Shortcuts: Solar Panel Kits | Running on Solar vs. Charging with Solar | What are Photovoltaics?
Solar Panel Kits
For those interested in making electricity from the sun, but don’t know where to start: there are a number of solar kits available that includes everything you need, including solar panels of varying sizes, battery packs, charging cables, and sometimes even things like power inverters and LED lights.
Because the amount of power that can be generated by a solar panel is partially dependent upon the size of the solar panel, consumers will find that larger panels and larger batteries cost more money. The smallest capacity batteries, suitable for small mobile devices, can be found for around $20. Meanwhile, the highest capacity batteries can be upwards of $1500 or more. These high capacity kits, such as the Goal Zero Yeti 1400, are well-suited to keeping larger devices and refrigerators running during power outages.
Similarly, a small solar panel for smaller capacity batteries or mobile devices will start at around $50 – such as the Suaoki 25W solar panel charger, which is packable and provides plenty of power for charging your smartphone while out hiking.
Higher capacity (and much larger surface area) panels well into the $300-$500 range. Although technology in the field continues to allow for smaller panels and batteries with increased efficiency, even the most efficient solar panels will be less than 50% efficient regarding the amount of power produced, and the most efficient batteries will still hold a only limited amount of charge before becoming too heavy and too costly to fit the term “portable”.
The amount of time required to charge a portable generator battery will vary greatly between different brands. This number is fully dependent on several variables, including the efficiency and size of the solar panels and the size of the batteries. A consumer’s best bet when purchasing a portable solar powered generator is to try to match the solar panel size with the generator battery size, using the makers’ guided instructions.
Many companies selling portable solar powered generators will sell a variety of solar panels and generator batteries. These can range from small, pocket-sized batteries and panels that can fold up easily into a backpack, to much larger and heavier batteries that weigh over 30 lbs., with panels that can weigh over 20 lbs. The larger the capacity, the less “portable” some of these kits will be, making many of them equivalent to a fuel-powered generator regarding weight.
However, portable solar powered generators are beginning to compete with fuel-based generators in some applications. A high capacity generator kit can come with photovoltaic solar panels with a 90W rating, and generator batteries with a 12000Wh rating. This is enough battery power to run a 16 cubic foot refrigerator for a whole day, perfect for the occasional and unexpected power outage. As with fuel-based portable generators, the higher the capacity of the unit, the more it will cost.
Consumers should be aware that a solar powered generator would need to be charged well ahead of time in order to function with higher capacity devices. While some higher-end, higher-capacity solar panels can run a device on their wattage alone, most devices cannot. Even a high-capacity panel, such as a 90W panel, could take anywhere between 30-50 hours to charge a 1200Wh generator battery. As such, portable solar powered generators will provide the cheapest, quietest emergency power generation, but are best utilized in over smaller periods of time, and with much forethought.
Running on Solar vs. Charging with Solar
Functionally, solar powered generators operate as one large battery. While fuel-powered portable generators operate with some form of engine, producing power continually (as long the fuel source does not run out), solar powered generators convert sunlight into usable electricity, which is then stored in the portable generator’s batteries. A solar powered generator can be used to power anything from a cell phone to a refrigerator. What you can practically provide power for will depend on both the size of the battery and the size of the generator battery.
Those interested in purchasing a solar powered generator should first and foremost be aware of the time required to charge the generator battery. Although some generators can still charge via photovoltaic solar panels under cloudy conditions, the charge time for a small generator battery (around 11-12Wh) with a small solar panel (around 7W) could be around 4-5 hours with good light conditions.
Solar panels are measured in how many watts they are able to continuously produce as they absorb sunlight. A small solar panel measured in 7 watts means that the panel will produce 7 watts of power for each hour of peak sunlight. This is generally enough wattage to charge a cell phone or other small mobile device, but not enough to charge a device that requires more power.
In order to charge a device with a battery, the solar panels must produce more continuous energy than the device uses. This is simple enough if the device is off. However, if the device is running, the amount of continuous wattage required will go up. For comparison, a typical iPhone charger will produce 5 watts of power. This is enough to charge an iPhone while it is running. However, a typical iPad charger produces 12 watts. If a consumer is attempting to charge a device directly from a small sized, small capacity solar panel, the results will be underwhelming, to say the least.
The larger the solar panel capacity, the larger the solar panels will be. Likewise, the larger the portable generator batteries, the longer it will take to charge the batteries. This is also why larger portable generator batteries require larger solar panels with a higher wattage. The batteries will begin to lose their charge very slowly, even with nothing plugged into them. If the solar panel produces too little wattage, it simply will not charge the battery. Alternatively, if the solar panels produce too much wattage (something that cannot be controlled by any means other than covering up part of the panels), then the generator batteries will not be able to handle the amount of incoming electrical current.
What are Photovoltaics (PV)?
Photovoltaic panels being installed on the roof of a house.
Image courtesy of Jon Callas
In modern times, there are two primary ways in which solar energy is utilized to create electrical power: photovoltaics (PV) and concentrated solar power (CSP).
Photovoltaics are the primary source of solar electric power generation in the world, accounting for 1% of total (from all sources) worldwide power generation, which works out to be nearly 200 gigawatts of power. Since the discovery of the photovoltaic effect, many different materials have been discovered that produce electrical current directly from the sun’s rays.
How do Photovoltaic Cells Make Electricity?
Plainly speaking, the sun bathes the Earth (and everything around it) in endless waves of photons. While these photons are, for the most part, harmless purveyors bringing us light and heat, they can also interact with different materials, causing the electrons in those materials to become more active and produce energy in the form of electrical current.
Unlike concentrated solar power, which requires the heat energy of the sun to create chemical reactions (primarily steam), photovoltaics are able to create electrical power directly, no moving parts required. This is why photovoltaics account for a much larger share of solar energy production, and why photovoltaics are behind only wind and water for renewable energy sources.
The popularity of photovoltaics is in their light weight, portability, foldability, and increasingly lower cost. However, the largest concern and current focus for photovoltaic solar cells is in their efficiency. A solar cell’s efficiency is measured in how much sunlight can be converted into usable energy – without losing energy before conversion to direct electrical current (DC) and further conversion from direct current to usable alternating current (AC). While the most efficient solar panels created are just over 40% efficient, these higher efficiencies are not necessarily the most useful for consumers. Indeed, the higher efficiency panels are currently much more expensive, making them less desirable for consumer purposes. The balance between efficiency and cost exists somewhere between conversion rates of 12-20%.
Solar powered generators will always run using photovoltaic solar cells with varying efficiencies. Because the technology for these types of generators is still fairly new, their power output tends to be much smaller. Likewise, a solar powered generator will take much more time to produce power than a generator running off of a combustible fuel, such as gasoline, diesel or propane. However, a solar-based system will have distinct advantages over those powered with combustible fuels.
