It is well documented that the shift towards a low carbon society will result in a step change in how electricity is generated and consumed across distribution networks. In particular, the uptake of Low Carbon Technologies (LCTs) such as Electric Vehicles, Photovoltaics and Heat Pumps is reducing the available capacity within LV networks and creating a requirement for costly and time consuming network reinforcement. In fact, the potential UK network reinforcement caused by the uptake of Electric Vehicles alone has been estimated to reach £34bn - £48bn by 2040.
Furthermore, these LCTs are connected to an AC distribution network despite the fact that most consume and generate DC power. This creates the requirement for often low efficiency three stage converters between DC devices and the AC network, increasing both network demand and customer losses and equipment cost.
To overcome the challenges discussed above existing LV AC circuits could be converted to DC networks operation to release additional capacity within existing network infrastructure whilst significantly reducing customer losses. In theory, an LV DC distribution network could support longer LV feeders and reduce the number of secondary substations required to supply an area. This is due to improvements in transfer capacity caused by improved circuit voltage drop and increased cable thermal capacity. In addition to this, if the losses associated with EV charging were reduced by only 4% using a DC supply UK consumers could save up to £52m annually by 2040. For targeted applications LV DC network operations could deliver significant value to UK electricity consumers in the near future if innovation funding is invested into its development.
However, there are number of technical and commercial challenges which need to be addressed before LVDC can be fully adopted by UK DNOs as a business as usual (BaU) approach to facilitate the uptake of LCTs. Some of these challenges include:
· The impact on cable ageing when converting existing low voltage AC cables to LV DC at different voltage levels and cable types.
· The optimal LV DC voltage for distribution networks when considering both customers (reduced losses) and network requirements (increased transfer capacity).
· How an increased transfer capacity over distance could benefit and change network design practices i.e. longer LV feeders, less secondary substations, smaller cable etc.
· The H&S requirement for LV DC adoption both within the network and at the point of customer connection.
· The number of opportunities for UK DNOs to convert existing LV AC circuits to DC including a proven Cost Benefit Analysis (CBA) for different applications demonstrating the financial benefit.