This week saw the opening of a massive energy project centred on Shetland. A consortium led by the French energy company Total has invested £3.5bn in extracting gas from deep undersea over 100 km west of the islands, receiving it onshore at a new complex adjacent to the existing Sullom Voe oil terminal, and then feeding it into the UK mainland gas grid. According to the report “the Shetland Gas Plant is said by its operator Total to be capable of supplying energy to two million homes” (Total turns on gas from west of Shetland Laggan and Tormore fields).
By coincidence, an article last week reported that Hornsea takes the world lead in offshore wind. Hornsea is a project which has two things in common with the Shetland gas terminal: it is offshore (120 kilometres off Yorkshire) and big (with a peak capacity of 1.2 gigawatts, nearly twice the size as the London Array, currently the world’s largest such installation). The big difference, though, is that gas supplies are guaranteed, barring a system failure, while the output of any wind farm varies uncontrollably.
The ‘peak capacity’ quoted for Hornsea would give a theoretical energy output of nearly 10.5 terrawatt-hours. If we take 80% as the actual capacity factor, comparable to an efficient conventional station, this would generate sufficient electricity to power about half a million homes (using the 2011 ONS figure of 16 MWh for total annual household consumption of energy as electricity and gas), if it was available on demand. But in reality, the capacity factor would be half that, so the figure for homes supplied would come down to 250,000.
For more background information, it’s interesting to look at the London Array, as the Engineer journal did in 2013 (Your questions answered: the London Array). This wind farm occupies 100 square kilometres in the Thames estuary. The current 630MW peak output arrangement was intended to be added to in a second phase, but this has now been dropped because of concerns about the impact on overwintering Red Throated Divers.
In response to a question about expected output, the engineering team answered “We expect a load factor of c.40%, giving output of c.2,200,000MWh – enough to meet the electricity needs of around 500,000 households.” On that basis, we can expect the claim for the planned Hornsea project to be for a million homes to be supplied with electricity. However, if we take overall household energy consumption, the output of this giant wind farm will supply only a quarter of that number over a year.
The important point is that this quarter of a million is simply the expected output of the wind array divided by the average household energy consumption. It should not be confused with a real figure; it is by no means a guarantee that this number of houses could be supplied with energy at any one time.
To continue the comparison, Hornsea is said to cover an area more than five times the size of Hull, which would make it at least 350 km2. The developers will not reveal the cost, but the London Array cost £1.9bn, so let’s assume around £4bn. The Shetland gas terminal, on the other hand, is reported to be part of an overall £3.5bn investment by Total and its partners and the biggest construction project in the UK since the London Olympics. However, it has a footprint of only about half a square kilometre (this and other facts from Building the Shetland Gas Planton the Petrofac website).
Gas will, of course, be sold at market prices, although in practice often on long-term contract. Some will go directly to homes and commercial premises for heating, and some to power stations, which will provide electricity also at market prices. On the other hand, we read that World’s biggest offshore wind farm to add £4.2 billion to energy bills. Under a contract agreed in 2014 with Ed Davey, Energy Secretary in the then coalition government, electricity from Hornsea will cost £140/MWh – four times the current market price – for a guaranteed 15 year period. It is estimated that this will cost domestic and commercial consumers £4.2bn in total, or an average of £280 million each year.
The National Audit Office was critical of the deal, and with good cause. In 2015, a competition for available subsidies for existing wind farms resulted in prices as low as £115/MWh being agreed. By way of comparison, the troubled HInkley C nuclear project would attract a price of £92.50/MWh, which has been widely condemned as being unnecessarily expensive. Against the price for offshore wind, it begins to look like a real bargain.
So, what we have in the case of Laggan/Tormore and Hornsea can be summed up as follows. One is a plant with capital costs of £3.5bn, which should not increase energy bills (and may help to keep them down) and will not cost taxpayers anything over its lifetime, capable of supplying the entire energy needs of two million homes reliably (that’s 8% of national energy demand).
The other has much the same capital costs and will add an estimated £4.2bn to energy costs over 15 years (and more if it lasts longer). On a straight comparative basis, it is theoretically capable of supplying the energy needs of a quarter of a million houses, or about 1% of total UK energy use. Not factored into this are the additional costs of accommodating the fluctuating output into the grid and the need to have conventional backup to maintain a stable supply.
The simple question to ask is why a government would support a project with at best one-eighth of the output of Laggan/Tormore and costing the country at least twice as much over its (almost certainly shorter) lifetime? The answer would of course be to meet emissions reduction targets. But there is a much more reliable way of doing that, which is to build nuclear stations.
The fact that we are still so far from doing this is down to problems with finance and lengthy design approval as well as the arbitrary inclusion of targets for renewable energy to emissions reduction goals. To have a secure, affordable, low carbon energy system, we need more nuclear and gas use rather than more massive wind farms. Unfortunately, in the case of offshore wind, it seems to be a question of out of sight, out of mind, at least until the bills start ratcheting up.