Power industry evolution: local energy v long distance transport

The Competition and Markets Authority (CMA) has proposed changes to the way transmission losses are charged among its recommendations to improve competition in the energy industry.

The energy lost in transporting power from centralised generating plants to customers has been a bugbear for many, and in recent years there has been a surge of interest in local energy projects connected to the distribution system, or even on-site. It’s a good thing: power generated where it is used improves efficiency and cuts the cost of the system overall.

But there is more to it than that.

It’s worth remembering why the transmission network grew up. First, it was a more efficient way of running the system: there is a cost to transporting power, but it is much smaller than the cost of transporting bulk fuel – coal, say -  to local generating plants.  So coal-fired plant sites were not chosen at random – they were as close as possible to the mine-mouth. And gas-fired plants are

How it works

It’s also worth remembering that although there are losses in the transmission system, they are far lower than in the distribution system. Why?

In crude terms (and with apologies to electrical engineers) energy loss depends on the current in the wire. And transmission cables carry an extremely tiny current, because current and voltage ‘seesaw’: as one is ‘stepped up’, the other  is ‘stepped down’. In transmission the voltage is stepped up a thousand-fold to 250,000 or 450,000 volts (whereas local networks are as low as 250 volts) and current comes down accordingly.

This electrical property is what allowed us to shift dirty power fossil plants out of towns and cities, and instead transport power back to where it is needed.

And the ability to transmit power like this is even more important for renewables, where there is no option to truck the fuel to the plant. It’s what allows us to take advantage of wind and tidal power, in bulk, from well-supplied places like northern Scotland.

Why it won’t go away

Although the advent of cheap cleaner power like rooftop solar has made local generation more attractive, that doesn’t mean transmission will not become even more important in the coming years.

First, there is that bulk power supply to shift from resources in Scotland and elsewhere.  National Grid says in the future: The transmission network will need new capacity to transport power across Scotland and much of England to meet southern demand.”

Second, power will come from offshore wind farms. We should take advantage of this resource and the good news from early wind farms is that they generate considerably more than we expected. But a connection to a wind farm tens of miles offshore is clearly going to have to transport power from farther than even the most centralised onshore plant.

That’s not the farthest. The government wants interconnectors between the GB system and our neighbours at least to the EU’s recommended level of 15% so we can import (and export) power.  That power may come from just the other side of the channel in France, or could be brought from much farther away if the dream of free trading across Europe is realised. In addition, direct links will certainly see us buying and selling power from Norway  and possibly as far as Iceland.

So our future is mixed. Onsite power will supply far more of our needs. But for some, and to balance weather-dependent generation – even with storage in place – we will be using transmission networks that could bring power over hundreds of even thousands of miles.

This has implications for charging. We still have to have a transmission network, in fact it will be even more extensive than it is now. But we may not use it as much. How do we pay for that in a way that is fair to all parties?

And similarly, local and onsite generation will entirely change the way we use the distribution network – but may not reduce its size, as we will continue to swap power between neighbours or areas, or as conditions change through the day. The same question applies. How do we pay for that in a way that is fair to all parties?