Alberta has a neighborhood that stores heat in the summer for winter use:
Large-scale ‘sand battery’ goes online in Finland
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Re: Large-scale ‘sand battery’ goes online in Finland
#22What's the round trip efficiency of something like this, and what's the rate of loss to the environment? There's been a couple of these posted in the last few days and I have no feel for these numbers.
The RTE of turning electricity into heat (or hot water into hot sand into hot water) is pretty good, most of your problem will be environmental losses between the heating station and the end-users.
It's not going to be as good as a heat pump, but they don't work very well in very cold climates, and storing electricity (or energy that you turn back into electricity) is expensive/lossy/difficult.
Re: Large-scale ‘sand battery’ goes online in Finland
#23Why sand? - water has 5x the specific heat capacity of sand - water can be pumped around easily - water can be used directly for district heating
Sand is non-corrosive and doesn't expand significantly at 500C (it takes temperatures ~3x that to get it to melt). That doesn't answer the "why" completely, but those are probably some of the factors.
Edit: the article doesn't explain how the "battery" works, but my intuition is that the sand doesn't move. It's likely merely heated and then passively heats whatever actual transportation medium is used (likely water).
Re: Large-scale ‘sand battery’ goes online in Finland
#24Why sand? - water has 5x the specific heat capacity of sand - water can be pumped around easily - water can be used directly for district heating
Presumably, because sand can be heated to above 100C.
Given Newton's law of cooling, it's not entirely clear to me why you want your thermal battery to be heated to above 100C... But I'm not an engineer - I only play one on TV.
Re: Large-scale ‘sand battery’ goes online in Finland
#25The whole thing seems so inefficient but I am not an expert. Can anyone here expand on this?
You can sink solar power into it in the summer and use the heat in the winter.
With intermittent power like solar and wind you probably want to be able to sink it somewhere useful.
Re: Large-scale ‘sand battery’ goes online in Finland
#26As an American it completely breaks my expectations that district heating not only works can be more efficient that decentralized heating. The amount of heat lost just moving water from the water heater on one side of the house to the shower on the other is ridiculously high in houses here. The idea that you can insulate well enough to efficiently move heat across a city is amazing to me.
As a German living in a city with mandatory district heating... the end result is to be that people seem pay more for heating than they would with a decentralised system. I think that's mostly due to the high upkeep costs of the system, though, the transmission loss is quite manageable, I think. Of course there are arguments to be made that when accounting for the cost of installing a heating system, and the space it…
> What's nice about it, and maybe hard to quantify, is how this limits air pollution in the city.
It should be simple to quantify. If gas is used for heating I can't think there would be any improvement.
Local heating with a heatpump would be an improvement if the power supply mix is greener than gas only, maybe worse if the power is all coal.
Re: Large-scale ‘sand battery’ goes online in Finland
#27Why sand? - water has 5x the specific heat capacity of sand - water can be pumped around easily - water can be used directly for district heating
My guesses:
- Water would either require a tremendous sized reservoir, or infrastructure capable of withstanding the pressure of superheated steam
- superheated steam, and even water to an extent, has corrosive chemistry. Sand is basically inert.
Those are just guesses though. I'd love an engineer who works on this to break down the real reasons.
Re: Large-scale ‘sand battery’ goes online in Finland
#28As an American it completely breaks my expectations that district heating not only works can be more efficient that decentralized heating. The amount of heat lost just moving water from the water heater on one side of the house to the shower on the other is ridiculously high in houses here. The idea that you can insulate well enough to efficiently move heat across a city is amazing to me.
As a German living in a city with mandatory district heating... the end result is to be that people seem pay more for heating than they would with a decentralised system. I think that's mostly due to the high upkeep costs of the system, though, the transmission loss is quite manageable, I think. Of course there are arguments to be made that when accounting for the cost of installing a heating system, and the space it…
I find district heating in Copenhagen to be good value, and it seems to be a good deal greeted.
https://celsiuscity.eu/district-heating-prices-highly-compet...
Re: Large-scale ‘sand battery’ goes online in Finland
#29What's the round trip efficiency of something like this, and what's the rate of loss to the environment? There's been a couple of these posted in the last few days and I have no feel for these numbers.
Data from Drake's Landing in Aberta has a COP of 30 (30kw of heat per kw of electricity)? The heat stored is waste heat - otherwise lost to the atmosphere, so storing it until use is should be compared to typical heat pump COP of 2-4.
Re: Large-scale ‘sand battery’ goes online in Finland
#30As an American it completely breaks my expectations that district heating not only works can be more efficient that decentralized heating. The amount of heat lost just moving water from the water heater on one side of the house to the shower on the other is ridiculously high in houses here. The idea that you can insulate well enough to efficiently move heat across a city is amazing to me.
My hometown has a power plant in city center. During winter it uses the entire downtown area as a heat sink. It's great. Power plant gets cooling for its hot water, city residents get cheap heating for their homes. Best part is you don't even care about heat loss because you're trying to get rid of all that heat anyway. This scheme has been inplace since the 60's. https://en.wikipedia.org/wiki/Ljubljana_Power_Station…
Given how much health problems are caused by coal power plants, not sure it is that great to live near one.
But if you have to have coal, it makes good sense to harvest the energy rather than wastefully pumping the steam into cooling towers.