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I wrote earlier today about grumbling at a Greenbuild session on life-cycle assessment, and I assigned the blame to bad news delivered by Stanley Rhodes of Scientific Certification Systems. The biggest shocker might have been Stanley's analysis that a given unit of electricity produced by wind resulted in increased greenhouse gas emissions compared with a unit of electricity produced by traditional fossil fuels (unfortunately he did not name the specific wind project analyzed). Because wind begins and ends abruptly and unpredictably, it delivers a fluctuating amount of electricity. Power companies therefore need to be prepared to spike the power grid with electricity from conventional power plants like those using natural gas. These plants need to be on "hot standby" to be ready for this spike, which is an inefficient way for them to operate, hence resulting in increased emissions, according to the analysis. If this is true, why would any power company use wind power? One answer would be renewable portfolio standards, which require a certain percentage of power from renewable sources. Another is customers who buy wind credits to "green their electricity" (discussed in the EBN feature article "Greening Your Electricity"). But I bet there's a lot more to this story.

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Comments

1 A great deal has been learned posted by Michael Goggin, AWEA on 08/27/2010 at 10:30 am

A great deal has been learned about this topic in recent years, with studies and data showing that the emissions benefits of adding wind energy are even larger than was commonly thought. We've summarized the results of these recent studies here:http://www.awea.org/newsroom/pdf/08-27-10-Wind_and_emissions_response.pdf

Michael Goggin AWEA

2 It seems the problem isn't in posted by James on 11/15/2007 at 10:27 am

It seems the problem isn't inherent with wind power but with the difficulty of matching supply to demand at a given moment. Fossil fuels are good for supplementing because they can be burned on demand, but supplementing is just one strategy. Another is storage. Wind power over a mean level could be stored for when wind levels drop, keeping energy from other sources at a constant level. Current battery technology has its own environmental drawbacks, but hydrogen holds promise for storage technology.

3 I would love to hear what you posted by Benjamin Tressler on 11/15/2007 at 10:19 am

I would love to hear what you find out about Stanley Rhodes analysis of wind power. His claims were disquieting and warrant further explanation.

4 I have great doubt that this posted by Alan Johnson on 11/15/2007 at 10:22 am

I have great doubt that this is true in the general case. I believe this assumes that fossil fuel plants are the only option available to compensate for the wind loads, and it also assumes that wind is supplying a significant percentage of the power to the grid. Given that grids tend to be regional (Vermont, for example, gets power from NH, MA, NY, near-by parts of Canada, and even further as needed), I doubt there are currently many places that fall into this category. So, an abrupt change in output from a wind farm (e.g. the wind speeds exceeds max the blades can handle of ~40MPH typically, some go higher), that would only represent a small fraction of total power on a regional grid, and is not likely to change the output required by near-by plants by more than 10 or 15%. So, even if the wind is at 100%, there is not likely to be a fossil fuel plant that goes on standby because of it, and if it did, there are plenty of sources to pull power from while it is starting up.

Now, one useful way to look at this is as a potential pitfall as wind power becomes more dominant on the grid. However, given the advances in energy storage systems of late, not to mention the techniques already in use, there is likely to be a cost effective solution to this before it is an issue. If only we could level the playing field by removing all energy subsidies and adding a carbon tax, cost effectiveness would be a none-issue.

Either way, wind, like any other green energy tech, is not a silver bullet, but it can be a big part of the solution with the current state of the art, not to mention recent advances that are yet to be prevalent in the market.

5 While it is entirely true tha posted by Steve Massey on 11/15/2007 at 04:34 pm

While it is entirely true that the output from individual wind turbines fluctuates with windspeed, it is incorrect to assume that there are no controls on modern turbines to account for this fluctuation in order to provide a stable source of current. Utilities must also retain a 'spinning reserve' in any case to compensate for system wide voltage fluctuations as the customer load on the system is likewise continuously fluctuating. To suggest that turbines leaving and entering service is a characteristic unique to wind systems is also erroneous as solar panels are in and out of service as clouds pass and night falls, and nuclear plants are offline for months at at time for repairs. Further, if I recall correctly, a Dutch study concluded that wind farms need only be separated by a few hundred miles to allow for reasonably predictable output from the total as the wind speed would be more likely to average between separate installations. Lastly, the wind speed may vary from second to second, but the generation speed of the wind can generally be forecast and monitored with reasonable accuracy.


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