground level, the maintenance of filters will be simplified.
I would recommend that wind turbine operators try this approach on 10 units for six months and if the results are favorable, retrofit other units to this configuration. Operators should also ask for this arrangement of filters and pump/motor unit on all their future procurement. Yes, it may be slightly more expensive at the outset, but in the long run they could avoid costly maintenance.
Abbey Vijlee, McKees Rock, Pa.
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