Portable Solar Power : A Basic Understanding
Solar power is a form of renewable energy that has been around for more than 2000 years. Early historians believed that humans used sunlight and magnifying glass to start fires. By the late 50’s we were using solar power to power satellites, and now anyone can use solar power for practically anything they want. There are a couple different factors when choosing which solar power system is right for your
specific application. One must consider charge time, panel location, battery storage, and appliance usage for starters. The right place to start is with a little background knowledge, so that anything I talk about will be understandable.
Current: The movement of electric charges, measured in amperes(A). DC refers to direct current, which is current flow in one direction only. AC refers to alternating current, which is current flow in two directions. The direction of current flow in AC alternates periodically depending on the source producing the AC waveform. Common waveforms found in North America are sinusoidal (sine waves.) Electronic components like computers require DC since information stored in memory are either on or off and as such, low voltage steady current is required. If an AC is used, the information stored in memory would be unstable since the current (and voltage) will constantly oscillate. For household use, AC is always used since it is easier to change voltages in AC. Voltage changes in DC require multiple components, which is why you need a power supply in your computer and laptop. The power supply in your computer is responsible for converting the 120v AC power from your house, into 3.3v,5v,12v DC, respectively. AC power is also used because of its efficiency travelling long distances as higher voltages like the ones used in power lines are needed for transmission.
Voltage: Is the electrical potential difference between two points. Think of it as the push that moves the electric charges. 0 volts means there is no electrical potential difference between the two points and as such, electricity will no longer flow between the connections of these points. I like to use the analogy of two water containers side by side, with a pipe connected between them. If the water level is the same in both containers, then the difference is 0 and no water will flow in the pipe. If, however, one container has more water, then the difference is higher, and water will flow to the container with less water until their difference is 0. Batteries are like containers of electricity in that the potential difference they carry (in volts) will push electric charge through a circuit until there is none left.
Figure 1:Voltage Analogy
Watt: Also known as power, is the rate of electrical work it takes to move one Ampere of current across one Volt. 1Watt = 1Volt * 1Ampere. Read the labels on any electrical appliance you own, and you will see how much power, in Watts it consumes.
Power Inverter: This device changes the current from DC to AC. It is required when powering AC devices from solar panel systems as all solar panels store their energy in a battery, and all batteries are DC.
Series connection: This refers to the way a component, usually batteries, is connected in an electronic circuit. Most components including batteries, have a positive and negative terminal. A series connection is one where all components are connected positive to negative in a closed circuit. Most older Christmas lights are connected in series. In a series connection, if one component in the circuit is disconnected, electricity will not flow. Therefore, when one bulb breaks, the rest of the lights will shut off.
Figure 2:Series Circuit
Parallel connection: A parallel connected circuit, is a closed circuit where the positive and negative terminals of each component share the same connection for the positive and negative terminals respectively. Unlike a series connection, the positive terminal of each component is connected to the positive terminals of the other components, and the negative terminals are connected to the other negative terminals. Houses in an electrical grid are connected in parallel because in a parallel circuit, if one component is disconnected, electricity can still flow to the other components.
Figure 3: Parallel Circuit
A solar panel is a collection of solar cells. The solar cells are responsible for converting sunlight into electricity. Each cell works independently to create a small amount of electric potential and so we need to combine all these independent cells to form a larger voltage so that we can “push” electrons along the wire into our battery or output device. Simply put, the more cells you connect in series, the higher the voltage. Most batteries require 15+ volts to charge so the panel itself will have around 36 cells. The cells are wired in series because series connections add voltage but keeps current the same. Parallel connections keep the voltage the same but increases current. From this point, panels themselves can be connected depending on their usage. You may only need a single 50W solar panel to charge one or two 12v batteries in your boat, but if you needed to power your house, you may need to connect somewhere around 20-40 panels with each panel rated at 150W. Remember, power consumption for your home runs in the kilowatt range. Also, when used for household appliances, we need AC power. All solar panels produce DC power, which is easy to use for charging batteries and phones. In cases where AC power is required, we must use an appropriate inverter to convert DC to AC.
Portable Solar Power
Solar panel products are common enough that anyone can get started with ready made products. What you need to know, is what you intend to power. If for example, you need solar panels to charge your cell phone on a camping trip, then you can easily find products made for that purpose, generally these products will feature some sort of weather proof solar panel, and a battery pack and output for a USB cable to plug your phone into. Since most phones require 5v chargers, these battery packs output 5v, and you just need to consider battery pack capacity, and solar panel efficiency when purchasing. These do not come with inverters since solar power is DC and phones charge through DC. Let’s look at some portable solar power products.
Solar powered light bulbs are extremely popular and available in many different products. The reason for this is because these products use LEDs (Light Emitting Diode). A regular incandescent light bulb produces light by heating a filament. Most of the energy it takes to make the light is wasted heat. In an LED, light is produced by electrons moving across a one-way barrier. Think of a turnstile for electrons. The movement of electrons in a diode produces light more efficiently than the light produced from heating a filament. The amount of light produced by a 60W incandescent bulb is about the same as a 10W LED. The LED won’t generate close to the same amount of heat as the incandescent and it consumes less energy. The cost of production is higher, and this reflects in its price, but the lifespan for an LED bulb more than makes up for its higher cost (approx. 1200hrs for an incandescent bulb vs. 24000 for LEDs on average.)
LEDs need DC to operate, remember current can only flow in one direction across a diode. If you connected an LED to AC, the bulb would flicker on and off as the current changes its direction of flow. It is for this reason each LED bulb used in your house has its own power supply to convert your house’s AC power into DC. In applications with a battery, there is no need to convert to DC as all batteries are already DC. Therefore, solar panels, batteries, and LEDs are natural allies.
Figure 4: Inflatable Solar Light
The LUCI Inflatable Solar Light is a simple little device that uses a small solar panel to charge a battery that powers the LEDs used in the lamp. It’s a very small device at 4”H x 4” D, the light itself goes up to 25 lumens so it would make a great little light for moving around the house at night or lighting up a small space. The battery gives 7 hours of light on 8 hours of direct sunlight charging which is certainly practical for its price and intended usage. The device itself is completely waterproof, inflatable and made to float, which makes it a good thing to have when camping or outdoors.
Phone chargers and solar panels have risen in popularity recently due to solar panel efficiency improvements. When buying a solar phone charger, the most important factors to consider are panel output, battery capacity, and phone battery capacity. Most cellphone batteries are in the 3000mAh neighborhood in terms of capacity. Have a look at your cellphone’s specs to find out its capacity, most, if not all manufacturers will provide this number in mAh, which stands for milliamp hours. The solar charger you purchase will usually give the battery capacity in mAh for their product since the intended use is for small scale electronic devices. For example, if your phone’s battery is 3000mAh and the charger battery is 6000mAh, this means you can fully charge your phone twice(6000mAh / 3000mAh = 2) The charging time will vary depending on your phone’s charging capability, and the output amperage of the charger battery. In this case, assuming your phone can handle the Amperage, a 3A output current will charge your phone faster than a 2A output current. Finally, we must consider the output power of the solar panel itself. Knowing the battery capacity of the charger allows you to look at similar sized batteries and factor in the power of the panel. The higher the wattage of the panel, the better it can charge batteries. If it comes down to two chargers with the same battery capacity, choose the one with the better solar panel.
The QuadraPro Solar Power Bank is a great little charger perfect for camping and other outdoor activities. It has a 6500mAh battery capable of charging most phones at least twice from empty. The charger uses a fold out design to maximize the available surface area for the panel. This gives the solar panel a 5.5W power output in ideal conditions. It is water resistant, comes with a built-in light, and in addition to solar charging, the device has charging capability by plugging into your wall socket at home. Also included is 2 USB outputs giving you the ability to charge two devices at once, and there is wireless charging for supported devices. There are also built in loops and carabiners, giving you more flexibility when out on trips.
When portable solar power is needed for heavy usage such as boats, RV’s or cabins, a larger solar panel is necessary. Thankfully, finding a portable solar panel capable of powering your RV or camp is easy and affordable. Depending on the type of set up you have, whether it’s a single 12v hooked up to an inverter, or a battery bank, the size of the solar panel will dictate how fast you can charge those batteries. You would have to do a little research on how much power you need out of a solar panel depending on how many batteries you must charge, and how fast you need them charged. You must also consider location and how many hours of sunlight you expect on a day to day basis.
Figure 5: Goal Zero Boulder 200
The Goal Zero Boulder 200 is a portable, outdoor ready solar panel. It is a 200W folding panel with angle adjustment capability. The great thing about the Boulder 200 is their specs are straight forward and buying the right panel is made easy. Everything becomes clear when you use real world examples. The Yeti 1000 is a 1045Wh power station. It is basically a proprietary battery with a built-in inverter. We’re more interested in what you can do with such a device, and if the solar panel you intend to buy is enough for that application. Going off the information on Goal Zero’s website, a 1045Wh power station can power a refrigerator for 17+ hours, which kind of gives an estimate on how much other things you can run simultaneously. Furthermore, the site claims that the Yeti 1000 will charge in 10-20 hours of sunlight using a single Boulder 200 solar panel. Knowing how fast you deplete a battery on any given day will help you decide how fast you need to charge the batteries daily. Ideally one could buy enough solar panels to keep the batteries full all day every day with usage. That is not practical for most people and so they buy solar panels to charge their batteries when they are not using them for power. I would say that a 200W panel can power most RVs for a long weekend and will charge the batteries during the weekdays when the RV is not in use.
There are so many resources available to get people on board with solar energy. Outdoor activities benefit the most from solar energy because solar does not have the same prerequisite electrical infrastructure to get hooked up with electricity. The current efficiency of solar panels allows them to be extremely portable and applicable for any off-grid situation. I myself would use a 50W panel to charge my trolling motor batteries when I’m done fishing. Right now, I store my boat at the lake an hour away from my house. I don’t have electrical hookup at the boat, so I must lug my batteries home after every trip to charge them. If I had a solar panel, I could leave it hooked up to the boat and it would charge my batteries during the week.
Written by John Sader
From camping shoreside as a toddler while his father fished well into the night, to portaging through the backwoods of Ontario, John is an outdoorsman in every sense of the word. A natural Jack-of-all- trades, he is always outdoors doing anything and everything. John enjoys spending his weekends fishing, from a boat or through the ice, hunting for Turkeys and mushrooms in the spring, wing shooting in the fall and chasing deer until the last day of the season. He one day hopes to have his own homestead where he can enjoy the outdoors to it’s full potential. Follow along on his journey on Instagram @set_hook.