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tony.
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« Reply #15 on: July 05, 2009, 08:53:17 PM » |
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daftlad,
i would use a 3 pin 78 series voltage regulator. they come in different voltage ratings ie 5 volt output is a 7805, 9 volt output is 7809 try maplin,farnell,rs for stockists.
have a look at the data sheets for these units.
regards
tony
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daftlad
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« Reply #16 on: July 05, 2009, 09:08:27 PM » |
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Yup
cheers for that.
How do they react when they have only 9 volts supply voltage?
I think for less than a quid I may as well fit one.
cheers everyone
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tony.
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« Reply #17 on: July 05, 2009, 09:44:13 PM » |
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i imagine if you add a couple of 12volt electrolyic capacitors across the input that would help.
tony
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Ivan
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« Reply #18 on: July 05, 2009, 10:40:51 PM » |
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I've got a 12v fan running directly from a PV. Works fine. I guess you don't want to overrate the PV beyond the fan ie 5W PV drives a 5W fan...NOT 10W PV driving 5W fan. I found that the standard computer fans are hopeless if you have any kind of pressure drop across your air-heater panel. I ended up using a 10W tangental fan designed for souped-up computers - £5 from ebay. As someone else suggested, a bilge pump is suitable for larger flow volumes, but I find that my 10W fan is fine for up to 1.5kW of solar heat.
Ivan
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daftlad
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« Reply #19 on: July 05, 2009, 11:08:56 PM » |
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I found that the standard computer fans are hopeless if you have any kind of pressure drop across your air-heater panel.
I don't understand. You lot keep banging on about pressure? Why would there be a pressure difference? Basically I am building one of those "solarventi" things that Billi linked to, why would I need have air pressure, I would think I just need to move air down a 4 inch pipe? I think I need an explanation of air flow characteristics? Learning lots laters |
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Ivan
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« Reply #20 on: July 06, 2009, 01:19:48 AM » |
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For air to move, you need to have a pressure difference. Pressure differences and movement of air are inseparably linked. Everything has a resistance to flow. If you have a 100" pipe it will have less flow resistance than a 4" pipe. The faster you push air through, the higher the pressure-drop will be. In the case of computer fans, they can shift a fair bit of air, if there is a negligible resistance. As soon as the resistance increases, even just a little bit, it reduces flow rate to almost nothing. Now your panel might have sufficiently low pressure-drop to avoid any problems. But in my case (50cm or less of 50mm diameter flow and return pipe feeding air through 20 parallel 15mm diameter 1.5m long pipes, and returning via concentric 47mm tube) the resistance was too high. From the above, you should be able to estimate relative resistance of your panel.
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knighty
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« Reply #21 on: July 06, 2009, 02:08:02 AM » |
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having spent a fortune on PC fans... I can say you need a different kind... if you get one made for a cpu heatsink it should work fine....
some of those ultra quiet low poer case fans are pretty naff.....
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billi
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« Reply #22 on: July 06, 2009, 11:51:11 AM » |
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I donot know exactly why the solar air collector companies over spec their PV panel compared to the fan ( in this case its only overspec for the small panel they have , but thats because i guess the fan is integrated in the panel and the other models are external and radial fans ..... nice one that they write in there brochure the type of fan so for the "TWINSOLAR 2.0" http://www.grammer-solar.de/downloads/ts/ts_handbuch_twinsolar_eng.pdfthey used this fan  http://uk.farnell.com/ebm-papst/6224n/axial-fan/dp/1256121Billi |
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Guinness no Grid comes near
1.6 kw and 2.4 kw PV array , Outback MX 60 and FM80 charge controller ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw windturbine
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knighty
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« Reply #23 on: July 06, 2009, 11:59:06 AM » |
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I guess of they overspec the pv pannel they will have better airflow when the sun isn't 100%,,,, they're probably worried about overheating ?
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daftlad
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« Reply #24 on: July 06, 2009, 01:17:31 PM » |
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My brain is broken.
I have been reading about static pressures in pascals or inches of water
does 100 pascals equal 1 milli bar?
errrrhhhhhaaaaggghhhh
It seems like catch 22. If you want good pressure and airflow then you need more power therfore more pv.
I want this to be cheap so I will start with 5 watt pv and just under 5 watt fan, if it doesn't work then double it and so on.
thanks everyone
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billi
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« Reply #25 on: July 06, 2009, 01:49:13 PM » |
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My brain is broken.
I have been reading about static pressures in pascals or inches of water
does 100 pascals equal 1 milli bar? I know that feeling i had a go a year ago on that to get my underfloor heating running in our attached tunnel and bought 4 ca 5 watt radial fans to be able to connect them in series ..... http://www.navitron.org.uk/forum/index.php/topic,2188.45.htmlStill not a finished product  Billi |
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Guinness no Grid comes near
1.6 kw and 2.4 kw PV array , Outback MX 60 and FM80 charge controller ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw windturbine
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billi
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« Reply #27 on: July 06, 2009, 02:51:03 PM » |
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Daftlad i am sure i could tell you , if i had the 2m2 of beer cans in my head Anyhow my radial fans with about 6 watt costed only 5 euro each so not a big loss http://www.pollin.de/shop/shop.php?cf=produkt.php&ts=40&p=OTkzOTk4Just try it i reckon with a 12 volt battery ( perhaps from a cordless drill ) Billi |
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Guinness no Grid comes near
1.6 kw and 2.4 kw PV array , Outback MX 60 and FM80 charge controller ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw windturbine
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sleepybubble
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« Reply #28 on: July 06, 2009, 08:12:34 PM » |
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I reckon after 2mSq of beer can's anything is possible. Especially on the same night! |
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;-)
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daftlad
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« Reply #29 on: July 06, 2009, 08:28:30 PM » |
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I reckon after 2mSq of beer can's anything is possible. Especially on the same night! It took bloody months and My Brother had given me a load of bitter cans which turned out to be steel so I had to get back to the hard drinking again! oh hum it's a hard life! Any one know of a UK supplier of computer cenrtafugal (radial) fans, the only places I have found them is RS and Farnell where they certainly are not priced to sell?.... 35 quid plus the drat laters |
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