6 ms·

I'm a little embarrassed that in all of the discussions I've heard about ways to store solar energy for dark periods, I never noticed that this kind of solution

I'm a little embarrassed that in all of the discussions I've heard about ways to store solar energy for dark periods, I never noticed that this kind of solution was omitted. I wonder how it stacks up against the more commonly discussed approaches.

DavidHm 8y ago
Eh. (imho) Hydro pumping is way more simple, and is just limited by the fact that you can't have it wherever you want. Also concrete is not exactly environmentally friendly to make.
- DoofusOfDeath 8y ago
  Sorry, I should have been more specific. The category of solution I didn't seem to be hearing much about was "move a dense, solid mass uphill". I wasn't thinking specifically about concrete.
  - criley2 8y ago
    To be fair, the gold standard is "move a dense, liquid mass uphill" so doing it with solids is kind of a novel approach.
- TeMPOraL 8y ago
  > Also concrete is not exactly environmentally friendly to make. Anything heavy will work. I wonder about bags of stones & rubble, or earth itself. The challenge would be making such bags not break apart due to fall.
  - knodi123 8y ago
    > not break apart due to fall. If they're falling and there's an impact at the end, something has already gone wrong. When operating correctly, the descent is a smooth glide.
- tomatotomato37 8y ago
  This actually seems like the more ecological design, as the concrete used for weight here would be less than the amount used for a dam, and you wouldn't also have to pervert the flow of a river in order to build it. Besides, one time costs are trivial compared to running costs of industrial processes in terms of the environment, especially in terms of power production.
  - konschubert 8y ago
    > as the concrete used for weight here would be less than the amount used for a dam Think that through. A dam probably holds 100 or 1000 tons of water for every ton of dam material. A concrete weight holds exactly on ton of concrete for one ton of concrete weight material. And "amount of weight helt", be it water or concrete, is Exactly what matters here.
  - 0xffff2 8y ago
    >... and you wouldn't also have to pervert the flow of a river in order to build it. You don't necessarily need a river to be involved at all for pumped storage. Just build two reservoirs at different heights.
acjohnson55 8y ago
I mean, they basically in the article that the energy density is abysmal. You can't take advantage of the space filling properties of pumped water, either. I'm sure there are valid use cases, but I'm guessing they're specialized.
- chrisb 8y ago
  The energy density really is abysmal, which is why the "lifting heavy things up" techinique of energy storage is essentially never discussed outside of pumped-storage. The problem is the linear relationship between the mass, the height, and the stored energy: energy = mass * height * gravitational-acceleration. gravitational-acceleration is fixed at the earth's surface to ~10m/s2 So taking an example of 1,000,000 tons lifted up 100 meters: energy = 1,000,000,000 (mass) * 100 (height) * 10 (gravity) = 1,000,000,000,000 Joules This looks like a lot, but really isn't. It's equal to ~278 MWh (megawatt hours), which means it can supply 278 MWs for one hour. 278 MWs is equivalent to one small power station. Note that the largest pumped-storage power station in the UK, which is of course constrained by exactly the same E = mgh formula, Dinorwig (https://en.wikipedia.org/wiki/Dinorwig_Power_Station https://en.wikipedia.org/wiki/Dinorwig_Power_Station) stores ~9,000 MWh. Another way to consider this is to calculate how much mass needs lifting 100m to supply the whole of a country for a day. As a very crude estimate the UK requires an average of about 30,000MW of electrical energy. Over a day this equals 30,000,000,000 * 24 3,600,000 Joules = 2.510^18 Joules per day. The mass required to be lifted up 100m to store this is 2.510^18 / (100 10) = 2.510^15 Kg = 2.510^12 tons = 2,500,000,000,000 tons. Which is many times more than the current global annual concrete production of 10,000,000,000 tons (ref: http://www.columbia.edu/cu/civileng/meyer/publications/publications/83%20Concrete%20Materials%20and%20Sustainable%20Development.pdf http://www.columbia.edu/cu/civileng/meyer/publications/publi...)
  - thechao 8y ago
    I live in an extremely hilly area, made of soft rock (limestone), but very little water. Carving out a hill to 100m down, with a 100x100m cross section is totally doable—we have larger projects just to make flat land to build houses on. If the weight was only 10m high, it’d be ~200k tons. By your calculation that’s ~54MWh/day, or enough energy to power ~1500 homes. There’s a hill the right size next to my village of ~1200 homes. We have excess wind & solar power. So... where do I sign up?
Cthulhu_ 8y ago
It's not omitted, it's just proven to be terribly inefficient. Hydroelectric pumping is being used in practice, being relatively cheap and you can store a huge amount with little materials - millions of tons if need be. Imagine having to lift up blocks of concrete millions of tons heavy and the machinery it would require. A previous discussion mentioned a heavy train being hoisted up and down a slope for the same effect - same problem. In addition to the weight you can shift being a fraction of a hydroelectric dam, you also have to deal with material maintenance and wear and tear, security, etc.
- Nasrudith 8y ago
  Even if the blocks are technically efficient the logistics and lack of granularity would keep it from being more than a curiosity like recharging your phone via a thermoelectric generator stuck in a campfire. Technically it works and is neat but it isn't going to be used much. Water you can get it perfectly load matched. Here you get one concrete block lowered worth of energy and stopping midway has its own share of problems. Look at the mere 100MWh Tesla bank in Australia. They made millions per day and reduced power prices for consumers by millions as well. They did it by not only utterly cornered the power service market but managed to outrun the problem so well they weren't getting paid for all of them until the grid upped their sampling rate to deal with the unprecedented speed for a system that expected dispatched natrual gas turbines to be the fastest thing it would ever deal with. I may be wrong and it may have a legitimate use but it would clearly need complimentary components to cover its flaws.
stephengillie 8y ago
It's like storing energy in electric cars by parking them at the top of big hills. Charge the cars during the day, and park them at the top at dusk. Then drive one downhill every hour at night, using regenerative braking to pull some of the potential-turned-kinetic energy into the battery as electricity. Then discharge the car into the grid. Descending the hills in east Auburn and Kent in WA State usually regenerate 400-500 Wh into my hybrid. Gravitational potential batteries have less vampiric effects than chemical batteries, but still some possibility to suddenly discharge, in a landslide or similar event. And they are less efficient than hydroelectric, as another poster has pointed out.

DavidHm 8y ago

Eh. (imho) Hydro pumping is way more simple, and is just limited by the fact that you can't have it wherever you want. Also concrete is not exactly environmentally friendly to make.

DoofusOfDeath 8y ago
Sorry, I should have been more specific. The category of solution I didn't seem to be hearing much about was "move a dense, solid mass uphill". I wasn't thinking specifically about concrete.
- criley2 8y ago
  To be fair, the gold standard is "move a dense, liquid mass uphill" so doing it with solids is kind of a novel approach.
TeMPOraL 8y ago
> Also concrete is not exactly environmentally friendly to make. Anything heavy will work. I wonder about bags of stones & rubble, or earth itself. The challenge would be making such bags not break apart due to fall.
- knodi123 8y ago
  > not break apart due to fall. If they're falling and there's an impact at the end, something has already gone wrong. When operating correctly, the descent is a smooth glide.
tomatotomato37 8y ago
This actually seems like the more ecological design, as the concrete used for weight here would be less than the amount used for a dam, and you wouldn't also have to pervert the flow of a river in order to build it. Besides, one time costs are trivial compared to running costs of industrial processes in terms of the environment, especially in terms of power production.
- konschubert 8y ago
  > as the concrete used for weight here would be less than the amount used for a dam Think that through. A dam probably holds 100 or 1000 tons of water for every ton of dam material. A concrete weight holds exactly on ton of concrete for one ton of concrete weight material. And "amount of weight helt", be it water or concrete, is Exactly what matters here.
- 0xffff2 8y ago
  >... and you wouldn't also have to pervert the flow of a river in order to build it. You don't necessarily need a river to be involved at all for pumped storage. Just build two reservoirs at different heights.

acjohnson55 8y ago

I mean, they basically in the article that the energy density is abysmal. You can't take advantage of the space filling properties of pumped water, either. I'm sure there are valid use cases, but I'm guessing they're specialized.

chrisb 8y ago
The energy density really is abysmal, which is why the "lifting heavy things up" techinique of energy storage is essentially never discussed outside of pumped-storage. The problem is the linear relationship between the mass, the height, and the stored energy: energy = mass * height * gravitational-acceleration. gravitational-acceleration is fixed at the earth's surface to ~10m/s2 So taking an example of 1,000,000 tons lifted up 100 meters: energy = 1,000,000,000 (mass) * 100 (height) * 10 (gravity) = 1,000,000,000,000 Joules This looks like a lot, but really isn't. It's equal to ~278 MWh (megawatt hours), which means it can supply 278 MWs for one hour. 278 MWs is equivalent to one small power station. Note that the largest pumped-storage power station in the UK, which is of course constrained by exactly the same E = mgh formula, Dinorwig (https://en.wikipedia.org/wiki/Dinorwig_Power_Station https://en.wikipedia.org/wiki/Dinorwig_Power_Station) stores ~9,000 MWh. Another way to consider this is to calculate how much mass needs lifting 100m to supply the whole of a country for a day. As a very crude estimate the UK requires an average of about 30,000MW of electrical energy. Over a day this equals 30,000,000,000 * 24 3,600,000 Joules = 2.510^18 Joules per day. The mass required to be lifted up 100m to store this is 2.510^18 / (100 10) = 2.510^15 Kg = 2.510^12 tons = 2,500,000,000,000 tons. Which is many times more than the current global annual concrete production of 10,000,000,000 tons (ref: http://www.columbia.edu/cu/civileng/meyer/publications/publications/83%20Concrete%20Materials%20and%20Sustainable%20Development.pdf http://www.columbia.edu/cu/civileng/meyer/publications/publi...)
- thechao 8y ago
  I live in an extremely hilly area, made of soft rock (limestone), but very little water. Carving out a hill to 100m down, with a 100x100m cross section is totally doable—we have larger projects just to make flat land to build houses on. If the weight was only 10m high, it’d be ~200k tons. By your calculation that’s ~54MWh/day, or enough energy to power ~1500 homes. There’s a hill the right size next to my village of ~1200 homes. We have excess wind & solar power. So... where do I sign up?

Cthulhu_ 8y ago

It's not omitted, it's just proven to be terribly inefficient. Hydroelectric pumping is being used in practice, being relatively cheap and you can store a huge amount with little materials - millions of tons if need be. Imagine having to lift up blocks of concrete millions of tons heavy and the machinery it would require. A previous discussion mentioned a heavy train being hoisted up and down a slope for the same effect - same problem. In addition to the weight you can shift being a fraction of a hydroelectric dam, you also have to deal with material maintenance and wear and tear, security, etc.

Nasrudith 8y ago
Even if the blocks are technically efficient the logistics and lack of granularity would keep it from being more than a curiosity like recharging your phone via a thermoelectric generator stuck in a campfire. Technically it works and is neat but it isn't going to be used much. Water you can get it perfectly load matched. Here you get one concrete block lowered worth of energy and stopping midway has its own share of problems. Look at the mere 100MWh Tesla bank in Australia. They made millions per day and reduced power prices for consumers by millions as well. They did it by not only utterly cornered the power service market but managed to outrun the problem so well they weren't getting paid for all of them until the grid upped their sampling rate to deal with the unprecedented speed for a system that expected dispatched natrual gas turbines to be the fastest thing it would ever deal with. I may be wrong and it may have a legitimate use but it would clearly need complimentary components to cover its flaws.

stephengillie 8y ago

It's like storing energy in electric cars by parking them at the top of big hills. Charge the cars during the day, and park them at the top at dusk. Then drive one downhill every hour at night, using regenerative braking to pull some of the potential-turned-kinetic energy into the battery as electricity. Then discharge the car into the grid. Descending the hills in east Auburn and Kent in WA State usually regenerate 400-500 Wh into my hybrid. Gravitational potential batteries have less vampiric effects than chemical batteries, but still some possibility to suddenly discharge, in a landslide or similar event. And they are less efficient than hydroelectric, as another poster has pointed out.