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-   -   Large drainback solar hot water project (https://ecorenovator.org/forum/showthread.php?t=3276)

ESharp 10-21-13 07:12 PM

Large drainback solar hot water project
 
Over the past year Iíve been picking away at a large ground mounted solar hot water system for my house. I got a lot of inspiration to do it from a few members of this forum and Garyís Build-It-Solar $2k drain-back design. Iíll make a few separate posts to get my count up so I can upload some pictures.

ESharp 10-21-13 07:15 PM

It all started when I was browsing Kijiji (like Craigslist) last September and noticed some used panels for sale. There was a picture of five of them and I thought great, five should be able to do most, if not all, of my domestic hot water. I called the fellow up and it turned out he had 16 8íx3í panels! They were older ones removed from an apartment building while the roof was being redone and I guess they thought it was not worth it to put them back. I bought the whole lot for $1000 and the possibilities for my project got a bit larger.

ESharp 10-21-13 07:20 PM

I had to start thinking where I could fit 16 panels. 16 was too many for the roof and with that many panels, contributing to winter heating was my goal. The roof is at ~25deg pitch, whereas 65-70deg would be preferred. I decided on a ground mount structure off to the side of my house. Fortunately my neighbours are through the trees and it is not in my windows view plane.

ESharp 10-21-13 07:36 PM

2 Attachment(s)
After a bit of layout work I decided I only really had space for 12 panels, even on the ground. The structure is 40í long, with 10 post holes (4 sections, each 10í long). The design is similar to Daoxís. Post holes are dug below the frost line and concrete poured into tubes with galvanized 4x4 post supports set into the tops. I tried to make it very forgiving on construction tolerances (post locations, lumber straightness, etc). Once the posts were set, I used lines to achieve one flat plane with fully adjustable 2x4ís along the sides of the posts. I built this over the fall of last year.

http://ecorenovator.org/forum/attach...1&d=1382402018

http://ecorenovator.org/forum/attach...1&d=1382402014

ESharp 10-21-13 07:52 PM

Tank
 
1 Attachment(s)
I really liked the simplicity of Garyís drainback system and the large low cost storage tank. I went with a 6í long x 3.5í wide x 4í tall tank as that was the biggest I could reasonably fit in my mechanical room. It holds ~350 gallons. To maximize water space (and save a bit of money) I only used 1Ē of poly-iso to line the interior of the tank, regular fiberglass batt is between the 2x4 reinforcements on the exterior. Unfortunately I didnít take any pictures during construction.

http://ecorenovator.org/forum/attach...1&d=1382403038

Daox 10-22-13 08:33 AM

Awesome stuff Eric! Cant wait to see more. :thumbup:

I'm still widdling away at my project one baby step at a time. :)

ESharp 10-22-13 10:39 AM

4 Attachment(s)
Thanks Daox, I'll be posting in bits as I have time. It has been certainly the same for me, slow progress, step by step. These systems are more work then they first appear. I'm still not quite finished.



Although the panels were in reasonable shape, the demo crew had unfortunately cut the header pipes flush with the side of the panel frame. In order to make any connections I had to install couplings to all 4 corners. This involved drilling the rivets off the back side, and flipping the insulation up to allow access to clean up each header end. I soldering the new couplings on and re-riveted the cover back on. It was an annoying and tedious job.

Mounting the panels was the fun part since I could finally see some tangible progress. I riveted pieces of aluminum angle to the sides and screwed those down into the cross-members of the structure. I made 2 banks of 6 panels each. They both have slight slopes back to the supply line. The banks are plumbed with a parallel-reverse-return configuration to help with balanced flow. I used 1Ē PEX for the main supply and return, but 1Ē copper to connect the 2 banks since PEX has quite a bit different larger thermal expansion coefficient.

After I got one bank on and soldered up, I sent a bit of water through with the hose. Since the panels had been sitting in the sun for a while, steam was the result!

http://ecorenovator.org/forum/attach...1&d=1382456146

http://ecorenovator.org/forum/attach...1&d=1382456146

http://ecorenovator.org/forum/attach...1&d=1382456146

http://ecorenovator.org/forum/attach...1&d=1382456146

Daox 10-22-13 11:37 AM

Great stuff. 384 sq/ft of panels is wonderful! I was quite happy when I got my ~200 sq/ft of panels.

I also had/have to do the same thing with my panels. Each had to be disassembled, cleaned and pressure tested, fittings soldered on every corner to I can set them up to connect to each other. The un-installer did the same thing, zipped them with the sawzall.

randen 10-22-13 06:07 PM

Esharp

Nice to see another Canuck toiling away saving money collecting solar. If I may ask what are you going to do with all that heat. Heated floors, indoor pool, hot water fan center,??

Randen

ESharp 10-22-13 06:27 PM

3 Attachment(s)
I currently have an older oil forced air furnace which Iíd love to stop buying oil for :) Iíve installed a water-to-air heat exchanger (Finned Coil Water to Air Heat Exchangers) in the return plenum and the heating loop pump circulates water directly from the storage tank through it. I realize that relatively low-temp solar isnít an ideal supply for this, but installing hydronic in-floor heat is a project for another day. The exchangers are typically used for those with back-yard wood boilers and are pretty decently priced. We typically turn the heat down quite low at night and itís also off during the day while away. This gives a bit larger of a delta-t to work with.

As for the summer, I think Iím going to need a pool :)

Here are some pictures of the plumbing. I followed Garyís design fairly closely here. I am using a TACO-011 for the solar circulating pump. The smaller pump is a TACO-005 for the heating loop. The domestic supply to the hot water tank is a 300í coil of 1Ē PEX. I plan to add a few spacers to spread the coil out a bit in the tank.

http://ecorenovator.org/forum/attach...1&d=1382484046

http://ecorenovator.org/forum/attach...1&d=1382484046

http://ecorenovator.org/forum/attach...1&d=1382484046

Mikesolar 10-22-13 06:41 PM

Good work Eric, how will you use the heat in the summer because that is the biggest issue. Given what I see there, I would use about 6' of copper to keep the heat away from the pex. You may be surprised (or not) by how much heat will flow into the pex. The copper can help a bit.

BTW, where in NS are you. My cottage is near Chester.

Mikesolar 10-22-13 06:46 PM

There is a very neat tank called the ROTEX from Germany and they use 3-4 parallel loops of 1/2" pex as the DHW HX in the tank. Not much different from what you have done.

ESharp 10-22-13 06:47 PM

Controls
 
2 Attachment(s)
I decided to use an Arduino for the controls. Since I wanted to integrate the solar with my heating system, I figured it would give me plenty of flexibility. Iím using one wire DS18B20 digital temp sensors for the inputs and a relay board (http://arduino-info.wikispaces.com/ArduinoPower) to control the pumps and furnace. There are four relays, one for the solar loop pump, one for the furnace loop pump, one to turn on the furnace fan, and the last is in parallel with my house thermostat. This allows three modes of operation for heating the house.

First mode/stage would be solar only. The water in the tank is hot enough to comfortably heat the return plenum air, so just the circulating pump and the furnace fan are switched on. Second stage is if the stored water is still warm, but not sufficient to provide all of the heat to maintain the house temperature. The oil burner will switch on, but Iíll also keep the circulating pump on. Third stage the water has cooled down to a point where it is pointless to circulate it. Iíll switch off the pump relay, and keep the oil burner on.

I also bought an Ethernet shield to hook everything up to the internet. I got most of the programming from Natefulís Differduino site: Arduino Differential Controller | Arduino Solar Hot Water | Differduino | Nateful . Iím connected into Xively (previously Cosm, previously Pachube) to log data and can also control the thermostat set-point and pumps remotely. You can see the feeds here: https://xively.com/feeds/42603

Most of them arenít hooked up yet, Iím kind of controlling things manually for now until I have everything set-up. Wiring is also still a bit messy.

http://ecorenovator.org/forum/attach...1&d=1382485264

http://ecorenovator.org/forum/attach...1&d=1382485264

ESharp 10-22-13 07:11 PM

Quote:

Originally Posted by Mikesolar (Post 32568)
Good work Eric, how will you use the heat in the summer because that is the biggest issue. Given what I see there, I would use about 6' of copper to keep the heat away from the pex. You may be surprised (or not) by how much heat will flow into the pex. The copper can help a bit.

BTW, where in NS are you. My cottage is near Chester.

Thanks Mike,

Yeah I will definitely have an abundance of extra energy in the summer. A pool or hot tub is a possibility. It is a drainback system, so if the tank is maxed I just need to turn the pump off.

Perhaps I could make a few modifications and get some steam to power a turbine, haha.

I am a little concerned about the PEX connection at the beginning of the return. If I have a failure due to heat it will be there. One aspect helping me is that the loop will be un-pressurized in stagnated conditions. It is supposed to be good for 100psi @ 180F.

Chester is a beautiful place to have a cottage. I live close to Peggy's cove.

Mikesolar 10-22-13 07:20 PM

I guess it was not as much fun to buy the panels from Thermo-Dynamics in Burnside, haha, but that is not what this forum is about, it seems.

Many years ago I had dreamed up and made a steam turbine for just that purpose using a tesla turbine but the amount of heat needed was pretty high to get much out of it, then you have to capture the condensate but it was a lot of fun to make.

You will have to just see how it goes with the pex. Although it is rated at 100/180F, this is just the agreed upon standard. It will take more temp at less pressure or vise versa. If it is a good tubing like REHAU, it may have higher capabilities.

Actually the cottage is near Blandford on the Aspotogan, lovely sunsets looking west (ish)

ESharp 10-22-13 07:30 PM

Those are good panels, I've even taken a tour of their shop, but at $1k a pop, they were are a bit out of the budget.

The Aspotogan is just across the bay from me :)

Mikesolar 10-22-13 07:32 PM

I may be forced (by curiosity) to drop in next time I am down, haha.

ESharp 10-22-13 07:53 PM

:) Certainly, love to give you a tour.

randen 10-22-13 08:36 PM

ESharp

This is some good stuff. I've been collecting solar for about 4-5 yrs. Still amazed at how much heat is available. In-floor heating just rocks. Using an arduino for controlling all aspects AWSOME!! Love that you have already installed the Water to air HX. Is there a 2 speed fan?? It will be interesting what your system will do. I'm on the edge of my seat.

Randen

ESharp 10-27-13 09:14 AM

4 Attachment(s)
The furnace just has a single speed fan, and from what I can tell so far I'll need all the air flow I can get with the low temp water.

Here are a few pictures of some insulating I did yesterday. Iím using 1Ē thick EPDM closed cell foam made by Areoflex (http://www.aeroflexusa.net/products/aerocel_sspt/). Itís a bit pricey here at ~$3 a foot, but Iíve got a significant amount amount piping outdoors. It is also UV resistant and theoretically does not require any additional covering.

http://ecorenovator.org/forum/attach...1&d=1382882828

http://ecorenovator.org/forum/attach...1&d=1382882852

For the Ďtrenchí to the house Iím using 2Ē rigid XPS board. I had to make a compromise/sacrifice here since itís a drainback system the trench becomes a protrusion closer to the panels. Iím relying on the rigid box to help maintain a gradual slope back to the basement. I plan to do some grading to cover it, but the pipe and insulation is definitely not below the frost line. Time will tell whether this was a mistake.

http://ecorenovator.org/forum/attach...1&d=1382882879

http://ecorenovator.org/forum/attach...1&d=1382882911

ESharp 10-27-13 09:44 AM

One issue I’m working through at the moment is getting reliable readings from the temperature sensors. As soon as I plug in a fourth sensor, I stop getting readings from all of them. I’ve done a bit of googling and I apparently chose the least recommended configuration for longer wire runs with multiple One Wire sensors, the star, or hub. This is when each sensor is on it’s own wire and they all connect back to the one spot next to the arduino. For larger networks of sensors a daisy-chain configuration is recommended.

Guidelines for Reliable Long Line 1-Wire Networks - Tutorial - Maxim

osolemio 09-10-20 05:45 AM

ESharp, how is it going with your project, all these years later? Is it still working?

I am researching the drainback principle. Where I have built a few systems, most of every system is a closed system, with anti-freeze (glycol). They do normally NOT drain back.

I am working on combining various technologies, to take solar thermal to a new level of both efficiency, simplicity as well as reliability (and less maintenance)

solarhotairpanels 12-24-20 06:18 PM

Stag temps can go over 180... keep an eye on it.
You may have to run 3/4 copper for a few feet coming off the collector then back to Pex

solarhotairpanels 12-24-20 06:25 PM

How's everything in Hong Kong? Hope you and your family are staying healthy.

Did you build a solar hot water drainback system? If so how'd you make out with it?

osolemio 12-27-20 02:28 AM

Quote:

Originally Posted by solarhotairpanels (Post 63360)
Stag temps can go over 180... keep an eye on it.
You may have to run 3/4 copper for a few feet coming off the collector then back to Pex

I didn't get to it yet. Well, I have started sourcing parts, but an ongoing pandemic has slowed things down a bit, to put it mildly. Also, starting a company in HK is a longwinded process. Just getting a business account (not even with a credit, just a savings account), takes months.

About the temperature, I am not using PEX or any other plastics in the primary circuit. I would only use PEX for underfloor heating and some heat storages, where I can control the temperature. All primary circuits are copper or brass mainly. Trying to stay away from iron and steel.

The drainback will be a closed system, understood as in - the air in the system will normally not vent. If it's an open system (the air can enter and exit), then the air (and then water) will have oxygen added to it. This is not good in the long run, with regard to corrosion and such. So it will all stay in tanks, some of them with partly air in them.

solarhotairpanels 12-27-20 06:54 AM

Drainback system
 
Ok, sounds good and good luck with your new business.

Try to stick with 3/4 pipe because the water will drain back much faster with the larger diameter.

Haven't had any air issues corroding my pipes. System has been functioning now since 2010. System can be flushed with vinegar using a sump pump submerged in 5 gal bucket.

Similar to tankless water heaters your system should be flushed at least once per year to remove rusty water and contaminants. Red hot water passing thru copper creates rusty water.

When building your piping install flush kits. All a flush hit is is a water valve with a shut off allowing you to connect a garden hose to the flush valve. You want to install 2 flush valves total. One on the outbound pipe leading TO collector, one on the return pipe FROM collector.

How to flush solar hot water drainback collector system:
Drain system
Dump 3 gallons of vinegar into 5 gallon bucket
Put sump pump into bucket
Connect a garden type hose from sump pump to pipe (flush valve) that goes out to collector
Connect another hose from collector (flush valve) return pipe back to 5 gal bucket
Turn on sump pump and pump vinegar thru system for 30 minutes
Dump bucket and replenish with fresh water
Run the pump again with the fresh water in bucket to flush out remaining rusty contaminated water

All done!

Take care and don't forget to post pictures back in here of your system especially whatever your plans are for the parabolic setup. Like to see that.

osolemio 12-30-20 01:57 PM

Quote:

Originally Posted by solarhotairpanels (Post 63376)
Ok, sounds good and good luck with your new business.

Try to stick with 3/4 pipe because the water will drain back much faster with the larger diameter.

Haven't had any air issues corroding my pipes. System has been functioning now since 2010. System can be flushed with vinegar using a sump pump submerged in 5 gal bucket.

Similar to tankless water heaters your system should be flushed at least once per year to remove rusty water and contaminants. Red hot water passing thru copper creates rusty water.

When building your piping install flush kits. All a flush hit is is a water valve with a shut off allowing you to connect a garden hose to the flush valve. You want to install 2 flush valves total. One on the outbound pipe leading TO collector, one on the return pipe FROM collector.

How to flush solar hot water drainback collector system:
Drain system
Dump 3 gallons of vinegar into 5 gallon bucket
Put sump pump into bucket
Connect a garden type hose from sump pump to pipe (flush valve) that goes out to collector
Connect another hose from collector (flush valve) return pipe back to 5 gal bucket
Turn on sump pump and pump vinegar thru system for 30 minutes
Dump bucket and replenish with fresh water
Run the pump again with the fresh water in bucket to flush out remaining rusty contaminated water

All done!

Take care and don't forget to post pictures back in here of your system especially whatever your plans are for the parabolic setup. Like to see that.

3/4" is my favorite for most work, so I agree. The trick is some times valves, flow meters and such.

There won't be any "rusty water" here, and that is because my systems will be closed. With no oxygen added, no corrosion is going on. Having an open vent is easier, but I just don't want the air to be added. Your system has lasted 10 years so far, but then you flush it with vinegar, and replace the water I presume. I won't need to.

And yes, there will be plenty of valves. Not just a few, but I need a lot of valves and places to connect, mainly as I am experimenting. I need to be able to shut off parts of the system. I will also be using conical connections, so I can change the design as needed, without throwing out a lot of pipe and other parts. As much as I love press, it doesn't have an "edit" or "undo" function.

osolemio 04-27-21 04:43 AM

Quote:

Originally Posted by solarhotairpanels (Post 63376)
Ok, sounds good and good luck with your new business.

Try to stick with 3/4 pipe because the water will drain back much faster with the larger diameter.

Haven't had any air issues corroding my pipes. System has been functioning now since 2010. System can be flushed with vinegar using a sump pump submerged in 5 gal bucket.

Similar to tankless water heaters your system should be flushed at least once per year to remove rusty water and contaminants. Red hot water passing thru copper creates rusty water.

When building your piping install flush kits. All a flush hit is is a water valve with a shut off allowing you to connect a garden hose to the flush valve. You want to install 2 flush valves total. One on the outbound pipe leading TO collector, one on the return pipe FROM collector.

How to flush solar hot water drainback collector system:
Drain system
Dump 3 gallons of vinegar into 5 gallon bucket
Put sump pump into bucket
Connect a garden type hose from sump pump to pipe (flush valve) that goes out to collector
Connect another hose from collector (flush valve) return pipe back to 5 gal bucket
Turn on sump pump and pump vinegar thru system for 30 minutes
Dump bucket and replenish with fresh water
Run the pump again with the fresh water in bucket to flush out remaining rusty contaminated water

All done!

Take care and don't forget to post pictures back in here of your system especially whatever your plans are for the parabolic setup. Like to see that.

Update here is that I am still working on it. Not many pictures to show just yet.

Right now, part of the focus is on installing ducting in the house, and the pipes for hot water. Since there are 3 floors and rooftop, and all hot water comes from local electric instant water heaters, we need to route the pipes also (for hot water).

The A/C ducting will be built by isolation board (like styrofoam), with wooden on top of it (I think 3/8 inch). I won't even paint the wood, it will be a visible feature of the house. Which is not a bad thing, as the house will be some kind of proof of concept anyway.

Sourcing parts is not easy. We buy from various places, either local shops or online. For several challenges, there are so many ways to do it, and so many products, that the decision becomes hard by simply having to pick parts/methods! Here is an example:

The ducting will have variable control to dampen the flow to rooms where conditioned air is not needed. Also, bathrooms and the kitchen fan will have fans replaced by valves. Sensors of temperature, humidity, CO2 level and more will modulate inlet or outflow valves.

Initially, we were looking at which motor controlled valves we would use inside the ducting. Now we decided to combine louvre registers and valves. This means it will be much cheaper, and also simpler to build and maintain. Those louvres with servo modulation costs around 25-30 USD including register, motor and all. And they are silent (the ducting valves were surprisingly noisy, probably from the gear box).

CO2 sensors will help detect occupancy, and thus guide air where it's needed the most. Humidity will be used especially in bathrooms and the kitchen. And we are working on a solution where one or more sensors will detect foul air, to ensure bathrooms are vented as needed, also when it's not from humid shower air (!!!).

It will all be automatic, comfort, clean air and hot water year round.

And there is much more. Dishwasher will be installed, and it will use hot (solar) water. The same for laundry, it will be switched to dual cold/hot. It will all save lots of energy. And to ensure minimal water waste, a return pump will run in certain cases to ensure hot water is available throughout without having to let the water run for a while to become hot.


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