Power generators are trying a plethora of technical innovations to maximize energy efficiency and reduce greenhouse gas emissions as the planet's temperature continues to rise. Part and parcel of these efforts: improving power grids, where weak interconnections and line losses consume even more fuel and emit more CO₂. An inside look.

Power generation represents a little less than half of all CO₂ emissions (41%, to be precise), mainly because of fossil fuels’ dominant role, especially coal. This contribution is expected to increase to 44% by 2030 as electricity demand doubles¹. Supplementing progress on CO₂ emission reduction, engineers are actively working on programs to improve the energy supply chain downstream – the interconnections within and between transmission systems – where better power flow management and reductions in line losses offer major opportunities for productivity gains. Such gains will have the effect of reducing the amount of electricity to be produced upstream by eliminating its dissipation as useless heat in conductors, transformers and switchgear.

Eliminating bottlenecks

Electricity travels from one point to another following the path of least resistance. Energy flows are scattered as a result, generating operating losses proportional to wheeling distances. In turn, more primary energy must be burned in power plants, producing additional CO₂ emissions in the case of oil, gas or coal-fired plants. This is another reason why improving interconnections and transmission infrastructure has become a priority. The goals are to reduce losses, save fuel and lower CO₂ emissions by optimizing power flows, and to eliminate the notorious bottlenecks capable of turning minor mishaps into full-fledged blackouts causing stag gering financial and energy losses.

Power systems are already saturated

As demonstrated by the 2003 blackout in Italy and the November 2006 outage in Northern Germany, which affected almost 10% of the power supply in the western part of the continent, European grids participating in the UCTE² are vulnerable and their energy efficiency is patently lacking. Grid vulnerability and poor energy efficiency are in fact two sides of the same coin: each major grid disruption increases primary fuel consumption, thus raising costs and boosting greenhouse gas emissions. In the priority interconnection plan it submitted to the European Council and Parliament in January 2007, the European Commission indicated that, at its current levels of infrastructure spending, the EU would not be able to establish a true single market for electricity that would help achieve its CO₂ emission reduction goals. For instance, the EU would not be able to add the necessary power generation from renewable sources because it is too vulnerable to production fluctuations. Prices would remain high due to grid saturation and the continued operation of inefficient production capacity in each of the energy regions with insufficient interconnections. The risk of temporary supply interruptions will remain high if power systems continue to operate at their physical capacity limits year after year. Lack of coordination in communication procedures and a still incomplete European grid management system could amplify the consequences of any major disruption.

Rising use of decision support tools by grid operators

Under these circumstances, the most urgent decisions are obviously political ones, particularly as regards funding for grid upgrades. In the meantime, R&D programs offer promising prospects for improvement. First, information technologies are now providing a number of tools for real-time grid operations. These tools offer immediate operational support for decision-making under both normal and off-normal operating conditions, helping to maintain the stability and balance of flows. These include Wide Area Management Services (WAMS), which are improving coordination between operators using enhanced capacity chart visualization and third-party grid intelligence systems relying on next-generation data processing equipment. Other systems are energy trading tools, which match supply with demand and monitor changes in generating costs in real time. Still others involve the use of forecasting methods from the world of finance. Together, these tools will allow operators to coordinate emergency response and, more generally, to optimize overall grid efficiency.

Substantial savings from very high voltage

The development of power electronics and semi-conductors such as thyristors makes it possible, and often desirable, to implement very high voltage direct current systems (VHV-DC) wherever there is an advantage in doing so.

Today, the majority of European high voltage lines, such as those in France, carry triphase alternating current at 225 kV and 400 kV. This system is flexible and makes it easy to adapt the voltage upstream using transformers to meet the needs of final users. But this comes at a cost: the Joule effect produces significant line losses proportional to the wheeling distance. In addition, reactive power³ must be offset when electricity is transmitted as alternating current, impacting its energy efficiency. The footprint is also larger, as is the cost of infrastructure (three cables are required to transmit triphase current). Moreover, overhead lines are often a source of conflict with local residents and raise environmental issues. All in all, the cost/benefit ratio decreases as the distance increases.

In contrast, VHV direct current can carry up to 800 kV with very small line losses over distances of several thousands of kilometers, as in Brazil, India and China. For shorter distances, as in Europe, VHV would help eliminate bottlenecks at the border by creating “power line superhighways”, ensuring voltage stability while promoting exchanges between national grids. In practice, the preferred solution would be to replace weak links in the grids or those with sub-par performance with new VHV direct current infrastructure that could triple transmission capacity while sharply curtailing line losses and ensuring voltage stability. At identical footprint, and if only in the cross-border areas of the UCTE, benefits expected from power flow improvement include a 10% reduction in fossil fuel consumption, representing some 16 billion euros per year, and a reduction in annual CO₂ emissions equivalent to 100 million tons!

New technologies such as superconductivity may also contribute significant improvements eventually, albeit for limited applications. For now, VHV is clearly a mature solution capable of meeting two of our major challenges: maintaining interconnection stability in the European Union and reducing greenhouse gases in the power generation sector. A third challenge would be to invest in this type of infrastructure. But that’s for national governments to decide...

1. OECD-IEA, 2006, World Energy Outlook.

2. The Union for the Coordination of Transmission of Electricity (UCTE) was created in 1951 to promote grid interconnection in Western Europe. It was the first step towards economic integration in Europe, even before the European Coal and Steel Community (CECA).

3. Reactive power is needed to operate inductive equipment such as engines, transformers, fluorescent lamps and energy-saving light bulbs. It increases load on the grid and requires relay stations.