In just five years time renewables are expected to overtake coal to become the largest source of electricity generation worldwide, supplying one third of the total. Andrew Cripps, director sustainability, buildings and places at AECOM, part of the Triple Point Heat Networks Investment Management team delivering the Heat Networks Investment Project says this will require more flexible energy systems and heat storage can play an important role.
The International Energy Agency (IEA) says that Covid-19 is ‘hurting – but not halting – global renewable energy growth’ and renewable technology costs are continuing to decline. The resilience, adaptive capacity and forecasted growth of renewables needs to be harnessed and utilised to drive global emissions down to net zero. But matching variable renewables with variable demand calls for a more flexible energy system. Luckily, some solutions are already available and in common use.
In its Sixth Carbon Budget the Committee on Climate Change stated that, “the shift to electrification and heat networks can also deliver improved energy security and improved air quality”.
Heat networks allow a range of low-carbon heat sources to be used individually, or in combination in a single network. Thermal energy storage can be used to help match supply to demand, improving their efficiency and flexibility. They are technology agnostic, but are increasingly being supplied by heat pumps which provide an efficient way of heating multiple homes with renewable electricity.
Heat network flexibility can be obtained, amongst other methods, by integrating thermal energy storage in district heating systems. This allows a scheme to take advantage of periods of high availability (and low cost) of renewable energy, by using morepower to store extra heat . The scheme can reducepower demand and rely on stored heat when renewable energy is scarce or more expensive, and may earn extra income from grid services.
By supporting the grid at scale, a heat network can help in a way that single heat pumps cannot. Centrally located, thermal energy storage can provide value to district heat systems.
Energy flexibility in thermal networks can be offered by many sources, ranging from dedicated storage systems (e.g. tanks and aquifers), to the thermal energy storage inherently present in the network, building thermal inertia and network pipes containing warm water.In some countries, the majority of district heating systems have controllable thermal storage tanks.
There is a growing interest, both in Europe and China, for the use of short-term storage in district heating to provide flexibility, particularly in the form of ancillary services to the electricity grid, but implementations of these techniques are rare.
The recent announcement from the Climate Change Committee (CCC) of its Sixth Carbon Budget highlights the opportunity for heat network development. The sector will have to embrace demand side response and flexibility. A number of heat networks applying for Heat Networks Investment Project (HNIP) funding are incorporating thermal storage and mechanisms to support a more flexible energy system as we transition towards net zero.
In the UK the potential for flexibility from district heating has not yet been fully exploited but it is more common elsewhere - for example, in Sweden as much as 64 % of heat network capacity is available for flexibility services.
New developers need to know that flexible heat projects can be viable and economic. We would like to hear about case studies and projects that demonstrate the principle at work, to add to our examples. With the help of New Power we hope to build a library of examples and make them more visible, to help put heat flexibility on the menu for all new developments.