Large-scale ‘sand battery’ goes online in Finland • Hacker News Board

Re: Large-scale ‘sand battery’ goes online in Finland

#101

Post by tjmc » Thu, Jul 07, 2022, 2:25 AM UTC

WalterBright wrote: post #93

I've proposed several times on HN a "box of rocks" at the house level to store heat/cold when electricity is cheap, and release heat/cold when electricity is expensive. It was ridiculed every time. I should have patented it :-)

HVAC engineer here. At the residential level this is already achievable with hot water storage from either solar thermal and/or heat pumps. Plus you get to use the hot water (assuming you've sized the tank correctly!)

Storing heat in rocks or sand doesn't make sense from a thermal efficiency standpoint unless the temperature is high and that isn't economically viable unless you have large volume storage - typically district or precinct level.

Re: Large-scale ‘sand battery’ goes online in Finland

#102

Post by duskwuff » Thu, Jul 07, 2022, 2:28 AM UTC

jelly wrote: post #64

zmgsabst wrote: post #61

Earlier quoted context omitted.

> gas supplies in question were not covered by sanctions, but Russia tried to unilaterally switch to being paid in roubles I don’t think this is a very honest characterization: Russia demanded payment on their terms only after they were kicked out of SWIFT and their reserves frozen by foreign banks. I don’t think I’d describe that change in payment terms in response to bank sanctions as “unilateral” or unrelated to s…

Gazprombank is still in SWIFT

Given reports that the Russian military may be paying soldiers through Gazprom, that probably won't last much longer.

https://www.rferl.org/a/ukraine-gazprombank-sanctions-funds-...

Re: Large-scale ‘sand battery’ goes online in Finland

#103

Post by jefftk » Thu, Jul 07, 2022, 2:36 AM UTC

dwighttk wrote: post #50

gamegoblin wrote: post #14

Earlier quoted context omitted.

Many American universities use district heating for the whole campus. Also, as made famous by the many steam vents in NYC movie shots: https://en.wikipedia.org/wiki/New_York_City_steam_system . More info: https://en.wikipedia.org/wiki/District_heating#United_States

As the first dorm on the loop my freshman year, I’d get back from crew practice, go into the bathroom, turn on all three showers, and flush the three toilets about three times each to flush all of the hot water out of the cold water line so that I wouldn’t burn myself when taking a shower. I never heard if anyone got hurt when I took a day off and slept in.

Why was the cold water line hot?

Re: Large-scale ‘sand battery’ goes online in Finland

#104

Post by O__________O » Thu, Jul 07, 2022, 2:40 AM UTC

tsol wrote: post #85

rcv wrote: post #65

Earlier quoted context omitted.

> The borehole thermal energy system (BTES) is located underground to store large quantities of heat collected in the summer to be used in the winter. Basically they heat up the soil and rock beneath their park during the summer using hot water/glycol from their solar arrays, and then during the winter they pump cold water through it which soaks that heat back up. What's amazing is that it apparently took 4 years to…

And there isn't a massive amount of heat loss with that? It's a cool idea, what surprises me is that it actually works

Yes, appears so; after looking around, found three additional documents.

(1) 10 year report on the project, which has detailed charts on the performance of the system:

https://www.dlsc.ca/reports/swc2017-0033-Mesquita.pdf

(2) More mathematical explanation of the dynamics of the system, specifically: “Because of their construction principle, BTES are not thermally insulated to the bottom and the side; only a top insulation layer reduces the losses to the environment. As the thermal conductivity of underground material is rather moderate, in a range of 1–5 W/m·K, heat losses can be kept low if the total volume is large enough to achieve a good surface-to-volume ratio. Size is important because heat losses are proportional to the storage surface while the storage capacity is proportional to the volume.“

https://www.sciencedirect.com/topics/engineering/borehole-th...

(3) What is the specification W/mK

https://forum.digikey.com/t/what-is-the-specification-w-mk/3...

Re: Large-scale ‘sand battery’ goes online in Finland

#105

Post by dwighttk » Thu, Jul 07, 2022, 2:41 AM UTC

jefftk wrote: post #103

dwighttk wrote: post #50

Earlier quoted context omitted.

As the first dorm on the loop my freshman year, I’d get back from crew practice, go into the bathroom, turn on all three showers, and flush the three toilets about three times each to flush all of the hot water out of the cold water line so that I wouldn’t burn myself when taking a shower. I never heard if anyone got hurt when I took a day off and slept in.

Why was the cold water line hot?

It was next to the hot water line and not insulated (enough) and it had pretty much just been sitting there all night.

Re: Large-scale ‘sand battery’ goes online in Finland

#106

Post by epistasis » Thu, Jul 07, 2022, 2:41 AM UTC

pavon wrote: post #8

As 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.

This is actually a really good business for natural gas utilities to switch to if they want to survive in the future.

They have tons of experience with pipes, they can swap gas furnaces for heat pumps and exchangers.

And it turns out that the areas that district heating works well with are really comparable to where it makes sense to pump natural gas. Yoi don't necessarily need heated pipes, just using the ambient temp in the ground is usually good, with very small bits of storage/heating.

Re: Large-scale ‘sand battery’ goes online in Finland

#107

Post by nr2x » Thu, Jul 07, 2022, 2:44 AM UTC

thematrixturtle wrote: post #55

excitom wrote: post #43

> It has a particularly strong use case in Finland which sees long and very cold winters, and was recently cut off from Russian gas supplies over a payments dispute. Well I guess that's one way to characterize war-related sanctions and their side effects.

It's factual. The gas supplies in question were not covered by sanctions, but Russia tried to unilaterally switch to being paid in roubles and were told to go batter sand (bada bum tssh).

It’s possible to be factual and dishonest at the same time.

Re: Large-scale ‘sand battery’ goes online in Finland

#108

Post by O__________O » Thu, Jul 07, 2022, 2:53 AM UTC

ggm wrote: post #86

tsol wrote: post #85

Earlier quoted context omitted.

And there isn't a massive amount of heat loss with that? It's a cool idea, what surprises me is that it actually works

London Underground originally was kept cool because of its thermal mass. Over the last 100 years, it has now turned into a giant heat store, and there is an emerging airconditioning problem. I believe its the resistive heating from the trains passing through, over time, plus the sweaty exhalation of millions of people. TL;DR ground heat is remarkably persisting and takes years to dissipate, if deep enough. Coolth, th…

From Wikipedia, “When the tunnels were built the clay temperature was around 14 °C; this has now risen to 19–26 °C”

According to the same page though, the tunnels only add 4% to the heat and humans add 7% — remaining 89% comes from the trains; unless I misunderstood something.

https://en.m.wikipedia.org/wiki/London_Underground_cooling

Re: Large-scale ‘sand battery’ goes online in Finland

#109

Post by epistasis » Thu, Jul 07, 2022, 2:59 AM UTC

ars wrote: post #32

rightbyte wrote: post #25

Earlier quoted context omitted.

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.

It has 80 hours of storage - that's not enough summer/winter shifting. At most it's day/night.

If it discharges continually, it will discharge for 80 hours. 8000kWh / 100kW, capacity divided by discharge rate

This is a different number than the amount of energy lost when it is not discharging. However I would suspect that this particular unit is not designed to store heat for six months.

However there are plenty of underground systems designed for seasonal storage, and the storage capacity is relatively cheap. The problem is getting enough neighbors together to meet the minimum scale.

Re: Large-scale ‘sand battery’ goes online in Finland

#110

Post by zbrozek » Thu, Jul 07, 2022, 3:08 AM UTC

taeric wrote: post #89

com2kid wrote: post #60

Earlier quoted context omitted.

I was thankful, and shocked, the one year of my life that my HVAC system didn't break down in some fashion. Hot water heaters should have leak detectors on them. They often don't. The higher end models do. Product differentiation strikes again. Last water heater I had, the anode was A-OK, I had it checked about a year prior to the water heater failing. Thermal stress destroys stuff.

I've... Never had a problem that was catastrophic in my adult life. Only real issue we've ever had was someone hit the ac unit with their car. Curious what sort of load you put on yours to have such terrible luck.

I had one catastrophic failure and several minor ones. Now I have a tankless water heater.