While solar power is a great use of renewable energy, it comes with several disadvantages. The most obvious is that the power provided by a solar panel is directly influenced by the intensity of the sunlight available. At night, a solar panel won’t provide any power at all. On a cloudy day, a solar panel might only generate a small amount of power. Jelle Reith leaned into that with Explorer, a solar-powered art piece that throttles its own frame rate.
Explorer runs Tim Clarke’s famous Mars demo, which was a 3D animation of Mars-like terrain from 1993 that ran in DOS on a 386 processor. That animation was special, because it was able to generate smooth 3D graphics with very little processing power (by modern standards). Reith wanted to create their own version of the Mars demo to run on an ESP32-S3-MINI-1. While coding that from scratch (based on Mark Feldman’s Java version), Reith noticed that it was difficult to get both a high frame rate and a lot of terrain detail. Because the Mars demo required the full resources of the ESP32, Reith realized that any restriction in power would have a real effect on the demo’s performance. That led them to this art project.
Explorer has two solar panel arrays on either side of a small SHARP Memory display. That looks a bit like a satellite, which fits the theme. SHARP Memory displays work a bit like a mix between E Ink screens and LCDs. They offer much faster refresh rates than E Ink screens, but still use very little power. The Mars terrain renders in grayscale on that screen, with the ESP32 generating the terrain and graphics in real-time. When Explorer has exposure to bright sunlight, it can collect enough power to keep an 18650 lithium-ion battery from dropping too much juice and can run the demo at full speed. When sunlight is limited, it runs slower to reduce power consumption.
This required a complex system of voltage monitoring and usage of the ESP32’s sleep modes. Reith provides detail on the power consumption workarounds in their write-up. In theory, when starting with a full battery, Explorer can run the demo for almost seven months by carefully controlling the power consumption of the demo.