Solar module efficiency is what, about 20% at best? Thermal is more like 60%. This means less roof area needed on a house that doesn’t have a lot of solar exposure.
Then there’s cost. With the thermal system I’m planning there will be 40gal of potentially very hot water mixed down to the (lower) maximum temperature of my 40gal electric water heater, which will again be mixed down to the maximum temperature allowed for domestic use. In effect the design will be one battery feeding into another. 'Seems cheaper than lithium batteries, and since this will be a passive system, no controller will be needed.
You also have to deal with a ton of extra plumbing and envelope penetrations, and the space the thermal solar collector takes up doesn’t fit nicely with a solar PV array either. A HPWH might use 800 kWh/year, so thats like less than two 400+ W panels to cover all your water heating. I think thermal solar is fine tech and there are certainly situations where it makes sense (perhaps yours) but overwhelmingly HPWH is more cost effective and simpler.
Solar module efficiency is what, about 20% at best? Thermal is more like 60%. This means less roof area needed on a house that doesn’t have a lot of solar exposure.
So anything above a CoP of 3 and you need less area. That’s pretty doable these days. Maybe read up on how heat pumps work first before making assertions.
Also you can totally store hot water from a heat pump.
Solar module efficiency is what, about 20% at best? Thermal is more like 60%. This means less roof area needed on a house that doesn’t have a lot of solar exposure.
Then there’s cost. With the thermal system I’m planning there will be 40gal of potentially very hot water mixed down to the (lower) maximum temperature of my 40gal electric water heater, which will again be mixed down to the maximum temperature allowed for domestic use. In effect the design will be one battery feeding into another. 'Seems cheaper than lithium batteries, and since this will be a passive system, no controller will be needed.
You also have to deal with a ton of extra plumbing and envelope penetrations, and the space the thermal solar collector takes up doesn’t fit nicely with a solar PV array either. A HPWH might use 800 kWh/year, so thats like less than two 400+ W panels to cover all your water heating. I think thermal solar is fine tech and there are certainly situations where it makes sense (perhaps yours) but overwhelmingly HPWH is more cost effective and simpler.
So anything above a CoP of 3 and you need less area. That’s pretty doable these days. Maybe read up on how heat pumps work first before making assertions.
Also you can totally store hot water from a heat pump.
The main disadvantage is cost and complexity.