Newbie on solar contract?

[russ]

possibly a heat pump for the pool.

A solar thermal system for the pool seems to probably be a better choice.

[wirebender06]

A solar thermal system for the pool seems to probably be a better choice.

It might seem so, but why can't a Solar PV system be used to run a heat pump? Possibly as an adjunct method to heat the pool when ambient temps aren't enough to warm the water adequately.

[SunEagle]

It might seem so, but why can't a Solar PV system be used to run a heat pump? Possibly as an adjunct method to heat the pool when ambient temps aren't enough to warm the water adequately.

All of our household hot water is heated with a solar thermal system. While it might not very cold here in Florida we do get temps in the low 30's and I still get very hot water.

I also believe a solar thermal unit is more efficient to heat water than using a pv system and electric heat pump.

[J.P.M.]

It might seem so, but why can't a Solar PV system be used to run a heat pump? Possibly as an adjunct method to heat the pool when ambient temps aren't enough to warm the water adequately.

A PV system can be used to run a heat pump. But a swimming pool, even with a decent cover, is a pretty big load to meet with electricity, heat pump or otherwise. As Russ points out a solar pool heater is a much better match to the task.

One often unspoken and usually unconsidered fundamental of cost effective use of resources is to match the resource to the task. Killing flies with a howitzer is possible, but probably not too cost effective. Heating water with electricity is like cutting butter with a chain saw. Certainly possible, but not as cost effective as using nat. gas for the task, as reflected in the usual price differential for the two sources. Electricity is a low entropy source of energy best used for things that higher entropy sources like, say, nat. gas can't do in their raw form, like, for example, running the monitor you're probably reading this from.

Depending on climate, and after addition of a solar pool cover, "active" solar pool water heating is the best adjunct to the pool cover, and about the most cost effective use of "active" solar energy for residential use there is at this time. After that, and a poor third probably comes nat. gas. Electrical heating of pool water, heat pump or otherwise ain't even on the radar.

Add: Depending on climate, most of the same goes for heating domestic water, although some solar "batch" heaters may be more cost effective than some "active" systems for heating domestic, residential potable water.

[wirebender06]

A PV system can be used to run a heat pump. But a swimming pool, even with a decent cover, is a pretty big load to meet with electricity, heat pump or otherwise. As Russ points out a solar pool heater is a much better match to the task.

One often unspoken and usually unconsidered fundamental of cost effective use of resources is to match the resource to the task. Killing flies with a howitzer is possible, but probably not too cost effective. Heating water with electricity is like cutting butter with a chain saw. Certainly possible, but not as cost effective as using nat. gas for the task, as reflected in the usual price differential for the two sources. Electricity is a low entropy source of energy best used for things that higher entropy sources like, say, nat. gas can't do in their raw form, like, for example, running the monitor you're probably reading this from.

Depending on climate, and after addition of a solar pool cover, "active" solar pool water heating is the best adjunct to the pool cover, and about the most cost effective use of "active" solar energy for residential use there is at this time. After that, and a poor third probably comes nat. gas. Electrical heating of pool water, heat pump or otherwise ain't even on the radar.

Add: Depending on climate, most of the same goes for heating domestic water, although some solar "batch" heaters may be more cost effective than some "active" systems for heating domestic, residential potable water.

I fully agree with what everyone is saying regarding the inefficiency of heating a pool with electricity over solar.

Currently, the only means to hold heat in my pool is with a solar blanket. When the temps are hot, its very effective keeping the pool warm. In the hottest part of the summer, it works too well and we have to remove it to prevent the pool from becoming a giant hot tub. However, as the night time temps drop, the water temp in the pool drops concurrently and it becomes too cold for comfortable pool use. Our swim season currently runs from June to the end of september.

From what I understand about solar pool heating, in conjunction with a pool cover, you can extend your swim season by perhaps 2-3 weeks on either end of those months and at best, you get a month on either side of the summer months.

So with my current situation, I get about 4 months of pool usage each year. The cost to maintain the pool (chemicals, cleaning, pool pump, etc) year-round is not cheap and I've always wanted to find a way to extend out swim season so that those costs could be better justified each year.

In my attempt to find ways to accomplish that, I came across a company Aquacal who claim that a heat pump can be quite effective and not as inefficient as most believe to heat your pool. Apparently they are quite popular in Arizona and some parts of Florida.

So if using the heat pump alone is inefficient, what about the idea of getting solar pool heating system which gives me maybe 6 months of swimming, if i add a heat pump, i could perhaps extend it by another month on either side which might get me 8 months of swim each year. Punching in some rough numbers on the aquacal website, it would cost roughly $70-100 to heat the pool in April and October. Something that a PV system could offset in those months.

What do you guys think?

[russ]

From the Aquacal website -

If the heat pump uses no fossil fuels then it is to be operated on solar PV only? Just BS advertising as most power is from fossil fuels

Emit no noxious gas - Again it is BS - that is done by the electric generator

Uses 410A - I believe all new refrigerants sold in the US use "green" refrigerant

• "Are Solar Heat Transfer Units" No more than any other heat pump
• Meet all AHRI efficiency standards Well whoopee - don't all new ones?
• Do not need sunshine to heat your pool - Not solar transfer units then?

The items in this are all BS advertising and nothing more.

Electric consumption specification? Their claim of 400 to 600% improvement over electric resistance heating is total BS

The heat pump idea can work and the efficiency can be OK - you can NOT run the pool water through the heat pump - bad things would happen. Many honest companies without the BS sell the same thing.

Did you know? AquaCal Heat Pumps:

• Use no fossil fuels
• Emit no noxious gas
• Use Green R410A refrigerant
• Are Solar Heat Transfer Units
• Minimize your carbon footprint
• Meet all AHRI efficiency standards
• Do not need sunshine to heat your pool
• Still heat your pool when temperature drops to 45°F

[thejq]

Heat pump is not the same as a thermal electric heater, although they achieve the same goal, the technical principle behind them are completely different. A normal water heater uses electricity passing through a heating element to create heat. A heat pump exchange heat from the surrounding environment like running an AC (or fridge) in reverse. So the air exhausted from it would be freezing cold. It won't work well if the ambient temperature is too cold (eg no heat to extract from). In theory, if the pump is really efficient it can exchange much more energy/heat than it consumes. Just look at how efficient refrigerator has become in the last 10 years or so. A well build heat pump in general is much more efficient than a gas heater. Comparing it to a solar water collector however is more complicated. Remember, normally the collector has to be installed on the roof (to compete with your PV's real estate) with long pipes. Most of at time, you have to upgrade the water pump to 2 HP to pump the water 20 feet up. Also heat pump can be run at night, whereas solar collector only during the day. So it's hard to say which one is cheaper to run (between heat pump and solar water), but if you can get electricity cheap like from solar, it's definitely cheaper to replace that old gas heater if you plan to run it often and at night.

[wirebender06]

Heat pump is not the same as a thermal electric heater, although they achieve the same goal, the technical principle behind them are completely different. A normal water heater uses electricity passing through a heating element to create heat. A heat pump exchange heat from the surrounding environment like running an AC (or fridge) in reverse. So the air exhausted from it would be freezing cold. It won't work well if the ambient temperature is too cold (eg no heat to extract from). In theory, if the pump is really efficient it can exchange much more energy/heat than it consumes. Just look at how efficient refrigerator has become in the last 10 years or so. A well build heat pump in general is much more efficient than a gas heater. Comparing it to a solar water collector however is more complicated. Remember, normally the collector has to be installed on the roof (to compete with your PV's real estate) with long pipes. Most of at time, you have to upgrade the water pump to 2 HP to pump the water 20 feet up. Also heat pump can be run at night, whereas solar collector only during the day. So it's hard to say which one is cheaper to run (between heat pump and solar water), but if you can get electricity cheap like from solar, it's definitely cheaper to replace that old gas heater if you plan to run it often and at night.

That's what I was hoping to do, but like the responses on this thread, I haven't found too many people who think its a good idea.

[russ]

A heat pump can be a good deal though I do not agree with several general points in the previous post.

The Aquacal I was not at all impressed with! They are relying on BS to direct the customer rather than facts. What counts is the kW in compared to the Kw out - referred to as COP. They didn't give that in the document (owners manual) that I looked at.

The pool water can not be allowed to go through the heat pump - you have to have a separate heat exchanger in the loop. If they don't have that heat exchanger then they are even bigger shysters than I think and that would take some doing.

[thejq]

The pool water can not be allowed to go through the heat pump - you have to have a separate heat exchanger in the loop. If they don't have that heat exchanger then they are even bigger shysters than I think and that would take some doing.

Why not? Any of the pool heat pumps will allow you to do that, eg. http://www.rheem.com/products/pool_spa/classicseries/ also lists the rough cost comparisons. BTW, I don't work/install/market Rheem products, it's just for illustration. Just connect input and output, plug it in. No extra exchanger is needed.

[russ]

Why not? Any of the pool heat pumps will allow you to do that, eg. http://www.rheem.com/products/pool_spa/classicseries/ also lists the rough cost comparisons. BTW, I don't work/install/market Rheem products, it's just for illustration. Just connect input and output, plug it in. No extra exchanger is needed.

Any of the pool heaters will NOT allow you to do that safely.

Rheem has a titanium heat exchanger - common in sea water systems but not for home use. The Aquapal does not or else they would have listed it - it is an expensive part.

I have not seen the 6 COP before - No different than any ASHP in an air to water configuration and they typically are in the 3.5 range.

With a COP of 6 it would be the most efficient way to go by far.

[thejq]

Most of the pool heat pumps made by brand names have titanium heat exchanger specifically built for pool water, including the Aquacal http://www.aquacal.com/aquacal-pool-heat-pumps. They are expansive, costing a couple of thousands to start. If your old system still works, it may or may not worth it to upgrade, but if you're starting fresh, it's definitely worth considering. FWIW, I don't have heat pump, but my neighbor does. I have a ground mount solar collector, so it's relatively cheap to run.

[russ]

Most of the pool heat pumps made by brand names have titanium heat exchanger specifically built for pool water, including the Aquacal http://www.aquacal.com/aquacal-pool-heat-pumps. They are expansive, costing a couple of thousands to start. If your old system still works, it may or may not worth it to upgrade, but if you're starting fresh, it's definitely worth considering. FWIW, I don't have heat pump, but my neighbor does. I have a ground mount solar collector, so it's relatively cheap to run.

I stand corrected - something totally new on me. I still point out that a lot of the Aquacal advertising is tripe.