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Invisible, Underground HVDC Power Costs No More Than Ugly Towers

Clean, renewable power is running into transportation problems. To deliver renewable power from remote areas to where the people need it, we need to add a lot of transmission capacity to the grid. If we follow our traditional practice of building ugly towers all over the landscape and stringing wires from them, we will spend years fighting environmentalists only to ruin the landscape we love.

The U.S. power industry is very slow to change. In 1954 Sweden began using High Voltage DC (HVDC) power transmission instead of the AC system, which was created in 1885 by Nikola Tesla. DC systems used to be much more expensive because expensive electronic voltage converters had to be used in place of simple transformers. However, semiconductor costs are falling while transformer, land and steel costs skyrocket. As a result, underground HVDC power transmission is rapidly becoming cheaper than ugly AC towers. By following existing road and rail rights of way, very quick turnaround times are possible and court battles are avoided.


Credit:ABB Ltd., Zurich, Switzerland

AC power transmission requires 3 cables instead of two and has additional losses due to skin effect and capacity to the ground. DC voltage converters are very efficient with less than 1% loss. They also handle faults much better as they can respond in an instant. They are already used to tie together our regional AC grids.

Most regulated utilities have little incentive to cut costs as they are given a percentage as their profit. Los Angeles is one exception. The LA Department of Water and Power serves the ratepayers, not shareholders. LADWP built one of the few long HVDC links in the U.S. in 1986. It brings 1600 megawatts (MW) of power from Utah to Los Angeles. The link is now being upgraded to 2400 MW and will soon be extended to the wind farms in Wyoming.

Wyoming wind is very valuable in Los Angeles because wind peaks in the evening, hours after electrical demand peaks in the afternoon. The two-hour shift in sun position between Los Angeles and Wyoming causes wind output to almost perfectly match electrical demand. HVDC power links pay for themselves quickly because the spot price of electricity varies by as much as 3:1 through the day and can be mismatched by as much as 33:1 between unconnected areas.

Wind power that has no place to go can actually have a negative value, as it must be disposed of. Solar power in the north requires links to southern deserts, preferably further West as solar output peaks about four hours before demand peaks. North-South links between populated areas also smooth annual demand variation: In the north, demand peaks in Winter while the south needs more in summer for air conditioning.

HVDC links should be built to link rich renewable resources to distant population centers. Solar thermal plants in the Sahara desert and the hydroelectric resources of Scandinavia could power all of Europe. The current system of importing energy through pipelines, trains and tanker ships should be replaced by clean, efficient HVDC power links. An excellent movie on the subject by GENI is called "There is no energy crisis; there is a crisis of ignorance" 

HVDC connection losses are only about 3% per 1000 km plus 1.5% for two voltage converters. This is much more efficient than conventional transportation. In fact HVDC can be often be justified because it is cheaper than building a pipeline to bring in gas to run power plants. Electric motor efficiencies are typically above 90% while fossil fuel engines are usually under 30% so it is more economical to ship electricity than fuel. 80% of rail shipping in the U.S. is for transporting fuel.

The United States has been completely left behind in HVDC equipment development. Swedish, German, French and Japanese companies dominate the field and have built an extensive network of links. Many are across the waters surrounding the continent. The U.S. needs to play catch-up. We clearly need new laws that encourage grid development in the U.S. to accommodate our renewable energy.

Superconducting cables are even more promising but still too expensive. American and Japanese companies have already installed working superconducting links. With superconductors there is no loss in the cable but the wire must be kept cold with circulating liquid nitrogen. Newer superconductors under development can work at dry ice temperatures but much development is needed.

As with many of our energy problems, the technical solutions are the easy part but the regulatory environment is the real problem. Subsidy decisions made decades ago distort the market and encourage continuation of the inefficient fossil-based status quo. New laws could make it easier and more profitable to build HVDC links and greatly reduce the cost of renewable energy.

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Volume 18, Issue 4


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