> It is fair and reasonable to demand that environmental regulation justify its existence with hard, scientifically verifiable data or else get chopped
Here is a strawman for you: studies for regulation A show that it is successfull in improving habitat for endangered species.
Studies also show that the regulation increases tax burden and decreases competitiveness of national agriculture.
That's the whole point of this, no? Heat pumps can't heat up a large amount of water quickly (like resistive heating can). So if you have a solar peak at noon, where either yourself are producing cheap solar, or there's cheap solar on the grid in general, then you want to use that cheap energy to store heat for later use (like showers in the evening/morning).
So the way I see it, is that this material should be able to quickly store heat with the using the low temperatures that heat pumps provide, and be able to store it with minimal losses until it is needed.
> Heat pumps can't heat up a large amount of water quickly
No, it's about temperature difference. My heat pump water tank heats about as quickly as resistive water tanks; but it could never heat to hundreds of degrees.
Does heating water in a boiler work well with a heat pump? How about a release of energy 10 hours later (peak solar at noon, to first shower the next morning)?
I actually don't know the answer. I'm just thinking that there must be more to it, if the answer was as simple as "just heat water".
It does. However, the hotter the water becomes, the less effective the heatpump becomes. With anything beyond 60C becoming very inefficient.
With hot water tanks, they are unfortunately pretty badly insulated as well, with some of them loosing heat very quickly. Depending on how you plan on using that water, you also have to make sure the temperature never dips below ~60C to avoid legionella from spreading.
I actually think that heating your home slighly higher than you‘d usually do is the simplest and most effective approach, assuming it is properly insulated. Just rise the target temp for 1-2C when the energy is cheap and reset it once it isn‘t. Probably not as efficient, but extremely simple to implement.
I have two heat pump water tanks, one Rheem and one AO Smith (our local utility heavily-subsidizes these, with a net-cost less than a standard tank water heater).
They both are rated for annual kWH usage less than the US EPA yellow label can display (for their category of tanked water heaters, i.e. competing mostly with resistive heating models).
Annually water heating is about 3% of my energy consumption.
The AO Smith (retail $1678) cost $250, after rebates (available to all SFH in any of TVA's power sellers, typically between Thanksgiving and NYE). With rebates the Rheem was $1000 (and is two years older).
Without rebates, they're similarly priced.
As far as reliability, they both have decent warranties and backup heating elements. Both heat water without internet connectivity. Similar performances (as far as heat output).
Overall, I feel the AO Smith is more customer friendly. Definitely easier to install:
1) AO has both top and side water connections; Rhm has one top and then one side connection (why?!)
2) AO's venting connections are far superior to Rheem's (which require custom/expensive adapters if installed in spaces <700sqft) — AO just has two standard 8" duct connectors on top... so much easier/cheaper to install into a closet. Rhm's top slit needs a $120 plastic adapter, and then ejects to the side (of a 24"D cylinder) [again: why?].
3) Rheem will not stay in ELECTRIC-HEAT (only) mode, for longer than two days — it automatically reverts to the prior heat pump option (which is annoying; you can use the app and set up a schedule to "force" electric mode... but then you have to use an app). AO stays in whichever mode you select.
4) AO is just nicer presentation. Despite a few obviously less-expensive components and design decisions... the AO is better thought-out. Just as an example, the Rheem has a threaded 3/4" socket for condensate, while the AO has a pre-installed (cheaper, too) drip tube.
5) The AO's electric vault is on the side (and not top) so a top leak is less likely to fill the conductors // corrosion. This is a better decision.
6) Rheem will likely last longer, despite being two years older. We'll see.
Either one will save you a lot of electricity + bonus dehumidification (while operating). I bought whichever was cheapest, the first time; now I would buy the AO even if ~$250 more expensive because the install is that much easier. This last rebate period I bought three =P
The legionella thing is a little overblown fwiw. 50 degrees is perfectly adequate, and you can go lower with very little risk if you set it to briefly bump up to 60 every week or two. Even that is not hugely necessary in a domestic setting.
> Does heating water in a boiler work well with a heat pump?
Sure, heat pump hot water tanks are a thing. Air-to-water heat pumps are less efficient than air-to-air as they need to reach higher target temperatures, but it will be more efficient that straight resistive heating by a factor of 2 at low input temperatures, and 3+-ish at high summer temps.
The primary concern would be the quality of the tank’s insulation. I would hope HPHWTs are good on that but if you’re looking into that you probably want to double check the heat loss of the tank.
For the datasets, I tried to access (like the full disc image in visible wavelength, MTG 0 degree), it is sufficient to register at eumetsat to get a username and password. The eumdac python tool is probably the easiest way to access the data:
(If you do not want to use python, the --debug option is quite useful to see exactly the request made. The output is either some JSON metadata or a large zip with the netcdf data)
Here is a strawman for you: studies for regulation A show that it is successfull in improving habitat for endangered species. Studies also show that the regulation increases tax burden and decreases competitiveness of national agriculture.
Should the regulation be chopped?
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