With battery storage able to provide a unique role in balancing a renewable electricity grid, Toby Gill, CEO of Intelligent Power Generation, asks could innovations in green hydrogen and biofuel technologies contribute to a more optimised and economical energy mix?
The growth of global industrialisation, increasing demand on energy resources and rising carbon emissions are deepening the need for energy infrastructure that is increasingly green, distributed, flexible, and resilient.
As our world becomes more connected, more electrified, and more renewable, not only are we increasing the demand on our energy systems, but we are also fundamentally changing the way they operate.
We are transitioning from a demand-led energy system, where power generation can be easily turned on and off to match demand, to one that is led by supply from variable and inflexible sources. As a result, grid balancing is now becoming more complex, whilst resilience and reliability all the more important.
The challenge, now, is in establishing a renewable energy mix that can effectively and economically balance supply and demand season-by-season, week-by-week, hour-by-hour and second-by-second.
Localised balancing is not a new problem
Grid balancing and resilience is not a challenge borne out of our transition to a net-zero carbon economy. It is, however, a challenge that is being made all the greater as we continue to decentralise power generation with more distributed, variable and inflexible sources, such as wind and solar.
Grid balancing is about ensuring electricity supply meets demand second-by-second, by regulating properties including power, voltage and frequency. This is to ensure that electricity is always there to safely power everything from industrial plants to the wall sockets in our homes and offices.
For grid operators, the macro trends in power demand can be easy to predict, and therefore easier to balance. For example, demand will often increase when is it raining or peak during half time of a national televised sporting event. But what is difficult to predict is the localised and short-term variations in this projected demand. This is why balancing mechanisms are used to match supply from the centralised power sources with consumption at a local scale.
This varying demand on the electricity grid is managed by different balancing mechanisms, with some more suited to specific changes in demand than others. One example is diesel and natural gas generators, that are plugged into local transformers. These “dispatchable” forms of power generation can respond to changes in demand in as little as 5 minutes, making them suited to balance those difficult-to-predict peaks.
Our grid is changing, and so must the way we operate it
So how is our grid changing, given our drive towards renewable power generation and the decarbonisation of our energy systems?
Increasingly, wind and solar are replacing fossil fuels as our principle source of energy. They not only afford us some of the cheapest energy we can produce but also a route to the low-carbon power necessary to achieving global decarbonisation targets.
These renewable energy sources, however, are fundamentally distinct from our traditional forms of power generation. The power outputs of wind and solar are intermittent, fluctuating according to real-time availability, whilst infrastructure must be built in specific locations. This creates an energy system more variable and more distributed than we’ve previously operated.
We are no longer working with an energy system that can be led only by predictions in demand, but one that needs to establish a new set of mechanisms that can effectively and economically balance this demand uncertainty with a newfound uncertainty in supply.
What are the mechanisms we need to balance a renewable grid?
100% wind and solar is not feasible on its own
There is more than sufficient wind and solar power potential to exceed demand. In Europe, for example, on- and off-shore wind energy potential is estimated to be ten times greater than the annual demand.1
It is argued, therefore, that with this power potential, we can create enough excess in wind and solar power that the statistical likelihood of not having the power supply to match demand is effectively zero. However, wind and solar generation is location specific, and it is not as simple as transmitting wind power from Scotland to power homes in London.
With the yearly average of wind power in the UK at around 30% of power potential,2 at first glance, it may seem we only need 3-4 times as much infrastructure to ensure we have the minimum power requirement for the nation. But, if you look a specific areas in the UK, take London, the daily wind power output could be far lower, and therefore the need will not be 3-4 times, but far greater.
In this scenario, therefore, we would have to vastly oversize our wind and solar infrastructure to ensure we can deliver the absolute minimum power requirement for those worst case scenarios.
Battery storage can optimise the energy mix, but is also limited
We are all becoming increasingly familiar with the narrative that, energy storage is thesolution for balancing a distributed and renewable grid, therefore reducing the need for vastly oversized infrastructure.
Batteries are one mechanism for doing this, as they store power, when wind and solar generation outstrips demand, and use this to balance the grid when demand outweighs supply. They also have the unique ability to discharge power within the millisecond, and effectively balance the second-by-second variations in output. A fuel-based generator cannot turn on quick enough to respond to these types of changes.
But, to solve the week-by-week or season-by-season variations with batteries is to follow the same route as a 100% wind and solar powered grid. Again, to scale battery storage to store the weeks and weeks of power needed to balance the grid in those situations would result in huge infrastructure requirements.
Therefore, in the scenario above, batteries enable you to significantly reduce the oversizing of wind and solar infrastructure, whilst ensuring the minimum power requirement. But in those longer timeframes and locations farther from energy sources, the question becomes: is a system that only has wind, solar and battery storage the most optimised and economical one we can create?
Hydrogen and biofuels offer another form of renewable energy storage to further optimised our energy system
Wind, solar and battery storage are not the most optimised solution, not when we have a route to net-zero, demand-responsive power with fuels such as hydrogen and biofuels. These renewable fuels can be a more energy dense and more cost-effective energy storage medium for balancing supply and demand not just in those longer timeframes, but across the spectrum of intermittency.
The challenge in using renewable fuels today is twofold. Firstly, the timelines to the abundant availability of renewable fuels that are economical to produce and environmentally sustainable is uncertain. This creates risk around investing in fuel infrastructure today that could become redundant tomorrow. Equally, any technology currently available, for burning these renewable fuels, uses a flame during the combustion process, producing the pollutant emissions that are harmful to human health.
We need, therefore, technologies and solutions that offer fuel-flexibility in order to de-risk the transition to renewable fuels, as well as ones that do not compromise our clean air ambitions. Hydrogen fuel cells go some way to answering these challenges, but breakthroughs in flameless combustion and low-cost, high-temperature ceramics offer an alternative solution.
We can, then, continue to use the localised dispatchable power generation that we have always used but do so with renewable fuels. As with batteries, renewable fuel-based power offers a further opportunity to optimise our energy system and reduce the total amount of infrastructure needed.
A hybrid system of wind, solar, batteries and renewable fuel-based power is the solution for a resilient, optimised and stable energy system
As the world strives to decarbonise and mitigate our climate impact, one of our key goals is to ensure sustainable, secure and affordable energy. Renewable fuels, and innovations in the technologies that operate them, offer a road map to reinventing fuel-based power generation to help achieve this future. An energy system that uses wind, solar, battery storage and renewable fuel-based power is not only more optimised and stable, but one that is decarbonised and affordable too.
Let us not, therefore, discard fuel-based power as a tool of the past, but one that can evolve to help us achieve a resilient and secure net-zero future.
1 Swart, R. J., et al. Europe’s onshore and offshore wind energy potential, an assessment of environmental and economic constraints. No. 6/2009. European Environment Agency, 2009.
2 Renewable UK, Wind Energy Statistics Explained, available at: https://www.renewableuk.com/page/UKWEDExplained#:~:text=The%20load%20factor%20is%20calculated,onshore%20wind%3A%2026.62%25, accessed 12th November, 2020