Solar water heaters were cool in 1980s. They could be again. : technology

[–] poVoq 13 points 9 months ago (1 children)

They are still cool. I just recently installed one :)

The vacuum tube ones are IMHO the best, but there are also ones that circulate a heat exchange fluid in panels for direct connection to a heat-pump. The advantage of the latter is that you get good efficiency out of them in the winter, but it also means that the heat-pump has to run all the time. My vacuum tubes work fine most of the year with only a small circulation pump running (and smaller systems with a thermo-siphon don't even need that).

[–] SpaghettiYeti@lemmy.world 2 points 9 months ago (1 children)

What did you end up spending for it? Are you using it paired with an existing hot water heater?

[–] poVoq 1 points 9 months ago

It's combined with a stand alone air-to-water heat-pump that shares a hot water storage container with the solar thermal panels. Prices are hard to compare and I actually got a small government subsidy for it as well, but the solar thermal vacuum tubes alone should be less than $500 for a typical family home.

[–] benjhm@sopuli.xyz 6 points 9 months ago (1 children)

We have one, it works reliably for many years, even in winter when there is sun - problem is sunny days are too rare here from Nov to Jan. If you get one, get a big tank, and optimise setup for winter (low sun angle), more than enough hot water in summer.

[–] anothercatgirl@lemmy.blahaj.zone 1 points 9 months ago* (last edited 9 months ago) (1 children)

yeah, a very big tank (more than 2000L) of warm water can last a few days which is important for intermittent sunlight.

[–] boonhet@lemm.ee 4 points 9 months ago* (last edited 9 months ago) (3 children)

How big are we talking here, really? Or should insulation be considered too?

I have two tanks in my house that are heated by different elements of the (fossil fuel based, unfortunately) heating system - the stove and the furnace, which used to burn coal, but now we're doing wood and briquettes.

Either one of those can be heated to near boiling temperatures in about an hour, carry about 100-150 liters of hot water, but sadly will cool down over less than 24 hours so if it's freezing, but not "fuck my balls are going to fall off" freezing, I have to use the electric boiler at great expense. But both of those are bare metal tanks, no insulation at all AFAIK.

PS: House was built by grandparents, I'm too broke to put 10-30 grand on either an air to water or ground to water heat pump right now, but if anyone's interested, I can tell horror stories about the current heating system and house altogether. Soviet era design choices and modern prices for literally everything make for an uh... interesting combination. When it hit -28C (around -18F), I was up all night fueling the furnace, literally feeling myself burn through money.

[–] JacobCoffinWrites 2 points 9 months ago (1 children)

I'm definitely interested, for what it's worth. I've lived in some old houses with head-scratching design choices (though mostly around the wiring) so I sympathize

[–] boonhet@lemm.ee 3 points 9 months ago* (last edited 9 months ago) (1 children)

Welcome to my personal hell!

The house is divided into 5 semi-floors, but of those, one is basement level, and another is halfway underground. There are 3 above-ground floors. The entire thing is heated mainly using a furnace in the basement that drives hot water into the radiators and also a hot water tank that by default always runs into the toilet sink, but a switch can be made to use it in the other faucets too. Otherwise, the upstairs bathroom has its' own electric boiler, that can also be used downstairs in the kitchen, and also the sauna, but for it to run into the kitchen, you'd have to switch around some valves again - otherwise the kitchen and sauna use hot water from the stove in the kitchen, which also has a massive tank. The stove tank I believe is the only one that can't be used in the upstairs bathroom. I'd also like to add that there used to be a separate tank in the sauna that got its' heat from the sauna furnace and ONLY heated water for a single faucet in the sauna, but NOT the shower in the sauna. That's been gone a long time, because there was no real need for a faucet there, you can just get water out of the shower which has a faucet attachment anyway.

Now, insulation. The house has a total of 5 big windows and 10 small ones. The big ones are now double or triple glazed (they weren't all done at the same time, so 2 are double glazed), the small ones have two single pane window panels, which does technically create an air gap, but all the windows leak hair like crazy. The walls themselves are actually well insulated I believe. But the roof has been insulated using sawdust. Naturally, mice have carried it all away, there's none left. But also the upper half of the roof leaks water, so I can't add new insulation to that half until the roof's fixed. Also it's lined with asbestos-cement panels, so those are going to be fun to remove. Luckily the lower half was repaired years ago.

The kicker? The house being as big as it is, the furnace is absolutely massive and burns through wood like there's no tomorrow. It's meant to be used with long-burning coal, which was cheap in the soviet times. Now it's expensive and hard to find, so the heating benefits don't really outweigh all the drawbacks anymore.

Ah and if it gets really cold, there are two additional fireplaces I could make a fire in. You know, in addition to the furnace, stove and sauna.

Do I want a ground-source heat pump with under-floor heating? Hell yeah. Is it feasible? Not even close. The yard isn't big enough to fit a horizontal collector big enough for the house and I'm not sure I could have deep enough holes drilled for vertical ones. And even if I got the heat pump, it'd have to heat the existing radiators, because I'd simply lose my sanity installing under-floor heating here.

[–] JacobCoffinWrites 2 points 9 months ago

That's kinda amazing. I'm impressed by the number and variety of heat sources, and the way they're all kinds tangled together. Also the range of technologies used in the construction and heating. Thank you for sharing all this!

[–] poVoq 2 points 9 months ago

Some basic isolation will definitely help, as does a behaviour change from showering in the evenings as opposed to the mornings.

IMHO expecting the heat to last several days is unrealistic, but you should have a tank sufficiently sized for allowing all your family members to shower and then some, as the heat doesn't get produced on demand. 300-500 liters is normally more than sufficient.

For my system I get some heat out of it even on cloudy days and then use the heat-pump to top it off to a nice shower temperature. But again this requires to wait for the evening to shower.

Also realistically speaking, in climates with strong freezing temperatures the risk of the system freezing and breaking is quite high and you probably really do not get much out of it in the winter, so maybe it's not the best solution for such climates.

[–] anothercatgirl@lemmy.blahaj.zone 1 points 9 months ago

Yeah I meant a lot more water than that. Could do the math when I get home...?

[–] Flumpkin 6 points 9 months ago

Due to economics, using photovoltaic solar panels and an electrical heater is actually cheaper. Which is a bit stupid of course. I think water heater are more compact but more expensive. And they need a pump and a heat pump and more maintenance with moving parts and antifreeze etc.

[–] JillyB@beehaw.org 3 points 9 months ago

Tech Ingredients made a great solar water heater and showed how to do it

[–] CounselingTechie 1 points 9 months ago

I have tried to think about the feasibility in installing a solar water heater on a monolithic dome styled house.

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