Hot Water - Solar / hybrid / on demand

[TonyWilliams]

I've been in the solar industry for 12 years and have PV, Solar Pool heating, and solar thermal for domestic hot water on my home.

Tell us a bit about solar hot water. I'm interested since I have two hot water tanks that are 15 years old.

 

[jimbo69ny]

What would you like to know? I am well versed in solar hot water.

Check out my website, http://threehillsproperties.com/

 

[miimura]

I looked into doing solar hot water in Silicon Valley two years ago. The state has a rebate program for solar hot water. However, the required engineering is so rigorous that people I talked to would rather sell the system without participating in the rebate program. They basically said that they would have to charge an additional amount almost equal to the rebate amount just to participate in the program. In addition, the state guidelines for the rebate program don't allow you to use stored hot water for freeze protection, so you are forced to use a glycol system, further increasing the cost. The most cost effective system I found was a passive system with storage on the roof. It would basically be set up as a pre-heater ahead of a conventional storage water heater. I was not willing to put that big ugly thing on my roof because it was visible from the street. In addition, the choices for boosting heaters were slim. The best option I found was an electric 240VAC system that used PWM modulation so that it would not switch in a big load all at once, causing voltage drops and lights dimming. Those can be arrayed or even installed in series to get the required temperature rise at the required flow rate. I don't have a link handy, but I can find it if someone is interested. One more thing, I was investigating this for new construction and the electric heaters would have been a significant hit to my Title 24 numbers, so the Green Points consultant advised against it even though it could be offset with solar PV.

Finally, I ended up with a Navien NR-240A Condensing Tankless Gas water heater. The Energy Guide showed $125/year energy costs, so it was hard to justify spending the quoted $10,000 for solar hot water vs. $1,650 for the Navien. I'm sure there are better solar options out there, but I wasn't able to find an installer to quote me a reasonable system within the time I had available. I really like the Navien and have no regrets.

 

[arnolddeleon]

When I replaced with my water heater with a tankless unit I planned to adding a solar water heater. I had the plumber install valves for it so it would be easy. But Every time I would look at the numbers I couldn't make it work. I tend to agree with this sentiment:

http://www.greenbuildingadvisor.com/blogs/dept/musings/solar-thermal-dead

The bonus I got with the tankless water heater is space freed up in the garage. If I had money to burn then I might consider a heat pump water heater just on the principle of using less natural gas.

arnold

 

[miimura]

When I replaced with my water heater with a tankless unit I planned to adding a solar water heater. I had the plumber install valves for it so it would be easy. But Every time I would look at the numbers I couldn't make it work. I tend to agree with this sentiment:

http://www.greenbuildingadvisor.com/blogs/dept/musings/solar-thermal-dead

The bonus I got with the tankless water heater is space freed up in the garage. If I had money to burn then I might consider a heat pump water heater just on the principle of using less natural gas.

arnold

That's a very good article. They do bring up a good point about the lifetime of a heat pump water heater (maybe only 5-8 years) and the importance of where it is located. As waidy said on this forum some time ago, if you can put the water heater in the same space as your string PV inverters, it will help because the waste heat from the inverters will improve the efficiency of the water heater. Also, if you have a good place to put it, a completely passive solar water heater is an inexpensive way to pre-heat your water before it even goes into a heat pump water heater.

 

[jimbo69ny]

Solar hot water has a better return on investment than any EV car, plug in hybrid, or PV system. I get so tired of hearing people say they couldnt make the numbers work. If you dont use any hot water, ever, then no, it wont work. But for anyone else, it totally works. Its a simple system and its soooo easy to do. And the are cheap with tons of incentives! I have rental properties in central ny and I am putting systems on the roofs of each of my properties. My systems will pay for themselves within 3 years, probably less.

REGARDLESS, just like our EV cars, we arent in this for the "payback". We do this because its the right thing to do and its the best solution for providing a healthy environment for our kids and their grandkids. When I hear people say "it doesnt pay" it drives me crazy. Even in whatever math your using, it WILL PAY! Your grand kids kid may be the one person on the planet that uses the last gallon of gasoline or natural gas. If you switch now, maybe that last gallon happens next generation instead.

In the north east we have to worry about fracking and the fact that it ruins our drinking water. Which is a whole other debate. I for one try to use as much renewable sources as possible. Aside from all the political bs etc, I save a ton of money. One of my properties is a 3 unit house which I live in myself. I bought it in May of 2013. Prior to that the propane bill was $400/month on average. Since installing a solar hot water system in May of this year, I havent spent a DIME ON PROPANE! Right there I saved at least $2000! I am not sure how the winter will be quite yet but I am hoping to wait as long as possible to find out.

 

[pchilds]

In SoCal my gas bill is $10 month, please show me the payback in 3 years. :lol:

 

[smkettner]

In SoCal my gas bill is $10 month, please show me the payback in 3 years. :lol:

Mine is 40% higher :| Still don't see the return.

 

[Tadol]

Great info! I have PV on our home and at our coast house, but use NG at home and a very old electrical water heater on the coast. Both need replacing pretty soon, and I've been trying to get more info on solar water heating as well as possible solar space heating and dehumidification - that link led to enough other threads I'll be reading for days!

 

[miimura]

Solar hot water has a better return on investment than any EV car, plug in hybrid, or PV system. I get so tired of hearing people say they couldnt make the numbers work. If you dont use any hot water, ever, then no, it wont work. But for anyone else, it totally works. Its a simple system and its soooo easy to do. And the are cheap with tons of incentives! I have rental properties in central ny and I am putting systems on the roofs of each of my properties. My systems will pay for themselves within 3 years, probably less.

Please give us the details about your system and how much the total installed cost was. I know this stuff isn't rocket science, but I couldn't find an installer out here to do one for a sane price.

 

[DevinL]

My parents got solar hot water (for pool heat) & PV on their house in northwest LA county. They were on propane, not nat gas, so the cost savings made a lot more sense. That said, the system was a colossal pain in the butt and never quite worked right. With a pool solar system you pump the actual pool's water through the panels though, and they had a salt water chlorinator, so that could have been part of the issue.

I have wanted to go to tankless hot water at my house since we moved in but just can't justify it since the tanked water heater still works and my highest bill from SoCalGas was $50 when running the FAU. During the summer when it's only used for water and cooking it rarely ever goes above $10.

 

[miimura]

My parents got solar hot water (for pool heat) & PV on their house in northwest LA county. They were on propane, not nat gas, so the cost savings made a lot more sense. That said, the system was a colossal pain in the butt and never quite worked right. With a pool solar system you pump the actual pool's water through the panels though, and they had a salt water chlorinator, so that could have been part of the issue.

Solar pool systems are a completely different animal than domestic hot water. It is low pressure, direct circulating, and it doesn't matter what the outlet temperature is as long as it's warmer than the inlet. They are easy and cheap to install and have great payback compared to other pool heating methods.

 

[jimbo69ny]

My parents got solar hot water (for pool heat) & PV on their house in northwest LA county. They were on propane, not nat gas, so the cost savings made a lot more sense. That said, the system was a colossal pain in the butt and never quite worked right. With a pool solar system you pump the actual pool's water through the panels though, and they had a salt water chlorinator, so that could have been part of the issue.

Solar pool systems are a completely different animal than domestic hot water. It is low pressure, direct circulating, and it doesn't matter what the outlet temperature is as long as it's warmer than the inlet. They are easy and cheap to install and have great payback compared to other pool heating methods.

And the collectors are different too. The chlorine reacts to the copper over time and degrades it. Pool systems usually have plastic collectors.

 

[jimbo69ny]

You can look on my website for some photos. I also have photos on my facebook pages.
www.threehillsproperties.com
www.emmasacresllc.com

On facebook search for Three Hills Properties and Emma's Acres LLC.

As for my investment, I purchased the remaining solar hot water heating equipment from a company that went bankrupt. I bought it all for a fraction of its value. I bought about $60,000 worth of stuff for $14,000. I sold 2 complete solar hot water kits that included 2 panels and a tank for $2900 each. In ny you can get a complete system installed from a professional company for $8,000 - $10,000 and I think the tax credits are 40-50%. So say around $4000. If you pay $50/month in solar hot water heating, and assuming the solar hot water system makes up 100% of your hot water needs (which in California it definitely should!), the pay off is about 6.6 years. However there are a ton a variables and each household is different. It really depends on how much hot water you use and how much sunlight you get.

Each of my systems ended up costing me about $4000 including the equipment materials and hiring some help to mount the panels to the roof. However I have HUGE systems because they are 3 and 4 unit apartment houses. (see my websites)

Solar hot water systems are sooo easy to do. Any plumber can plumb the system. I have never done one before and I installed 2 so far that work great. this summer they have provided 100% of my heating needs. Solar hot water has been proven to have a better return that pv systems or plug in cars.

 

[miimura]

I assume your systems use glycol and a heat exchanger. Is it an external exchanger or a glycol loop inside the tank? I assume you would not do a drainback system in NY. I love what you've done at Emma's Acres, but I think it's a little telling that you were able to get the equipment from a company that went bankrupt.

 

[jimbo69ny]

Thank you. I am very proud of Emma's Acres and I cant wait to continue development.

What do you mean it was telling that I bought it from a bankrupt company?

Yes I am using a glycol system. You have to use a glycol system anywhere there could be a freezing concern. I also designed the systems to use steamback which is the only way to go as far as I am concerned.

I have huge tanks and yes they all have internal heat exchanging coils. In the property at Emma's Acres I have a 135 gallon, a 105 gallon dump and a 40 gallon back up fired off the propane boiler.

 

[miimura]

What do you mean it was telling that I bought it from a bankrupt company?

Presumably the company was trying to make money installing solar thermal systems and wasn't able to survive. Obviously, I don't know the circumstances, but my conclusion was that there was insufficient demand for that hardware, so you were able to pick it up cheaply. It's also informative that you found the installed system cost reasonable when you were able to buy the hardware at a significant discount and you provided most of the labor.

Can you explain "steamback"? I'm not familiar with that term.

 

[jimbo69ny]

The fact that I bought the equipment from a company that went bankrupt has nothing to do with the technology. The owner of the company knew nothing about solar hot water and his employees stole from him. He also invested in spray foam not knowing about that field either. He made really bad business decisions. There are at least 4 other companies in my area that do just fine.

This is long but it will probably explain it.
https://www.youtube.com/watch?v=pt5Cc14Dyk8

Its a relatively new way of installing solar hot water systems. Here it is in a nutshell.
The big problem with solar hot water systems is the risk of overheating and building too much pressure. To combat that you have a few options
1. a large storage tank that would take forever to heat up or simply not get hot enough to provide all of your heating needs. It would strictly be a preheating system for your main hot water heater.
2. Have a normal size tank and a heat dump. The heat dump could be a radiator or a second water storage tank.
3. With steamback, you have a normal size tank and when the temperatures get too high the circulatory pump turns off. The h2o part of the glycol mixture turns to gas and pushes the glycol into oversized expansion tanks. Then when temperatures drop the pump turns back on and the gas turns back into h2o. With a steamback system you do not use air release valves at the top of the system because you want that gas to stay inside. You also need to do some math and make sure you have plenty of expansion tank space. Its the best way to go because it will keep your tank temperatures high so you can actually use the system as your main heating source instead of just a preheater.

 

[miimura]

Good explanation. I always thought that if you wanted to have a large system that can do radiant heating in the winter and domestic hot water year-round in a southern state, that it would be very helpful to have a pool so you could dump the excess heat into the pool in the summer. Of course, that would require an external heat exchanger to transfer the extra heat to the pool water. That's an idea I had that I've never actually seen implemented.

 

[Larry_in_Seattle]

Solar Thermal is an excellent technology that works really well in all climates... IF you use the appropriate technology for the intended use. Three main types of water heating systems.

Solar Pool Heating: Uses what is called an unglazed collector, simply meaning there's no glass or frame around the black colored absorber. Yes, the easiest lowest cost and most efficient solar system. At low delta T (temperature difference between pool temp and rooftop temp at the collector), a plastic solar pool collector can reach over 80% efficiency. Even in the Seattle area, a pool system pays for itself in 3-5 years when installed by a professional company (not self installed which would be much quicker.) Max temp in practical use is about 105-110F. NO special overheating protection required, drains at night or when off, thereby also serving as freeze protection since there's no water left to freeze pipes. A "Drainback" system that drains by gravity when turned off. Haven't needed any backup (gas) pool heating the last 9 years for summer use in Seattle.

Flat Plate Glazed collector: Been around for probably 50 years, typically copper tubing inside a frame with glass (Glazing), insulation on sides and bottom, and the copper tubing is painted black or dark blue to absorb the most heat. Most commonly used around the US and elsewhere for a long time. Durable, can reach working temperatures over 170F. Needs antifreeze/over heating protection in most climates (propylene glycol, a non-toxic heat transfer fluid used in Sierra Peak's non-toxic antifreeze). Various ways to design system. Good for climates that don't go below freezing because with that big plate of glass on the top, heat loss is a big problem. Sizes range from 3'x5', to most common 4'x8' to larger commercial sized ones.

Evacuated Tube collector system: Used to be 3x more expensive than flatplate glazed systems, but now about the same cost. Can reach temps over 212F, works great in sub-zero temps due to the fact it's built like a thermos bottle (vacuum). I have this kind of system for my domestic hot water. Can be used for process heat like breweries that need a lot of hot water (147F ???). This is USUALLY a glycol protected system too, but mine is a drainback system that simply uses water (but not the drinking water) as the heat transfer fluid.

A good solar thermal designer can work with you to determine exactly what will work best for your needs, your climate, etc. You get the 30% federal tax credit, it's sales tax free in WA, and is a great way to offset your water heating from gas/electric powered systems.

Biggest savings for those who use a lot of hot water. Since you can't spin your gas or electric meter backwards with excess hot water, unused hot water is just 'wasted'. So, for those who only spend $10/month on heating your water the reason to go solar thermal will not be 'economic', but simply because you want to be a part of the solution ... like by driving an EV.

My self-installed system in Seattle paid for itself after about 7 years, and we've never ever ever run out of hot water even when extended family was visiting and everyone was in and out of the pool and shower all day long.

Expecting to do much radiant heating with with solar in the winter is very problematic in most places. The highest need for heat, and the fewest hours of usable sunlight per day. You need the most heat at night... precisely when there's no sunlight to replenish the system. I've done multiple systems though that were oversized for winter heat collection, and used excess heat for domestic hot water, and an in-ground pool during the summer when the house heating load was low.