orbitoid
Posts: 14
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Re: Solar Power

Wed Jan 25, 2012 2:14 am

Mezo said:


There is the F&P smartdrive (washing machine motor) option, puts out about 300w of electrickery, theres also some good info on solar on this site also.

http://www.thebackshed.com/Win.....ents.asp#2

Great site with all sorts of hacks.

Mezo.



Wow i have been looking for a site like this for ages! Thanks

Now i just need to find an old fisher and paykel washing machine.

Tomasz
Posts: 1
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Re: Solar Power

Wed Jan 25, 2012 2:25 am

RaTTuS said:


http://www.amazon.co.uk/Powere.....00681LZ68/

now would that power an RPi?


This is a toy. The lithium battery inside will die after 10-12 recharges from overheating under the sun. Mine was like a pillow ...

If you don't live in "cloudyland" 20Wp panel should be enough for running the setup 24/7. Ofc. you will need also good battery to keep little charge for the night.

orbitoid
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Re: Solar Power

Wed Jan 25, 2012 3:04 am

Any links to a good solar panel/battery combo that might work well?

I guess it will need to be 5V 24Ah (as stated above) if we want it to power the Pi for a whole day without any charging? For those days where the sun doesn't come up

I don't want to go purchasing a battery that will fail after a few charges.

kme
Posts: 448
Joined: Sun Sep 04, 2011 9:37 am

Re: Solar Power

Wed Jan 25, 2012 3:21 am

You'd need a voltage regulator to keep a stable 5.0 V supply. And 24 Ah is way over-optimistic in the real world. Go for the double.

Some one up to design a voltage regulator PCB taking any DC input and outputting 5.0 V for the R-Pi? Price point next to zero and size too.

orbitoid
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Re: Solar Power

Wed Jan 25, 2012 3:27 am

kme said:


You'd need a voltage regulator to keep a stable 5.0 V supply. And 24 Ah is way over-optimistic in the real world. Go for the double.

Some one up to design a voltage regulator PCB taking any DC input and outputting 5.0 V for the R-Pi? Price point next to zero and size too.


This looks like it should do for between 7-18VDC

pretty cheap too.

http://www.newegg.com/Product/.....6882021214

Input Voltage: 7-18V DC Output Voltage: 5V DC Output Current: 1 amps (1000mAh)

spurious
Posts: 343
Joined: Mon Nov 21, 2011 9:29 pm

Re: Solar Power

Wed Jan 25, 2012 3:33 am

kme said:


You'd need a voltage regulator to keep a stable 5.0 V supply. And 24 Ah is way over-optimistic in the real world. Go for the double.

Some one up to design a voltage regulator PCB taking any DC input and outputting 5.0 V for the R-Pi? Price point next to zero and size too.


http://www.maplin.co.uk/lm2940.....lator-8063

kme
Posts: 448
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Re: Solar Power

Wed Jan 25, 2012 3:48 am

spurious said:


kme said:


You'd need a voltage regulator to keep a stable 5.0 V supply. And 24 Ah is way over-optimistic in the real world. Go for the double.

Some one up to design a voltage regulator PCB taking any DC input and outputting 5.0 V for the R-Pi? Price point next to zero and size too.


http://www.maplin.co.uk/lm2940.....lator-8063


I hope the R-Pi Shop will stock such, as they are not necessarily easily accessible anywhere. I'd have a hard time to find these in Denmark as a private individual not buying bulk numbers.

error404
Posts: 351
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Re: Solar Power

Wed Jan 25, 2012 5:31 am

Orbitoid said:


Any links to a good solar panel/battery combo that might work well?


It's hard to dimension a solution without really having a good idea of what the power consumption is. I believe the number that's been thrown around is 2.5W maximum? So a day at maximum is going to be 60Wh. Call it 100Wh, building in some tolerance and efficiency derating. So your solar system needs to collect at least 100Wh per 24 hours to stay running. During winter you can expect maybe 5-6 hours of decent sunlight. A 20W panel is thus probably just sufficient. Say something like this: http://www.amazon.com/Instapar.....038;sr=1-5

Then you need a charge controller and a battery system capable of storing ~100Wh. An MPPT controller is probably required given the math above, though you could just over-rate your panel choice to compensate for the lack of one. Not sure which option is more cost effective. $20-100

Finally, a battery. SLA will be easiest, most cost effective, and most reliable. This is not going to be a very portable solution anyway, so it's the right choice. Buy locally as shipping for what is basically a lead+water brick is expensive. Go with either a single 12V or 2x6V (other configurations possible, of course), you'll want at least, say 12Ah. $50.

Add a 12V->5V regulator, which you can poach from a cigarette USB charger or buy loose from eBay. $5.

Add wire, fuses and etc. $10.

This setup is at about $150, and it's pretty optimistic about solar panel effectiveness... You might be able to use a smaller solar panel and battery if you measure the actual average power consumption of the device. I really doubt it will be anywhere close to 2.5W. Probably half that or less.

Themroc
Posts: 44
Joined: Fri Jan 06, 2012 9:35 am

Re: Solar Power

Wed Jan 25, 2012 7:14 am

kme said:


http://www.maplin.co.uk/lm2940.....lator-8063

I hope the R-Pi Shop will stock such, as they are not necessarily easily accessible anywhere.


This chip will convert electric energy into heat. At 12V input it would burn 3.5 Watt while r-pi ("A" model assumed) eats only 2.5. Very bad use of expensive PV energy! Go for a switch mode converter, one of them cheap USB car cigarette lighter adapters mentioned above will do. It shouldn't be too cheap though:


I received the 2 port USB car charger a week ago and have just gotten a chance to try it out. At first everything seemed to working well with it. It charged my Fiance's Samsung Moment extremely fast… almost…too fast. It went from 28% to 100% in about 4 minutes! I was amazed! Then I thought about the damage that can cause and quickly unplugged the phone from the charger. I was unfortunately too late. Her battery is now ruined and I need to buy a new one. This charger achieved the incredible charge rate by over-volting. This is extremely dangerous for delicate electronics such as cell phones, gps, tablets, ya know, things this charger is apparently designed for. Sadly her phone no longer holds a charge and you can watch the battery gauge drop 10% a second as soon as its unplugged from a good charger. Next time I will buy a quality name brand charger for something expensive such as cell phones. Lesson learned.


speedevil
Posts: 7
Joined: Tue Jan 24, 2012 3:27 am

Re: Solar Power

Wed Jan 25, 2012 5:44 pm

A 20W panel may be sufficient in good weather, in optimal conditions.

http://www.pvoutput.org/list.j.....8;sid=2940 - this is a nearby solar panel array.

It's 4kW.

If you look at the daily generation graph, you see that if you want it to run worst-case, you pretty much need to be able to survive several days at 1000Wh/kW.

This will drop out several days a year.

We need 2.5 watts constantly for 24 hours per day.

This is 60Wh/day.

Charge/discharge is perhaps 80% efficient with good batteries, bumping this up to 75Wh.

Assuming 750Wh/kW, you need 100W of panel.

And perhaps 200Wh of battery, minimum. ([email protected]) (however, if lead-acid, you need 500Wh, as it won't be safe to charge the battery with the full output of the panel)

This would have stopped working for maybe a week or two in November, and perhaps a few days in december.

If you wanted it actually to work all the time, you'd need more like a 150W panel, and a 750Wh

http://re.jrc.ec.europa.eu/pvg...../pvest.php is a useful resource for working out how much you're likely to get in a given month for a location in europe.

However, the monthly totals it can produce are averages - as you can see from the data above, you need to cope with several days of very low output.

It may not be quite as bad as the data above presents it.

It's possible you can gain perhaps 20% with a system optimised for low-light conditions - that is efficient even when the solar panel is dimly illuminated.

In addition, of course, powersaving may be possible to use under 2.5W.

Plus, you may be lucky enough to live where it's sunnier.

eeyore
Posts: 3
Joined: Tue Jan 17, 2012 8:10 am

Re: Solar Power

Wed Jan 25, 2012 7:32 pm

Keep up the good work guys.
I"ve been thinking of powering a unit via solar for use in the allotment. A mix of wind and solar.
Why?
Well what I"m thinking is a method of recording or sending me back info on my plants or sending pictures from a camera if something is tripped (shed alarm or animals?) Also could remote trip water sprinklers etc.

takeshi
Posts: 4
Joined: Wed Feb 22, 2012 3:43 pm

Re: Solar Power

Wed Feb 22, 2012 4:36 pm

Has anyone considered this panel?

http://www.xscyz.com/index.php.....cts_id=184

It looks, to me like it could be a pretty decent bang for the buck panel.  Especially for this purpose.

bredman
Posts: 1415
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Re: Solar Power

Wed Feb 22, 2012 4:55 pm

takeshi said:


Has anyone considered this panel?


The specifications are too low. At absolute maximum it could generate just enough to power an RPi without any peripherals. You would not be able to tolerate any losses caused by battery charging.

Note that the specifications are VERY optimistic. Tests were performed at irradiance of 1kW/m2 which is similar to what you would get in the Sahara desert.

takeshi
Posts: 4
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Re: Solar Power

Wed Feb 22, 2012 5:11 pm

I was thinking at $23, one could build an array with them that would easily rival the other $170 panels people have been posting.  If you had 4 of them, that would be plenty to charge batteries and power a pi wouldn't it?

drgeoff
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Re: Solar Power

Wed Feb 22, 2012 5:41 pm

takeshi said:


I was thinking at $23, one could build an array with them that would easily rival the other $170 panels people have been posting.  If you had 4 of them, that would be plenty to charge batteries and power a pi wouldn't it?


I doubt that even 4 of those panels and any reasonably sized rechargeable battery stack would be enough for 24/7/52 operation - at least in the UK and similar climes.

takeshi
Posts: 4
Joined: Wed Feb 22, 2012 3:43 pm

Re: Solar Power

Wed Feb 22, 2012 5:55 pm

So upon further research I think I'm going to use a car battery (free since I have a marine deep cycle one I'm not using).

Charge it using an array of 2-4 of these panels($46-$92):

http://www.xscyz.com/index.php.....cts_id=184

and this charge controller $16:

http://www.amazon.com/gp/produ.....d_i=507846

and this adapter $4:

http://www.amazon.com/Cigarett.....038;sr=8-1

My project will only be running at night, so this should be more than adequate since the Pi can be shut down during the day.  Also, if the Pi has to stay shutdown for a few nights due to insufficient charging during the days, that's okay with me.  I plan on leaving this project in a remote location to collect information for extended periods.

Also, I don't have the challenge of living in the UK.  We have low humidity and get plenty of sunlight here!

riggsre
Posts: 52
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Re: Solar Power

Wed Feb 22, 2012 8:11 pm

Do you have a Harbor Freight in your area?

Or harborfreight.com


hellsing
Posts: 7
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Re: Solar Power

Thu Feb 23, 2012 1:54 pm

Do not forget to power a screen :p

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cowpat
Posts: 90
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Location: London
Contact: Website

Re: Solar Power

Tue Apr 17, 2012 12:47 pm

Being in the UK is a big disadvantage for me, but I've been doing a bit of homework on a solar system for my project... I think one key factor that I haven't seen mentioned in this thread is the seasonal variability of solar systems, particularly at 51° N

I need my system to run 24/7 from March to October, and the companies I've been speaking to have suggested solutions in the order of 60W, with 100Ah of batteries to give 3 days power in the event of prolonged cloud/snow.

From the sums I've looked at these figures get even less favorable the closer you get to Jan+Dec.

I've only got a camera and and IR led to run, and I think I gave them an estimated 6w to work with.

I'm looking at splitting the battery bank into 3x37Ah to make it easy to carry to site... once it's boxed up 100Ah = 30kg! I looked at Lithium chemistry Steatite do a peli case full of lithiums, 100Ah at 16kg but they quoted about £1300 over the phone.

I'm very interested to hear how some of these ideas work out... as I wholly conscious of the fact that that quote for 60W + 100Ah ultimately comes from someone who sells solar panels.

freezer2000
Posts: 1
Joined: Tue Apr 17, 2012 6:25 pm

Re: Solar Power

Tue Apr 17, 2012 7:29 pm

For people in Germany:

http://www.pollin.de/shop/dt/N....._30_W.html

Not sure about shipping to EU etc.

bugmage
Posts: 1
Joined: Thu Apr 19, 2012 10:19 pm

Re: Solar Power

Thu Apr 19, 2012 11:22 pm

I'm just going to hook it to a http://solarjoos.com/ I bought a while back, looks like they upped the price recently but should be a simple solution for something like a xmbc box

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jbeale
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Re: Solar Power

Thu Apr 19, 2012 11:39 pm

Yikes, price is a bit high, but it looks more than capable of powering the Pi.

john_wage
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Re: Solar Power

Thu Apr 19, 2012 11:50 pm

jbeale said:


Yikes, price is a bit high, but it looks more than capable of powering the Pi.


- Starting with a full battery, for a couple-three hours or so. Maybe 4 in good sun.

Edit: that is not counting any display, if you want to use that in a truly mobile scenario.

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cowpat
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Re: Solar Power

Fri Apr 20, 2012 11:40 am

I concur with John - my estimate of 60W and 100ah backup didn't include a screen. One of the sites I have looked at quoted 4hrs of peak performance in uk summer, falling to 1hr in winter.

http://www.windandsun.co.uk/So.....output.htm

this little tool might be handy, it makes graphs of power over time for the year.

http://re.jrc.ec.europa.eu/pvg...../pvest.php

poing
Posts: 1132
Joined: Thu Mar 08, 2012 3:32 pm

Re: Solar Power

Fri Apr 20, 2012 12:07 pm

I think for continuous operation a combination of solar and wind power would be optimal with a large battery to overcome windless nights.

Something like this: http://www.mdpub.com/Wind_Turbine/

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