Hi all. Recently bought a townhouse in Mora and thinking that simple gravity fed Solar Water Heating from a rooftop unit might be practical. Has anyone any experience or recommendations in this respect?
P.S. Most impressed with the forum setup and content.
Cheers, Ray.

I have solar hot water (a self built system) and have installed a few systems. All work extremely well, the best solar investment you can make!

One customer of mine has a system he also uses to heat his house - I only installed it this spring so as yet we don't know the results.

I'm currently working on a project to install a hybrid solar/heat pump heating system for my house, again a home made system hopefully I'll have it installed soon and will know how well it works this winter. I had the heat pump working last winter and saved in the order of 1500 euros in heating oil by running it.

I must admit to not being a fan of the gravity fed systems as I've seen problems such as boiling/calcium build up etc. with them. The system I prefer is a closed solar circuit with circulating pump and an indirect heated tank.

Mine, for example, is a single panel (about 2.4m x 1.2m) and a 160 litre water tank. We have hot water from this pretty much from late February to November. Outside of this I use a combination of a heat pump or immersion heater to heat the water, the former being the most efficient. The pump and control runs from solar so effectively costs nothing to run.

Hi Nigel, could you provide a plan for your 160l system? 

Wow they were a good find Nigel, never seen any of them in a skip
And thanks for the link, bookmarked them, useful site for us with an eye for cutting costs.

Thanks all for input. Gravity system still looks simplest (and probably cheapest) to me..acknowledged that I'm only going on reading stuff and that there might be some longer term issues. Seems difficult to find a spanish supplier quoting prices, but I have found some in Malaga via ebay uk site if anyone is interested.
Cheers, Ray.

I see lots of this type of system around - it seems an obvious solution but does have limits, some of which are below:

1. The pipe radiates heat and as it is not enclosed in a panel the heat escapes so reducing the efficiency. Also wind will cool the pipe if not enclosed in some form of panel.
2. The quantity of water is limited to the amount that will fit in the pipe.
3. The surface area of the pipe in contact with the water is small. The bigger the pipe the less contact.
4. The surface area of the pipe exposed to the sun is small as large parts of the pipe are in the shade.
5. Plastic pipe is not a good conductor of heat.
6. At night the heat will be lost due to lack of insulation.

Hi Nigel,
I hear what you say but :-
1.  I'm thinking that if a 30m green hose pipe gives me about 10 litres of water hot enough for washing up (and too hot for showering) then 100m of black 32mm pipe would give a lot more (i.e about 300 litres).  More than enough for general houshold use at any one time as once you've done the washing up or showered (or whatever) the residue in the pipe would carry on heating up.  It wouldn't be difficult to locate the pipe in the lee of the wind ?
2.  See above.
3.  Don't get that ?
4.  Ratio mentioned in 1. still applies.
5.  Ratio mentioned in 1. still applies.
6.  How much washing up etc. do you do at night ?
I'm not trying to deliberately contradict you and your laws of physics are correct but it seems to me that it would be very cheap and simple to construct.  I'd give it a try if I had nowt else to do and a 15€ bottle of gas lasts about three months on the water heater.
Could an insulated storage tank not be included in the circuit so that there was a resevoir of pre-heated water to feed the boiler in the morning ?

Nigel what is your opinion on 3/400 ft. of 32mm black pipe coiled flat on 8x4 ply base painted black enclosed on top with uv grade polycarbonate. placed on a frame on the ground facing the sun. The hot water from the coil thermosyphons up through insulated pipe to a heavly insulated 1000l tank on the roof with either a second coil or just direct feed from the tank back to the coil gaining heat during each cycle. 
A DC pump with panel could be used for circulation if the thermosyphon is not enough.