Networking’s not just for data. Obviously the power grid is a network; not so obviously, it could benefit by having its generation facilities much more decentralized than they are. Moreover, the existence of this network makes distributed power generation practical even when the generators are very small – like household size.
Long time readers of Fractals of Change may remember that we were going put solar panels on our house in NJ to generate electricity. Never happened because there were some technical obstacles – too many gables – and then we moved. Now we’re looking at putting a wind turbine (first choice) or solar collectors (second choice) at a camp (“camp” is Vermontese for a seasonal place) we’re renovating on Lake Champlain. It’s windy there.
Vermont is not nearly as generous as NJ in credits and other subsidies for small-scale power generation. The payback for the project is still marginal at today’s energy prices; but, if you can afford or finance the capital cost, it’s not totally impractical either. It’s the fact that the house IS on the electric grid that makes this all work.
If you’re going to use wind or sun to power a house which is off the grid, you have to have a huge bank of expensive batteries to store electricity from the time the wind or sun want to make it to the time you want to use it. Even then, you either need a power-interruptible life style or a standby fossil-fuel powered generator. Storing electricity is unfortunately not very efficient.
But, when you’re on the electric grid, the grid becomes your battery. The impetus for all of this was the Public Utilities Regulatory Polices Act (PURPA) of 1978. It requires utilities to buy back power at avoided cost rates from certain small producers and from co-generation facilities. The state implementation of this in Vermont (and many other states) essentially says that, if you are generating power at home, you can sell that power back to your local utility at retail rates. When you’re generating more power than you’re using, your meter runs backwards. This is called net metering.
You don’t store any electricity at all. That’s what’s important. You store credits (money’s easy to store) when the wind blows and the suns shines, and you draw down those credits when you need to. The grid can deal with the variability in what you produce just as it deals with the variable demand we all put on it. No expensive batteries. Probably no onsite generator.
If you generate less than you use in a month, you pay for net power consumed. If you generate more power than you use, you get a credit which is applied to future months. In Vermont (unlike some other states) you can’t end up with the utility owing you money; on a rolling twelve month basis, unused credits revert. In other words, if you generate more power than you use in a year, you donate that excess electricity to the utility.
Forcing utilities to buy power back at retail rates is clearly a subsidy. Kilowatts must cost them less somewhere else or they’d be out of business. Someday this subsidy may go away. Vermont law allow utilities to refuse this power if 1% of their peak load came from net metering; but we’re nowhere near having to worry about this.
What are the public benefits of this subsidy which is actually a tax on other electric users who don’t generate their own power?
- Since only renewable sources are eligible, there may be a reduction in carbon dioxide emissions. However, much of Vermont’s power comes from Vermont Yankee (a nuclear plant) and from hydro sources in Quebec; neither of these emit any CO2. Peak power here is provided by burning fossil fuel so any peak load avoided is an atmospheric plus. Moreover, nuclear or hydro power Vermont doesn’t use may replace fossil fuel generated power elsewhere – we are on the national grid.
- To the extent that the electrical network includes many small generators who are geographically dispersed and, ideally, are relying on different kinds of generating power (sun, wind, cow manure), the network is less vulnerable to failures of or attacks on the huge centralized sources of most of our power. Long time before this has any practical effect, though.
- An interesting side effect of having to “donate” surplus power generated over the course of a year to the utility is that it gets you to think how to use MORE electricity. We are deliberately planning on electric hot water heat and spot electric space heating. Gas is currently used for both these applications at our camp because electricity is normally more expensive. The gas we don’t burn won’t produce any CO2.
Note that this all works because of networking. Life off the power grid is much more expensive and the power supply less reliable. Also the manufacture and disposal of the batteries required off grid has a significant environmental cost.
Distributing the load is a way to make the network better.
The next post in this series is on the value of long links in a network.
Series on decentralized networks begins here.