Eco-friendly air conditioning?

[dan_aka_jack]

Hi folks,

Loving this forum... loads of handy tips.

It's hot here in London and it's due to get hotter this summer. Does anyone have any bright ideas about how to run air conditioning in the most energy-efficient way? Is the only option to put lots of (very expensive) PV cells on my roof and run "traditional" air conditioning? Or is there some clever way to use a heat exchanger somehow?

Thanks loads,
Jack

[shiney]

Oh I wish I just had some cool air coming in the windows. It's so hot today and muggy. No air, can't move!

No smart ideas from me I'm afraid.

[dan_aka_jack]

Yes, it is hot, isn't it! I've done some Google searches and yes, it looks like it is possible to use solar power to cool down your home / office. From my quick skim-reading, it looks like the best technology is "absorption refridgeration". If I understand it correctly, you should be able to "power" and absorption cooler from solar collectors! Here are some quick links:

http://en.wikipedia.org/wiki/Absorption_cooling

Quick overview of solar cooling

Another very quick overview of the solar cooling technologies available

Description of how solar absorption chillers work

Lots of very useful PDFs on solar cooling

Thanks,
Jack

[dan_aka_jack]

Hmm... bother... it looks like domestic solar absorption chillers aren't yet available... it seems that it's no easy feet to make these coolers less than about 100 tonnes! Ooops.

Back to the drawing board???

[shiney]

Nev's probably the best man to ask about all that sort of thing. I am sure'll he find the thread and may have some answers. 8)

[Shirley]

I'm looking forward to learning more about this - although to be honest it isn't particularly warm up here in Aberdeenshire... thunderstorms and rain have kept it cool... but hayfever is still there

[dan_aka_jack]

Hmmm... actually... this PDF describes (in far more technical detail than I can understand!) a 4.4kW solar cooling system. Here's a quote:

Experiments with the half-effect system have been performed under several operating conditions. The maximum cooling capacity was 4.36 kW, 44% of the original design. The maximum obtained COP was 0.25, 66% of the design value. The reduced COP mainly resulted from the design modifications required in relation to costs. However some of this reduction is caused by problems in fabrication. It should however be remarked that the operating conditions were quite different from the design conditions. This also has a significant impact on performance. For operating conditions similar to the design conditions the capacities and efficiencies would be much smaller than designed.

Hmm... I'm day-dreaming a system powered by one or two roof-mounted solar water heaters which supply both hot water for showers and refridgerated water for air conditioning and keeping food cool![/quote]

[Muddypause]

I don't really get the aricon thing - not in the UK, anyway. Open a window. Wear cool clothing. Use sunblinds. Buy a fan.

Air conditionaing does two things, really. It moves heat from one place to another, and it reduces the moisture content of the air. The former means that you will radiate heat more effectively, and the latter means that you will need to perspire less to achieve the same cooling effect on the body.

But how many days of the year do we really need aircon in this country? 5? 10? Maybe even 12? I'm not disputing the comfort of an air conditioned environment, but I have a hard time coming to terms with the expense of it - I was at a public debate on global warming last week, and someone said that aircon produces 4 times more greenouse gases than central heating (figures were not explained or supported). Certainly an aircon pump in a car adds a fairly large load on the engine, so you will consume more fuel.

Since the body has natural techniques for losing heat, why not spend the few days a year that are uncomfortably hot capitalising on these. One of the main ways we cool down is by perspiring, so first of all, stop thinking of sweat as something nasty, and encourage it. Do not use any anti-perspirants. Encourage its effectiveness by wearing light clothing that allows air to circulate around the surface of your skin. Get the air indoors moving - have doors and windows open to allow a through draught, or use a fan. Both will encourage your perspiration to evaporate, and a through draught will stop the humidity of the room rising. Take a quick, cool shower from time to time. Drink cold drinks - preferably lots of water, so you don't dehydrate. But also, apparently, tea stimulates a cooling effect on the body somehow, and a hot curry will also cause you to perspire more.

A great deal of heat is lost through the head, so, outside, if you wear a sun hat, make sure it is well ventilated, and light in colour to reflect the heat of direct sunlight; even, dip it in water, so that it absorbes heat as the water evaporates. Buy one of those trigger-spray bottles that produce a fine mist, fill it with water, and spray yourself with it (this is particularly lovely on hot muggy nights when you lie on the bed, unable to sleep, the bedclothes are on the floor and you are still sweltering - spray the mist into the air over yourself, and it will descend onto your skin as a delightful cooling blanket).

Most importantly, I reckon, is to savour the few really hot days we have - they'll soon be gone.

[dan_aka_jack]

I don't really get the aricon thing - not in the UK, anyway. Open a window. Wear cool clothing. Use sunblinds. Buy a fan.

Sure, I take your point.

And yes, I can survive without air conditioning. But my little home office here in muggy London gets really hot. I run a little film production / editing business and so my office is full of equipment which produces quite a lot of heat (and uses lots of energy... sorry... I am trying to find ways to decrease my carbon footprint as much as possible!) My business is getting to the point where clients come to visit and - as we all know - it's a bad idea to put your client in an uncomfortable environment! So I need air con! (I have a 14" fan running on full, pointing right into my face right now!)

But how many days of the year do we really need aircon in this country? 5? 10? Maybe even 12?

Hmm... I think that if I had carbon-neutral air-con then I would probably use it for about 2 months of the year. I like it cool!

And let's not forget refridgeration for food - that fridge in my kitchen uses up a sizable proportion of my electricity bill. Wouldn't it be cool (sorry, couldn't resist!) if you could power your fridge directly from the sun?

I've written to this guy to ask about solar-powered air conditioning. I'll report back when (if?) I get a reply.

Thanks,
Jack

[Martin]

sometimes it can be a case of shrugging your shoulders, admitting defeat - buying the most economic consumption air conditioning unit you can find, and then trying to offset with other technologies!
At the moment, I wouldn't recommend pv panels in most domestic situations - they're very pricey, at best offer a 25 year payback, and will undoubtedly plummet in price shortly, owing to new manufacturing techniques in the pipeline. Then comes wind - unless you're blessed with an enormous garden, I'd suggest that's a no-no too - roof mounted turbines are only a "badge" - they will not generate meaningful amounts of power - so of all the easily accessible technologies, solar hot water heating gives the "most bang per buck" - many times the kw/h output of pv panels, and FAR cheaper.
If you want to try "far side" - there are people importing Indian copies of old Lister diesels - ally that to a 3kw alternator, you can charge up a battery bank, run whatever you like, use the cooling water to heat the house, and as it's of such rudimentary design, run it on filtered chipfat!

[Muddypause]

My business is getting to the point where clients come to visit and - as we all know - it's a bad idea to put your client in an uncomfortable environment!

Ah, right! I can see that a spray bottle of water might not be the best idea in this circumstance.