Electric Grid: The Most Important Infrastructure
The recent power outages due to weather events and forest fires are a warning shot across our bow. Grid operators have ferociously resisted putting the transmission grid underground for a long time. They fall back on the higher cost of putting power transmission lines underground, but underground transmission does not necessarily have to be more expensive than overhead transmission lines. This is especially true when one considers the externalities of overhead transmission such as weather and fire sensitivity, habitat disruption, and aesthetics.
There is an interesting possibility presented by the high real estate values in urban areas. If the existing transmission and distribution power lines are put underground, the real estate value of the right of ways can pay for the cost of putting the system underground.
This was discussed in our recent PES paper, Mesogrids for Regional Power Delivery and Reliability. We chose to model the San Francisco Bay area in that paper, but there are also many other urban areas with high enough real estate values to finance undergrounding of the distribution grid.
There are technologies that make underground transmission feasible, but those technologies have not been developed. Underground transmission always comes up when utilities want to build any new transmission line, and they hold fast to the idea that this is unfeasible, and perhaps they do not want to support research on lower-cost underground lines because it would undermine this argument.
Overhead transmission lines are so unpopular that it typically takes 15 years or more to build one because of opposition in the US or Europe. The cost of this delay is not being properly factored in when considering the possibility of moving transmission and distribution underground. We need to get over that delay in order to build the grid of the future, including continental-scale supergrids, which are needed to make renewable energy practical as the basis for our energy economy. And the only feasible way to overcome that opposition is to move the transmission system underground.
The many benefits of having a continental scale supergrid include making renewable energy practical as the basis for our energy economy while reducing the necessary energy storage and dispatchable generation to balance the load. A continental-scale supergrid is the most important technology for getting off our addiction to fossil fuels.
We are about to invest heavily in infrastructure in America. This is the moment to decide whether we continue to develop an obsolete grid or decide to go in a new direction that will still be useful for hundreds of years to come.
AC power won out over DC around 1895 because of the transformer which only works to change the voltage of AC power, and because it is much easier to have a circuit breaker for AC compared to DC electricity. As a result of that, our grid has evolved into an AC grid everywhere in the world.
Technology has advanced, and now it is feasible to have a continental scale high voltage grid based on DC power, and a DC continental-scale transmission grid can be put underground, unlike the AC grid.
We are now at that “oh shit the sky is falling” moment with global warming where out-of-the-box ideas like supergrids can finally gain traction. For this to ever be a reality in the United States or Europe, the supergrid must be based on underground transmission.
There are two viable technologies for moving a continental scale supergrid underground. The conventional alternative is a pipeline size steel conductor filled with the cheapest available metallic conductor, sodium. This type of device is called an elpipe. The other way is superconducting lines. Superconducting lines have a maximum practical voltage of around 130,000 volts (130 kV). If we build a DC supergrid at a higher voltage than that, we will need very expensive voltage conversion stations linking the supergrid to the regional power distribution grids which bring power to the substations for delivery. These huge investments will later be outmoded when superconducting transmission becomes preferred.
In order to avoid many billions of dollars of future expenses due to replacing stranded assets, it is crucial to get the supergrid right.
It is feasible to operate both the DC supergrid for continental-scale transmission and regional DC mesogrids for power delivery from the supergrid to the substations at a single DC voltage that will also be compatible with future superconductive transmission. Making that decision now will save a great deal of money in the long run.
Changing the electric grid over to a form compatible with renewable energy requires getting standardization and a shared vision on the future of the grid right now. This will help us greatly in the future.
If we keep investing in the grid the way we are, we will be wasting a great deal of money in the long run. It is time to get our very best minds together from the National Labs and NASA to address this problem before we make a huge mistake. It would be a terrible mistake to defer this decision to utilities, regulators, and commercial entities.
