Packaged cogeneration

< needle>By the grace of God< /needle> Kathy Kinsley has led me to this item about a company that is building rooftop power plants on commercial buildings.

The article doesn't give a lot of detail, but it appears that they are doing something called cogeneration. With cogeneration, you generate electric power, but you also use some of the waste heat from the prime movers (usually gas turbines) for heating rather than rejecting it to a heat sink like a river, lake or atmospheric cooling tower. The result is improved thermal efficiency - more delivered power per unit of gas consumed.

There are other benefits also. There is more diversity of supply for electric power. Capital, operation and maintenance costs can be reduced with standardized designs and training. And as an engineer with a strong IT background, I like technologies that leverage both - such installations require sophisticated control systems.

There is a downside, however. One nice thing about remote powerplants is that any pollution is deposited far from the point of consumption. And the real cost of pollution is a strong function of where it is deposited. I'm not sure places like LA need any more heat or exhaust gases around - other locales such as Ontario may be far better.

The prime movers, which provide the heat and drive the generators, run on natural gas. Presumably any cost savings would result in part by buying natural gas in long-term contracts. I have to wonder if the existing gas distribution infrastructure can handle large-scale application of this. This could require major capital investment in places that are hostile to such development.

Also, although absorption chillers can use waste heat to provide cooling for air conditioning, it's difficult to balance the power and cooling demands. The difference presumably would be made up by buying more power from other utilities. The result will be a system that reduces the base load for power without doing much to reduce the maximum loads. And it's the costs at the maximum loads that cause the grief.

So I'm not sure we'll ever see really wide application of this in places like California, where the initial sites are. Ontario may be different. It will be interesting to watch.