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Thursday, May 29, 2008

Want 20 Percent Wind Power by 2030, Get to Work!

The U.S. Department of Energy’s (DOE) Wind program arm just released a report (PDF, 4 MB) on the prospect of wind power generating 20% of U.S. electricity by the year 2030. News agencies have reported on this result, though typically only by reading the official press release. USA Today did do some additional research and their coverage accurately reflects both the intention and the results of the DOE report. In the following discussion I will suggest that you thumb through the report by highlighting a few items I found interesting. If wind power is going to produce such a significant portion of U.S. electricity, then there is a lot of difficult work to do (and don’t get discouraged if it fails).

The report is not a prediction that wind energy will be our savior. It begins by stating that President Bush motivated an improvement in the nation’s energy diversity. Give the DOE credit for taking the Bush Administration’s Energy Agenda and putting some real numbers behind it. Reading through this 248 page report will get you completely up to date in terms of the steps necessary for wind power to generate as much as 20% of all U.S. electricity by the year 2030. It’s not an easy climb, however, so it is important that the public have realistic expectations to avoid becoming disenchanted with wind power if it ends up costing more than this report suggests.

Points of Interest

Page numbers given here are from the report itself. The corresponding page number of the PDF is 20 greater, e.g., for page number 33 cited below, you can find the referenced page as 53 in your PDF viewer.

  • Page 16: Power plants use more water than agriculture. There may be a technical issue because power plants withdraw more water than agriculture, but they might return enough of it that they actually consume less water than agriculture. Either way, wind farms use much less water than other types of power plants (this is an area in which nuclear loses dramatically) and could be developed to save 450 billion gallons of water annually. The southwest should consider that a huge benefit of wind power.
  • Page 31: There is a physical limit to the energy efficiency of a wind turbine. Betz’ limit is that at most, 59% of the energy associated with a free stream can be extracted. Basically, if you remove too much of the flowing fluid’s energy (air is a fluid here), then it stops in its tracks and prevents any more fluid from passing through. If no more fluid passes through, then no more energy can be extracted. If that is the bad news, then the good news is that “Modern utility-scale wind turbines generally extract about 50% of the energy in this stream below the rated wind speed”.
  • Page 32, Figure 2-8: A great plot that shows the wind speeds at which a turbine will turn itself on, reach its maximum efficiency, and turn itself off to avoid damage.
  • Page 34, Figure 2-9: The cost of operation and maintenance versus the age of the equipment for very large wind harvesting facilities (i.e., generation greater than 5 MW). There are large error bars for the equipment that was installed up to 6 years ago. For example, wind power that was completely installed four years ago has an operating and maintenance cost with a standard deviation of ± 75%! This means that such a facility cannot accurately predict their operating costs based on other comparable sites. There are very few qualifying sites, however, so the statistics are not so good in the first place. The 75% standard deviation is calculated after reviewing only 17 facilities. Maybe one of them was just horribly mismanaged.
  • Page 36, Figure 2-10: Good luck reading the axes on this figure. Did someone just scan it from a Whole Foods bag?
  • Chapter 2: It’s odd that there is so much information in the section on technology improvements because the turbines already operate at very high efficiency (see page 31 reference above). Still, improvements in efficiency also include electricity transport so we should push for continued development.
  • Page 47, Figure 2-16: This figure shows blade size versus time along with markers for the construction of facilities to test the blades. There are no facilities in the U.S. that can test blades longer than 50 m, though blades larger than this are becoming standard for the large scale wind farms in development. These tests are very important, but the report states that manufacturers cannot afford to each have their own facility. Hopefully, government support of such an infrastructure will become part of the plan. This does not sound like something that is getting much coverage in the present discussion.
  • Page 47: Here is a funny quote, “Because blades are approaching sizes of half the length of a football field and can weigh more than a 12.2-m yacht, they are very difficult and expensive to transport on major highways.” The football field comparison is good, but how many people have a concept of the weight of a 12.2 m yacht?
  • Chapter 3: Do we have the resources to implement 20% electricity generation by wind? We might not have enough fiberglass (page 72), “For example, the glass fiber requirements would be about half the level used domestically for roofing shingles (which is currently the largest consumer of fiberglass) and about double the amount now used in boat building.” Even worse, we might not have enough qualified people (page 73), “In a report published by the National Science and Technology Counsel (NTSC) in 2000, the percentage of 22-year-olds earning degrees in science and engineering will continue to drop in the next 40 years”.
  • Page 80, Figure 4-2: Qualitative plotting of the grid load over multiple timescales. On the timescale of days the load is fairly regular. As to be expected, the load fluctuates more rapidly over the course of minutes.
  • Page 84, Figure 4-6: This is a plot of voltage control features at a wind farm currently in operation by General Electric. Impossible to read if printed out. The PDF view is not much better.
  • Page 89, Table 4-3: This table displays the “capacity factor” of midwest energy production between June 2005 and May 2006, which is the percentage of energy actually produced by the method (out of the total energy possible). Nuclear produces the best by putting out 75% of the total it is capable of producing. Wind hits 30%, but the point of this table is to show that all energy sources are needed to ensure that enough electricity is generated. Nuclear energy is getting more positive press and will hopefully continue to develop right along with wind.
  • Offshore wind technology is not as advanced as that for land based wind farms. This might turn out to be an expensive development that will slow the progress of wind power collection.
  • Page 106: Not in my backyard! The public might be one of the problems that prevents wind energy from reaching the 20% point. “About 10% to 25% of proposed wind energy projects are not built—or are significantly delayed—because of environmental concerns. Although public support for wind energy is generally strong, this attitude does not always translate into early support for local projects.” One of the more popular examples of this involves a U.S. Senator trying to prevent the building of a wind farm in his favored sailing seas.
  • Page 112, Figure 5-2: Wind turbines kill fewer birds than house cats. An environmental argument against wind power (I’ve heard it, but do not have a reference handy) is that the farms kill too many birds. If we outlaw house cats, then this might become a valid argument.
Original here

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