Can wind turbines meet our energy needs?

Published on Thursday, 16 September 2010 09:24

	By Robin Whitlock Follow @RobinWhitlock66

I wrote in my previous piece, concerned with solar power, that Vaclav Smil, the Manitoba University professor of engineering and writer, is generally sceptical of the ability of renewable technology to replace fossil fuels by themselves. What seems to be true for solar power is also true for other forms of renewable energy and Smil is similarly pessimistic with regard to wind power. In the windiest parts of the USA the power density obtainable by wind turbines is around 400 W/m², Expressed as electricity generated per m² it is a miniscule amount, largely due to the spacing required between each turbine in order to reduce wake interference.

Smil states that a wind farm comprising large 3 MW Vestas turbines with a rotor diameter of 112m and spacing of six diameters apart will have a peak power density of 6.6 W/m², which would realistically translate as an average of 2.2 W/m². Smil goes on to look at other sites such as the London Array in the outer Thames estuary, Altamont in California and Puget Sound Energy's 'Wild Horse' wind farm and concludes that the power densities obtainable from wind will not be higher than 2 W/m².[1]

David Mackay points out in his book that the amount of area available in the UK for shallow offshore wind would be restricted by the requirements of shipping.[2] He also states that offshore wind is difficult because of the corrosive effects of seawater. He cites the example of the Danish wind farm at Horns Reef, which had to be dismantled because all the 80 wind turbines had to be dismantled and repaired after 18 months exposure to sea air.

He speculates that the Kentish flats turbines may be having similar problems with their gearboxes. Even so, assuming a power density of 2.6 W/m², which Mackay calculates at the beginning of his chapter, on offshore wind, a power delivery of 16 kWh/d per person would require some 44,000 3 MW turbines equal to 15 turbines per km of coastline assuming an area of 13,000 km². That's two-thirds the size of Wales.

David Mackay

With regard to deep offshore wind, Mackay argues that an area 30 per cent larger than Wales would be required. Much of this would be further than 50 km from the shore and would deliver 32 kWh/d per person. All this ignores the problems caused by wind intermittency, it also ignores the resources required to build the infrastructure.

Mackay calculates that in order to generate 48 kWh per day per person from offshore wind 60 million tons of concrete and steel would be required, which is one ton per person. Mackay compares the effort required with the building of the Liberty ships by the US during the Second World War, some 2751 of which were built between 1940 and 1945, and this is just in relation to offshore wind, never mind all the other forms of renewable power. As I read this, I can't help thinking of the Friends of the Earth campaigner at the Bristol Festival of Nature some months back who told me that we should effectively be on a 'war footing' by now.

In comparing renewable technologies with current fossil-fuel sources of electricity generation, Smil concludes that replacing fossil fuels will certainly not be easy. My reading of MacKay's book leads me to believe that he thinks the same. Smil believes that a society that chooses to rely totally on renewables would have to concentrate flows of energy from solar, wind and biomass in order to bridge the energy gaps. This would require an increase in fixed-use renewable energy developments and would deny the land used to any other form of use, save perhaps crops or grazing beneath the wind-turbines.

There would also have to be an extensive network of roads for maintenance purposes and buffer zones devoid of any permanent human habitation. More land would have to be secured for transmission rights-of-way in order to secure the transmission of generated power to other areas. As a consequence Smil concludes that the land involved would have to be ten to a thousand times greater than that currently used by today’s fossil-fuel industries.[3]

George Monbiot in his book Heat:How Can We Stop The Planet Burning is more optimistic. Smil makes one glaring omission in his articles, he doesn't look at offshore wind, but Monbiot revels in the potential rewards that offshore wind has to offer.[4]

Monbiot’s optimism is reflected in a study by Cristina Archer and Mark Jacobson of Stanford University in the USA. Archer and Jacobson found that the total amount of global wind power that is available from locations with mean annual wind speeds of greater than 6.9 metres per second (m/s) at altitudes of 80 m is 72 terrawatts which equates to 54,000 Mtoe. They conclude even if 20 per cent of this power could be captured, this would be enough to meet global energy demands for all purposes and could also meet the world's electricity needs seven times over.[5]

Vaclav Smil

Somewhat confused, I decided to email Professor Smil and find out what he had to say in response. In his reply Smil sounded somewhat, and in my opinion, justifiably, annoyed. "Monbiot should educate himself about the costs, capacities and problems with HVDC cables before he writes anything about them" he says before going on to criticize the media attention Monbiot regularly receives.

"Why do the media people keep citing sensationalizing writers like him rather than engineers who actually build that stuff and understand its true potential and limitations?" I believe this to be a very valid point. Yet Smil goes further, he dismisses the idea of a Saharan energy source and the idea of obtaining sufficient power from global wind resources, "There are no Saharan megasolar parks" he says "and will be none for decades to come, energy transitions move slowly. Archer and Jacobson is just a theoretical maximum account, not an assessment of engineering capacities."[6]

It would be foolish to merely rely on a limited number of sources regarding this issue, so I presented the subject on the discussion pages of several relevant groups on the networking site Linked In to find out what other experts in the field had to say on this question.

Richard Crenko, a consultant at Cleantech Commercialisation in Berne, Switzerland, stated that he did not quite understand Smil's fixation with power density. "Virtually no one else in the business of future energy pathways gives this parameter anywhere near this kind of importance,” he says before claiming that Smil's data on PV efficiencies is at least five years out of date.

"In the lab concentrator cells have exceeded 40 per cent (not 30) and greenfield PV powerplants are well above 15 per cent (not 10) with monocrystalline silicon".[7] Smil however, unsurprisingly, sharply rejects this criticism. "Power density is a fundamental measure of the dynamics of all systems, from microbial mats to galaxies" he says, "I am not referring to theoretical laboratory performance (irrelevant for the real world) but to actual performance of Spanish and German solar plants, the reality as is".[8]

Another voice on the same LinkedIn discussion site pointed me in the direction of the recently released Zero-Carbon Britain report.[9] This report favours a paper by Jacobson and Delucchi (2009) which, given Smil's view of Archer and Jacobson's assessment of global wind power mentioned above, is hardly encouraging. Jacobson has also been widely criticised elsewhere, to which, apparently, Jacobson has consistently failed to respond.[10] The bulk of the chapter on renewables advocates a mix of renewable technologies excluding nuclear. This may indeed be possible in the long term but it will require time in order for the necessary infrastructure to be constructed and because energy transitions move slowly. The key issue at stake here is that we may not have the time to make the transition without experiencing gaps in supply.

This is the key point made in a new book by Derek Birkett entitled When Will The Lights Go Out due to be published shortly. Birkett is a former Grid Control Engineer with over 20 years experience. His message was recently carried by The Daily Express and he essentially warns that Britain could face blackouts in the near future because of over reliance on renewables. "We need a mix of sources and this takes time," Birkett says. "Renewables have the problem of being intermittent, particularly wind, and we need more back-up capacity. By having all our sources in one basket we are risking disruption".[11]

 

Professor Smil's new book Energy Myths and Realities makes for highly interesting reading. In the book he swiftly demolishes the idea that understanding these quite fundamental issues is an easy task to achieve. "Suddenly, everybody seemed to become an energy expert" he writes in relation to the situation following the oil crisis of 1973-4, "eager to profer solutions. In reality, however, only a relatively small group of people understood energy affairs well enough to recognize how much was unknown about the structure and dynamics of complex energy systems, and how perilous it was to prescribe any lasting course of action."[12]

I have long felt that we are now paying the price for a wasted opportunity, coupled with the short-term greed of politicians and energy executives alike. When I was a somewhat younger environmental activist in Yeovil during the early 1990's, virtually everyone I talked to at the time, outside of my circle of environmentalist friends, including members of my own family dismissed my concern about climate change as delusion and paranoia.

 

The reason for this has now become clear, huge oil corporations with vested interests in maintaining the status quo lobbied intensively against measures to counter the risk of climate change and any consideration of reducing demand on fossil fuels. The result was that throughout the 1990s, most of the population throughout the western world dismissed climate change totally. It is surely scandalous that we as a society wasted ten years during which we should have been urgently weaning ourselves off a total reliance on oil.

Smil too condemns years of lost opportunities to increase efficiency and reduce wastefulness. "Unfortunately, some sensible policies aimed at reducing wasteful energy use were completely (and indefensibly) abandoned at this time" he writes, before going on to describe a whole range of efficiency measures that existed but yet were not developed until the price of oil began to rise again in the early years of the new millennium.[13]

Smil does not accept the concerns of those worried about energy depletion or 'peak oil', mostly because of existing reserves of other hydrocarbons besides oil such as non-conventional oil and natural gas. This is where we disagree, but in all other points relating to renewables and the way that they have been presented as a panacea for our energy problems I have to accept his logical and presented arguments. The blunt truth of the matter is that total reliance on renewables will not save us.

So what is the answer? Some say that we need to abandon fossil fuels entirely in order to achieve a sustainable society, but it seems clear that renewables will not support us if we choose that option. As Dr Lewis Perelman, a consultant in the areas of sustainability and homeland security, comments on LinkedIn "I would advise caution about what you wish for. There was in the past a human society based entirely on 'green' energy. Historians call it the Dark Ages."

That might seem a bit over dramatic to some but Dr Perelman goes on to explain that "the loss of fossil fuel power will impose social impacts that many today would find unattractive."[14] The Zero-Carbon Britain report appears to recommend a 'power-down' stage during which we first concentrate on increasing efficiency while simultaneously restricting consumption and reducing emissions.

This appears to be a form of 'managed collapse' supported by existing fossil fuel resources. If Smil is right, there would be no real reason to fear an energy peak during this process because of the availability of natural gas and unconventional oil. This scenario may therefore be possible providing there is enough political will and given the support of the general public. The idea would then be to 'power-up' using a renewables package, which hopefully would have increased in efficiency. In other words this appears to recommend creating the time necessary for a transition to a fully renewable future.

Another option would be to create a strong nuclear-power programme with an increase in the number of nuclear power stations, and the replacement or refurbishment of those already in situ, in order to reduce reliance on fossil fuels as soon as possible and in support of the creation of a wide-ranging renewables programme. It's this option that seems to be favoured by the current governments in both the UK and the US.

However, both Smil and Mackay basically state that renewables are currently as efficient as they are ever going to get and therefore any increased reliance on them is probably unlikely. Given the threat from climate change, if not also energy depletion depending on whether you believe there is an energy depletion problem, it is therefore more realistic to finally put to bed the idea that we can continue to follow the current model of economic growth with ever increasing levels of consumption with all that that entails. The idea instead would be to build a new society where growth is based not only on gross national product but also on aspects that have so far been ignored, such as a healthy and clean planet, a fair and equitable global society and satisfaction with what we already have (or less) rather than what else we can acquire and achieve.

Whatever you believe to be the most plausible solution, it is becoming increasingly clear from the rate of climate change alone and the threat that entails for our whole society and the planet that whatever we decide to do we need to make the decision sooner rather than later.