Molten Aluminum Lakes Offer Power Storage for German Wind Farms
bloomberg.com
bloomberg.com
http://www.renewablesinternational.net/german-aluminum-firm-...
The general term for this is "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-tri...
Additional article: 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/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.p...
That's why they call it "virtual".
It's possible to create a metal-air battery, and aluminium is in fact one of the more promising substrates for such. In which case, what you've got isn't a "virtual" battery -- able to soak up and release load, but an actual battery, able to soak up and release current as electrical energy.
http://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery
http://en.wikipedia.org/wiki/Metal%E2%80%93air_electrochemic...
The fact that the Bloomberg story doesn't allow making heads or tails of this is utterly frustrating.
Addendum: I've written Timo, and his editors, citing the problems with the article and discussion here.
You're either a battery or you're not. If you can store and release energy in the same form you're a battery. If you can't, but can store energy for later use, then you're an energy banking system. Otherwise you're a demand response system.
This is a demand response system.
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.
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.
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.
"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.
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_... ... shows what could well be a metal-air battery.
It's a fucking disaster of reportage.
> 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.
EDIT: They also talk about a conversion rate of 90%, so this makes me think there needs to be a mechanism to generate current.
"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.
Anyway the biggest problem of German grid are not really peak hours, but transporting energy from north where turbines are to industrial south.
The basic rule is - those, who unbalances the network pays those that balances it back for the troubles, so there's huge incentive to predict your power requirements and transfer requirements precisely. I guess Germany with their solar cells and wind turbines have a lot of problems with that.
There are a few whole markets set up with energy, transfer capacities, reduction (or increases) offers by both plants and users, and it works quite nicely.
I worked on a system for bulk energy trading and it was very intersting to see how it works behind the scenes.
BTW demand reduction is actually BETTER than storing and returning energy. Demand reduction of 100 MW frees more than 100 MW (heating loses), and lets other people use the wires in that time.
http://en.wikipedia.org/wiki/Control_of_the_National_Grid_%2...
Another, unrelated, slightly bonkers UK power supply innovation is the ability for energy companies to remotely control their customers' supplies using secret signals embedded in Radio 4:
They are melting aluminum oxide, which is used as the insulator in electrolytic capacitors, and the extracted aluminum pools at the bottom apparently.
If they are able to maintain the oxide layer at suitable thickness, do they not basically have a capacitor?
"The electrodes, in tandem with the liquid metal that settles to the bottom of the tank and the oxygen above, form an enormous battery."
I know nothing about battery chemistry, does that make any sense?
That said, even if we could reduce the need for coal plants that would be a huge win of course.
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.
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.
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_...
This presentation also shows the energy arrow pointing from the aluminum plant to the consumer: 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.
The losses involved are from some somewhat inefficient use of the grid and, there, losses flowing the energy through the grid.
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.
[1] http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_s...
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.
[1] http://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_s...
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.
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).
Or to get real freaky: thermite -> Fe + Al2O3 + electricity, Then we break down corundum to al + o?