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Bringing Arizona solar to East Coast evenings: Increasing connections in the power grid

Mark A. Gabriel's picture
President and CEO United Power Rural Electric Cooperative

Mark A. Gabriel is the President and CEO of United Power in Brighton, Colorado, a position he assumed in March 2021.  United Power is one of Colorado's largest rural electric power cooperative...

  • Member since 2021
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  • May 5, 2021

This item is part of the Grid Modernization - May 2021 SPECIAL ISSUE, click here for more

For the past 20 years the idea of unifying the eastern and western grids to take advantage of different generation resources, weather and times zones has been floated as one solution to supporting the nation’s energy needs. The narrative usually involves building a “transmission superhighway,” often described as multiple ultra-high-voltage, direct-current lines stretching coast to coast. Others have suggested possibly linking the two grids, which, as demonstrated the last time this occurred between 1967 and 1975, creates an unstable connection point that may continue to separate the interconnections.

Neither may be feasible—or necessary—to realize the vision of better power flows between the three distinct grids in the U.S. Instead of trying to construct billions of dollars’ worth of transmission, the potential exists to upgrade and uprate the seven direct-current intertie converter stations that currently bridge the interconnections as well as some of the surrounding transmission lines and other equipment.

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Today, these seven interties in the U.S.—there is an eighth in Canada—can transfer 1,320 megawatts of energy across the interconnections. Recognizing that the majority of the interties were developed in the 1980s and the facilities are, in some cases, in need of refurbishment, the interties already include existing rights-of-way and transmission connections, both of which are extremely valuable

Expanding the interties’ capability, even with a simple doubling,  would increase the bi-directional transfer capacity to 2,640 megawatts—about the equivalent of the seven large mainstem federal hydroelectric dams along the Missouri River, six 600-MW natural gas plants or 66 20-MW battery storage systems. And, the technical feasibility is significantly greater.


The case for converter stations

These interties are the most cost-effective way of bridging the interconnections. Access to power from the adjacent grids allows utilities to delay construction of powerplants needed to meet peak power demands. The stations allow the interconnections to exchange energy in a manner that supports both system flexibility and economic performance.

As evidenced in California in mid-August and early September 2020, moving generation to the right place at the right time requires critical operations to occur and power to flow across a system. Price does not become the determining factor; generation and transmission capacity does. At 7 p.m. PT Aug. 14, 2020, energy prices in California spiked to $1,410 MW-hour, and everyone was scrambling to supply as much energy as possible into the grid to limit rolling blackouts. It also was hot across the West, pushing the entire system to the very edge. Across the interties in the Southwest Power Pool market, prices were $35 with about 12,500 MW of available capacity. Had California and the rest of the West been able to tap into SPP’s energy supply to a greater degree than they did, the situation that evening would have been quite different.

Operating a system requires diversity in supply, whether it be diversity of renewables, hydropower, natural gas, coal or nuclear. The broader the physical connections the better in terms of time zones, weather conditions and resources.


Moving forward

As with all infrastructure, the open questions are, “who gains and who pays?” Historically, the interties have been funded by individual entities like the Western Area Power Administration and its customers. WAPA has four interties connected to its system, owning and operating two of them. As there is a broader benefit to utilities and reliability, it will be critical to determine the right funding and cost recovery mechanism.

Energy markets could provide the financial incentive to refurbish and modernize the interties. The SPP Western Energy Imbalance Services and the CAISO’s Western EIM may be interested in optimizing market-to-market transactions as both expand in the West. Such opportunities can provide justification to invest in greater intertie capacity. Paying for the interties could be handled by establishing single “zones” to capture costs and benefits. Additionally, the ties could qualify for financing through a loan with WAPA’s Transmission Infrastructure Program.

It is important to recognize that while improving the interties will be a quicker fix than building the new transmission superhighway, it is not without complications. In addition to the interties themselves, surrounding infrastructure will need to be bolstered, new lines may need to be constructed and the modeling of the system will have to be managed. System operators will also have to figure out the paths east and west to and from the interties.

Despite those challenges, the seven interties offer an opportunity to strengthen the U.S. electric system in a reasonable amount of time at a fraction of the cost of constructing new transmission facilities and would offer a respite from the immediate pressures of closing power plants. This can be done at the same time as planning a longer term, more robust solution and represents a no-regrets strategy.

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Matt Chester's picture
Matt Chester on May 5, 2021

Thanks for your insights on this, Mark-- such a hot topic right now, especially with some new funding coming down from the federal government to harden, advance, and modernize the grid.

If you want to hear more from Mark about the future of the grid, stay tuned for an upcoming episode of the Energy Central Power Perspectives Podcast

Mark Silverstone's picture
Mark Silverstone on May 13, 2021

Thanks for bringing this topic closer to my level of understanding.

Expanding the interties’ capability, even with a simple doubling,  would increase the bi-directional transfer capacity to 2,640 megawatts—about the equivalent of the seven large mainstem federal hydroelectric dams along the Missouri River, six 600-MW natural gas plants or 66 20-MW battery storage systems. And, the technical feasibility is significantly greater.

I guess one question related to what is possible, is "What is needed?"  For example, what would 30 gigawatts of offshore east coast wind mean, in practice, for the West coast, given the interties´doubling, as described above?

Mark A. Gabriel's picture
Mark A. Gabriel on May 13, 2021

I used the simple concept of doubling--although I actually believe moving each to 1,000 MW of transfer capacity is more logical--to make it a reasonable, time capable and achievable investment. "Field of Dreams" construction is always difficult in this business so rather than hoping to do something the long term such as waiting for 30 GW of wind, the practical opportunity now is to expand for what is needed now. During Winter Storm Uri the price of power was $600 a MWH on the east side of the system with shortages; in the west it was $20 a MWH with plenty of supply. We need to move now...this could be done in 18 months.

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