The Virtual Power Plant on an All-Renewable Grid
By George Harvey
When I was young, a telephone had no dial on it. When you picked up the phone, you heard a female voice say, “Number, please.” There was no Caller ID, a long-distance call meant contacting a long-distance operator, and a call to Europe could cost $20, half a week’s pay for some people, for just the first three minutes.
In those days, designing a power plant included getting estimates of what the greatest demand would be, and building the plant to cover that and a little more. Since the generating plants had huge boilers, it took days to get them up and running after a shutdown. And so they ran all night at full power, when no one wanted power, just to be able to cover the peak demand of the following day, when factories operated and people went about their daytime lives.
Wholesale prices were mostly a simple matter of demand, because the supply was nearly constant. During the day, the spot price of power was high, because that was when power demand was high. During the night, the spot price went low, because demand was low.
It is important that the power in low demand periods be used, because an overload can cause troubles with equipment, but the low prices attracted industries willing to work at night to use the low-cost power. If the attraction was still not strong enough, the prices went down even further. They could become negative, so people were paid to use the power, because it was important for the generators stay on to be ready to make power for the daytime high-demand periods.
It was a simple system, intended to serve a simple world. Commuter trains were hauled into Chicago by steam locomotives designed in the 19th century. Type was set for daily papers by casting it in lead alloy. Television was a black-and-white novelty. Nearly all computers were analog, mechanical, or both; the very few electric digital computers were huge, were slow, and had memory that cost $1 per bit. And space vehicles, even unmanned satellites, only existed in fiction.
Today, some of the owners of the power plants that were designed in those days will tell any and all listeners that the old ways of designing power plants are still the only viable way to go. Coal is reliable, they say, but nuclear is the wave of the future. And they really are experts, which we can know from their many, many years of experience.
Because they are experts, many people believe them. They say renewable power will not cover all our needs, because the sun only shines a few hours a day, the wind does not always blow, and nearly all suitable valleys for hydro power are already dammed.
But today, we have a new kind of power plant some of the experts in old-style technologies find hard to imagine. It is called a “virtual power plant.” It operates without fuel, and it matches demand far better than coal or nuclear could ever hope to do.
At the heart of the virtual power plant, there is a computer, with special software. The computer takes data input from the grid and from the weather. It analyzes the current and expected future conditions, and sends signals to various power stations to turn on or off.
A number of different power types are employed for this. Solar power includes PV, which provides a lot of power during peak demand periods. Solar also includes thermal, with its ability to store power for evening production.
Wind is onshore or off. In either case, if there is more power than demand, it can be shut off.
Hydro may include dams, but it also includes pumped storage, which stores power from times of excess power for later use as demand develops. Hydro also includes different kinds of run-of-river turbines and ocean power, which have no need for dams and little impact on the environment.
Bio-fuels include gas from bio-digesters; gas from wood gasification and similar systems; liquids from waste, such as biodiesel; liquids from oils and fats not used by the food industries; liquid fuels processed from cellulose; liquids fermented form starches and sugars; pellets from wood; agricultural waste, such as nut shells, corn stalks, and so on.
In addition we have a hope of getting power from the earth as geothermal, though the science on this is not entirely complete.
On top of this, there are ways to synthesize fuels from water, carbon dioxide, or other molecules. And there are numerous ways to store energy physically or chemically, including flywheels, compressed air, and standard batteries.
The virtual power plant can adjust supply from these as needed by choosing what should be given the highest priority. Facilities that can store power can be shut off while those that only produce power can make it. Then, when the sun is down and the wind is still, it is possible to tap the reserves of stored power.
The virtual power plant can also tell smart devices to turn on or off. For example, if we have a freezer, we can have it start its compressor at 5º in times of low demand, or at 10º in times of high demand, thus leveling demand. An electric car can be used to make this go further, because the virtual plant can tell the car to charge when demand is low, not charge when demand is high, and actually return power from its batteries to the grid when demand is highest.
The old paradigm for power generation is really a rather clunky product of a 19th century mind, when you think about it. It is a tried-and-true system that matches the steam locomotive and the Linotype casting machine. The fact that it was not updated when nuclear power came along is partly because nuclear power is just a higher-tech continuation of the lower-tech approach. That approach is, “Heat lots of water in big boiler to make lots of money for a big business.”
The newer paradigm is being used, and it works. The grid does not get less stable because of solar power, but rather more stable. In some places, planned power transmission lines have been cancelled because the distributed nature of solar power made them unnecessary for maintaining full power at peak demand periods. Wind power can have a similar effect.
We hear in the news that the utilities are having trouble with wind power because it puts power on the grid all night, at no expense to the operator, and that can make power generated by older facilities have negative value. They are having trouble with solar power because it puts power on the grid when demand is highest, depressing the peak prices. For these reasons, they say the grid is being made unstable by renewable generating facilities.
This is what we hear from power companies, but we should read between the lines. What they are really talking about, but using their words to disguise the truth, is that coal and nuclear are outdated and cannot compete with the newer, renewable paradigm.
Studies from organizations that have no particular interest in outcomes tell us quite a lot about this. The University of Delaware and Delaware Technical Community College teamed up to investigate the potentials for renewable power. They gave a detailed evaluation to what would happen if the US tried to go to 100% renewable power sources. They concluded that if the electric supply was properly designed and managed, we could have 100% renewable power reliably 99.9% of the time. This means that we would need assistance from non-renewable sources about 8 hours per year. (Their report is Cost-minimized combinations of wind power, solar power and electrochemical storage, powering the grid up to 99.9% of the time.)
The same study also concluded that the cost of power from 100% renewable supplies would be comparable to today’s power. And, it could be achievable by the year 2030. One interesting aspect of the study is that it did not include a virtual power station in the grid design. Perhaps if they had, they could have done better than needing help 8 hours per year.