Wednesday, May 31, 2006

Wind integration follies

At the end of 2005, the Power Engineering Society (PES) of the Institute of Electrical and Electronic Engineers (IEEE) published a special issue of its Power & Energy Magazine (Volume 3, Number 6, November/December 2005) focused on integrating wind into the power system. This document provides a brief summary of many of the salient points from that special issue about the current state of knowledge regarding utility wind integration issues.
The May 2006 report ("Utility Wind Integration State of the Art") prepared by the Utility Wind Integration Group (UWIG) has been frequently cited recently as showing that wind power can easily provide 20% of our electricity. In fact it doesn't say that at all. Even their own press release misrepresents the report in that way.

The report does constructively address some of the market structures that complicate integrating a variable and intermittent source of energy such as that from the wind, but it glosses over the fact that such integration has little effect on the use of other sources. Even as it notes that wind is an energy, not a capacity, source -- that is, it can't replace any other source of electricity on the grid, it disregards the costs of keeping that excess capacity on line and using it all that less efficiently, nor does it consider the madness of, for example, calling for building excess, redundant, wind facilities in the dim hope that somewhere the wind will be blowing and for more transmission lines to deliver this marginally useful energy -- instead of spending that money to better use what we already have (or even, damn your eyes, to use less energy).

It also inconveniently declines to provide the sources it refers to ("two major recent studies," "have been shown," "one major study"), instead simply referring to the P&E Magazine. So one reads the UWIG summary with no idea of the reliability of its sources. Here are some extracts, with commentary in brackets.
On the cost side, at wind penetrations of up to 20% of system peak demand, system operating cost increases arising from wind variability and uncertainty amounted to about 10% or less of the wholesale value of the wind energy.
Besides obviously ignoring the cost of the wind plant itself and its supporting transmission infrastructure, it should be noted that this is about cost only. As noted above, the publicizers of the UWIG report have misread this to say that the problems of integrating that amount of wind energy are minimal and even that there are corresponding benefits. But nothing in the UWIG report says that.
Since wind is primarily an energy -- not a capacity -- source, no additional generation needs to be added to provide back-up capability provided that wind capacity is properly discounted in the determination of generation capacity adequacy. However, wind generation penetration may affect the mix and dispatch of other generation on the system over time, since non-wind generation is needed to maintain system reliability when winds are low. [That is, wind does not need new back-up capacity, because it should be generally ignored in capacity planning, anyway (since the wind will be low so often).]

Wind generation will also provide some additional load carrying capability to meet forecasted increases in system demand. This contribution is likely to be up to 40% of a typical project’s nameplate rating, depending on local wind characteristics and coincidence with the system load profile. [Utter fudge. First, typical generation reported to the EIA is 27%. Second, that "depending on" is the starting point of the problem not a minor sideshow.] Wind generation may require system operators to carry additional operating reserves. [Just don't call it new back-up!]

In areas with limited penetration, modern wind plants can be added without degrading system performance.
And there's the crux of the matter. What is "limited penetration"? It certainly isn't 20% of peak demand. As long as wind penetration is low enough so that its variability can be accommodated as easily as demand fluctuations, it doesn't present a problem. And that limits the possible contribution wind power can make to meeting our electricity needs.
Because of spatial variations of wind from turbine to turbine in a wind plant -- and to a greater degree from plant to plant -- a sudden loss of all wind power on a system simultaneously due to a loss of wind is not a credible event. [Hogwash. It is wishful thinking (and more madness: to build more wind turbines to back up other wind turbines, further diminishing their usefulness) and it is not at all borne out by actual experience.]

The addition of a wind plant to a power system does not require the addition of any backup conventional generation since wind is used primarily as an energy resource. In this case, when the wind is not blowing, the system must rely on existing dispatchable generation to meet the system demand.
This contradicts the earlier statement that "[w]ind generation will also provide some additional load carrying capability to meet forecasted increases in system demand." It states that wind has no -- zero -- capacity credit. In other words, it is not a choice between wind turbines and smokestacks or cooling towers. Erect and connect all the wind turbines you can, and you'll still need the same amount of "conventional" plants.
The addition of a wind plant to a power system increases the amount of variability and uncertainty of the net load. This may introduce measurable changes in the amount of operating reserves required for regulation, ramping and load-following. Operating reserves may consist of both spinning and non-spinning reserves.

Wind’s variability cannot be treated in isolation from the load variability inherent in the system. Because wind and load variability are statistically uncorrelated, the net increase of variability due to the addition of wind is less than the variability of the wind generation alone. [Nonsense: The addition of times of high wind generation during low demand (and, to a lesser extent, since wind has zero capacity credit, vice versa) obviously increases load variability.]

Upgrades or additions to transmission facilities may be needed to access locations with large wind-energy potential.
For more information on the actual contributions of wind power and its effect on other sources, see "The Low Benefit of Industrial Wind."

wind power, wind energy, environment, environmentalism