by Tom Evslin
Let’s really Build the electric grid Back Better. That means converting to direct current.
There’s no argument that our electric grid needs to be rebuilt. Some of it, like the transmission lines that sparked the California fires, is dangerously past its use by date. Much of it, like the lines radiating out from the site of the former Vermont Yankee nuclear plant, are in the wrong place. The design is centralized as a relic of the days before advanced electronics and communications made decentralization a more resilient and cheaper option. Almost all of it carries alternating current (AC) as result of an argument Nicholas Tesla won over Thomas Edison a century ago. Most important, the grid is not ready for the loads we will put on it as we continue to electrify. It is also not reliable enough to be the sole source of energy for transportation and heating.
Times have changed. All the electronics in our houses use direct (DC) and not alternating current; that’s why they are plugged into our AC outlets through the ubiquitous converter bricks. Almost all energy efficient appliances use direct drive motors and convert AC to DC internally. LED light bulbs are better with DC. Water heaters don’t care.
The illustration above is from a report by the American Council for an Energy-Efficient Economy (ACEEE) The report estimates that at least 10% of the energy coming into a house is lost in conversion from AC to DC. The number is much higher if a storage battery or an electric car is also being charged. The number gets higher each time a rechargeable tool replaces a gasoline-powered predecessor.
All solar panels generate direct current. All batteries are charged with direct current. But, if you have solar panels and battery backup today, the output from the solar panels is converted to AC by an expensive piece of equipment and at a significant energy loss; then, at the battery, the AC is converted back to the DC the battery needs by another expensive piece of equipment and more energy is squandered. These inefficient systems exist today because the transition from AC to DC had been unplanned; that’s no one’s fault.
But now we have a chance to build back better with the money already appropriated in the 1.2 trillion dollar bipartisan infrastructure bill.
Fortunately we have time. The last great stimulus bill in the Obama administration was a jobs bill. We had to put people to work right now right now even though we didn’t have constructive “shovel ready” jobs for them. Unemployment was very high. That was then and this is now. We have a shortage of people to do what we were doing before the pandemic. We can plan and design and then really build back better while we’re training the workforce we’ll need.
These are some of the rules we need:
- Any new transmission line and any line which is substantially rebuilt with the federal money must be DC. There will be a transitional cost of equipment to convert to AC where local sub-transmission or distribution is still AC. Think of these convertors as scaffolding for building back better. After all grids are DC, we won’t need them anymore.
- Any new distribution line any distribution which is substantially redone with the federal money must be DC. Again there is a transition cost to convert to AC at houses which still need that.
- Building codes should be amended (a local and state job) to permit and encourage DC and hybrid houses as in the diagram below (also from ACEEE).
Once the distribution system is switched to DC, the inverter at the entrance to the house is no longer needed.
- After a transition period no grant money or subsidy of any kind should go to equipment for converting from DC to AC as part of solar or wind turbine installations or from AC to DC for battery installations.
5.Give consideration to going underground for new and rebuilt parts of the grids for reliability reasons (and to prevent forest fires). There are less problems in burying DC lines than AC lines.
- Take advantage of the rebuilding of highways to bury electrical (and broadband) conduits as well as drainage.
America and Americans will have a huge advantage if we are the first major country to go all DC. Our energy costs will be lower as will emissions from generating electricity. Electricity will be more economical and reliable enough to replace much fossil fuel. The money’s already been appropriated. We can build back BETTER.