Monday, June 16, 2014

Early Solar Powered Computers

August 1999, I asked some hands-on PV pioneers who had the first photovoltaic powered personal computer (PV powered PC). Here are their responses and some comments.

My own PV powered PC experience began July 1982. While living in the Arkansas Ozark mountains, I got an Apple II Plus. I wanted to connect the computer directly to home 12-volt DC PV system instead of using an inverter so I called Apple Tech Support to make sure what I wanted to do would not harm the computer. Apple technicians told me that my computer was the first PC they knew of that was PV powered. I connected my 12-volt PV system battery bank (6 each 2-volt 400 amp-hour C&D lead-acid cells) to a separate 12-volt group of gel cells. The gel cell 12-volt output was connected directly to the Apple’s hard drive and the computer's 5-volt RAM was connected through a voltage-dropping resistor.

When I moved to Los Angeles in 1982, I continued to power my Apple II with PV using a Tripplite 550 inverter with a 120-volt square wave output. I have also owned Compaq, Kaypro, IBM and PC clones that I powered with Tripplite, Heart and Trace inverters. Most PC power supplies can work with unfiltered utility power so they could also work with most of the square and stepped square wave inverters available back then. I also powered my Sharp laptop and Epson notebook with PV power and a voltage dropping resistor into the internal battery. Computers and PV power are very compatible. This blog was written on a desktop PC in a completely solar powered home and office. See

Here are a few of the 1999 RE-Wrenches replies. Someone wrote that a company named “KISS” (Keep It Simple Solar) has a patent for a solar powered computer, but I couldn’t confirm it. He also wrote that KISS sold out to Advance Power (Power Experts) around 1997 or 1998. In 199, Sunwize offered a PV module to power PCs. IBM had an interesting patent for an amorphous PV module that was behind the PC’s LCD screen. Office or outdoor light that passed through the computer screen's non-energized pixels and onto the PV module could charge an internal battery or capacitor. That was more than 15 years ago yet there are still no computers or hand-held screen devices that do not require plug-in charging.

Phil Karn reported: I dunno who was first, but right now (1999) I have three Linux systems running on solar power all day, crunching Seti@Home datasets. There should be a separate competitive category for solar-powered SETI. The last time I measured power consumption with a Brand Electronics power meter my three computers plus networking gear (various Enet hubs, cable modem, ADSL box, GPS receiver, etc.) was about 330 watts. That's with Seti@Home running on all four CPUs (one machine is dual-CPU). Idle CPUs draw significantly less power, at least under Linux. I figure my home computers use about twice as much energy as my EV1 (see Note) does on a normal daily commute (about 10 miles round trip). SDG&E comes to swap my meter tomorrow. Then I'm clear to enter SELL mode. I have an interesting saga to tell about doing net metering with TOU tariffing; perhaps I should write that up too. The bottom line is that little old me was able to get a big bad utility to change a tariff just for me. Of course, it helped to have California state law on my side. My note: The EV1 was General Motors’ wonderful electric vehicle that they recalled and destroyed. See

Walt Pyle reported: I doubt that we were the first, but we powered our Imsai 8080 that was built as a kit from a bag of parts in 1976 with 10 each 10-watt Solarex silicone-potted single-crystal silicon modules. Those PVs charged a pair of 8-volt locomotive batteries with 12 volts tapped off and one cell not used. I used a Tripplite square wave inverter to go from 12vdc to 120vac that rattled the transformer windings of the Imsai. Later, we replaced the Tripplite with a Trace inverter.

Dan reported: We manufactured the first solar power PC and won awards for it in 1995 at the University of Florida in Gainesville. See*/

Someone whose name I can’t recall reported: FWIW, I used a solar powered Apple IIc with LCD panel on archaeological projects in 1984.

Derek Dexheimer reported: I doubt this is what you want, but I remember playing with a solar panel and my old Tandy 200. This was probably 1988 or so. It was just me fiddling around for a couple days.

Dan Metcalf at reported: Check out my home web site. The whole system is 100% powered off of solar power.  I've been running this solar electric experiment since December 1998 and powering the web site since May 1999.  The system never runs on grid power unless I'm going to be away from home for more than 2 days, and so far that's only been a couple of times.

Loren Amelang reported: I built a Z-80 S-100 system in 1981 which took DC power from the PV array that powered my home and well near Philo, CA. At that time there were 6 each 35W Solec panels in a 12V array. A multipole switch moved several lead acid batteries between 12V charging configuration, and the complex series array needed to get the 8 and +-16 Volt S-100 supplies. It had the PerSci servo-actuated 8" DSDD dual floppy drive for the fastest response short of a real 14" hard drive (which I didn't feel I had enough PV to run). It had a 12", 12 VDC monochrome serial ASCII terminal, and/or a directly connected (5 inch?) monitor from an Osborne. The original Epson 9-pin printer (made entirely from metal!) ran from a Heathkit inverter when needed. It even had a 12VDC 300 baud modem, but there was no phone line. To access Micro-Net I would plug the ASCII terminal and the (acoustic coupled) modem into my pickup and drive to the only pay phone in the next town. When the Tandy Model 100 (the original laptop) came out, it made this payphone surfing much simpler, and became the serial terminal for the S-100 box. That same Tandy 100 is still plugged into my PV system right now, logging data from my water system! Today I have various modern laptops, plus a P200 ISA backplane system running from an Aquire, Inc. ACE-870C 24VDC input switching power supply with all the normal regulated PC voltage outputs. And the original flat panel Apple Studio Display, 25 watts for the most beautiful 15" screen image I've seen anywhere, plus it takes S-Video in from the satellite system. See a video about Loren’s off-grid home at

These replies plus email and snailmail exchanges with thousands of PV users confirmed what I had imagined. Back before the turn of the century, there were thousands of PV powered PCs ranging from the computers used by Home Power magazine founders and many of their readers, to Peace Corp volunteers and missionaries in developing countries, to techies and amateur radio operators, to people who just happen to have their PC plugged into their PV powered home.

Joel Davidson
June 16, 2014

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