The Anonymous Widower

Siemens Gamesa Begins Operation Of Its Innovative Electrothermal Energy Storage System

The title of this post, is the same as that of this press release from Siemens Gamesa.

This is the introductory paragraph.

In a world first, Siemens Gamesa Renewable Energy (SGRE) has today begun operation of its electric thermal energy storage system (ETES). During the opening ceremony, Energy State Secretary Andreas Feicht, Hamburg’s First Mayor Peter Tschentscher, Siemens Gamesa CEO Markus Tacke and project partners Hamburg Energie GmbH and Hamburg University of Technology (TUHH) welcomed the achievement of this milestone. The innovative storage technology makes it possible to store large quantities of energy cost-effectively and thus decouple electricity generation and use.

This second paragraph gives a brief description of the system.

The heat storage facility, which was ceremonially opened today in Hamburg-Altenwerder, contains around 1,000 tonnes of volcanic rock as an energy storage medium. It is fed with electrical energy converted into hot air by means of a resistance heater and a blower that heats the rock to 750°C. When demand peaks, ETES uses a steam turbine for the re-electrification of the stored energy. The ETES pilot plant can thus store up to 130 MWh of thermal energy for a week. In addition, the storage capacity of the system remains constant throughout the charging cycles.

This system is a pilot plant and will test the system thoroughly.

They state that the long term aim is to store energy in the gigawatt range and be able to provide the enough power for the daily electricity consumption of around 50,000 households.

The method of energy storage would appear to be inherently simple.

• Heat rocks to a high temperature using a gigantic electric heater and blower.
• Use the heat when required to boil water to create steam.
• Pass the steam through a conventional steam turbine.

I can envisage a clever computer system, controlling the hot air and water flows into the vessel to get the correct level of steam out, as needed for the amount of electricity required.

I suspect the biggest problem is where do you keep a thousand tonnes of hot rock?

The answer is given in this article on the American Society of Mechanical Engineers, which is entitled Heated Volcanic Rocks Store Energy.

This paragraph describes the storage.

A key finding from an earlier, smaller project proved greater efficiency of a round shape for the container holding the rock. It has an increasing diameter on both ends, where inflow and outflow openings are located. It has a total content of 800 cubic meters of rock with a mass of 1,000 tonnes, covered with a one-meter-thick layer of insulation.

I estimate that the diameter of a 800 cubic metre rock sphere would be just 11.4 metres, so perhaps around fourteen with the insulation.

The sphere would need to be a pressure vessel, as it would contain high-pressure steam.

The process looks to be simple, efficient and scalable.

The article also makes the following points.

• Eighty percent of the components are off-the-shelf.
• There are no hazardous materials involved.
• High efficiencies are claimed.
• Siemens Gamesa are aiming for a 1 GWh system.
• The German government has provided development funds.

It is being built on the site of an old aluminium smelter, so I suspect, the site has good connections to the electricity grid.

In the early 1970s, I was involved in the design and sizing of chemical plants for ICI. In one plant, the process engineers and myself proposed a very large pressure vessel, that would have been larger than the one, Siemens Gamesa are using in Hamburg. But then the domes of pressurised water reactors, like this forty-six metre diameter example at Sizewell B are even larger.

 

I very much believe, that design and construction of the pressure vessel to hold the hot rocks for Siemens Gamesa’s system could have been performed by the team I worked with in 1972

How Big Would The Sphere Be For A One Gigawatt-hour System?

• The current pilot system has a 130 MWh thermal capacity and uses a thousand tonnes of volcanic rock.
• The rock occupies 800 cubic metres.

I estimated that the pressure vessel with insulation could have a diameter of fourteen metres.

A system with a 1 GWh thermal capacity would be 7.7 times larger.

• It would need 7,700 tonnes of volcanic rock.
• The rock would occupy 6,160 cubic metres.

I esimate that the pressure vessel with thermal insulation would have a diameter of twenty-five metres.

How Much Power Could Be Stored In A Sizewell B-Sized Dome?

Out of curiosity, I estimated how much power could be stored in a pressure vessel, which was the size of the dome of Sizewell B power station.

• The dome would have a diameter of forty-two metres if the insulation was two metres thick.
• This would store 39,000 cubic metres of rock.
• This would be 48,750 tonnes of rock.

Scaling up from the pilot plant gives a 6.3 GWh thermal capacity.

I would suspect that Siemens know an engineer, who has worked out how to build such a structure.

• A steel pressure vessel wouldn’t be any more challenging than the dome of a pressurised water reactor.
• It would be built in sections in a factory and assembled on site.
• Rock would probably be added as the vessel was built.

I can certainly see one of these energy stores being built with a multi-gigawatt thermal capacity.

Would This System Have A Fast Response?

Power companies like power stations and energy storage to have a fast response to sudden jumps in demand.

This section in the Wikipedia entry for Electric Mountain, is entitled Purpose and this is said.

The scheme was built at a time when responsibility for electricity generation in England and Wales was in the hands of the government’s Central Electricity Generating Board (CEGB); with the purpose of providing peak capacity, very rapid response, energy storage and frequency control. Dinorwig’s very rapid response capability significantly reduced the need to hold spinning reserve on part loaded thermal plant. When the plant was conceived the CEGB used low efficiency old coal and oil fired capacity to meet peaks in demand. More efficient 500 MW thermal sets were introduced in the 1960s, initially for baseload operation only. Dinorwig could store cheap energy produced at night by low marginal cost plant and then generate during times of peak demand, so displacing low efficiency plant during peak demand periods.

Given that we are increasingly reliant on intermittent sources like wind and solar, it is surely getting more important to have energy storage with a fast response.

Consider.

• Gas turbine power stations are very quick to start up, which is a reason why, they are liked by power companies.
• As Wikipedia says pumped storage systems like Electric Mountain usually have a fast response.
• Lithium-ion batteries have a very fast response.

I think the Siemens Gamesa ETES system could have a medium-fast response, provided there was enough heat in the rocks to raise steam.

Could This System Be Placed In A Town Or City?

Consider.

• The system doesn’t use any hazardous materials.
• The footprint of a 1 GWh system would probably be football pitch-sized.
• The system could probably be designed to blend in with local buildings.

This picture shows the Bunhill 2 Energy Centre in London, which extracts waste heat from the Underground and uses it for district heating.

When I took the picture, the system wasn’t complete, but it shows how these types of developments can be fitted into the cityscape.

 

 

May 15, 2020 - Posted by AnonW | Energy Storage | Bunhill 2 Energy Centre, Siemens Gamesa ETES