When most people ask how my “tiny house” is progressing; they want to see pictures of the interior. Everyone is fascinated by the flooring choice, wall materials, countertops, and bathroom fixtures. However, I get very few questions about the systems that actually run everything. The entire thing is designed to be 95% self sufficient and operate in an off-grid format.
For all my fellow Energy Nerds out there — this one is for you!
Solar System Overview:
- Three 330 watt panels on the roof connected to custom tilt + turn mounts (Roughly 1kw of solar input total)
- Charge controller for managing the solar power (Renogy Rover 60 AMP)
- 24V Battery bank = 4x 180AH 6V deep cycle batteries wired in Series
- 3000 watt inverter with 9000 watt surge capability. (AIMS Pure Sine)
Now the above system overview is probably too simplified for some people and a bunch of gibberish to others. First, I’ll provide a basic description of how this all works, and we can get technical later.
Whenever the sun is shining it’s releasing Energy that can be captured and used. The three solar panels on our roof are harvesting this energy and sending it (through thick wires) down into the container where it hits the Renogy Charge Controller. The charge controller stabilizes the solar power and inputs it safely into the batteries. It insures the batteries do not receive TOO much solar electricity (which would result in battery failure and be unsafe). It also keeps the solar electricity moving in one direction — you wouldn’t want electricity going BACKWARDS towards the panels. Basically, a charge controller is required in any off-grid solar system.
After the charge controller — the electricity is pumped into our battery bank. This is essentially four large batteries designed to be capable of holding various amounts of electricity at any given time. The amount of electricity contained in the batteries is displayed on the charge controller as a percentage. 0% meaning we have no usable solar electricity stored in the batteries and 100% meaning we are fully charged. Above you can see that I currently have 71% of usable electricity remaining, with 102watts of electricity going into the batteries from the Solar Panels. (the sun was setting at this point, because normally our panels are inputting around 700W on a sunny day) Making sense?
The next step is getting the sunlight energy from the batteries to the house. This is done with our AIMS 3000W Inverter which converts the battery electricity to usable “household” electricity and sends it to all the outlets, lights, appliances, etc… Whenever the Inverter is turned on, the outlets throughout the shipping container are active. Plug something in and it works! Just like a standard household outlet. The 3000W part of the Inverter is describing how much maximum electricity we have available through this size Inverter. FOR EXAMPLE: 5 lights, radio, the mini fridge, fan, and my laptop use about 265 watts — well within the capacity of this Inverter. As you turn things on, the amount of watts rises, with the maximum available being 3000 watts.
This particular AIMS Inverter also has the option to charge the batteries from a standard “on-grid” source of electricity. If the container was near a structure that has grid power available; you can plug the container into a outlet (insuring proper breaker size for the amp draw) and have this charge the batteries or even bypass our entire system and run the shipping container off standard power.
We will get into mechanical systems in a separate blog — but I want to note that our Minisplit (which is how we have air conditioning during summer) uses roughly 825 watts and is the biggest electrical user in the shipping container. Recently, during a sunny 90F day — I worked for 6 hours with the Minisplit providing AC the entire time. The batteries had a 100% charge when I arrived and were at 45% when I left.
Using a very inexpensive wall mounted power meter; you can view the total amount of electricity being used at any given time. Below you can see that I am using 463 watts of electricity at this point in time. By looking at this little power meter, and comparing it to the Renogy Charge controller — you can actively see if you are using more energy than the sun is currently inputting. Pretty fun thing to do as you turn things on and the sun moves around 🙂
Solar System Budget:
- 330W Solar Panel x3
- $215 each = $645 total
- Renogy Rover 60 AMP Charge Controller (12/24V)
- $215 total
- AIMS 3000W Inverter/Charger
- $925 total
- Solar LCD Power/Energy Display
- $20 total
- 400 AMP/Hour 6V Batteries x4
- $85 each = $340 total
$2,145.00 total cost before wiring, disconnect, switches, etc
I’ll write up a technical article later that outlines how/why we wired everything including wire sizes, connections types, lengths etc.
For now, this is a good overview of where we started at for our Shipping container tiny house renewable energy system. We plan to double the battery bank in 1-2 weeks, but for now this is working great.