BSEE
ENERGY OPTIMISATION
Hard electrification vs sector coupling
The UK can choose between hard electrificaon or sector coupling as the basis for its decarbonisaon strategy. David Bradbury, content manager of SAV Systems, explores the issues
n recent years, the UK has seen impressive growth in the use of renewable energy sources, particularly wind power. Although this has produced some useful sound bites for politicians, it has also led to the nation’s energy being viewed solely in terms of electricity, detracting from a more meaningful view of the full picture. This is unfortunate, as concentrating only on electricity (so-called ‘hard electrification’) makes it very difficult to balance the electricity grid. It creates a critical bottleneck in the transmission and distribution of renewable energy, imposing severe constraints as the UK tries to deliver on its decarbonisation agenda. A ‘sector coupling’ strategy is a more holistic and cost-effective approach to energy usage. It also addresses the UK’s ‘Energy Trilemma’: the need to ensure security of supply, reduce carbon emissions and cut the costs of energy. It also reinforces the key role of heat networks in the UK’s decarbonisation strategy.
I
The pros and cons of wind power
Undoubtedly, wind power has played a major role in the green transition up till now. It is virtually zero carbon and can deliver energy at a fraction of the cost associated with conventional sources. However, as wind generation capacity has grown, the transmission
infrastructure has failed to keep up. This is not surprising, when comparing the timescales involved. For example, a wind farm can be built in a couple of years after authorisation, but it can take 10 years or more to plan and install a large transmission line. New power lines tend to be unpopular with the public (and thus with politicians), which is a further reason why such infrastructure might be delayed. This transmission bottleneck means that wind generation cannot always be fully accommodated, leading to wind farm operators receiving large constraint payments in compensation for reducing output. During 2019,
26 BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2020
such curtailment cost the country over £1 billion.
There will be times when the wind fails and the sun is obscured, giving rise to the need for standby storage and back-up capacity. Although the UK has significant back-up resources, these are mostly in the form of gas power stations, situated in remote locations. When it comes to electricity storage, this sector is in its infancy with some serious R & D effort still required before results can be expected.
Hard electrification vs sector coupling
The concept of hard electrification requires that electricity should be the sole energy source for all points of demand that are within reasonable reach of the electricity grid. This means the mass electrification of heating for buildings, with wholesale
abandonment of gas boilers. It also calls for the replacement of the nation’s car fleet by electric vehicles. The infrastructure costs associated with hard electrification would therefore be very considerable.
On the other hand, a sector coupling approach is based on the interaction between networks for power, gas and district heating (with district cooling as a further option at a later stage). There is provision for the conversion of energy between networks, with large- scale storage `providing a vital balancing function.
Of the two, the hard electrification option is expected to be significantly more expensive. For instance, in Germany it has been calculated that the transition by 2050 to a well- integrated, sector-coupled energy system would be 600 billion euros cheaper than a system that is strongly dependent on electricity.
“Power to X”
The crucial difference between hard electrification and sector coupling is that the former requires storage using ‘power to power’ technologies (such as batteries), whereas sector coupling uses
‘power to X’ solutions (which means either power-to-heat or power-to-gas). Power-to-heat involves the conversion of electrical power to hot water in heat networks at times of abundant wind or solar generation, using large scale heat pumps and/or electric boilers. The hot water is then sent to storage, where it plays a key role in balancing energy supply and demand. This mechanism is an important part of sector coupling. Power-to-gas using renewable electricity produces zero-carbon fuels, which can be deployed in the UK’s established gas network. Electrolysis of water has already been developed for the commercial production of hydrogen and this can be used to partly replace natural gas, without compromising safety. Using the Sabatier process, hydrogen can then be combined with atmospheric carbon dioxide to produce methane, to replace natural gas completely.
Summary
The contrast in cost and carbon between hard electrification and sector coupling is significant, and therefore the UK needs to consider its options very carefully. Sector coupling is based on mature technologies and is pragmatic in its ability to build on the UK’s existing energy infrastructure. It also has the inherent flexibility to incorporate future innovation, whilst addressing the three elements of the UK’s Energy Trilemma.
To realise the full potential of sector coupling, will need policy to be in alignment and also encouragement by government, with removal of existing techno-economic and regulatory barriers. Sector coupling will not happen on its own!
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The contrast in
cost and carbon between hard electrificaon and sector coupling is significant, and therefore the UK needs to consider its opons very carefully
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