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Utilities Battle Homeowners Over Solar Power
HughPickens.com writes Diane Cardwell reports in the NYT that many utilities are trying desperately to stem the rise of solar power, either by reducing incentives, adding steep fees or effectively pushing home solar companies out of the market. The economic threat has electric companies on edge. Over all, demand for electricity is softening while home solar is rapidly spreading across the country. There are now about 600,000 installed systems, and the number is expected to reach 3.3 million by 2020, according to the Solar Energy Industries Association. In Hawaii, the current battle began in 2013, when Hawaiian Electric started barring installations of residential solar systems in certain areas. It was an abrupt move — a panicked one, critics say — made after the utility became alarmed by the technical and financial challenges of all those homes suddenly making their own electricity. "Hawaii is a postcard from the future," says Adam Browning, executive director of Vote Solar, a policy and advocacy group based in California.
But utilities say that solar-generated electricity flowing out of houses and into a power grid designed to carry it in the other direction has caused unanticipated voltage fluctuations that can overload circuits, burn lines and lead to brownouts or blackouts. "At every different moment, we have to make sure that the amount of power we generate is equal to the amount of energy being used, and if we don't keep that balance things go unstable," says Colton Ching, vice president for energy delivery at Hawaiian Electric, pointing to the illuminated graphs and diagrams tracking energy production from wind and solar farms, as well as coal-fueled generators in the utility's main control room. But the rooftop systems are "essentially invisible to us," says Ching, "because they sit behind a customer's meter and we don't have a means to directly measure them." The utility wants to cut roughly in half the amount it pays customers for solar electricity they send back to the grid. "Hawaii's case is not isolated," says Massoud Amin. "When we push year-on-year 30 to 40 percent growth in this market, with the number of installations doubling, quickly — every two years or so — there's going to be problems."
But utilities say that solar-generated electricity flowing out of houses and into a power grid designed to carry it in the other direction has caused unanticipated voltage fluctuations that can overload circuits, burn lines and lead to brownouts or blackouts. "At every different moment, we have to make sure that the amount of power we generate is equal to the amount of energy being used, and if we don't keep that balance things go unstable," says Colton Ching, vice president for energy delivery at Hawaiian Electric, pointing to the illuminated graphs and diagrams tracking energy production from wind and solar farms, as well as coal-fueled generators in the utility's main control room. But the rooftop systems are "essentially invisible to us," says Ching, "because they sit behind a customer's meter and we don't have a means to directly measure them." The utility wants to cut roughly in half the amount it pays customers for solar electricity they send back to the grid. "Hawaii's case is not isolated," says Massoud Amin. "When we push year-on-year 30 to 40 percent growth in this market, with the number of installations doubling, quickly — every two years or so — there's going to be problems."
There's a couple of issues. But I'm not a power systems engineer, so chime in if you are one.
If the control systems make the assumption that power will always be net positive--all work will be going in always and any fluctuations will still be overwhelmed by the amount of current indraw--then those meters, and the control station could have problems.
Think of it this way. Your power supply has a current source limit. It rarely publishes the current SINK limit. So if you plugged your 12-volt supply into your 5-volt supply (to get 12-5=7 volts) the 12-volt line would be sourcing, but instead of common, the 5-volt line would be sinking. The sink limit for a typical power supply voltage rail is MUCH smaller. You can have a 5 A rail that can only take a few milliamps of INPUT current. The key thing here is, power supplys typically have a direction.
For a more IT analogy, think about cable service. Cable comes from head end, hits distribution nodes, and then more nodes, and then finally the end node and to your house. Each one of those makes an assumption that you're not going to broadcast cable (not internet, but TV) from your house.
Second, end-node measurement. Power meters don't have to be designed to measure current both ways. That's an assumption made during manufacture. If you bought one of those nifty Kill-A-Watt meters and then ran current backwards, it would likely either not register it, OR register it still going forward. That's a serious problem for a power company. They can see reduced load using their existing system, they cannot see negative loads.
It's possible I'm wrong and they're great future thinkers or need negative power measurement as part of some sort of power systems. But I've not heard of it, so a Power Sys engineer chime in.
Moving along, let's be honest: Just because someone makes something does not mean it's compatible with the grid. You don't run one-off kernel drivers made by your neighbors. If someone hacks together some random garage equipment (and not some government certified power controller box) and plugs it into the grid, that grid is now touching everyone else's house nearby. Imagine water coming into your house, and all a sudden some guy in your neighborhood is pumping his well water back into your system. Would you want to drink that? Now clearly the stakes are a little less dangerous with electricity, but that guy can still muck up the line. He can add tons of noise to it, he can raise or lower the voltage level until the system can react--and if his changes faster than the system can react, it's not going away. I wonder if it's even possible that someone could use a system like that to "game" the correction system into swinging harder and damaging your components.
More on compatibility, it's not just current and voltage. There's power factor. There's noise. There's the shape of the power wave to begin with. (Also called noise.) Someone dumping square waves at the right voltage and current into your power line is going to cause problems. It's kind of like someone buying an Arduino and bit-blasting ethernet frames into a hub (Layer 1). Everyone shares those physical lines and if that Arduino doesn't do it exactly right, everyone's got problems.
The point with all of this scribble is that power grids are very specific and allowing anyone to plug in and generate power is like allowing anyone of your neighbors to share your water. If they're not careful, or don't even care, to match the requirements of the system, they can easily wreck havoc with it and you.
I am not even remotely saying it should be illegal to generate power. What I am saying is it should be very clear what the requirements of the grid are, and that anyone who violates those requirements should be fined, and repeat offenders kicked off the grid. I also think generators/controllers should be certified to work with the grid if they're not already.