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Climate Change / Global Warming Discussion
- Thread starter Raffy.Roma
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mspohr
Well-Known Member
It's basically a refrigeration unit. Lots of those have a long track record.Hopefully that will continue
nwdiver
Well-Known Member
I HAAATE Solar Thermal. Anyone selling Solar Thermal these days is either ignorant or running a con. Back when PV was $10/w it made some sense. You can get a heat pump water heater for ~$1200 that reduces your energy use by ~70% (the remaining 30% is easily covered by <$500 in PV) OR a solar thermal water heater that reduces your energy use by ~95% (Still need backup heat occasionally) for ~$5k...
Option 1 is less maintenance and you can export the surplus energy. Option 2 is just absurd compared to option 1.
WannabeOwner
Well-Known Member
Errmmm ... a single evacuated tubes panel (big enough for domestic hot water for a family - 1.7M x 2M, Peak 1.1kW) here is $500. Some plumbing required, but that's not going to be anything like $4,500 ... but for any situation that required long pipe runs [to domestic hot water tank / pool] it is usually regarded as pointless (pipe-cost, and the "start heat penalty" as the panel tips over the set-temperature then almost immediately stops as the cold water from the panel-to-tank-and-back returns to the panel. That also dumps the same cold water into tank too of course ... it probably only takes "some tens of minutes" on a long run to turn from negative into positive ... but our Winter is 10x less solar insolation than Summer, so nothing useful in Winter (fair enough) but this cycling becomes an edge-issue as Autumn progresses, and when Spring starts. You can add bypass-to-tank to stop the cold water getting into the tank, but that's even more "complexity & cost" to go wrong / need repair. Domestic hot water tank, in the UK, is usually upstairs, sometimes even in the loft, so pipe runs to roof are short enough in the majority of houses.
250W PV panel here is $120-ish ... needs fitting to the roof (Solar Thermal is one panel, dunno how many PV panels equivalent that is (converting solar therma gain to electricity + heat pump? several I suppose?) and cost of inverter and heat pump too ... so I'm struggling to get the capital cost anywhere near par.
But if I have to get a plumber out once a season because the Solar Thermal has air in it, and if the anti-freeze has been wrecked because of excess temperature in the interval between me noticing its not working (rubbish controllers with no Data Freed type stuff, to keep the cost down, so I have to actually "notice" its not working) and plumber's visit then have to recharge and flush through the whole system. Probably a 4 hour visit ... my "saving" on Solar Thermal is out the window at that point.
Over here we fit flexible "corrugated" pipe from tank to panel, and it's the joints between that and regular pipe that seem to let the air in IME.
Also a good idea not to let it overheat - so when the domestic hot water tank is full what then as a "heat dump"? We have a 5,000L accumulator (normally heated by wood fired boiler, which in turn provides source for winter central heating and pool in summer, and also pre-heats mains-water before it goes into domestic hot water tank), but the only other houses that I know of, in UK, with accumulators like that are nutcases like me!
Pool is an easier call for Solar thermal - sun comes out, solar loop pump comes on, through heat exchange, pool circulation triggered so filter-and-heat whilst the sun is out. We have PV too, so power for the pumping is "free" and the cycles all come on together. We only filter the pool when the sun is out, and never have a problem with water quality ... (this is UK
).But I still think, for pool, that PV + Heat Exchanger wins on reduced maintenance cost. Pool only needs low-grade heat, so ideal for Heat Pump.
Its 10 years since I installed Solar Thermal and Wood-fired boiler, so much may have moved on, but I'd be very interested to hear about models of Heat Pump that can lift water temperature to 60C (and have a decent COP). 60C is fine for domestic hot water, but we need hotter than that for central heating radiators. Underfloor Heating, which we also have in new parts of the house, is fine at 40C ... but sadly most of our house is radiators and retro fit of under floor heating in the "impossible" category, sadly.
We ruled it out here because in winter we don't have enough Sunshine, and Heat Pump needs 3-phase supply, and domestic houses are not fitted with 3-Phase in UK (its common on continent though), and electricity company has a monopoly on fitting that, so it is often several $n0,000 to just have 3-phase supply fitted (even though 3-phase supply is typically available nearby... e;.g. a street is wired from 3 phase, and every 3rd house on the same phase [Single phase is 240V here in UK])
nwdiver
Well-Known Member
I only know what I've seen. A co-worker paid $7k a while back for a solar thermal system. She got conned.
This doesn't include installation... areas that need freeze protection (pretty much the entire US) add a lot of complexity...
WannabeOwner
Well-Known Member
OK, so that's new hot water tank too. A taller-tank has better thermal layering of course ... but either may not be necessary, or the existing tank ready for replacement anyway (and taller tank better even if using some other heat source).
My supplier is not listing a kit including tank ... but without tank it's $1,500 (excluding sales tax, but in the UK pretty sure that installation qualifies for rebate on some/all of that)
High-Spec Solar Kit for the Professional Installer - 4720
Posh replacement thermal cylinder is about $500 - but we would normally just fit a solar-coil in existing cylinder (unless it was knackered anyway)
Vented Cylinders - Solar Hot Water Cylinders | Navitron
Add the two together and I'm still half the USA price - I wonder why that is? - tariffs perhaps?
Anyway, we are agreed that Solar Thermal is more likely to be done-better by PV + Heat Pump - but for me its not just the price
My supplier is not listing a kit including tank ... but without tank it's $1,500 (excluding sales tax, but in the UK pretty sure that installation qualifies for rebate on some/all of that)
High-Spec Solar Kit for the Professional Installer - 4720
Posh replacement thermal cylinder is about $500 - but we would normally just fit a solar-coil in existing cylinder (unless it was knackered anyway)
Vented Cylinders - Solar Hot Water Cylinders | Navitron
Add the two together and I'm still half the USA price - I wonder why that is? - tariffs perhaps?
Anyway, we are agreed that Solar Thermal is more likely to be done-better by PV + Heat Pump - but for me its not just the price
This is a timely (for me) albeit somewhat off-topic discussion. I had to remove my old ground-mount solar thermal panels for my swimming pool last year and was planning to replace them with roof-mount solar thermal this month. The idea of solar PV --> heat pump --> warm pool water never really occurred to me because it seems an inefficient transfer of solar energy. However, thanks to recent posts, I'm starting to understand potential benefits:
I see it as a complicated solution for household hot water, but for something that's somewhat optional like a pool, what are the other arguments I should be considering?
- Solar PV is operational even when not heating the pool, although that's in low-producing months October-April.
- Less maintenance/no winterization and draining panels.
- Ability to heat the pool from grid or batteries even when solar exposure isn't great enough for solar thermal to be effective
I see it as a complicated solution for household hot water, but for something that's somewhat optional like a pool, what are the other arguments I should be considering?
SageBrush
REJECT Fascism
Yup.
The difference in price is even more stark in practice because the DHW is a marginal cost to the PV system in place for cars and home electricity. And unfortunately the solar thermal systems have a lot more (read: expensive) upkeep than PV. Solar thermal is one of those things that sounds like a good idea but the reality is actually fairly poor.
Heat pumps are awesome and they appear to have a bright future of improvement. And when they also act as dehumidifiers in the summer they are another 2-3x better. I'm looking forward to integrated systems that optimize heat transfer to the best times of the day. Along with better building that emphasizes insulation and low leakage with HRV for air quality adds up to inexpensive, energy efficient, no pollution results.
Regarding DHW, our current behaviors are retarded. 50% of heat can be conserved via simple counter current heat transfer and an optimized heat pump can have a yearly COP of 3-4. That works out to heat use of 10-15% of typical today.
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SmartElectric
Active Member
Counter argument / example:
Put in 10 solar thermal panels 12 feet x 4 more than 10 years ago.
Mounted beside pool on ravine.
No maintenance. Perfect. Total cost was $3000 Canadian installed with electronic automated valve and controller.
Heats our 32x16x8 foot deep pool to 85 F from June to September in Ontario Canada.
Put in 10 solar thermal panels 12 feet x 4 more than 10 years ago.
Mounted beside pool on ravine.
No maintenance. Perfect. Total cost was $3000 Canadian installed with electronic automated valve and controller.
Heats our 32x16x8 foot deep pool to 85 F from June to September in Ontario Canada.
SageBrush
REJECT Fascism
SmartElectric
Active Member
No. When it's cold outside, no one wants to swim in the pool.
Solar PV drops to fraction of summer, but even so I will DIY a few kW of panels this year to offset our mid day peak usage as I have a teired rate of 24c peak and 2c /kWh overnight.
WannabeOwner
Well-Known Member
In my case yes (but UK is at same latitude as Canada so very little solar insolation in Winter). I have heat exchanger for pool, and also an either/or valve connecting direct loop off the solar circuit to a long copper pipe in the conservatory, so any heat available helps the plants (brought in to overwinter). Whether it was worth even installing I don't know! And if I had put PV in instead then the "deployment" would be much more versatile.
If I had no maintenance mine would be perfect too. Same installer did a Solar Thermal for my Father in Law at the same time as me (for DHW) and he's never had a problem, that's about 10 years.
mspohr
Well-Known Member
Heat pumps aren't terribly effective under about 50F. Overnight may not work well, depending on nighttime lows. I know where I am it goes below 50 regularly in summer nights.
mspohr
Well-Known Member
SageBrush
REJECT Fascism
That varies a lot by heat pump, and so far as I know by refrigerant. The Japanese have been selling CO2 filled heat pumps for a couple of years now with very impressive COP values
E.g. this Sanyo reports COP of
3.75 at 20C
3.1 at 7C
1.8 at -15C
And here is a chart for the Sanden:
COP of 3.1 at 23F
COP of 2.0 at 5F !
Good use for CO2.
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mspohr
Well-Known Member
Global warming will depress economic growth in Trump country
Global warming will depress economic growth in Trump country | Dana Nuccitelli
Global warming will depress economic growth in Trump country | Dana Nuccitelli
SageBrush
REJECT Fascism
Don't worry about it. They'll take it as confirmation that god is angry with the liberals.
Huh. I thought global warming started in the 1850's according to experts. Aren't there term limits?
I don't think it stated that climate change would cause issues due to how residents voted. It just suggests that the geographic locales slated to be more directly impacted happen to be "red" states.
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