Page 1 of 3

Web Server running only on Solar Power

Posted: Wed Jul 18, 2012 5:54 am
by Stirring
My Raspberry Pi project is to see how many years (uptime) I can keep my Raspberry running as a server on the Internet, powered 100% by Solar power generated at my house. Still a work in progress but you can check out the details at http://pi.qcontinuum.com/ Also check out my case. Enjoy.

Re: Web Server running only on Solar Power

Posted: Wed Jul 18, 2012 9:46 am
by CCitizenTO
I've done some math for the RPi solar powering...

The RPi uses 700mA (maybe less maybe more). This means you need a battery wih at least 24H * 700mA = 16,400 mAh (MilliAmp Hours) so that it can run for a full day without generating any power.

You may want to increase this even more. You may want to double up on this so you can have two sets of batteries feeding it so you can hot swap to perform maintenance on one package at a time. Basically the battery packs determine how much energy you can store to deal with Night-time, cloudy days, rainy days, etc...

5V * 700mA = 3.5 Watts

Now we know the RPi takes 5V and 700mA... This means it takes 3.5 Watts to power. That is before you take into account any peripherals you may need to power like USB Wireless Network Dongles. If you have these your numbers will increase since it will need more than 700mA and thus need more batteries to cover it as well. I'm sure you can figure it out. Anyways 3.5 Watts of power means you need to generate 3.5 watts constantly. Now since the sun is only out about 50% of the time (simplification) this means you need to double this number for your solar panel. As well since we arent putting the RPi into space you have to deal with cloudy days,inclimate weather and maybe sandstorms depending on where you live. Thus you might want to double that number again. So instead of a 3.5W Solar panel you'll need something closer to 14 Watt Solar panel.

Combining Batteries + Solar Panels ultimately the goal is to achieve power independance so that you dont need to plug your RPi into a wall socket. I applaud your effort and awayt to hear of your success in this endeavor since I'm thinking of similar stuff myself.

Re: Web Server running only on Solar Power

Posted: Wed Jul 18, 2012 9:58 am
by RaTTuS
nice ....
install uptimed
so you get to see the histories for when it fails ...

Re: Web Server running only on Solar Power

Posted: Thu Jul 19, 2012 2:39 am
by Stirring
The Solar Panels are rated at 45 amps and the battery is a 80AH battery. I have a graph showing the voltage updated every five minutes at http://pi.qcontinuum.com/cgi-bin/rrd/rrdgraph.volts and as you can see from the graphs the Raspberry doesn't even hardly knock the surface charge off the battery at night. I am having issues getting the Raspberry stable at the OS level but the Solar power hasn't been an issue. The Solar panels/battery are running the Raspberry and the Arduino Uno that I am using to monitor the power. The Arduino is powered through the USB connection to the to the Raspberry. They both are totally off the grid.

Based on my calculations the Raspberry could only use a total of 8.4AH in a 24 hour period. The 45 Watt Solar panels ( which I calculated at 3.5 amps with losses) would only need to charge the battery 2.4 hours in a 24 hour period to replace the power used by the Raspberry. The document I have on-line explains this much better. http://pi.qcontinuum.com/

Re: Web Server running only on Solar Power

Posted: Thu Jul 19, 2012 8:16 am
by RaTTuS
very nice info , so a 20W panel and a car battery may do the trick ....

Re: Web Server running only on Solar Power

Posted: Thu Jul 19, 2012 1:15 pm
by Arie
Nice!

Reducing power consumption of a raspberry Pi might be interesting for solar powered set-ups..

Re: Web Server running only on Solar Power

Posted: Thu Jul 19, 2012 3:35 pm
by CCitizenTO
Well maybe my math is off but either way with a 80AH battery and a 45W Solar Panel you've got more than enough excess power at your disposal to handle night times and cloud cover to make it to the next sunny day. ;)

Also if using a battery you might not want to use a car battery. Though it may be good to have some circuitry to keep the battery in the 40-80% charged range since I believe thats where optimum battery life resides (being full or empty kills battery life from what I've heard)

Re: Web Server running only on Solar Power

Posted: Thu Jul 19, 2012 4:08 pm
by Mortimer
A car battery can be deep discharged, just not repeatedly. A leisure battery which is similar to a car battery is designed to be discharged more deeply, but they tend to be far more expensive. A car battery could probably be deep discharged a couple of times before you start noticing any ill effects.

In this case, he has 960Wh to play with. So if we assume that the consumption is 1A at 5V, it would take a couple of days before you even get close to 30% discharge. I wouldn't call that deep. Any any deep discharge is going to need a week or more at that sort of power level to cause a deep discharge, unlikely enough that the risk to a car battery is negligible I think.

Re: Web Server running only on Solar Power

Posted: Thu Jul 19, 2012 4:18 pm
by RaTTuS
\o/ I like it - if I get some spare cash I may have a go at that then ....
and some time
and some sun.
;-p

Re: Web Server running only on Solar Power

Posted: Thu Jul 19, 2012 7:55 pm
by Cybertimber2009
Can you add a graph of the input voltage? It would be nice to see the charging voltage go up and down. At least it would help me determine where day and night was on your graphs. :p

Re: Web Server running only on Solar Power

Posted: Fri Jul 20, 2012 3:19 am
by Stirring
The battery is a deep cycle boat battery. It is a "starting" deep cycle battery so it is somewhere between car battery and a true deep cycle battery. I have used them for years on my UPS and they seem to hold up. This one was not new but it is in good shape. I have alerts setup to page (text message) me if the voltage gets low first yellow then red so I should have some time to fix an issue.

The voltage graph is the voltage right off the battery. You can tell night from day. Night is when it is very smooth. In the morning you see the voltage slope up followed by small voltage spikes all day long. I guess that is what I get for having a cheap Solar panel regulator but the battery is a good capacitor so it doesn't seem to be hurting anything. The total voltage drop during the night is so slight it is hard to see with the way I have the graph scaled. When I get some time I will play with the graph to try and make it more visible.

Re: Web Server running only on Solar Power

Posted: Wed Jul 25, 2012 10:41 am
by RaTTuS
I'm interested in solar powering an RPi and some other stuff in my shed,
what would I need ?
Solar panel 20W ?
Charge controller what type
battery - what type ? can I daisy chain several together ?

what sort of things to avoid?

Re: Web Server running only on Solar Power

Posted: Thu Jul 26, 2012 3:10 pm
by oscar
hello Stirring,
first off, congratulations on your great project and the nice way you explain and demonstrate the results.
I have a doubt: why have you used the arduino? I understand the raspberry pi has not a lot of processing power, but checking analog inputs every few minutes should not affect its performance, isn't it?
what do you think?
thanks in advance!
òscar.

Re: Web Server running only on Solar Power

Posted: Thu Jul 26, 2012 4:24 pm
by Mortimer
Possibly because the Raspberry Pi needs a device attached to it to take the analogue measurements and convert them into a digital form for it. This device might as well be an Arduino, as this has analogue GPIO built into it.

Re: Web Server running only on Solar Power

Posted: Fri Jul 27, 2012 7:20 pm
by oscar
hello Mortimer,
my wrong... I thought the raspi had also analog inputs...
thanks for the answer,
òscar.

Re: Web Server running only on Solar Power

Posted: Fri Jul 27, 2012 8:07 pm
by pygmy_giant
the site pages actually load quicker than most! how much traffic are you getting?

Re: Web Server running only on Solar Power

Posted: Fri Jul 27, 2012 10:06 pm
by jbeale
Looks great, and fast server response. Surprised you prefer to have your panels on the deck, if you plan for years of uptime, though. Seems like the roof would be more out of the way. Isn't it possible to have a bracket that just rests on the rooftop without nailing anything into the roof? Ok, it might blow off in high winds I suppose, unless it was made flat to the roofline and also heavy. And on the deck you can also more easily clean off the dust and bird droppings :-).

On the last graph on this page, seems like it should read "last year" not "last 24 year"
http://pi.qcontinuum.com/cgi-bin/rrd/rrdgraph.volts

Re: Web Server running only on Solar Power

Posted: Sun Jul 29, 2012 4:17 pm
by sparky51
Hi Stirring,

I've found your threat very interesting as I am thinking about doing a similar thing as I have a couple of solar panels on my shed roof, but I wish to run my Pi as a samba server.

Hope you don't mind if I ask but what did you use to drop the voltage from 12 to 5, I'm thinking I will use a travel plug, the type you plug into a 12v cigarette outlet and drop it to 5.

regards
sparky51

Re: Web Server running only on Solar Power

Posted: Mon Jul 30, 2012 4:34 am
by CCitizenTO
It looks like something is blocking your sunlight between Noon and 6pm... Unless ofcourse your battery charger is stopping from overcharging or something...

Voltage measurements are basically measuring how full the battery is right? I dont work with batteries very often myself.

Re: Web Server running only on Solar Power

Posted: Mon Jul 30, 2012 1:57 pm
by Raspbrain
Stirring,

That's an amazing project. I checked your RPi server running on solar power, and looks great. Can you share more details on this project? Where you purchased the parts, and the code for Arduino, and how to connect Solar panel and the battery, so on?

Thanks!

Re: Web Server running only on Solar Power

Posted: Mon Jul 30, 2012 6:48 pm
by pwl
Raspbrain wrote:Stirring,

(...)and how to connect Solar panel and the battery, so on?
Add me to this request. Would like to know how you solved those issues.

Re: Web Server running only on Solar Power

Posted: Wed Aug 01, 2012 5:54 pm
by yv1hx
I guess this link can be useful for you while calculating your Solar Panel:

http://www.davisnet.com/product_documen ... -power.pdf

Best regards,

Re: Web Server running only on Solar Power

Posted: Thu Aug 02, 2012 9:09 pm
by jarodium
This is indeed, a great project I i'm inspired to make something like this.

I would like to ditch the 80aH battery ( since it's bulky and I would like to keep the battery indoors without risking messing up my house.

So I would like to know if I can replace that 80aH battery for something smaller like:
http://www.tekkeon.com/products-mypall-specs.html

I'm guessing 2 or 3 of these connected to a converter (not sure if this is the right term, but I want the batteries to provide power without any power downtime ) to provide the Pi a 3 battery setup.
That way the batteries would be constantly charged by the panels.

Regards

Re: Web Server running only on Solar Power

Posted: Fri Aug 10, 2012 3:39 pm
by Stirring
Sorry I have been busy with real life. Let me answer some of the questions asked.

Mortimer's post answered the question of why I am using the Arduino.

pygmy_giant, looks like I am getting around 20,000 to 30,000 hits a day.

jbeale, The back deck is not ideal. The panels are in the shade in the morning. I did it because but I did not want to mount them on the roof. My deck is big so they are out of the way and not causing any issues in that location. They get plenty of sun for what I need. Thanks for finding the typo on the graph.

sparky51, I am using a 12v cigarette lighter adapter to drop it to 5 volts. I don't remember the brand or model and I am not at home right now to look at it. I could have done it with the Solar panel controller module but I wanted it separate so I could change the controller if I needed to without a downtime. I also was not happy with the voltages it was producing.

CCitizenTO, In the mornings the panels are in the shade. Most of the day they are in the sun. Voltage measurements are measuring how full the battery is. The voltage regulator in the Solar Panel controller module regulates the charging voltage.

Raspbrain, pwl, Re-read my site I think it has answers to most of your questions. I will have to hunt down my Arduino code and do a new post specific to it. Some new pictures of everything running may help.

Jarodium, My battery is over kill you could get a away with much smaller batteries. Deep cycle boat batteries are relatively cheap and I had the room. I use a plastic boat battery box to house the battery. Do the math and calculate what you need.

Re: Web Server running only on Solar Power

Posted: Fri Aug 10, 2012 6:56 pm
by sparky51
Hi Stirring,
Thank for the reply, that's what I did in the end I used a 12v cigarette lighter adaptor,
I did post a thread on here about my solar powered Nas but can't find it :roll:

Just like to say, love the graphs will be interesting to see how long you can keep your Pi online, I will be following its progress.

John