A coal plant vs. a heat battery. Credit: Modified from TVA in Public Domaine (Wkipedia).
This is a “please-tell-me-why-I’m-wrong” diary. I’m always been stunned by the intelligence and high level of science-knowledge among Dkos diarists and commenters. Mark Sumner is kind of awesome at this kind of thing. So I would respect having your feedback.
Just about all DKos readers know that the biggest problem with renewable energy is power storage. Sun goes down, power goes off from solar panels. This prevents us from immediately decarbonizing our society. It is the best argument for maintaining the fossil fuel industry and it is a big, legitimate problem.
An induction-powered heat battery. Sounds complicated; it’s not.
I’ve read about this idea, exactly...nowhere. Why can’t decommissioned coal plants be turned into “batteries”, using the same simple technology (induction heating) that is used for kitchen cook tops? Replace the coal furnace unit (see the figure above) with a big-ass chunk of iron* (having internal water channels to make steam) and a magnetic induction coil that heats the iron block. It’s the same as switching from a coal fire to an induction stove top to heat your food.
When solar (or wind energy) is plentiful, excess electricity is stored as heat in the iron. It can get really hot. When the renewable energy drops to zero (nighttime or cloudy days), water is run through the iron block and turned to steam to run the generators already in place in the old coal plant, converting stored heat energy back into electricity. This is an induction-powered heat battery. As long as the iron chunk’s temperature exceeds 100 C, you can turn on your lights, heat your home, plug in your car, watch Netflix. Voilà!
Most of you know about induction cook tops and how they work. For the both that don’t, a high-frequency AC electromagnetic coil will generate electrical currents (eddy currents) in a nearby ferromagnetic material like iron, mainly in the electrically conductive metal “skin”, that are converted to heat by electrical resistance. You need to use a iron pan for an induction stove top. Better? Induction furnaces get hot enough to melt metals and they are used all of the time, so it can easily replace a coal-fired furnace. Iron has a high heat capacity and it is highly thermally conductive. A induction heater on one side of the iron block will heat that whole sucker up as high as you want and it will stay really hot for a long, long time if it is insulated.
Current solutions to intermittent renewable energy production mainly focus on huge Li-ion batteries (or Na-ion and even zinc batteries) for utility energy storage. These are expensive, potentially dangerous from the point of view of metal fires, and alkaline metal mining has big environmental and geopolitical costs. Not to mention a short half-life (when did you last have to get a new phone?).
Other ideas include hoisting enormous weights on stilts or down abandoned mines that can raised during power excess and slowly released to drive a mechanical generator (so-called gravity batteries). Similarly, water can be pumped uphill to dams during energy surplus and released to drive a turbine when needed. But this is 1) environmentally damaging and 2) requires new, expensive infrastructure and construction. Finally, research is on-going on reversible fuel-cells and green hydrogen that can be transported for burning to generate electricity. Maybe.
All of these are good ideas, but mine is better. Much better.
Induction heating is far more efficient than combustion, almost magically so: 70-85% efficiency compared to 30-40% for a natural gas stove top. It checks all of the boxes on efficiency, cost, safety and environmental safeguarding. We can immediately recycle the 290 decommissioned coal-fired power plants in the US with minimal outlay and allow the utility companies to recoup their sunken economic costs in a dead power plant. If it makes them money to go green, utility companies will be more excited about it than a russian soldier seeing a washing machine.
Advantages:
1. Cheap. After the Ukes win, rebuilding of Ukraine can start with chopping up and selling all the ruscist T-72 hulls to make solar powered metal heat battery blocks. When these are gone, we’ll move on to the battleships rusting in Suisun Bay. If a magnet sticks to it, it will work just fine.
2. It uses well-known, established and proven technology. Duh. No pie-in-the-sky. Essentially an induction furnace but it stores the heat energy and works at lower temperatures than a furnace. (Thermovoltaics seem promising but we need the technology now, not in a decade or two). This is important also since all the components of the induction heating industry (including parts and repairs) already exist and do not need to be built. Induction heating has been commercially used for over a century.
3. Repurposes environmentally disastrous coal and natural gas generators using the same water heating (steam generators) technology to generate AC current electricity. We are just changing the way we heat the water. Lithium mining is not good.
This would greatly accelerate the rate of conversion of fossil fuel power plants to renewable energy: Econ101. It would turn power companies from being the biggest obstacles to renewables to the biggest promoters. Why? Because they own all the aging power plants and they can still make a buck from them when they become batteries.
4. SCALABLE. This is huge (both literally and figuratively). To make more battery capacity, all you need to do is add more insulated metal block/electromagnets. Obviously, this comes with steam piping issues but all this is stone-cold simple. If you have multiple blocks, you can heat them up or draw them down automatically, all at once or one-at-a-time based on their temperatures. The heater is so cheap (essentially a coil of wire), you can make as many as needed. The control circuitry is simple.
5. The heat battery does not need to be directly attached to the solar photovoltaic (PV) or wind energy generator and so it can be distant from the power source. In fact, if a town has a small power plant (not uncommon), the battery could be on the opposite end of the power grid so electricity is first used by the community, then excess is stored in the battery, and the circuit is reversed when power is needed.
6. It uses the existing power grid (with minor modifications). Also huge. Remember, the coal plants were built to be the electrical generators.
7. Safety: Instantaneous shut-down when the power is turned off and then the block naturally cools. Also, it only heats up the power block (induction is so efficient because energy is only transferred into the metal not the surrounding environment). Unlike a coal furnace where the entire furnace and chimney heats up. I can put a butter dish next to a boiling pot when I cook. Very convenient for some sauces, such as scampi with garlic, white wine and butter.
Disadvantage: The magnetic currents decrease exponentially with depth so you probably would have to limit the size of each heating block. But again, since it is just a hunk of iron surrounded by copper wire, use more of them. You are just heating up blocks of metal for God’s sake. You don’t want molten iron so it cannot heat up too much (a thermocouple would be a good idea). It also requires a power inverter (induction heating requires AC current) but this isn’t rocket science. It is not inconceivable to shrink these metal heat batteries so that everyone with home solar PV panels can have hot water at night. At-home, microsteam-electrical generators is a bridge too far, however.
Kindly do me a favor and tell me why I’m wrong about this. I cannot find any indication that this idea is being pursued and it’s driving me nuts. Go ahead and tell me I’m stupid, I’ve got a thick skin. I would love to know why a induction electrical heat battery will not work. And then I’ll tell you about my other idea on to how to get rid of waste plastic by using it as a mesh “rebar” in asphalt to make roads last longer, with smaller potholes...
*BACOI: I haven’t trademarked this yet, but it is catchy, isn’t it? (BTW: I’ve got a number chores going on but I will try my best to promptly read and reply. Thank you for commenting.)
