As we move towards net zero, energy storage will become a central focus – and buildings will need to become part of a flexible and integrated storage and supply system
There are many reasons to mentally divide the massive effort to decarbonise the economy into a series of discrete tasks, looking individually at each sector, be that transport, utilities, housing, commercial buildings or industry.
It provides multiple focal points for action. It helps assess where effort is most needed and where to target incentives. As policies are formed, it helps government work out how initiatives might be funded and who will bear the burden in a way that somehow looks fair and politically acceptable.
But lift the lid on the various parts of the economy and it soon becomes clear that everything is intimately connected. Obviously. That’s the world for you.
This helps explains why policy formulation is increasingly turning to a whole-system approach, with the Climate Change Committee stressing that for the government it is an imperative to avoid unintended consequences. Meanwhile, the Carbon Trust’s Flexibility in Great Britain report, released this summer, illustrates the huge savings and efficiencies that flow from a whole-system approach.
Taking a more holistic approach can throw up unexpected optimal solutions. Some may run against our instincts, others may on reflection seem obvious. This becomes very evident when we examine the link between the electricity grid and housing.
We may be used to flicking a switch and the power coming on, but as the Carbon Trust highlights, the idea of homes as relatively passive consumers of energy looks like being over. Buildings, especially homes, need to become part of a flexible and integrated energy system, where they store and increasingly generate energy as well as consume it.
To understand what this means we need to look at the way the energy supply is changing and how we plan our quickest route to net zero. Clearly cutting emissions is a major part, but buildings will need to play a wider role.
Looking at the bigger picture, the UK has made big early strides, as the government regularly reminds us, in reducing its CO2 emissions. But later strides will be a great deal tougher to achieve.
Chart 1 shows how, since the United Nations Framework Convention on Climate Change came into force in 1994, the UK has cut CO2 emissions by around 45%. These are the territorial emissions, directly from the UK. The cut in emissions associated with consumption is less impressive, at around 30%. This difference is caused by trade. The UK, like many richer nations, increasingly exports services and imports goods that generate CO2 during production from countries such as China.
The big cuts made by the UK, as Chart 2 shows, are within the energy generation sector. Emissions are less than half what they were a decade ago. Renewables now produce more electricity than fossil fuels, as Chart 3 shows. Wind energy, on the back of gathered momentum at the turn of the century, is set to top gas as the biggest single source of energy over the next few years as the progress to decarbonisation continues.
Other sectors contributed far less to meeting net zero. The drop in emissions from business partly reflects our changing economy which, through trade, transfers the emissions consumed to other countries. Cuts in emissions within transport and housing are piffling compared with the challenge, and arguably depressing given the supposed efforts made over decades.
We can expect transport to see big cuts as electric vehicles become the norm. Tackling housing poses bigger problems given the age of the UK housing stock. Retrofitting and replacing fossil fuels with electrically powered heating such as heat pumps comes with a hefty price tag and both political and technical challenges.
However things pan out, decarbonising both transport and housing points to ramping up the electricity supply to replace the fossil fuels. And here’s the rub. Historically, flexibility to meet peaks and troughs in demand was provided by large-scale power plants, many powered by gas which could be turned on and off relatively freely. Shifting to erratic sources of energy takes us into a new world where the supply is determined by the whims of nature. If we are to avoid having to build in huge overcapacity to cope with peak demand when nature is being parsimonious, greater flexibility, greater integration, and far more storage become essential.
The broad thinking is that we can store some of the energy in pumping water uphill ready to drive turbines, as we do already. We could use fly wheels. That might provide some smoothing. Also, wind power can be used to create hydrogen through electrolysis. The hydrogen can be stored and used either for transport, industry, or home heating, lowering the demand for electricity.
But recent analysis by the Carbon Trust suggests we need to go much further in storing energy and drawing on supplies in a smarter manner to smooth out the peaks and troughs inherent in both solar and wind power. It reckons providing greater flexibility could cut the bill to provide a net-zero energy system by £16.7 billion a year, which on its figures comes out at about 13%.
In future, homes will have to store energy, either as heat or in batteries. Quaintly, this in many ways takes us back a generation or three, when storing energy was the norm – then it was most likely to be storing coal in cellars or sheds.
However, the direction of travel suggests homes in future will not simply be stores of energy. They look likely to become an integral part of the supply system. Automatic installation of energy storage will lower the leap to home generation, with battery storage collecting energy from domestic solar pv.
The battery storage needed to ensure flexibility need not necessarily be within the home. Huge attention is being paid to the vast quantities of energy likely to be stored in electric car batteries. The ability to charge these when capacity outstrips demand and draw on them when demand outstrips capacity provides huge potential for balancing supply and demand.
As things stand, the batteries currently installed in cars could run a house for two days or more. There is already a growing market for electric car batteries when they begin to lose their vitality. Many are being repurposed for home energy storage.
This more local approach to supply will provide a further bonus on the route to net zero. It will reduce transmission losses, which amount to about 8% of the electricity supplied, again making the journey to net zero more manageable.
Looking beyond the electricity supply system, with homes becoming a store not only of electricity but of heat, hot water tanks are envisaged as a means of managing demand. Certainly, Carbon Trust’s report sees hot water tanks being used extensively in homes, either within homes or as part of a district heating system.
Inevitably, this means seeing homes much more as sources, sinks and storage for energy and heat, rather than perhaps we have. This, in turn, alters how we address the supply of energy and moderating heat levels, as the climate alters through global warming. It also means more careful consideration, if electric cars are to become a major store of electrical energy, of how we integrate cars and car charging.
It is far from clear how this will feed through as changes in the way we configure our new buildings, especially housing, and how we reconfigure the existing stock. But it will warm the hearts of many architects that it should make us think more deeply about the huge, often hidden, value that lies in the interconnectedness inherent within the built environment.