Solar Assisted Heat Pump Water Heaters
Someone made a comment recently about Sanden/SANCO2 and SAHP being alternatives to the “vertical stack” HPWH units that dominate the North American market.
I had never heard of the SAHP brand, so did some poking around to find out more info; it’s a split system with an integrated outdoor panel and refrigerant lines between the indoor/outdoor units. The panel is black, but that seems to be the extent of “solar assisted”.
I couldn’t find much info about first hour ratings, etc., or much of the normal-ish water heater metrics, but the SAHP seems like a fairly low thermal input from the BTU specs in the marketing literature. Maybe similar to the “vertical stack” units, don’t know.
Does anyone have thoughts about the SAHP products and how they would perform? There’s very little info outside of sales brochures and press releases, and a rather large hole here for any mention of it.
I think we’re missing a discussion here, in the GBA community.
https://www.theradiantstoreinc.com/solar-assisted-heat-pumps
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Anyone have thoughts on these?
Hi Chris,
Sorry you haven't had any luck getting a response. Perhaps nobody who has seen your question has experience with these. Interestingly, I have a connection to the developers of the Hillside Center for Sustainable Living featured on the website you shared. If you'd like, I can try to connect you with one of them to talk about the SAHP system they used there. Let me know.
I recently contacted them about info, and talked to a stateside supplier (the radiant store). The info I got was that they don't have a traditional COP rating like we use in the states, but the estimate is around 3 even in below freezing temps when the sun is shining. The panel seems to output 4.4-4.8kw on sunny days. However, if you use water in the evenings, you'll be relying mostly on the resistance element to reheat the tank. There is no info on the efficiency of the heat pump without sunlight.
My thought was, if the best case is a COP of 3, and only for daylight water use, that's not great.
The advantage is that it does qualify for the solar tax credit. It's about $3500 for the smaller 200L unit. The only difference with the larger one is the tank size, same heating capacity.
The reminds me of the old ground source heat pump systems that used refrigerant tubing in the ground. They were a disaster and the companies making them went bankrupt. This isn't quite as bad an idea, but it still adds many more possible points of failure to the refrigerant system, which irresponsible given the climate impact of refrigerant leaks. Better to provide the solar assist to a conventional heat pump water heater with a PV panel, and if you want even better efficiency, add a drain water heat recover system.
I work with one of the two US distributors (New England Solar Hot Water, in Canton, MA. Radiant Store is the other). Thought I’d chime in on a couple of the comments;
1. The heat pump capacity varies as a function (mostly) of the outdoor conditions. 1.25kw to 2kw, roughly.
2. Most households leave the ‘back up’ resistance elements off 365 days/yr. HW usage in the evening (or any other time) does not cause the resistance element to come on. The electric element is used for periods of very high hw usage only.
3. The unit has refridgeration lines running from the tank to the evaporator panel outside. There are no additional points of failure of relative to a mini split. Less risk, actually, as the refrigerant is much lower pressure than r410a, and these systems are much simpler with a fraction of the components.
Thank you!
Cool, thanks for the firsthand insight. Are they really as quiet as the 41 dB(A) rating would suggest? That's crazy quiet.
If the max HP output is 2kW, that may equate to roughly 10 gal/hr recovery...?
I struggle with that, but I think that's because I don't have any experience living with a HPWH yet. Normal rules apply I would imagine, with up-sizing the tank to hedge against the lower recovery time.
Out of curiosity, any idea of how many units are out in the wild in North America?
1. There are about 400 installed in North America.
2. Recovery is slow. But as with any slow recovery hw heater (straight electric tank, hybrid, or conventional solar hw), the tank has to be properly sized- if the household runs out of hot water, then the tank was sized incorrectly. There are certainly larger sized households where we simply tell folks that a SAHP (or even a non-solar hybrid wh) is not appropriate. Generally, the largest unit (79 gallons) is good for a household of 5 or 6.
3. They’re very quite. There’s no fan. Just a little compressor.
The primary benefit of these is that they do not consume air from the interior, conditioned, space. A ‘hybrid’ hpwh may have a nominal COP of 3 or 3.5, but in the winter they’re imposing additional load on the space heating while expelling cold air.