Connections between these grids have been limited because the grids aren't synchronized, so the AC power is out of phase. Special stations that convert AC power into DC power and then back into AC power in the correct phase are needed to move power from one grid to another.

Only a fraction of 1% of the electricity generated in the US can currently be transferred between the grids, and there is no direct connection between Texas and the Western grid.

The Tres Amigas station, which will connect all three grids together in one place for the first time, will initially more than double the ability to transfer power between them, providing 5GW of capacity. Eventually, the station is expected to transfer as much as 30GW of power.

The Tres Amigas SuperStation will act as a power market hub, enabling the buying and selling of electricity between the nation’s three Interconnections, which is not possible today.  Wind, solar, hydro and geothermal renewable energy sources that do not currently have access to transmission lines and/or customers will be able to tap into multiple markets through the Tres Amigas SuperStation. 

For example, regions rich in solar energy will be able to buy electricity at night, when the sun is not shining, from regions rich in wind energy.  As a merchant transmission system, Tres Amigas will charge a fee for usage of the power hub.

The Tres Amigas renewable energy market hub will be constructed in Clovis, New Mexico, a location that has easy access to all three of the nation’s power grids.   New Mexico’s State Land Office already has granted Tres Amigas, LLC the right to lease 14,400 acres (22.5 square miles) of land in Clovis for this system. 

An underground approach
Superconductor Electricity Pipelines combine conventional underground pipeline construction techniques with two highly complementary electric power technologies: DC superconductor power transmission cables and multi-terminal (voltage-source) AC/DC power converters. 

The result is a high-capacity electric transmission “pipeline” that is underground, easy to site and access, highly efficient and controllable, offers greater security and avoids complex cost allocation issues for interstate transmission of power than competing technologies.

(Below: These superconducting wires form the basis of power cables that carry far more power than conventional copper cables.)
Superconductor Electricity Pipelines combine conventional underground pipeline construction techniques with revolutionary, high capacity superconductor cables and proven multi-terminal DC-AC power electronic converters. The result is a high-capacity, long-haul electric transmission “pipeline” that:
 
 
• Delivers Gigawatts of green power to market: capable of carrying wind, solar, geothermal and hydro power from multiple sites to multiple cities.

• Resolves difficult siting problems: Conventional overhead transmission lines require new corridors hundreds of feet wide. The time-consuming and potentially litigious process involved to site these lines is a significant roadblock to developing new renewable power in the US. Superconductor Electricity Pipelines can carry thousands of megawatts of power in a 25ft wide corridor and  placed in existing railroad and highway rights of way.

• Improves Aesthetics: Conventional high voltage towers are more than 100ft  tall and can significantly impact the aesthetics of neighborhoods, national parks and sensitive wildlife areas. Superconductor Electricity Pipelines are out of sight and out of mind. Unlike overhead power lines, they also are free from electromagnetic fields.

• Increases Security: Ice storms, hurricanes, tornadoes and terrorism are just a few of the threats to overhead power lines. Given their underground location, Superconductor Electricity Pipelines are out of harm’s way.

• Enhances Efficiency: Superconductor Electricity Pipelines are able to cut power losses by two to three times when compared with conventional transmission options. This results in improved return-on-investment and reduced carbon emissions.

• Simplifies Cost Allocation: Cost sharing for new AC transmission lines is a significant challenge due to the difficulty in determining the benefit each affected electric utility receives. The power supplied to and delivered from Superconductor Electricity Pipeline DC-AC on- and off-ramps enables much simpler cost allocation.

• Cost Competitive: When looking at the thousand-mile, multi-gigawatt transmission runs required to transport renewable energy from America’s heartlands to its cities, Superconductor Electricity Pipelines are comparable in cost to 765kV AC overhead transmission lines.

Wonder what the Beauly to Denny line would cost with this approach?