Power Consumption

It might seem intuitive that turbines must produce a lot more power than they consume, but without actual numbers, who really knows? It is fairly easy to find out how much power is being generated by most wind farms. What is so far been impossible is to find out how much power they consume during their operation. So far I’ve looked for information on both wind farm and individual turbine consumption and have found nothing. Without this information it is impossible to know how much of a contribution a wind farm actually makes to the grid, and this in turn affects the calculations of CO2 savings and so on.

The turbines do not use the power they produce to power themselves; instead they are connected to either the existing grid just like any other utility user or to their own distribution system from a substation. I presume the power they use is metered and the project pays the power company for it just like you and I do, so the numbers I’m looking for should be readily available. If the usage isn’t metered (and I’ve read of such cases, amazingly) then pretty much the true value of the entire project is unknown. UPDATE – Early on CanWEA apparently got a deal [there was a nice 30-minute radio program on CKNX but it has been pulled] with the Ontario government that whatever electricity is used by a project is supplied free of charge. Whether it is metered or not I don’t know.

It turns out that turbines might use a surprisingly large amount of power. A quick and probably partial list might include: computers, lights and sensors, motors that control the pitch and direction of the blades, keeping the nacelle at a proper temperature and energizing the electromagnets in the generator. Additionally, it seems that the blades won’t tolerate remaining still for any length of time, so during extended calm periods they must be rotated using power from the grid. I found one guess that this input might be 10% of the rated output; in other words, about a third of the actual output. As I find any real information about this I’ll post it here. In the meantime, if anyone out there has any insights to this, please let me know.

UPDATE, March 24, 2009. I finally saw a number! 15,000kw-hr per turbine per year, which averages out to 1700 watts, roughly equivalent to 2 smaller homes. It was from an economist who works for the Danish Wind Industry, so I’m assuming it is accurate, although I’d (of course) like to see reports of actual measurements. Plus there’s certain other aspects of the article that are problematic and as a result I’m suspicious of the entire thing. Assuming a typical turbine generates 3000-4000 mw-hr in a year this isn’t such a large deal.

3 thoughts on “Power Consumption”

  1. This myth of wind power dies hard. Wind turbines have batteries or capacitors that they charge as part of their normal operation for their electrical systems’ use. Their name plate capacity is their net capacity. They don’t use grid power.

    In assessing this, I first read through critiques of wind energy to determine if any quantitative work had been done. I found one site that is used as the source of misleading statements regarding consumption of electricity by wind turbines by anti-wind advocate Eric Rosenbloom. Other anti-wind advocacy sites referenced Mr. Rosenbloom’s AWEO site uncritically and did not add any substantiation. Mr. Rosenbloom’s sources are an unnamed Swedish graduate student on a defunct discussion forum and unlisted personal correspondence.

    On the other hand, wind turbine producers have a vested interest in full lifecycle cost assessments and publish these. For example, I will use material from Vesta, on their LCA for their 3.0MW onshore and offshore wind turbines. This and other LCAs are published and available. These LCAs following manufacturing standard ISO 14040-14043 approaches to costing and are independently reviewed by Force Technology, a firm engaged for that purpose by Vesta.

    Electrical consumption during operation is not listed, although every other form of energy during manufacturing, construction, use and decomissioning is listed. That’s not because they are hiding it, it’s because it doesn’t exist.

    References, analysis, excerpts and an interesting graphic are here.
    http://www.quora.com/What-is-the-ratio-of-consumption-to-production-on-an-average-windmill-over-the-course-of-a-year

  2. Mike, I sometimes wonder if your main goal with this type of comment is to simply waste my time looking up the facts needed to settle the matter. You say wind turbines don’t use grid power. This is nonsense. You say their name plate capacity is their net capacity. This is also nonsense. My references? The Vestas General Specification for their V100-1.8 turbine, sections 9.11 and 3.11 respectively. You say they have batteries, and they do – to keep the UPS going for the controller (30 seconds worth!) and safety systems (35 minutes worth!). Hardly enough to last through a calm spell, eh? My reference? Section 3.8.

    You mention that you couldn’t find any quantitative numbers. Apparently you didn’t accept the Rune letter that was linked to in my posting, and which stated the average consumption was 15,000 kw-h per turbine per year. Or maybe you didn’t notice the WI Shoals Economic Impact Study, which gives an indication that about 135,000 kw-h are used per turbine per year.

    Your “on the other hand” paragraph tells me you are inclined to uncritically accept everything the wind industry publishes. Are you this credulous with other industries? Their “vested interest” with the LCA numbers is to present the lowest possible numbers that can be plausibly defended, not to publish honest numbers. Just like any other industry.

    My main points were that the consumption numbers didn’t look that large, but without a public accounting we’ll really don’t know. Nothing you’ve said changes my conclusions.

  3. University of Minnesota at Morris has wind productioin and research data on their

    1.65 megawatt Vestas NM 82.

    http://renewables.morris.umn.edu/wind/research

    There’s raw hourly and daily production both positive and negative although it doesn’t explain where the negative comes from – the worst negative occur when then wind is light and variable. At 0 wind speed winter negative production is twice the negative production of summer. I believe the Morris facility is off the main grid and so the negative production would not be “free” to them.

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