Gravity Energy Storage(중력 배터리). Who's right and Who's wrong ?

Subject : Gravity Energy Storage. Who's right and Who's wrong ?

Back in January last year I made a video looking at the concept of gravity energy storage. You may remember me showing you a group of design students who setup a nice little demo on a very high building that generated enough electrical energy to run a recode turntable. Clever stuff! Back then I focused on two companies who were developing their own different interpretations of gravity energy storage at utility grid scale. One of them was the Swiss-based company Energy Vault, whose massive open-air tower and multiple crane design got quite badly panned at the time by some well-known YouTube debunking channels. The other company was an Edinburgh based outfit called Gravitricity. They were pursuing a very different road to achieving a gravity energy storage system, opting for a much safer more stable and predictable system that involves lowering massive weights into decommissioned mine shafts. Now, one of the requests i get quite often for you good folks out there is for me to occasionally revisit technologies that i've featured in past videos to check out what progress they've been making. So, one year down the line from that original video, i thought now was as good a time as any to take another look.
Hello and welcome to just have a think. This whole using gravity to store energy thing is a pretty good idea in princple.In fact we've effectively already been doing it for more than 100 years with pumped hydro facilities that make use of reservoirs of water at different heights, when power is required. The trouble is those facillities are quite expensive to build and of course you need the right geographical conditions to make them work so they're not something you can course you need the right geographical conditons to make them work so they're not something you can simply replicate all over the world. Energy Volt's original concept was this massive freestanding tower on top of which they planned to bolt about five cranes that could winch great 30 ton weights up and down depending on whether there was a surplus or deficit of energy on the electricity grid. Now i'm not going to get into the weeds of why some commentators were so critical of this system. I'll let you go and find those debunkers yourself on YouTube and other social media platforms. Suffice to say there were some very significant questions of physics that appeared not to have been addressed, like the fact that all the blocks at the bottom of the pile possessed precisedly zero potential energy because they were already sitting on the floor. Plus the perfectly reasonable observation that lt'd be quite tricky to stop a 30 ton weight wandering off the vertical on a windy day, which would not only mess up the synchronization of the system but also put untold stresses and strains on the tower structure itself. Energy Vault now appears to have moved away from that original design concept and pivoted towards this new idea which they tell us is the Energy Vault Resiliency Center or EVRC. It's a warehouse style building about the size of a very large football stadium housing hundreds of multi-storey racking systems carrying 30 tonne blocks in each location all of which will apparently get lifted dropped and shounted from side to side by a complex network of computer controlled pulleys and casters. Now that is a heck of a construction project! But Energy Volt aren't stopping there. They reckon this facility is a modular design that can be built out into even larger configurations, presumably eventually reaching this size of a small town ! Now of course this video was not filmed at a real world construction site. It is in fact a computer-generated rendering of what such a football stadium-sized facility would look like - you can tell by the little white blobby trees in the background. Eh ? No files on me ! So as far as I know such a building has not yet been created anywhere in the world and Energy Vault are still at concept stage. I must admit it does look like an awful lot of expensve infrastructure maintenance over the long haul. So I think I'll let you make your own mind up about this one, and maybe I'll have another little rummage around at some point in 2023 to see if the company has actually broken ground anywhere int the world. In the meantime, a very different company with a very different approach to harnessing the advantages of a gravity energy storage system is Gravitricity in Edinburgh who I mentioned at the start of the video. I caught up with their MD, Charlie Blar, via Zoom recently to help with my understanding of how Gravaticity differs from Energy Vault and to get the latest news on how their concept is progressing. Arguably the most fundamental difference between the two concepts is that Gravitricity believe that, outside of pumped hydro, the only serious way to achieve safe, reliable, dispatchable grid-scale gravity energy storage is to use the geology of the earth. One of the most compelling arguments for this approach is that instead of building a massive warehouse with miles and miles of steel support structures inside you can simply use the planet to hold up your weight. After all, that's precisely what a pumped hydro system does isn't it ? Now, just to really confuse the issue, the first demo structure that Gravitricity built back in 2021 w was a steel frame tower above ground. So what was all that about then ? Well Charlie explained that it was a simple matter of making things as easy as possible for the test rig so that all the mechanical elements could be simply monitored and viewed by the engineers. The tower only needed to be quite small compared to a full-size configuration too. The rig was essentially built to assess the dynamic behaviour of the weight during the stop start phases of the system and specifically the speed of response that the system could achieve as gravity competed with inertia to get that weight moving. That sord of test data is absolutely crucial for any device providing grid frequency requlation. Engineering simulations showed that the system would operature within acceptable parameters, so the test rig was there to validate those results. And happily for Gravitricity, validate them it did ! The concept demo uses a naturally high density iron ore aggregate derived from magnetite. At full scale each weight will be around 500 tons so having it in lots of small pieces rather than one big solid lump obviously makes it infinitely more manageable for transport, as well as on-site handing and maintenance and even for decommissioning at the end of the facility's operational lifetime. The winches and motor generator systems that allow the weights to be gently lowered and raised work on very similar principles to the regen braking system in an electric vehicle which harnesses the energy that would otherwise be wasted as the vehicle slows down or goes down a hill. Except of course in this case the energy is going directly into the grid rather than into a battery. The core elements of the system like the shafts and the weights and the structural elements holding the winches and motor generators all have projected operational lifetimes of more than 50 years. The cables are good for 75,000 cycles which is about 10 times the number of cycles that a typical battery can manage. At full scale the shaft depth will be between 300 and 500 metres and the containers of iron ore will be between three and five metres in diameter and perhaps four or five metres deep. The system is designed to be extremely versatile in terms of duration of discharge. It can be used for anything from instant response frequency regulation with a signle weight system in an existing mine shaft, right up to long duration discharge times of between two and eight hours in purpose-built multiple weight configurations to complement solar power and to provide extra electricity for peak hours of the day. Now, the question many of you quite rightly ask me about any of the energy storage systems I look at on the channel is what's the levelized cost of storage or LCOS ? And the answer to that question is it depends on which variables and paremeters you put into the calculation. Gravitricity commissioned imperial College London to assess their system, and the parameters they input look like this for a storage system with a discharge time of two to six hours. For a 24.4 megawatt hour system cycling 730 times a year for 25 years the Gravitricity system stackes up very favourably indeed, not just against lithium-ion batteries but also against a range of other energy storage options currently available. The next step for Gravitricity will be to assess different locations all over the world to establish which ones are suitable for this kind of system. And there'll be no shortage of options. The European Union is keen to accelerate coal mine closures as part of its REpowerEU initiative, and it obviously makes sense to look for ways to do something useful with those decommissioned facilities. In fact, Gravitricity is already in contact with mine owners in countries like the Czech Republic and Poland and similar opportunities exist in North and South America and in Africa. Having derived very positive data from their proof of concept tower up in Scotland, Gravitricity are now in the early stages of an 18-month engineering design phase for their first full-size fully operational facility. Once that work has been done and the location somewhere like 2025 or 26. After that though the turnaround time for subsequent projects is likely to be relatively quick. So there you have it folks. A progress report as promised. I guess what it shows is it's bloody hard work to get from design concept to a real world commerical operation. Gravitricity are a pretty pragmatic and realistic team of predominantly engineering types who understand that there are no shortcuts and no amount of slick marketing will make the process move any faster. But their system does look like it could serve a very useful purpose in a very large number of otherwise useless and redundant locations all over the world, and if it can achieve that then it really will be offering a meaningful contribution to the sustainable energy transition. Now, you're probably chomping at the bit to voice your opinion on this one, so by all means jump down to the comment section below and leave your thoughts there. Keep it civil though, eh ? That's it for this week. A massive thank you, as always, to our fantasic Patreon supporters who keep these videos completely independent and ad free.

 

Gravitricity는 폐광의 깊은 갱도에 중량물을 저장하고 전력이 필요할 때 중량물을 위로 올려 전력을 생산하는 중력 기반 에너지 저장 시스템을 개발하고 있습니다. 이 시스템은 기존의 배터리 저장 시스템보다 더 저렴하고 오래 지속되며, 신뢰성이 높습니다.

Gravitricity는 2021년 스코틀랜드에서 첫 번째 개념 증명 타워를 구축하고 성공적으로 테스트했습니다. 현재 Gravitricity는 첫 번째 상업용 시설을 건설하기 위해 18개월의 엔지니어링 설계 단계에 있습니다. 이 시설은 2025년 또는 2026년에 완공될 것으로 예상됩니다.

Gravitricity의 시스템은 전력망의 안정성을 유지하고 신재생 에너지원을 보완하는 데 도움이 될 수 있습니다. 또한, 이 시스템은 전력 수요가 급증하는 시간 동안 전력을 공급할 수 있습니다.

Gravitricity는 중력 기반 에너지 저장 시스템의 잠재력을 믿고 있습니다. 이 시스템은 전 세계의 전력망을 안정화하고 신재생 에너지원을 보완하는 데 도움이 될 수 있습니다.