Thrashing out the sums — land use for different energy forms
Written by David Watson
September 13, 2019
Solar and wind energy have enjoyed a meteoric rise in popularity in recent years. The upfront price tag for these intermittent sources of energy continues to fall. However, it’s worth looking beyond those capital costs at the wider impact of these technologies. One such impact is on land use.
In my country, the UK, land is at a premium. We’re over 60 million people in a small space, and it’s difficult to build pretty much anything without rubbing up against existing requirements for housing, industry, transport and, though often overlooked, wildlife.
I recently wrote an articleon the wildlife inhabiting the nature reserves alongside Sizewell B and other nuclear plants in the UK and beyond. Amazingly, I found out that not only are there nature reserves adjacent to nuclear plants, but they often contain endangered species. For example, there are thought to be only 160 breeding bittern males in the UK, 9 of which live in the marshes directly alongside Sizewell.
I thought I would work out whether we could replace the nuclear plant with onshore wind or solar whilst keeping the precious wetland habitats intact. The answer was an emphatic “no”.
Replacing Sizewell B with solar would require completely draining the RSPB wetland reserves alongside the nuclear plant. More than that, it would require covering every single field between Ipswich and Lowestoft with panels, an area which otherwise is agriculturally very productive. If we wanted to avoid cutting down the forests and evicting those living within the shaded area, this would mean using an even larger amount of land.
Wind turbines would require an even greater area. Unlike solar panels which cover vast surface areas, wind turbines have to be spread out, which leaves space for some wildlife below. However, the marshes alongside Sizewell B — of world importance to bird and ampihibian life — would have to be drained for the turbines to be installed, and any trees that happened to be in the way would require felling. Once running, the turbine blades would be hazardous to the vast flocks of birds, as well as rare species of bats, that use the marshes and lakes in this area.
How did I come up with the numbers?
Sizewell B’s nameplate capacity is 1198 MWe. Its capacity factor (how much of the year it was running at full power) was 83.9% for 2017. I measured the site on Google Earth and it came out as 0.2 sq km in size. The capacity factor for onshore wind in 2017 according to UK government figures was 28%. This means we would need to install 3590 MW of wind capacity to achieve the same energy ouput over a year as Sizewell B. Assuming 2W/m2 of land for onshore wind this would require 1794 sq km of land to be covered by wind turbines. Feel free to add a factor of two if you think 2W/m2 can be improved on — either way the amount of land required is huge.
A similar approach was used for solar: 10.7% capacity factor, 10% efficient panels, 100W/m2 solar energy. This gives 940 sq km of solar panels. If we use more expensive 20% efficiency panels, we can half that to the still massive 470 sq km.
Neither of these calculations accounts for the intermittency of wind and solar, which to match Sizewell B’s low carbon emissions would require balancing out using enormous and currently unavailable battery storage. Today such wind and solar farms are backed up by methane gas plants, which effectively increase their lifecycle emissions.
If we did want to use wind turbines then offshore might be a better bet where they would occupy a slightly smaller area than if onshore (due to a 5–10% higher capacity factor). The impact on the seascape is likely to be much smaller than the onshore wind impacts on the landscape, although there is still the ever-present risk to birdlife posed by turbine blades.
This land use issue partly explains why the UK government is a huge supporter of offshore wind but no longer subsidises onshore wind or solar.
