Renewables, Energy Flexibility and Energy Storage
… … … 12 minute read … … …
This is blog number one in what I plan to be a series of blogs about decarbonising the energy sector. I will be talking about up-and-coming technologies and innovations which are helping, or will help, in this revolutionary transition. In my last blog (blog zero), I introduced myself, my interest and why decarbonising the energy sector is of absolute paramount importance in tackling climate change. I want to now talk about, in a bit more detail, how we can transition from a fossil fuel dominated energy mix to a low-carbon and eventually a zero-carbon energy mix. It is important to understand and acknowledge that this is a transition, we can’t simply substitute renewables for fossil fuels straight away. To appreciate this, it is necessary to understand a bit about how the National Grid works. Once this is understood, it becomes clear what needs to change and how new and exciting innovations will help this transformation.
Throughout this blog I will be primarily using the example of the UK energy mix but the technologies and core concepts are largely universal.
Okay so, the National Grid of Great Britain, how does it work? A fundamental concept, which perhaps sounds ridiculously obvious, is that when you turn something on and use electricity, energy needs to be generated somewhere else to create this electricity. But the sensitivity of this energy demand and supply is often not appreciated. The National Grid isn’t like a constantly flowing river of electricity supply that you can just scoop a bucket of energy out of when it pleases, it’s more like a tap which is turned on and off in accordance with energy demand. Energy supply must balance energy demand – and energy demand is changing all of the time. This ‘tap’ is controlled by a combination of the National Grid – controlling the high voltage ‘transmission network’ and the distribution network operators (DNOs) – controlling the more local, lower voltage ‘distribution network’. But ultimately it is the National Grid controlling the generation of energy and how much of it we need at any one time. They are able to see the fluctuations in demand throughout the day and can identify small spikes, for example, relating to the end of EastEnders when everyone gets up at the same time and boils the kettle to make a cup of tea. Over the course of the day there are repetitive patterns in energy demand with people using more electricity in the day and less energy late at night when people are asleep. And energy demand does not just vary on a daily basis but also on an annual basis, with far more electricity required in the winter months with colder and darker days.
Thinking now about the energy supply, it’s no good having only enough power stations to generate the average electricity demands over the year, you need a large enough supply network to meet peak energy demands. So meeting these ever changing demands naturally involves the turning on and off of power stations. If the energy demand was absolutely constant over the course of the year, we could make do with fewer power stations.
Some power stations are on all of the time, providing a uniform amount of energy constantly. This is called the ‘base supply’. This base supply includes nuclear power stations (currently accounting for about 20% of all electricity supply), which are not easy to turn off and on, so are left generating energy at a fairly constant rate. Then we have renewables, which as it stands, do not provide the remaining necessary electricity supply. Over the past year renewables (wind, solar and hydroelectricity), have accounted for around 25% of electricity supply. But this is a percentage which is changing all the time depending on when it’s windy and sunny. (I’ve just clicked on ‘The National Grid: Live Status’ website and renewables have accounted for 50.7% of energy generation over the past day – the 28th of June.) This means that the remaining supply to meet demand is also changing all of the time. In the UK this comes largely from natural gas accounting for 36% of the energy mix in the past year (fossil fuels make up 38% in total), but also from some biomass (7%) and ‘interconnections’ – imported energy from other countries such as France (9%). These bits are what I like to think as ‘the tap bits’, which constantly needs adjusting to ensure supply meets demand, and controlling this tap is the key job of the National Grid. If supply fails to meet demand altogether we would have ‘rolling black outs’ where some properties experience power cuts. In the UK, it’s easy to forget, these power cuts don’t happen very often and if they do, are most likely the result of a power plant or power line fault. How many power cuts can you remember having in the past five years? Probably not many.
So a well done and a thank you to the National Grid I suppose! But as we move to more renewables how will the grid cope? We are effectively asking the National Grid to substitute this handy natural gas which can be burnt quickly and easily to meet electricity demands, for these temperamental renewables which are annoyingly changing all of the time. Not an easy transition to make!
This is where energy flexibility and energy storage comes in. A massive topic that I’m going to split over multiple blogs – but to get across the broad idea, let’s quickly think of two imaginary reservoirs. Two massive reservoirs, adjacent to each other, one a thousand meters above the other. The bottom reservoir is full of water and the top one is empty. Now, imagine that this is also a future utopia where we have achieved 100% renewables. Yay! Sometimes when it’s windy and sunny, we are producing more energy than we need and sometimes the renewables are falling short of demand. We can use the excess energy in windy and sunny conditions to pump water from the low reservoir to the high one. Then on days when renewables aren’t quite cutting it, we can empty the top reservoir and send the water back to the bottom one and, as we do so, generate hydroelectricity to make up for the lacking wind and solar electricity.
(In case you’re interested… I’ve just estimated that if both reservoirs were the size of Loch Lomond, this hypothetical system (operating with 100% efficiency), would have an energy storage capacity of 26 quadrillion Joules or 7.2 TWh of energy. The equivalent capacity of 144 million Tesla model 3 batteries.)
This imaginary reservoir system is indeed hypothetical, but not as far-fetched as you may think. Pumped storage is in fact a real method used for energy storage and is currently by far the most significant form of energy storage globally. But as you can imagine, it is a bit geographically restrictive. However, there are many other forms of energy storage which can help solve the intermittency renewable problem. One alternative form is in using actual batteries. Unlike the super fancy lithium-ion batteries in new electric vehicles, they don’t have to be super light weight and compact for grid storage, so energy density is not so important and can exist in various cheaper chemical compositions, such as the more traditional lead-acid battery. Other energy storage alternatives include: compressed air energy storage, flywheels, chemical energy storage, high temperature thermal energy storage, electromagnetic storage, and the list goes on…
Further to all this storage capacity, the grid is getting smarter all of the time. Perhaps you’ve heard this ‘Smart Grid’ phrase before, but what does it mean? Well, people at the National Grid prefer the phrase ‘Smarter Grid’ because they like to think it’s already quite sophisticated, but fundamentally the supply needs to get smarter as the demand gets more complicated. More complicated because we will no longer have a simple fossil fuel energy mix with easily adjustable supply and a predictable demand. Rather we will have intermittent renewables with individual consumers generating their own electricity, storing it and feeding some of it back to the grid, alongside changes in heating and the drastic and inevitable rise of electric vehicles. So to facilitate this increasing complexity the grid is becoming more automated with computers predicting demand and sensitively optimising the supply from the many energy sources, with a constant, two way communication of information between the utility and the consumers. It is also simultaneously optimising when energy supply should be directed towards supply and when it should be stored. It does this by considering what all the other energy sources are doing, what they will be doing (using weather forecasts) and how to match this predicted future supply against predicted future demand. Increased quantities of data (e.g. from smart meters) and developments in machine learning and artificial intelligence are allowing this optimisation to become more sophisticated all of the time, reducing the amount of wasted energy and increasing the cost-effectiveness of the assets – all good stuff.
ALSO… ‘The European Super Grid’. This is an idea under conception whereby interconnections could be greatly improved with long, super high voltage, direct current power lines (reducing energy losses), which would improve interconnectedness across Europe and, again with more clever computers, will be able to balance demand more easily. So, for example, when it’s not very windy in England, it may be very sunny in Spain, so they could send us some of their excess solar energy, and then vice versa when we are producing a load of wind and their solar arrays are failing to meet demand. Anyway, you get the idea, there are plenty of promising ideas out there which can be implemented to improve energy flexibility. (Energy storage, smart grids and the European super grid will all certainly be discussed in more detail in future blogs).
One final question to consider… is it possible to implement more renewables now, before we have this improved energy flexibility? Theoretically, yes it is. One (simplistic) solution would be to have far more wind and solar farms than we would need to meet average energy demands so that we could meet peak energy demands even when it wasn’t that windy or sunny. But clearly this is very wasteful and not financially advisable. Additionally, turning off these renewable sources when we are producing too much energy costs a lot of money and again is a waste of assets. Other renewables, such as tidal, are more predictable and could help to alleviate the intermittency of wind and solar. There’s the simple idea that if you had a diverse enough renewable energy mix, you’d always have some sources producing enough energy whilst others were not. This is no doubt an important consideration, but a lot of these other renewable technologies are still in relatively primitive stages of development and pushing ahead with lots more wind and solar, whilst increasing storage capacity, seems like the most financially logical and immediate thing to do.
The UK recently reached a milestone in renewable energy generation. During one weekend this May, Britain was producing electricity with its lowest ever carbon intensity (33g/kWh). This was in part due to lower overall energy consumption due to the Coronavirus lockdown, allowing renewables to make up a larger portion of the energy mix, but also due to a fantastic combination of sunny and windy weather. At this time the country also saw negative electricity prices. Yes, that’s right – some people were not paying to use electricity but rather being payed to use electricity. This is not the first time electricity prices have been negative but it’s the most negative they’ve ever been, at minus £9.92 per MWh. But why would the energy suppliers ever pay consumers to use electricity you may be wondering. The answer is because it’s cheaper to do this than turn off the wind turbines. So although negative energy prices sounds great, it’s clearly not the most financially sustainable set up. To me, this is effectively telling us it really is time to invest significantly in energy storage – to keep this increasingly frequent excess energy and accommodate the encouraging rise of renewables.
This all perhaps sounds quite conclusive then. It seems fairly obvious what needs to happen now and where money should be spent. But I assure you there’s lots more juicy detail – technologies and innovations I’m keen to learn more about and discuss here. I have just made a quick ‘blog plan’ to make sure I can think about enough topics to sustain a prolonged blog. In about ten minutes of thinking off the top of my head, I thought of fifteen massive topics, each worthy of their own blog. So I think I don’t need to worry about a lack of material!
Some of these topics include: more on energy storage, decentralised changes in energy use, the role of nuclear energy, the role of gas with carbon capture, energy efficiency, new build properties, green cities, low-carbon heating, the electrification of almost everything, and many other highly relevant topics.
I want to make clear that all of this will be a learning process for me, I’m no expert on any one of these topics. Therefore if you spot anything inaccurate in any of the blogs please let me know and leave a comment!
Next time I plan to talk more about the different energy storage technologies. As we’ve seen here, that’s the thing that’s really going to allow renewables to take off. See you then!