Electrical Transmission Lines (Direct Current, Alternating Current, Renewable Energy)
Image Credit: BFS Man (CC-BY, flickr)

John D. Rockefeller had a growing problem on his hands. His strategic investments in petroleum refinement had given him a near monopoly over that industry; 90% of the market bore his name. Yet, he quickly found a limit to the growth of his business in the cost of transporting crude by rail. In an attempt to lower his transportation costs, Rockefeller tried consolidating the various railroad companies of the time under his banner. Upset with the oil baron’s monopolistic moves, the railroads banded together and refused to transport Rockefeller’s oil all together. With their retaliation, the railroad companies had effectively cut off access to the large markets of the eastern seaboard. Faced with this rail blockade, Rockefeller made a move that was audacious at the time: he opened an interstate pipeline. At the time, pipelines were risky and unproven. When Rockefeller made his move around the railroads, pipelines had already been used for more than 30 years. Still, no one had come close to attempting the extent and length that the oil barren was proposing. Ultimately, Rockefeller successfully built his pipeline, broke the railroad blockade, and revolutionized how the world would transport both crude and refined oil.

Today, one hundred years have passed since Rockefeller laid his pipeline and the future of our energy economy is moving away from fossil fuels. We have seen the rise of electricity, nuclear power, surging natural gas, and a revolution in renewable energy since Rockefeller’s pipeline. Renewables in particular seem destined to become the norm in our energy mix given the forces of economics, policy, and public opinion. That’s not to say the path to a renewable future is free and clear; we still face a number of technologic hurdles; not the least of which in the arena of energy transportation.

Fossil fuels are elegant in one way. When you need to move them, you can simply load the solid, liquid, or gas into a pipeline, truck, or ship. You can physically move the potential energy to where it can sit indefinitely until you eventually consume it to do work. Renewable energy sources like wind and solar lack this simplicity in transport and storage. You can’t change where the wind is consistent and where the solar radiation is high. The resource itself can’t be moved and we are struggling to move the energy it produces the long distances to people that need it. If there aren’t a lot of people around to use up the energy carried by sunlight and wind currents, it will largely go un-captured. Effectively, we haven’t built interstate pipelines for electricity.

That’s not to say that we couldn’t build a super long electrical line from the resource to the people. There are, however, some peculiar properties of electricity that dampen the effectiveness of our most familiar option. The vast majority of the United States’ electricity is transmitted in Alternating Current which isn’t very good at moving power over long distances; say from hydroelectric plants in Washington state to consumers in LA. Or from wind farms in the sparsely populated Oklahoma panhandle to consumers in Chattanooga, Tennessee.

From an electrical engineer’s stand point, you just can’t build an AC line that far. You would lose too much energy as it made its trip, making the whole ordeal economically pointless. The ways in which these losses occur are numerous and complex. For example, the AC electricity format has an odd consequence called the “skin effect” that limits how large a wire can be. Larger wires can theoretically carry more current, but AC electricity tends to only flow through the outer most parts of the wire. A larger wire in this case wouldn’t be able to economically move more current. When you add “derelict losses” and “corona discharge” to the picture, the outlook isn’t good for AC transmission longer than 600 miles or so.

That limitation of Alternating Current, plus the ever increasing need to move renewable energy long distances, is driving a surprising resurgence in Direct Current. High Voltage Direct Current (HVDC) to be precise. With its ability to scale up better that AC and a lower susceptibility to losses, HVDC lines make it possible to build “pipelines” for our renewable energy. It’s a solution we have actually used in a limited capacity since the 1970s. The Pacific HVDC Intertie (humorously nick-named the “Western Donut”) has been used since May of 1970 to transfer bulk amounts of hydroelectric power down the Pacific Coast.  

Currently, there are a few proposals for a grand expansion of HVDC. One of the most dramatic suggests a national “grid overlay” of continental scale on top of our existing AC transition system. This “supergrid” would provide a feasible way for clean energy to be moved en masse from where it can be produced to places where energy demand is high. With the “supergrid,” all of that solar radiation falling on the sparsely populated desert southwest could be harnessed and economically moved up to the eastern and western seaboards, for instance, before being transferred onto our existing distribution systems.

While the idea might sound incredible, the thought behind the “supergrid” is very similar to the logic of oil and gas pipelines that we use daily: it’s an economical way to move the bulk resource from where it is collected to where it can be processed and distributed further. We already have experience building systems on these types of scales. For example, consider that the existing sections of the Keystone pipeline snake almost 3,000 miles to send crude oil from Canada down to Texas and Louisiana for refinement. It’s only 2,300 miles from Death Valley to New York City. If we can move the crude oil fueling our climate crisis that far, then it’s well within our ability to move carbon free energy at least the same distance.

When the original baron of oil was faced with an affordability crisis in transportation, he innovated on the pipeline. Even before Rockefeller’s pipeline, coal mine owners innovated on James Watt’s steam engine by placing it on rails to haul coal more efficiently; caravans of horse drawn wagons had become prohibitively expensive. We face a similar problem today; one fueled by a lack of efficient transportation for our electrons. As the cost per unit of electricity from wind and solar continues to fall, the economic pressure to solve this transport problem will only rise. The renewable energy potential is out there to power our nation. We just need a modern day Rockefeller to innovatively move it to market.

 

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