The Battery System
The installed battery system. Pictured here is the vertical gutter at the bottom, a master cutoff above that, in the middle is the Sol-Ark 15K, bottom right is the Homegrid Stack’d.
There was obviously a delay in the battery project. Most of this was due to Oncor. It seems that when you are putting power onto the grid via solar panels, they are quite happy to get things done quickly. However if you are generating power and storing the vast majority of it in your own batteries instead of their grid, they tend to get picky. The original plan was officially submitted several times, with the final version submitted in April (Oncor kept asking for changes). It was officially approved in at the very end of July, so I could finally be added to Kosmos Solar’s install schedule.
While the original system was going to be based around the Li On system, they were experiencing delays of all sorts mainly due to supply chain issues. But the new system is based around the vendor Sol-Ark and their inverter with lithium ion batteries from HomeGrid.
Technically it’s not done - the city inspector still needs to officially sign off on the thing, but as I got a PTO (Permission To Operate) letter from Oncor, it is up and running live. I expect the inspection to happen next week.
Installation
The install took three days, and the installers were quite thorough. They even did a few minor extras, like testing and removing an old electrical connection box (no longer in use and unrelated to any solar equipment), and securely attaching the Internet fiber optic box and my weather-resistant Ethernet box on the outside of the house. A final visit a few days later (after some monitoring parts came in) added a half day.
The Sol-Ark 15K.
Hiccups
Fortunately most of the hiccups have been minor, and between myself and Kosmos we’ve managed to work around them. Most of them relate to the configuration - there are multiple external systems connected to the Sol-Ark and multiple use cases, so this will just take time as data is gathered and the system is tweaked. I’ve already done some tweaking myself, but overall everything is just fine.
There is only one thing not impacted by the configuration in need of resolution. There is a monitoring device that uses PLC (Power Line Communication) to talk to the original 22 panels to monitor power levels (a non-critical function but one I’d like to have). I could technically live without that monitoring as I can get a general idea from looking at the smart meter data, inverter data, and subtracting the other 24 panel monitoring information from the equation, but this is an estimate only. Right now Kosmos is researching options, and I am not objecting to the idea of updating this not-so-modern monitoring system to something more current.
The new Sol-Ark inverter does connect to the Internet, and I chose Ethernet as the option. This offered me slightly more control and closed what I deemed to be a massive security hole as the WiFi setup is wide open thanks to a non-configurable hardcoded password that has been published publicly. I configured the Ethernet drop to be a part of the solar VLAN with the other insecure solar devices. I’ll be doing a complete security evaluation and write-up on the Sol-Ark in the future. In the meantime I have configured the horrid app and it is talking to the China-based cloud server where my data is going, but I have purposely disallowed remote access in. For example the Sol-Ark inverter itself has port 80 open with no password, which is terrible when you couple that with the broken WiFi - insane for this day and age. sigh…
Cost
This one is surprising, at least for me. Originally I had budgeted $35k for the battery system, but with the advent of some alternate vendor choices as well as improvements to products, it came in at just over $28k. Considering the fact that I will be able to take a quarter of this off of my Federal taxes, this will result in a cost of $21k. Right now if the grid goes down, the entire house will stay up until the battery drops below a certain level, then the secondary panel kicks in and only critical systems are pulling from the battery. Yes this could eventually drain the battery completely, especially at night, but the next day during daylight we’re back to charging. For me, this is worth the cost.
All told, when factoring in the cost of the solar panels, the entire system will have paid itself off in roughly 7 to 8 years, but bear in mind I have not calculated in the current price of energy. This is going off of rates I was paying in 2019. As rates increase, this means I will be “saving” even more money, paying it off sooner.
The Homegrid Stack’d system. Each of the beige modules is a 4.8kW battery for a total of 24kW capacity.
Physical Security
One concern I had was physical security. Anyone driving up the street could see the batteries, tweak settings, shut things off, disconnect and steal things, and perhaps even kill themselves if they chose to start poking around. My backyard had a nice 8 foot board-on-board fence around it, so this was extended to cover the entire area around both the existing and new equipment (you can see a bit of it in the top picture). This is of course on top of the fact I now have an Ethernet switch mounted out there, and numerous solar devices that can speak WiFi with the hard-coded password on a tag on the side of the unit.
There are a few things to consider when physically securing things, as this also encloses the meter which Oncor needs access to. I had to set up a lock on the gate and the gate code needed to be on file with Oncor (plus Kosmos has it, as well as the company that does my yardwork). This meets regulations in my area, but different rules might apply to other areas.
Yes this is a lame form of security as this barrier can be defeated with a ladder (or an axe), but the fence went up before the battery install, and so anyone driving by basically saw the Kosmos van out in front of a house that has solar panels on the roof, and they were working behind a closed gate.
Gear Breakdown
Here is a list of solar-related gear that was installed before the battery system was in place:
22 Mission Solar 300W solar panels
11 DC to AC APsystems YC-500 micro-inverters for pairs of 300W panels
APsystems ECU-3 version 4 monitoring device for 300W panels (talks PLC to micro-inverters, configured for Ethernet)
24 Mission Solar 310W solar panels
1 SolarEdge SE6000H HD Wave DC to AC inverter for 310W panels
1 SolarEdge monitoring device for 310W panels (configured for Ethernet)
2 cutoff switches for AC electrical runs from inverters
Here is a list of the new gear for the battery system:
1 Sol-Ark 15K inverter system
1 Sol-Ark combination WiFi/Ethernet dongle for remote access and management, in Ethernet mode
1 Homegrid Stack'd battery system, 24kW capacity
1 secondary circuit panel for critical circuits only
1 "gutter" (enclosed weather-proof vertical metal tray) for housing various wires and connections
1 cutoff switch from load (grid and solar combo)
Several sensors for monitoring mains from main circuit panel
Misc pipes and connectors to hook entire system up
A lot of the cut-off switches are required by Oncor or Arlington city regulations, most by both.
Conclusion
Am I happy with the choices on going with batteries and the vendor choices? Absolutely. I’m in the middle of suburbia, but I’m ready for an extended outage, and I can still take advantage of the conveniences of city life and maintain the independence of someone off the grid in the middle of nowhere. Okay, I’m not off the grid, but this is pretty damned close.
