A few posts back, I showed you this picture…
… as a hint of things to come.
Well, things have come.
While Kat has been working hard on tearing out the interior of the trailer, I have been working on getting the solar array up and going. We bought the system back in the Autumn of 2014 and we are just now getting to hooking it up.
With the help of our good friend Andres, who happens to be an electrician, we went over all of the components one day in mid August, and then we went out and bought a whole bunch of little fiddly bits that he needed to get the job done correctly.
One of those fiddly bits was a grounding plate.
This is a big plate of solid metal that you bury in the ground and run a large gage wire (#6) from it to your electrical box. This provides proper grounding to all of your electrical system. This is especially important if you get hit with lightning. ZAP!!
Here is the picture of the hole I dug for it and the trench for the wire. The plate needs to be at least 60cm (24″) underground.
In addition to the electrical stuff, I also had to buy some stuff to make a rack for the solar panels. I chose to use these things.
I’m sure they have an official name, but I don’t know what it is. They’re L shaped pieces of heavy gage metal with holes all along them. The holes make it convenient to connect them together.
I cut some pieces and bolted them together. Then I painted them with rust-proof paint so they will last longer in the weather. Then I started to haul them up and attach them to the roof over the trailer.
Here is the very start.
I chose a spot on the roof along a screw-line so I knew there was something to connect to. I also reinforced the wood strapping underneath the roof, with a much larger piece of wood, and then drilled holes through it so I could bolt the metal rack supports I had built through it.
It seemed to work just fine, though I had a heck of a time climbing up and down the ladder, going back and forth from under the roof to on top of it. Oh, and I had to remove a hornet’s nest the size of a volleyball to be able to do the work under the roof. Nothing a little late night spraying couldn’t fix.
Here is the shot of the two bottom supports in place with a cross piece at the bottom.
Lo and behold, here we have the first panel mounted on the rails.
I ran more of the same metal rails down the back of the roof, which is what I connected the main supports to. I can unbolt them and change the angle if so desired. However, after getting all three panels up there, it felt a bit wobbly, so I added some extra supports. It’s nice and sturdy now, but the number of bolts I need to loosen to change the angle that the panels are set at has increased drastically.
Oh well, I’d rather have it stable and a bit more work to change than have it fall over in a big wind or heavy snow storm. Here is a picture of the final result with all three of 250W PV panels installed.
Here is another look from a different angle.
With the rack completed, we now needed to build a platform for the batteries to sit on. These aren’t regular car batteries. They are massive, deep-cycle, marine style batteries and we have eight of them. Each one weighs in around 55kg (120lbs). Needless to say, they aren’t the easiest things to move around.
For the platform, I took three cinder blocks and spent some time leveling them as perfectly as I could. The batteries have liquid in them so you want them to be as level as they can be.
Once I had that part completed, I took a nice new wooden pallet we got free from one of the building centers in town, and I cut a section off it to the size that I needed for the batteries. A piece of 3/4″ (1.9cm) plywood was screwed down on top of the pallet and then I put extra pieces around the edge. The final result looked kinda like this, but less blurry.
With that all done, we could cart over the batteries. Here is the picture of all of the batteries in place on the wrack, with their connections to each other.
The solar panels are mounted and the batteries are connected. Its time to start putting all of the connections together, so we need to crack open that big control box you saw in the first picture.
Electrical work, like a lot of things, seems very complicated at a casual glance. In addition to the complicatedness, you have the issue where if you mess up you can electrocute yourself or burn your house down. These are not good things.
Luckily, I had Andres there to do all of the connecting. Each individual part is fairly straight forward, but once you start putting a lot of simple things together, it gets a lot to keep track of.
We eventually got everything connected. That was late yesterday, and the sun had already gone behind the trees, so we weren’t going to get much solar power that day. Today, however, it was a beautiful sunny day and around 10am I snapped this picture of the display on the charge controller.
In case you don’t read “electric”, that basically says we have 79.5 V(olts) coming in from the solar panels and the batteries are currently sitting at 51.8V. I’ll talk a bit more technically about it at the bottom, so read on if you want the technical stuff.
The system we bought is pretty fancy; far more than what we need for just the trailer. We bought it for the house, though we will be adding a few more solar panels to it when we get to building the Earthship. It will be overkill for the trailer, but that means we shouldn’t have to worry about having power, once the batteries are fully charged.
Our inverter came with a nice little monitoring device. It came with 15m of cable too, so we disconnected it from the control center and ran the wire into the trailer so we can keep an eye on things without having to go outside. Here is a picture of what it was doing this evening.
At the time that picture was taken, it was about 18:00 and I had turned on the generator. You see, with the batteries having been unused for two years, we want to make sure they are fully charged before we start using them. This is why we are still running the generator in the evening, to help top of the batteries.
Charging batteries is an interesting topic all on its own. We have 8 batteries, each one being 6V. A good analogy for a battery is a car tire filled with air. A tire stores a certain quantity of air at a certain pressure. Volts can be thought of as electrical pressure. Electrical quantities are measured in amperes, or just A(mps) for short.
Let’s say your tire is getting low and you want to put more air in it. If your tire is at 25psi (172kPa) and you want to get it up to 30psi (207kPa) you must be pushing air into the tire at a pressure greater than 30psi. If you don’t, you will never fill your tire. This works the same for batteries, except I can connect batteries together to make larger batteries. You can’t really do that with tires :P.
In our case, our eight batteries are connected in series to create one big 48V battery (8 * 6V = 48V). So if we want to be able to charge those batteries properly, we need to be pushing more than 48V into them. On top of that, you don’t ever want your batteries to drop down to only 48V, that would be too low. For this system, getting them up around 57 is where they will be fully charged, roughly speaking.
Luckily, each of our solar panels puts out 30V at max capacity. The panels are also wired in series so, they can push over 90V into the system. There is a magic box called a Charge Controller that takes that incoming voltage from the panels and regulates it to properly charge the batteries. Ours is pretty fancy and it does a lot more than just that, but I can’t say I know even half of it yet. Having the solar system now so we can learn about it and get used to it will make things easier when we get to using it in the Earthship.
You may be wondering where Watts come into all of this, as electrical devices usually have a maximum Watts rating on them. Well, Watts are just Volts * Amps, or pressure * volume if you’re following the analogy. Watts is a measure of energy. Electrical companies charge you by the kWh, which is kiloWatt-hour. A kiloWatt is just 1000 Watts. An hour, obviously, is a measure of time. This gives a unit of power, which is energy used for a duration of time. If I have a light bulb on that uses 60W and I leave it on for 1 hour, that’s 0.060kWh of power used.
The math can get heavy as you go further, but you can start to get an idea of what it would take to determine:
- How much energy your batteries can store
- How much energy your solar panels can put back into your batteries, on a good day of sunshine
- How much energy you can expect to use per day, based on the electrical appliances you use
Once you start working that out, you can figure out just how large a system you will need to run the stuff that you want. However, solar equipment isn’t cheep and your best course of action is to reduce your usage. If you can do that, and buy only the solar gear that you need, it will easily pay for itself within a short amount of time. As the costs of being connected to the electrical grid continue to rise, being disconnected from it makes a lot of sense.
Oh, just so you know, we put 3.3kWh worth of power into our batteries today from the sun. We look forward to days like this.