The Tennessee Valley Authority (TVA), the largest public utility in the nation, signed power purchase agreements (PPA) to add 450 MW of wind power to its service territory by 2012 through a pair of projects in the Dakotas, roughly 1500 kilometres from TVA headquarters in Knoxville, Tennessee.
The power will be moved to TVA's wires by the Midwest Independent System Operator (Miso), which operates a large adjoining grid. "Their south-easternmost service area touches up against our north-western corner," says TVA spokesman Scott Brooks. "So it's a direct line from them to us."
Electron trade
The actual electrons generated by the Dakotas wind stations will not reach the Southeast: "The system works by displacement," says Miso transmission technical director Dale Osborn. "You add some electrons in the Dakotas and everything just gets nudged a little east and south. The equivalent amount that they schedule will come out the other end and go into the TVA system. It sounds like magic, but that's the way it works."
The sale of power between the regions is seen by some to resolve the issue that inadequate wind resources would prevent south-eastern utilities from complying with a national renewable energy quota.
"Utilities in the Southeast are already importing a lot of fuel," says Michael Goggin, transmission policy manager for the American Wind Energy Association. "Coal is coming from places like Wyoming or even overseas and a lot of their gas is imported from other states. So if they're already importing their fuels, it makes sense that you could just import the wind ... via transmission lines."
The proposed Ashley wind farm in North Dakota, developed by CPV Renewable Energy of Maryland, should provide 200 MW. Invenergy of Chicago is building the Hurricane Lake project in South Dakota, set to add 250 MW. Both new 20-year PPAs are the result of TVA's 2008 request for proposals that sought 2 GW and attracted more than 60 responses. "TVA has a goal driven by our board of directors that calls for more than 50% of our generation to come from non-carbon-emitting sources," says Brooks. "We're shooting for the next five to ten years to reach that goal."
The utility currently draws most of the power for its 32 GW system from coal. Its portfolio also includes 6.9 GW from nuclear power stations and another 4.3 GW from hydroelectricity.
Its non-hydro renewables capacity is about 50 MW. Around half of that is from wind. TVA built three 660 kW turbines on Tennessee's Buffalo Mountain in 2000 and signed a 20-year PPA when Invenergy added 27 MW at the same reclaimed strip mine in 2004. TVA has been slow to add more wind to its seven-state system, but expects to announce a small handful of additional contracts in coming months.
