District heating using a sand battery as storage for peak demand

https://interestingengineering.com/energy/sand-battery-polar-night-energy

“The net result: Pornainen fulfilled all of its municipal climate targets with a single installation. Oil use dropped 100 percent, emissions fell 70 percent, and woodchip combustion was cut by 60 percent. According to the Mayor of the Municipality of Pornainen, Antti Kuusela, the municipality now heats all its public buildings, including a new sports arena opening in September 2026, entirely through this district heating network.”

Nice.
Necessity is the mother of invention.

But you can't really call it a 'battery' , as it stores heat, not multi-purpose electricity.
Although you could re-purpose the heat above 100^o to heat water into steam and drive generators ( with some losses ), and that last 100^o of water would still have about 5 times the heat capacity of the 100^o sand.

Pretty interesting method of storing energy. At 500-650C, there is plenty of energy to make steam if desired, even enough to turn a turbine. The description does lack somewhat, like, how is the medium heated with electricity? Are there electrodes running through it? Also, is the medium static or does it get hot enough to partially liquify? I would be very interested in seeing blueprints but that is probably out of the question for proprietary reasons or some such.

2 minutes ago, npts2020 said:

Pretty interesting method of storing energy. At 500-650C, there is plenty of energy to make steam if desired, even enough to turn a turbine. The description does lack somewhat, like, how is the medium heated with electricity? Are there electrodes running through it? Also, is the medium static or does it get hot enough to partially liquify? I would be very interested in seeing blueprints but that is probably out of the question for proprietary reasons or some such.

Well it seems to say that the sand is heated by heating air and passing that through large bore ducts within the sand.

It also says that the designers wish to keep it simple which is perhaps why did not use water/steam as MigL suggests since corrosion is a very real problem with steam at those temperatures and special materials ( probab;ly expensive) are required.
Also in the event of a breakdown the pipes will not be damaged by frozen water.

8 minutes ago, studiot said:

Well it seems to say that the sand is heated by heating air and passing that through large bore ducts within the sand.

It also says that the designers wish to keep it simple which is perhaps why did not use water/steam as MigL suggests since corrosion is a very real problem with steam at those temperatures and special materials ( probab;ly expensive) are required.
Also in the event of a breakdown the pipes will not be damaged by frozen water.

Ok, how large is large? 5 cm? 20? 100? What kind of volume/pressure/flow is required?

Also, they say they are building some to make steam. IMO the problems with steam are being overstated, anyway. Every plant in the world that generates power with steam, and there are a lot of them, operates with the same high temperature water constraints.

26 minutes ago, npts2020 said:

Pretty interesting method of storing energy. At 500-650C, there is plenty of energy to make steam if desired, even enough to turn a turbine.

Just for comparison, a primary steam power station will typically produce main steam at 165 barg and 570^oC. This implies 230^o of superheat. The intermediate cycle would be superheated to the same temperature, but at ~60 barg.

Bear in mind that energy content is almost independent of pressure: it's all about the temperature.

19 minutes ago, npts2020 said:

Also, they say they are building some to make steam.

But that's dry saturated steam at 200^oC which just happens to be industry standard for the drying sections of pulp and paper mills, a vital cog in the wheels of the Finnish economy.

No one serious generates power from this quality of steam.

Edited 11 minutes ago11 min by sethoflagos
misprunt