First Quarter, 1991

POWER

Long-distance interties connect faraway areas

s utilities have become aware of the benefits that international power exchanges offer, the number of transmission interties between countries has increased. Taking the trend a step further, proposals are being considered to transmit power over very long distances, with interties that eventually could connect both hemispheres.

Traditionally, a utility generated all of the electricity that its customers needed. Customers typically received their electricity from the nearest generating plant, which often was not very far away. Indeed, the maximum economical transmission distance 30 years ago was only about 500 km. This method of operation was the norm for many years.

However, evolving technology has made transmission over longer distances possible without significant losses or threat of voltage collapse; escalating fuel costs have made it desirable. Power exchanges within a country first began to occur, and currently, power sales also take place across national borders. There are 50 nations that actively exchange power with one or more countries. Three regions have formed large interconnected power systems. Continental Western Europe has the Union for the Coordination of the Production and Transport of Electric Power (Ucpte). Eastern European countries have the Comecon interconnection, and Scandinavia has the Nordel system.

Such interties save money for all involved. The most efficient power generation usually comes from base load units. Often, excess base load capacity from one utility helps meet demand peaks of another one utility gains revenue for electricity from a unit that would be operating anyway, the other buys electricity at a lower cost than its own peaking units could generate it.

Magnified cost benefits

Some countries anticipate great economic benefit from long-distance transmission. To illustrate: Many developing countries-particularly in Africa and Latin America have vast untapped generating potential. If there were a means of transmitting this power, they could sell it to gain much-needed revenue. Developed countries without ample power reserves could buy this electricity economically. An added benefit is that much of the untapped generating capacity comes from clean renewable sources-such as hydroelectric and biomass.

A long-distance transfer scheme could benefit the environment as well Fuel is saved and emissions are cut when utilities level out their load curves. Also besides being relatively inefficient, some types of peak generating units burn fossil fuels. Relying more heavily on renewables can reduce pollution. Additional savings come from eliminating losses involved with starting and stopping units.

Technology is available

Another significant technological advance is the multi-terminal high-voltage dc line. Major ones include a five-terminal link between the northeastern US and Canada and an intertie that interconnects the separate power systems of Corsica, Sardinia and mainland Italy (see companion article). Similarly, thyristor technology - used to convert power between ac and dc - also has improved and become less expensive.

It is less clear how to establish the various control and communications systems necessary to regulate power flows, meter, and supply data to Scada and energy-management systems among multiple parties. Although a global communications grid has existed for several decades it would be complicated and costly to relay power system data to several utilities in several countries. In addition, since power system operators would need to confer when problems arise, even spoken language is a barrier. Many countries are addressing these communications issues internally so there should be solutions available by the time long-distance interties are ready for construction.

It also is significant that various types of energy storage--pumped water, compressed-air, battery, and magnetic-field are either being refined or made commercially viable. Some would argue that this area of technology could help utilities use power more effectively without the need for long-distance interties. Considering all of the available technology, companies and governments must evaluate each project on a case-by-case basis.

No matter how attractive the economics of long-distance international interties are, the political aspects of such projects remain a hurdle. Many wonder if countries can afford to become too dependent on buying power from other nations. While the emphasis in many nations is on becoming energy-independent, international interconnections mean a move toward interdependence. "The barriers to long-distance interties definitely are political and bureaucratic rather than technical." Says Peter Meisen, director of Global Energy Network Institute (GENI), San Diego, Calif, USA, a proponent of the development an international power network. "Countries have to decide whether this idea will complement their energy policies."

US/Soviet transmission link

Prevalent trends in the Soviet Union support the possibility of constructing the line. Besides opting for higher transmission voltages, approximately 95% of the country's generating capacity now is interconnected. Indeed, the USSR already is able to derive benefits from long-distance transmission because the country spans 11 time zones.

However, such a line would be very expensive. The cost of a UHV overhead line over relatively uncomplicated geography is about $US 620 000/km. The estimated cost for an underwater link under the Bering Strait is $5-billion. Nevertheless, estimates say that potential savings could make the project cost-effective.

GENI is promoting this intertie heavily because it feels that it will serve as an example to other countries. The organization foresees the development of a global energy grid that would have far-reaching world benefits. Several organizations within both the USSR and the US are considering the line seriously, with other interested groups from around the world also participating. The American Society of Mechanical Engineers, Manitoba HVDC Research Center, and the USSR Academy of Sciences, for example, all are conducting feasibility studies. Various other organizations are sponsoring meetings for concerned parties to discuss the issue. Again, politics and bureaucracy remain significant considerations; as relations between the two countries seesaw, it remains unclear whether the project will be pursued further.

None of the proposed long-distance interties have gone beyond the discussion phase. Besides the US/Soviet link, others being considered include ones between:

• Europe and Africa. The distance between the Morocco and Spain across the Strait of Gibraltar is relatively short. While there currently is no impetus for power exchange, there might be in the future. There is 34000 MW of undeveloped hydroelectric power in central Africa along the Congo River. Selling this power to western Europe would help provide Europe with clean power and provide needed income to African nations.

• Iceland and UK. Iceland's renewable geothermal and hydroelectric resources could provide economical power for the UK. The distance between the two countries is about 640km.

• North America and Europe. This link is the other way of connecting hemispheres but it certainly is the least practical. It represents very long underwater transmission distances and thus the most technical problems and cost. If the previously mentioned link between Iceland the UK is built, the line becomes more feasible because completing the link would only involve constructing a line from Canada across Greenland to Iceland.

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