Solar PV heat pumps?

[MUD DAWG]

Has anyone installed one of these for their homes or garages?

There are system that are purely solar, but will require a battery bank, and there are hybrid systems like the one linked below. I wouldn't get rid of my propane furnace, or my regular AC, but I think having a solar system would be a good addition to keep the house or garage cool/warm for a few pennies a day. Of course there's a ton of variables to consider, but I wonder if these systems really live up to their claims??

http://www.hotspotenergy.com/solar-air-conditioner/

 

[theoldwizard1]

You can make your own "hybrid" system by simply buying a very high efficiency heat pump/AC unit and a number of solar panels (however many you can afford) and "mini" inverter grid-tie solar controller.

No rocket science. All "off the shelf" parts. The best part of a "roll your own" system is that you are pumping power back to the grid whenever the sun is shinning. It CAN be more than what you are consuming, but this is where local laws and POCOs "muddy the waters".

This is a true DC-only (48VDC) air conditioner.. To use this unit off-grid, up need and energy source (wind or solar), a charge controller, and a 48V battery bank. If the voltage drops below the cut off voltage (46V), it shuts down.

 

[MUD DAWG]

This is a true DC-only (48VDC) air conditioner.. To use this unit off-grid, up need and energy source (wind or solar), a charge controller, and a 48V battery bank. If the voltage drops below the cut off voltage (46V), it shuts down.

I've seen that as well, but it's more expensive, and you need the charge controller, and battery bank that'll need replacing. The one I posted plugs directly into the solar panels. When you have nice sunshine, the power comes from the panels, and when the sun isn't shining, you still have a traditional high efficiency heat pump running off your house's 220.

 

[tyme2par4]

You can make your own "hybrid" system by simply buying a very high efficiency heat pump/AC unit and a number of solar panels (however many you can afford) and "mini" inverter grid-tie solar controller.

The difference is that the unit OP linked to appears to run off of the DC power directly. So theoretically a little more efficient, as you aren't switching between DC and AC, and you don't have the cost of the inverter.
It really depends on what the extra cost is over a traditional unit. You can buy 300W PV panels for around $.50/Watt these days.

 

[Ed Devinney]

Interesting idea, and less tweaky than the solar thermal air-conditioning that's available for non-freezing climates.

I didn't see any mention of sending excess power back to the grid?

Right now in swing season my grid-tied solar is putting a lot of unused electricity onto the grid that will surely be used with AC in summer.

Still, for a garage or one room, the price is pretty interesting. That's 1/10 the cost of just the minisplits in my place

 

[MUD DAWG]

I didn't see any mention of sending excess power back to the grid?

This has nothing to do with selling power back to the grid. Whatever power you make from the 3 panels, you use up. If the panels fall short, then grid power picks up the slack. On nice comfortable days, I don't think the system would kick on much, except to maybe dehumidify. On cold or warm days, it'll do what's needed to achieve the right temperature.

I found some videos on YouTube. And interestingly, the company website says it's a DIY job, but recommend an HVAC tech. I've never heard of HotSpot before. Are they a quality brand? Would it be difficult to get parts vs a big name miniplit like Mitsubishi?

Part 1, Components:

Part 2, Setup:

Part 3, Running (Energy consumption):

 

[yeldogt]

One of the big manufacturers is doing this with a regular split system -- it's an interesting idea and IMO will grow as the technology get a bit better and the parts more robust.

We have a problem around me in the country because too many have put in full systems -- they are designed for max summer output and what's happening is too much energy is produced at the wrong times?

Having systems designed for excess buyback creates all kinds of problems -- these hybrid systems are a great idea.

 

[Ed Devinney]

This has nothing to do with selling power back to the grid. Whatever power you make from the 3 panels, you use up. If the panels fall short, then grid power picks up the slack. On nice comfortable days, I don't think the system would kick on much, except to maybe dehumidify. On cold or warm days, it'll do what's needed to achieve the right temperature.

My point isn't about selling, it's about storing for later. But I think we are in general agreement. In many climates, theis system will not be running for a good portion of the year, or even for much of the day (think about duty cycle) and thus not consuming solar power. With only 3 panels and $1700 invested that's not much of a waste, but it's there.

Clean and simple solution for a room, for not much $. Sounds good.

 

[MUD DAWG]

My point isn't about selling, it's about storing for later. But I think we are in general agreement. In many climates, theis system will not be running for a good portion of the year, or even for much of the day (think about duty cycle) and thus not consuming solar power. With only 3 panels and $1700 invested that's not much of a waste, but it's there.

Clean and simple solution for a room, for not much $. Sounds good.

I agree that there's a bit of waste in the system, depending on where you live. But someone in a Texas or Florida summer, will recoup their investment pretty quickly. For where I live, I'd get more use out of it during those cooler spring and fall days where the furnace isn't totally necessary, but still nice to have.

Also, with a system like this, I totally see someone letting it run all day, vs trying to conserve with a regular AC or furnace.

 

[theoldwizard1]

I agree that there's a bit of waste in the system, depending on where you live. But someone in a Texas or Florida summer, will recoup their investment pretty quickly.

IIRC, that is a 1 ton unit. It might handle a 2 car garage, but that is it.

 

[theoldwizard1]

"Selling" electricity back to the POCO is basically using them as a giant AC "battery".

There are lots of local rules that govern grid tie solar system so you need to check your local codes.

They now sell "mini" solar PV grid tie controllers for between $100-$200. Plug the panel into one side and plug the other into a regular wall outlet ! Total 3kw system, including panels is under $6000.

Remember, this system will be putting 3kw back into the grid every hour the sun is shining !

 

[MUD DAWG]

IIRC, that is a 1 ton unit. It might handle a 2 car garage, but that is it.

Yeah it's a smaller unit. 11,500 BTU cooling and 11,500 BTUs cooling, so like I said, it would be a great compliment to the main system, or yeah a nice piece for the garage.

I hope this kind of technology improves and gets lower in price. In my neck of the woods, electricity prices are a very hot topic, and likely to get the government tossed out. Going off grid doesn't make sense financially, but the more stand alone technologies that emerge, the better off we'll be.

 

[Gila Monster]

You will have to supplement that by charging the battery pack with some kind of inverter that will be tied to you home's grid if you want any sort of continuous use out of it.

It would make far more sense to just buy a conventional mini split without solar panels and then tie a conventional solar panel system to your home's grid than trying to combine the two into one system.

I don't know what sort of subsidies Ontario gives you, but a 900w solar panel would probably save something like 50 cents a day on my utility bill. And that's likely being optimistic and there's no clouds or rain, etc.

When solar panels give those ratings like "900 watts" it's a "peak" rating, it only actually outputs that full amount a few hours a day. You get like only like 3-4 hours per day of full sun depending on the location and season.

 

[MUD DAWG]

I don't know what sort of subsidies Ontario gives you, but a 900w solar panel would probably save something like 50 cents a day on my utility bill. And that's likely being optimistic and there's no clouds or rain, etc.

When solar panels give those ratings like "900 watts" it's a "peak" rating, it only actually outputs that full amount a few hours a day. You get like only like 3-4 hours per day of full sun depending on the location and season.

I haven't looked into them lately, but the math as of 2 years ago still didn't make sense. We have an absolute debacle of a Green Energy Act, but that fiasco is a different debate.

I'd be more than happy to shell out the money now for solar panels, but the pay back is still pretty far out. I also held off on getting a mini-split because electricity prices are expected to take a major spike in 4 years. That was the reason I opted for a high efficiency propane furnace to replace my oil burner.

 

[Gila Monster]

I haven't looked into them lately, but the math as of 2 years ago still didn't make sense. We have an absolute debacle of a Green Energy Act, but that fiasco is a different debate.

I'd be more than happy to shell out the money now for solar panels, but the pay back is still pretty far out. I also held off on getting a mini-split because electricity prices are expected to take a major spike in 4 years. That was the reason I opted for a high efficiency propane furnace to replace my oil burner.

At least from what I've seen, solar usually only makes sense when the government showers money on people to buy it, and then they have to raise the utility rates for everyone else to pay for those programs.

Our state is cutting off this cycle and many others are following suit as it was always sold as a way to just get solar off the ground, not a permanent entitlement. No one is forbidding you to have solar, it's just not going to be subsidized by other ratepayers like it was.

Regardless, I think though you can make a really good case for a mini split system (especially if you can do the install yourself) as they are incredibly energy efficient, even if electric rates go up. I would just skip the solar part of it for now. But just do the math and see.

I would think propane for heat would get expensive.

 

[yeldogt]

The point of these systems is to smooth out the load on the grid. The isolate the panels from the grid.

If a panel was directed at the sun for max output at the heat of the day -- the theory would be as more electricity is needed to power the AC unit -- more would be coming from the panel. This would lower the need for peak power -- the most expensive part of the grid system.

Around me any system that can feed the grid -- needs much special equipment. You can't have back feeding to the lines with them knowing. We actually have areas where the grid can not take all the power being generated. The power is being bought back at rates higher than what the power grid can supply -- in effect the owners of the panels are not paying for the cost of the delivery.