Category: Wind energy

Wind Energy In Scotland – What A Wind Farm Looks Like

I have just returned from eleven days in Scotland – one week as a Visiting Professor in the Engineering School at the University of Aberdeen and the remaining time visiting with my wife’s family in and around Glasgow.

Prior to heading to Aberdeen, shortly after arriving, I was kindly taken to see the Whitelee Wind Farm just outside Glasgow, an experience I am still savoring. A few pictures will illustrate why I was so excited by the visit – quite a change from the late 60’s and early 70’s when I first got involved with renewables:

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The Whitelee is Europe’s largest onshore wind farm, built in two stages to reach its current dimensions: 215 turbines (140/2.3 MW, 69/3 MW, 6/1.67 MW) with a maximum capacity of 539 MW. Wind energy is Scotland’s fastest growing renewable energy technology, reflecting the fact that Scotland is the windiest country in Europe (25% of all of Europe’s wind crosses the Scottish landmass and its surrounding seas). Scotland’s wind energy potential is estimated to be more than 150 GW onshore (current peak demand in Scotland is 10.5 GW) with significant opportunities for additional onshore and offshore development. Scotland’s offshore potential is estimated to be 206 GW and offshore wind power generation is predicted to be about 10 GW in 2020. As result, the Scottish government has set a target of generating 100% of Scotland’s electricity from renewable energy by 2020, with most of this likely to come from wind power. Scotland is also a world leader in development of wave and tidal power.

A few interesting facts about Scotland’s wind power resource:
– Scotland’s first offshore wind turbine was placed at the Beatrice Wind Farm in the North Sea in 2006 and was the world’s large wind turbine at the time – 5 MW. A second identical turbine was also installed and the wind farm began delivering electricity in 2007. Based on historical wind speed measurements it is expected that these turbines will run 96% of the time (more than 8400 hours per year) and at full power (10 MW) 38% of the time.
– based on averages a wind turbine in an EU country will operate at a 25% capacity factor. In Scotland, given the consistency of wind, it is expected that an average Scottish turbine will have a capacity factor of 35% or more. In fact, a small community wind farm in Shetland set a world record in 2005, achieving a capacity factor of 57.9%.
– About half of the UK’s current installed wind capacity is in Scotland.

This is all happening in the context of a vote next September in Scotland as to whether Scotland will separate from the UK and go out on its own as an independent nation. This is a complicated issue that is receiving extensive coverage in Scotland and the other parts of Great Britain, as well as elsewhere, and may be a nail biter until the vote is taken. An interesting fact is that Scotland is already an independent nation legally – the treaty that bound Scotland to England et al combined their parliaments but did not remove Scotland’s legal separateness. It will be an interesting debate for the next nine months.

Wind and Hydropower: A Natural Partnership

This blog was stimulated by an article published in the October 30, 2013 Washington Post: ‘Perfect’ winds blowing Brazil to new era of renewable energy (http://wapo.st/16nattl). It describes a rapid increase in Brazilian onshore wind deployments (the government’s goal is for wind turbines to supply “up to 10 percent of its generating capacity” by 2021) and quotes a Brazilian wind energy company president as saying “Wind is the perfect complement for the hydro base that we have in Brazil.” The purpose of this blog is to put increased focus on the too-little discussed importance of this natural partnership between wind and hydropower.

Hydropower and wind energy are closely related in that both are systems that use turbine blades to convert the kinetic energy of a moving fluid into electricity. In the case of hydropower the fluid is water and in the case of wind energy it is air. In both cases the energy available for conversion is proportional to the third power of the fluid speed V past the turbine – V squared from the kinetic energy in the flow and V from the rate at which fluid is moving through the blades.

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Wind energy is a variable (intermittent) renewable energy source that be used as an energy saver for fossil-fuel powered generating systems when the wind is blowing but requires some kind of storage of excess wind-generated electricity if it is to supply electricity at other times. Water reservoirs associated with hydropower dams serve as a natural “storage battery” for variable wind (or variable solar) as hydroelectric generators have short response/startup times as well as flexibility as to when water can be released to the generators from reservoir storage. The combination of wind and hydro thus provides a system capable of firming up power availability even when the wind is not blowing and reduces complementary water releases when the wind is blowing.

But this hybrid system has its limitations. It works extremely well as long as the wind component is not too large and the variations can be handled by the hydropower system’s flexibility. When wind generation gets too big that flexibility no longer exists or becomes increasingly expensive and excess wind energy must be utilized elsewhere. The U.S. Department of Energy’s Pacific Northwest Smart Grid Demonstration, underway in five Pacific Northwest states, is exploring options for addressing this growing problem.

A few more words about onshore wind (today’s dominant form of wind energy; offshore wind, an emerging technology, is discussed in an earlier blog on this web site) and hydropower, both of which are considered mature technologies.

Falling water first became a source for generating electricity in 1879 at Niagara Falls. Today hydropower provides about 20% of global electricity, with China, Canada, Brazil, the U.S. and Russia being the largest producers. There are about 78,000 MWe of hydropower generation capacity from 2,500 dams in the U.S. at present, with an additional 22,000 MWe in pumped storage capacity. Depending on rainfall and water availability, hydro provides about 6-7 percent of U.S. electricity and is currently the largest U.S. source of renewable electricity.

An interesting aspect of U.S. hydropower generation is that while further development of large hydropower projects is problematic (the best sites have already been developed) considerable potential exists for increased hydropower through development of new small and micro hydroelectric plants (59,000 MWe), development of new hydroelectric capacity at existing dams without hydropower facilities (17,000 MWe), and generation efficiency improvements at existing facilities (4,000 MWe).

Onshore wind energy capacity now totals more than 60,000 MWe in the U.S. and more than 300,000 MWe globally. Both numbers are growing rapidly. An interesting aspect of U.S. onshore capacity is the limitation imposed by existing highways – components for wind turbines beyond a given size (about 3 MWe) cannot be accommodated by existing roads. In principle the bigger the wind turbine the better the economics (ignoring the visual and noise impacts), a major argument for putting wind turbines offshore where size is not limited and other impacts are mitigated. One response being examined is manufacturing turbine components (towers, generators) in place using movable manufacturing systems.

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In sum, hydropower and wind energy are important sources of renewable electricity with significant growth potential individually and as hybrid partners. Both will be important parts of our inexorable march to a renewable energy future.