This post presents a review and consideration of European transmission networks along with a more detailed examination of the issues present in the German, UK and French grids.
The networks considered, along with those throughout Europe, are facing two potentially conflicting forces; the economic downturn has seen a retraction in network investment heightened by the strong underlying prices for raw materials which has slammed up against the broadening needs of a diversifying generation mix. Thus, a network designed around large centralised generation assets is is being asked to deal with a broadening set of technologies with more erratic generation profiles. At present these are centered around Wind but increases in Solar and Hydro (along with micro-storage) will also figure large in the coming decades.
The European Network
Due to the ongoing financial crisis in many countries, the pricing of the cable has become a competitive parameter with electric utilities expecting the cable manufacturers to reduce the prices. Furthermore, due to the cancellation of transmission expansion plans and delays in the orders, the competition between companies installing the networks has increased.
High emphasis on the commercialisation of the renewable energy throughout the the continent is expected to drive the growth of the transmission and distribution cables. The renewable energy resources are often at far off from existing networks and often located in geographically tough places.
Many countries in Eastern European are integrating their regional grids together to form a nationwide grid with the development of the renewable energy further supporting the grid interconnection. In European countries, the work is going on to form a single European grid among all EU nations and in many countries the transmission networks are not reliable enough to transfer the electricity from growing number of power plants. The increased focus on the renewable energy, grid interconnections, economic development are expected to drive the demand for the transmission and distribution lines.
On March 31 1990, the electricity industry was restructured and then privatised under the terms of the Electricity Act 1989. The National Grid Company assumed ownership and control of the transmission system and joint ownership of the interconnectors with Scotland and France, together with the two pumped storage stations in North Wales, but these stations were subsequently sold off. In the UK, National Grid owns and operates the high-voltage transmission system in England and Wales, which consists of approximately 4,500 miles of overhead line, 410 miles of underground cable, and 341 substations.
In the North of Scotland, generation is assumed to significantly increase with onshore and offshore wind and marine renewables all contributing. The level of demand is not anticipated
to increase significantly over the next decade. Accordingly, there is a predominant net export of energy from the region to the Central Belt of Scotland. Additional power flows in the Central Belt of Scotland, within the Scottish Power Transmission (SPT) network, would place a severe strain on the 275kV elements of the network and, in particular, the north to south
and east to west power corridors. The circuits between Scotland and England are already operating at their maximum capability. It is hard to foresee any circumstances under which the transfers from Scotland to England do not increase significantly. Reinforcements identified to relieve the boundary restrictions across these circuits result in power transfers on the Upper North network of the England and Wales transmission system exceeding network capability. South of the Upper North boundary the increased power flows south from Scotland and North West of England progressively diminish as they are offset by the closure and displacement of existing conventional generation along the way. Accordingly, while there are transmission overloads in northern England the effects are greatly muted as the flows travel towards the Midlands.
Offshore wind generation connecting in England and Wales, together with the potential connection of new nuclear power stations raises a number of regional connection issues; particularly in North Wales, South West England and along the English East Coast between the Humber and East Anglia. The anticipated increased power transfers across the North to Midlands boundary and/or the increased generation off the East Coast and/or Thames Estuary would also result in severe overloading of the northern transmission circuits securing London.
The traditional methods of enhancing system capacity, particularly those which involve new overhead line routes, can be difficult to achieve due to planning constraints and environmental concerns.
London is the largest demand centre in the UK and a large proportion of electricity generated nationally flows into the city from the adjacent regions. Regionally the only significant generation is focused in the lower Thames Estuary where there are large coal, oil and gas-fired stations generation support is provided by units further away, such as the nuclear power stations to the East of London. Demand can also be met through the existing interconnectors to France and the Netherlands. Consequently, the demand in London is predominantly met by transmission connections from remote generation sources. The area is particularly sensitive to changes from the existing interconnectors to Europe. The commissioning of the Belgium-England interconnector (NEMO) coupled with the existing interconnectors to mainland Europe could potentially swing flows from 5GW import to 5GW export depending upon market conditions and generation/demand balance in the UK and Europe.
Thanks partly to the forecast rise in net generation, growth of which exceeds that of the underlying demand trend, the French power supply surplus is likely to increase as new largely nuclear capacity kicks in. A gradual decline in the percentage of transmission and distribution losses from around 6.63% in 2011 will help strengthen the market. The theoretical net export capability is expected to grow from 48.85 in 2011 to 55.58TWh in 2021.
In France, there is one transmission system operator – Réseau de Transport d’Électricité (RTE). There is also a major distribution system operator – EdF Réseau Distribution – accounting for 95% of electricity distribution, and around 160 local distribution companies. There are some 280,000km of transmission lines in continental France. In an effort to increase electricity interconnection capacity, France and Spain will set up a joint electricity grid company. According to a declaration signed at the 20th Franco-Spanish summit in Paris under the auspices of the then-French president Nicholas Sarkozy and Spanish Prime Minister José Luis Zapatero (who, since November 2011’s general elections, is no longer in power), the two countries will build a common, high-speed voltage power grid across the Pyrenees. RTE and Spanish Red Eléctrica de España, will each hold 50% of the JV, called Inelfe. The companies submitted a route proposal in 2008. Given that Spain imports 80% of its energy needs the JV will, most likely, leave additional export markets for French suppliers. In December 2011, Spain’s Red Eléctrica announced that German-built equipment for building the 8.5km tunnel that will connect France and Spain began work in Spain in Q1-12. Groupe Eurotunnel, the concession holder of the Channel Tunnel, is to build an electricity interconnector. The company is partnering with STAR Capital Partners in a 49:51 JV. The project, named the ElecLink, includes a twin 500MW direct current cable linking Sellindge in Kent, UK and Coquelles in France. The project is estimated to cost EUR250mn and will be supported by the European Investment Fund. The line is expected to become operational in 2013.
The German electricity grid is designed to connect the conventional power stations (and particularly large coal-fired and nuclear power plants) with high demand areas. The geographic concentration of wind energy development in northern Germany, due particularly to the offshore wind parks planned for the North and Baltic Seas, results in huge variations in the power flow. In the dena Grid Study model calculations were carried out to determine where bottlenecks can be expected in the grid.
The extension of the electricity grid will also affect the geographic distribution of any new conventional power stations. As wind energy dominates the transmission capacities in northern Germany in periods of strong winds, these are only available to a minor degree for the transmission of electricity from other power stations at such times. This must be taken into account when planning new, fossil-fuelled power stations in new locations in northern Germany and in the replacement of nuclear power stations which are being closed down in the North.
The cost of adapting the electricity grid to the increased amount of wind energy being fed into the system by 2015 amounts to a total of EUR1.1bn. Investments in the renewal and extension of the distribution networks are, however, not only necessary for the integration of renewable energies into the system, but also under the scope of technical modernization, the improvement of East-West transmission and the growing electricity trading within the European electricity market. Integrated planning is therefore necessary where upcoming investment in the distribution networks is concerned. Moreover, political backing (for example in the guise of an acceleration law) could provide considerable support to the extension of the grid within the target period.
The recently published Dena Grid Study (2011) suggested how the high-voltage grid needs to be expanded and optimised to the period 2020-25, assuming 39% of German electricity generation will by then be sourced from renewables and taking into account increasing electricity trading within Europe.
The least expensive option to this involves new standard overhead cable routes, which would raise the network-use charge within household electricity bills by just EUR0.002/kWh, from EUR0.058/kWh to EUR0.06/kWh. The most expensive option, involving high temperature cable, would raise the network charge by EUR0.005/kWh.
Transmission system operator Tennet is sceptical about the high-temperature cable scenario – even though the requirement for new routes would drop to 1,700 kilometres. “To implement this idea, the existing high-voltage network would have to be taken out of operation within the next five years. This is not compatible with maintaining a secure electricity supply” reports Tennet
Finally, to accommodate the growing amount of renewable energy coming online between now and 2050, there have been proposals for an offshore grid in the Northern, Irish and Baltic seas, as well as improved connections between Spain and France, and Germany and its neighbours.