[Ibon]

At Mount Totumas we are already generating 7kw of eclectricity with our micro hydro system. We just completed a lodge and are approaching the maximum electricity build out.

We are at 6500 feet above sea level with strong sunlight when shining which even in the rainy season means most mornings are sunny.

It seems so silly to use electricity from the hydro to heat water and we would like to now set up an active hot water solar system for hot water use in the lodge.

We have left over construction supplies and are thinking of the following.

180 meters of 3/4 black tubing (cost $ 180) in a spiral design inclosed in a box with transparent left over roofing material and left over wood from construction. This collector will lead to a black water tank that we will wrap with left over insulation material from construction. This will be connected to the water line to the house where we have gas on demand at the moment as a back up.

So from what I have seen on the internet we need a circulation pump and a control unit and maybe some pressure release valves and other such devices to put this all together.

Does anyone have any experience with such a set up to help us out?

Would be much appreciated.

Thanks

Jeffrey

[Ibon]

Thanks Pstarr. The cost of shipping and the cost of a turn key system eliminates that option anyway. The idea is to recycle material from our last construction and take with me from the US all the valves and pumps and control unit that I cant get down there and then supply locally the rest. To get everything I need before heading down and avoiding not being able to get a key component once I am down there.

Maybe somebody went through this do it yourself process and can share their mistakes so I don't repeat them. I am not mechanically a McGuiver type, I usually have to sponge off of others mistakes.....buy the way free lodging for anyone wanting to come down and help me set this up.........

[dolanbaker]

If the tubing is plastic then it will be essential that you fit a pump, other wise the plastic will heat up enough to melt!

All you need is a simple central heating circulation pump and a "tank thermostat" attached to a piece of black metal place the thermostat inside the panel so that the sun catches the metal and wire this in series with the pump. This will allow the system to automatically pump whenever the sun is strong enough to heat up the metal sufficiently to trip the thermostat. I built one like this years ago and it worked well.

I built a "drain back" system which is open vented and placed a copper hot water cylinder inside it, the cylinder contains the hot water that is actually used in the house and the tank only contains the solar heating water. This layout allows me to have the hot water at mains pressure while the solar water is unpressurised. The drain back configuration avoids the chance of freezing in the winter.

[sunweb]

From my old memory there are basically two types of hot water system with water exposed to the outside. One has antifreeze in it and requires a heat exchanger (and if you are going to drink it, a triple wall heat exchanger) and the other is a drain down which automatically drains the water to an inside holding tank when it is freezing out side. These all need controls, thermistors and valves.
Another possibility and the one I would use would be to make a well design hot air panel. When the air is say 100 degrees it would turn on a fan and blow it across a air to water heat exchanger (radiator). The air could either circulate through the collector or could be released into the home and new air for the collector could be enter at some low point. This design requires a snap disc thermostat (cheap) and a squirrel cage fan (not to costly).
There are all kinds of designs of the net for homemade hot air panels. This to be requires the least amount of controls and protects against freezing which would bust your pipes.
Hope this opens another possibility.
Good luck.

[Longtimber]

If you have the ample roof real estate and you have modest requirements ( no dorms, 5 loads wash /day, etc) , PV Direct has many advantages, No Plumbing, Pipes to freeze, etc. You will need ~2.5 times the roof area over thermal to make up for the 17% vs 55% efficiency. 3 - 280 watt panels will do 80% of the Hot water for 2 people. Recommend at least one 80 gal tank to get thru cloudy days. What better way to store energy? Search for Possible vendors, Liberty Box/EDS , Sun Bandit, Butler PV Wand, Techluck. Expect more vendors soon. I've installed the Techluck, it 's cost effective & works beyond expectation. but there are no code standards for this yet. Since you are not changing plumbing and there is no grid connection, OFF Radar in many Jurisdictions.

[vtsnowedin]

As your in the tropics you don't have to worry about freezing. I think you can build it a a true thermo-syphon and not need any pump. The collection coil of pipe needs to come from near the bottom of your storage tank and run level or slightly up hill to the collector and then spiral always upward in the collector and back to the storage tank. the return entrance to the storage tank HAS to be through the side of the tank about a foot below the top. If you try to enter through the top of the tank it will vapor lock and not work. the tank does need a pressure and temperature relief valve and that will guard the whole system. The cold water supply will pressurize the whole system and can enter the storage supply tank anywhere. the hot water out should come out from the top of the tank. I've used similar systems for years using wood stoves as the heat source.

[sunweb]

I didn't know you where in the tropics. This would be an easy install. Good luck.

[BobInget]

Longtimber is on to something. I had several mismatched panels (used) and hooked em up to a small under-counter 120 W water heater used as a PRE-Heat for a standard 220 W 30 gallon conventional electric water heater. We now get free hot water even in winter when we had to drain our old tank-on-top solar W.H. Make sure to fuse this arrangement and don't forget that steam escape valve.

Tank on top Solar is only practical year round where is does not freeze.

The new house where I grew up in Miami, Florida came with a solar water heater as the only source of hot water. The year built, 1940. One of my 'jobs' was to clean dust off the glass once a month. If water wasn't hot enough the mother would just point to the water hose and push-broom. Even to this day houses of that pre-war era sport what appears to be a chimney at the roof's highest point. There's where the storage tank is hidden.

[Longtimber]

The main advantage is Simplicity and Low PV Prices. .. NO pipes and the panels can be remote with just 2-3 wires. The Controller should do Max Power Point Tracking and convert the DC to AC that the standard thermostat can safely switch. LOCKABLE disconnect on the PV side required and metallic ( "FMC" - Flex metallic Conduit or Metal Clad "MC" easiest ) required inside a residence. Connectors on the panels count for service disconnect as long as inside conductors DIRECTLY run to PV Power disconnect . Size 90C rated conductors for 156% of PV short current, you won't need fusing. Why 156% instead of 125%? "JBIC" Just because it's Solar and we know Nuclear power is safer! 3 - 60 cell panels = ~95Vdc @ max power , Potentially lethal just like Service Mains and since it's a separate DC power "System" , NEC 250.166 dictates System ground in addition to existing Equipment ground(s) NEC 2014 requires Arc Fault on DC > 80V, but it's not available yet, so there's an exemption on things not yet available... Mammals Water and electrons mix not, make sure pumping and tank are continuously and irreversibly grounded. note that majority of licensed electricians are not experienced or qualified with PV DC Source circuits, so better to trust a Solar contractor, PV source circuits likely will not trip on a fault, so you take that into consideration . Simpler to stay under 150 volts to ground.

[Ibon]

Thanks for some of these suggestions. Some clarifications. Yes we are in the tropics so no freeze risk and no closed system with heat exchanger required. This will be active solar heating with a circulation pump to circulate water from the collector to the tank.

Dolanbaker suggestion of a thermostat at the collector site that turns on the circulation pump as soon as heated up is great.

Since we already are producing 8KW constant AC with our hydro I do not need additional PV on the roof for electricity generation which would then need a DC to AC converter for adding little additional KW.

A circulation pump only uses 25w and I have the AC power for this so I don't need to design this as gravity fed passive solar either. Active solar uses electricity to run the circulation pump which we have.

Here are the specific design questions and doubts I still have

1) We now have good water pressure to the lodge as there is about 20m head from a 6000liter reservoir we built above the lodge. If we add a closed loop active solar to this water line how do we do this and not lose the pressure? Maybe this is a dumb question?

2) What pressure valves and check valves etc do I need when setting this up so that we avoid pressure building up anywhere in the system.

3) If we want to tie the solar heated water into the back up on demand gas heaters, would there be a controller that could feed the solar heated water direct to the hot water lines bypassing the on demand gas heaters when the water is hot and when the temperature drops automatically have the water directed through the on demand so that the gas turns on to bring the water up to required heating. I will have paying guests so I do need to make this system as automatic as possible trying to provide a hassle free hot water to the lodge without having to go run to the tanks and switch things around everytime a guest complains that the water is running cold on a cloudy afternoon. I hope that was understandable what I just wrote

Any further ideas appreciated

Jeffrey

[Shaved Monkey]

When travelling in Turkey 20 odd years ago they had black plastic drums on the roof above the showers usually with a hose coming through the roof and to a shower head with a tap in the line.
The flash ones had a toilet cistern valve in the buckets others were just filled every morning.
You had your warm shower in the afternoon.

[Surf]

If we want to tie the solar heated water into the back up on demand gas heaters, would there be a controller that could feed the solar heated water direct to the hot water lines bypassing the on demand gas heaters when the water is hot and when the temperature drops automatically have the water directed through the on demand so that the gas turns on to bring the water up to required heating.

a gas tank water heater would have most of what you need. It has a pressure relief valve, a thermostat and input and output pipe fittings. Simply connect the plastic tubing to the two water pipes. when the tubing is hot enough a temperature switch (not part of the tank) will turn on the pump and move water through the tank. The tank thermostat would be set to a temperature lower than what the solar water heater would achieve. That way the gas would not come on unless the solar is off or insufficient to provide the needed hot water. You should also add a switch to turn off the solar pump to prevent the water from getting too hot.

be sure you use food grade plastic and select tubing that won't melt in direct sunlight. the plastic tubing would simply be laid out on the roof. You probably won't need to put the tubing in box with a window.

You might want to look for a combination gas / electric water heater. I am not sure but there are probably are water heaters out there that have an electric heater as well as a gas heater in only one tank. That way you could use, solar, electricity, or gas depending on the conditions.

However I should point out that I have never done this and don't any direct experience. I would advise you to consult with someone that works in the solar hot water business, You might also want to look at http://www.homepower.com. Homepower.com is a magazine dedicated home renewable energy systems. some of the free information on their web site maybe useful.

[vtsnowedin]

Here are the specific design questions and doubts I still have

1) We now have good water pressure to the lodge as there is about 20m head from a 6000liter reservoir we built above the lodge. If we add a closed loop active solar to this water line how do we do this and not lose the pressure? Maybe this is a dumb question?

2) What pressure valves and check valves etc do I need when setting this up so that we avoid pressure building up anywhere in the system.

3) If we want to tie the solar heated water into the back up on demand gas heaters, would there be a controller that could feed the solar heated water direct to the hot water lines bypassing the on demand gas heaters when the water is hot and when the temperature drops automatically have the water directed through the on demand so that the gas turns on to bring the water up to required heating. I will have paying guests so I do need to make this system as automatic as possible trying to provide a hassle free hot water to the lodge without having to go run to the tanks and switch things around everytime a guest complains that the water is running cold on a cloudy afternoon. I hope that was understandable what I just wrote

Any further ideas appreciated

Jeffrey

!. The entire system can be at the pressure of the incoming cold water. Opening a hot water tap lets hot water flow out and as the cold water pushes into the tank to make up the volume. The cold settles to the bottom of the tank and starts out the feed pipe to the collector.
2. A single pressure /temp relief valve on top of the storage tank will safeguard the whole system as long as your circulation pump allows flow through it when not turning. If you pump doesn't allow flow or if your collector is a long way from the tank you could add another relief valve in a T coming up off the collector pipe at the top of the collector loops. No check valves are needed or advisable.
3. I would not fiddle with automatic controls but just feed your solar hot water into the cold side of your on demand heaters and let the on demand top off the heat as needed. When you don't have guest you could turn off the on demand heaters and just let the solar run through them.

[Pops]

Here's what I'd do on a shoestring

Build a "tank" out of scrap lumber, line it with heavy plastic sheeting (Visqueen)
Make it say 4'x4'x4' and insulate it, this is your storage/exchanger

Get some amount of copper tubing or PEX and arrange it inside your tank
Plumb it into the existing cold water line before the water heater.
Use some valves so you can bypass the tank if required.
Pressure test the line.

Build a collector out of your tubing and locate it below the tank
Be sure the lowest loop of the collector comes from the lowest level of the tank
and the highest section of the collector dumps into the highest level of the tank
Be sure the outlet of the collector (in the tank) is always covered with water
Evacuate air from your collector loop

Voila, thermosiphon!

I'd think you only need a pump if you can't locate the tank above the collector

If you find you do need a pump I'd try to rig up a small pv panel direct to a 12v pump, when the sun shines the water moves, no controls needed. I'd bet a good pump will cost more than a PV panel to drive it

Here's your link:
http://www.builditsolar.com/Projects/Wa ... ermosyphon

Here's a picture of what I'm thinking - because that's how I think lol

[vtsnowedin]

Pops your drawing will not work without a pump. It will vapor lock at the top where the pipe turns down into the tank. Bring the line from the collector into the tank horizontal about a foot down from the top and then it will thermosyphon without a pump. The light hot water needs to be able to exit the pipe and move up to the top of the tank. You cant get it to go down even an inch. Believe me I have tried. Also the cold feed to the collector should come right off the bottom of the tank not climb up through hot water to the top.

[Pops]

Thanks VT, I was afraid of that

I made a tank for the greenhouse out of a series of 55gal plastic drum and had to order some fittings to go through the sides of the tank, I assume you can make it work through sheeting

http://www.mcmaster.com/#tank-fittings/=sbh92x

[Ibon]

!. The entire system can be at the pressure of the incoming cold water. Opening a hot water tap lets hot water flow out and as the cold water pushes into the tank to make up the volume. The cold settles to the bottom of the tank and starts out the feed pipe to the collector.
2. A single pressure /temp relief valve on top of the storage tank will safeguard the whole system as long as your circulation pump allows flow through it when not turning. If you pump doesn't allow flow or if your collector is a long way from the tank you could add another relief valve in a T coming up off the collector pipe at the top of the collector loops. No check valves are needed or advisable.
3. I would not fiddle with automatic controls but just feed your solar hot water into the cold side of your on demand heaters and let the on demand top off the heat as needed. When you don't have guest you could turn off the on demand heaters and just let the solar run through them.

Thanks Vtsnowedin



Most of the pressure relief valves I am seeing on line are rated for 150psi and 210 degree F. Does this mean that the valve only opens at this psi and temp range when the water would actually start boiling? If so is this the right one for this system?

[vtsnowedin]

Thanks VT, I was afraid of that

I made a tank for the greenhouse out of a series of 55gal plastic drum and had to order some fittings to go through the sides of the tank, I assume you can make it work through sheeting

http://www.mcmaster.com/#tank-fittings/=sbh92x

Or just get the painted steel tank shown here and stand it upright. http://www.mcmaster.com/#hot-water-stor ... ks/=sbhgxt
The 80 gallon one for $560.05 would work like a charm.

[Ibon]

Here's your link:
http://www.builditsolar.com/Projects/Wa ... ermosyphon

Thanks for the link to this site. good info