Its Payback time

[jondy]

A few years ago we got one of those flyers through the door ' FREE ENERGY' solar hot water, free estimates etc. An old couple up the road brought one and he told me of its many virtues, designed by mercedes benz, he said. Must be good. I had the opportunity of taking a quick look, it was the latest (then) glass tube panel and had an impressive digital read out gaugue. About a year ago the Lady let on that it was very expensive, bit unhappy about her other halfs purchase. I think these systems are said to provide up to half of your water heating costs?
What are your water heating costs? If you are going to pay around £2,000 (and up) how many years is pay back time? The point is all products have a life, will the life of the product expire before pay back time, will you expire before pay back time? I know the glass tube panels are probably the most efficient and prices for these are coming down. Example, ebay 20 vac tubes 58mm x 1.8m price £325, add in the other bits for the system and you still have an unacceptable payback time. I know about the radiator versions, they work very well in the summer. Built from used items they make sense, but rust out etc. I have started a simple diy system. The idea is to make a 3 season system that does not involve antifreeze, drain down in the winter. The most important factors are keep it simple, keep it cheap. The first part was a freebie. A used copper cylinder. It's better than aluminium as you can solder copper tubes to. Cut off the top and bottom of the cylinder, cut along the the length of the cylinder to form a flat sheet. 10mm copper tube is easily formed into a serpentine shape avoiding soldering. The box, I have some oak decking boards, f.glass insulating, I have that. For the glass I thought that twin wall conservatory plastic roof might substitute for glass, not so good at transmitting light but this might be offset by the insulating value. The absorber plate can be rivetted to another one if you want to make a bigger panel. No harm in adding panels as scrap copper cylinders become available. This is not intended to go on the main roof but on a lower flat roof. Ideas are evolving, solar pump, perhaps. Any ideas for something simple? A payback time of 6 months would be nice.

John

[Muddypause]

Can you do a webpage with a few pictures of this, so that we can see how it all fits together? Be very interested in what results you get.

[jondy]

Not clued up with computers Muddypause (could'nt get a picture on here despite lots of trying) I found websites that advised on Al clip fins on copper pipes and copper pipes on Al absorber plates with wire twists to hold the piping, for example. Joining the copper tube to a copper plate would be a better thing to start with easy soldering giving good connection/conductivity. Cheapest way to copper plate was the scrap hot water tank. 'Solartwin', is well plugged (google) does not rely on antifreeze, uses black non metal piping,(used in milk producing?) no freeezing problems. I think this piping could be sourced. I want something very simple, it could at first stage provide warm water directly to the washing machine and (pre warmed) for kettle or kitchen sink use. but looking for some ideas. Making the panel should be an easy first step. I find with projects that things evolve. The point here is look at the payback time before spending your money.

John

[Martin]

I'm all for experimentation, it's how we progress! - but please, do be very careful with "preheating" water - if you store it at too low a temperature, there is the very real danger of Legionella!
Plastic pipes for solar? - sucks teeth, gazes heavenwards! - well, we wouldn't use them! A real solar hot water system gets bally hot, you do not want to be faffing about with placcy!
As to antifreeze, I don't like the stuff, but in a well designed system, you're probably talking well under a litre of the stuff, replaced every five years (FAR less than you'd use in your car)

[Martin]

ps, if you want a really simple and cheap system, using placcy - collect loads of clear plastic pop bottles, and a length of black hose - make a hose sized hole in the bottom of each bottle, and thread the hose up through the centres of all the bottles - then trickle water through - on a sunny day, it gets surprisingly hot! - you could try having them on the ground, and run a loop of "bottled hose" to an insulated water butt, at least 6-8' above the level of the bottles, that way it should thermosyphon! (one end of the hose attached to the tank near the top, the other at the bottom!)

[jondy]

Hi Martin, as far as plastic pipes go, I mention this as 'Solartwin' appear to use these in their system. It's an interesting and well proven concept. I have'nt found plastic pipes myself, The low cost way is copper tubing. You would know about Solartwin? I guess they can withstand the temperature?
As far as pre heating water, the idea of solar water heating systems, ie. warm solar water in a seperate tank, for example, feeds into the hot water cylinder. Lots of other concepts. You would not need to drink the water, I mention preheating for kettles as an idea, it would need to be looked at. Thus any ideas.
How much is a Solar water heating system? How much of the hot water costs can a solar system save? What is the approximate cost of a family's hot water costs? How many years to pay back time? Sucking of teeth, gazing heavenwards! Be interested to hear your views.

John

[jondy]

Just looked on the Solartwin website, there 'placcy' pipes, (actually silicone rubber), are OK from -60 to plus 200c! A good concept that is well proven, lots of info. But very expensive.

John

[Muddypause]

Plastic pipe is a standard for central heating systems; would solar heating get the water any hotter? With a boiler, you should have 1m of copper tube before you use the plastic (I don't know the rational for this - it may just be about not having plastic pipe near the source of flame).

Jondy, it depends how much copper tubing you are talking about, but I call it feckin expensive stuff - 15mm tube is a pound a meter; 22mm is two pounds a meter, and a plumbing system usually uses more than you think.

BTW - my guide to including pictures in your posts.

Edit to add: I've just looked it up, and I see plastic pipe suitable for central heating is pretty much the same price as copper.

[Martin]

All I'm prepared to say on plastic pipes in solar is what I said above - we would never use them, we don't consider they are up to the job! The manifold on a vacuum tube solar system can happily run at 120c - that's seriously hot!
It's a classic "how long is a piece of string" question, but I'll do my best! - you can indeed obtain complete kits of parts to "do it yourself" for around 1200 quid - that would comprise probably a 20 tube panel,a twin coil 175 litre heat store (one coil for your existing boiler, one for solar), and provision for an immersion heater, control system, sensors, pump, and pressurised loop for solar! I would also certainly not pretend that it is impossible for a very keen handyman to manage to fit it, and several people do accomplish it!
To have a simple system fitted, we'd probably charge around 2.5-3k all-in.

So,- we reckon that a good system should give the average family all the domestic hot water for the summer months, Mid March - October in the south, and make a small contribution the rest of the year! If you have the misfortune to only have an immersion heater as a substitute, payback will be relatively swift, if you're on mains gas, it'll take longer, as gas is by far the cheapest fuel - oil is somewhere in the middle!
Certainly, the systems we do are designed to last well over twenty years - they are remarkably simple and robust - there isn't a lot to go wrong!
So, I wouldn't pretend you'll get payback within a couple of years, but especially if you went the diy route, it shouldn't be inordinate!

[Martin]

while I'm at it, I may as well don my salesman's hat!
"Payback" is important - both financially, and in terms of the damage we do to the earth by using any technology, but we do need to look at it in relation to other things we spend our money on as well!
There are many people who think nothing of trashing their old kitchen every 3 or 4 years, and spending several thousand quid on having "this year's look", or flying off to Brazil three times a year to do "eco charity work", -or change their cars every couple of years for a new model - all of these activities are incredibly wasteful of both money and energy - in relation to those sorts of expenditure, solar hot water looks incredibly attractive - AND if you get it done for around 3k, you've added 5k to the value of your property!
Add to that the fact that energy prices ain't ever coming back down again, and it's a start to divorcing yourself from the centralised state controlled power sources.............

[Martin]

ps, when looking at solar systems, have a jolly good squint at how they connect the solar panels to your plumbing!
A "cheap and nasty" system will circulate all your hot water through the panel, giving lots of lovely problems with limescale, or faffing about with water softeners! A proper system usually entails a tank change too - the normal copper cylinder with one coil is replaced with a thermal store(super-insulated tank) with 2 or more coils, so there is a dedicated pressurised loop for the solar system, one for the boiler etc.

[jondy]

Muddypause, thinking 10mm pipe. Smaller diameter pipe, hotter water, perhaps. Solartwin's pipe is 6mm so I guess hotter. Perhaps its not black in colour, it could be under the solar collector plate. Could be ok to copy, if you found the pipe.

Martin, Simple question, based on your figures, how many years to get back the £3,000 outlay....Before, you start saving money? Rough guess?
at todays prices. (predicted fall next year) How long is the system gauranteed for?

John[/u]

[Martin]

if you heat your water electrically, it could be as short as five years, but for most properties, it'll probably be nearer ten! It really does depend on your existing plumbing, water useage etc.!
If you want to do sums, one of our 20 tube panels will give 14kw/h of heat on a summer's day (1-2kw/h in the depths of winter).
We give a year's full guarantee, during which time any faults should surface and be remedied - we try to give the best possible value, and I think the following sums it up -

"we offer a 12month guarantee, although, with no moving parts the panels are extremely long-lived, probably in excess of 25years. In fact, the manufacturers offer a much longer guarantee, but in the UK we do not offer this extended period due to the legal requirements - if we were to offer a 25year guarantee, we would need to take out an 'indemnity' policy on the product. The insurance company bases its risk on an assumption that if it priced the policy on the basis of replacing the unit once within 25years, then they will ensure profitability regardless of claims - thus they would cost this in at probably £300 or more per item sold. The cost is out of line with our policy of keeping prices as low as possible, and We decided that most customers probably would not want to pay this additional fee!"
-from our suppliers

[Martin]

'ang on!!!!!!! - far be it from me to carp, or point things out, but I just visited the website of a company who's name has been much-bandied about in this thread - the choice is yours - one of their diy kits -2.5k, and that is just a "hack it into the existing system" kit - no tank or proper controller included!!!!!!
-and I've had a quick rootle through the figures - and this is from an actual typical installation of our system - over a year, the pump costs around 3 quid in electricity to run - 33kw/h!

[jondy]

Regarding a payback time of 10 years this ,assumes, a very generous saving of £300 per year on your hot water costs! Cloudy days in Summer too.

So for 10 years you are denied the interest on your £3 grand sitting in a building society at 4 or 5 %, compounded.

Add to this the very real possibility of failed pumps or other parts in that 10 year period. Add to this an inspection or two, antifreeze check etc. ? Whilst trying to recover your initial investment in low cost energy.

Year 11 perhaps, you might look forward to some cheap energy gained from a potentially more unreliable system.

From the 'Solartwin' website you will see the results of eight different systems tested in Milton Keynes. The carbon footprint, for example shows that using electrical energy to power the system brings about negative results shown for glass tube systems. As for the carbon footprint, manufacture of a system should be added into this. Ask yourself about the manufacture of the products, off shore/china? for example. China powers its industry with coal fired power stations.

Adding value to your home?, sorry. From much media advice on how to add value to your home, I have never seen a mention for solar water heating. Top of the add value lists are improve your kitchen/bathroom and add a conservatory, for example. All add to the so called, wow factor. Adding a conservatory can also add a great deal to home heating in the winter sunshine.

Think you might have got your lines crossed with legionaires disease as you will be boiling the water to make tea, but worthwhile looking into the downside of all things I suppose. Using rubber tube in the plastic bottles, piped to a black water butt, a potential freebie, good thinking Martin. 'Solartwin' Great concept, make a good diy? Nonsense prices.

John