The U.S. needs a DC 'super-grid' to boost renewables and reduce pollution

power lines security
CC BY-SA 2.0 Oran Viriyincy

We could reduce CO2 emissions by 75% by 2030

The United States is a single country, but it doesn't have a single power grid. There are multiple regional grids that are not that well interconnected, making it very hard to transfer energy from one side to the other, especially over long distances since the lines are mostly alternating current (AC), which isn't very efficient over large distances. On top of this, the AC cycles on the different grids are not synched, making it even harder to send power across...

This is becoming a problem for the rise of renewable energy. Wind and solar power are intermittent sources, as is hydro, to a lesser extent. The best way to dampen that variability is to be able to share power across a very large area, sending energy from regions where there is a surplus to regions where there is a deficit, balancing things out.

Renewable Energy Policy Network wind and solar charts for 2013Renewable Energy Policy Network/Screen capture

As the grid is today, this is very hard. For example, if Texas was to keep building many gigawatts of wind and solar capacity over the coming decades, it might not be able to send surpluses elsewhere because its power grid is mostly independent from neighbor states.

So what can we do? It turns out that there's a way to make the grid more welcoming to renewable energy and efficient long-distance transfers of power without rebuilding the major parts of the existing grid, which would be ridiculously long and expensive.

A recent study looked at what would happen if we built a direct current (DC) 'super-grid' on top of the existing grid, with 32 nodes all over the country. DC is more efficient over long-distances, and also removes the synching problems when you transfer power from two different AC grids.

Renewable Energy Policy Network wind and solar charts for 2013Renewable Energy Policy Network/Screen capture

To see the impact of this DC 'super-grid', the authors of the study ran very detailed computer models to 2030, running various scenarios to see how they would impact energy prices and carbon emissions.

The authors examined four different scenarios. One included coal having a substantial role in the future grid. This kept prices low ($.0854 per kiloWatt-hour) but boosted carbon emissions by 37 percent compared to 1990 US emissions, when grid prices were typically $0.1176/kWhr. The rest eliminated coal and varied renewable and natural gas prices. With high-cost renewable energy/low-cost gas, carbon emissions dropped by 33 percent, while the cost was similar to having coal present at $.0857/kWhr.

For cheap renewables/expensive gas, renewables were used more heavily, and carbon emissions dropped by 75 percent. Prices were higher, at $0.1004/kWhr, but that was still cheaper than 1990 and below the projected cost in 2030. Having moderate prices for both gas and renewables resulted in a similar price ($0.1021/kWhr), while emissions dropped by more than 60 percent. (source)

All of those models make a few conservative assumptions. They assume that there are no significant changes in technology for renewables, and they include the cost of creating the DC super-grid.

The cheap renewable scenario is the most interesting, because it's also the most likely to happen since renewable will become much cheaper over time. Oil and gas are cheap right now, but they've always been cyclical commodities going up and down by large amounts. Renewables are different: Prices have been doing down rapidly for decades, and they are not likely to go up again. The sun and wind will always be free, and solar panels and wind turbines will keep getting more efficient and cheaper through economies of scale. For example, here's the price of solar power over the past decades:

Price of solar power graph© BNEF

So let's get working on this 'super-grid' as fast as possible!

Via Nature Climate Change, Ars Technica

Tags: Energy | Renewable Energy | Smart grid


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