Engineering challenges of the UK energy review

3 May 2002

Recent editions of NEI have focused on the implications of the UK energy review for nuclear power. Here, energy consultant Ian Arbon outlines the difficulties in achieving the targets recommended for the review's big winner - renewables.

The long-awaited Policy Innovation Unit (PIU) UK energy review (ER) has little new to say on the subject of renewables and energy from waste (EfW). The proposal to see 20% of power generation from renewables by 2020 is to be welcomed but of little value without serious commitment from government. The potential of EfW is disparaged and there is no methodology of dealing with the growing problem of landfill. Power transmission difficulties are mentioned, but few solutions are offered and embedded power generation systems are largely ignored. All things considered, as far as renewables and EfW are concerned, the ER is a poor effort that gives few pointers as to what the future holds for these technologies.

An ambitious target

The ER gives little encouragement to newer renewable energy technologies. The emphasis is on the four well-known fields of onshore wind, offshore wind, solar photovoltaic, and biomass & energy crops. There is some hope held out for power generation from waves and marine currents, but not in the shorter term.

So what does this contribution from renewables and waste mean for UK power generation? The Figure on the next page, taken from the ER, shows the Department of Trade & Industry's (DTI's) view of the scenario to 2020 and shows coal and nuclear in steady decline, with renewables not increasing between 2010 and 2020, and natural gas making up the difference. Remarkably, it still shows renewables providing 10% of power generation between 2010 and 2020, rather than rising to 20% by 2020 as proposed by the ER.

Estimating how much power can be generated from renewables in the UK gives the following figures. The current demand of 400TWh/year gives an installed capacity of roughly 50GWe. According to the government's 1997 target of 10% from renewables by 2010 this would require some 5GWe of installed renewable capacity. The PIU's revised 2002 target of 20% by 2020 increases this to 10GWe.

So how is the 2010 UK target of 10% from renewables and EfW made up? The ER does not define this but estimates made from 1998 DTI figures show onshore and offshore wind at 2000MWe, biomass and energy crops contributing 500MWe, landfill gas and EfW with 1500MWe and hydroelectric with 1000MWe.

Similarly, estimates for the 2010-2020 target of an additional 10% give offshore and onshore wind at 1000MWe each, biomass and energy crops at 1000MWe, EfW also at 1000MWe and other renewables with a further 1000MWe.

The estimated contribution to the 10% target of various renewables and EfW would suggest that, during 2002, the UK should already be achieving 5%, whereas the reality is just 3%. It is also worth noting that it has taken the last ten years to increase the percentage generated from renewables and waste from 2% to 3%.

Major obstacles

The ER identifies three main obstacles to more renewable energy:

• The New Electricity Trading Arrangements (NETA) penalise intermittent and unpredictable sources of power generation, which most renewables are.

• The inadequacy of the current transmission systems, built to connect huge fossil-fuel power stations to major users.

• The lack of planning consent, par-ticularly for biomass and wind installations.

However, beyond the blindingly obvious "something must be done" the authors of the ER have little to say on how these serious obstacles to progress can be overcome.

The ER does say, though, that "the main technical consideration is the feasible rate of deployment. In order to get more than 20% of electricity from renewables by 2020, build rates for the leading options would need to be at levels never before seen in the UK. Onshore and offshore wind would need to be installed at a rate of between 1-2GWe per year in the period 2010-2020" and also, it should be noted, between 2002 and 2010 given the 10% target already outlined.

"This would be a challenge" the ER notes by way of understatement, "but 1.5GWe and 1.6GWe of onshore wind was built in Germany in 1999 and 2000 respectively, and a further 1.2GWe was installed in the first eight months of this year [2001]. Build rates of 1GW per year were also seen in Spain in 2000, and 600MWe in Denmark in the same year." However, these impressive figures are in fact nameplate ratings not the actual amount of electricity generated - they have to be de-rated by a factor of 3 or 4. So, let's do the sums:

Given the targets, it would be safe to assume 200MWe of new actual power contribution from wind is required each year for the next 18 years through to 2020. Assuming an average turbine nameplate rating of 1.5MWe then a continuous rating is likely to be around 400kWe, or 27%, depending on where the turbine is located. To achieve the annual target of 200MWe, then 500 such turbines have to be installed each year. This equates to the installation of 1.35 turbines every day of the year, or 2 each and every working day!

To illustrate the point further: 500 wind turbines per year would probably be at around 100 different locations, each of which would require planning consent. It is estimated that 95% of all wind farm planning applications are refused, at least first time. This means that to achieve 100 successful installations, 2000 full-blown planning applications would have to be made each year. Unfortunately, UK industry has no experience whatsoever in building turbines of this size and the ER has much more to say about statistics than about practicalities and appears to have been written by civil servants rather than by engineers. It encourages the deployment of existing renewable technologies in the short-term and the development of new technologies for the longer-term but has little to say about how this would actually benefit the beleagured UK manufacturing sector.

The ER makes several references to the need to upgrade transmission lines and goes on to say: "There is also a potential need for upgrading of electricity transmission from Scotland if marine and wind resources from the far north and west are to be exploited. The DTI's recent proposal to examine the feasibility of an offshore cable along the west coast is an important first step." But there is no obvious reference to embedded or distributed generation schemes that would mitigate that need.

Funding and the future

The ER makes no recommendation to change the current system whereby government funding is more readily made available for inventions and innovations than for the application of existing technologies in novel and innovative ways. Examining the future for potential sources of renewable energy reveals some significant opportunities.

Solar energy

Active solar thermal relies on the heat of the sun for space heating of buildings, usually by hot water. This has limited use in the UK. Passive solar thermal is more related to building design, which must capture the heat of the sun. There is certainly scope for more of this in the UK.

Photovoltaic systems rely on the light, rather than the heat, of the sun and should have excellent application in many UK installations, once production volumes have lowered unit costs.

Water power

Large scale hydro is the largest source of renewable energy in the UK and is well proven. Small scale hydro has limited application in the UK to date - yet most of the growth will be in this field.

Tidal barrage technology is also well proven, for example in France. The main site for the UK is the Severn estuary, which could provide around 6% of the UK's power requirements. Environmental consequences are quite high, however, and it is unlikely to be built.

Wave energy is good at capturing the public's attention but not much else. Tidal stream turbines show considerable promise, with two competing British technologies. However, the technology is in its infancy.

Wind power

Onshore wind technology is now well-proven and cost competitive. The ER relies very heavily on the implementation of this and major problems to be overcome are that the best wind regimes are very remote from point of use and visual impact is a concern to some. Nominal size is 1MWe to 1.5MWe, expected to rise to 2.5MWe.

Offshore wind is regarded as the answer by all British NIMBYs ("not in my back yard") because it puts the problem out of sight. However, there are major obstacles to be overcome, particularly in the lack of deep-water experience and how to transmit power back to shore. Nominal size for offshore wind turbines is 2MWe, expected to rise to 5MWe.


Virtually any type of purpose-grown energy crop or agricultural residue can be used to produce renewable energy. The main benefit of power from biomass is that it avoids the intermittent and remote problems of other renewable energy systems.

Energy from waste

Most municipal solid waste (MSW) is currently landfilled because of the public dislike of "incinerators". Modern combustion systems have been developed which could overcome all such objections and can deal with all solid and liquid wastes, not just MSW.

Regarding gaseous wastes, the ER considers coal seam methane but no other gaseous wastes. There are well-proven and cost competitive methods already existing in the UK which can produce a sizeable amount of electricity from industrial waste streams.

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