Another thing I’ve leaned about wind energy: when the output of a wind farm is expressed as, say, “30 MW,” that means that the combined output of the turbines has a theoretical maximum of 30 megawatts. Which is to say that on a perfectly windy day with all the turbines operating at perfect efficiency a 30 MW wind farm would be generating 30 MW of electricity. Of course perfectly windy days are few and far between, so the output of a 30 MW wind farm is more often than not less than 30 MW.
Setting that aside, here’s how the economics of the publicly-owned Eastern Kings Wind Farm work: Maritime Electric has a contract to purchase all of the energy the wind farm produces at a fixed price indexed to the consumer price index. Currently they pay $78 per megawatt hour (a megawatt hour being 1 MW of energy for one hour). So on a hypothetical perfect day the return to the public purse (not accounting for paying down the capital costs of the wind farm) would be:
30 MW x $78 x 24 hours = $56,160
And in a hypothetical perfect year – all wind, all the time – the farm would return $20,498,400. In reality, because reality is less than perfect, the return is less than that – electricity sales were last reported at $8.2 million/year. Here’s the summary of the Eastern Kings Wind Farm from the last annual report of the PEI Energy Corporation:
An objective for this year was to improve turbine availability at the East Point Wind Plant, and thus increase electricity production from the facility. This was accomplished. Despite replacing all ten gearboxes, machine availability improved to 89.4% as compared to 81.0% in the previous year. This increase in availability resulted in a 10% rise in energy sales, from 78,738 Megawatt-hours in 2008-09 to 86,779 Megawatt-hours. The only other major disruptions were the repair of switch gear in a turbine and the replacement of all three blades on another turbine.
A 30 MW wind farm has 262,800 (30 MW x 24 hours x 365 days) theoretical megawatt hours of energy it can generate, meaning that in 2008-2009 the farm was operating at 33% of “perfection.”