New transmission lines?

Unless electricity is generated on-site, from solar, wind, biogas or small hydro, and is then used on-site, some kind of transport is needed – either of fuel (coal, gas, LNG, diesel, biomass, nuclear fuel), or of waste products (fly-ash, spent nuclear fuel), or of the electricity itself.

Some forms of power generation (large hydro, geothermal) have little flexibility in their siting because of the nature of the resource. Coal power is more fexible – industry and power generation have to some extent grown up around coal resources, but more often the coal itself is transported by ship, rail or truck. Natural gas has to be piped – sometimes vast distances across continents. Increasingly it is pressurized and then shipped in containers in liquid form as LNG. Nuclear fuel and waste need especially secure transport. All theseforms of transport and processing add to the cost of those fuels, and to the amount of carbon emitted in getting their energy from the ground and to the electric plug.

Wind power can be developed in a very wide range of locations, and at many scales – from one or two turbines to hundreds. Optimizing the siting can make a big difference to the power output from a wind turbine, and this is greatly magnifed over a turbine's operating lifetime of 20+ years. However, as pointed out earlier in this book, up to now the rate of deployment of wind power by country has largely been dependent on political issues rather than resource criteria. In Germany, for instance, a favourable political climate has led to the large-scale deployment of wind power, while its wind resource (especially in the centre and south of the country) is lower than in some other European countries with much less installed capacity.

So while wind power can work effectively in many locations, it is true that some regions have an excellent resource that is located away from the towns and cities needing power (in fact, truly windy locations have historically been avoided as places to live). This might be true on a small scale (western texas has excellent wind, but its cities are further east and south) or a larger one (Xinjiang's excellent wind is many miles from China's eastern seaboard cities). And then there is the case of connecting large-scale offshore wind with electricity users. Connecting those resources to the locations where power is needed does require new lines – just as new lines would be needed for large hydro, or pipelines for gas.

A further factor to bear in mind is that the power lines built decades ago in some parts of the world badly need upgrading to cope with the demands and size of today's power sector, so investment in grid upgrades is needed in any case. The IEA estimates that by 2030, over 1.8 trillion USD will have to be invested in transmission and distribution networks in the OECD alone2. In some parts of the world – such as europe – grid upgrades are also a prerequisite for the operation of the market without conficting with legislation allowing competition.

Yet with all this talk of power grids and centralized generation, it is worth noting that a high-voltage grid is not always the answer. In many parts of both the developed and developing world, the cost of building transmission lines to reach every part of the countries is simply prohibitive. there are thousands of communities that the grid may never reach. Occasionally high-voltage lines even pass overhead, busily on their way from a large hydro plant to a big city – but there are no substations and distribution networks to deliver usable power to the people who live beneath. Here wind power, sometimes in combination with other renewables, can work on a smaller scale, off-grid, or on so-called mini-grids that serve a pocket of need.

The right quality of power

Another aspect to bear in mind is that the performance of, and output from, wind turbines harmonizes with the grid's requirements and does not create any disturbances to the system. This is ensured by means of so-called 'grid codes' that lay down the parameters within which wind turbines must operate.

Grid codes cover the technical aspects relating to the operation and use of a country's electricity transmission system. They also lay down rules that define the ways in which generating stations connecting to the system must operate in order to maintain grid stability.

Technical requirements within grid codes vary from system to system, but the typical requirements for generators normally concern tolerance (i.e. minimum and maximum voltage and frequency limits), control of active and reactive power, protective devices and power quality. Specific requirements for wind power generation are changing as penetration increases and as wind power is starting to function more like other large power plants.

Earlier generations of wind turbines were unable to respond if there was a fault on the network, and could even aggravate the situation. Today, however, modern wind turbines contribute substantially to the stability of the grid. Te majority of turbines being installed today are capable of meeting the most severe grid code requirements, with advanced features including fault-ride-through capability. this enables them to assist in keeping the power system stable when disruptions occur. Modern wind farms are wind energy power plants that can be actively controlled and provide grid support services.

ANNEX

2 International Energy Agency, World Energy Outlook 2008.