Delivering Green Energy Efficiently
As the UK moves towards renewable energy generation, the challenge is on to reduce losses from the transmission and distribution networks. Doug Gracias, Engineering Director of cable manufacturer Prysmian UK considers some of the issues involved.
In the UK we have come to regard the consistent and reliable delivery of electricity on demand as a given. Maintaining this situation, in the face of a rapid diversification in generation and increasing demand is a challenge. Add into the mix the ambition to increase the efficiency of the delivery network, and there really is a test for the engineers.
The government target of producing 15% of our energy requirements from renewable sources by 2020 will mean the electrification of heating, transport and industrial processes. These changes may increase the average electricity demand by between 30% and 60% - as much as double today’s electricity capacity could be needed to deal with peak demand.
To meet this demand with any degree of reliability requires three significant developments: the integration of a diverse range of generation sources into both the transmission and distribution networks, building a greater degree of connectivity with international generation and greatly increasing the sophistication by which the network and demand is managed.
Integrating Diverse Generation Sources
The most efficient way to transmit electricity is at very high voltage. DC is also more efficient than AC, so if you are looking to carry energy across large distances, the most efficient way to do so is to use a low-loss high-voltage direct-current (HVDC) transmission system.
Distance is a very topical issue as wind turbines are supplying nearly 12% of UK energy demand and, by their nature, wind farms do not tend to be situated conveniently close to areas of high energy consumption.
Offshore wind farms, such as the 160-turbine Gwynt y Môr project in North Wales (the second largest operating wind farm in the world) contribute a steadily rising percentage of power requirements. The challenge here lies in integrating this energy into the grid. High voltage submarine cables bring the electricity to shore, where it then needs to be stepped down to the 400kV used in the transmission network and accommodated into the grid.
International connectivity is widely regarded as a way of building flexible capacity that can be shared across Europe and, potentially, North Africa.
Existing interconnectors join the UK network with France, the Netherlands and Ireland and many more such projects are planned - the most ambitious plans looks to capitalise on the extensive renewable energy generation capacity of Norway and Denmark.
Looking to the future, both generation and demand will be highly variable with predictions of wind and solar power entirely reliant upon accurate weather forecasting and outputs uncertain. Relying on such intermittent generation in the energy network creates a balancing headache for the network managers.
In a system employing a diverse and disparate range of generators, ranging from rooftop PV panels to community ground source heat pumps or individual wind turbines the challenge is one of control - local balancing and system optimisation in order to maintain an orderly supply.
The way to manage this very dynamic environment is with better diagnostic information and smarter controls. Prysmian can already supply cables with integrated sensors that monitor the performance of the cable, alerting managers to a developing fault or area of underperformance.
We are also developing real time thermal rating systems, using fibre optic cable to measure the temperature of the conductor to give a very accurate picture of the loading at any given time. With this understanding comes the ability to control the distribution and optimise the efficiency of the distribution network.
As cable manufacturers we have a significant contribution to make, not only to support the distribution of electricity from diverse generation sources, but also to contribute to its better management and control.