Off Grid Hot Water - Solar Vacuum Tubes

xtry51

xtry51

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So, I started a chat with our resident off grid expert Gomer, but figured I should post a thread here. My wife's grandfather (hither to referred to as Gramps :)) is all about going off grid and installed a kit from Amazon linked below for a vacuum tube solar collector. Well, I saw him last week and he can't stop talking about how awesome it is. After looking at what he is generating even in these super short days of Nov, I have to say I was impressed. He is producing 1/3rd of all his heat and hot water needs from the single kit (measured by comparing his previous electric use from last year to this year since installation). Last week when I was there he was producing enough to heat the top of the holding tank to 125F. I think the bottom was 90F while I was there.

Gramps lives in NE CT. I live in S NH, making my winters a little colder meaning I'll have to go deeper into the glycol territory than he is. This lowers the thermal efficiency of the system. So here's my main question. Does anyone know of someone using this type of setup in VT, NH or ME? I'm just trying to get an idea on what scale I would need to go and get some data points if they are out there.

We currently use oil for hot water (100% house heat from wood). So I can keep the oil to use as a backup and fill in for those cloudy weeks. I'm trying to establish a long term plan for going complete off grid for our house. Right now this year I have to do a new metal roof and install solar in the garage to make it stand alone off grid as a test. So this is a 2019 or 2020 project if I think it's viable this far north.

I am going to see Gramps this weekend again for Thanksgiving. I will take pics of his setup and post them here when we get back for reference incase anyone is interested. His setup does include some parts not in the kit below as he was retrofitting the whole thing into a 1700s farm house that required some initial plumbing "simplification" and will require a lot more work to streamline once he expands the current setup. Whoever did the plumbing in that house over the years loved Rube Goldberg and probably owned stock in copper pipe manufacturing :D

Amazon Kit:
Amazon product ASIN B00HP84GVO
 
The evacuated glass tube heat pipe technology is very efficient. The manufacturer may be of help in sizing your system. I do know they have much more output per sf than the old fashioned panels. A minimal system gives you a lot of hot water.
The catch is higher cost up front.
 
There is no link to the amazon unit he used in your OP. I would be interested in this as well for northern NH use. I never did get around to contacting David about the wood gasifier but still plan on making the generator wood gasifier. I will try to do some research with you on this because I am also looking to have an off grid solution for NH in the next 4 or 5 years.
 
xtry51 said:
So, I started a chat with our resident off grid expert Gomer, but figured I should post a thread here. My wife's grandfather (hither to referred to as Gramps :)) is all about going off grid and installed a kit from Amazon linked below for a vacuum tube solar collector. Well, I saw him last week and he can't stop talking about how awesome it is. After looking at what he is generating even in these super short days of Nov, I have to say I was impressed. He is producing 1/3rd of all his heat and hot water needs from the single kit (measured by comparing his previous electric use from last year to this year since installation). Last week when I was there he was producing enough to heat the top of the holding tank to 125F. I think the bottom was 90F while I was there.

Gramps lives in NE CT. I live in S NH, making my winters a little colder meaning I'll have to go deeper into the glycol territory than he is. This lowers the thermal efficiency of the system. So here's my main question. Does anyone know of someone using this type of setup in VT, NH or ME? I'm just trying to get an idea on what scale I would need to go and get some data points if they are out there.

We currently use oil for hot water (100% house heat from wood). So I can keep the oil to use as a backup and fill in for those cloudy weeks. I'm trying to establish a long term plan for going complete off grid for our house. Right now this year I have to do a new metal roof and install solar in the garage to make it stand alone off grid as a test. So this is a 2019 or 2020 project if I think it's viable this far north.

I am going to see Gramps this weekend again for Thanksgiving. I will take pics of his setup and post them here when we get back for reference incase anyone is interested. His setup does include some parts not in the kit below as he was retrofitting the whole thing into a 1700s farm house that required some initial plumbing "simplification" and will require a lot more work to streamline once he expands the current setup. Whoever did the plumbing in that house over the years loved Rube Goldberg and probably owned stock in copper pipe manufacturing :D

Amazon Kit:
Amazon product ASIN B00HP84GVO
Click to expand...

Can you re-post the link?
 
Here are some pics of the system including temps. T1 is bottom of storage, T3 is top of storage and T6 is the manifold temp. These were taken right as sun fully set on Saturday. Tubes get 5 hours of direct sunlight and 3 hours of partial sunlight (heavy woods). There are 30 tubes in a single manifold and a 80gal system. He said they ship 40 tubes so you have extra in case of breakage. All of his arrived undamaged.

There are 3 zones in a 1760s 2400sqft farmhouse. Dirt basement, stone foundation. This array is heating one of the zones (top zone in pic, largest volume one in house) by itself set to 70F during day and in morning right now he said the zone will be about 66F in morning. 30% glycol mix.

He has the bumble bee set to constant circulation as long as water temp is above 90F. Water is ciculated through previously existing standard baseboard heat.

This is a temporary install as he wanted to get a feel for a winter before expanding. Eventually in the spring he will add an additional 50 tube system to heat the other two zones and move to a larger bulk storage. He is making a pad for the final placement of all the tubes and a proper steel frame to hole them up off the ground at least 2 ft to avoid snow.


20171125_164317_HDR.jpg 20171125_164006.jpg 20171125_164043.jpg 20171125_162750.jpg 20171125_164021.jpg 20171125_164032.jpg 20171125_164251.jpg 20171125_164302.jpg


20171125_164317_HDR.jpg 20171125_164006.jpg 20171125_164043.jpg
 
Forgot to add that the system has an option for freeze prevention where you can set a lower bounding temperature on the manifold (T6). Upon hitting lower bounding temp will turn on the manifold pump and regulate flow from holding tank to maintain min temp in manifold to prevent icing. He has his set to 20F right now based on his glycol content.
 
I agree it's more than "rough" at this point. He was just going for proof of concept. I would need to plan whatever I did around a solar array to power it. My current plan is having two solar systems independent. One for the house and one for the garage. Keeping both with as many common parts as possible. I'm still trying to find someone at my latitude or higher to meet in person and find out what the scale needs to be.
 
xtry51 said:
Forgot to add that the system has an option for freeze prevention where you can set a lower bounding temperature on the manifold (T6). Upon hitting lower bounding temp will turn on the manifold pump and regulate flow from holding tank to maintain min temp in manifold to prevent icing. He has his set to 20F right now based on his glycol content.
Click to expand...

Where we are in the White Mts (Plymouth, NH area) the temps regularly drop to -15F....so that'd be a lot of pumping, or a lot of glycol
 
40% glycol is enough for that temp. 50% is good to -30F. I think 45% would be my target to be safer but not sacrifice too much heat capacity and transfer. 50% has 12% loss of carrrying capacity versus 30%. Its a fair amount but honestly if you just talking about adding 10-15 extra tubes to offset the loss, the overall cost increase is really not that much.

At 45% I can set the low bound safety temp to -20F and be confident it will only need that on the harshest of nights.

Just like solar, there's no escaping the need to plan for cloudy days and a few days of extreme temps on both ends of the scale. Honestly the problem larger than winter is how you control the overage on a large system scaled for 365 coverage in the summer at peak temps and sun duration. That's a LOT of BTUs to store or dump. Likely I'll need to pull tubes out late spring to early fall to limit the amount I'm generating.
 
Too much capacity....that would be a good problem to have.
And a tarp would go a long way towards decreasing your capacity without plumbing changes!
The Taco HEC-2's were discontinued. I've been looking at higher efficiency circulator pumps for our heating systems
 
Yeah I was thinking about making 20ga stainless steel covers with foam backings for sections, but then gramps showed me the tubes are quick disconnect, so it's likely better to just remove them during summer.

As a note, water does not flow through the tubes. The tubes have a copper conductor rod inside the vacuum tube that conducts heat into the manifold through which the water flows. No part of the tubes actually touch the water.

Also even with this setup he had way too much capacity in the summer when he set it up. Through September it was creating 100% of their hot water usage and excess was being dumped into their pool. Laundry, showers, dishwasher and potable water.
 
This summer I took down 4 hot water solar panels and aluminum angle iron rack stand from my parents roof. I put this system up when Jimmy Carter was president. The stone lined tank in the basement leaked so we never replaced it and stopped using it as a working system at that time. The pump set up is on the wall in the basement next to the tank . If anyone here wants this setup the panels are in the driveway neatly stacked, the pump set up i can take down also. No guarantees but it had glycol in it and when operating we had 150° water coming off the roof. There was a strap on thermostat on the pipes on the roof that was wired into a relay with the pump. When temps dropped the pump would stop pumping. If this should be put in another forum please excuse me. As I'm a plumber, I can explain the assembly if needed.​
 

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