Many people debating greenhouse gas controls think they know that coal is our worst electricity source with respect to carbon dioxide emissions and that natural gas is about half as bad. Although replacing coal power with gas-fired power seems like an environmental winner, this simplistic generalization is often wrong. Eliminating coal-fired electricity will require replacing it with gas and because of the characteristics of our gas-fired stations, Ontario’s carbon dioxide emissions will rise.
This essay also addresses the suggestion from many environmental groups that Ontario should seek to maximize the use of gas in the form of high-efficiency cogeneration as opposed to mid-efficiency combined-cycle generators and low-efficiency simple-cycle generators. I note that the more cogeneration Ontario adds, the lower the potential penetration of wind power the power system can tolerate.
PDF of paper here:
Post Script: This posting was originally made July 5, 2009. Since then new gas combined cycle technology has emerged, such as the GE FlexEfficiency 50, that will reduce substantially the efficiency penalty of hybridizing wind and gas generation.
That’s the sad problem with coal, is that it has become the symbol of “dirty energy”, and people so much has hear the words coal and power in the same sentence, they think of big smoke stacks and black smoke comming out of them.
The idea that coal has environmental benefits relative to gas for backing up wind power is starting to get circulation.
The concept was picked up in a essay by Donald Jones in an article posted to a wind power blog site:
http://windconcernsontario.wordpress.com/2010/08/23/ieso-will-ontarios-wind-turbine-power-plants-reduce-greenhouse-gas-emissions/#more-14803
A shorter version of the Jones piece is forth coming in a Canadian Nuclear Society publication.
The Jone piece appears to have been an input to an opinion column in the Ottawa Citizen by Randall Denley which includes the comment, “Coal plants consume far less fuel (than gas plants) on standby.”
Read more: http://www.wind-watch.org/news/2010/09/04/those-political-winds-keep-blowing/
Based on the production cycle of some of the combined cycle gas units in Ontario over the last winter, I have some doubts about the assumptions I made in this piece about the minimum load characteristics of those units. Many days over the winter, units like Brighton Beach were operated with two pulses of full or nearly full power per day and two periods of no output. If this mode of operation can be sustained over the long term then gas would have a substantial GHG advantage over coal power during periods when dispatchable generation is needed on hot standby.