Thanks. That's very helpful because that's the size I was looking at. Maybe I'll start with half that size. I'm guessing this was diy?
Why almost no one doing Solar Thermal?
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Also with the equipment available today I could of controlled it better.
If I was going to do it again I would of used the pool as a dump for when the hot water heater reached temp. Remember that water is going to boil eventually no matter what if you don't have somewhere to send the heat. I also toyed with the idea of motorized slats to cover the collector box when it reached desired temps. Never tried it though.
Last thing I wanted to try and never did was a water to water exchanger. Heat antifreeze or some other coolant in the collector and have it go thru a tank with its coolant lines and a line from the water heater submerged in the tank. The highest temp the water heater could be exposed to would be sub boiling temps in that exchange tank for safety. But you would have to keep the exchange tank topped off from time to time. Was in the country so I had plenty of room there to play with stuff like this
New place is in the city so "experiments" are not really possible here.
If I was going to do it again I would of used the pool as a dump for when the hot water heater reached temp. Remember that water is going to boil eventually no matter what if you don't have somewhere to send the heat. I also toyed with the idea of motorized slats to cover the collector box when it reached desired temps. Never tried it though.
Last thing I wanted to try and never did was a water to water exchanger. Heat antifreeze or some other coolant in the collector and have it go thru a tank with its coolant lines and a line from the water heater submerged in the tank. The highest temp the water heater could be exposed to would be sub boiling temps in that exchange tank for safety. But you would have to keep the exchange tank topped off from time to time. Was in the country so I had plenty of room there to play with stuff like this
New place is in the city so "experiments" are not really possible here.
LOL VERY diy. There wasn't much out there back then to buy even if you wanted to unless you wanted an entire setup. I talked to a friend who ran the local housing authority and they had installed solar water heating on the newer apartments with a gov grant when they built them. He said each unit which had two apartments in it but shared the solar water heater. Each unit cost them $25,000.
Lt.Dan
Solar Wizard
In my home town of 125,000 people, I think I have seen 1 or 2 houses with Solar Thermal in their roofs. Like others have said, PV just makes far more sense IMO
I've also heard of people pumping water through their PV panels to heat their pool, but here it gets so hot in the middle of summer, that a regular pool almost feels like a luke warm bath, which is not very enjoyable. Heating it up any more would be even worse.
I've also heard of people pumping water through their PV panels to heat their pool, but here it gets so hot in the middle of summer, that a regular pool almost feels like a luke warm bath, which is not very enjoyable. Heating it up any more would be even worse.
That's because the systems are so expensive here in the States
OzSolar
Whatever you did, that's what you planned.
Solar thermal via batch collectors are still very widely used in non freezing climates. Decades of troubles free service is the norm. Adding freeze protection is where the feasibility breaks down quite quickly. FWIW: I've installed or worked on hundreds of solar water heating systems over the last 30 years.
peakbagger
Solar Enthusiast
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I have had solar thermal over 20 years. Its pretty simple, a DC circulator pump, a used Siemens 60 watt PV panel, a simple controller two hot water panels and a Rheem Solaraide storage tank. It works but fundamentally it produces too much heat in the summer and marginal in the winter. Standard hot water panels only raise the water temp 80 F over ambient temps during the day. Its fine for preheating incoming water like I do in winter but not enough without supplementing it. My Rheem tank is basically an electric hot water heater with copper coil wrapped around it before its insulated and skinned and it has one set of electric elements. I didnt even hook up the elements until a few years ago as in the winter I use it for preheat and then use my wood boiler to heat it up the rest of the way.
Common system failures were differential temperature controller failures, acidic glycol eating the copper in the collectors and piping, air vents failing and check valves failing leading to freeze ups. Storage tank failures also are a known issue. I have fairly non aggressive water and change out my tank anode about every five years. Almost all tank type electric hot water heaters have sacrificial anodes and if they are changed routinely, heaters can last for the life of the house. Plumbers make their living selling heaters so few anodes are replaced. I do not know if Rheem even sells this tank anymore so its to my incentive to keep the anode in good shape. On many heaters the anode is too long to remove without hitting the ceiling. In that case, they have to be pulled up, clamped so they do not slide back down in the tank and cut off before pulling the rest of it out. There is special anode called a flexible anode or "hot dog" anode that is string of anodes on a stainless cable that will slide right back in. In areas with agressive water the anodes may need to be replaced every couple of years in other cases they can last ten years. It the anode isn't there or just a remnant is there, plan on replacing the heater soon. Also make sure to drain the sediment out of the tank bottom every year or two as corrosion cells can form in the bottom if the sediment gets deep.
Given the drop in PV costs and heat pump water heaters along with net metering, its far better to add a few PV panels and pump it back to the grid and then use it when you need it with a heat pump hot water heater. I am not abandoning mine and am always keeping my eye out for used SHW panels as when I build a new house I may still install one for mostly summer use since I have a few spares like spare DC pump and spare PV panels to drive it. Not sure what I would do for storage but think I would use an Aquamate tank typically used for residential hot water running off a zone of oil or gas heat. I would just switch over to the wood boiler in the winter and skip the preheat due to piping complexity.
BTW, evacuated tube type collectors look neat but the tubes tend to fail early and often. They tubes are not standardized, and finding replacements is impossible. I would recommend avoiding them. A thermal camera will easily show the contract between good and bad tubes.
Common system failures were differential temperature controller failures, acidic glycol eating the copper in the collectors and piping, air vents failing and check valves failing leading to freeze ups. Storage tank failures also are a known issue. I have fairly non aggressive water and change out my tank anode about every five years. Almost all tank type electric hot water heaters have sacrificial anodes and if they are changed routinely, heaters can last for the life of the house. Plumbers make their living selling heaters so few anodes are replaced. I do not know if Rheem even sells this tank anymore so its to my incentive to keep the anode in good shape. On many heaters the anode is too long to remove without hitting the ceiling. In that case, they have to be pulled up, clamped so they do not slide back down in the tank and cut off before pulling the rest of it out. There is special anode called a flexible anode or "hot dog" anode that is string of anodes on a stainless cable that will slide right back in. In areas with agressive water the anodes may need to be replaced every couple of years in other cases they can last ten years. It the anode isn't there or just a remnant is there, plan on replacing the heater soon. Also make sure to drain the sediment out of the tank bottom every year or two as corrosion cells can form in the bottom if the sediment gets deep.
Given the drop in PV costs and heat pump water heaters along with net metering, its far better to add a few PV panels and pump it back to the grid and then use it when you need it with a heat pump hot water heater. I am not abandoning mine and am always keeping my eye out for used SHW panels as when I build a new house I may still install one for mostly summer use since I have a few spares like spare DC pump and spare PV panels to drive it. Not sure what I would do for storage but think I would use an Aquamate tank typically used for residential hot water running off a zone of oil or gas heat. I would just switch over to the wood boiler in the winter and skip the preheat due to piping complexity.
BTW, evacuated tube type collectors look neat but the tubes tend to fail early and often. They tubes are not standardized, and finding replacements is impossible. I would recommend avoiding them. A thermal camera will easily show the contract between good and bad tubes.
HarryN
Solar Enthusiast
There is actually a lot of solar thermal in Florida and some other states.
The most common use is pool and hot tub heating. It is very good for that application.
The most common use is pool and hot tub heating. It is very good for that application.
OzSolar
Whatever you did, that's what you planned.
There’s people with experience with solar thermal and those with opinions.
Some do…
Some do…
EastTexCowboy
Solar Wizard
I heat my water the old fashioned way - natural gas on demand.
We're fortunate to be in a rural area that actually has NG service. First home I've ever had with an option for NG. The only things running on it are two on demand Rheems, the cooktop, and the generator that exercises once a week. My monthly gas bill is about $25 year-round. The minimum charge is $18 so I'm really not using a lot. I can't improve much on that.
We're fortunate to be in a rural area that actually has NG service. First home I've ever had with an option for NG. The only things running on it are two on demand Rheems, the cooktop, and the generator that exercises once a week. My monthly gas bill is about $25 year-round. The minimum charge is $18 so I'm really not using a lot. I can't improve much on that.
What controls the temperature ? WHat happens when the water begins to boil ? Thanks
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
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- 18,970
The standard thermostat controls a DC relay. Which turns on or off the solar array. With two relays, both elements can be used.
I'm using an 80 gallon electric hot water heater right now. Works fine and all and heats up fast but it does use a good bit of power when on. But the total kw used a day is VERY low in comparison with other things in the house.
Even days where a bunch of hot water is used the most I see is 6kw for the day with 2kw or so being the norm.
That said I do plan on upgrading to a tankless natural gas hot water heater. While fairly expensive natural gas is awesome if you have access to it. That is one of the biggest benefits of being in town now. Also having it power the generator too rocks since that gives me unlimited run time if needed.
With the tank-less one I'm going with there isn't even a pilot light as it uses electric ignition so unless hot water is need its free.
Even days where a bunch of hot water is used the most I see is 6kw for the day with 2kw or so being the norm.
That said I do plan on upgrading to a tankless natural gas hot water heater. While fairly expensive natural gas is awesome if you have access to it. That is one of the biggest benefits of being in town now. Also having it power the generator too rocks since that gives me unlimited run time if needed.
With the tank-less one I'm going with there isn't even a pilot light as it uses electric ignition so unless hot water is need its free.
dougbert
Solar Addict
yep, I can most of those same problems. When expensive heat exchanger croaked, that it was it for me.
I first got this system free some 15 years or so ago. Built in the late 70s Come pick it up and take it away. The only things I used were the 2 4x8 collections. copper sheet with copper pipes "welded" to the sheet. With one inlet and one outlet. I installed both in series and things worked, until it froze with water pooling in the mis-aligned drain down. Burst a copper pipe in one of the collectors.
Scrapped that one
run on one until the heat exchange began leaking. It worked but lots of work to keep it going, used gylcol and active pumps
I still have the last collector and am wondering to give it away or recycle the copper and aluminum
peakbagger
Solar Enthusiast
- Joined
- Oct 26, 2021
- Messages
- 310
Once people figure out that there is copper in them, they usually end up at the scrap yard. Some were built with aluminum and they usually are not worth trying to reuse as they tended to corrode.
I do see the Amtrol or equivalent indirect water heater tanks show up on Craigslist pretty often, they can make cheap but kind of a small SHW storage tank but stilll good for summer operation. The finned tubed heat exchangers inside them are pretty robust. They have to be used with the non toxic antifreeze on the collector side as they are direct contact exchangers. On occasion the brazed joints on the heat exchanger and bottom over can leak, I tired rebrazing once and had a tough time but a bit of epoxy seemed to hold.
I do see the Amtrol or equivalent indirect water heater tanks show up on Craigslist pretty often, they can make cheap but kind of a small SHW storage tank but stilll good for summer operation. The finned tubed heat exchangers inside them are pretty robust. They have to be used with the non toxic antifreeze on the collector side as they are direct contact exchangers. On occasion the brazed joints on the heat exchanger and bottom over can leak, I tired rebrazing once and had a tough time but a bit of epoxy seemed to hold.
If someone does go this route or is already doing it check out evans coolant. Its VERY expensive compared to antifreeze but last forever and has zero pressure issues for most of its temp range. I think it boils at 350 degrees or something.
Also it shouldn't eat the copper tubing either.
Also it shouldn't eat the copper tubing either.
IMO it only makes sense if it’s integrated in two or three alternatives.
Solar Thermal systems are huge in Europe/Germany but I think it was back when PV panel costs were high and it was integrated with one or two other heating systems (fossil fuel + biomass). Not sure how subsidies assisted in installs.
Free heat is free heat, but excess heat in summer and minimal heat when you need it in winter is a challenge for system design.
Solar Thermal systems are huge in Europe/Germany but I think it was back when PV panel costs were high and it was integrated with one or two other heating systems (fossil fuel + biomass). Not sure how subsidies assisted in installs.
Free heat is free heat, but excess heat in summer and minimal heat when you need it in winter is a challenge for system design.
Ampster
Renewable Energy Hobbyist
Over the past forty years I have done two solar thermal systems and have come to the conclusion that the most cost effective system is PV solar with a heat pump water heater. As mentioned earlier, thermal solar still makes sense for swiming pools because the temperature differential is small and the panels are less expensive and the pump equipment is already in place for the pool filter anyway.
I have solar hot water; it is required by code in Hawaii. Flat panel system, direct loop of potable water. (Nice that we don't really need any glycol here.) It saves a huge amount of energy and in our climate is better than adding PV. The electric water heater needed 90kWh in the past year, which is essentially 10-15 days without enough sun.
I was originally planning on eliminating one of the three 4x10' panels because it is causing sag on one of the window headers and replacing it with PV. Once I had the metering data it became clear that it was a bad idea to do that.
We don't have heat, so it isn't used for that. The two 120-gallon tanks are 14 years old and might not make it to 20. They will be a bear to replace like-for-like; the space they are in has very little extra clearance. The level of storage is what we need for the house to minimize electric water heater use, but a compromise might be to do an inline 4kW instant booster water heater for the master bathroom
I was originally planning on eliminating one of the three 4x10' panels because it is causing sag on one of the window headers and replacing it with PV. Once I had the metering data it became clear that it was a bad idea to do that.
We don't have heat, so it isn't used for that. The two 120-gallon tanks are 14 years old and might not make it to 20. They will be a bear to replace like-for-like; the space they are in has very little extra clearance. The level of storage is what we need for the house to minimize electric water heater use, but a compromise might be to do an inline 4kW instant booster water heater for the master bathroom
Ampster
Renewable Energy Hobbyist
My brother has a place in Mauai and it must have been constructed before that code went into effect do it did not have thermal solar. Because of the high electric rates he did put in solar recently, but he could not get a NEM agreement so he also installed two Tesla Powerwalls. Now the utility has come back and asked him to participate in a program where they will pay him to use his Powerwalls to support the grid. About the same time he istalled the solar and Powerwalls he also installed a heat pump water heater. One of the benefits of that is that the cold air exhaust can be used to cool the home.
