How do we get to a Net-Zero Power Grid?
In Part 3 of our Series - Energy & Emissions - we look at how we could power an electrical grid that doesn't emit CO2. We give a brief introduction to the generating sources that could power this future net-zero grid, look at which of these sources makes sense for the UK, and show you where you can find more information on all of these topics
Disclaimer
In this blog we will discuss various technologies and industries, so it is worth stating that at COP26andBeyond we are technology neutral! While I have worked in both the nuclear industry and on Hydrogen Fuel Cells as a mechanical engineer, neither I nor COP26andBeyond have any specific backing or influence from a single industry.
A Net-Zero Power Grid
In our last blog in this Energy & Emissions series we looked at where our emissions come from and showed that roughly a third of the greenhouse gas emissions humans are pumping into the atmosphere come from the generation of electricity.
How we get our power, therefore, has a huge impact on how much GHGs we emit.
In our climate science series of blogs we have also talked about the urgent need to reach a point where we no longer emit CO2 and other GHGs into the atmosphere (known as Net-Zero).
To reach this point for the entire economy we will certainly have to reach it for the power grid, in fact decarbonising electricity generation is considered one of the “low hanging fruit” of decarbonisation, changing the electricity generating source from one that runs on fossil fuels to a low-carbon alternative can reduce emissions without the end user (us) seeing any difference. You can’t tell what type of power station generated the electricity when you turn on the light at home, and much of the progress countries such as the UK and US have made in reducing emissions already has come from a change in the sources of electricity.
Electricity is key to a Net-Zero future
When you have a power cut, as I have experienced three times here on the East Coast of the US in the last year alone, you begin to realise just how much of our lives rely on electricity.
Electricity is actually not a fuel, it is an “energy carrier”
This means it is a way of transferring energy from a source to an end use, and we have come up with plenty of uses for it. Electricity powers the appliances and lighting in our homes and places of work, it can cool and heat our homes, as well as power industrial processes and some forms of transportation. In most cases, electricity is generated at large power stations and distributed through transmission lines across countries, and occasionally even between continents via undersea cables.
Most Net-Zero scenarios and pathways rely on a large increase in the demand for electricity across the economy. This is because on of the more promising ways to reach Net-Zero would be to use electricity to run our cars and heat our homes, as well as all the uses we currently have for it, and then to produce that electricity from low carbon sources.
This would mean not only does our current electricity supply have to become fully low-carbon, but our generating capacity needs to grow in a big way. We will need a lot of low-carbon generated electricity to reach Net-Zero.
So, what should we do?
The easy answer is stop burning fossil fuels and start using renewable energy sources, but you won’t be surprised to hear it’s a little more complicated than that.
To start with, electrical grids are complex. Supply has to match demand very closely, or you get blackouts (or brownouts) so you have to carefully plan the mix of generating assets you have on your grid.
Also, the best solutions will vary country to country. Saudi Arabia has the potential to be a leader in solar energy with vast unpopulated deserts, Norway has enormous hydropower capabilities, and the UK has fantastic offshore wind and tidal resources. There is no one-size-fits-all solution.
Low-carbon vs Renewable
By definition, renewable energy sources are not depleted when they are used. This means wind, solar, tidal or hydropower can be defined as renewable sources of electricity.
Low-Carbon technologies are those that don’t emit CO2 and other GHGs, for instance Nuclear and natural gas plants with carbon capture technology. While they don’t contribute to climate change at the point of generation they do use up natural resources faster than they can be replenished, such as uranium or methane.
There are a number of ways you can power a grid using low-carbon generating technologies, but what are these technologies?
Here we give brief introductions to the main ways we can produce low-carbon electricity, future blogs will focus on these sources one by one to provide more depth and technical understanding of their benefits and drawbacks.
Solar Power
Solar power plants harness the energy of the sun, either through the use of photovoltaic cells (PV) or through concentrating the energy using lenses and mirrors to generate steam and turn turbines.
PV cells can be arranged in panels either in large solar farms or distributed in smaller arrays on houses and businesses to produce electricity when the sun shines.
In the UK they are mainly used to boost energy supply in the summer during midday peaks of demand, as shown by the grid data for the UK on the 22nd August (taken from Gridwatch):
Solar energy is also one of the cheapest forms of generating electricity, with its price reducing rapidly in the last few years and is the fastest-growing form of energy source.
Wind power
Wind turbines are structures that comprise of a tower, blades (almost always 3 of them), and a turbine housed within a case called a nacelle. They can be placed onshore or at sea (offshore wind) and their size and power are increasing each year, to the point where the latest offshore turbines are almost as large as the Eiffel tower with blades as long as a football pitch.
The cost of energy produced by wind turbines has also reduced in recent years and offshore wind is rapidly becoming the backbone of renewable generation in the UK. Onshore wind remains a key source of renewable generation but runs into more local planning disputes and has received less backing in recent years from the UK government.
One of the most promising future developments is floating wind, where the turbines do not have solid foundations in the sea bed but are tethered to the ocean floor, allowing them to be placed further offshore where the wind is stronger and more reliable.
Hydropower
A huge amount of energy can be stored in bodies of water. If you dam a river and hold that water back from flowing downhill, you can harness gravity to power turbines when you release it, which can produce large quantities of electricity.
You can also pump water uphill when electricity is plentiful, and allow it flow back down through turbines when it is scarce, in a form of energy storge known as pumped hydro. The UK, Dinorwig Power Station, known as Electric Mountain, is an example of a huge pumped hydropower station.
Hydropower is one of the biggest sources of low carbon power for some countries such as Norway and Brazil, however it takes a lot of investment to build the civil engineering structures required to hold back significant amounts of water, and it alters the natural environment, flooding some areas and withholding water from others.
Geothermal Energy
Geothermal energy plants take advantage of the heat produced in the Earth’s core to heat steam and turn a turbine.
While there are a number of different technologies the basic principle of a geothermal power plant is that water is piped from under the ground and the heat of the water is turned to kinetic energy via a turbine, which then turns a generator producing electricity.
Geothermal plant in Iceland. Courtesy of Unsplash
Some countries such as Iceland and New Zealand (predominately those near tectonic plates) have a strong potential for geothermal power due to the heat being close to the surface, reducing the cost of the power plants.
Nuclear Fission
Nuclear power is one of the few technologies that is both low-carbon and provides large scale baseload power. Essentially, a nuclear plant is designed to harness the energy given off when an atom splits (called fission), use that energy to heat steam which can then be run through a turbine, which turns a generator to produce electricity,
Hinkley Point
In the UK, our fleet of Nuclear plants is ageing, with Hinkley Point C in Somerset the only new plant under construction. There are some technological challenges with launching a big increase in nuclear capacity, such as long-term solutions for nuclear waste, but the most pressing impediment is the large cost of capital compared to new renewables. To overcome this issue the UK Government is considering alternative financing options for future nuclear projects, and new technologies such as Small Modular Reactors are being proposed. In order to reach Net Zero key decisions will have to be made about the role of nuclear in the energy mix.
Perceptions of nuclear power are complicated and controversial, but often misjudged. For instance, only 26% of 18-24 year olds in the UK know that Nuclear is Low Carbon. Read our interview with Henry Preston to hear how the industry aims to work on its perception by the public.
Tidal Power
A fairly nascent industry compared to other renewable forms of generation, various technologies have been developed that harness the power of the tides to generation electricity.
A Tidal Lagoon project was proposed in Wales that would block off a large lagoon using a sea wall, and run that sea water through turbines as the tide went in and out. The project was scrapped by the UK government in 2018 due to concerns around it’s cost, and will not go ahead, leaving tidal developers to forge ahead with smaller “Tidal Stream” technologies such as the Orbital Marines turbine shown above which stays stationary in the water and lets the flow of the tides turn underwater turbines to generate electricity.
No single technology has emerged as a clear “winner” in this area but there are some promising developments. One of the great advantages of tidal power would be the predictability and consistency of the tides, meaning supply could be planned to match demand as predicting the tides is a well honed science compared to predicting the wind.
Fossil Fuels using Carbon Capture & Storage
Carbon Capture and Storage (CCS) has long been touted as the silver bullet to producing low carbon power. The idea is that you could run a coal or natural gas plant as normal, but capture the CO2 emissions before they reach the atmosphere and pipe them deep underground, perhaps in empty oil and gas fields, where they can’t contribute to the greenhouse effect. The UK government launched a £1Bn competition to develop CCS in 2007 but after numerous delays cancelled the scheme in 2015, essentially ending development and investment in the technology.
The road blocks have really been financial so far, there are technologies that would work, they just cost money, and adding energy intensive processes reduced the efficiency of your power plant. However, some forms of CCS currently being researched would actually produce extra power which is potentially very promising as it would provide an economic incentive to capture carbon. If not, there will have to be some form of government incentive to push energy companies to start to use the technology at scale. It is still seen as crucial to reaching Net Zero, with one report by Atkins predicting 100 CCS plants will be required by 2050 if Net Zero is to be reached. Since there are currently no power plants with CCS attached, a lot of work is required to re-start development of the technology.
Great, we have all the technologies, why can’t we just use them to make a Zero Carbon grid?
The UK’s Committee on Climate Change wrote a report in 2019 “Net Zero – The UK’s contribution to stopping global warming” in which they set out what a Net-Zero future could look like. This showed it is physically possible for us to have a Net-Zero economy, but it is not a plan on how to get there.
The energy section of the report suggests we may have to see a doubling of electricity demand, a quadrupling of current renewable generating capacity complimented by “firm” low carbon sources such as nuclear and Gas with CCS, as well as potential role for Hydrogen to help the hardest to decarbonise sectors (the Hydrogen economy will be the subject of a future blog).
This future is technically feasible, but getting there will be difficult and the CCC themselves have said the gap between what are doing and what we need to do is actually widening.
A report by engineering consulting firm Atkins suggested that “From now to 2050 we must replace or repower almost all our current generating capacity and build almost twice as much again to meet the anticipated increased demand.” A herculean task, and this is supposed to be the “low hanging fruit” of decarbonising the whole economy!
So, while it is widely accepted that all the technologies we need to reach a net-zero grid are already developed, they are not built to scale yet. In the UK we will almost certainly need even more offshore wind farms, greater grid balancing capabilities, new nuclear plants to replace the retiring older ones, and CCS added to gas plants. All of this takes investment and time, which we are rapidly running out of.
Also, running a grid on 100% renewables isn’t as easy as it sounds. You may have read headlines like “UK runs on renewables for record number of days” and think “well why can’t we just do that all the time”. But there are a few problems, firstly, the UK is not particularly sunny, so for us solar power provides a good top up to our grid in the middle of summer days, but is not much good in winter, or at night.
Wind is more reliable in the UK, particularly offshore, but even then there are sometimes days with little of no wind, meaning an alternative form of generation is required. So we need some form of “firm” or baseload power. This is power that can be reliably provided every day in a predictable pattern, whatever the weather.
Most of the baseload power in the UK used to be from coal, but this has been replaced by natural gas, leading to a big drop in emissions from electricity generation, which is undoubtedly a good thing. The tricky bit, however, is weaning ourselves off gas, and managing to replace that missing generation with enough baseload sources to complement an expansion of renewables.
Is the grid ready for the future?
Well, thankfully it is not just us at COP26andBeyond who have been thinking about this. The challenges we have laid out in this blog have been extensively discussed and analysed by engineers and policy makers.
One of the key upgrades to our grid will be the addition of better forms of energy storage. With more renewables providing power at times that don’t exactly coincide with when we need the power, that electricity will have to be stored somehow. And how best to store electricity is one of the key technical challenges yet to be solved by engineers.
As Wind Energy pioneer Dr Andrew Garrad said in an Energy For the Energy Transition event we hosted in March 2021:
“I think the big challenge is integration and use, generation we have almost cracked, (wind energy) will go on getting cheaper and there may be technological developments (but with) integration and particularly storage, we have only started to scratch the surface of storage… It has been the holy grail for a long time and there is now real progress but there is still a huge range of different technologies, from hot rocks to chemicals to pressing air to flywheels to pumping water up a hill, so that is where I am expecting to see major changes together with integration.”
The solution likely depends on how long you need to store the power, if its is a matter of seconds, it looks like large banks of batteries could be the answer. Minutes? Pumped Hydro. Days, weeks, months? Perhaps converting water into hydrogen, compressing it, then releasing it through a fuel cell to produce energy will be the solution. We will explore these technologies in greater detail in future blogs.
With a huge increase in renewable generation, firm power from nuclear and CCS, increased grid integration and new energy storage technologies the UK could have a Net-Zero power grid by 2050. But time is running out to put everything in place to make that happen, and its not just the UK that needs a Net-Zero grid, the rest of the world needs to replace fossil fuels with renewables and low-carbon sources of energy. There are technical challenges, but the main obstacles are still political, which shows just how important the decisions made at COP26 will be to our collective future.
Where can you find out more about the power grid and electricity sources?
The fuel mix of the UK grid can be tracked in real time at https://www.gridwatch.templar.co.uk/
John Armstrong - https://www.amazon.com/Future-Energy-transition-technology-sustainability-ebook/dp/B08W29N1G3
CCC – https://www.theccc.org.uk/publication/net-zero-the-uks-contribution-to-stopping-global-warming/
IEA Net Zero Report - https://www.iea.org/reports/net-zero-by-2050
Atkins Net Zero Report - https://www.snclavalin.com/~/media/Files/S/SNC-Lavalin/download-centre/en/report/engineering-net-zero-summary-report.pdf
Energy Institute - https://knowledge.energyinst.org/