This project goes into the build of a portable and powerful off grid emergency solar generator with higher capacity than commercial units at a fraction of the cost. This system can keep a small fridge operating 24/7, charge your devices, power TV ,LED lights, Laptops. it is small enough to be stored away in your garage and portable enough to move where it was needed.
The main components used to build this generator are as follows.
4 Renogy 100 Watt 12 Volt Monocrystalline Solar Panel
Renogy Rover 40 Amp MPPT Solar Charge Controller
Renogy Deep Cycle AGM Battery 12 Volt 100Ah
Sug 2000W(Peak 4000W) Power Inverter Pure Sine Wave DC 12V to AC
Renogy 20 Feet 10AWG Solar Extension Cable with MC4 Female and Male
BLACK+DECKER BM3B 6V and 12V Automatic Battery Charger / Maintainer
6 Circuit Fuse Block W/Negative Bus
Milwaukee Hand Truck with handle
Control Panel with USB Charger,LED Voltmeter,12V Power Outlet, ON-OF Switch.
To create a solar system that can truly meet your needs and cope with the variability of your environment, you really need to do some planning. This will help you avoid building a system that isn't up to the job and can save you considerable money by preventing the expense of replacing components later on.
To calculate the number of batteries and solar panels you will need to create a system to provide power in all seasons through inclement weather and at your particular latitude, you need to determine the devices you intend to power, log their power consumption across a few days using a power meter. Then find the reserve days . This is how many non sunny days the system can tolerate while still powering your devices. Also find the recovery time by calculating how many days of sun that will be needed to fully recover when the batteries have run down due to lack of sun. You also need to know the usable charging hours in day and the actual battery round trip efficiency since batteries give back something less than the amount of power used to charge them.
Here we use 4 100 Watt 12 Volt Monocrystalline Solar Panels to charge our 12 Volt Deep Cycle Battery. The panels are wired in series so that the voltages add together and you can get up to 80 volts from four panels. With this system there is enough voltage to begin charging as soon as there is any daylight at all. It also charges the batteries right up until dusk. Another advantage of the series wiring is that it is much better for long wire runs when the solar panels are not close to the generator and you can use less expensive smaller wire gauges for the solar panel runs.
To use panels in series you must have an MPPT type charge controller. They are specially designed to accommodate the high voltage of panels wired in series up to the particular controllers voltage limit .MPPT controllers are much more efficient converting nearly all the energy coming from the panels into charging power for the battery.
A 2000 watt pure sine wave inverter is used that can provide up to 4000 watts of surge power, and with enough battery support can run any conceivable device including those with motors. To store energy we use a 2 12V AGM marine batteries . These give plenty of reserved capacity that will last with reasonable care . They don't leak and can tolerate cheaper discharges and have very good round trip efficiency.
Four 100 watt solar panels are connected through the 40 amp MPPT charge controller . The panels can deliver up to 2400 watts of solar power in the shortest days of winter. And the charge controller converts solar power to charging power very efficiently and also support serial panel configurations increasing the systems capability.
A heavy duty hand truck is used for loading all the components . A frame made of angle iron is welded on to the platform to mount the batteries. Two angled straps are welded across the truck to provide more support for the battery frame.
The various components are mounted on a back support made of five eighth inch plywood. I use a tapered punch to make starter holes for all the screws that hold the components. The hand cart is laid on its back and the plywood board is aligned in such a way it doesn't block the holes. While the cart was on its back I screw down all the components with stainless steel screws.
For the project we use a thinner 18 gauge wire for the low current circuits, medium 14 gauge for the 12 volt port and heavy 10 gauge for the high current charging circuits. Red is always connected to the plus or positive connectors, black always to the minus or negative.
The positives and the negative connection coming from the solar panels are connected to the solar charge controller with the help of a quick disconnect Wire Harness SAE Connector. The negative of the solar charge controller is directly connected to the negative connection of the battery while the positive goes through a fuse block before connecting the positive of the battery.
The negative connections from switch, voltage display ,USB ports and battery charge meter is connected via a medium 14 gauge wire to the battery negative. The positives are connected to the battery through the fuse block. The 12 volt port is on its own fuse so it gets separate wires in the medium 14 gauge. The positive of the 12V Battery Charger is connected to the fuse while the negative is connected to the battery.
The batteries are placed on platform of the cart facing opposite directions so that positive and the negative terminals are near the plywood backboard where the components are attached.
The battery connection cables are cross connected to create a parallel 12 volt configuration careful to ensure the block cable connected only to minus terminals at both ends and the red cable connected only to plus terminals at both ends.
Next step is the orientation of the solar panels. As you probably know the sun is lower in the sky in the winter higher in the summer. In the winter, the days are also shorter as you really want to optimize for winter to get as much energy as you can when the days are short. Since my panels are fixed, we want to point them due south and angle them for the winter sun. There are tables you can find online that can give you a pretty good idea of the right vertical angle for your geographical location.
In the summer the sun is pretty much straight overhead, so the panels are optimal when laying flat. The angle panels are their most productive in the depth of the winter losing a little each day until the height of the summer as the sun is further off the winter angle. Meanwhile, the flat panels are less efficient in the winter because the sun is at a low angle but gaining each day as the sun gets higher in the sky.