/diy/ - Do It Yourself

>>1603002
>>1602495
>>1602496
>cans

No. Do not use anything you've ever seen online that involves cans. they are ultra inefficient. Just use a single sheet of black-painted roofing metal as the solar collector in a box. It is very simple and all you need is to adjust a vent to get the flow you want.

For water heating, you want an heat exchanger for areas where outside temps can cause water to freeze and burst lines. For everywhere else, a batch water heater should be all you need. The latter is basically a big black-painted tank of water in your pressurized system that is inside an insulated box with or without reflective panels. The panels can just be painted flat white, no need for mirrors or foil. For places where you need a heat exchanger, you can use thermosiphon flow to help move heat and liquid through the system. The liquid will be water + antifreeze. The solar catching & heat exchanging piping should be copper for best thermal conductivity, but that isn't needed as any metal piping will work. Some people even use large diameter PEX coils in the batch pool in their basement for whole house heating.

The basic thing you need for heat exchanging is large diameter pipes with as few directional changes as possible. The perfect shape would be a perfect circular ring made of pipe, but that isn't going to happen in most places. So, try to keep as few elbows and slow coils in the design as possible. A lot of people make the mistake of putting too many loops in heat exchanger coils and that slows down the flow drastically for thermosiphon. If you use a forced system that has a pump then it doesn't matter since the electric pump does all the work, but thermosiphon means the sun's heat is doing the work. So, few directional changes for the flow and large diameter piping. The same thing applies to air flow.

>>1367505
Here's another old one of mine. Circa 2009. The solar box needs to be lower than the water tank so the flow works correctly.

>>731261
Something similar to this.

>>557653
>>557654
A closed loop for the heating side with anti-freeze will prevent problems for areas that have freezing temps.

>>441709
Yes.

It's easy too. If you live in an area where water won't freeze, in the winter, then make a solar batch water heater. If you live in an area where it will freeze then you'll need to insulate it well or use an antifreeze thermosiphon circuit like in this image.

http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

>>324227
>is this how they work?

Fundamentally, yes.

>i havent seen syphons with mirrors or polished metal

I've made a couple, as practical conceptualizing.

The best way to design them is with a use in mind. If you will be adding reflector panels, the air or liquid passing through the collector will get very hot dependent on its speed and volume. This will allow a faster flow rate. Since the flow rate can be faster, you can increase the diameter of the channels or piping and make them straight vertically instead of zig-zag.

However, the amount of heat you put into the system needs to be taken out just as quickly on the other end for whatever use you are using it for. Otherwise, you are essentially wasting all that extra reflector space.

>>324242
That depends on too many factors to accurately determine; unless you have those variables to calculate. If there's no flow, it is well insulated, and the collector size is large, then it can get so hot that it will ignite wood. Conversely if the flow is very fast and volume high it will be barely warm to the touch.

Essentially, you will need a square area of full sun equal to about 3 feet x 7 feet to make enough warm water for a good shower or bath. Adding reflector panels can increase the temperature, but might not increase the flow rate very much.

I think I've reworded the same information enough to give you an idea. Here's some quick tips,

1: larger diameter piping = easier flow starting faster flow
2: fewer bends = easier flow starting faster flow
3: reflector panels = hotter, which can allow for a faster flow design
4: zig-zag is good for slow heating applications
5: straight pipe is good for fast heating applications
6: good flow will only occur when you have a good heat exchanger to remove the heat

>>310804
I plan on making a passive solar water heater some time soon. For my collector I'm going to use an old glass patio door, old sheet of roofing metal painted black, and copper piping painted black inside it. Since my area freezes down to -15F in the winter, mine will have a closed loop for the heating side and it will have antifreeze in it.

There's a chance I may hook a small VAWT up to it to pump it with wind power if the flow is too low otherwise.

One big tip. The larger diameter of your piping and the fewer the elbows and turns the faster and better it will flow for heating if you are using a passive non-pumped design.

Here is one of my designs. I recommend using 2nd hand glass sliding patio doors for the glazing. It keeps them out of landfills, is normally free, and their double glazing helps keep the heat in when wind hits it. Minor fogging of the glass due to the seal being compromised isn't that big of a deal (which is why people toss these for new ones, fyi).

For the collector you can use large diameter copper pipe. For the rest you can use large diameter PEX tubing. The more bends and elbows there are the less water flow, but the larger the diameter the better the water flow. So, it is all about finding the right diameter piping for water flow and cost. This is of course a passive system without any pump, hence the large diameter piping. An active system with a pump can use smaller diameter piping and the collector and storage tank positions do not matter.

Passive solar for hot water in areas where freezing is a problem.

Solar thread.

Post all things DIY solar. Bonus points for being passive solar.

Here's a passive solar thermosiphon water heater I designed, some years ago, for areas where water freezes in the winter.