When stones become energy storage
In a night storage heaters stones are usually heated at night with cheap "low tariff" electricity. The stored heat is then released during the day. Whether
this principle also works on a large scale when it comes to energy use
is currently being tested by engineers in a pilot plant near Hamburg
Altenwerder, a district in the port of Hamburg. With the safety helmet on her head, engineer Jennifer Wagner walks over a construction site. The two buildings - each big as an apartment building - are almost finished. What's missing are the core components:
"The stones are not delivered yet, but in the end they look just like the heap over there, they are very simple quarry stones being blown out of the quarry."
Wagner and her team are waiting for 1,000 tons of volcanic rock from the wind turbine manufacturer Siemens Gamesa. In the next few weeks, the delivery should come. Then the stones will land in one of the two buildings. It is a heat-insulated concrete bunker, which should act as a huge storage - as power storage. Wagner's colleague Hasan Özdem explains the concept:
"The storage is very simple, basically we use electricity, convert it into heat, store the heat, and later turn the heat into electricity."Oversized hair dryer heats up stones
The electricity to be stored drives a massive fan heater, an oversized hair dryer. This blows hot air through thick tubes into the storage building and heats the naturally heat-resistant volcanic rock, up to 600 degrees Celsius. A procedure that experts have already tested on a small scale.
"In 2014, we built the facility where we tested the storage itself - it was about physically controlling the storage and also about the economy - after we did that and the results were better than expected, we now have a bigger one built, which really goes online. "From the heat back to the stream
But the heat in the stones has to be transformed back into electricity. This is done by channeling cold air into the cairn. As a result, it gets really hot and flows through pipes to a steam generator. He then drives a steam turbine. This can be found in the second building, the power plant. Jennifer Wagner:
"On the stage you can see these concrete pillars - there is the steam turbine on it, with a maximum of 1.5 megawatts." The special thing about the steam boiler is that it is designed to carry out frequent changes - always approaching, driving off, driving off, driving off. That's exactly what we designed this kettle for. "
Efficiency is not the decisive criterion
The plant is to be able to store 35 megawatt hours of electrical energy - enough to run the turbine for more than 24 hours. The efficiency, however, sounds rather modest: Just 25 to 30 percent of the electricity used should come out in the end again. But that's not so bad, experts say. Because the stone storage is to be fed mainly with surplus electricity from wind farms and solar systems - electricity so that would otherwise be thrown away, so to speak. The assessment of Jennifer Wagner:
"We assume that at the end of the day not efficiency will be the decisive criterion, but usability."
The new concept could score above all in terms of costs. Because stones are outspoken cheap goods.
"You can find them very often all over the world, the big cost factor is the transport."
Hasan Özdem says - and makes a comparative calculation:
"Not only are our technologies much larger than batteries, they are also ten times cheaper to use."New life for decommissioned power plants?
Batteries are more flexible and can absorb and release energy much faster. By the next summer at the latest, the demonstration plant in the Port of Hamburg should start. The experts hope that it will prove itself - and are already planning significantly larger stone storage. That would be necessary to be able to save economically relevant amounts of electricity, says Jennifer Wagner.
"We made an estimate for a gigawatt-hour investment, which would be the size of a quarter of a football field."
It would even be conceivable to convert decommissioned coal or gas power plants. Then, instead of a coal boiler, a stone storage would make the turbines steam - in the truest sense of the word.
Altenwerder, a district in the port of Hamburg. With the safety helmet on her head, engineer Jennifer Wagner walks over a construction site. The two buildings - each big as an apartment building - are almost finished. What's missing are the core components:
"The stones are not delivered yet, but in the end they look just like the heap over there, they are very simple quarry stones being blown out of the quarry."
Wagner and her team are waiting for 1,000 tons of volcanic rock from the wind turbine manufacturer Siemens Gamesa. In the next few weeks, the delivery should come. Then the stones will land in one of the two buildings. It is a heat-insulated concrete bunker, which should act as a huge storage - as power storage. Wagner's colleague Hasan Özdem explains the concept:
"The storage is very simple, basically we use electricity, convert it into heat, store the heat, and later turn the heat into electricity."Oversized hair dryer heats up stones
The electricity to be stored drives a massive fan heater, an oversized hair dryer. This blows hot air through thick tubes into the storage building and heats the naturally heat-resistant volcanic rock, up to 600 degrees Celsius. A procedure that experts have already tested on a small scale.
"In 2014, we built the facility where we tested the storage itself - it was about physically controlling the storage and also about the economy - after we did that and the results were better than expected, we now have a bigger one built, which really goes online. "From the heat back to the stream
But the heat in the stones has to be transformed back into electricity. This is done by channeling cold air into the cairn. As a result, it gets really hot and flows through pipes to a steam generator. He then drives a steam turbine. This can be found in the second building, the power plant. Jennifer Wagner:
"On the stage you can see these concrete pillars - there is the steam turbine on it, with a maximum of 1.5 megawatts." The special thing about the steam boiler is that it is designed to carry out frequent changes - always approaching, driving off, driving off, driving off. That's exactly what we designed this kettle for. "
Efficiency is not the decisive criterion
The plant is to be able to store 35 megawatt hours of electrical energy - enough to run the turbine for more than 24 hours. The efficiency, however, sounds rather modest: Just 25 to 30 percent of the electricity used should come out in the end again. But that's not so bad, experts say. Because the stone storage is to be fed mainly with surplus electricity from wind farms and solar systems - electricity so that would otherwise be thrown away, so to speak. The assessment of Jennifer Wagner:
"We assume that at the end of the day not efficiency will be the decisive criterion, but usability."
The new concept could score above all in terms of costs. Because stones are outspoken cheap goods.
"You can find them very often all over the world, the big cost factor is the transport."
Hasan Özdem says - and makes a comparative calculation:
"Not only are our technologies much larger than batteries, they are also ten times cheaper to use."New life for decommissioned power plants?
Batteries are more flexible and can absorb and release energy much faster. By the next summer at the latest, the demonstration plant in the Port of Hamburg should start. The experts hope that it will prove itself - and are already planning significantly larger stone storage. That would be necessary to be able to save economically relevant amounts of electricity, says Jennifer Wagner.
"We made an estimate for a gigawatt-hour investment, which would be the size of a quarter of a football field."
It would even be conceivable to convert decommissioned coal or gas power plants. Then, instead of a coal boiler, a stone storage would make the turbines steam - in the truest sense of the word.
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