War of the Currents: Round 2
The War of the Currents was fairly fought over 100 years ago and the winner was the undisputed better technology; a technology that has served us well. Electricity has worked its way into every facet of our lives and into almost every corner of the country. To be off-the-grid practically means to be Amish or The Unabomber. It’s so critical that when we had an extended power outage here in Seattle in 2006 eight people died of Carbon Monoxide poisoning. So what has changed to make we want to take up arms and fight for the discredited Direct Current?
The first is the increasing complexity of the grid. When most power was produced near where it was consumed the grid was stable and AC fit the bill. But since electricity deregulation an increasing amount of power is produced by Independent Power Producers far from the load they are serving. Sometimes these are distant coal plants near the mine rather than the load (it is easier to move electricity through a wire than coal down a train track) and sometimes it’s a wind farm (most people don’t live near where it’s windy). Large amounts of power rolling from one part of the grid to another makes the delicate balancing act that is required to keep the grid stable much more difficult. This instability can lead to small problems becoming big problems (see 2003 Blackout).
The second reason for re-fighting the War of Currents is that we can now change the voltage of DC currents. Though this has been true for a century, the technology is now good enough to support a High-Voltage DC (HVDC) network across the country. This technology is more expensive, less efficient and less reliable than the ubiquitous AC transformer, but it is now good enough that for long-distance, high-power applications HVDC’s other advantages can be appreciated.
And what are those advantages:
- Higher transmission efficiency (about 3% loss over 1000 km, about 30% less than with AC). Over short distances the lower efficiency of the voltage conversion dominates and AC is preferred.
- Ability to carry more power over a given amount of wire, reducing the costs and impacts of towers and wires.
- Ability to connect power sources (e.g. wind in South Dakota) with power demands (e.g. New York City) that are in asynchronous grids (remember from part 1 about synchronizing grids).
- Much better underwater, possibly allowing some power lines to be built without any towers or NIMBYs.
- Superconductors only work with DC power, so the meta-grid could use superconductors or copper.
My vision is that we split the Western and Eastern grids each into 4 smaller, easier to manage grids to increase reliability. These 9 smaller grids (leaving Texas as is) would only be connected by a national HVDC grid. At least initially, each AC grid would have one interconnection to the HVDC meta-grid that would allow it to sell power to anyone in the lower 48. Eventually multiple stations would be preferred to increase reliability.
For instance, during spring runoff utilities in the Northwest have huge amounts of power that they can’t sell. We could use the existing AC network to get that power to our Meta Grid Hub where it would be converted to HVDC. From there it could be transmitted to another part of the country where it was needed.
Using roads as a metaphor, this is Eisenhower’s federal interstate freeway system. It connects cities, but is not designed to get around cities. There is no need for a new, high tech meter in your home or for your refrigerator to talk to the utility (that’s the city road system). Nothing at your home changes and only the power traders at your utility do anything differently. They will have one more place to sell power (the Meta-Grid) and one more place to buy power (the Meta-Grid). How those transactions work would be complicated (does the Meta-Grid buy and sell power, or only allow those transactions to happen between utilities and provide transmission), but the details aren’t critical to the concept and would only affect a few people inside the utility.
Since most of our renewable resources are in remote areas of the western half of the country (e.g. wind in North Dakota or solar in the Southwest) it is difficult to imagine without this type of grid the eastern half of the country being powered primarily by renewables. No single project is big enough to withstand the challenges of building transmission, and even if it did transmission linking a single source (e.g. a large wind farm in Kansas) to a single demand (e.g. Chicago) is not viable. What happens when the wind doesn’t blow or Chicago doesn’t need the power? The more sources you connect the higher the odds that one of them will be active. The more sinks you connect to the higher the odds that one of them will need your power.
This is not a new idea at all. I haven’t heard anyone else talk about breaking up the large AC grids, but the rest of what I’m talking about here is well within reach of current technology and thinking. It’s only a matter of political will and money. When someone says that we can’t get off fossil fuels without a huge scientific breakthrough, that just isn’t true. Sure more efficient and reliable AC-HVDC conversion or room-temperature superconducting wires 1000 km long at less than $1000 a mile would be useful. Inexpensive energy storage would improved things greatly (I might write an entire posting on energy storage). But there’s no need to let the perfect be the enemy of the good, especially since the perfect tends to be 20 years into the future and always will be.