Solar thermal, brand new project and want it right! Not just how the Italians want to do it.

Hi all,

Had a bit of a trawl around the forum but not quite fund the answers I need so hope you don't mind me starting a new thread.

My wife and I have bought an old farm (yup, that old cliche) in Tuscany, Italy and are working towards a more self-sufficient and responsible lifestyle, our next project is to get rid of all of the hideous electric water heaters in the house and heat the water with a combination of solar thermal for warm months and wood stove with back boiler in the cold months.

We've had our first quote for the solar panels and 300 litre tank (inc. install) which is comprised of a new type of flat panel, looks nice but someone has since told me that these aren't as effective as the tube type of panel, so i'm confused already and thought i'd come to my 'go to' forum and 'go to' people to get some info and try and get this job done properly from the start as we have a finite pot of money to do a few projects before the money dries up, we're into doing things properly and once however as whatever we invest in now needs to last as long as possible.

So any advice on both solar thermal and wood stoves (not quite the right part of the forum I know) would be HUGELY appreciated.

Thanks in advance!

Stuart Smith : Welcome to Permies.com, our sister site Richsoil.com and a big Welcome to the Solar, and potentially the Rocket, Wood stoves,
and the Cob Forum Threads !

A little paperwork to make your searches and threads more useful to you ! Links below :

https://permies.com/t/34193/tnk/permies-works-links-threads
https://permies.com/t/43625/introductions/Universal


With Soooo- many Fellow Members world wide you should be able to come here 24 / 7 365 and talk with someone who wants to talk about what
you want to talk about !

Short version The air evacuated tubes allow light to enter and be absorbed by the black painted back surface turning light energy into heat energy
which is 'trapped'' by the vacuum, as water* trickles down the back plate it absorbs this heat energy.

This arrangement is much more efficient ,more costly and a lot more fiddle-y !

Here is a D.I.Y. link that will quickly bring you up to speed on terms and their meanings , Link Below !


http://www.builditsolar.com


Hope you find this timely and helpful for the crafts! Big Al

* Actually a Glycol and Water solution for antifreeze !

Thanks for the warm welcome Big Al!

I'll take a look at these links now.

Stuart Smith wrote:someone has since told me that these aren't as effective as the tube type of panel

So? It's not like sunlight is metered...

I'd be concerned more with the expected lifespan of the materials than with collection efficiency.

I'd be more interested in panels that can be used in freezing weather...

Stuart : It took me a little time to remember where I saw this ! These units actually work excellent when the sun is out

These are individual Evacuated tubes for solar cooking Link below :


https://permies.com/t/28528/solar/GoSun-solar-borosilicate-stove

More information at GoSun.com For the crafts! Big AL

OK, too now add to this, the architect wants us to site the panels behind the house, they'll be south facing but they will lose the sun by 2pm after 5hours sunlight, is that enough?

Stuart : Joseph Lofthouse has a good point, unless you have very deep pockets you should be looking at power generated per unit costs !

People like the idea of Solar collection panels, but don't like to look at them ! I think that your Architect is thinking in terms of presentation .

This will affect your ability to sell the house years from now, also he does not want the reputation as the Architect who puts up those ugly

shinny things in the front of peoples houses.


The Architect's location is poor at best ! Especially if you are going to be commuting and coming home in the evening, this is when you will

want to Bath / shower , cook, clean, do laundry, wash-up and so the unit will need to be bigger to Collect/Store more heat or use a back up

source MORE -to make sure you don't run out of hot water !

Siting your solar collector to achieve the most energy to match your (assumed ) Needs is only common sense ! For The Crafts ! Big AL

Stuart,

The evacuated panels are more efficient but that doesn't matter in Tuscany as you don't have long snowy winters which is really the only time when that "efficiency" matters. The flat plastic panels work great anywhere it is warm. In addition, the cost difference is staggering! In addition, the weight and thus engineering is greater with the evacuated panels again making the simple flat panels much cheaper.

As for sighting, the long and more sun, the more hot water but again, how much hot water do you need? Nothing more expensive than building in capacity you don't use!

Thanks for your replies so far guys, really do appreciate the help on the this forum.

So, here's the full story on location for these panels, we have a 300 year old stone and stucco farm house, the roof is a standard (fornhere) pitched roof, the front pitch faces west, the rear pitch eastwards, our own architect submitted plans to fit them to the west side of the roof, these plans were then approved by the local council but not by the man in charge, the superintendent from Florence, his word is final, firstly he insisted that the panels were red to match the roof tiles, our architect told him that was not possible so he insisted to come and visit which he did last week, this is all made more difficult because we live in a conservation zone so they try hard to preserve the look of the area, anyway, it was when he visited that he suggests the panels are fitted to the shed roof which runs along the rear east facing wall, this roof wall take four square meters of solar panel.

Michael Bushman wrote:Stuart,

The evacuated panels are more efficient but that doesn't matter in Tuscany as you don't have long snowy winters which is really the only time when that "efficiency" matters. The flat plastic panels work great anywhere it is warm. In addition, the cost difference is staggering! In addition, the weight and thus engineering is greater with the evacuated panels again making the simple flat panels much cheaper.

As for sighting, the long and more sun, the more hot water but again, how much hot water do you need? Nothing more expensive than building in capacity you don't use!

Thanks Michael,

I like this reasoning!

It sounds like flat plastic panels are thew way forward for us then, I can at least rule the more expensive option out which is a bonus.

I just need to work out if 4 or five hours of sunshine onto 2 1mx2m panels will be enough to heat a 300 ltr tank and for it to stay warm enough long enough, as Big Al says the evening is when we'll mostly need this water and first thing in the morning too.

P.S. sorry for the duplicated replies above, I was using my phone which said it couldn't post because of a javascript error when it clearly was posting fine!

Insulating the tank is cheaper than adding more panels. As for how much hot water you will get from that much sun is something someone smarter than me will have to comment on. I would think however that a factor in that is whether or not the system uses passive or powered movement of the water.

Another thought is that most plastic tanks are black, perhaps having one black in the sun for evening usage and another that is insulated for morning use, perhaps tying the insulated one to your wood fired hot water heater setup? More complication but again, all depends on how your costs and usage play out.

Hi Stuart,

In the process of doing a DIY installation of a 200L evacuated tube (24) type of solar hot water heater at our place. Have seen the flat ones on the market too, but didn’t think they were the right choice for us in snow or typhoon conditions.

With the electric water heaters in your house already, you may have a chance to also circulate solar heated water through them in winter too.

Our hot water outlet from the tank will go through a thermostat valve, then through a gas water heater, so on very cloudy days the gas heater can be turned back on (automatically or manually) and we can still have hot water in the house.

Here are some pics of them around Japan.
MMC Solar in Japan

And a few links to other info.

Solar hot water heating

Evacuated tube or flat plates

https://en.wikipedia.org/wiki/Solar_water_heating

And a couple of pics of our unit and the tubes.