I may only be a few days in, but I’m loving my new solar plant. Yes, it will take a decade or so for it to actually pay for itself, but knowing that I’m driving on sunshine and operating my entire household as close to truly carbon-free as one can reasonably get is a great feeling.
Of course, it’s not perfect. The software stack that comes with the inverter leaves a lot to be desired.
First, the included software only checks and records the status of the system about every five minutes. When you’re trying to tune your energy usage, that means you can make an adjustment (say, increasing the charge current to the car’s batteries) but then you have to wait up to six minutes to get an updated reading on whether you’ve made the right adjustment. In that time, a cloud might have drifted over or the sun rose a bit more and the reading you get just doesn’t tell you what you need to know. So you do it again, with another six-minute wait. Imagine if you’re trying to boil pasta: it’s boiling over, so you turn down the heat. But then you’re not allowed to look at it again for six minutes, during which time the water might have cooled so much that it stopped boiling. Now you have sticky, starchy noodles. You try to compensate by turning the heat up a little, but when you’re allowed to look six minutes later, your pot has boiled over and made a mess of your stove and possibly your dinner.
The other is a problem I alluded to about ten days ago: the default software stack gives the manufacturer the ability to modify the equipment by remote control. They can reduce the functionality, turn it off altogether, or even cause it to operate in an unsafe manner that could put me and my family at risk. I don’t, as it happens, have any particular reason to trust the manufacturer or not, but I also don’t have any confidence that, even if they aren’t malicious, their software quality control and cybersecurity are good enough to guarantee that they won’t make a coding error or that a malware miscreant won’t get access to their — and thus my — systems and hold my energy and my personal safety hostage.
I mitigated both these problems with a device called Solar Assistant.
Solar Assistant is actually a software product which you can purchase for under $60 and install on a Raspberry Pi. I have several Pi’s floating around, but I really wanted a turnkey system to make sure I got up and running as quickly as possible. I purchased a complete system consisting of a Pi, case, power cable, and SD card with software pre-installed for a little over $200. For my particular inverter, I also needed a special cable. Everything arrived within a week, and it took me less than half an hour to install it, configure it, and get it running.
My inverter and battery stack are no longer directly connected to the internet. I can access the Raspberry Pi — completely under my control — instead. I get the same information I got from the default setup, but updated every 2-3 seconds instead of every five or six minutes. I can also tweak some internal settings on the inverter that make it work better for my use case. I’m connected with a cable, not Wi-Fi, so I don’t have to worry about somebody messing with me by jamming my Wi-Fi (the inverter is quite a distance away from my home). I bought and paid for the inverter; it should be under my control and now it is.
Next, I’m going to write some software that takes advantage of the Solar Assistant’s APIs so that I can adjust the charge rate on my car in real time (Tesla’s APIs are also published, if not officially supported) to always optimize where my energy is going.
As a bonus, which might or might not prove important, Solar Assistant is compatible with Home Assistant, a free and open-source home automation system. I’ve used internet-of-things (IoT) devices such as security cameras, door locks, irrigation controls, HVAC controls, and lighting but they’ve all relied on centralized, proprietary systems. In other words, you don’t own these devices. Home Assistant is a locally-hosted, non-proprietary solution so you don’t have to worry about companies spying on your devices. I’m not sure if or how my solar plant will integrate with the Home Assistant IoT devices I’m installing, but it’s nice to know it can if the need arises.
—2p