Econintersect: A common question raised about the incorporation of significant amounts of wind power centers because of the unpredictable and intermittent nature of wind and problems associated with efficiently utilizing wind as a component of supply to a larger electrical grid. Wind farm data from Great Britain may significantly address these questions.
Research, also published this year in the American Institute of Physics’Journal of Renewable and Sustainable Energy, has described the intricate level of detail in analysis necessary to avoid wasting power generated by wind turbines. From a summary of that research published by Warmageddon:
The new strategy is based on continuous predictions of how fluctuating winds affect each turbine’s maximum generation capacity. It also incorporates factors missing in other wind-farm control strategies, including differing power generation between turbines, actual fluctuations in power generation capacity, errors in prediction, communication disruptions preventing active control, and even turbines without the capacity for continuous active control. To demonstrate the feasibility of the new strategy, the researchers compared their predictions to raw data from a single wind turbine. The team then further refined their calculations and simulated a control operation with data from a wind farm of 33 turbines.
The results suggest that wind-farm managers can improve their power-generation efficiency with the new strategy. However, the researchers caution that before implementing the strategy, each wind-farm manager should adjust the underlying parameters – such as how often to adjust each turbine’s speed – based on local conditions.
While the research described above related to how to prevent the waste of energy production by wind turbines in excess of the grid demand, there is another efficiency concern. Energy can also be wasted if wind farm energy production falls below that expected by the grid and “emergency” energy production from other sources (such as fossil fuels) is required. The waste comes from having to maintain the “ready reserve” production because the wind is inconsistent.
The following data from UK National Grid bears on the question of unnecessary (inefficient) back-up for planned wind power production that fails to happen because the wind is “fickle”.
The level of excess power used because wind power production failed to meet the “forecast” output was less than 0.1% over an 18 month period of measurement.
This result indicates the amount of back-up power used during the 18 month period. So it bears upon the total amount of fossil fuel consumed, if that was the back-up source.
The result does not address the back-up capacity that must be maintained available on a standby basis. If all of the shortfall occurred in a single hour the back-up capacity needed would be 22 Gw. If it was evenly distributed over 100 hours, the standby required would be 0.22 Gw; or over a period of 1,000 hours standby 0.022 Gw. An 18 month period covers approximately 13,000 hours.
Without further breakdown of the data the capacity requirement for backup cannot be determined. The results from the three six-month periods is too small a sample (n=3) to attempt any statistical analysis. It may be tempting to say that the back-up capacity needed would never exceed 11 Gw (or some lesser number) but that cannot be done for two reasons: (1) we do not know the distribution of failures to produce over the 6 month period and (2) with only three samples we have no way of assessing the probability that a much larger number than 11 Gwh might occur in some future 6 month period from whatever the distribution of results would be for a large sample.
The important factors from these new reports are:
- The operational parameters of turbines in wind farms have been effectively modeled with regard to controlling the integration into power grids with control at the individual turbine level. This means that only limited amounts of turbine generated power will be wasted due to unneeded over production.
- The variability of wind has a very small impact on the use of back-up power. Limited inefficiency will occur because of failure to forecast underproduction from wind turbine sources.
Sources:
- National Grid report challenges wind energy critics (James Holloway, gizmag, 25 June 2013)
- The badger cull is no black-and-white issue (Geoffrey Lean, The Telegraph, 31 May 2013)
- Windpower: Consistently Inconsistent (But Still Awesome) (Warmageddon, 26 March 2013)
- An active power control strategy for wind farm based on predictions of wind turbine’s maximum generation capacity (Dewei Liu, Jianbo Guo, Yuehui Huang, and Weisheng Wang, Journal of Renewable and Sustainable Energy, 19 February 2013)
