It's not exactly new, there's been a few projects looking into using gravel or sand as a thermal battery. I remember a video about a project in where they were testing different media to see how they performed
I think the eventual goal is STES (Seasonal Thermal Energy Storage) where you warm up your thermal battery in summer using excess energy and use it in winter when it's needed
To do that you need a lot of heat and something extremely stable and cheap to store it in, hence why they're looking at stuff like sand, gravel or even building rubble
I heard there was also a chemical version where they'd heat up some salt to turn it into a solid and then when they add water the reaction is exothermic to create heat
It's a great idea when combined with district heating, which personally I think should be mandatory in every new estate
For example near me the council is building some new all weather pitches. Not hard to imagine putting a concrete lined tub underneath and filling with sand or gravel and a water pipe network like a GSHP
If there was a district heating system put in place along with a fair amount of solar PV then the council could buy the excess solar in summer, use it to heat the storage battery, and then discharge it in winter in the form of district heating
Could even use wind energy from the grid to supplement the energy demand.
My personal favourite idea would be to use the district heating for cooling as well as use the heat battery as a giant heat sink instead of dumping all that heat energy into the atmosphere
The economics are dodgy as hell however. Much like district heating it's an idea which only works at scale and is quite a risk for anyone investing into it.
Also with any community system there's always going to be nimby's and naysayers who will try to block any system being installed
Thermoelectric generators are either solid state, complex and awful (seebeck/peltier) or are steam turbine based and require huge amounts more kit to implement.
Yeah especially when community schemes get mentioned
Part of the problem with them is that they're only really viable if you get a majority of the people in the area to sign up. If that doesn't happen then the costs are shared among a small customer base and it's unaffordable
And between Nimby's and general aversion to good ideas in this contry you can be sure you'll struggle to get people onboard
Possibly the only way to make it work would be a council run scheme of some sorts. For example where I live the council could install a couple of big thermal batteries and run heating pipes under all the roads in the nearby estates
The cost for this could be built into property tax and connection fees could be made free for the first few years. Since residents are basically paying for the system already, then a lot of people would be quick to sign up
Chuck a decent local grant on top for Solar PV and heat pumps and all of a sudden you've a viable district heating system powered by renewables, which can also make some income for the local council
Those community heating schemes work pretty well on the continent, Germany/Poland esp. Technically no reason why we could do the same. Course, you need the public to "buy into it" as you say, and that's a challange in this place.
Too much "ahh but sure i want to do my own thing"..... but I digress from the sand battery point.
