Renewable electricity production, from sources such as wind power and solar power, is sometimes criticized for being variable or intermittent. However, the International Energy Agency has stated that deployment of renewable technologies usually increases the diversity of electricity sources and, through local generation, contributes to the flexibility of the system and its resistance to central shocks.

There have been “not in my back yard” (NIMBY) concerns relating to the visual and other impacts of some wind farms, with local residents sometimes fighting or blocking construction. In the USA, the Massachusetts Cape Wind project was delayed for years partly because of aesthetic concerns. However, residents in other areas have been more positive and there are many examples of community wind farm developments. According to a town councilor, the overwhelming majority of locals believe that the Ardrossan Wind Farm in Scotland has enhanced the area.

The market for renewable energy technologies has continued to grow. Climate change concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization. New government spending, regulation and policies helped the industry weather the 2009 economic crisis better than many other sectors.

Adapted from the Wikipedia article Renewable energy debate, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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According to Campbell:

* There are no new potential oil fields sufficiently large to reduce this future energy crisis.

* The reported oil reserves of many OPEC countries are inflated, to increase their quotas, or improve their chance of getting a loan from the World Bank.

* The practice of gradually adding new discoveries to a country’s list of ”proven reserves”, instead of all at once, artificially inflates the current rate of discovery.

In 1989 Campbell claimed that there would be a shortage towards the late 1990s. In 1990 he claimed that 1998 would represent a “depletion midpoint.” These early assessments were, however, according to Campbell himself, “based on public domain data, before the degree of misreporting by industry and governments was appreciated.” Since that time, Campbell has been predicting that the peak of oil production will cause a catastrophic worldwide economic depression.

One theory, held by many in the oil industry and the United States Department of Energy , is that oil production will continue to increase, due to technological advances and the geopolitical pressure caused by rising oil prices. They argue that:

* Much of the world’s oil reserves come from areas that have not been fully explored because they are politically unstable, like Russia and Iraq. Nobody knows how much oil is really left in those areas, and economic pressure could result in a new exploration boom.

* New methods of extracting oil from existing fields are currently being developed. This may even expand the definition of “oil”: Hydrocarbons exist in shale and tarry sands, and as a result companies like Exxon predict that there are up to 14 trillion barrels (2,200& km³) of exploitable hydrocarbons left in the world, which could fuel the oil industry for another century.

The U.S. Department Of Energy report ”Peaking of World Oil Production: Impacts, Mitigation, and Risk Management”, often referred to as the ”Hirsch Report”, proposes an urgent mitigation approach to deal with the possibility of oil production going into decline in the immediate future.

It states: “The peaking of world oil production presents the U.S. and the world with an

unprecedented risk management problem. As peaking is approached, liquid fuel prices and price volatility will increase dramatically, and, without timely mitigation, the economic, social, and political costs will be unprecedented. Viable mitigation options exist on both the supply and demand sides, but to have substantial impact, they must be initiated more than a decade in advance of peaking.”

The current debate in the U.S. revolves around energy policy, and whether to shift funding to increasing conservation measures, fuel efficiency, and other energy sources such as wind power, solar power, hydropower, and nuclear power.

Campbell has previously predicted production peaks which have not realized, some people are criticizing his methods because of that.

Adapted from the Wikipedia article Colin Campbell (geologist), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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There are isolated wind turbines at Brooklyn and Gebbie’s Pass. At the Te Rere Hau wind farm there are five 500KW wind turbines, however the transmission line to the rest of the electricity grid is limited to one megawatt. The horizontal layering shows the effect of a single turbine (or a small number of turbines) running at their maximum output. For Te Rere Hau however, the graph suggests that this maximum setting is about 200KW, not the nominated 500KW.

The Hau Nui wind farm has an intermediate capacity…

While south of the Manawatu Gorge the Tararua wind farms operate almost in synchrony. Construction of the Tararua III wind farm began in early 2007, but after winter some turbines became u/s.

North of the Manawatu Gorge is the Te Apiti wind farm, while in Southland the White Hill wind farm began operation.

Combining all the wind generation shows that the total production was uneven over the year due to variations in capacity.

By contrast, the Clyde hydro power station (for example) has its generation timed to suit demand, likewise the New Plymouth thermal power station – which was deactivated in October 2007, until the resulting power shortages in 2008 encouraged its partial reactivation.

Availability over a year

An important consideration for the organisation of an electric power generation system is the availability of power from its various components. Hydro power stations with a reasonably large lake can be started and stopped at will, while thermal power stations are controllable also, though cycling between hot and cold causes wear and is to be avoided. Wind turbines of course generate only at the whim of the wind, so the question becomes “How often does the wind blow at useful rates?” From the viewpoint of the electricity system, this becomes “How often does the generator deliver various levels of power?”

This can be assessed via consideration of the “duration” curve, of power vs. the proportion of time at (or below) that power, derived from the observed generation data for some interval such as a year. Specifically, given measurements at regular intervals (half-hourly is usual in NZ), as were used to produce the plots of generation, sort a year’s 17520 values into the order lowest power to highest. A plot of the power as the y-variable and the index of the value’s position as the x-variable produces curves such as follow.

For wind power, there is no controllability, except in design choices as to wind speeds for start and stop, so the power output is closely connected to the wind speed.

These curves are rather disappointing. For Te Rere Hau for example, the top tenth of the time for generation involves a power drop of two tenths. Half the time, the generation is less than 25% of full capacity. For about forty percent of the time the generation is less than ten percent of nominal capacity, a level that is hardly worth the trouble and it is zero for about a quarter of the time. Since the timing of the pattern of demand for electricity is not much correlated with the wind, this means that at any particular time of high demand, it will be unlikely that wind generation is operating at high power.

Perhaps a wind farm with many turbines and unconstrained by transmission line capacities will do better: here is the curve for the Hau Nui wind farm

And the Tararua wind farms, distorted by the increase of capacity for Tararua III during 2007.

And Te Apiti (north of the Tararua wind farm) along with White Hill in Southland which commenced operation in 2007.

And for all wind combined, distorted by the changes in active capacity during 2007:

The combined curve is ”not” the summation of the individual duration curves; rather, for each time the values for the wind-powered generation at that time were added, and the sort performed on the sum. Despite the geographical spread, it is clear that at any given time, there is a high chance that the contribution from wind generation will not be a large proportion of the installed capacity. For instance, half the time, it will be no more than a third, and only a quarter of the time will it be above two thirds.

Correlation between different locations

So the next question is just how much correlation might there be amongst wind power installations at different locations? Perhaps when the wind fails to blow at one location, it might blow at another. This can be assessed by considering scatter plots where a point is placed for each measurement of the year according to station A’s generation at that time for the ”x” co-ordinate and station B’s generation for the ”y” co-ordinate. A fair comparison would be amongst stations that have not changed during the year, so this means that White Hill and Tararua III that were under construction in 2007 must be excluded. A later time span could be used when they have settled down, but incompetence within the electricity commission has meant that data for wind generation (and many other smaller generation stations) is no longer being received.

Scrutiny of the generation plots shows that the adjacent wind farms Tararua I and II are steady (and almost the same), and Te Apiti, on the north side of the Manawatu Gorge is likewise steady. So for two nearby wind farms,

This shows that the two operate almost as one. Further, when the wind is strong north of the gorge it is also strong south of the gorge, and vice-versa. The lone wind turbine at Brooklyn above Wellington is rather further away, and unlike Hau Nui, the Rimutaka mountain range intervenes between it and Te Apiti.

This shows very little correlation, though still when the wind is strong (or weak) at one location it is likewise at the other. The obtrusive horizontal spacing is a consequence of the data supplied being given only to a 2KW step even though the full scale value is just 230KW and the metering is good to one part in ten thousand.

Much further away is the lone wind turbine at Gebbie’s Pass by Christchurch.

Which shows no correlation. However, times when there was no generation at both locations would not be well-depicted in this display.

By contrast, the Clyde hydro power station has controllable generation. It has four turbines and the steps in the duration curve show that one, two, three or four turbines (but not which individual turbines) were operating at their nominal output for various portions of the year. Thus, the Clyde power station was not generating at all for about a twentieth of the year (zero power up to about 0.05 of a year) and ran one turbine only for about a tenth of a year, the flat between 0.1 and 0.2. A hydro turbine is at its most efficient only near its design capacity and the flow of water is controlled accordingly. However, the power output can be varied a little (and the water pressure varies with lake level), so the “flats” of the staircase are not completely flat, nor the risers vertical. For new Plymouth, for two thirds of the year’s half-hours it was not running at all.

Now, it is true that a hydro power station does not operate at a hundred percent all the time, but this is not the same thing. Clyde runs at about 60% of its capacity, but this is because a hydro power station typically has more generation installed than could be supplied by the annual average flow of its river. Given that a hydro power station is being built, an extra generator is not much further expense. The difference is that the excess generation can be started or stopped as the demand for electricity varies, with the water reservoir either falling or rising correspondingly, but averaged over a long period the flow through the generators matches the river’s actual flow since otherwise the lake will overflow or be drained. With wind turbines there is no storage of wind for other times of greater need. Thus a hydro power station has good availability (for any given half-hour) while a wind power station does not, even if both offer about the same ratio of average power to maximum power over a year.

Adapted from the Wikipedia article Wind power generation in New Zealand (2007), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Positioned 370 metres (1200 feet) above sea level and 15 kilometres (9 miles) outside Glasgow, Scotland’s largest city, the wind farm has over half a million people living within a 30 km radius. This makes Whitelee one of the first large-scale wind farms to be developed close to a centre of population. In May 2009, Whitelee was officially opened to the public by Alex Salmond MSP, First Minister for Scotland. However, Whitelee was generating power long before this with the first phase of the wind farm supplying power to the electricity grid in January 2008.

In May 2009, the Scottish Government granted permission for an extension to the wind farm that will produce up to a further 130 megawatts of power,

which would increase the total generating capacity of Whitelee to 452 MW. There is also the potential to increase the generating capacity once again by 140 megawatts. This would give Whitelee the potential to generate almost 600 megawatts of renewable energy.

The Scottish government has a target of generating 31% of Scotland’s electricity from renewable energy by 2011 and 50% by 2020. The majority of this is likely to come from wind power.

On 19 March 2010 a blade snapped off a turbine, resulting in temporary suspension of operations until safety checks were completed. Following the accident Keith Anderson, managing director of ScottishPower Renewables, said: “This type of incident is exceptionally rare and highly unusual.”

Adapted from the Wikipedia article Whitelee Wind Farm, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Wind power is derived from uneven heating of the Earth’s surface from the Sun and the warm core. Most modern wind power is generated in the form of electricity by converting the rotation of turbine blades into electrical current by means of an electrical generator. In windmills (a much older technology) wind energy is used to turn mechanical machinery to do physical work, like crushing grain or pumping water.

Hydropower is energy derived from the movement of water in rivers and oceans (or other energy differentials), can likewise be used to generate electricity using turbines, or can be used mechanically to do useful work. It is a very common resource.

Geothermal power directly harnesses the natural flow of heat from the ground. The available energy from natural decay of radioactive elements in the Earth’s crust and mantle is approximately equal to that of incoming solar energy.

Alcohol derived from corn, sugar cane, switchgrass, etc. is also a renewable source of energy. Similarly, oils from plants and seeds can be used as a substitute for non-renewable diesel. Methane is also considered as a renewable source of energy.

Adapted from the Wikipedia article Renewable resource, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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By the 14th century Dutch windmills were in use to drain areas of the Rhine River delta.

Adapted from the Wikipedia article History of wind power, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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The actual effects of removing fossil fuel subsidies would depend heavily on the type of subsidy removed and the availability and economics of other energy sources. There is also the issue of carbon leakage, where removal of a subsidy to an energy-intensive industry could lead to a shift in production to another country with less regulation, and thus to a net increase in global emissions.

Policy suggestions

Jacobson and Delucchi (2009) have advanced a plan to power 100% of the world’s energy with wind, hydroelectric, and solar power by the year 2030, recommending transfer of energy subsidies from fossil fuel to renewable, and a price on carbon reflecting its cost for flood, cyclone, hurricane, drought, and related extreme weather expenses.

Adapted from the Wikipedia article Economics of climate change mitigation, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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After years of contentious debate, the proposal was voted down by the LURC in 2007. The summit of Redington was seen as too ecologically sensitive — a sub-alpine fir habitat providing a home for two rare species, the bog lemming and Bicknell’s thrush. Also, the development would have been visible for miles along the Appalachian Trail (AT).

A revised proposal, for 18& turbines only on Black Nubble, was put forward by MMP, supported by many environmental groups, but still opposed by Maine Audubon.

The project was rejected by the LURC in 2008.

Adapted from the Wikipedia article Wind power in Maine, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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In 2007, UK wind farms achieved “load factors on an unchanged configuration basis” of 27.3% for onshore and 28.3% for offshore respectively.

In 2008 onshore farms achieved 29.4% and offshore farms achieved 34.9% on the same basis. A study by the Renewable Energy Foundation (REF), which campaigns against the use of wind energy in the UK, claimed that only a few Scottish wind farms achieved the 28% average, while turbines in lowland England were operating at much lower levels, some at less than 10% of capacity.

There is also much dispute over the necessary amount of reserve or backup required to support the large-scale use of wind energy due to the variable nature of its supply. The opponents of wind energy argue that it is necessary to have up to 80–90% backup, however National Grid which has responsibility for balancing the grid reported in June 2009 that the electricity distribution grid could cope with on-off wind energy without spending a lot on backup.

Adapted from the Wikipedia article Wind power in the United Kingdom, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Although the waters off the Atlantic coastline of Ireland is a better site for wind farms because of the available wind resources, sites along the eastern coastline such as Arklow were chosen for the first wind farms because of the shallower waters, which are 20& m (65.62& ft.) or less.

Adapted from the Wikipedia article Wind power in the Republic of Ireland, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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