Any GARNheads out there tried combining a GARN with solar? My specific question is whether the chemicals in the GARN would lead to buildup in the solar panels if one were to implement a drainback system?
GARN and solar
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Como
Minister of Fire
Your chemical pack depends on your water supply, so a lot of differences.
The sheer size of the array to make a noticeable contribution may be the bigger issue.
The sheer size of the array to make a noticeable contribution may be the bigger issue.
Thanks David. The array will supply what it can. It will definitely contribute. If not enough, fire up the GARN. As for the chemical pack, the original pack is the same for all units. So I am not convinced that the adjustments will make that much difference unless one's water is way off the "norm". Perhaps someone else has a comment.
Jim K in PA
Minister of Fire
Since none of the chemicals that are appropriate to use in the GARN are dissolved solids, there should be no "build up", but perhaps you could be more specific about your concern? You can also contact PrecisionChem, the company that does the water testing for GARN. www.precisionchem.com They can give you more specific answers relative to the chemical package and solar panels.
David's comments are worth considering with respect to panel sizing. Calculate the Btuh output of your panels, and then see what level of contribution to temperature rise you will get in the storage tank. I looked into this for my WHS2000, but decided that it would be far more productive to connect the drainback system directly to an indirect water heater for summer DHW supply, then switch back to the GARN for winter DHW supply. I do not have enough room nor budget for the amount of panel surface area to make any reasonable dent in the temperature of the GARN from solar, but perhaps you do.
Let us know what kind of solar system you set up. We love to learn.
David's comments are worth considering with respect to panel sizing. Calculate the Btuh output of your panels, and then see what level of contribution to temperature rise you will get in the storage tank. I looked into this for my WHS2000, but decided that it would be far more productive to connect the drainback system directly to an indirect water heater for summer DHW supply, then switch back to the GARN for winter DHW supply. I do not have enough room nor budget for the amount of panel surface area to make any reasonable dent in the temperature of the GARN from solar, but perhaps you do.
Let us know what kind of solar system you set up. We love to learn.
Jim - good idea on contacting PrecisionChem directly. My concern comes from the long-term evaporative effects of drainback systems. My thought is that as a system drains at dusk (when the solar pump stops) that surface tension will keep some of the liquid (and any suspended particles). The heat from the panels will quickly evaporate the water leaving the "scum" behind. Over time this "scum" will accumulate and eventually lead to reduced flow. This is speculation based on reading and pseudo science. ;^) Only the cleanest of water would eliminate this - and one could argue that may not even be true.
As to the panels, my thought was that the solar panels only need to maintain around 120 degrees for the shoulder and summer seasons. Standby losses would obviously be less because of the much warmer ambient air temperatures. So the panels would only need to replace standby losses and the DHW requirements since there will be no space heating to start with. Also the GARN will not be starting with cold water but merely transitioning over from wood to solar. Is my logic that out of whack? :^)
As to the panels, my thought was that the solar panels only need to maintain around 120 degrees for the shoulder and summer seasons. Standby losses would obviously be less because of the much warmer ambient air temperatures. So the panels would only need to replace standby losses and the DHW requirements since there will be no space heating to start with. Also the GARN will not be starting with cold water but merely transitioning over from wood to solar. Is my logic that out of whack? :^)
Como
Minister of Fire
Do some numbers, do some trial runs. How much wood do you need a day to keep it at I would have thought at least 140.
I have high solar gain, some time back I worked out I would need 6 10'x4' panels to make it logical.
Buys a lot of wood.
I have high solar gain, some time back I worked out I would need 6 10'x4' panels to make it logical.
Buys a lot of wood.
Well if you are going to get all technical on me... ;^)
Two things. The panels are bought and installed already. Just not hooked up yet. In my favour - they were used so the capital outlay has not been too bad. Don't think I need 140. Tend to run "cooler" showers and 120 is considered the norm so I thought 100 -110 would suffice. I guess my logic may be trumped by your science. Bummer. For me however, this is more then being just about numbers. I am really trying to cut back our carbon footprint. I have what I call eco-dollars. I try to get the bang for the buck out of them. This is next on my list. Of course, I am not always right - my wife has a strong case for me rarely being right - but that is a different discussion unto itself.
To my mind - I might as well try hooking the solar up to the GARN and see what happens. The issue still remains whether to go with a drainback system and no heat exchanger issues or closed loop system with anti-freeze and a heat exchanger.
Two things. The panels are bought and installed already. Just not hooked up yet. In my favour - they were used so the capital outlay has not been too bad. Don't think I need 140. Tend to run "cooler" showers and 120 is considered the norm so I thought 100 -110 would suffice. I guess my logic may be trumped by your science. Bummer. For me however, this is more then being just about numbers. I am really trying to cut back our carbon footprint. I have what I call eco-dollars. I try to get the bang for the buck out of them. This is next on my list. Of course, I am not always right - my wife has a strong case for me rarely being right - but that is a different discussion unto itself.
To my mind - I might as well try hooking the solar up to the GARN and see what happens. The issue still remains whether to go with a drainback system and no heat exchanger issues or closed loop system with anti-freeze and a heat exchanger.
May be a silly idea but what if you only half filled the GARN say 500-750 gals. for solar gain during the non-heating season?
Como
Minister of Fire
Now if you have them anyway, well a different situation. I was just looking at the total investment cost new. And from a Carbon Footprint point of view I would be better burning wood.
The type of system I think depends more on your local situation that using the Garn. We have extreme cold but big fluctuations and high solar gain so what would work for me may not for you.
140F was on the basis of 120F at the tap, taking into account losses in the system.
Good luck. Let us know what the end result is, theory is one thing, actuality another.
The type of system I think depends more on your local situation that using the Garn. We have extreme cold but big fluctuations and high solar gain so what would work for me may not for you.
140F was on the basis of 120F at the tap, taking into account losses in the system.
Good luck. Let us know what the end result is, theory is one thing, actuality another.
afblue
Feeling the Heat
Since you already have the solar, I would plumb it goes directly to an indirect DHW tank, then just use the Garn tank as a heat dump, if it ever gets too hot. Ultimately what you are trying to do is get DHW as close to 100% of the time as possible, or potentially not have to fire the Garn for the longest time of the year possible, not quite saving wood. I am not an expert on efficiencies of solar systems, but if you have to use a heat exchanger to separate it from the Garn, you might as well make it a antifreeze system. The drain back tank adds expense but the biggest one is the fact that you need a large pump to initially overcome the startup head of a drainback system, which is a more expensive pump, and more electricity to run it.
gorbull said:
Hmmmm... interesting thought but could make the water treatment a bit tricky. Hats off for thinking outside the box. I will keep your thought on the back burner for now. Thanks for the contribution however.
afblue said:
Six panels is in the range of 20 gallons of drainback, that might be less than the expansion of the garn from cold to hot, so the garn can handle that without a separate tank. The garn is also open, so an additional tank would be pointless. This assumes you can mix garn and drainback water of course.
If the panels are located perfectly, just above the water level of the garn, then the pump doesn't need to be any bigger than you would otherwise want to use with six panels. The extra head is not wasted once the panels and return fill with water because the falling water balances the rising water, so electricity can be less than a glycol system.
Benjamin - you have obviously read the response I was referring to on the other thread. Unfortunately, the panels are located below the GARN and for that reason, I would be looking at a remote tank. The main reason I was looking at a drainback system was so I could use the GARN water and avoid the need of a heat exchanger and gain the efficiency of water versus glycol as well. Perhaps glycol (closed loop with heat exchanger) is the way to go...
Como said:
I am interested in your opinion that burning wood would be better then solar from a carbon footprint point of view. How do you figure that?
As for the 140F - you have an excellent point about system losses. Thanks for that thought.
I will inform whenever I get this thing together!
I'm lost, how are you going to get away without a heat exchanger if the panels are below the garn? If the water is shared the air in a remote tank will get moved to the garn and anything lower than the garn will be full of water, and eventually freeze?
You could forget about drainback and use the panels just in the summertime, pretty risky freeze wise though.
You could forget about drainback and use the panels just in the summertime, pretty risky freeze wise though.
I was going to have a separate tank located below the panels. It would be buried and insulated to prevent freezing. When the pump was running it would pump into the GARN. One way valves would stop the GARN from draining into the panels and separate tank. This, of course, may be wrought with problems / errors in thought. The lines are buried and insulated.
afblue said:
You have hit the nail on the head. I am attempting to NOT have to fire the GARN for the longest period of time. What I don't get is if the GARN is already at temp - would the panels not be able to keep up with DHW use and standby losses? Given the fact that the GARN is very well insulated - and that the summer temps would limit losses it just does not seem like the panels would have that much of a problem keeping up. However the thought of feeding the DHW directly and using the GARN as a heat dump has crossed my mind.
Como
Minister of Fire
I agree with the separate smaller tank, would recover much much quicker, I do not have my calcs to hand but putting solar btu's into a large tank takes a long time to do anything.
Solar panels have to be manufactured, transported, installed.
They need electricity to operate, so does a Garn burning wood so lets call that a wash.
Wood where I am is both plentiful and need of being used, Beetle Kill, so it either burns/rots in situ or gives me energy.
Solar panels have to be manufactured, transported, installed.
They need electricity to operate, so does a Garn burning wood so lets call that a wash.
Wood where I am is both plentiful and need of being used, Beetle Kill, so it either burns/rots in situ or gives me energy.
OK - I see your point about the carbon footprint. You failed to mention that rotting would also contribute both CO2 and methane.
"While CO2 is the most important greenhouse gas – mainly because there is so much of it – it is not the only greenhouse gas we need to worry about. Methane (CH4) is also a very powerful greenhouse gas, although it has a much shorter lifetime in the atmosphere than CO2. Like CO2, methane comes from both natural and man-made sources. Natural sources include rotting wood and wetlands, while human activities that emit methane include agriculture and waste deposits. Other greenhouse gases also contribute to man made climate change. They include nitrous oxide (N2O) and several synthetic compounds from industry containing fluorine."
from http://www.atmosphere.mpg.de/enid/1w8.html
It appears that you may very well be right. I guess it would depend upon how long the panels run and how efficient getting one's firewood is. (Chainsaw, skidder / tractor, transportation) would all make firewood less appealing. Firewood that would otherwise decay certainly has merit. My two cents.
"While CO2 is the most important greenhouse gas – mainly because there is so much of it – it is not the only greenhouse gas we need to worry about. Methane (CH4) is also a very powerful greenhouse gas, although it has a much shorter lifetime in the atmosphere than CO2. Like CO2, methane comes from both natural and man-made sources. Natural sources include rotting wood and wetlands, while human activities that emit methane include agriculture and waste deposits. Other greenhouse gases also contribute to man made climate change. They include nitrous oxide (N2O) and several synthetic compounds from industry containing fluorine."
from http://www.atmosphere.mpg.de/enid/1w8.html
It appears that you may very well be right. I guess it would depend upon how long the panels run and how efficient getting one's firewood is. (Chainsaw, skidder / tractor, transportation) would all make firewood less appealing. Firewood that would otherwise decay certainly has merit. My two cents.
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