On the Street to Elevated Transmission: Excessive-Voltage Direct Present

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How Excessive-Voltage Direct Present Strains May Higher Join Photo voltaic and Wind to the Present Grid

Evaluating the Routes: HVAC Versus HVDC

It’s a query on the minds of grid planners all through america: How can we faucet into the nation’s greatest renewable sources on the lowest price?

That aim is on the horizon, nevertheless it might take rethinking the best way our energy transmission programs are constructed. So, let’s discover constructing HVDC traces.

At the moment, there are solely 5 HVDC transmission traces in america, the oldest of which was accomplished in 1970. Traditionally, DC transmission was extra cost-prohibitive and technically complicated than HVAC traces, notably for shorter traces of lower than a number of hundred miles. However current developments have made HVDC traces extra reasonably priced and useful to the grid.

HVDC traces work essentially in a different way than HVAC traces. Direct present electrical energy runs frequently in a single route, like the ability that flows out of your automotive’s battery to your automotive’s electrical programs. With alternating present, the circulate of electrical energy switches forwards and backwards dozens of occasions per second.

HVDC traces are bodily completely different from HVAC traces in a number of methods, the obvious distinction being the variety of wires every makes use of. HVAC traces sometimes use three conductors, whereas HVDC transmission solely requires two conductors.

Fewer wires wanted to conduct electrical energy means the towers that help them are additionally narrower than their HVAC counterparts. That signifies that proper of approach necessities for HVDC traces are additionally decrease than HVAC traces that carry the identical quantity of energy.

Discovering the Path of Least Resistance

There are a number of advantages that might make HVDC transmission traces extra interesting for a future grid that entails greater quantities of wind and photo voltaic vitality.

First, the circulate of DC electrical energy might be managed way more simply than our present AC system as a result of the converter stations which can be wanted to put in DC traces on the grid inherently have the flexibility to regulate how a lot electrical energy the DC traces carry.

Second, HVDC traces can carry greater voltages on cables of comparable measurement to HVAC traces, which means the traces warmth up much less and lose much less vitality to warmth. Much less vitality misplaced means extra energy might be transmitted additional.

Funded by the U.S. Division of Power and in partnership with the Pacific Northwest Nationwide Laboratory, the Nationwide Renewable Power Laboratory (NREL) is performing the Nationwide Transmission Planning Examine to analyze the alternative ways grid planners can deliver energy from areas wealthy with renewable vitality sources to the nation’s main load facilities.

In long-distance situations, comparable to can be the case with potential interregional renewable vitality zones (IREZ) that might deliver low-cost clear vitality to main load facilities from the nation’s greatest renewable-energy-rich areas, vitality losses on HVDC traces could possibly be lowered by as a lot as 50% when in comparison with comparable HVAC traces.

“Whereas there aren’t that many long-distance HVDC traces which have been contemplated traditionally, there are an honest variety of proposals for DC traces now,” mentioned Paul Denholm, a senior analysis fellow at NREL. “It’s only a matter of the bigger problem of finding out, siting, and allowing them transferring ahead.”

Trying Down the Street at HVDC’s Potential

Most HVDC traces are “level to level,” which means they solely connect with the grid on the very starting and finish of the traces. NREL is researching how multiterminal HVDC traces could possibly be utilized in the way forward for grid planning. These might increase the chances for transmission by creating the flexibility to faucet into an excellent longer line at a number of factors with out ending the road at these factors.

“It’s sort of like constructing a superhighway with an specific lane,” Denholm mentioned. “One of many questions that we’ve is knowing the trade-offs with the price of constructing combos of point-to-point HVDC, multiterminal HVDC, and HVAC traces. We’re solely simply beginning to get that detailed evaluation as a part of the Nationwide Transmission Planning Examine.”

Subscribe to NREL’s vitality evaluation emails to obtain updates, and be sure you watch NREL’s brief video summarizing 4 methods to extend transmission.