In my quixotic quest for an entirely solar-powered van build, I also created a home automation server like that at my house. I ended up with an energy efficient computer with the same core specs as an upgraded MacBook Pro but with only 2/3 of the power requirement… and less than 1/3 the cost.
It’s been a long time since I built a computer. But building computer from scrap parts is exactly what got me interested in the subject at age 11.
I could have simply used a laptop and/or a Raspberry Pi. But I liked the idea of having a relatively powerful Ubuntu server in the van, just as I was accustomed to using at home. Much of my software developer work can benefit from some additional nearby computing power.
Understanding Computer Power Usage
Many people find power consumption confusing. It’s easy to learn quickly by observing, though. I bought a handy device called a Kill-a-Watt. You just plug it in to the wall, and it keeps track of power usage for anything plugged in to it.
Using this device, I quickly discovered that the LG UltraFine 5k monitor which I had bought for my MacBook Pro (2017 USBC) machine was not entering any kind of sleep mode, drawing a ~1.4 Kwh every day. Perhaps consumption increased when the screens were actually on, but this number was suspiciously high. If I locked the MacBook Pro screen and hooked it up directly to the Kill-a-Watt, its sleep mode drew effectively zero power.
By way of benchmarking, a 15″ MacBook Pro will consume ~45 while fully charged an operating in reasonable bounds. When charging or pushed hard, it can reach ~95 watts.
Building a Computer from Parts
PCPartPicker.com lets you pick parts for a computer, ensure that they are compatible, and even see the power consumption of your build. I began by reading this blog post in order to get some recommendations, but
My system (see part list) came in at a theoretical 99 Watts. It sports an i7 (2.9Ghz quad-core), eventually was upgraded to 32 GB of RAM, and a 256 GB SSD… making it very similar to a ~2018 15″ MacBook pro.
DC Energy Efficient Computers
Since the van is powered by solar and batteries, it’s most efficient to not convert the DC battery power into AC.
I found a company which offers power supply units (PSUs) which consume DC. After chatting with them via email, they recommended the M4-ATX for me. It could provide in the 250 Watts range, so it appeared to be way more than enough for the 151 Watt PC (giving me a little headroom, if I event want to sacrifice some efficiency for more computational power).
Putting it All Together
Keeping with the steampunk theme of the van, I used a decorative box to house the computer. At one point, I had fairy lights (LEDs) inside the vials you see outside, connected via USB to indicate when the computer is on (I removed these because the van is a small place and light is annoying). The small touchscreen monitor can be used for diagnostic purposes, but in practice I usually ssh in the server from my laptop.
The whole project cost about $750. It consumes about 30 watts in normal operating modes, but can peak up to 99 watts when pushed. Not bad, considering that it’s as powerful as a MacBook Pro for a fraction of the cost.
