Re:Desalination system could produce freshwater that is chea...
by zbrozek on Thursday September 28, 2023 @12:47AM
(#37685344)
Where are you finding COP for water heaters? The best I found was a field study by the Canadian government where it seemed like most units operating in ambient temperatures relevant for me (in central California) get about 2.5.
Re:Desalination system could produce freshwater that is chea...
by danans on Thursday September 28, 2023 @02:12AM
(#37685911)
The COP is roughly equivalent (but more forgiving) than the UEF rating. Many new heat pump water heaters have a UEF of 4 [1], but this accounts for things like standby losses, so the COP of the heat pump itself is higher than that.
Some premium hot water heaters like the SanCO2 can achieve COP of up to 5.0 [2], so high that they don't need backup resistance elements, even in northern climates.
1. https://www.energystar.gov/productfinder/product/certified-w...
2. https://www.smallplanetsupply.com/small-planet-blog/2021/1/7...
Re:Desalination system could produce freshwater that is chea...
by zbrozek on Thursday September 28, 2023 @11:32PM
(#37698995)
Here's the definition of UEF:
https://www.govinfo.gov/content/pkg/CFR-2016-title10-vol3/pd...
It would be really nice if manufacturers published delta-T vs COP curves.
Right now most people are better off (from a total cost of ownership perspective) with PV panels + heat pump water heater. The latter can achieve a COP of 3.0 (300% "efficiency"), and also can just use grid electricity on a cloudy day. Unless you are off-grid, the additional cost/complexity of running plumbing to the roof for a solar water heater doesn't pencil out.