How will our future energy demands be met?
Science Feature by Professor Glenn Patrick
IT was recently reported that Dorset Council had not ruled out wind farms along our coastline.
A previous proposal – the Navitus Bay project – for a wind farm of 194 turbines located on the bed of the English Channel, off the Dorset and Hampshire coast, was rejected by the government in 2015.
Of course, we already have a turbine generating green energy right here in Lyme Regis! This is the Town Mill hydro-electric system.
Whatever our views on the merits of large Dorset wind farms, it begs the question of how our future energy demands will be met in an era when we need to reduce the climate effects of fossil fuels?
In the northern hemisphere, new evidence of the effects of climate change appears on a regular basis with disappearing glaciers, new islands popping up from beneath diminished ice-caps and shrinking sea ice.
It is now widely understood that our climate problems have largely arisen from artificially adding greenhouse gases, such as carbon dioxide, to the atmosphere.
The largest share (50%) of this CO2 comes from electricity and heat production and it makes sense to make this a priority. This is set against the background of an increasing world population and the fact that fossil fuels are a finite resource which will eventually run out anyway, whatever we do about climate change.
The global temperature record shows that the average temperature has increased by 1 degree Celsius since the Industrial Revolution began.
In November, the upcoming COP26 conference will again look at how we limit future warming to stay within the 1.5 degrees Celsius agreed in Paris back in 2015.
So, the question is, how do we provide enough sustainable energy for everyone on the planet?
There are some parts of the world which can produce virtually 100 per cent of their electricity and heat needs from natural sources.
In Iceland, for example, hydro power generates 75% of its electricity, whereas geo-thermal sources provide 100 per cent of space and water heating as well as 25% of electricity.
The Orkney Islands were once dependent on fossil power stations delivering electricity by cable from the Scottish mainland, but these days 500 wind turbines and wave energy converters mean that enough power can be produced locally that some of it can even be exported.
These locations have obvious natural advantages, but what about the rest of us?
Wind farms have grown around the UK coast and play their part in renewable energy. However, there are still issues that have resurfaced in the Dorset debate.
The visual impact of large turbines is clearly not acceptable in certain locations. There is also the problem that the wind industry relies on rare-earth elements (such as neodymium) that must be mined to make the strong permanent magnets used inside the turbines.
Then, of course, the wind does not always blow, and the power supply is intermittent.
Similarly, solar farms can take up large amounts of farmland, the photovoltaic cells depend on rare metals (like gallium and indium) and the Sun does not always shine in the UK meaning another intermittent supply.
The intermittency of wind and solar power would be resolved if we could easily store energy, but there is no battery technology capable of storing Giga Watts of energy. This means there remains a need for a reliable baseload and backup capacity if we are to always keep the lights on.
The power demand in the UK is about 45 Giga Watts. With the existing 15 nuclear power stations approaching their later years and with 14 due to be closed by the end of 2030, this has meant proposing new nuclear stations.
About 50km to the north of Lyme Regis, lies Hinkley Point C in Somerset – the first of these stations to start construction.
Although nuclear energy is green in the sense that no carbon dioxide is produced, there are the obvious issues of nuclear waste, future nuclear fuels, and public perception.
In the media, nuclear waste often conjures up images of green, luminous liquid, but we are really talking about spent fuel rods. These largely (95%) resemble natural uranium as found in the Earth and this cannot really be regarded as ‘waste’ – as it is still a potential energy source.
Natural uranium consists of two isotopes – U238 (99.28%) and U235 (0.72%) – but it is only the U235 that can be used in thermal reactors. This means that the natural uranium is often enriched to boost the U235 content to 3-5% so that a chain reaction can be sustained.
It is this 5% which undergoes fission and although the fission fragments are radioactive, they have relatively short half-lives meaning that their radioactivity soon subsides.
It is the U238 which does not fission, but does capture neutrons to form the more troublesome transuranic – heavier than uranium – elements.
A good example is plutonium 239 which has a half-life of over 24,000 years! Only trace amounts of plutonium exist in nature, but like uranium it can undergo fission and can be used to fuel reactors.
Some countries reduce their waste problem by reprocessing the spent fuel to extract the uranium and plutonium to make new fuel. The remaining radioactive waste is then vitrified in a glassy state for long term storage.
About 90 miles across the English Channel from Lyme Regis lies the La Hague facility which has reprocessed enough fuel to power all of France’s reactors for 14 years.
The UK no longer reprocesses its fuel at Sellafield, so all the spent fuel is now regarded as waste. Nonetheless, the current inventory shows that the volume of high-level waste (HLW) – the highest radioactive category – would fit inside an Olympic size swimming pool.
We could also avoid using uranium completely by burning thorium instead. This has the advantage that it is three times more abundant than uranium (as abundant as lead) and inside a reactor can be converted to uranium 233.
Perhaps not surprisingly – with one of the world’s largest reserves – India is pursuing an ambitious programme based on thorium.
The only UK reactor – called Dragon – to include thorium as fuel was built in Dorset at the Winfrith Atomic Energy Establishment, but this reactor shut down in 1976.
Finally, we could ditch the conventional thermal reactor completely and build an accelerator driven sub-critical reactor (ADSR). In this device, the neutrons are provided by a high intensity particle accelerator which means that there is no chain reaction and if the accelerator is switched off, the reactor shuts down safely.
There is also the advantage that an ADSR can use thorium as fuel and produces a minimal amount of plutonium and other transuranic waste.
China has just built a prototype high intensity accelerator which has achieved its design goals with the view to building a full facility by the end of the decade.
Our future energy programme is of national strategic importance. Finding the right mix of technologies that delivers not only the required energy, but also limits CO2 emissions over the required timescales is a huge challenge.
We cannot afford to put all our eggs in one basket as there is no single, perfect technology.
Let us keep all our options open and include nuclear fission in the mix until our climate is under control or a ‘holy grail’ technology arrives like nuclear fusion.
Professor Glenn Patrick is a particle physicist and science communicator who explores the quantum world of sub-atomic particles (including at the Large Hadron Collider) and now lives in Lyme Regis.