'Sand Battery Could Solve Green Energy's Big Problem' (bbc.co.uk) 123
AmiMoJo writes: Finnish researchers have installed the world's first fully working 'sand battery' which can store green power for months at a time. The developers say this could solve the problem of year-round supply, a major issue for green energy. Using low-grade sand, the device is charged up with heat made from cheap electricity from solar or wind. The device has been installed in the Vatajankoski power plant which runs the district heating system for the area. Low-cost electricity warms the sand up to 500C by resistive heating (the same process that makes electric fires work). This generates hot air which is circulated in the sand by means of a heat exchanger. Sand is a very effective medium for storing heat and loses little over time. The developers say that their device could keep sand at 500C for several months. So when energy prices are higher, the battery discharges the hot air which warms water for the district heating system which is then pumped around homes, offices and even the local swimming pool.
Wake me when it's in mass production (Score:2, Insightful)
Slashdot is littered with stories about cool technologies that never leave the lab because there's no good way to produce them at scale. So, let me know when someone is actually mass producing these things.
Over here in Europe (Score:2)
We get the heat stored in the Sahara sand.
With the Sahara sand.
heat pump instead? (Score:1)
A resistive heating element is super inefficient. Why not use a heat pump instead?
Still wastes a lot of power, but less than a pure resistor.
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You're out of your chair. A resistive heating element does something you don't usually want to do; namely, it converts electrical energy, which is very useful and easy to convert, into heat, which is mostly undesirable and difficult to convert.
But it does it with vanishingly close to 100% efficiency. Converting electrical power to heat by resistive heating is literally the most efficient energy conversion I know of. The reason for this is simple: when
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Resistive heating is inefficient (compared to a heat pump) for making your house a few degrees hotter than outside your house. Its deficit versus a heat pump decreases as the temperature differential increases. Other limitations with heat pumps also start getting in the way.
There's a reason people use arc furnaces to make steel, and not heat pumps.
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They aren't trying to move heat around here. They are trying to store (at any efficiency) electrical energy itself. This is not geothermal they are using here.
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Resistive heating, and most other forms of heating, are ~100% efficient. Heat is the waste-pit of the universe, all energy ends up there in the end.
Heat pumps "cheat", and so have an effective efficiency that's typically around 300+% for residential uses. However, that efficiency falls rapidly as the temperature gradient increases, and the engineering challenges get more difficult. Just trying to heat a space to a pleasant 20C while it's -10C outside will typically drop the efficiency below 200% or less,
Re: heat pump instead? (Score:2)
Heat pumps produce low grade heat, which would require massive amounts of storage medium. Like say bedrock, but then you don't need sand.
Solving global warming with global warming (Score:2)
Just so weâ(TM)re clear, to help stop global warming they want to store mass amounts of energy generated by wind and solar in giant sand repositories at 500 degrees. This would seam extremely counter intuitive to the primary objective of stopping global warming. Fascinating.
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That heat would be generated regardless. The question is does that heat just get released into the atmosphere during the summer, or do you delay it's release until Winter?
If you release it in summer, then you need to extract more energy in the Winter to keep things warm, so you consume more energy resource and you also add more overall heat.
Carnot Efficiency (Score:2, Informative)
Like other posters have said, converting the electricity to heat is nearly 100% efficient. And with a temp of 500C, the carnot efficiency is (773K (hot) - 293K (cold)) / 773K = 62%. This is the maximum efficiency possible. Newer supercritical coal plants operate in this same temperature regime and are 40-45% efficient.
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Carnot efficiency isn't highly relevant here. They are describing the 'battery' store being used as a source for heat for heating needs. So it's not a general 'battery' in a good sense of the word, but it could offset heating-related energy consumption in cold weather.
If someone talks about using it as a general store for generating electricity though, it wouldn't be a promising strategy.
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Hypothetically, this may be a good way to cheaply store thermal energy for later release as a heat source, but not to drive a generator. This would be in conjunction with some potentially pricier solution for electrical energy storage, but the cost of the electrical storage would be mitigated for not having to cover as much heating load.
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That's not so clear to me. If you have need for a lot of heat (for district heating) then adding an electricity generator as well seems more or less zero cost. Turning the heat back into electricity might be inefficient, but what does efficiency matter when you are going to turn the concentrated heat back into low level household heating anyway.
The question is, do you need the electricity at the same time as the heating? If the answer is yet, then why not add a generator or thermovoltaic cell?
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Efficiency is less important when the energy is zero emission and excess that would otherwise be unused. The main concern is the size of the battery, but with stationary ones providing district heating that isn't much of an issue either.
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Like other posters have said, converting the electricity to heat is nearly 100% efficient.
Yeah, but converting the heat to electricity isn't. So while they're saving energy up front in construction as opposed to storing electrical energy in a battery, they're pissing heat energy away every time they generate the power to recharge. If the goal is to put heat into sand, then they'd have much more efficiency heating it more directly.
This is not a general solution. (Score:1)
Maybe this works for Finland but this is not a solution that will work generally. The problem is not getting enough sun. Solar power of any kind can produce only so much energy per area per year. We can calculate the energy consumption for a nation/region/whatever in the same terms of energy per area per year. People have done this and charted it out for us. http://www.inference.org.uk/su... [inference.org.uk]
I'll suspect someone looking at that graph might believe that with 5 watts per square meter (or whatever, it's in
Re: This is not a general solution. (Score:2)
Thin film PV with some foamed plastic to put it at an angle would consume little material by installed weight. PV designed for TeraWatt scale wouldn't look like PV designed to put on homes with large subsidies.
Molten salt storage (Score:2)
I am really lost on this one. Molten Salt Storage plants are already a very old and well tested technology.
Here's the 5 biggest.
https://greendiary.com/biggest... [greendiary.com]
Is the point of this to try and do the same with electricity during off peak hours? If so there's too many problems.
1. Solar production correlates well with solar power demand. The low demand times are late at night which just so happens to be when the sun is unavailable
2. Converting PV solar to transmission like power and then to heat is a lossy pr
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The obvious problem with molten salt is that it's expensive and dangerous (molten salts tend to be volatile and corrosive), and best coupled with solar-thermal power plants (which are themselves rather high maintenance)
In contrast, a big pile of sand with resistive heaters in it is about as cheap as you can get, and is compatible with any energy source. And while there are transmission losses, heating is always roughly 100% efficient (unless you "cheat" with heat pumps to do better - but that works best wi
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You want cheap as possible better than nothing?
Give people a big brick and a couple of solar reflectors. They can heat it during the day and stay warm at night.
Sorry this hot sand solution seems like little more than pointless feel goodismm, that does little but put money in connected pockets.
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Finland is up north. In winter, they measure the day length in minutes rather than hours. And during the day, the sun is low in the sky, so the light is low. Conversely, in summer they have 20+ hours of sun.
The website claims that their insulation is good enough for months. I would imagine day time variation is part of their aim, but weekly to seasonal variation seems the big win.
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District heating is common in the Nordic countries. We also have lots of off peak hydro power that could be used to heat this. I think the article focused too much on solar/wind, but I guess it's what the world has.
Sand (Score:2)
I can't wait to see the expression on MBS' [dailycaller.com] face.
Battery should store electricity (Score:2)
Going from anything, electricity, kinetic energy, anything to heat is 100% efficient, because that is the lowest grade of energy.
Getting heat to do work, that is very very problematic. Efficiency is abysmal.
Now they just need to miniaturize it... (Score:2)
Seems contradictory and expensive. (Score:2)
If sand "loses little heat", then it must have a low thermal conductivity, meaning it is difficult to heat and equally difficult to extract that heat. You can't have it both ways. The question would be if, at scale, you can actually heat the sand up fast enough to absorb the excess energy you need to store before the process becomes too inefficient or cost prohibitive compared to alternatives. Equipment costs (e.g., heat exchangers, compressors, blowers, duct, and valves) grow exponentially in cost with siz
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I guess they put pipes in it. If this is the case, the costs would grow linearly with size (twice the sand, twice as many pipes) rather than exponentially, while the other costs (the tank and insulation) would drop linearly to a first approximation.
Their big pitch here is for seasonal storage anyway. The sand does not need to be highly conductive, there is time for the heat to move around. The stats on their website support this. They are claiming a power of 100MW but up to 20GWh of storage. So that's 200 h
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More pipes requires more blowers, or bigger blowers. And the sand does need to be conductive. Time matters if you want to do anything useful. Ideally you want a single pass to generate a useful product stream. If the heat transfer rate is too low, you'll need multiple passes, which requires either more exchangers and a larger footprint (very expensive) or need a recycle loop that is much larger than the product stream and lose way more energy to piping friction losses (they are much larger per unit of flow
More "let's call it a battery!" bullshit (Score:2)
What is it with people trying to call pumped hydro a "water battery".
And thermal resistance storage a "sand battery".
Use the fucking proper terms.
Stop trying to sell bullshit.
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We don't have a word. "Thermal energy storage system" just does not trip of the tongue.
I think you should just get used to it. The meaning of the word "battery" is changing.
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And that's the point.
"The term Lamborghini is changing..."
img src="http://www.blahblahblah.com/yugo.jpg"
Variation on a theme (Score:2)
The more common format is to have a building with a heat pump, and use the ground under the building as a heat sink in the summer, and a heat source in the winter.
These generally use water to transport the heat, which limits the temperature difference you can achieve (extract too much heat, and you'll freeze the ground around the collection pipe), and you have to contend with groundwater as the heat storage area is not walled off.
This Finnish system will have more construction cost to build the sand tank, b
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I was wondering why they didn't use a two stage process - first heat the air with the more efficient heat pump up to its practical limits and then use resistivity heating for the rest of the temperature boost.
Although that would probably increase the capital and maintenance costs substantially so it might not be economically feasible.
In addition, the source of heat (air, ground, body of water) at scale could be an issue if the heat pumps were running a lot (basically freezing the ground and/or dropping the
Re:10% efficiency (Score:5, Informative)
And the efficiency for conversion from heat to electricity is always bad, like 45% maximum normally. The formula for maximum efficiency of conversion from heat to mechanical work is 1-(Tcold/Thot), temperatures in Kelvin.
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180C is apparently the hottest we've managed to run a heat pump:
https://ammonia21.com/norwegia... [ammonia21.com]
Not yet commercially viable and just demonstrated in a lab unit within the last few years, so probably 5 years from running a demo plant. Still, I can see running such a pump as the input to a thermal battery as being a great proof of concept use case, there's no critical load depending on the heat output being available 24x7 so any need to tinker, troubleshoot, or maintain the prototype can easily be accomplish
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Re:10% efficiency (Score:4)
It is 100%, everything goes to heat in the end. Old school light bulbs are still 100% efficient as heaters, they are just inefficient at outputting energy as usable light on its way to heat. A heat pump is able to achieve better results by moving heat in from somewhere else, producing more heat in one area by making another area colder.
However, on the way to get that energy into electricity is where the inefficiency may come in. E.g. if you have natural gas as your power plant source, it's better to just pump the gas out and burn it in furnaces, since some of the natural gas energy would otherwise become heat in the power plant, which doesn't need that much heat.
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It is 100%, everything goes to heat in the end. Old school light bulbs are still 100% efficient as heaters, they are just inefficient at outputting energy as usable light on its way to heat. A heat pump is able to achieve better results by moving heat in from somewhere else, producing more heat in one area by making another area colder.
However, on the way to get that energy into electricity is where the inefficiency may come in. E.g. if you have natural gas as your power plant source, it's better to just pump the gas out and burn it in furnaces, since some of the natural gas energy would otherwise become heat in the power plant, which doesn't need that much heat.
False because words have accepted meanings. You are conflating heat with energy. It is 100% efficient (or practically so) at energy conversion if you sum up all outputs and compare them to the input. Visible wavelengths of light are not considered part of the infrared spectrum and as such are not considered heat, even though they may be captured and reradiated as multiple lower photons in the thermal band. No one ever said light bulbs were zero or 100% efficient.
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But visible light becomes heat, from the perspective of heating a room. It's just an very slightly indirect path to becoming thermal energy. It may become heat further away from the point where electricity is running, but it is going to become heat in the end.
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But visible light becomes heat, from the perspective of heating a room. It's just an very slightly indirect path to becoming thermal energy. It may become heat further away from the point where electricity is running, but it is going to become heat in the end.
True. But that’s because you added a boundary condition that reradiates them at a lower (equilibrium) energy. If there was no room, but an infinite void, then the visible electromagnetic radiation (and the infrared as well really) would be lost. Even for a room the air itself isn’t going to absorb and radiate enough to make much difference.
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I look forward to the patent on your infinite sand battery.
We actually have one, the earth. It generates twice the power used by all humans today through radioactive decay [scientificamerican.com] and has no problem storing it all indefinitely at nearly 100% efficiency on human scales. Further, there are actually functional dark solar panels using the power of the atmosphere vented to the background of interstellar space. They use thermo radiative optimizer diodes [interestin...eering.com] such that on a clear night if you point them to space you will receive much less photon pressure than is in equilibrium to
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Sure, electrical resistance may not be 100% efficiency at heating an infinite void, but I don't think that's a concern we need to worry about. The spherical cow will just have to deal with the cold. In the practical scenario, the light will become heat after bouncing off enough surfaces within a room.
This is all nitpicking at the word 'efficiency', which in this specific context is pretty well 100% in practice, but does not speak to the efficiency of getting the electrical energy in the first place and oth
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This is all nitpicking at the word 'efficiency', which in this specific context is pretty well 100% in practice, but does not speak to the efficiency of getting the electrical energy in the first place and other solutions like moving heat around.
My god, yes this^. I nitpick because of how it is framed and explained, there is far more confusion than needs to be. I nitpick specifically because it was painful to have it presented in only the absolute terms, and not to a process as compared to a perfect idealized process with the same environmental constraints. Believe me when I say I bothered my mechanical engineering professors relentlessly to the point I’m pretty sure my CV took a hit but I don’t care if I can just change one mind.
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1) "conflating heat with energy" - heat IS energy. Not all energy is heat, however.
2) "If you sum up all outputs and compare them" - their point is that "all outputs" eventually turn into heat. It's a consequence of entropy. And it doesn't matter if that heater radiates some energy given that it's surrounded by objects opaque to the wavelengths it would radiate in in any meaningful quantity.
3) "not considered part of the infrared spectrum and as such are not considered heat" - infrared light IS NOT heat.
Re: 10% efficiency (Score:2)
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All of those energy "losses" turn into heat pretty quickly. For all practical purposes resistive heating, like an old fashion lightbulb is 100% effective at turning electricity into heat. That's also why they're so ineffective as light sources. Of the radiation they produce, it's like 95% infrared, i.e. heat.
Time I learned 100% is also 95% for what must be very large values of 95%.
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The formula for maximum efficiency of conversion from heat to mechanical work is 1-(Tcold/Thot), temperatures in Kelvin.
Cool kids do it in Rankine. But this is why all thermodynamic processes are ruled “inefficient”, because your cold source reservoir is ambient which is actually quite hot. Never mind you never paid for that ambient heat and got it for “free” as in you didn’t pay for it. The more sensible process efficiency would be to assume the ambient thermal conditions are the zero mark instead of the absolute, then you are left with how optimal the process is compared to a perfect proce
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A heat pump is usually designed to work with a medium that can flow through the heat exchanger for creating a difference between the two sides - e.g. pumping a refrigerant through the exchanger to transfer heat to air, which convects away to supply the exchanger with more air.
Sand doesn't convect very good, so it would be an interesting design challenge.
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Hot air can be made to flow through sand just fine.
A problem does come however if you're wanting a heat pump to pump up to 500C. Good luck with that ;) Your COP will be awful.
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This is fine for smoothing out variable supply from wind in winter. The wind blows for a few days, you heat the sand up. The wind stops for a few days, you use the heat. A 100t silo can store about 36 GJ or 10 MWhr.
This is useless for smoothing out variable supply from solar. Solar has a peak generation in summer, when no-one has a use for excess heat. It has a minimum generation in winter, when everyo
Citation Needed (Score:5, Informative)
Resistive heating converts 100% of the energy used into heat. It's literally the first sentence of the first search result.
https://www.energy.gov/energys... [energy.gov]
Not quite 100% (Score:2)
Some of the energy (a very, very small amount) will go into RF radiation even if the supply is pure DC because of the random nature of electron flow.
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Sure, some goes into RF radiation, and some goes into sound, etc. Inside a vessel where those things are basically trapped, they end up as heat again and the overall efficiency still ends up as very close to 100%.
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The big problem with solar is storage. If we needed five or ten times the solar in order to go 100% solar, it would still be cheaper than dealing with global warming. 200 billion is a conservative estimate of the costs of Fukushima. That alone would buy a whole lot of solar. So solutions like these are the way to go, especially for heating instead of going back to electric.
Re:10% efficiency (Score:5, Informative)
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Efficiency is an ill defined term when it comes to electric heaters. After all any kind of electric device, regardless of what it does, would have 100% efficiency in the same way. Like your video gaming console has 100% efficiency, while also entertaining you (perhaps) or your cryto-mining farm also has 100% while possibly generating you a net gain in the greater fool market (as long as there are greater fools).
I'll just quote here a 12 years old post from physics.stackex
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You can certainly express efficiency as one thing versus another. That's typically how people talk about heat pumps, and it's exactly what your number is (technically, the coefficient of performance), except you put resistive heating in the denominator instead of the numerator.
However, you can't just claim "10%" like the OP did without saying specifying the comparator and the conditions of the test. The efficiency of a heat pump drops as the temperature difference increases, and for a heat storage system yo
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If I understand my thermodynamics correctly then 100% is actually the default, because eventually everything will end up as "waste heat" regardless of what you do.
And that's the problem with the grander picture her
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No, 100% isn't the worst you could achieve. First of all there's a control system somewhere, likely outside the sand area, and it's consuming power and not contributing to work produced, so the heater isn't really 100% efficient. Then there's losses in the wiring outside the "sand battery." And you can't perfectly insulate the sand or get all the heat back out. But let's compare this to heating the sand with some combustible source. That'll definitely be significantly less than 100% efficient because y
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To keep it short, I do agree that for the purpose of converting the electricity into recoverable heat from sand based thermal storage. It would be well below 100% if you consider everything from the generation of the electricity to the thermal energy that you get out of the storage again. Which again, is just thermodynamics.
That's a realistic take considering more than just the pointless nitpick factors. You put it into the context of what amount of energy goes into the storage.
Re: 10% efficiency (Score:2)
It's only a problem for ground source heatpumps if they don't return heat in summer. In my country large scale installations have to run at net zero ground heat load across the year, but small ones are exempt.
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With your lightbulb example you're measuring how much of the input energy is converted to "useful" light in the process.
But for heat? You've always get 100% conversion efficiency, because everything turns into heat eventually. To me that means everything is at least 100% efficient when it comes to the context of heating. Even that supposedly 80% lightbulb, that supposedly would convert 80% of the input energy to usable light, will have that light
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The general consensus is that while it's technically true, it's practically marketing bullshit to confuse the uneducated, like you.
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I have a long family line working in the field and grew crawling on schematics of various parts of power plants because both my parents worked in the field and would often bring their work home.
OP is completely correct in his estimation. I've seen a couple of times when a marketing pro would try to spin efficiency numbers the way the article does in a room of engineers, only to get interrupted by senior engineer in the middle of presentation and get a dressing down of such harshness level that presentation
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You'd be shocked how many smaller subcontractors don't send engineers to sell engineering things to large multinationals. That actually works on the execs who tend to be business people with surface understanding of underlying engineering.
Which is why a lot of multinationals nowadays mandate presence of a senior engineer in relevant fields for final presentations before decisions are made on such issues.
Re:10% efficiency (Score:5, Informative)
Electrical resistive heating has a one way efficiency of 10%.
Completely false, resistive heating is over 99% efficient at converting electricity to heat. Only sound and some light escape, it’s actually typically over 99.7%.
You’re likely confusing it with heat pumps or something, concentrating existing heat energy is often cheaper because you get the pile for “free”. To see just how stupid the laws of thermodynamic efficiency are explained, you need look no further than the atmosphere. It’s possible to extract near infinite (on human scales) energy for free because it’s about room temperature and you didn’t pay for it. You then just exchange it with low energy photons to the vacuum of space, the cold reservoir near absolute zero, whose thermodynamic efficiency is also over 99%. Only when you realize there is a “high resistance” barrier to overcome does the actual picture of what’s real come into focus. This is how it is calculated and not expanding/transferring the heat to absolute zero but instead the ambient is the reason all thermodynamic efficiency is so very low, despite being close to the maximum efficiency possible.
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Re:10% efficiency (Score:4, Informative)
How does this get modded up? It is exactly backwards from the truth
No it isn’t. You have failed to learn physics or engineering past a reddit meme level, or perhaps past some misleading advertising literature. Resistive heating is nearly 100% efficient, until you start getting so hot an effective portion of the photons fall out of the the thermal radiation band but this process is dependent on temperature to the fourth power so is irrelevant then quickly becomes the dominant source of energy transfer. Any thermodynamic process is considered inefficient because we vent to ambient temp not absolute zero but in reality calling a process 30% efficient when you never paid for the 70% and the process is 100% efficient seems stupid and backwards to me but that’s how it is presented to the world from institutions.
Heat pumps aren’t efficient In absolute terms. What makes them “efficient” is you don’t pay for the heat in the first place. Concentration of the existing heat you got for free costs less (sometimes even 5 or 6 times less) but does not “create” more energy than you put in. Source: I have a masters in mechanical engineering but really all you need to understand this is high school physics.
Re:10% efficiency (Score:5, Interesting)
The parent is correct; resistive heating is ~99+% efficient (with a miniscule loss to sound and light, rather than heat, energy).
However; that doesn't make resistive heating more efficient than a heat pump. Someone else had the right numbers, and several have linked websites, but the key is understanding *where* the efficiency is applied.
To heat a room? Heat pump wins; ~1 unit of electrical energy can transfer ~4 units of heat energy (~400% efficient!), compared to resistive heating at 1 unit in = 1 unit out (0.99 units out...)
To *generate* heat, rather than transfer it? Resistive heating is, as noted, ~100% efficient. There's not much more efficient; even burning things "only" transforms stored chemical energy to heat, and you're limited there to a 1:1 (100%) theoretical efficiency limit. Electrical resistive heating here is "inefficient" - as compared to say natural gas or other hydrocarbon sources - in that the cost (in your local currency) of 1 unit of electrical energy is generally much higher than the cost of 1 unit of stored chemical energy (at least in the hydrocarbon sources commonly used). I see this in the inverse; cooling my house (with a heat pump/AC unit) by ~10C in the summer costs me rather more than heating (with natural gas) by ~30C in the winter (as compared to rough outdoor temperatures).
In this particular scenario -- heating sand as a "heat battery" -- I suspect that resistive heating, using "free" (read: otherwise wasted) wind/solar/other renewable electricity, may actually be more efficient than a heat pump due to the target temperatures involved (~500C), and given the simplicity of the technology required. When your input cost is the infrastructure, not the energy, a cheaper but less energy-efficient infrastructure may be the winner.
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That comment about target temperatures is key, heat pumps are great when you don't have a terribly uphill climb for moving heat from one area to another. I.e. the smaller the delta in temperature, the easier it is to move heat from one to another. Trying to heat something up to hundreds of degrees more than ambient? Heat pump won't get you that far.
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I suspect that resistive heating, using "free" (read: otherwise wasted) wind/solar/other renewable electricity, may actually be more efficient than a heat pump due to the target temperatures involved (~500C), and given the simplicity of the technology required. When your input cost is the infrastructure, not the energy, a cheaper but less energy-efficient infrastructure may be the winner.
This is spot on. I wish we had better ubiquitous terms for how thermodynamic efficiency actually works. I have tried to convince many people including my engineering professors that a better framing for laypeople and everyday operations on earth is process efficiency which is the efficiency of the system compared to the thermodynamic limit. Heat pumps can often be several hundred percent efficient in the process because you only need expend one unit of energy you pay $$ for to get back several units of
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One more voice saying you're wrong about efficiency, though right about heat pumps.
Efficiency is determined by a very simple formula: (energy out)/(energy in). Or for a one-way analysis of a storage system: (energy stored)/(energy in). And resistive heating is 100% efficient. As are most other forms of heating, since heat is the waste-pit of the universe and everything ends up there eventually.
Heat pumps are actually much more than 100% efficient - usually somewhere in the 300% to 400% range for residen
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This is the PR aimed at the ignorant. Reality is that you can measure efficiency in two ways:
How much energy you spend for what outcome. For energy storage systems, that would be "how much energy you're putting in, vs how much you get out". For heating systems it's "how much energy you spend to get how much increase in temperature in whatever it is you're heating".
This is how engineers do it, because this manages numbers that are relevant to the OUTCOME. The other way is the marketing, which measures only t
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I'd suggest you read the post to the end before you open your mouth and remove all doubt about your intelligence. But then, I'd have a lot less fun just copy-pasting a few lines down from the post you quote above addressing that very point:
>Most thermal batteries have a very low efficiency for reasons of inefficient heating (in this case, resistive being very inefficient but likely necessary because of high operational temperatures involved making heat pumping not viable)
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Re:10% efficiency (Score:4, Funny)
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Resistive heating is as close to 100% efficient as it can get - you put 1W of electricity into the resistor, and you get 1W of heat out.
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Their company website claims "efficiency up to 99%".
https://polarnightenergy.fi/te... [polarnightenergy.fi]
I stopped reading there because I understand physics and know that this is marketing wank that claims what is effectively impossible for multi-state energy transitioning system even in absolute best case scenario.
Efficiency is one of the biggest problem with energy storage systems, and if they can't tell you what theirs is even in ballpark terms and instead lie by omission to such an extreme degree, their system is certainl
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I am not sure "heating" can have a meaningful efficiency. This a heat storage system designed for district heating. We have had them for decades ("storage heaters") in residential homes. The question is how much of the heat that you put is in kept till when you need it, which is another way of saying "is the insulation any good". With storage heaters, that was always a problem because they couldn't be very big. This can be, to a first approximation, as big as you like. For shifting solar power to night heat
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Re:10% efficiency (Score:5, Insightful)
In which case any process is 100% efficient at generating heat.
If you're going to claim it's something else, like 10%, you've got some 'splaining to do.
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"should work pretty well" (Score:1)
For shifting solar power to night heating, it should work pretty well, I'd guess.
How many solar panels would be required to heat the sand up enough to heat a home for an entire night, vs pretty much any other energy storage mechanism using fewer solar panels to store energy but producing the equivalent heating in homes.
And even if the sand were efficient (which it's not) you have tremendous transmission losses piping warm water out to homes.
Re: (Score:2)
If your input fuel is free (solar) efficiency falls off in importance.
Same reason cars in the 50s got 10 mph. Fuel was extremely cheap so it wasn't really important to be efficient.
8000x more energy hits the earth per year with just solar than the entire human race currently uses from all sources *combined*.
That's a huge amount of efficiency loss that
Re: (Score:2)
You know cities already use central steam heat right?
Yes, how many solar panels are needed to heat a large mass of sand to where you can actually get steam by running water through it? And how long will it be able to do so?
Read up on how New York's Steam System works [untappedcities.com] and then think of how much sand and how many solar panels would be required to replicate what they are doing.
You know OF the New York steam system, but I know how it works.
Not that many cities use steam anymore though, because it turns out el
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Electricity is indeed more efficient to transmit....when you have it to transmit. The efficiency of a solar panel at midnight isn't great.
The entire point of the sand *batteries* is to allow that energy to be stored for *later* use. You do realize that right?
Hell you don't even need solar panels, you just need mirrors for a concentrated solar to heat
Re: (Score:2)
Oil does not cost anything either.. It's digging it up and transporting it that puts a price-tag on it.
Please let us know the cost of transporting sunshine to a solar panel...
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The cost of transporting sunshine....is the sun itself. Well, the expenditure of "fuel" that the sun needs to create this "sunshine" you speak of. And most of those sunshine rays don't even end up here on this planet. But the transport of the sunshine rays that do land on the surface of our planet is without further cost to you or me or the environment being able to develop itself on this planet.
Oil is nowadays expensive to dig up as most close-to-surface wells have been emptied. Then it needs to be transpo
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In a dumb attempt to refute my 'solar fuel is free' the previous poster had claimed that
Oil does not cost anything either.. It's digging it up and transporting it that puts a price-tag on it.
So I asked the obviously silly question of how much it cost to transport sunshine to the solar panel.
The fossil fuel industry trolls simply can't grasp that a 'fuel' could be free.
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You do not "have tremendous transmission losses piping warm water out to homes". Municipal heating systems are very efficient. The main loss mechanism - overwhelmingly - is in the wastewater, which is still (at least based on our system in Reykjavík) still about 30C. I'm involved in research to reuse that heat, BTW. :)
As for "how many solar panels", if you had read the article, you would have realized that the problem is that they have insufficient power in the winter but excesss in the summer. So
Re: (Score:2)
How many solar panels would be required to heat the sand up enough to heat a home for an entire night, vs pretty much any other energy storage mechanism using fewer solar panels to store energy but producing the equivalent heating in homes.
And even if the sand were efficient (which it's not) you have tremendous transmission losses piping warm water out to homes.
It would be way better if they used CSP to heat the sand.
Re: (Score:2)
This can be, to a first approximation, as big as you like. For shifting solar power to night heating, it should work pretty well, I'd guess.
I’d agree with that statement, surface area scales as a squared function of linear distance or “size” while volume scales to the cubed power. Thus for double the length, you’d have four times the area for the heat to leak out but 8 times the heat for a given temperature. So by creating a minimal surface area shape and by making it large, it becomes very easy to make long term efficient storage possible. Unfortunately the way the efficiency is calculated by default is if you store