The hot topic: Where does heating fit into a low-carbon electricity network?
The decarbonisation of the UK's electricity network is set to have significant implications for how low carbon heat is delivered to the buildings of the future. These changes will likely influence new policy from the Greater London Authority, as well as national guidance, regulations and calculation methodologies. The way that London responds to delivering low carbon heat needs to evolve over the coming months and years.
Looking at how different systems compare is a good place to start. According to the national calculation method (SAP), which is proposing to use average grid emission factors, gas fired Combined Heat and Power (CHP) could have the highest calculated CO2 emissions compared to other heating options going forward. CHP is currently one of the most commonly used low-carbon heat sources, but the decarbonisation of the electrical grid will change that. Based on the same proposed calculation methodology, direct electric heating solutions will start, for the first time, to provide carbon emission savings.
While direct electric could offer a very low cost solution for developers, wide spread use of electricity for heating will have a substantial impact on the electrical grid with the possibility of reinforcement costs being passed onto consumers through higher tariffs. All of this is set against the reality of a dynamic electrical grid, where taking an average view does not provide a robust driver for technology choice.
One thing is clear – heating our buildings is currently responsible for 30% of UK CO2 emissions. This needs to be reduced to almost zero by 2050. Gas boilers currently take around an 80% share of the heating market and this will need to be one of the first things to be replaced. The question is - what will replace it? Future options include an uptake in heat networks, a switch to heat pumps or even greening the gas grid. These technologies will then need to be applied to new and existing homes across the UK.
Other challenges that need to be taken into consideration include overheating risk from buildings with excessive, and unshaded, glazing and lack of effective ventilation. Poor heat network design is another challenge, as it can lead to high costs, variable carbon emissions, and overheating. This leads in turn to negative public perception about heat networks, lowering consumer satisfaction and trust. Air-quality is another growing concern, especially in densely populated cities such as London. Addressing these measures needs to be given priority alongside resolving the significant efficiency improvements required in existing building stock.
It is becoming increasingly clear that electrically led heat pump based heating is suited to new builds, which are generally highly efficient. Heat pumps could also be used to feed district heating networks, especially if there are natural heat sources or even waste heat sources available (e.g. sewers, tube lines, recycling centres). In addition, it must be noted that there is still a place for CHP systems, especially if electrically lead, with energy storage. CHP generates electricity, which often helps the financial case for heat networks. Combined with energy storage solutions, this could be a real game changer in low carbon design, allowing us to maximise carbon savings and minimise costs.
Planning for a low carbon future, including guessing what the national heat strategy will be in 50 years’ is not possible. Instead we must allow for the evolution of flexible systems. We should not rely solely on decarbonising the electrical grid, as the implications of everyone adopting electrical heating will cause a dramatic rise in electrical demand, possibly leading to a more carbonised grid. Neither should we be blinkered by the more traditional approach to low carbon design. We need to recognise that the electrical grid is decarbonising, but with future policy, technology, energy costs and incentives being uncertain; our designs need to be flexible, allowing us to adapt to the ever changing nature of the UK energy mix.
 Based the SAP 2016 consultation
 DBEIS – Final UK greenhouse gas emissions national stats 1990-2015
Channa Karunaratne is an associate director at AECOM