Solar hot water, basic ideas

[jonescg]

Hi all,

I was thinking of trying to put a solar hot water system together by myself, using a few simple ingredients. Does anyone know if this idea is too crazy? My roof faces north and east:

For those in the know, here in the Southern Hemisphere the sun is in the northern sky So while having my collectors facing east is less than ideal, it is close to all the plumbing and out of the way of other potential photovoltaic setups like on the north facing roof.

I was thinking of a in-ceiling hot water tank which is pressurised by the main water supply. Lots of companies make these upright tanks with good insulation, or even better, an evacuated space. Anyway, in order to make the most of the thermosyphon process, I was thinking the collector could lie flat on the roof and the plumbing can come into the house like so:

Would I need a non-return valve on the collector pipes? Like a ball and check valve I guess?

Any ideas would be great.

Cheers,

Chris

PS I don't own the house, but I plan on making him an offer one day when I have some money.

 

[dnmun]

it looks like you have a tile roof. have you even asked the owner? i assume it never freezes there?

solar hot water is much more cost effective than solar photovoltaics. it is easy to conserve electricity, but you have to use tons of electricity if you use it for heating water.

you want the largest storage tank you can find, i used 120 gallon tanks on both systems i built. i have to use drain back systems, with heat exchangers and i used propylene glycol as the antifreeze in the primary loop with a 15gallon tank for the primary loop storage.

read up and you will find there is an optimum flow rate, so you only need a large enuff pump to handle that flow rate for the pressure head you are dealing with.

your tank will have to be on the basement concrete floor because the tank weighs 400 lbs itself and holds another 1100 lbs of water. add another 400 lbs for the primary coolant and heat exchanger.

there is a ton of literature and blogs out there, but focus on getting control of the house. money is cheap now because of the financial crisis so if you have job and can borrow money, go talk to the owner first and get control of the property before doing any work. you would be liable for damages when it fails, as it will if you are using a high pressure primary loop. plus the authorities always want their cut and be able to tell you how to do your job too.

 

[jonescg]

120 gallons (~500 litres) is a lot of water. It's just the missus and myself at this stage, so we don't need a huge supply. The house is brick with a tile roof, and there are lots of other houses with storage tanks on tile roofs. Like this one is about 100 m away:
http://www.nearmap.com/?ll=-31.910136,115.841924&z=21&t=k&nmd=20110420

There is a section of brick wall at the back where the shower recess is, and this could easily support the tank. It would need to be about 300 litres though. I would really prefer not to have a system that requires circulating water or glycol with a pump, and even if I did I don't have room for a tank at ground level. That's all garden space You can see my crop of broccoli at the upper right

Yep, we ever get frosts and the Perth summer is better known for never ending I would have an electric booster in there as well, but with a manual switch and timer (say 30 minutes maximum). We do also get nasty hail storms, however most PV systems survived unscathed, but older hot water systems were destroyed.

Still saving for a deposit. Australia's financial system is tightly regulated - that's why we aren't in a whole pile of poo right now. You can't borrow for a house unless you have a minimum of 15% deposit. If only I could stop pouring money into my electric motorbike...

 

[spinningmagnets]

All the plusses and minuses of every possible type of system is listed at http://www.builditsolar.com/. There is a months worth of reading there.

Consider if a solar pre-heater might work for you, they can be mounted on the ground, as long as you insulate the outlet that goes to the inlet of the stock home water heater:
http://endless-sphere.com/forums/viewtopic.php?f=41&t=27760