There is no need to store summer heat for the entire winter, which would necessitate a far larger capacity system.
One would only need to store solar thermal energy that is available on any sunny or partly sunny day for night time and cloudy days.
Where I live about half of all days produce abundant solar thermal energy even in the depth of winter. Calculating in night time, you end up with about 12.5% of total winter time having abundant free thermal energy.
So one would need to build a system of solar thermal collectors about 8 times the size one would need to heat a house on a sunny winter day, and that is not a very big system.
Space wise I think it would work for single family residential homes on .25 acre lots if the house was designed for it from the start.
This exists already and is called a liquid to water heat pump, where a liquid is circulated in long pipes either buried under your lawn (if it's big enough) or inserted in holes drilled several hundred feet deep, and then passed through a heat pump to provide hot water that's then distributed through your house.
You just need to go ~20 ft down for the thermal mass of the soil to significantly damp out even annual oscillations, so there the soil temperature equals the mean temperature where you live.
The main barrier to adaptation is that most people don't have a big enough lawn for the shallow method, and the cost of the deep method is big enough that it takes too long to break-even for most people.
What we really need for any such method to succeed is that governments must make it mandatory for new houses, then we can get economies of scale and probably make it viable also for retrofits.
Heat pumps have greater than 100 percent efficiency when compared to a regular resistive electric heater (which is already 100 percent efficient, when measured as heat out / energy in).
Everyone always forgets about the part where you're cooling down the outside...
Yes. Heat-pumps will make up for some losses from all other steps but I highly doubt it all togrther will reach efficiency of purely thermal system. Heat pumps also rely on access to medium that they cool down to get the additional heat and are at least as complex as a fridge or air conditioner.
It might be that one or the other is better "in general", but I can see that this technology could have benefits in certain scenarios, maybe long term storage in remote, cold climates.
No current electric battery technology has the energy density to heat a house all winter economically. You'd need a volume of batteries similar to the volume of your house.
The opposite of saving winter ice for the summer was popular in the 1800s before mechanical refrigeration. Ice can last many months if insulated by sawdust below ground.
Princeton had an "ice pond"[1][2] in the early 80's. The project was run by Dr. Ted Taylor[3] (who worked on the Manhattan project and later the Orion spacecraft-- huge nuclear bomb-powered spaceships!). Snow machines made slushy ice that was stored in pond covered with insulation. Water was pumped through the pond in the summer to provide cooling. It worked well and at the end of the summer there was still ice in the pond.
I read about this as a kid reading Freeman Dyson's "Imagined Worlds"[4]. Dyson's commentary is definitely worth reading. (Anything written by Freeman Dyson is worth reading.)
A cheese factory used ice ponds[5] for about 10 years, eventually abandoning them because the ice didn't last through the summer and it was difficult to maintain[6].
The storage facilities are called Ice House [0]. The large ones stored several thousand metric tons and could last through the whole summer, depending on the climate.
Another way is to simply use the ground. Dig trenches, lay in pipe. The ground is cooler than the air in summer, can warmer in winter. I read that using it as a heat exchanger can cut HVAC bills by 30%.
These systems are pretty popular, even my dad has one. The problem is they're also pretty expensive -- on the order of $20,000. At that price it could take a long time to hit break even, at least in the U.S.
With improvements in refrigeration technology they may never. If you compare installing geo-thermo 10 years ago vs someone who installed an air source heat pump, and then upgraded (at optimal times picked on hindsight), the latter has paid less for equipment, and his yearly costs are now less as well. Geothermal equipment is enough more expensive that upgrading doesn't help those numbers much even though the expensive pipes in the ground are still perfectly good.
Of course there is eventually a limit in efficiency gains. When you reach that limit geothermal has advantages that will pay off eventually. 10 years ago at least you should not have installed geothermal. What the next 10 years will bring is beyond my knowledge.
According to this [1], the 2015-16 estimated average residential winter heating bills for a propane user ( the highest ) was $2,569. The cost of this system is approximately equivalent to 7.8 years of heating costs. If this system saved 50% on the bill then it breakeven is about 15 years out. These numbers aren't too far from solar historically, if I recall correctly.
The main expense is digging the trenches. If this is done before the house is constructed, i.e. you've already got the backhoe on site to prep the site, the cost should be minimal.
"Expensive" is always relative to the overall cost of construction. For a $400K home being custom made that's not as huge a hit as it would be to some place that's a $100K fixer-upper.
An in-floor heating system can easily cost $5K or more. Installation is the big cost on these things.
Expensive is already relative to the alternative. If a furnace can provide the same comfort at $5k, it takes a long time for the cost savings of the heat pump to make that up.
The real savings is that in new construction, you don't have to pay the extra cost to retrofit.
As I understand it, using the ground as a passive thermal sink is great for 'survival' but not so great for 'comfort' in my experience. A coworker of mine built a log home in Montana with a thermal reservoir which put the reservoir heat exchanger 80' under ground. Water is circulated through radiator type devices in the house.
It certainly takes some load off the HVAC system but I didn't get the sense from him that it was as much as 30%.
Who puts in a system like this? It costs an absolute fortune to install one of these and a nearly complete waste if all it can do is circulate a bit of ground-temp water around the house. The typical thing to do is to connect the ground loop to a heat pump which greatly increases the amount of heat transfer (in either direction).
I believe you are correct. Below 6' the earth is consistently 55ish degrees. Even with perfect/fast transfer of heat that would mean the max winter temp of your house would be 55 (since it's often colder than that there.) Of course given perfect/fast transfer of heat, it would work wonderfully in the summer. But I assume there are pretty significant limitations in how quickly a body of 55 degree water can cool a 90 degree house. Which is also a common summer temp there.
Are we talking heat pumps or a different passive heat exchanger system? Air-con/heat-pumps/refrigerators can extract heat from surprisingly cold sources as long as there's enough of them e.g. the city of Dremmen that extracts heat from the near freezing North Sea to heat water to near boiling point.
The original claim of a 30% saving seems like the jump from from air source to ground source heat pumps which are often quoted as giving back 3x or 5x the energy put in, respectively.
I think this kind of technology has enormous potential to improve human life. Bad weather is a huge, chronic problem that makes almost everyones' life substantially worse. Just the other day my aunt broke her wrist after slipping on a patch of ice.
One question though: why do they need a special high-tech material to do this? Why can't they just bubble warm air through cold water in the summer and vice-versa in the winter? Water has very large heat capacity, 400x that of air by volume.
Lye itself is pretty low-tech -- but being able to safely and repeatedly hydrate and dehydrate it while controlling the heat transfer, that itself may require some finesse.
As others have pointed out, there's no need to store heat for six months. But you bring up a common enough viewpoint, one that I think bears re-examining:
>I'd imagine there's not enough water to do this inland..
We quite often forget that there's no physical limitation on the amount of water available inland. Water is constantly flowing from the oceans onto land, being recycled (mainly by trees pushing it back up into the airstream), and flowing back out and mixing with the ocean.
So the amount of water per square meter of land is limited by only two variables:
* The rate at which fresh water falls on land (liters/hectare/year)
* The time it takes that water to flow to the ocean (years).
The amount of water available on land (liters/hectare) is simply these two quantities divided by each-other.
The flow is fundamentally limited by the energy balance of the sun, so there's not much we can do there. But the time is entirely determined by our ability to design infrastructure and land use patterns that store water on the land in useful catchments instead of draining it off rapidly. Farm-scale dams are one visible way of doing that, but it's much cheaper to store water in the ground via infiltration systems.
The amount of water is inversely proportional to the amount of time it takes water to flow back to the ocean after it falls. So if we want to "wet up" the landscape, we should make it follow a loooong path with a lot of passive friction and storage buffers.
Just to show my math here, in the USA on average there's 715 mm of rainfall per year, which works out to 19,000 gallons for the average 100 m^2 house footprint. And next year you get that much water again.
In extremely arid areas like California it would even be possible to use salt water for thermal storage.
That's true for west coast cities, but not for east coast cities like Boston and New York, which experience terrible temperature extremes.
How much water do we need? I wouldn't try to affect large regions, just specific urban areas. The water doesn't actually have to go anywhere, it just sits around storing heat. All we have to do is bubble a lot of air through it. As a nice side benefit, this should clean the air.
Are you proposing that we capture heat this way to warm houses (in which case it's a terribly ineffective and inefficient system) or to actually raise the outside temperature? If you're proposing the latter, there's just no way. Water might store 400 times as much heat per unit as air, but there's an absurd amount of air hovering around a town and an enormous area that air mixes with constantly.
NaOH is a super cheap, common chemical. It's the principal ingredient in Drano and similar plumbing cleanout products.
High concentrations of NaOH in water are strongly basic. It will corrode many oxide-based ceramics (like toilet bowls) and aluminum, but it's no problem for most other common metals and plastics.
I think practical applications would transfer the heat to pure water in a heat exchanger instead of delivering the NaOH directly to the radiator. In a well insulated system, the losses should be minimal
No, if the sodium hydroxide is already in solution then diluting with copious water is one of the best ways to deal with a splash on skin. You're right that adding water makes the problem worse if you have e.g. a spill of prills to clean up.
I had looked at dry storage of heat using NaOH a while ago, I can't recall the energy density but it's on wikipedia.
The bigger problem that I found was that the efficiency was horrible. I wonder if having it in solution resolved this problem, if that's the case then there's going to be some applications for this with even a reasonable energy density.
Wikipedia says 44.51 kJ/mol, so that should be 309 Wh/kg, for dry NaOH dissolved in water. The amount of energy needed to heat 1 kg of water with 1 K is 1.16 Wh. So the heat released from dissolving 1 kg of NaOH in water will heat 10 liters of water with about 26.64 K.
It is also more than twice as dense as water, so the amount needed to heat 100 liters of water with 53,3 K will only have 1/10th the volume of said water. So even if you only use a small area in your basement for energy storage, it should be enough to have hot baths all winter...
20kg of lye for a bath seems like a lot. That's 2000 kg just to get through the coldest 3 months. Multiply that by the number of people in the house. And then remember to add space for all the water you'll have to mix with the lye to extract the heat. And actually double the water space if you're going to keep it after recharging instead of dumping it.
2000kg of NaOH has a volume of less than one cubic meter. And I don't get for what reason I would have to store the water needed for the reaction instead of just connecting the device to whatever water supply the house uses.
A cubic meter per resident. For just 3 months of the years. And each unit is diluted 50% already.
As for the water, you're going to basically dump a bunch of water into this thing to generate heat. And when you're done, your NaOH will be more dilute and need a bigger storage vessel. So you need enough room to store all the water you'll ever add.
When you recharge, you'll produce a bunch of water, too. You either dump it or you store it for the next use. If you store it, then you double the amount of storage that you need for water because you have room premix and postmix.
You could use a cubic meter of solution and store the heat underground then use a heat pump to extract it. But that could be also done directly by heating the ground using excess solar. Lye seems better suited for daily storage - store during the day, extract at night. Mostly useful in the desert or during the spring/fall when day/nught temperature variations are high and solar irradiation is good enough.
I think a better design would be to construct a reinforced holding tank underground (either underneath the basement or adjacent to the house) that would hold the NaOH solution, then lay piping and use a pump to circulate small amounts of it to a heat exchanger in a central ventilation system.
Wikipedia notes that it reacts with aluminum but not with iron. Iron is relatively plentiful as well and we know how to build holding tanks with that material.
It's probably not a good idea for earthquake-prone areas, but this method might work ok in places like Minnesota to replace burning LNG in a furnace or coal-plant-powered electric heating as the primary source of heat in the winter. I guess it depends on the reaction rate and efficiency of the system - how many tons of NaOH would be required to heat the house throughout the entire winter?
"how many tons of NaOH would be required to heat the house throughout the entire winter?"
This is one of those cases where the fact that it wasn't mentioned leads me to believe "embarrassingly large amounts".
(That said, the technique may not be useless, and they may have a valuable machine. It's just that this particular application is setting off my energy-scale alarms. Press releases tend to get pretty breathless.)
I have worked with NaOH before, and I think the amount required would probably be more than a (US tank-style) water heater and less than a typical above-ground swimming pool.
I think you would need some of the tables typically found in chemical engineering manuals to work out the exact amount.
You would need the heat capacities for 50% and 30% (wt%) aqueous NaOH, mass fractions, enthalpy of dilution, and maybe activity coefficients. It sounds like a homework problem for a ChemE student.
Yeah, I never took enough chemistry to be confident I could get that correct or I would have done it myself. I've done Physics 101 BotE work on HN before but I'm pretty sure I'd have screwed this up. :)
I agree. One would hope that when this research-level technology reaches the market, they can effectively isolate and contain the NaOH, and have some solid safeguards against malfunctions.
On the optimistic side, we've mostly succeeded in doing that for other volatile things like gas tanks in cars and lithium batteries in electronics.
On the pessimistic side, the failure modes can be very catastrophic! I'd definitely want to know what failsafe mechanisms are in place to prevent my house from blowing up before I'd consider using it.
Personally I would have no problem to have that stuff in the basement, whilst having it circulating in pipes just under the floor (you know, the heated kind, where likely you go around barefooted) might be an issue. Also, consider how on multi-storey houses the ceiling is nothing but the underside of the upper floor. ;)
Sure, I do hope that those scientists are not totally irresponsible.
Still another heat exchanger will further lower the efficiency of the system. In my experience (maybe a tad bit dated) common heat exchangers (water/water) are difficult to maintain as - generally speaking - the most efficient ones have smaller passages for the liquid and they tend to become clogged and it is "normal" to clean them periodically.
I have no idea how large must be a heat exchanger (where one of the fluids is lye) to be efficient enough, considering also that the temperature is relatively low, but most probably it won't be exactly "compact".
Ammonia is already a product that is stored and used by lots of people. It is a common fertilizer. There are guidelines for safety equipment and tank maintenance, but I'm not convinced that everyone follows those.
I think ammonia's next big application will be as an easier-to-use form of hydrogen for fueling ICEs with renewable energy.
This reminded me of a similar system that uses the same tech as those hand warmer things that have a chemical that changes state, either absorbing or releasing energy. They also talk about absorbing heat and physically transporting it. The example they have was waste heat from industrial processes being shipped via canal to a district heating system.
> The heated water generated in the process of condensation is then transferred to a geothermal probe (generally loops of pipes embedded vertically in the ground) for storage and retrieval.
That is a neat approach. It works well for solar-heated water. Where winters are very cold and summers hot, one can also have cold-storage loops for summer cooling.
I'm not sure about the NaOH thing, however. I get that it enables heat transport. But as scotty79 notes, transporting concentrated NaOH is hazardous. It's already done, of course. But the scale for heat transport would be much greater than as chemical feedstock, I think.
I usually find these types of new green technology to be impractical, and obviously not going anywhere (store energy by dragging a train uphill for example).
Let's assume a large example: trains weighing in sum 20 000 tons (e.g. 200 freight cars, each weighting 100 tons, probably distributed across a few trains), and an incline with a height difference of 1 km (which is going to be very long to be usable with heavy trains).
that's 20 000 000 kg * 9.81 N/kg * 1 000 m = 196 200 000 000 Nm or 55.4 MWh stored energy (without efficiency factors, so not the usable energy at the end).
In comparison, a stored-hydro plant typically has between 200 MWh to 3 GWh capacity.
Maybe you could stack even more trains on it? But that again adds complexity and costs (more locomotives needed). I'm not convinced it will work out in all that many locations. And how fast can you transfer power in and out, with limited train speeds and overhead wiring?
Stored hydro is simpler and at least just needs space to scale the capacity, so you can make it a lot larger, even if it also only works in selected suitable locations.
(Sorry for editing this so much, should have written it out in a text file beforehand ;))
My understanding of the idea is that they plan to move the weights up the hill by train, but then unload the weight. That way, with just one car, you can move multiple cars' worth of weight up the hill. Now, this bottlenecks you on how quickly you can store/release energy, and you have to store a lot of cargo containers in a possibly small space, but even moving 4+ cars' worth of weight per car brings the total stored energy capacity up to that of a smaller stored-hydro plant. Not to say this is necessarily cheaper than stored hydro, but it at least costs a lot less in terms of excavation.
That is greenwashing taken to anther level. They are not just pretending to be green, they are actually doing harm and wasting money that could be used in better places.
If you read the article you'll notice they refuse to compare to pumped hydro (because if they did people would laugh at them for how expensive they are). They are happy to compare to batteries though, because those are also not a usable way to store energy in bulk.
Sigh. With projects like this is it any wonder people are so skeptical of "green technology"?
There has to be some political reason this is getting built, because there sure isn't an economic or environmental one.
Then rail energy storage only works in areas with railelectric plants.
Pumped hydro works anywhere with a power source and a water source.
Dragging a train uphill for 5 miles to store energy sounds moronic. I bet the losses in this system are absurd. It also creates a 5 mile virtual chasm that's potentially unsafe to across.
Hydro storage works because water is available in huge quantities without much special work, and you don't need any infrastructure except "big hole". Neither of those are true for a train or weights.
These technologies are existing since 115 years (heat pump) and have been mass produced in the 1950.
The article is unwillingly misleading. It is not new technology per se, it is an improvement on a very old technology that is as simple as the Sterling engine.
Britain (France) has been a massive adopter of this, having a paradoxal effect on aggravating the power peak in the morning inducing the use of coal plants to be massively used in the morning to face this peak since pump were electricity driven.
But with mechanical wind mill, or solar power maybe they could finally become green.
As usual evil lies in the details, and most new new techs are deceptive because we lack knowledge. This is an old tech, and we know the trap.
Is this something that could be used in a dense urban residential setting?
Is the reaction extremely volatile? Does this require a high-tech ultra-low-tolerances system, or can it be DIY-ed?
I can see having a setup on a condo balcony (esp. if you're facing south / west), with heat exchangers on an otherwise-unused wall, and a few cylinders of NaOH. As long as the kit doesn't blow the wall off the building if it leaks or some such disaster..
I'm not sure what you mean by "volatile reaction". NaOH is not super dangerous but I wouldn't trust a DIYer with large quantities, since it's so alkaline. You can find out more online by just searching for "MSDS sodium hydroxide" and you'll find phrases like "very hazardous in case of skin contact".
A leak in some DIY setup would easily have horrific / disfiguring consequences.
Assuming the 50% NaOH solution releases half the amount of heat released from dissolving dry sodium hydroxide in water, to store 1 MWh you would need about 6.5 tonnes of sodium hydroxide. The price for NaOH pearls 99% is 300-400$ per 1 metric tonne.
The article describes a method using NaOH for long-term storage and transfer of heat, taking advantage of excess heat in the summer to use it during the colder months of winter.
One would only need to store solar thermal energy that is available on any sunny or partly sunny day for night time and cloudy days.
Where I live about half of all days produce abundant solar thermal energy even in the depth of winter. Calculating in night time, you end up with about 12.5% of total winter time having abundant free thermal energy.
So one would need to build a system of solar thermal collectors about 8 times the size one would need to heat a house on a sunny winter day, and that is not a very big system.
Space wise I think it would work for single family residential homes on .25 acre lots if the house was designed for it from the start.