The National Grid’s Chris Bennett

The UK energy industry faces a tumultuous future. Over the next decade, as most nuclear plant comes offline and many coal-fired power stations close, it will lose up to 20GW (about a quarter) of existing generating capacity.

To replace this was always going to be tricky. But to do so while shoring up energy security and meeting targets that call for 35GW of generation capacity to come from renewable sources by 2020 is a monumental challenge.

Although the nuclear, wind, tidal and other generators hoping to add to the mix face their own technical and political hurdles, it could be argued they have the easy job. Integrating these technologies into the UK’s diverse future energy mix is arguably a far steeper challenge.

That job falls to the National Grid and Chris Bennett, its recently appointed future transmission networks manager. He is responsible for defining a transmission system that can cope with the many possible permutations of the future energy mix.

‘We’re entering a period of unprecedented change,’ he told The Engineer. ‘With regards to the generation mix we recognise that in terms of climate change and security of supply there’s a massive amount of change that’s going to happen and it’s going to have a fundamental impact on transmission.’

Bennett identifies two phases in the evolution of the energy industry. In the short term, the need to meet the energy shortfall and the 2020 renewables targets will result in a huge increase in wind power (from one per cent to 30 per cent of capacity) and some new gas-fired generation.

But for Bennett the key decade is from 2020, when it is all change again. Up to 10GW of new nuclear is expected to have kicked in by 2030. ‘If we’re going to hit the 2050 greenhouse gas targets [of an 80 per cent cut in emissions] we’ve got to get the remaining bits of the dirty coal off the system between 2020 and 2030,’ he said.

Putting the measures in place that will enable the grid to react to these changes requires some flexible thinking. Bennett said: ‘What we’ve been doing is taking those scenarios — with whatever old and new plant we’re assuming to be on the system — and asking ourselves, “what does a transmission system need to look like to actually deliver the amount of new capacity on to the system and maintain security of supply?” ‘

Many of the biggest regulatory and engineering challenges arise from the increasingly important role to be played by renewables.

Fortunately, said Bennett, much can be done with the existing infrastructure. For example, simply rejigging grid-access regulations could help to meet 2020 targets.

In an effort to get more renewables on to the system before infrastructure development, Bennett’s team is helping lead industry debate on reviewing access to the grid.

‘The simple example is wind,’ he said. ‘We could change the access regimes so that wind farms share some of the transmission capacity with the conventional plant. When it’s windy the wind farm uses the transmission capacity and when it’s not the conventional plant uses it.’

The government’s Planning Bill, which aims to streamline the regime for key infrastructure projects, is also expected to help.

‘Our last experience of building a significant piece of new infrastructure, the second Yorkshire line, took us more than 10 years to get through planning and building. If we’re going to meet 2020 targets we need a slicker planning regime and that’s what the Planning Bill is trying to do, by creating a more defined timetable.’

Though such measures will help get some renewables on stream earlier, regulatory and planning reform is just the first step, said Bennett. ‘If we’re going to end up with 35GW of wind, there’s no doubt that we do need transmission investment.’

Bennett and his team are completing a report, due out in January, that will detail many of the key investments required.

Giving The Engineer a flavour of its recommendations, Bennett said one of the biggest engineering challenges will be to address the fact that many of the UK’s most promising renewables resources — wind, tidal and wave — are found far away from the most power-hungry areas.

‘Of the 35GW of renewables, 11.5GW will be built onshore within Scotland so we have been focusing on various scenarios within Scotland,’ he said.

The grid is updating the overhead power lines that carry electricity out of Scotland, but the anticipated torrent of renewable energy is likely to prove too much for these links, and a number of new options are on the table.

One of the most promising solutions is to replace the overhead links with high-voltage direct current (HVDC) sub-sea interconnectors that will run down the coast from Scotland to England. ‘HVDC links to avoid the need for new overhead lines is something that we are looking at very seriously,’ said Bennett.

Though HVDC interconnectors require costly converter stations, the likely length of such a cable would make a subsea link economically viable. Also, its environmental credentials could help ease the scheme through the planning process faster than if approval was being sought for hundreds of miles of pylons and overhead cables.

Interconnectors linking the UK grid with other parts of Europe could also help address energy shortfall issues, believes Bennett. There is already a link with France, and BritNed, an HVDC link with the Dutch grid, is under construction (The Engineer, 13 October). Before long, thinks Bennett, we could see more.

‘If you look at how much plant’s going to be coming off, there’s definitely a need for other forms of generation to connect between now and 2020, and interconnectors, as we’ve shown with BritNed, can be built pretty quickly. It wouldn’t surprise me to see another interconnector.’

Although the grid is backing wind as its primary renewable resource, Bennett is adamant that no form of generation is being ruled out.

‘From a security of supply point of view a diverse supply of electricity has got to be a good thing. We want to facilitate any form of generation coming on to the system. The likelihood for the 2020 target is that it will be wind — but if you take it all the way to 2050 and we’re going to reach this 80 per cent reduction in greenhouse gases, then we need to fully decarbonise the electricity sector. That means a mixture of wind, nuclear and carbon capture.’

This is where the grid’s vision starts spreading beyond its traditional remit. ‘To hit the 2050 targets we believe we should use our decarbonised electricity to decarbonise transport. We’ve got to move to electrical vehicles.

‘We’re not going to hit the targets if we’ve still got petrol, diesel and the like. All forms of decarbonised electricity are going to be crucial to hit the 2050 targets.’

It all sounds a long way off, but Bennett is no crystal ball gazer. To meet these far-off targets work needs to start now, and he is excited about the challenges ahead.

‘I took the job in April. It’s a new position and it’s a great job to have: looking into the future and linking these scenarios in with what it will mean in reality. Although 2020 sounds a long way out, from an engineering point of view we need to start doing some of this stuff now.’