Nice to see a video on this technology! Compared to other types of longer term energy storage, I can see two big advantages to this that I don't think I've seen mentioned anywhere. The first is the potential to very cheaply add lots of extra charging power on top of the heat pump using simple resistive heating. That should be useful during infrequent periods of very low, or even negative, electricity prices where you just want to charge as much as possible no matter the efficiency. The second is that since this system is based on heat, it should be cheap to add a "deep backup" option were you simply provide the heat from stored chemical fuels once the heat storage is empty. The efficiency would be low, but I think it would be very useful for grids primarily based on wind power since it could hold you over through the very rare periods of multiple weeks of low wind. That would then save you from having to invest in a completely separate backup system based on gas turbines or the like.
Not usually commenting but just found out your channel, content is amazing. You provide all the necessary information. Well structured, detailled and with schemas. So hard to find these information elsewhere. Thanks for your work!
Thanks for running this channel and especially covering this storage solution. I believe Thermal storage is going to be a big part of the solutions during the energy transition world-over, especially because it will be relatively cheap. I had a quick question, I was looking for the study at 9:57, is it available for people to view/read and learn more?
Thanks for your comment. That is a slide that was given to me by Henrik Stiesdal, the founder of the company, and I don't have any more info than that. BUT like you, I think energy storage duration is a very interesting and important topic, so I am planning a video on that soon. When I make that video, I will include reference material where you can learn more.
Interesting to see the step through of how it functions. Looking forward to seeing them grow and become a standard part of utility scale as well as independent grid solutions. Great to see the simple technology become even more appealing in tandem with solar and wind.
Very interesting 👌. I think another important factor in increasing the efficiency and decreasing overall product cost is to use it near the onshore wind farms, using the storage material available in that area (less transportation cost) and integrating it with the nearby residential community's or any other necessity's, heating and cooling needs (by product from loss energy at charging and discharging)
@@EngineeringwithRosie the other possibility is to site near large low grade heat users such as food industry or glasshouse growers to use the low temp waste heat.
One metric that I didn't see raised was what is the daily/hourly heat loss of the system? Even if it is only targeted at daily cycling that would be interesting to know.
Thank you so much for this tour! This system and compressed air system, if they indeed have 60% efficiency and are 10-100 cheaper than chemical batteries, seem to be very suitable right now for energy transition. Because I don’t see any progress in the pace of installation of small and midsize storage systems anywhere in the world. Let’s take Germany as an example. Germany added only 5 GWh of batteries last year, which is a staggeringly slow pace compared to the goal of 5 TWh defined in Tony Seba’s report for Germany. (For entire power of the country 10 TWh of batteries are needed.) At the current MegaPack price of 270 USD/kWh + installation etc. costs Germany would need to spend 2 trillion dollars over 10-15 years only for these 5 TWh of batteries, which is 40% its GDP! And these batteries have a roundtrip efficiency of 87%, which is not too far from 60%. The question now is how much does Stiesdal system cost if mass produced? If it is 10 USD/kWh we all should start a campaign of advocating and informing the governments. This type of storage should also be suitable for “tankering”. In his paper “Rethinking Energy (2022). Germany's Path to 'Freedom Energy' by 2030” Tony Seba suggests for Germany to install 5 billion kWh of batteries (5 TWh) during 10-15 years, which is equivalent of 3.5 days of all electricity needs (1.4 TWh per day). In case of a 2-week winter Dunkelflaute, common to northern countries, the country will cover only 3.5 days via batteries. I suppose that the remaining 10.5 days can be covered via international fleet of tankers full of batteries: 4 tankers each day, 32 tankers in total for a region size of Germany (4 on recharging, 4*3 + 4*3 on a 3-day long trip to/from Africa, 4 on discharging), but for all regions simultaneously in trouble the number of tankers obviously must be larger.
Thanks for the tour. I prefer the sodium acetate as a storage of heat. Then you can add water back as needed to give the year up. The advantage is the long term storage for heat. The disadvantage is the size necessary and cost of material.
Nice video! Thank you for introducing this technology! I agree with the idea that you need to disconnect the costs of charging, discharging, and storage equipment in order to enable longer-term storage capabilities by minimizing the third component (storage). But often these types of technologies are presented in a vacuum relative to other competitors. The gentleman interviewed mentioned the primary drawback of batteries (cost), but he did not mention the benefits of batteries (efficiency and response time, for instance) nor did he talk about the more direct competitors to his product. In this space, hydrogen is another player which will have benefits and drawbacks and another notable technology is Advanced Rail Energy Storage (ARES). He also did not cover important drawbacks, such as the fact that such a large amount of waste heat may NOT have much utility in summertime except in specific industrial application. In order for this technology to find at least a single market in which to play, it needs to beat ALL other comers, not just batteries. The important figures of merit that come to mind immediately are: - efficiency (both one-way and round-trip since technologies like this one and hydrogen have differences on charge and discharge) - cost (of the various components) - size (floorspace or volume, whichever is important for potential applications) - durability (life) - energy lost in storage over time - energy storage horizon (What is the shortest and longest amount of time that this technology can be reasonably applied to store energy? Seconds, minutes, hours, one day, several days, a week, several weeks, months?) - environmental impacts The point is that we need longer-term storage technologies like this or hydrogen or ARES (or others or all of the above) that can make one week or longer storage an affordable reality, but they all have their benefits and drawbacks. I would be interested in a survey of prospective technologies in this long-term storage space. If you want to address the VALUE side of the renewables equation, that is perhaps the biggest hurdle.
Thanks for these comments, all good points. I am working on a video about energy storage duration, and I could include long-term energy storage techs in that video. Thanks for the suggestions!
Thanks, Rosie. Can you explain how a compressor acts as a heat pump here? I get that it heats the gas (by T = PV/nR and perhaps compressor inefficiency), but their website claims the COP to be 2.5 and you don't get that without a refrigerant and an evaporator & condenser combo.
@@iain3713 - Hmm. That doesn't seem right. The turbine is playing the part of the compressor, which is already part of a true heat pump system. If it's a heat pump, you need *both* an evaporator and a compressor - and the evaporator facilitates heat transfer via phase change, which at this temperature is impossible to happen to air. Most importantly, a heat pump's purpose is to move heat, whereas this device's purpose is to convert electricity into heat and pressure. The movement of gas from the cold reservoir into the hot reservoir is helpful for facilitating that electricity conversion, but it's an entirely different type of concept. Keep in mind also that heat pumps are meant to work to move heat from an *open* system (i.e., not insulated) into a place where you want to warm things up. You can keep moving more heat because of the openness of the cold reservoir. In this device, the cold reservoir is insulated; if you move heat from it to elsewhere, no new energy enters the system. In fact, the most telling difference between this system and a heat pump is that a true heat pump would be cooling down the cold reservoir by the fact that it removes heat, but in this system any cooling down that occurs happens because you're pumping in cold air from the bottom. The system removes air from the system, and some heat goes along with the air, but if they weren't pumping in cold air at the bottom the temperature of the cold reservoir would *not* change ... all that would happen is that the rocks would stay at the same temperature but would now be in a partial vacuum. (For reference: energyeducation.ca/encyclopedia/Heat_pump)
@@rasraster I may be looking at it wrong, but air gets compressed to above the temperature of the hot storage tank, transfers some heat to the storage tank, it expands through the turbine, doing work so it loses heat and cools down below the temperature of the cold tank, absorbs heat from that and cycle repeats.
It sounds like the compressor is being used as in a gas turbine to feed air into the system to drive the system in a particular direction. If the air is at higher pressure at the cold end, the heated exhaust gas will flow towards the turbine end of the system. A smaller pressure applied over a larger area or ar a distance further from the drive shaft than the compressor blades results in greater torque in the direction that they want the system to flow.
@@rasraster I'm having a hard time understanding it too. Most Joule-Thomson (air cycle) refrigeration machines I've heard of had a COP less than unity, which would leave a COP of less than 2 as a heat pump (generous, because most actual heat pump applications require a larger temperature difference and lower efficiency than when operating as refrigeration, especially in this case). One thing to remember is that air cycle machines can be open cycle, they don't necessarily have to have both a corresponding "condenser" or "evaporator" (gas heater, gas cooler). The only issue is that when operating open cycle as refrigeration, ice tends to form in the expansion device (usually a turboexpander to help with the already low efficiency).
What gets me excited about this is how the cost scales so beneficially with storage capacity. Probably for installations with a large capacity but relatively low rating is dominated by the cost of the steel tank rather than the storage medium, which means you have the cube-square law on your side. And then if you want to increase the rating, I guess you just need to get a larger turbine system, so you just pay proportionally for that. Thanks for this!
This seems similar to liquid air storage in it's efficiency, and also in that adding capacity is cheap. Also siting is much easier than pumped hydro, and I assume this should be fast to build.
Doesn't liquid air use something like this too? To capture some of the heat generated when cooling the air, then to use that heat to expand the cooled air later?
Great video! It is now two years old. It would be interesting to make follow-up videos for this type of content after 2-5 years. Is the company still around? Do they sell their system at some scale? Are there other companies doing similar things with the same technology?
Understand the terminology used here as heat pump refers to a compressor and not a reverse cycle ´air conditioner’. Would love to see a video on the feasibility of a reverse cycle air conditioner on claiming waste heat from perhaps a hydrogen fuel cell and raising the secondary circuit fluid temperature to possibly drive a gas turbine to generate electricity.
It's effectively an air-cycle heat pump, also called a Joule-Thomson heat pump. It is to the Brayton cycle what mechanical vapor compression refrigeration is to the Rankine cycle. They aren't very efficient, their cooling COPs are usually barely 1, and their heat pump COPs are barely 2. But they can achieve much higher temperatures at tolerable good efficiencies where vapor compression refrigeration completely becomes ineffective.
Very original ! I didn't know this was existing. Thank you ! An interesting connexe topic is flywheels on magnetic bearings (such as what Stornetic does)
Absolutely perfect. Nice subject, all essential parameters of interest covered. Good enough picture quality. Good sound. Keep up the good work. / Joppe
Thank you very much but I am not sure I can agree about the quality of the sound 😂 I nearly sent it to a pro to get rid of some of the background noise, but ran out of time in the end.
@@EngineeringwithRosie A lav mic with a wind sock would have helped a lot. For the noisier areas, a handheld with a wind sock would have been a better choice. You can find cheap versions, but I've personally used Sennheiser Eng kits. (the EW 100 Eng mostly.) They are really handy for recording on anything with a mic /line in option. You only need to add a half decent XLR handheld, which can be fairly cheap to start out with.
I hadn't thought of using electricity to run a heat pump in relationship to thermal storage. Nice boost in efficiency. Still it seems like the capital costs will be very high, since neither rotating equipment nor pressure vessels are cheap.
It strikes me that these explorations of new technology would be a great vehicle for adding a bit of educational material in the spirit of your other technical videos. A great opportunity to add a bit of Carnot, and analyse the efficiency tradeoffs from the standpoint of how theoretical constraints drive the choices of technology, materials, market niche, and the manner in which the designs address these. These guys are able to use a heat pump to add heat - which is already an interesting start. You know this stuff better than me.
I am really not sure how they can use heat pumps for 600C hot air. Normal heat pumps are already pretty bad heating water or air above 60C. They must have a secondary heat source much higher than ambient or geothermal.
@engineering with Rosie. This is a great project and a great idea to make a video about it. The district heating bit is very relevant in Denmark. More than 60% has district heating so there is a lot of demand.
I had district heating when I lived there (I was in Kolding). It was great! But it does need some effort to change it to something other than the waste heat from fossil fuel/ waste power plants as they shut those down.
Wouldn't it make much sense to integrate these with base load thermal power plants that are hard to throttle like nuclear and coal? You would save a lot of energy by skipping on thermal-electricity-thermal transformation. Also the electrical infrastructure is already there, and you could use the existing turbines. Years later when the power plant shuts down, you can just expand the storage.
Considering the goal of these kind of storage is to get things like coal out of the grid, not for that. Nuclear, possibly yeah, that could be interesting.
Have you done, Can you do a report on the technology of the Australian energy stogage startup called 1414 Degrees? They are trying phase change of silicone Thanks
Looks like you've either bought, or copied, my original patent from Isentropic Ltd. The Energy Technology Institute walked off with all the IP when Isentropic closed. Did you buy it from them?
Nice I only knew the medium-scale plant in Hamburg by a Siemens Joint Venture. Haven't heard of it for a while though. If you're here again, can you drop there for a visit? ^^
Good question, but I don't think it is set up in a way that use waste heat. It can supply its waste heat to e.g. district heating though, and get better efficiency that way.
You could use wasteheat to preheat the air thats sucked in the compressor. In this way, you would use some of the energy. A datacenter is likely not a very useful source of wasteheat because of its low temperature level. It would save very little Energy in the charging cycle.
I know of hot rocks &/or hot iron storage (from other shows I've seen) there's one problem that I find difficult. Massive heat sources don't help the atmosphere if the heat insulation isn't highly efficient. Imagine millions of these things around the planet leaking heat. So my question here is how efficient is the insulation mechanism or how much heat is being released?
I don't have numbers, but I guess that it depends on the timescale. The graph at 9:55 suggests that the storage will be useful for up to a week. I don't know which efficiency that corresponds to.
I love your shows, we are working with a company called Raygen who is a solar thermal company but done in a different way mhich might prove interesting for you to cover. We are also based in Australia
Seems similar to Highview power except it's hot instead of cold storage. Similar in they both use mature existing tech. I wonder which is more efficient and more cost effective.
Is this driven by the Windmills? Also what is really interesting is that it has probably a very durability and almost no repair costs over decades. Simplicity and durability is a key factor for success.
My guess, and it's just a guess, is that siting there allows for using the energy from wind turbine dump and diversion loads. The closer to the source the better.
The sand battery has come and stayed. Denmark has stopped various contracts for the wind islands. I think this company has changed course. Definitely interested in hearing if you have any info, but you don't live here anymore so I understand it wouldn't have any live interviews, but Skype would be fine if you could refresh your contact with these companies. Please.
Hvac guy here. This idea has been gnawing at me for some time. What if we were to use refrigerants like r134 and r 404 in pressurised tubing for thermal energy storage.
"I MADE A STEAMPUNK THERMAL ENERGY STORAGE REACTOR IN MY BACK YARD" that would be a good video... Who will be the first crazy RUclipsr to build one... You'd need: 100kg of basalt grit, some way of heating it to 600'C, an old steam engine, and a wind turbine. Sweet video Rosie, that was an edgy interview.
Problems - stones crush in hot/cold cycle. Stones expand in hot, their weight isn’t zero, so them try to deform walls. Crushed stone blocks air passages. Heat insulation works on short time, only. Anyway all heat goes to ambient air. This storage may works on short discharge cycles, on long cycles + efficiency drops dramatically. Li+on seems to be better on longer cycles.
Seems like lots of other battery tech not yet in widespread use, promising adaptation of a Sand Blaster..? The Molten Salt heat storage seems more likely to be useful in Australia, in connection with the present heat generation systems and could buffer load distribution as is proposed for nuke MSRs. (Dare we say more, or is it a submerged issue?)
There I was standing on one of the ancient volcanic plugs that are in Edinburgh (Arthur's seat) thinking it's a pity we don't have a cheap source of basalt where a kilometre toroid of basalt could store enormous amounts of heat.
I wonder why they wouldn't use a material that undergoes a phase change near their target storage temperature? The phase change itself is a massive potential for energy storage.
Do you think this kind of system could be implemented at a fossil fuel powerplant thus switching it from power gen to storage. Reusing the turbine etc Hi from Denmark:)
I think the first step is to use the heat storage as district heating. Gridscale is building a full scale energy storage i Rødby close to a district heating center, so hopefully they can do some experiments.
Competent, comprehensive and detailed, as always with Rosie. One ambiguity that is notorious in the genre (and in here) is the use of the term 'battery'. A battery is an electrochemical device that stores electricity and releases it on demand. The term is used correctly e.g. in the diagram at 9.55. But then the Stiesdal facility is called a 'battery' in the title, when it neither stores electricity, nor electrochemically. So my firewood log store is a battery as well then?
I have to say the presentation did not close the deal with me. It's not obviously out of the question, but there are a few things to realize. First, the efficiency is described at being about 60%. Mr Birkemose promptly adds that the effective efficiency can be higher if you can make use of the waste heat for district hating. But the competition to that configuration is not necessarily a combustion heater, whose efficiency approaches 100%. It may be a heat pump, with an effective efficiency much higher than that. There may be other barriers to using that waste heat, including simply having the original power source too far from population centers. The case for a system like this sounds much like the case for Donald Sadoway's liquid metal battery: For applications where you don't care much about size and weight, its use of very cheap materials, and simple design, may make it worthwhile. That makes sense, at first glance. But the economies of mass-produced batteries, driven by the needs of a couple billion vehicles, may dominate most markets, no matter what anyone does with other designs.
MISTAKE ALERT: They are converting the electricity into "thermal energy" and not "heat". Heat is not a property of a thermodynamic system, but instead only refers to the flow of thermal energy BETWEEN two systems.
I am extremely skeptical of the round trip efficiency claim. I want to know the COP of the heat pump mode, and the thermal efficiency of the gas turbine. The round-trip efficiency can't be greater than its constituent parts. I don't think there is any gas turbine on earth with an efficiency of 60%.
Wow, big question and I could write a whole essay on that! (probably will some time soon 😉). Overall, I think we are going to need less storage than we imagine now, due to energy efficiency and demand flexibility plus we will probably connect electricity grids over longer distances to help smooth variability from renewable electricity generation. For what we do need, I think we will keep all the pumped hydro we have now, and hopefully use it smarter, but probably not add much more. I think lithium-ion batteries will take the majority of the short scale storage needs. Especially when you consider we will probably soon be able to add vehicle to grid storage from electric car batteries. There are several nearly-ready technologies that can fill this medium term storage that the heat battery is aimed at, and I'm not ready yet to make a call on which I think will survive. Probably there will be different tech suited to different locations, so I expect several will survive but probably not everything that is under development now. Thanks for the question, it is an interesting one that got me thinking! What do you think future energy storage will look like?
Nobody knows, but Henrik Stiesdal, founder of this company, is a bit of a guru in renewable energy industry, so this is definately a potential candidate.
@@EngineeringwithRosie There will be great need for fuel for heavy transportation, and there is research to get gas turbines to run using pure hydrogen. The heavy vehicles need a high kW per kg, and hydrogen is better than batteries now. So it looks like hydrogen will make a very good way to store energy for winters. I think green hydrogen will become the bridge fuel for the replacement of fossil fuels.
@@EngineeringwithRosie just a thought on energy storage. Old marine fridges ran the cooling pipes through a eutectic tank. This was so when the main motor was running during a passage the cooling energy could be stored in the eutectic tank while at anchor. This could be added to household fridges With smart electrics to run the compressor while energy is available.
1) Converting solar or wind power first to electricity and then that into heat is not efficient. It would be better to directly convert solar energy into heat. 2) Now with heat pumps, it's clear they have to draw energy from a source outside the house so I wonder now about storing the heat of the warm days into something for later use in in the winter by heat pumps. Imagine a deep huge pit filled with crushed rock and then we pour slightly warm water over it (warmed by the sun) If covered the top layer could still be used for growing crops which hate the cold.
If only technologies like these were possible (economically) on a residential scale for homeowners wishing to disconnect from the grid. Sadly the economies of scale don't allow for it.
I gotta say my favourite grid storage is still the one using liquid air. You can get air anywhere and don't need much material like with these stones here.
1:30 Then why not use water? Water has a *HUGE* heat capacity, it is cheap, easy to get and doesn't cause environmental damage if accidently spilled. On top of everything else, it's easy to clean up.
I've wondered the same thing but I think it's due to lower heat losses. When storing heat in a solid material that has low heat conductivity, the outer layers will act as insulation for the hot interior. If you use a liquid on the other hand, convection will make sure that all the liquid ends up at the same temperature and thereby require greater tank insulation to keep the heat losses down. EDIT: The main reason though, that I completely forgot about when I wrote the text above, must be that you can't store water at a particularly high temperature. That greatly limits the efficiency when you're trying to extract the energy again.
You can't use water over 100C without going for a high pressure system, like in nuclear reactors. That adds an retarded amount of cost and would destroy the whole building in case of a "spill". Heat energy storage volume is proportional to heat capacity of the material and temperature difference. So rocks that only have half the heat capacity of water can still store 3 times more energy in the same volume than liquid water because you have 6 times higher temperature difference.
Basically it's a giant twin walled vacuum flask with a load of thermal bricks in core with heating elements People back in day had storage heaters and they were awful they cost a fortune to run they were not financially viable to keep running at all
@@EngineeringwithRosie I think any kit will be a springboard for you to develop something far more interesting. But I'm glad to see you have taken a interest in the creative fun of it all, enjoy!
@@EngineeringwithRosie I may end up getting a giant bottle of superglue soon, most of my model's failures are due to winds that are to strong for the snap together plastic. Kinda like a jigsaw puzzle, once ya have it figured out, ya glue it for the picture and the accomplishment.
You need to do a better sound preparation for your interviews. It is hard to understand your interviewees because of the room that you are interviewing in. Better microphones better soundproofing interview room. You might need to repeat whatever the your interviewee is saying so that the audience is clear on what he said
Yep, I have been working hard on my audio quality in the year since I filmed that but onsite interviews are still a challenge! I always upload good quality subtitles so if you're having trouble understanding you can try turning those on. Thanks for the feedback!
Thank you for the great content! I hope this doesn’t come through as mansplaining but I would recommend using a lavalier mic, or the tiles from Rode into something like Zoom H4n as a cost-effective way. Decrease mic distance to sound source -> better direct vs. reverberant field ratio -> less prominent room modes in the signal.
Off course energy create is necessity individual consumption have minimise government has many public vehicales those are correct now Every country can follow same solution after pendamic
Very fascinating how so much of tech around finally boils down to the role of material science. Thanks for sharing.
Yep, you are right about that. Materials science is really important to most technologies.
Or maybe thinking outside the "CORPORATE" box.
Nice to see a video on this technology!
Compared to other types of longer term energy storage, I can see two big advantages to this that I don't think I've seen mentioned anywhere. The first is the potential to very cheaply add lots of extra charging power on top of the heat pump using simple resistive heating. That should be useful during infrequent periods of very low, or even negative, electricity prices where you just want to charge as much as possible no matter the efficiency.
The second is that since this system is based on heat, it should be cheap to add a "deep backup" option were you simply provide the heat from stored chemical fuels once the heat storage is empty. The efficiency would be low, but I think it would be very useful for grids primarily based on wind power since it could hold you over through the very rare periods of multiple weeks of low wind. That would then save you from having to invest in a completely separate backup system based on gas turbines or the like.
Not usually commenting but just found out your channel, content is amazing. You provide all the necessary information. Well structured, detailled and with schemas. So hard to find these information elsewhere. Thanks for your work!
Thanks for running this channel and especially covering this storage solution. I believe Thermal storage is going to be a big part of the solutions during the energy transition world-over, especially because it will be relatively cheap. I had a quick question, I was looking for the study at 9:57, is it available for people to view/read and learn more?
Thanks for your comment. That is a slide that was given to me by Henrik Stiesdal, the founder of the company, and I don't have any more info than that. BUT like you, I think energy storage duration is a very interesting and important topic, so I am planning a video on that soon. When I make that video, I will include reference material where you can learn more.
That was great Rosie. It really fleshed out visually what Dave at 'Just have a think' went into in some detail. Keep up the good work.
Sent here via let’s have a think. Great interview and tour, would love to see other interviews with new grid technology providers. Thanks!
Interesting to see the step through of how it functions. Looking forward to seeing them grow and become a standard part of utility scale as well as independent grid solutions. Great to see the simple technology become even more appealing in tandem with solar and wind.
Very interesting 👌. I think another important factor in increasing the efficiency and decreasing overall product cost is to use it near the onshore wind farms, using the storage material available in that area (less transportation cost) and integrating it with the nearby residential community's or any other necessity's, heating and cooling needs (by product from loss energy at charging and discharging)
Totally agree!
@@EngineeringwithRosie the other possibility is to site near large low grade heat users such as food industry or glasshouse growers to use the low temp waste heat.
Nice Video. I think this combined with batteries will be the energy storage of the future.
Also nice Siemens D3 turbine in the background at 10:48
Yes, in Denmark you are never far away from a wind turbine 😂 And this location was quite near the Siemens wind HQ.
One metric that I didn't see raised was what is the daily/hourly heat loss of the system? Even if it is only targeted at daily cycling that would be interesting to know.
The algorithm thanks you and so do I!
Thank you so much for this tour! This system and compressed air system, if they indeed have 60% efficiency and are 10-100 cheaper than chemical batteries, seem to be very suitable right now for energy transition. Because I don’t see any progress in the pace of installation of small and midsize storage systems anywhere in the world.
Let’s take Germany as an example. Germany added only 5 GWh of batteries last year, which is a staggeringly slow pace compared to the goal of 5 TWh defined in Tony Seba’s report for Germany. (For entire power of the country 10 TWh of batteries are needed.) At the current MegaPack price of 270 USD/kWh + installation etc. costs Germany would need to spend 2 trillion dollars over 10-15 years only for these 5 TWh of batteries, which is 40% its GDP! And these batteries have a roundtrip efficiency of 87%, which is not too far from 60%. The question now is how much does Stiesdal system cost if mass produced? If it is 10 USD/kWh we all should start a campaign of advocating and informing the governments.
This type of storage should also be suitable for “tankering”. In his paper “Rethinking Energy (2022). Germany's Path to 'Freedom Energy' by 2030” Tony Seba suggests for Germany to install 5 billion kWh of batteries (5 TWh) during 10-15 years, which is equivalent of 3.5 days of all electricity needs (1.4 TWh per day). In case of a 2-week winter Dunkelflaute, common to northern countries, the country will cover only 3.5 days via batteries. I suppose that the remaining 10.5 days can be covered via international fleet of tankers full of batteries: 4 tankers each day, 32 tankers in total for a region size of Germany (4 on recharging, 4*3 + 4*3 on a 3-day long trip to/from Africa, 4 on discharging), but for all regions simultaneously in trouble the number of tankers obviously must be larger.
Thanks for the tour. I prefer the sodium acetate as a storage of heat. Then you can add water back as needed to give the year up. The advantage is the long term storage for heat. The disadvantage is the size necessary and cost of material.
Great tip! It's not something I have looked into before.
Nice video! Thank you for introducing this technology!
I agree with the idea that you need to disconnect the costs of charging, discharging, and storage equipment in order to enable longer-term storage capabilities by minimizing the third component (storage). But often these types of technologies are presented in a vacuum relative to other competitors. The gentleman interviewed mentioned the primary drawback of batteries (cost), but he did not mention the benefits of batteries (efficiency and response time, for instance) nor did he talk about the more direct competitors to his product. In this space, hydrogen is another player which will have benefits and drawbacks and another notable technology is Advanced Rail Energy Storage (ARES). He also did not cover important drawbacks, such as the fact that such a large amount of waste heat may NOT have much utility in summertime except in specific industrial application.
In order for this technology to find at least a single market in which to play, it needs to beat ALL other comers, not just batteries. The important figures of merit that come to mind immediately are:
- efficiency (both one-way and round-trip since technologies like this one and hydrogen have differences on charge and discharge)
- cost (of the various components)
- size (floorspace or volume, whichever is important for potential applications)
- durability (life)
- energy lost in storage over time
- energy storage horizon (What is the shortest and longest amount of time that this technology can be reasonably applied to store energy? Seconds, minutes, hours, one day, several days, a week, several weeks, months?)
- environmental impacts
The point is that we need longer-term storage technologies like this or hydrogen or ARES (or others or all of the above) that can make one week or longer storage an affordable reality, but they all have their benefits and drawbacks. I would be interested in a survey of prospective technologies in this long-term storage space. If you want to address the VALUE side of the renewables equation, that is perhaps the biggest hurdle.
Thanks for these comments, all good points. I am working on a video about energy storage duration, and I could include long-term energy storage techs in that video. Thanks for the suggestions!
@@EngineeringwithRosie TIA!
Couldn't waste heat be used in absorption chillers ?
Thanks, Rosie. Can you explain how a compressor acts as a heat pump here? I get that it heats the gas (by T = PV/nR and perhaps compressor inefficiency), but their website claims the COP to be 2.5 and you don't get that without a refrigerant and an evaporator & condenser combo.
It’s pumping the heat from the cold storage tank to the hot tank, the turbine acts as the evaporator
@@iain3713 - Hmm. That doesn't seem right. The turbine is playing the part of the compressor, which is already part of a true heat pump system. If it's a heat pump, you need *both* an evaporator and a compressor - and the evaporator facilitates heat transfer via phase change, which at this temperature is impossible to happen to air. Most importantly, a heat pump's purpose is to move heat, whereas this device's purpose is to convert electricity into heat and pressure. The movement of gas from the cold reservoir into the hot reservoir is helpful for facilitating that electricity conversion, but it's an entirely different type of concept. Keep in mind also that heat pumps are meant to work to move heat from an *open* system (i.e., not insulated) into a place where you want to warm things up. You can keep moving more heat because of the openness of the cold reservoir. In this device, the cold reservoir is insulated; if you move heat from it to elsewhere, no new energy enters the system. In fact, the most telling difference between this system and a heat pump is that a true heat pump would be cooling down the cold reservoir by the fact that it removes heat, but in this system any cooling down that occurs happens because you're pumping in cold air from the bottom. The system removes air from the system, and some heat goes along with the air, but if they weren't pumping in cold air at the bottom the temperature of the cold reservoir would *not* change ... all that would happen is that the rocks would stay at the same temperature but would now be in a partial vacuum.
(For reference: energyeducation.ca/encyclopedia/Heat_pump)
@@rasraster I may be looking at it wrong, but air gets compressed to above the temperature of the hot storage tank, transfers some heat to the storage tank, it expands through the turbine, doing work so it loses heat and cools down below the temperature of the cold tank, absorbs heat from that and cycle repeats.
It sounds like the compressor is being used as in a gas turbine to feed air into the system to drive the system in a particular direction. If the air is at higher pressure at the cold end, the heated exhaust gas will flow towards the turbine end of the system. A smaller pressure applied over a larger area or ar a distance further from the drive shaft than the compressor blades results in greater torque in the direction that they want the system to flow.
@@rasraster I'm having a hard time understanding it too. Most Joule-Thomson (air cycle) refrigeration machines I've heard of had a COP less than unity, which would leave a COP of less than 2 as a heat pump (generous, because most actual heat pump applications require a larger temperature difference and lower efficiency than when operating as refrigeration, especially in this case). One thing to remember is that air cycle machines can be open cycle, they don't necessarily have to have both a corresponding "condenser" or "evaporator" (gas heater, gas cooler). The only issue is that when operating open cycle as refrigeration, ice tends to form in the expansion device (usually a turboexpander to help with the already low efficiency).
What gets me excited about this is how the cost scales so beneficially with storage capacity. Probably for installations with a large capacity but relatively low rating is dominated by the cost of the steel tank rather than the storage medium, which means you have the cube-square law on your side. And then if you want to increase the rating, I guess you just need to get a larger turbine system, so you just pay proportionally for that. Thanks for this!
This seems similar to liquid air storage in it's efficiency, and also in that adding capacity is cheap. Also siting is much easier than pumped hydro, and I assume this should be fast to build.
Doesn't liquid air use something like this too? To capture some of the heat generated when cooling the air, then to use that heat to expand the cooled air later?
Great video! It is now two years old. It would be interesting to make follow-up videos for this type of content after 2-5 years. Is the company still around? Do they sell their system at some scale? Are there other companies doing similar things with the same technology?
Best graphics ever! 😃. I love your videos, can I suggest a wireless microphone? Thanks, and keep producing this excellent content.
Understand the terminology used here as heat pump refers to a compressor and not a reverse cycle ´air conditioner’. Would love to see a video on the feasibility of a reverse cycle air conditioner on claiming waste heat from perhaps a hydrogen fuel cell and raising the secondary circuit fluid temperature to possibly drive a gas turbine to generate electricity.
Yes, domestic heat pumps only work efficiently with a low temperature output. This must be something very different, needs more explanation
It's effectively an air-cycle heat pump, also called a Joule-Thomson heat pump. It is to the Brayton cycle what mechanical vapor compression refrigeration is to the Rankine cycle. They aren't very efficient, their cooling COPs are usually barely 1, and their heat pump COPs are barely 2. But they can achieve much higher temperatures at tolerable good efficiencies where vapor compression refrigeration completely becomes ineffective.
Very original ! I didn't know this was existing. Thank you !
An interesting connexe topic is flywheels on magnetic bearings (such as what Stornetic does)
Absolutely perfect. Nice subject, all essential parameters of interest covered. Good enough picture quality. Good sound. Keep up the good work. / Joppe
Thank you very much but I am not sure I can agree about the quality of the sound 😂 I nearly sent it to a pro to get rid of some of the background noise, but ran out of time in the end.
@@EngineeringwithRosie A lav mic with a wind sock would have helped a lot. For the noisier areas, a handheld with a wind sock would have been a better choice. You can find cheap versions, but I've personally used Sennheiser Eng kits. (the EW 100 Eng mostly.) They are really handy for recording on anything with a mic /line in option. You only need to add a half decent XLR handheld, which can be fairly cheap to start out with.
I hadn't thought of using electricity to run a heat pump in relationship to thermal storage. Nice boost in efficiency. Still it seems like the capital costs will be very high, since neither rotating equipment nor pressure vessels are cheap.
It strikes me that these explorations of new technology would be a great vehicle for adding a bit of educational material in the spirit of your other technical videos. A great opportunity to add a bit of Carnot, and analyse the efficiency tradeoffs from the standpoint of how theoretical constraints drive the choices of technology, materials, market niche, and the manner in which the designs address these. These guys are able to use a heat pump to add heat - which is already an interesting start. You know this stuff better than me.
I am really not sure how they can use heat pumps for 600C hot air. Normal heat pumps are already pretty bad heating water or air above 60C. They must have a secondary heat source much higher than ambient or geothermal.
@@Psi-Storm That depends on the working fluid (gas) and the pressure (compression) ratio, very high temps are possible.
@engineering with Rosie. This is a great project and a great idea to make a video about it. The district heating bit is very relevant in Denmark. More than 60% has district heating so there is a lot of demand.
I had district heating when I lived there (I was in Kolding). It was great! But it does need some effort to change it to something other than the waste heat from fossil fuel/ waste power plants as they shut those down.
@@EngineeringwithRosie True it's a big job, but the pipes are there.
Wouldn't it make much sense to integrate these with base load thermal power plants that are hard to throttle like nuclear and coal? You would save a lot of energy by skipping on thermal-electricity-thermal transformation. Also the electrical infrastructure is already there, and you could use the existing turbines. Years later when the power plant shuts down, you can just expand the storage.
Considering the goal of these kind of storage is to get things like coal out of the grid, not for that. Nuclear, possibly yeah, that could be interesting.
Nice video
Not that long since I saw this being tested by DTU so it's neat to see that it's already being tested by a company.
It has been a super fast development, hasn't it?! That's what you can do when you keep things simple.
Rosie. How do think this compares with liquid air energy storage? It seems to be in the same performance domain.
Have you done, Can you do a report on the technology of the Australian energy stogage startup called 1414 Degrees?
They are trying phase change of silicone
Thanks
Nice one a practical, in thermal storage of energy.
Looks like you've either bought, or copied, my original patent from Isentropic Ltd. The Energy Technology Institute walked off with all the IP when Isentropic closed. Did you buy it from them?
It looks like a simple structure. Is it functional? and any demonstration project in the future?
Can you do a video about vanadium redox flow batteries?
How do they get the heat into the sand ? Must be a dry or wet system?
Nice I only knew the medium-scale plant in Hamburg by a Siemens Joint Venture. Haven't heard of it for a while though. If you're here again, can you drop there for a visit? ^^
Could this machine also make use of “waste” heat from i.e. Datacenters?
Good question, but I don't think it is set up in a way that use waste heat. It can supply its waste heat to e.g. district heating though, and get better efficiency that way.
You could use wasteheat to preheat the air thats sucked in the compressor. In this way, you would use some of the energy. A datacenter is likely not a very useful source of wasteheat because of its low temperature level. It would save very little Energy in the charging cycle.
I read the title and immediately assumed that it'd be a molten salt solution but this is completely new for me, seems like a simpler thing.
It was the simplicity that appealed to me too. I do plan to do a video on molten salt in the future too.
@@EngineeringwithRosie Waiting for engineers take on Solar Thermal projects..lot of videos but most of them barely touch real details.
I would like to see you do a video on plasma gasification for waste disposal.
I know of hot rocks &/or hot iron storage (from other shows I've seen) there's one problem that I find difficult. Massive heat sources don't help the atmosphere if the heat insulation isn't highly efficient. Imagine millions of these things around the planet leaking heat. So my question here is how efficient is the insulation mechanism or how much heat is being released?
I don't have numbers, but I guess that it depends on the timescale. The graph at 9:55 suggests that the storage will be useful for up to a week. I don't know which efficiency that corresponds to.
А чи не попробувати плюмбум замість каміння. Додаткова теплоємність зарахунок фазового переходу, точка плавлення.
I love your shows, we are working with a company called Raygen who is a solar thermal company but done in a different way mhich might prove interesting for you to cover. We are also based in Australia
I have plans to cover solar thermal, so I will check them out. Thanks!
@@EngineeringwithRosie If you need to contact Raygen email myself on manuel.cilia@photonenergy.com or michael.gartner@photonenergy.com
Seems similar to Highview power except it's hot instead of cold storage. Similar in they both use mature existing tech. I wonder which is more efficient and more cost effective.
There is a company called Azelio which also uses thermal storage pods and stirling motors. Could you do a similar video about that?
Is this driven by the Windmills? Also what is really interesting is that it has probably a very durability and almost no repair costs over decades. Simplicity and durability is a key factor for success.
My guess, and it's just a guess, is that siting there allows for using the energy from wind turbine dump and diversion loads. The closer to the source the better.
Would be interesting if this can also use process heat, I.e. what the minimum input temperature is.
Maybe the SaltX solution is better for this.
Amazing simple technology. I wonder how can we contact this company? I may have a proposal for them.
The sand battery has come and stayed. Denmark has stopped various contracts for the wind islands. I think this company has changed course. Definitely interested in hearing if you have any info, but you don't live here anymore so I understand it wouldn't have any live interviews, but Skype would be fine if you could refresh your contact with these companies. Please.
Hvac guy here. This idea has been gnawing at me for some time. What if we were to use refrigerants like r134 and r 404 in pressurised tubing for thermal energy storage.
Would that be preventing energy loss to get higher than 60% efficiency?
"I MADE A STEAMPUNK THERMAL ENERGY STORAGE REACTOR IN MY BACK YARD" that would be a good video... Who will be the first crazy RUclipsr to build one... You'd need: 100kg of basalt grit, some way of heating it to 600'C, an old steam engine, and a wind turbine. Sweet video Rosie, that was an edgy interview.
Problems - stones crush in hot/cold cycle. Stones expand in hot, their weight isn’t zero, so them try to deform walls. Crushed stone blocks air passages.
Heat insulation works on short time, only. Anyway all heat goes to ambient air. This storage may works on short discharge cycles, on long cycles + efficiency drops dramatically. Li+on seems to be better on longer cycles.
great job and thanks
Seems like lots of other battery tech not yet in widespread use, promising adaptation of a Sand Blaster..?
The Molten Salt heat storage seems more likely to be useful in Australia, in connection with the present heat generation systems and could buffer load distribution as is proposed for nuke MSRs. (Dare we say more, or is it a submerged issue?)
>90% RTE. That's *VERY* impressive. Intereting video!
using the waste heat for heating does wonders
just in general, not just for this tech
Thanks 👍
Is there a design for small off grid system? Like a small off grid home.
Not from this company but there are small thermal storage systems available for domestic use.
Thanks 🙏!!!!
There I was standing on one of the ancient volcanic plugs that are in Edinburgh (Arthur's seat) thinking it's a pity we don't have a cheap source of basalt where a kilometre toroid of basalt could store enormous amounts of heat.
I wonder why they wouldn't use a material that undergoes a phase change near their target storage temperature? The phase change itself is a massive potential for energy storage.
Great stuff, thank you
A crazy idea it sounds, but if it works, it works!
What kind of temperatures do they need for the system to work?
The hot side is 650 degree celsius and the cold side is -30 degree celsius. So a differential of 680 degrees
So what does this cost for 1 tank system
Do you think this kind of system could be implemented at a fossil fuel powerplant thus switching it from power gen to storage. Reusing the turbine etc
Hi from Denmark:)
I think the first step is to use the heat storage as district heating. Gridscale is building a full scale energy storage i Rødby close to a district heating center, so hopefully they can do some experiments.
Why vertical towers? Wouldn't they be cheaper lying down?
Competent, comprehensive and detailed, as always with Rosie. One ambiguity that is notorious in the genre (and in here) is the use of the term 'battery'. A battery is an electrochemical device that stores electricity and releases it on demand. The term is used correctly e.g. in the diagram at 9.55. But then the Stiesdal facility is called a 'battery' in the title, when it neither stores electricity, nor electrochemically. So my firewood log store is a battery as well then?
If you can make more firewood with electricity and release it on demand, then probably.
@@Psi-Storm Is that kind of circular capability necessary?
I have to say the presentation did not close the deal with me. It's not obviously out of the question, but there are a few things to realize. First, the efficiency is described at being about 60%. Mr Birkemose promptly adds that the effective efficiency can be higher if you can make use of the waste heat for district hating. But the competition to that configuration is not necessarily a combustion heater, whose efficiency approaches 100%. It may be a heat pump, with an effective efficiency much higher than that. There may be other barriers to using that waste heat, including simply having the original power source too far from population centers.
The case for a system like this sounds much like the case for Donald Sadoway's liquid metal battery: For applications where you don't care much about size and weight, its use of very cheap materials, and simple design, may make it worthwhile. That makes sense, at first glance. But the economies of mass-produced batteries, driven by the needs of a couple billion vehicles, may dominate most markets, no matter what anyone does with other designs.
Why can you not design a system for domestic use +- 8kw , I bet it would be cheaper to sell
You can already buy a bunch of hot water tanks. However, they can store the heat for only 3 to 4 days because of their small size (square cube law)
Some good microphones to the next video would not hurt. I need full volume to hear what is said.
I couldnt find the part where he said what storage medium TLDR
There are bookmarks in the description. Try this one: 06:40 What material is the heat stored in?
is this the one that uses molten silicon @1500c?
No, it's small rocks and they don't melt.
@@EngineeringwithRosie Thanks Rosie :)
im wonder how the hot air turbine works to convert hot air to electric energy, and for this machine efficiency,
MISTAKE ALERT: They are converting the electricity into "thermal energy" and not "heat". Heat is not a property of a thermodynamic system, but instead only refers to the flow of thermal energy BETWEEN two systems.
If he can achieve 60% cycle efficiency so easily why the thermal power plants are not using similar technology?
Thermal power plants either has a significantly lower outlet temperature, or they lose energy with the combustion products.
I am extremely skeptical of the round trip efficiency claim. I want to know the COP of the heat pump mode, and the thermal efficiency of the gas turbine. The round-trip efficiency can't be greater than its constituent parts. I don't think there is any gas turbine on earth with an efficiency of 60%.
Isn't that what a CCGT does?
Which of these technologies do you think will dominant in the future ?
Wow, big question and I could write a whole essay on that! (probably will some time soon 😉). Overall, I think we are going to need less storage than we imagine now, due to energy efficiency and demand flexibility plus we will probably connect electricity grids over longer distances to help smooth variability from renewable electricity generation. For what we do need, I think we will keep all the pumped hydro we have now, and hopefully use it smarter, but probably not add much more. I think lithium-ion batteries will take the majority of the short scale storage needs. Especially when you consider we will probably soon be able to add vehicle to grid storage from electric car batteries. There are several nearly-ready technologies that can fill this medium term storage that the heat battery is aimed at, and I'm not ready yet to make a call on which I think will survive. Probably there will be different tech suited to different locations, so I expect several will survive but probably not everything that is under development now.
Thanks for the question, it is an interesting one that got me thinking! What do you think future energy storage will look like?
Nobody knows, but Henrik Stiesdal, founder of this company, is a bit of a guru in renewable energy industry, so this is definately a potential candidate.
@@EngineeringwithRosie
There will be great need for fuel for heavy transportation, and there is research to get gas turbines to run using pure hydrogen. The heavy vehicles need a high kW per kg, and hydrogen is better than batteries now. So it looks like hydrogen will make a very good way to store energy for winters. I think green hydrogen will become the bridge fuel for the replacement of fossil fuels.
@@EngineeringwithRosie just a thought on energy storage. Old marine fridges ran the cooling pipes through a eutectic tank. This was so when the main motor was running during a passage the cooling energy could be stored in the eutectic tank while at anchor.
This could be added to household fridges With smart electrics to run the compressor while energy is available.
I was hooked from the beginning, but now I'm starting to wonder if this guy even owns a black leather couch.
what does "mature components" mean? the opposite of experimental?
Mature means the technologies are not bleeding edge; they have been around for a long time and are fully developed.
1) Converting solar or wind power first to electricity and then that into heat is not efficient. It would be better to directly convert solar energy into heat. 2) Now with heat pumps, it's clear they have to draw energy from a source outside the house so I wonder now about storing the heat of the warm days into something for later use in in the winter by heat pumps. Imagine a deep huge pit filled with crushed rock and then we pour slightly warm water over it (warmed by the sun) If covered the top layer could still be used for growing crops which hate the cold.
If only technologies like these were possible (economically) on a residential scale for homeowners wishing to disconnect from the grid. Sadly the economies of scale don't allow for it.
I gotta say my favourite grid storage is still the one using liquid air. You can get air anywhere and don't need much material like with these stones here.
did I miss the efficiency?
60 %
excellent
What time is it there
Right now it is 9:47
Please enable the subtitles
Pragmatic 😎
quite similar thinking here to Malta inc
1:30 Then why not use water? Water has a *HUGE* heat capacity, it is cheap, easy to get and doesn't cause environmental damage if accidently spilled. On top of everything else, it's easy to clean up.
I've wondered the same thing but I think it's due to lower heat losses. When storing heat in a solid material that has low heat conductivity, the outer layers will act as insulation for the hot interior. If you use a liquid on the other hand, convection will make sure that all the liquid ends up at the same temperature and thereby require greater tank insulation to keep the heat losses down.
EDIT:
The main reason though, that I completely forgot about when I wrote the text above, must be that you can't store water at a particularly high temperature. That greatly limits the efficiency when you're trying to extract the energy again.
Because water would turn into steam
You can't use water over 100C without going for a high pressure system, like in nuclear reactors. That adds an retarded amount of cost and would destroy the whole building in case of a "spill". Heat energy storage volume is proportional to heat capacity of the material and temperature difference. So rocks that only have half the heat capacity of water can still store 3 times more energy in the same volume than liquid water because you have 6 times higher temperature difference.
Basically it's a giant twin walled vacuum flask with a load of thermal bricks in core with heating elements
People back in day had storage heaters and they were awful they cost a fortune to run they were not financially viable to keep running at all
Concrete in lue of steel tank ? Tank created by drilling in bedrock ?
Interesting
Nice, no rare earth materials, very little waste when system is retired, non-toxic.
Van anybidy explain in kayman language what is happening here?
They use an electric heatpump to heat up rocks in a tank and then they use the heat to drive a turbine to generate electricity.
@@EngineeringwithRosie thanks 😊
1. What is the efficiency of the system?
2. The electricty used is green?
@@ibraheemali9541 The efficiency is 60 %, and you can use green electricity produced by solar cells or wind power.
@@Terascon anahan good thanks 😊
Came here from Just have a think.
Didn’t see any actual ‘workings’ of this simple principle ☹️
Why don't they make it more spherical?
Turkish Hot Sand Coffee Brewer with the Copper Cezve Ibrik.
Please cover liquid CO2 batteries. They claim to be 80 percent efficient!
Seems like a lot of extra steps and high loss of efficiency. Large scale capacitors would be the most efficient and keep the electricity ready to use.
Capacitors are not high enough kW per kg. Batteries are much higher.
Even when cost is factored in?
@@acmefixer1 What are the most energy dense without using rare-earth materials?
Lol@wind farm Lego's ~ K'nex !
I am very keen to get my hands on this Lego kit! Though these kinds of Lego kits aren't as creative as your K'nex adventures 😊
@@EngineeringwithRosie I think any kit will be a springboard for you to develop something far more interesting. But I'm glad to see you have taken a interest in the creative fun of it all, enjoy!
@@EngineeringwithRosie I may end up getting a giant bottle of superglue soon, most of my model's failures are due to winds that are to strong for the snap together plastic. Kinda like a jigsaw puzzle, once ya have it figured out, ya glue it for the picture and the accomplishment.
@@doktaahwho8858 get the Cragle out 😂 (I assume you saw the Lego movie... if not you may need help understanding that)
@@EngineeringwithRosie Sadly I have not seen it. So, ????
You need to do a better sound preparation for your interviews. It is hard to understand your interviewees because of the room that you are interviewing in. Better microphones better soundproofing interview room. You might need to repeat whatever the your interviewee is saying so that the audience is clear on what he said
Yep, I have been working hard on my audio quality in the year since I filmed that but onsite interviews are still a challenge! I always upload good quality subtitles so if you're having trouble understanding you can try turning those on. Thanks for the feedback!
Thank you for the great content! I hope this doesn’t come through as mansplaining but I would recommend using a lavalier mic, or the tiles from Rode into something like Zoom H4n as a cost-effective way. Decrease mic distance to sound source -> better direct vs. reverberant field ratio -> less prominent room modes in the signal.
Off course energy create is necessity individual consumption have minimise government has many public vehicales those are correct now
Every country can follow same solution after pendamic