Solar/wind?

[Bruce]

No, but you got two "Nice try"s in one posting, so you should be very grateful.

[Bruce]

Nice try. ;-)

[Andy Hall]

That one's on Shift-F4

[dennis]

She did. It doesn't matter as the 10C rise costs the same for the boiler if its from

60-70c. It doesn't take the same time for solar, it gets longer and longer.. most days you will be either be lucky to get *hot* water or have spent far too much on big panels. With gas prices as they are, solar water heating doesn't make sense, it certainly didn't make sense last year. Even if you save cash there is still the issue of using producing more carbon than you save. Some of us consider the environment and use the least polluting methods even if it costs more than solar.

I certainly wouldn't use wind power, the environmental damage from wind turbines is far too high whatever they save me in cash!

[The Natural Philosopher]

With dynamo dave, nice try == 'I think you got me there, right on target'

[R D S]

I didn't say 'each', I said 'all'.

[Fran]

Solar panels to heat water make a lot of very real economic sense - but it's a long term investment. I can't recall the exact figures now, but I think the solar water heating system I had in Cardiff cost something in the region of £3,000 to install around 10 years ago. By no stretch of the imagination is that 'cheap'; however it will have paid for itself within a few decades, even in the UK. Most people don't want to wait that long to see a return on their investment (and who shall blame them), so they don't see solar water heating as a viable choice. I have a large family, and we use a lot of hot water. For us, it's viable; for a single person or a couple with maybe one or two children it might not be. Then again, they wouldn't need such a large system as we did, so who knows. As I've said elsewhere, if I had the capital to have a similar installation in the house I live in now, I wouldn't hesitate to say yes. If I had the skills to install it myself it would have been done as soon as we moved here.

[Fran]

That depends on how much hot water you want though, doesn't it. I have a large family and we spend considerably more than £60 a year heating water for laundry and personal hygiene. Our expenses will reduce as the children leave home, but that's not going to happen for a few years yet.

[Owain]

Was that "paste" in WordPerfect 4.2?

Owain

[John Rumm]

I expect if you include the interest lost you could have had form leaving the money invested, or paying it off your mortgage for example, then it takes on a different complexion. If you have to borrow the money to install it then you are losing out from all directions.

If you could DIY at a capital cost of a few hundred, then it starts to look more attractive. (assuming you have a compatible hot water system in the first place).

[dennis]

£60 will give you about 3 ton of water at 70C using electricity or about 10 ton with gas. That will run a shower for about 350 hours.

Washing machines tend to use little hot water even if it has hot fill.

[Rod]

Did anyone else notice the story that solar wind might have blown life from Venus to Earth?

(What a difference a slash makes.)

[Andrew Gabriel]

That's probably down to the insulation of the fridge. Peltier devices can do more, although not having much heat pump capacity compared to a compressor fridge, it will take them quite a long time to cool down bottles. Heat pump capacity tends to be just under than their power consumption, but a lot of the cheaper circuits just turn them on and off with no proportional control, in which case they leak significant heat back in. One of mine will carry on powering the fan for a couple of minutes after you disconnect the supply, which it's doing by using the temperature differential across it to generate electricity as a thermocouple, but in doing so is leaking heat into the fridge even faster than it would just by conduction. Some don't have any temperature control and just run the device continuously.

In repairing these fridges, I would say the main issue is they aren't designed for continuous operation, but just occasional use, e.g. a couple of weeks a year, in which case you might get 10 years out of them. With continuous use, they seem to last around 6 months. There are 3 common failures: Peltier device corrodes because cold side is not well enough protected against condensation. You can buy sealed ones which aren't that much more expensive, but these cheaply built fridges don't use those. Fan motor dies (brushes give up). I've doctored a few fridges to take a standard PC fan, which lasts much longer.

12V power connector burns out -- they aren't of a suitable quality to take 5A and keep contact resistance low enough long term not to overheat. A few other one-offs such as a signal transistor shorting on the thermostat control board so the unit ran continuously, and I had one quite new peltier device which burned out on the last junction - I managed to solder a thin wire across that one so all the others would continue working.

[Andy Hall]

How long of a long term investment?

Is there a full return before replacement is required?

Will the system remain in a good state of repair and function without additional costs for these several decades?

Exactly. Who knows? Do you have figures?

It's easy to spend capital if you have it. Anybody can do that because it seems like a good idea at the time and especially if the salesman thinks so too.

[Andy Hall]

I tend to find that's the case after a few beers.....

[Bruce]

[Neil]

I also have a small compressor fridge/freezer, and can echo your findings. It is a Waeco CF18 and my measurements showed that:

From 20C ambient temp, it got down to 5C in less than 5 minutes.

From that point, to maintain 5C, the compressor was operating for an average of 1.5 minutes ON, followed by an average of 15 minutes OFF. Which is very close to(slightly better than) your own 10% running time figure!

The current draw while running was measured at approx 4 amps from a small 12v lead acid battery.

I make that 48 watts for 2.25 hours per 24, or 108 watt hours per day. Compared with 1440 watt hours per day for Peltier, or 2304 watt hours per day for an absorption fridge on 12v. Unless my maths are wildly out!

So I reckon that's doable with a reasonable PV panel and a small lead/acid battery to carry it through the night and overcast days.

Obviously if I turn up the thermostat until the box becomes a freezer at -20C(which it will do) then the watt hours goes up. But I didn't carry out a test for that use, as it would not be the main function of the CF18 in a camping role. As a freezer it's great for shopping for frozen food and not having to rush home before the ice cream melts :o(

HTH

Neil

(Reply via NG please)

[Andy Dingley]

How do you know? How are you measuring this? With gas in particular, it's hard to split DHW costs from space heating.

[The Natural Philosopher]

Well, in the UK you can get about 200 quid return annually on 4 sq meters of panel, used absolutely optimally. Mostly in the summer.

That was the calc I did based on the manufacturers own figures for average insolation.

Its up to you as to whether thats worth 4 grand of installation. It represents 5% ROI. you can get more han that leaving the money in the bank..

[Fran]

My central heating and water are heated by different systems.