Low Power Computer for Solar Monitoring Software

Ten or so years ago, I started running a computer at home as a web server and a server to upload data from my weather station to Weather Underground and Citizens Weather Observer Program. I used old Apple Macs to do this for a number of years, but it was painful how much power they used (80-100 Watts 24/7). I was on a quest for a low power computer - something I could build an off-grid solar-powered system to power it. I didn't find anything useful until 2006 or 2007 when I came across the Linksys NSLU2 - a network attached storage (NAS) device. It was great, but is now obsolete. It only drew about 3 Watts. It had a large community of people figuring out how to do cool things with it. And a group of people got Debian linux on it. I learned how to use and configure a linux box. It made a great home server for three years and inspired me to build my off-grid system to power it and a bunch of other stuff.

Modern Low Power Computers

Sheevaplug (and variants) - A few years ago, I replaced the Linksys NSLU2 with a much more capable Sheevaplug. The Sheevaplug has 512 MB of RAM and a 1.2GHz processor. It is also a low power computer - 2.1 Watts most of the time and up to about 3.75 Watts when it is working hard. I run Debian 6 Linux (Squeeze) on it and plan to upgrade to Debian 7 (Wheezy) when it comes out. The only issue with the Sheevaplug in an off-grid setting is it is a plug computer - like a big wall wart. I removed the AC power supply and added a power jack so it could run from the 5v DC-DC power supply I built for my NSLU2 (see http://www.plugcomputer.org/plugforum/index.php?topic=260.msg4246#msg4246). It works great and I use it for my home web server, weather station server, and my solar power monitoring. A good web site on loading Debian on a Sheevaplug is http://www.cyrius.com/debian/kirkwood/sheevaplug/.

I also bought a Seagate FreeAgent DockStar (not sold anymore). This computer is based on the same processor as the Sheevaplug. It has less memory (128 MB), but has a built in DC-DC power supply, four USB ports, and a dock to hold a hard drive (I have a 1 TB in it). I also power this from my off-grid system. It is nice in that it will run straight from 12 V battery power. It seems quite capable and provides backup and calendar services for our family.

Other Low Power Computers - I've been looking at the Gumstix and now the Raspberry Pi. They both look like you can run a full blown Linux on them. I haven't been able to find good power usage information on either of these, but the Raspberry Pi looks like a good solution for a low price. For both of these you need a regulated 5V power supply. What are others experiences in finding low power computers for monitoring solar power systems?

Comments

  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Low Power Computer for Solar Monitoring Software

    The Raspberry pi ticks all the boxes for me: cheap, 2 usb ports, tiny, cheap, built in ethernet, cheap, low power and cheap :)
    The only USB device I'm running at the moment is an RS-485 adapter to talk to the sunny island so have been powering the rpi itself with a simple 500mA USB phone charger. The lack of an onboard clock is not really an issue for me because it's connected to the network, so it syncs via NTP anyway, and the sunny island has an RTC I can poll if required.
    Supports full blown arm linux, the only limitation I've run into is that I had to use the pre-release Oracle Java 8 in order for floating point operations to be reasonably fast. Right now it's running Tomcat, mysql and mango automation software.

    Attachment not found.
    rpi.jpg 80.3K
  • jwrgorman
    jwrgorman Registered Users Posts: 22 ✭✭
    Re: Low Power Computer for Solar Monitoring Software

    We are experimenting with ARM-based computers, but one with a native RS-485 plug that does well with SMA inverters is this one:

    http://www.norhtec.com/products/mcjrmx/

    and one of the SMAs we're monitoring, along with 3-phase home consumption is here:

    http://data.solarnetwork.net/solarviz/node-dashboard.do?nodeId=35&consumptionSourceId=Input1

    we also talk to Enasolar, Outback, Morningstar, Xantrex and others - could monitor many devices from the same machine. SolarNetwork is all open-source and the dev guide is here:

    https://github.com/SolarNetwork/solarnetwork/wiki/Developer-Guide
    John Gorman / SolarNetwork Foundation
    e:john@solarnetwork.net
  • David and Laura
    David and Laura Solar Expert Posts: 139
    Re: Low Power Computer for Solar Monitoring Software

    The PogoPlus Series 4 makes an excellent low-cost embedded computer, with built-in Gigabit Ethernet and USB ports. You can purchase these for under $40 USD on Amazon (cheaper than a Raspberry Pi, and includes a case and 12vdc power supply), and then easily install Linux to run your own apps:

    http://archlinuxarm.org/platforms/armv5/pogoplug-series-4

    Once it's up and running, you can use one USB port for your boot/storage device, and the remaining USB devices to connect to RS-485, monitor temperature, etc. We're using the one we have set up to measure ambient radiation and light pollution levels, and we'll be deploying a few more to connect to other USB sensors.

    The SolarNetworks code looks pretty interesting —*Too bad that we don't know how to program in Java, and thus can't contribute.
    House: 2x SMA SI 6048 w 24x 2V DEKA Unigy II; 2x SMA SB 3000TL-US w 24x Sharp ND-H235Q2
    Cabin: 1x Magnum MS4024 w 24x 2V DEKA Unigy II; 1x Morningstar TS-MPPT-60 w 6x Sharp ND-H235Q2; 1x 200 Watt Harris microhydro
    Intertie: 1x SMA WB 3800; 1x Lambda GEN-600 DC Supply; 2x PSL pQube
  • jwrgorman
    jwrgorman Registered Users Posts: 22 ✭✭
    Re: Low Power Computer for Solar Monitoring Software

    Thanks! That unit does look very cool (and well priced) - and I've always been interested in Arch Linux. We currently have been using a Debian 6 image and are watching Debian 7 but also BSD and open to other ideas. I like the way you're using the same box to gather a whole bunch of different data streams: that's the architecture we're following as well with SolarNetwork. Also - we're developing in Java for a few good reasons, but it's not the only way for supported devices can be added. We've used C and C++ to implement the interfaces for different devices, got some help from a Perl script on one device, there's C# code out there too - so there's lots of room for collaboration. People should be comfortable with the languages they like to develop in, Java is just the one we've chosen - but we'll look at any code that will interface to a solar inverter or charge controller. The main thing anyway - for the end users of the SolarNode like solar integrators - is that it can be setup using a web browser, much like a DSL router's GUI interface, and connected to all your different hardware devices and web services, using point and click from the same box (development unit screenshot attached). Then, once it's collecting data and sending it up to the SolarNet server, you can visualize that combination of data streams in ways that you want to, using the SolarQuery web service API and say HTML5. We talk to SMA, Outback, Xantrex, Morningstar, Enasolar and some other devices like kWh meters. There's still a lot development underway, and takes a community to do it - but there's lots of ways to contribute with or without Java I think.... Got any TS-60s you'd like to try out? :)Attachment not found.
    John Gorman / SolarNetwork Foundation
    e:john@solarnetwork.net
  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    Re: Low Power Computer for Solar Monitoring Software

    rockchip has some very interesting and affordable ARM hardware. http://en.wikipedia.org/wiki/Rockchip

    http://liliputing.com/2013/03/first-android-tv-sticks-with-rockchip-rk3188-quad-core-processors-arrive.html

    I found out about them by acquiring a really cheapo 7" tablet that is pretty impressive for the money.

    check this one out:

    http://www.asiapads.com/en/dual-wifi-antenna-android-tv-stick-j22-quad-core-rockchip-rk3188-2431.html

    maybe something they have can be made to work?