Sunny days are good for more than just your tan: by utilizing solar power, you can cut down on your electricity bill and give yourself the flexibility to stay connected while off the grid.
Despite how intimidating solar power seems, with some basic knowledge of what the different components do, and how to safely set a system up, going off the grid can be a snap!
When building a solar array, you will be working with some very high voltages, and it is essential to follow proper safety guidelines. Here are four basic safety rules to adhere to:
- Always use thicker wire than you calculate yourself needing.
- Always wire fuses into your circuit, especially between your panels and battery bank.
- Always use a charge controller that can handle the huge power being output by your solar panels.
- Always hire a professional if you feel uncomfortable working with high voltages.
The components of an off-grid electrical system can be broken into four categories: sources, storage, connections, and loads.
Sources: These are the source of the electricity—in our case, the solar panels themselves.
Storage: These components store the electricity, for later use. Solar systems utilize a group of deep cycle batteries wired in series, known as a battery bank.
Connections: These consist of the pieces that tie the system together, such as wires, charge controllers, and fuses. From a safety perspective, the connections are the area most likely to cause an issue down the road, unless proper precautions are put in place.
Loads: These are the end goal; any piece of equipment that uses electricity is a load. This includes power inverters for our 120V appliances, as well as any 12V appliances we may be using.
Generating Power with Solar Panels
Solar panels work by converting energy from the sun into usable DC (Direct Current) electricity. This DC is then stored in batteries and used to power our devices.
When the Sun’s rays encounter the photovoltaic elements of the solar panels, energy is transferred to the electrons within. These excited electrons then zip around the circuit of the solar panel, from negative to positive ends, charging our batteries and keeping the lights on.
Solar panels generally come in two flavors, based on the molecular composition of their photovoltaic elements: black Monocrystalline and blue Polycrystalline.
In broad strokes, Mono panels are more efficient and more costly. Poly panels can be a good budget choice; however, one may find themselves needing more Poly panels to get the same power output generated by fewer Mono panels. If you are working with limited space, such as on top of an RV, Mono panels are the way to go.
Storing Power with a Battery Bank
There are many, many different types of batteries out there; so many that choosing the perfect ones for your battery bank can be a bit daunting. To simplify things a bit, keep these two rules in mind when choosing batteries:
- Always use deep cycle batteries—these are designed to be steadily discharged and sustain their power output. Using shallow cycle batteries, like car batteries, will result in a reduced life span of your battery bank.
- Deep cycle batteries can generally only be discharged to half of their full capacity before needing to be recharged. When considering your battery needs, look at your daily power consumption and multiply it by two.
Outside of those two golden rules, the choice of which batteries to use comes down to budget more than anything. Specifically, if you would prefer to pay more upfront for a more efficient, longer-lasting lithium battery bank, or get up and running for less money with a lead acid battery bank.
Before putting any of the pieces together, we need to know the proper thickness of wire, amperage of fuses, and max power of our charge controller. You wouldn’t march a parade over a new bridge without figuring out how much weight it can hold; same concept here.
Safe wire thickness comes down to how much current will be flowing through it at a given time, as well as the actual length of wire needed. Too thin and the wire could melt, causing an electrical fire.
To calculate the proper thickness, or gauge, of wire to be used, default to using a wire gauge calculator, and then increase the gauge by one or two. Note that wire gauges are backward: larger gauges use smaller numbers, and vice versa. So, if you calculate a safe gauge to be 10, use an 8-gauge wire.
Figuring out safe fuse amperage is far simpler than calculating safe wire gauge. Simply divide the maximum power (P) in watts of the circuit by the voltage (V) running through it to get the current (I) in amps. This is a basic equation in physics, known as Ohm's Law:
Charge controllers regulate the rate of charge coming into your battery bank from the solar panels to ensure safe operation. These units will have the max power input listed on them. If using a 400W solar array, you would need at least a 400W minimum power rating for your charge controller.
Powering Your Devices
Solar panels generate electricity in the form of 12V DC. While 12V is fine to power lights, charge our phones, or run fans, this does raise an issue: most everything we use in our homes is powered by 120V AC (Alternating Current). Note: this mains voltage differs in some countries, so do double-check.
To solve this, we use an inverter. Inverters work by converting the 12V DC into 120V AC and come in two varieties, Pure Sine Wave or Modified Sine Wave. In almost all cases, pure sine is the way to go, especially if using delicate electrical equipment like computers or games consoles.
Building a Solar Power System
Sources, storage, connections, and loads: these are the pieces that form an off-grid solar system. By exercising proper caution and doing a few simple calculations, you can safely build a reliable source of electricity to cut down on your electrical bill and keep you connected, no matter where you are.