from the sometimes-simple-solutions-are-the-simplest dept.
Heat batteries could help cut emissions by providing new routes to use solar and wind power:
A handful of startups think bricks that hold heat could be the key to bringing renewable energy to some of the world's biggest polluters.
Industries that make products ranging from steel to baby food require a lot of heat—most of which is currently generated by burning fossil fuels like natural gas. Heavy industry makes up about a quarter of worldwide emissions, and alternative power sources that produce fewer greenhouse gases (like wind and solar) can't consistently generate the heat that factories need to manufacture their wares.
Enter heat batteries. A growing number of companies are working to deploy systems that can capture heat generated by clean electricity and store it for later in stacks of bricks. Many of these systems use simple designs and commercially available materials, and they could be built quickly, anywhere they're needed. One demonstration in California started up earlier this year, and other test systems are following close behind. They're still in early stages, but heat storage systems have the potential to help wean industries off fossil fuels.
One key to heat batteries' potential success is their simplicity. "If you want to make it to giant scale, everybody ought to agree that it's boring and reliable," says John O'Donnell, CEO of California-based heat storage startup Rondo Energy
Many industrial processes run 24 hours a day, so they'll need constant heating. By carefully controlling the heat transfer, Rondo's system can charge quickly, taking advantage of short periods when electricity is cheap because renewable sources are available. The startup's heat batteries will probably require about four hours of charging to be able to provide heat constantly, day and night.
[...] In Rondo's system, electricity travels through a heating element, where it's transformed into heat. It's the same mechanism that a toaster uses, O'Donnell says—just a lot bigger and hotter. The heat then radiates through the stack of bricks, warming them up to temperatures that can reach over 1,500 °C (2,700 °F).
The insulated steel container housing the bricks can keep them hot for hours or even days. When it's time to use the trapped heat, fans blow air through the bricks. The air can reach temperatures of up to 1,000 °C (1,800 °F) as it travels through the gaps.
How the final heat then is used will depend on the commercial process, O'Donnell says, though many facilities will probably use it to turn water into high-pressure steam.
[...] Rondo isn't alone in its quest to deploy heat batteries in industry. Antora Energy, based in California, is also building heat storage systems, using carbon. "It's super simple—it's literally just solid blocks," says cofounder and COO Justin Briggs.
Instead of using a separate heating element (like Rondo's "toaster coil") to turn electricity into heat, Antora's system will use carbon blocks as a resistive heater, so they'll both generate and store heat. This could cut down on costs and complexity, Briggs explains. But the choice will also mean the system needs to be carefully enclosed, since graphite and other forms of carbon can degrade at high temperatures in the air.
[...] Even using commercially available materials, it'll take a while for heat storage to prove its role to manufacturers and make a meaningful dent in industrial emissions. But the technology could be one building block of a new, climate-friendly industrial sector. "We have all the tools we need to transform to a zero-carbon economy," O'Donnell says. Now it's time to build them.
(Score: 5, Informative) by Nuke on Thursday April 13, @08:27AM (1 child)
Brick-filled electric heaters were common in the UK in the 1960-1970 period. I expect there are still plenty around, although most were replaced when people installed gas or oil fired central heating (when even off-peak electricity prices went through the roof). They were called storage heaters, and were typically screwed to a wall. They accompanied electricity tariffs that provided cheaper electricity at night, and were part of the strategic move to nuclear generation at the time.
(Score: 1) by pTamok on Friday April 14, @08:30AM
And storage heaters were (and continue to be) awful.
They are warmed up overnight with electricity that costs less than during peak demand during the day. So the bricks are at their warmest first thing in the morning, losing heat throughout the day, until when you want the heat when you are home from work in the evening, they are at best, tepid, and stone (brick) cold at bedtime. If you happen to be at home during the day, it could be cosy - or insufferably hot. There's a reason why they were ripped out of many, if not most installations.
In theory, the storage heaters had louvres and fan systems, which together with insulation, was meant to minimise the heat-losses during the day, when they were not needed, and allow you to open them up and run a fan to cool the bricks (and warm the room) in the evening; but they patently did a lousy job. I know, as I've suffered them on more than one installation.
On the other hand, the BBC reported on an interesting Finnish approach: BBC: Climate change: 'Sand battery' could solve green energy's big problem [bbc.com] - instead of heating stuff up overnight to use the next day, they are talking about heating things up in the summer to use in the winter - a seasonal rather than a diurnal approach. The benefit is a large volume of whatever has a smaller surface area which is easier to control the heat losses from. The average energy density of the Sun is less than the middle of a compost heap [stackexchange.com], but because there is so much of it, the middle gets rather hot, and the heat conduction from the middle to the outside is remarkably slow [stackexchange.com]
(Score: 1, Interesting) by Anonymous Coward on Thursday April 13, @12:41PM (3 children)
Went and looked at the company link, on this page, https://rondo.com/how-it-works [rondo.com] , wait for it...
...
...
Yep,
Seems to me that a thermostat with some additional inputs (like electricity pricing) is all that's needed, but no, this system needs "AI".
(Score: 3, Insightful) by GloomMower on Thursday April 13, @12:46PM
I don't know that there is anything stopping anyone from calling a thermostat AI.
(Score: 2) by DeathMonkey on Thursday April 13, @04:11PM
Maybe the AI bit is for managing the incoming power? Dealing with voltage and current swings on your solar panels or wind turbines?
(Score: 2) by maxwell demon on Friday April 14, @07:18AM
To me, “automated AI patented controls” says that the automated controls were patented by an AI. Maybe only an AI would manage to patent a thermostat.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by GloomMower on Thursday April 13, @12:44PM (12 children)
How well does this scale? Is it something that utility companies would use? I'd figure if so, it would be in use by them already already since it is so difficult to start and stop other plants.
(Score: 1) by khallow on Thursday April 13, @01:15PM
Doubt they'd use it directly since heat is a poor way to store electricity. But they might for a customer who does need it.
(Score: 0) by Anonymous Coward on Thursday April 13, @01:21PM
Many types of thermal storage discussed here, https://en.wikipedia.org/wiki/Thermal_energy_storage [wikipedia.org] even a link to seasonal storage (charge in summer, heat the building in winter) at https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storage [wikipedia.org]
(Score: 5, Informative) by ElizabethGreene on Thursday April 13, @01:26PM (9 children)
I'm familiar with sand heat batteries, a related technology, and can answer for it.
The way these work is pretty straightforward. To "charge" the battery, electricity is dumped into a resistor coils in the middle of a big insulated container of sand|bricks. To discharge the battery, a fluid is pumped through a heat exchanger in the pile where it flashes to steam. That steam turns a turbine, driving a generator.
The complexity of maintaining the turbine and generator sets the smallest feasible size for them at large industry or small utility scale. As to how big they can get, the efficiency of storing heat*, turbines, and generation increases as they get larger. The limiting factor for largest possible size will be the available input power.
* - Specifically, the heat capacity of a sand battery scales with volume, the cube of length assuming it's a cube. The heat losses to convection, conduction, and radiation scale proportional to the square of its length. Technically heat loss would scales with the 4th power of temperature, but the assumption is the small ones and the big ones operate at the same temperature which makes that irrelevant. The upper bound for temperature is limited by the materials in your heat extraction loop.
It takes time to spin up a turbine, so they aren't good for load smoothing like Tesla's megapack. The use case for them is storing excess generation capacity of renewables and time shifting it to when there is power demand or for time shifting a predictable power load from expensive power to cheap power.
The best way to use something like this is to park it next to a solar or wind farm that has excess generation capacity during the day. Power grid operators tell farms like this to dump excess power at their generation peaks. Today that power gets dumped into resistive loads or arced off. Park a heat storage battery next to that facility and you gain the option of storing the power for hours or days until its needed instead of throwing it away.
I've made assumptions that they're using electricity for heat input here. It's also possible to heat the sand|bricks directly via e.g. solar concentrators, but then you have a hard materials handling problem of moving around materials at 1KC without losing too much heat or slagging your conveyors.
Sidebar:
If you live in a place with cheap power at night and expensive power during the day, you *might* benefit from a different type of thermal battery. If you have a large water heater, put a contactor on a timer on it to only power it when electricity is cheap. Modern water heaters are exceptionally well insulated and are great for load shifting *if you have sufficient storage capacity*.
(Score: 2) by DeathMonkey on Thursday April 13, @04:04PM
These batteries are supplying heat to industrial processes not converting it back into electricity so we don't need to worry about that last step involving the turbine.
(Score: 2) by RS3 on Thursday April 13, @04:43PM (6 children)
Wow, awesome post, you know your stuff.
Regarding turbines: I'm not a power system engineer nor steam / turbine, but AFAIK they keep the turbines running a constant speed and vary the generator's "field" coil current to vary the output. When little or no electric power is required, field current is low or off and there's very little energy spent- system basically freewheels. Of course you also have to vary the energy (heat) input accordingly.
For smaller scale systems, rather than using steam, would something like ammonia or another refrigerant provide a more efficient thermal cycle?
(Score: 2) by ElizabethGreene on Thursday April 13, @06:14PM (5 children)
I'm not an expert on the turbine working fluid bit. I thought you only needed different working fluids if you couldn't reject heat at "normal" temperatures. Is that wrong?
That's moot for this application; they aren't using turbines. Instead they are using the heat for industrial process heat. The big difference with this brick system is they aren't using a solid-to-liquid heat exchanger. They're pumping air through the hot bricks and running the hot air through an air-to-liquid heat exchanger to make steam. That cuts out a huge cost vs. by eliminating liquid lines. I've been thinking about that and think I can steal the idea for sand systems by injecting high pressure air into the bottom of the pile. That'll take a bit of experimentation and is now officially on my list. :)
(Score: 2) by RS3 on Thursday April 13, @07:32PM (2 children)
I'm a moderately thermo and mechanically adept EE, so I don't know the answer to your question about turbines, and actually I don't really understand the question due to my lack of knowledge. I just know the typical heat input makes steam, steam drives turbine, exhaust gets cooled to condense, water pumped back into boiler.
Yes, I understand. You mentioned turbines and spin-up time, so I was just commenting on that. :)
From what little I know, turbines are usually only efficient at larger scale, and/or with fairly large heat input, such as high pressure high temperature steam, or a gas turbine where the fire drives the turbine directly.
Again, from what little I know, steam systems aren't very efficient, and generally only useful at higher ΔT, but I really don't know for sure- I'm not trying to be an informer- more tossing out thoughts and brainstorming.
I don't work in thermo, but I like the idea of being able to generate useful electricity on a small-ish scale from lower ΔT. Water obviously needs a lot of heat to phase-change into steam, which is great at driving turbines, piston-engines, etc. My suggestion regarding ammonia or other highly volatile compounds like refrigerants was to use them instead of steam because they'll flash to heat-carrying vapor at much lower temperatures.
Obviously I have some interest, but like you, need to do some experimentation. Unfortunately most good refrigerants (heat-cycle efficient) compounds come with much danger, EPA restrictions (as they should), etc. Ether might be a good test compound but you would need to work outside, maybe under a large open pavilion or similar.
(Score: 3, Informative) by ElizabethGreene on Thursday April 13, @08:43PM (1 child)
Hank Hill would suggest energy-efficient clean-burning propane (R290) for all your heating, cooling, and cooking needs. I can confirm the small hardware store blue cylinder gas works as a refrigerant and is compatible with ester oil. It's cheap too. ;)
(Score: 2) by RS3 on Thursday April 13, @09:21PM
Yes, propane is awesome! It's great for shrimp on the barbie too!
Kidding aside, I recently bought a propane-powered generator.
And yes, I've read a bit about using propane in AC / refrigeration systems, but I don't know a lot about it (yet).
Another idea for the heat storage / electricity generation system: rather than a complete Carnot cycle [wikipedia.org], you could take the thermally spent but still hot propane, burn it to add to the heat cycle, that way all the heat is conserved- no need to cool and condense it. Did I just invent something, or is it obvious?
If we're aiming for no CO2 output, then forget that idea. Hoping for more CO2 capture happening in the future...
(Score: 2) by RS3 on Thursday April 13, @07:49PM (1 child)
PS: sorry, sometimes I forget to mention the main (obvious to me) point: your sand, brick, whatever thermal storage has to be pretty darn hot to make steam at pressure. At some point it'll cool and won't be able to make steam, therefore no electricity. But other volatile liquids will boil at much lower temperatures and it might be possible to use them to extract much more of the heat energy in your storage system.
For example, Titanic steam pressure was around 215 psi (~14.8 bar), which required 200°C.
Nuclear power plant:
(Score: 2, Interesting) by Anonymous Coward on Friday April 14, @01:29AM
Just as a point of reference, a friend restored a Stanley Steamer (car). The working boiler pressure is about 600 psi. https://tnmot.org/collection/stanley-steamer/ [tnmot.org]
(Score: 3, Interesting) by SomeRandomGeek on Thursday April 13, @05:30PM
This system appears to be an optimization of what the parent described.
That system was: Off Peak electricity is turned into stored heat, then stored heat is turned into peak electricity.
This system is: Off peak electricity is turned into stored heat, then stored heat is used for an industrial process like melting steel.
People have been asking for a while how to economically do industrial processes that require very high temperature with electricity, since, for generation heat, combustion is so much cheaper than any renewable process. The key insight seems to be that off peak electricity can be used to generate the heat then the heat can be stored until it is needed. And, depending on how you do the accounting, off-peak electricity is basically free.