Switched on
Meeting EU-wide renewable energy targets will be a tough challenge but an equal task will be to deliver that green energy where and when it's needed. John Crackett argues that's where the transmission and distribution networks must play their parts
The UK wind industry estimates that it could realistically supply 20GW (approximately 17 per cent of the UK's electricity capacity) by 2020 from offshore wind alone. But despite the fact the UK has excellent wind resources - the strongest in Europe - it's a simple fact that the best areas to generate wind, wave or tidal energy are not necessarily the places with the highest populations or the greatest demand for that power. Our networks were constructed to take power from central plant and distribute it outwards to the coast. Now this is being turned on its head along the east coast, where wind resource is abundant.
To put it bluntly, we have to change the networks if we want to change energy and we are only just starting to understand how we meet this challenge. But Central Networks was the UK's first electricity distributor to switch on an innovative system designed to connect the country's growing number of wind farms without the need for expensive new overhead power lines.
That's good for the wind generation companies because it means their projects are cheaper; good for Central Networks because it doesn't have to spend money upgrading the network; and good for everyone as we get more renewable energy at less cost.
Generation
Central Networks brings power to more than 10 million people across central England, from the densely populated city centres of Birmingham, Nottingham and Leicester to rural Gloucestershire and Lincolnshire. It is on the east coast where the company developed the Ofgem-backed Registered Power Zone (RPZ). Rather than spend £5 million on a new overhead line to cope with the extra wind generation, it spent a tenth of that developing the innovative technique to increase the capacity of the current dual circuit 132KV line between Skegness and Boston by more than 30 per cent.
To put it simply, power lines are designed on a fit-and-forget basis. The amount that the lines sag depends upon the power being transported, and therefore the conductor temperature. Their capacity is fixed using average summer and winter conditions to ensure that the required ground safety clearance is maintained. However, when it is particularly cold and windy, Central Networks could actually push more current down without the lines getting too hot. That's the beauty of it, the times when it's cold and windy is exactly when that wind power is generated. And the windier it is, the more the lines can carry.
The company's engineers are able to use real-time information on temperature, wind speed and power demand allowing them to exploit that latent capacity. This Dynamic Line Rating (DLR) technology uses three weather stations and four line temperature sensing "donuts" to precisely monitor the line's real-time capacity. Automated relays disconnect wind farms if load exceeds 95 per cent of actual capacity.
Information
Areva built the control systems relating to the RPZ, while Central Networks' own engineers wrote the algorithms for the control system. The company will be sharing this information because the more it is replicated, the more useful it is.
The RPZ alone could allow as much as 90MW of extra generation capacity on to the local network. The potential savings are of the magnitude ten to one. It costs around £5 million to construct a new overhead line and offer a full service. Under our new flexible offer, with some curtailment possible, the cost is around a tenth of that.
Of course, Central Networks has got to balance all this with its prime role of keeping its customers' lights on and keeping tight control of costs. The company is currently negotiating with the regulator Ofgem over its investment plans for 2010 to 2015. It is planning to spend up to more than £900 million across that period; on preparing for changes in demand, such as rising needs for cities and business or the growth in electric cars, as well as opening up new avenues for renewable energy sources.
Techniques
The system is a great example of the sort of techniques included in the 'smart' network management that will be needed if the UK is to increase its renewable, distributed and micro generation.
This isn't a magic formula for larger offshore schemes, but a step towards active real-time network management that in some situations, will allow more distributed generation to get connected in a shorter timescale.
John Crackett is the managing director of Central Networks, which is the electricity distribution company for the East and West Midlands. Part of E.ON, the company brings power to more than five million domestic and business customers with a network consisting of more than 133,000km of underground and overhead cables and via almost 94,000 substations.
Subcribe below for your
FREE newsletter.