Today is Energy Efficiency Day, and we are taking a look at some of the ways in which the UK's energy grid might be adapted to be more efficient and resilient as we transition to cleaner, greener sources of power.
Much of the discussion around reducing carbon emissions from power and heat generation focuses on questions of generation. How much electricity can we generate from wind and solar? What role will hydrogen and nuclear power play in our future energy supply? However, an aspect that is sometimes forgotten is the effect that these changes will have on the infrastructure used to transmit and store energy.
Perhaps the most visible part of the UK's national energy grid is the thousands of kilometres of cables carrying high-voltage alternating current (AC) electricity. However, the grid also comprises a variety of other elements such as high-capacity interconnectors to the island of Ireland and countries on the continent, as well as storage facilities such as the well-known Dinorwig pumped-storage hydroelectric station in North Wales. Alongside (or underneath) the electricity grid runs the network of gas pipelines that supply natural gas to industrial and domestic consumers around the UK. Many of these components will be affected as the mix of energy generation changes over the coming years.
To investigate how the gas and electricity grids might be adapted to cope with future changes, Ofgem (the UK's energy regulator) has announced L8 million of funding to support 18 innovative new projects under its Strategic Innovation Fund. This article explores various aspects of the energy infrastructure covered by these projects.
Electrical transmission lines usually transmit AC at hundreds of thousands of volts. AC is used because many common forms of power generation produce AC using turbines. It can also be stepped up or down in voltage relatively easily compared to direct current (DC). However, AC also has disadvantages in certain situations.
When transmitting power over very long distances, the capacitance of insulated underground or undersea power cables can cause significant power loss when using AC. These losses can be reduced by instead using high-voltage DC (HVDC) in long transmission lines where there is no need to tap off power and reduce its voltage at regular points along the line.
The UK has huge potential for wind power generation and already has the three largest offshore wind farms in the world. To reduce transmission losses, offshore wind farms are usually connected to the mainland by HVDC cables. However, this requires connector stations where the cables make landfall to convert HVDC back to AC and feed into the national transmission grid. These stations are costly to maintain, disruptive to coastal communities, and necessarily cause losses in converting DC to AC.
One of the projects funded by Ofgem seeks to improve the infrastructure that connects offshore wind farms to the grid by connecting offshore wind farms together via HVDC connections. This could reduce the number of coastal connector stations needed, reducing disruption and maintenance costs. It may also allow wind farms to be located further offshore, connected via an offshore HVDC network. Achieving this requires improvements in technologies such as DC circuit breakers that can safely switch HVDC lines to isolate sections of the HVDC grid when necessary.
AC must also be transmitted at a particular frequency, which in the UK is 50Hz. Fluctuations in frequency can occur due to changes in load or generation capacity and the grid must be carefully managed to ensure that the frequency stays close to its intended value. Significant changes in grid frequency can have dangerous and damaging consequences for network infrastructure and electrical equipment connected to the grid.
Some renewable energy sources such as wind are inherently more variable in their power output than sources such as fossil fuel or nuclear. Although this variability can be reduced by scaling up generation capacity, it will still be necessary to improve the resilience of the grid to short and medium-term fluctuations to maintain frequency stability. Another one of Ofgem's funded projects aims to improve infrastructure for grid stabilisation by developing battery-storage and super-capacitor technology, for example for deployment at the coastal connector stations of large wind farms.
Nearly 80% of heating for buildings in the UK relies on natural gas, provided via a national network of gas pipelines. This dependence will need to change to meet net zero targets, and the UK has already announced that newly-built homes will not be allowed to have gas boilers from 2025. These changes are likely to mean much more heating provided using electricity, either directly or using technologies such as heat pumps. This will further increase the demands on the electricity grid. Improvements to the efficiency of heating would help manage the increased demand.
One of the projects funded by Ofgem will investigate thermal energy storage. This is not a new idea, and many people might be familiar with electric storage heaters. These heat up a concrete block at night when electricity is cheaper and release the heat again during the day. However, this idea could be deployed on a much larger scale in future in combination with renewable power generation. For example, solar energy or excess electricity from wind could be used to heat up a large, insulated volume of rock, water, or even molten salt. The stored heat can then be released later to heat buildings or generate electricity. Longer-term storage facilities may even be able to store heat in summer for release during winter. This would reduce the overall energy requirements for providing the same level of heating to buildings.
The Department for Business, Energy & Industrial Strategy has also recently reaffirmed its commitment to expanding heat networks in future UK housing developments. Again, heat networks (also known as district heating) are not a new idea. They are already commonly used in Iceland and Sweden, and work by distributing centrally-generated heat to nearby buildings. This type of network is obviously most useful in densely-populated areas such as cities, and can provide savings in heat generation by allowing the use of larger, more efficient centralised facilities. Combining heat networks with large-scale thermal storage may further reduce the overall power requirements for heating buildings in future.
How much of a role hydrogen will play in our future energy mix is still uncertain. In particular, to be effective in contributing to net zero, hydrogen needs to come from renewable sources such as electrolysing water with renewably-generated electricity. However, it is clear that hydrogen does share some advantages with fuels like natural gas, petrol, and diesel in its relatively high energy density and ease of transport and storage compared to electric batteries. This makes it potentially attractive as a fuel for long-distance transport applications such as road haulage, marine shipping, and rail.
One project funded by Ofgem will investigate the practicalities of distributing hydrogen for use in the UK's railways. This may involve a network of hydrogen storage facilities, which could be connected to the existing gas distribution infrastructure once it is repurposed for hydrogen. Hydrogen-powered trains could then be refuelled at these depots, replacing current diesel trains on sections of track where electrification is too difficult or expensive.
The UK has expressed interest in repurposing its existing natural gas distribution infrastructure for distributing hydrogen. Reusing the existing network would save money and potentially reduce disruption to consumers, allowing them to replace gas boilers with hydrogen boilers. Such replacement would avoid the need to completely renovate their central heating system and home insulation, as can be necessary when switching to heat pumps.
However, an abrupt switch from natural gas to hydrogen is unlikely. Instead, it is more likely that a mixture of natural gas and hydrogen will initially be distributed, with the proportion of hydrogen being gradually increased over time. Another project funded by Ofgem will investigate the feasibility of local deblending facilities that can separate the natural gas and hydrogen at the point of use. This could allow the existing gas infrastructure to support applications such as hydrogen vehicles, which require high-purity hydrogen, throughout the switchover process.
However the switch to net zero is achieved, it is clear that developments in technology to improve the efficiency of energy storage and distribution will play an important role in adapting our power infrastructure to the requirements of generating our heat and electricity from renewable energy sources. As mentioned in our wind power insight, disputes over green technologies are already occurring. Such disputes are likely to become more common as investment in the transition to net zero grows. To avoid these disputes and put yourself in the strongest possible position when they do occur, it is important to properly manage your intellectual property and ensure it is protected by registered rights wherever appropriate.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
Mr Richard Morris
J A Kemp LLP
14 South Square
Tel: 203077 8600