Tres Amigas grid hub attracts more than renewables

* Grid superstation attracting variety of generators

* Initial hub expected to accommodate 3,000 to 5,000 MW

HOUSTON, April 14 (Reuters) - Tres Amigas, proposed as energy "hub" to allow new sources of wind and solar power to move from remote areas of the U.S. Southwest to power-hungry cities, is attracting interest from nuclear and fossil-fueled generators as well, said Tres Amigas Chief Executive Phil Harris on Wednesday.

To be built near Clovis, New Mexico, the Tres Amigas superstation will serve as a power hub, not only to only allow electricity to flow between the nation's three separate grids, but to improve the overall efficiency of the grid, Harris told attendees at the Gulf Coast Power Association conference in Houston.

Likened to a highway rotary, Tres Amigas will allow multiple power transmission lines from the three U.S. grids to feed power into and out of the superstation through multiple alternating- and direct-current converters connected by DC superconducting cables.

"It is time for the nation to be able to move power between the three separate grid," Harris said, citing other ambitious grid improvement programs in China and Europe.

He said he expects the station will be able to accommodate the transfer of 3,000 to 5,000 megawatts of power initially and to grow to 30,000 MW of transfer capacity over time.

After obtaining authority from federal regulators in March to sell transmission services at negotiated rates, Harris said Tres Amigas is negotiating a number of parties that may want to become "anchor" tenants in the project, five transmission companies interested in building high-voltage lines into the superstation and a number of companies that want to develop facilities to store electric power.

Harris said Tres Amigas has been contacted by developers interested in putting new nuclear, coal and natural gas-fired generation near the superstation which would give them the flexibility to sell power into the most attractive wholesale power market.

He expects the project to create the same kind of opportunity for generation and grid efficiency that he saw when overseeing the expansion of the PJM power market earlier in his career.

When PJM expanded to 15 states, Harris said participants expected power would flow from the lower-cost markets in the west to the higher-priced markets in the east. Within a few months, however, 20 percent of the power on the grid was moving from east to west as generators were able to take advantage of the geographic and weather differences across the larger system to increase their operating rates, Harris said.

"The transmission system is vastly underutilized," Harris said.

Tres Amigas is partly owned partly by American Superconductor (AMSC.O).

The U.S. bulk power network is divided into three grids: the eastern two-thirds of the country, the western states and Texas, with each grid operating on a different cycle. (Reporting by Eileen O'Grady; Editing by Marguerita Choy)