6 ms·

Molten Aluminum Lakes Offer Power Storage for German Wind Farms

80 points by sveme 12y ago

tinco 12y ago
This is nice for soaking up and making good use of peaks, but it does nothing for the lows, the aluminium can't give back the electricity, so you'd still need coal plants to complement the wind/solar farms when they're down. That said, even if we could reduce the need for coal plants that would be a huge win of course.
- danieltillett 12y ago
  They can help by improving the financial viability of intermittent power sources like wind by acting as soak for excess production. This allows you to invest greater amounts in wind farms and hence reduce overall coal use. It is possible that doing this might have the opposite effect if the wind farms are making most of their profit from the price spikes. In this case putting power back into the system by lowering usage in peak times might make wind less financially viable.
  - raverbashing 12y ago
    The price spikes exist regardless, because those are from high-usage hours (basically day hours) and at a longer range, at summers and winters (depending on where you are) because of heating and a/c. A lot of factories already use more energy in the evening/mornings, because electricity is cheaper at those times. Storage technologies are a huge potential to be explored.
- audunw 12y ago
  > but it does nothing for the lows, the aluminium can't give back the electricity Actually, it seems they might be doing precisely that. See the information in the other comments. It's hard to say for sure, even the primary sources seem fuzzy. But this graphic seems to indicate that they are indeed extracting electric energy from the molten aluminum: http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_630.jpg http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_... This presentation also shows the energy arrow pointing from the aluminum plant to the consumer: http://www.innovationsforum-energiewende.de/wp-content/uploads/2013/11/Thomas-Flesch-Trimet.pdf http://www.innovationsforum-energiewende.de/wp-content/uploa... The most confusing thing about all of this is that they say that they only adjust their own power consumption by +/- 25%, which seems to contradict the statement that they're giving energy back. But as far as I can understand, this +/-25% is the long term average. Of course they need to consume a positive net amount of energy during the day to keep the plant running. But it seems that they are able to pump energy back into the grid for a short amount of time, which would be during the hours when solar/wind power is at a minimum.
  - graycat 12y ago
    Maybe they are just giving back the energy to the grid in two respects, (1) energy they contracted for today they do not consume but sell back to the grid and (2) the energy was to come via the grid to them but, in not consuming that energy, the energy flows to homes, etc. instead and, thus, at least is redirected in the grud or, if you will, flows from the aluminum plant to the homes. At one point, they do say virtual. The losses involved are from some somewhat inefficient use of the grid and, there, losses flowing the energy through the grid.
- nhaehnle 12y ago
  It is misleading to claim that this does nothing for the lows, because everything that's happening here is symmetric. Let's say that aluminium production currently draws a permanent base load of 1GW. Let's say that the minimum acceptable overall level of electricity production given the status quo is 20GW. If aluminium producers manage to adapt their production so that they can temporarily operate on only 0.5GW, then the minimum acceptable overall level of electricity production is now 19.5GW. Unlike what the article misleadingly says, this is not magic that can somehow generate electricity when all other sources fail. But it does shift the line of when low levels of production become critical.
qwerta 12y ago
Article is bit misleading. They do not 'store' energy in the same way as battery, they never pump electricity back to grid. They just adjust their consumption to use cheap energy. > By varying the rate at which the metal is produced, the plant will be able to adjust the power consumption of the 290-megawatt smelter up and down by about 25 percent. Trimet can soak power from the grid when energy is cheap. It can then resell the power when demand is at its peak. The company can temporarily reduce its power consumption by slowing the electrolysis, cutting the energy drain.
- danmaz74 12y ago
  The article isn't clear at all, but they say "It can then resell the power when demand is at its peak." I wonder if they didn't understand the thing, or if they missed some very important information about getting energy back from the aluminium. EDIT: They also talk about a conversion rate of 90%, so this makes me think there needs to be a mechanism to generate current.
  - pja 12y ago
    Yeah, the way the article is worded further down strongly suggests that they are using the aluminium as an energy source: "Using the production process as a virtual battery is “an interesting option” for the industry, said Marian Klobasa, who heads the demand response and smart grids unit at Germany’s Fraunhofer Institute for System and Innovation Research ISI, an applied science researcher. If the volatility of the power market increases, Klobasa said by phone from Karlsruhe, “then it may make commercial sense and be economically worthwhile.” Trimet’s Hauck estimates the full costs 70 euros to 150 euros to store one megawatt-hour based on 1,000 hours of use per year. That would make supply competitive at some periods of peak demand during the winter." Aluminium plants in the UK already do demand shedding at time of peak load on the UK power grid - I'm sure German plants do much the same thing.
  - qwerta 12y ago
    I think they have contract obligation to take some energy, so they just resell it. Anyway the biggest problem of German grid are not really peak hours, but transporting energy from north where turbines are to industrial south.
ThePhysicist 12y ago
The article is really misleading: If I understand correctly, what Trimet will do is to REDUCE its power consumption on demand in order to reduce the stress on the power grid at times when there's not enough energy available for everyone. Since Trimet alone consumes about 0.7 % of Germany's energy production, adapting its energy consumption can help a lot to stabilize the power grid. Here's an article that makes this a bit more clear: http://www.renewablesinternational.net/german-aluminum-firm-rescues-grid-twice/150/407/82143/ http://www.renewablesinternational.net/german-aluminum-firm-... The general term for this is "demand response": https://en.wikipedia.org/wiki/Demand_response https://en.wikipedia.org/wiki/Demand_response The author of the Bloomberg article seems to think that they will use the Aluminium as a battery, releasing energy back to the grid, which to my understanding is not at all what they are planning to do (or even possible, for that matter). BTW, a Businessweek article seems to get this wrong as well: http://www.businessweek.com/articles/2014-11-26/germanys-trimet-aluminium-turns-smelting-tanks-into-batteries http://www.businessweek.com/articles/2014-11-26/germanys-tri...
- sveme 12y ago
  It's really a badly written article about an interesting topic - and I'm not sure what the real story is. Considering the graphic: http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_630.jpg http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_... it looks like they are indeed releasing energy back to the grid. Additional article: http://www.aluinfo.de/index.php/gda-news-en/items/trimet-develops-virtual-electricity-storage.html http://www.aluinfo.de/index.php/gda-news-en/items/trimet-dev... It looks more like they are adapting the process to handle energy fluctuations. The current process most likely requires a steady current and they are adapting the process to ramp up during times of cheap energy and throttle it during times of expensive energy. Still no battery, more like a balancer, adaptively throttling energy consumption. Edit More information from a paper abstract [1]: High Frequency Power Modulation - TRIMET Smelters Provide Primary Control Power for Stabilizing the Frequency in the Electricity Grid Scope The strong growth of renewable energy in Germany leads to high prices fluctuations, varying with the availability of these energy resources. To deal with this situation, TRIMET is using the tool “power modulation” since 2008 to compensate these strong price effects. Simultaneously the strong growth of renewable energy sources leads to a need of primary regulation energy for stabilizing the electricity grid at 50 Hz. In this context, TRIMET is the first electricity consumer world wide, which provides primary regulation energy by modulating a consumer. Traditionally this source of energy is only provided by power plants or energy storage plants, e.g. pumped energy storage or stationery batteries. http://www.programmaster.org/PM/PM.nsf/ApprovedAbstracts/281A8D0A5E4E0F0085257A48004DD9DA?OpenDocument http://www.programmaster.org/PM/PM.nsf/ApprovedAbstracts/281... Now were getting closer to the real thing. Edit II [2]: TRIMET Aluminium SE is developing a process that can turn electro- lytic furnaces for the production of primary aluminum in collabora- tion with conventional power plants into energy storage reservoirs for renewable energy. Aluminum has a high energy density. This makes its production energy-intensive and aluminum smelters re- cipients of base-load electricity. Excess energy is stored in the light metal. The principle behind the new process is the grid-commutated operation of the production equipment. To ensure this, the electrolysis cells are modified so that their output can be increased or reduced for several hours, as needed. The ope- rating point is selected in such a way that the output can be raised or lowered by more than 25 percent for hours. This makes it possible to provide enormous storage capacity. Using this method, TRIMET aluminum smelters could provide outputs of up to 130 megawatts with future capacities of up to 6,000 megawatt hours. This corresponds to the daily energy consumption of two million people. The “virtual battery” relies on the improved flexibility of aluminum elec- trolysis. With this method, TRIMET is revolutionizing the basic principle of a manufacturing process that has existed for more than 120 years. An electrolytic furnace is similar to a water container whose walls are made of ice. To ensure that the tank does not melt, the ambient temperature must be kept very low. But it must not reach a temperature that is too cold, or the water in the tank will freeze. Similarly, the temperature of the electrolytic furnace must be harmonized in order to stabilize the fur- nace walls under fluctuating power supply levels. The process developed by TRIMET regulates this balance through the clever use of exhaust heat, a form of thermal insulation that can be adjusted in an innovative way. The process offers significant advantages over other storage systems. At 85 percent, the efficiency factor of the aluminum storage reservoir approaches that of pump storage reservoirs, far higher than those of compressed-air or hydrogen storage reservoirs. what’s more, the system does not require new power lines, since it is integrated into the existing high-voltage grid. [2] http://www.trimet.de/fileadmin/pdf/trimet-at-a-glance-2013.pdf http://www.trimet.de/fileadmin/pdf/trimet-at-a-glance-2013.p...
Mithaldu 12y ago
The original german presentation of this is here: http://www.innovationsforum-energiewende.de/wp-content/uploads/2013/11/Thomas-Flesch-Trimet.pdf http://www.innovationsforum-energiewende.de/wp-content/uploa... To put this in simple terms: Normally the plant runs at a constant rate of energy consumption, due to restrictions in how the production process works. This means sometimes there will be a deficit of available electricity, other times there will be a surplus. They plan to change their production process such that they can: 1. soak up the surplus usefully when it is present and 2. "give back" energy to the grid by reducing their own consumption when there is a deficit They never feed back any energy, they just make it so more energy is available on the grid by reducing their own consumption. The difficult part here is that there is a certain engineering effort necessary to make this possible in the first place without disrupting the production process.
- jpfr 12y ago
  Some years ago Germany "deregulated" its energy sector. The energy providers are buying and selling electricity on exchange markets where prices change with supply and demand. Today, industrial clients are changing to dynamic pricing schemes instead of fixed price-per-kWh contracts with a supplier. That means they also schedule their consumption to profit from low prices when supply is high and demand low. In the future, big industrial clients could take an even more active role on the energy markets and directly trade capacity without an energy supplier as intermediary. Germany invests a lot in the grid infrastructure to enable more flexibility and decentralized energy sources without risking black outs. They have to do so, as it was politically decided to phase out all nuclear power plants after Fukushima happened. But it's not easy since nuclear plants provide a very stable "supply base" whereas the rising renewables are more volatile.
venomsnake 12y ago
Here is a billion dollar question: If we mix aluminum with mercury will we be able to use it as a real battery with high enough efficiency? Or to get real freaky: thermite -> Fe + Al2O3 + electricity, Then we break down corundum to al + o?
- dredmorbius 12y ago
  No need to mix it with mercury. An aluminium-air battery is a thing. And among the best anodes for metal-air batteries is aluminium.
Sanddancer 12y ago
My first thought when I read the headline was that a German firm had gone through to find a new substance for use in molten salt storage [1]. Reading through it, I was a bit disappointed that there doesn't seem to be any sort of waste heat recovery in place here, which is making me curious. Given that the molten aluminum needs cooled and shaped into ingots to be distributed to manufacturers, I'm curious if there is any sort of waste heat recovery system in place, and/or a system to pump that heat into any sort of a District Heating [2] sort of system. All that heating in the system has to go somewhere, and given the sizes of the smelting halls, it seems like it would be profitable to set some sort of system up. [1] http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_salt_technology http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_s... [2] http://en.wikipedia.org/wiki/District_heating http://en.wikipedia.org/wiki/District_heating
- dredmorbius 12y ago
  The fact that a metal-air battery is a thing, and that aluminum is actually one of the best anodes for use in them, only confuses the matter further. http://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery http://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery
graycat 12y ago
But, could molten aluminum or other metal be used for energy storage? So, when the sun is shining and/or the wind is blowing, use the resulting electric power to heat the metal by, say, just simple resistance heating. Then when want to draw energy from the molten metal, just have some tubes made of metal with a higher melting temperature carry water to be converted to steam to turn steam turbines and generate power. Since I doubt I'm nearly the first to think of such a thing, I have to guess that the detailed engineering and costing makes it not worthwhile.
- Sanddancer 12y ago
  That's the exact system behind molten salt storage [1]. It's just now getting to the point where it's really feasible, but is something that's being researched for the exact areas you described. [1] http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_salt_technology http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_s...
- dredmorbius 12y ago
  Yes. You've got two options. One is the straight thermal route, the other is to run the aluminum oxidation process forward and backward, in which the aluminium is the cathode and oxygen from the air the anode. It's just like any other battery in that you're creating an electric potential difference and current flow directly.
  - graycat 12y ago
    I wondered if it was necessary to boil water
    - dredmorbius 12y ago
      It's not necessary, but it's a good route. You could run a Stirling-cycle engine off a hot and cold end without a phase-change working fluid. But gas turbines are very efficient (and simple), and work best when working with the very high-level pressure gradient presented either by combustion (as with a jet engine) or live steam (with a pressure drop in the condensed state) as with a steam turbine. You could substitute other volatile working fluids, but water is cheap, abundant, and provides useful work at temperatures typically attainable in systems -- 100 - 1000 C (typically in the 200 C - 500 C range).
dredmorbius 12y ago
This is NOT an energy storage system. It's a demand-dispatch system. Think of it this way: in a conventional fuel-driven grid, your generation (supply) is dispatchable. If you need more electrical generation, you can crank up your coal, oil, gas, or nuclear-fueled generators (or hydro capacity) to meet that demand. Since demand is largely predictable based on known parameters (weather, day of week, season), even slow-to-cycle generation (e.g., coal and nuclear) can offer pretty good demand-matching, with the difference made up by other options. Gas and hydro can respond to load shifts in seconds to minutes, vs. hours for the others. Under a largely renewables scenario, your generation is not dispatchable. Your options are: ⚫ Retain some dispatchable capacity: hydro (conventional or pumped storage), biofuels, synfuels, geothermal, nuclear, conventional fossil fuels. ⚫ Utilize storage. Batteries, thermal energy storage, banked capacity (e.g., excess heating or cooling utilized later), pumped hydro, compressed air energy storage (CAES), flywheels, capacitors, electricity-to-fuel. All have limitations, most are cost-prohibitive. ⚫ Load shifting. This generally goes by the terms "demand response" or "demand side management". Effectively it's the inverse of the present model: rather than shift supply to meet demand, you're shifting demand to meet (an inelastic) supply. Typically this involves large industrial uses and customers. Tino Andeson's reporting here is horrible. It's sadly all too commonplace in general coverage of energy issues.
- bryanlarsen 12y ago
  It's a horrible article, but it certainly does imply that it is an energy storage system. "The electrodes, in tandem with the liquid metal that settles to the bottom of the tank and the oxygen above, form an enormous battery." "Trimet can soak power from the grid when energy is cheap. It can then resell the power when demand is at its peak." My guess: they usually just load shift in response to prices, but when prices get exceptionally high they resell, and the author mixes the two up.
  - dredmorbius 12y ago
    Problem is that there's different information available in different places which confirm either argument. The Trimet annual report / brochure linked elsewhere in this discussion makes clear that this is only demand-side management / load shifting. The diagram linked elsewhere ... here: http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_630.jpg http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_... ... shows what could well be a metal-air battery. It's a fucking disaster of reportage.

80 points by sveme 12y ago

tinco 12y ago

This is nice for soaking up and making good use of peaks, but it does nothing for the lows, the aluminium can't give back the electricity, so you'd still need coal plants to complement the wind/solar farms when they're down. That said, even if we could reduce the need for coal plants that would be a huge win of course.

danieltillett 12y ago
They can help by improving the financial viability of intermittent power sources like wind by acting as soak for excess production. This allows you to invest greater amounts in wind farms and hence reduce overall coal use. It is possible that doing this might have the opposite effect if the wind farms are making most of their profit from the price spikes. In this case putting power back into the system by lowering usage in peak times might make wind less financially viable.
- raverbashing 12y ago
  The price spikes exist regardless, because those are from high-usage hours (basically day hours) and at a longer range, at summers and winters (depending on where you are) because of heating and a/c. A lot of factories already use more energy in the evening/mornings, because electricity is cheaper at those times. Storage technologies are a huge potential to be explored.
audunw 12y ago
> but it does nothing for the lows, the aluminium can't give back the electricity Actually, it seems they might be doing precisely that. See the information in the other comments. It's hard to say for sure, even the primary sources seem fuzzy. But this graphic seems to indicate that they are indeed extracting electric energy from the molten aluminum: http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_630.jpg http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_... This presentation also shows the energy arrow pointing from the aluminum plant to the consumer: http://www.innovationsforum-energiewende.de/wp-content/uploads/2013/11/Thomas-Flesch-Trimet.pdf http://www.innovationsforum-energiewende.de/wp-content/uploa... The most confusing thing about all of this is that they say that they only adjust their own power consumption by +/- 25%, which seems to contradict the statement that they're giving energy back. But as far as I can understand, this +/-25% is the long term average. Of course they need to consume a positive net amount of energy during the day to keep the plant running. But it seems that they are able to pump energy back into the grid for a short amount of time, which would be during the hours when solar/wind power is at a minimum.
- graycat 12y ago
  Maybe they are just giving back the energy to the grid in two respects, (1) energy they contracted for today they do not consume but sell back to the grid and (2) the energy was to come via the grid to them but, in not consuming that energy, the energy flows to homes, etc. instead and, thus, at least is redirected in the grud or, if you will, flows from the aluminum plant to the homes. At one point, they do say virtual. The losses involved are from some somewhat inefficient use of the grid and, there, losses flowing the energy through the grid.
nhaehnle 12y ago
It is misleading to claim that this does nothing for the lows, because everything that's happening here is symmetric. Let's say that aluminium production currently draws a permanent base load of 1GW. Let's say that the minimum acceptable overall level of electricity production given the status quo is 20GW. If aluminium producers manage to adapt their production so that they can temporarily operate on only 0.5GW, then the minimum acceptable overall level of electricity production is now 19.5GW. Unlike what the article misleadingly says, this is not magic that can somehow generate electricity when all other sources fail. But it does shift the line of when low levels of production become critical.

qwerta 12y ago

Article is bit misleading. They do not 'store' energy in the same way as battery, they never pump electricity back to grid. They just adjust their consumption to use cheap energy. > By varying the rate at which the metal is produced, the plant will be able to adjust the power consumption of the 290-megawatt smelter up and down by about 25 percent. Trimet can soak power from the grid when energy is cheap. It can then resell the power when demand is at its peak. The company can temporarily reduce its power consumption by slowing the electrolysis, cutting the energy drain.

danmaz74 12y ago
The article isn't clear at all, but they say "It can then resell the power when demand is at its peak." I wonder if they didn't understand the thing, or if they missed some very important information about getting energy back from the aluminium. EDIT: They also talk about a conversion rate of 90%, so this makes me think there needs to be a mechanism to generate current.
- pja 12y ago
  Yeah, the way the article is worded further down strongly suggests that they are using the aluminium as an energy source: "Using the production process as a virtual battery is “an interesting option” for the industry, said Marian Klobasa, who heads the demand response and smart grids unit at Germany’s Fraunhofer Institute for System and Innovation Research ISI, an applied science researcher. If the volatility of the power market increases, Klobasa said by phone from Karlsruhe, “then it may make commercial sense and be economically worthwhile.” Trimet’s Hauck estimates the full costs 70 euros to 150 euros to store one megawatt-hour based on 1,000 hours of use per year. That would make supply competitive at some periods of peak demand during the winter." Aluminium plants in the UK already do demand shedding at time of peak load on the UK power grid - I'm sure German plants do much the same thing.
- qwerta 12y ago
  I think they have contract obligation to take some energy, so they just resell it. Anyway the biggest problem of German grid are not really peak hours, but transporting energy from north where turbines are to industrial south.

ThePhysicist 12y ago

The article is really misleading: If I understand correctly, what Trimet will do is to REDUCE its power consumption on demand in order to reduce the stress on the power grid at times when there's not enough energy available for everyone. Since Trimet alone consumes about 0.7 % of Germany's energy production, adapting its energy consumption can help a lot to stabilize the power grid. Here's an article that makes this a bit more clear: http://www.renewablesinternational.net/german-aluminum-firm-rescues-grid-twice/150/407/82143/ http://www.renewablesinternational.net/german-aluminum-firm-... The general term for this is "demand response": https://en.wikipedia.org/wiki/Demand_response https://en.wikipedia.org/wiki/Demand_response The author of the Bloomberg article seems to think that they will use the Aluminium as a battery, releasing energy back to the grid, which to my understanding is not at all what they are planning to do (or even possible, for that matter). BTW, a Businessweek article seems to get this wrong as well: http://www.businessweek.com/articles/2014-11-26/germanys-trimet-aluminium-turns-smelting-tanks-into-batteries http://www.businessweek.com/articles/2014-11-26/germanys-tri...

sveme 12y ago
It's really a badly written article about an interesting topic - and I'm not sure what the real story is. Considering the graphic: http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_630.jpg http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_... it looks like they are indeed releasing energy back to the grid. Additional article: http://www.aluinfo.de/index.php/gda-news-en/items/trimet-develops-virtual-electricity-storage.html http://www.aluinfo.de/index.php/gda-news-en/items/trimet-dev... It looks more like they are adapting the process to handle energy fluctuations. The current process most likely requires a steady current and they are adapting the process to ramp up during times of cheap energy and throttle it during times of expensive energy. Still no battery, more like a balancer, adaptively throttling energy consumption. Edit More information from a paper abstract [1]: High Frequency Power Modulation - TRIMET Smelters Provide Primary Control Power for Stabilizing the Frequency in the Electricity Grid Scope The strong growth of renewable energy in Germany leads to high prices fluctuations, varying with the availability of these energy resources. To deal with this situation, TRIMET is using the tool “power modulation” since 2008 to compensate these strong price effects. Simultaneously the strong growth of renewable energy sources leads to a need of primary regulation energy for stabilizing the electricity grid at 50 Hz. In this context, TRIMET is the first electricity consumer world wide, which provides primary regulation energy by modulating a consumer. Traditionally this source of energy is only provided by power plants or energy storage plants, e.g. pumped energy storage or stationery batteries. http://www.programmaster.org/PM/PM.nsf/ApprovedAbstracts/281A8D0A5E4E0F0085257A48004DD9DA?OpenDocument http://www.programmaster.org/PM/PM.nsf/ApprovedAbstracts/281... Now were getting closer to the real thing. Edit II [2]: TRIMET Aluminium SE is developing a process that can turn electro- lytic furnaces for the production of primary aluminum in collabora- tion with conventional power plants into energy storage reservoirs for renewable energy. Aluminum has a high energy density. This makes its production energy-intensive and aluminum smelters re- cipients of base-load electricity. Excess energy is stored in the light metal. The principle behind the new process is the grid-commutated operation of the production equipment. To ensure this, the electrolysis cells are modified so that their output can be increased or reduced for several hours, as needed. The ope- rating point is selected in such a way that the output can be raised or lowered by more than 25 percent for hours. This makes it possible to provide enormous storage capacity. Using this method, TRIMET aluminum smelters could provide outputs of up to 130 megawatts with future capacities of up to 6,000 megawatt hours. This corresponds to the daily energy consumption of two million people. The “virtual battery” relies on the improved flexibility of aluminum elec- trolysis. With this method, TRIMET is revolutionizing the basic principle of a manufacturing process that has existed for more than 120 years. An electrolytic furnace is similar to a water container whose walls are made of ice. To ensure that the tank does not melt, the ambient temperature must be kept very low. But it must not reach a temperature that is too cold, or the water in the tank will freeze. Similarly, the temperature of the electrolytic furnace must be harmonized in order to stabilize the fur- nace walls under fluctuating power supply levels. The process developed by TRIMET regulates this balance through the clever use of exhaust heat, a form of thermal insulation that can be adjusted in an innovative way. The process offers significant advantages over other storage systems. At 85 percent, the efficiency factor of the aluminum storage reservoir approaches that of pump storage reservoirs, far higher than those of compressed-air or hydrogen storage reservoirs. what’s more, the system does not require new power lines, since it is integrated into the existing high-voltage grid. [2] http://www.trimet.de/fileadmin/pdf/trimet-at-a-glance-2013.pdf http://www.trimet.de/fileadmin/pdf/trimet-at-a-glance-2013.p...

Mithaldu 12y ago

The original german presentation of this is here: http://www.innovationsforum-energiewende.de/wp-content/uploads/2013/11/Thomas-Flesch-Trimet.pdf http://www.innovationsforum-energiewende.de/wp-content/uploa... To put this in simple terms: Normally the plant runs at a constant rate of energy consumption, due to restrictions in how the production process works. This means sometimes there will be a deficit of available electricity, other times there will be a surplus. They plan to change their production process such that they can: 1. soak up the surplus usefully when it is present and 2. "give back" energy to the grid by reducing their own consumption when there is a deficit They never feed back any energy, they just make it so more energy is available on the grid by reducing their own consumption. The difficult part here is that there is a certain engineering effort necessary to make this possible in the first place without disrupting the production process.

jpfr 12y ago
Some years ago Germany "deregulated" its energy sector. The energy providers are buying and selling electricity on exchange markets where prices change with supply and demand. Today, industrial clients are changing to dynamic pricing schemes instead of fixed price-per-kWh contracts with a supplier. That means they also schedule their consumption to profit from low prices when supply is high and demand low. In the future, big industrial clients could take an even more active role on the energy markets and directly trade capacity without an energy supplier as intermediary. Germany invests a lot in the grid infrastructure to enable more flexibility and decentralized energy sources without risking black outs. They have to do so, as it was politically decided to phase out all nuclear power plants after Fukushima happened. But it's not easy since nuclear plants provide a very stable "supply base" whereas the rising renewables are more volatile.

venomsnake 12y ago

Here is a billion dollar question: If we mix aluminum with mercury will we be able to use it as a real battery with high enough efficiency? Or to get real freaky: thermite -> Fe + Al2O3 + electricity, Then we break down corundum to al + o?

dredmorbius 12y ago
No need to mix it with mercury. An aluminium-air battery is a thing. And among the best anodes for metal-air batteries is aluminium.

Sanddancer 12y ago

My first thought when I read the headline was that a German firm had gone through to find a new substance for use in molten salt storage [1]. Reading through it, I was a bit disappointed that there doesn't seem to be any sort of waste heat recovery in place here, which is making me curious. Given that the molten aluminum needs cooled and shaped into ingots to be distributed to manufacturers, I'm curious if there is any sort of waste heat recovery system in place, and/or a system to pump that heat into any sort of a District Heating [2] sort of system. All that heating in the system has to go somewhere, and given the sizes of the smelting halls, it seems like it would be profitable to set some sort of system up. [1] http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_salt_technology http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_s... [2] http://en.wikipedia.org/wiki/District_heating http://en.wikipedia.org/wiki/District_heating

dredmorbius 12y ago
The fact that a metal-air battery is a thing, and that aluminum is actually one of the best anodes for use in them, only confuses the matter further. http://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery http://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery

graycat 12y ago

But, could molten aluminum or other metal be used for energy storage? So, when the sun is shining and/or the wind is blowing, use the resulting electric power to heat the metal by, say, just simple resistance heating. Then when want to draw energy from the molten metal, just have some tubes made of metal with a higher melting temperature carry water to be converted to steam to turn steam turbines and generate power. Since I doubt I'm nearly the first to think of such a thing, I have to guess that the detailed engineering and costing makes it not worthwhile.

Sanddancer 12y ago
That's the exact system behind molten salt storage [1]. It's just now getting to the point where it's really feasible, but is something that's being researched for the exact areas you described. [1] http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_salt_technology http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_s...
dredmorbius 12y ago
Yes. You've got two options. One is the straight thermal route, the other is to run the aluminum oxidation process forward and backward, in which the aluminium is the cathode and oxygen from the air the anode. It's just like any other battery in that you're creating an electric potential difference and current flow directly.
- graycat 12y ago
  I wondered if it was necessary to boil water
  - dredmorbius 12y ago
    It's not necessary, but it's a good route. You could run a Stirling-cycle engine off a hot and cold end without a phase-change working fluid. But gas turbines are very efficient (and simple), and work best when working with the very high-level pressure gradient presented either by combustion (as with a jet engine) or live steam (with a pressure drop in the condensed state) as with a steam turbine. You could substitute other volatile working fluids, but water is cheap, abundant, and provides useful work at temperatures typically attainable in systems -- 100 - 1000 C (typically in the 200 C - 500 C range).

dredmorbius 12y ago

This is NOT an energy storage system. It's a demand-dispatch system. Think of it this way: in a conventional fuel-driven grid, your generation (supply) is dispatchable. If you need more electrical generation, you can crank up your coal, oil, gas, or nuclear-fueled generators (or hydro capacity) to meet that demand. Since demand is largely predictable based on known parameters (weather, day of week, season), even slow-to-cycle generation (e.g., coal and nuclear) can offer pretty good demand-matching, with the difference made up by other options. Gas and hydro can respond to load shifts in seconds to minutes, vs. hours for the others. Under a largely renewables scenario, your generation is not dispatchable. Your options are: ⚫ Retain some dispatchable capacity: hydro (conventional or pumped storage), biofuels, synfuels, geothermal, nuclear, conventional fossil fuels. ⚫ Utilize storage. Batteries, thermal energy storage, banked capacity (e.g., excess heating or cooling utilized later), pumped hydro, compressed air energy storage (CAES), flywheels, capacitors, electricity-to-fuel. All have limitations, most are cost-prohibitive. ⚫ Load shifting. This generally goes by the terms "demand response" or "demand side management". Effectively it's the inverse of the present model: rather than shift supply to meet demand, you're shifting demand to meet (an inelastic) supply. Typically this involves large industrial uses and customers. Tino Andeson's reporting here is horrible. It's sadly all too commonplace in general coverage of energy issues.

bryanlarsen 12y ago
It's a horrible article, but it certainly does imply that it is an energy storage system. "The electrodes, in tandem with the liquid metal that settles to the bottom of the tank and the oxygen above, form an enormous battery." "Trimet can soak power from the grid when energy is cheap. It can then resell the power when demand is at its peak." My guess: they usually just load shift in response to prices, but when prices get exceptionally high they resell, and the author mixes the two up.
- dredmorbius 12y ago
  Problem is that there's different information available in different places which confirm either argument. The Trimet annual report / brochure linked elsewhere in this discussion makes clear that this is only demand-side management / load shifting. The diagram linked elsewhere ... here: http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_630.jpg http://images.bwbx.io/cms/2014-11-26/tech_aluminumgraphic49_... ... shows what could well be a metal-air battery. It's a fucking disaster of reportage.