AKA: solar-electric modules, photovoltaic (PV) panels
PV panels are a solar-electric system’s defining component, where sunlight is used to make direct current (DC) electricity. Behind a PV panel’s shimmering facade, wafers of semiconductor material work their magic, using light (photons) to generate electricity— what’s known as the photovoltaic effect.
Other components in your system enable the electricity from your solar-electric panels to safely power your electric loads like lights, computers, and refrigerators. PV panels are assigned a rating in watts based
on the maximum power they can produce under ideal sun and temperature conditions.
You can use the rated output to help determine how many panels you’ll need to meet your electrical needs. Multiple modules combined together are called an array.
Although rigid panels are the most common form of solar electricity collector, PV technology also has been integrated into roofing shingles and tiles, and even peeland- stick laminates (for metal standing-seam
roofs).
PV modules are very durable and longlasting— most carry 25-year warranties. They can withstand severe weather, including extreme heat, cold, and hail stones.
Array Mounting Rack
AKA: mounts, racks
Mounting racks provide a secure platform on which to anchor your PV panels, keeping them fixed in place and oriented correctly. Panels can be mounted using one of three approaches: 1) on a rooftop; 2) atop a steel pole set in concrete; or 3) at ground level. The specific pieces, parts, and materials of your mounting device will vary considerably depending on which mounting method you choose.
Usually, arrays in urban or suburban areas are mounted on a home’s south-facing roof, parallel to the roof’s slope. This approach is sometimes considered most aesthetically pleasing, and may be required by local regulators or homeowner’s associations. In areas with a lot of space, pole- or ground-mounted arrays are another choice.
Mounting racks may incorporate other features, such as seasonal adjustability. The sun is higher in the sky during the summer and lower in the winter. Adjustable mounting racks enable you to set the angle of your PV
panels seasonally, keeping them aimed more directly at the sun.
Adjusting the tilt angle increases the system’s annual energy production by a few percent. The tilt of roofmounted arrays is rarely changed—adjusting the angle is inconvenient and sometimes dangerous, due to the array’s location.
Changing the tilt angle of pole- or ground-mounted arrays can be done quickly and safely. Pole-mounted PV arrays also can incorporate tracking devices that allow the array to automatically follow the sun across the sky from east to west each day. Tracked PV arrays can increase the system’s daily energy output by 25 to 40 percent.
Array DC Disconnect
AKA: PV di scon nect
The D C disconnect is used to safely interrupt the flow of electricity from the PV array. It’s an essential component when system maintenance or troubleshooting is required. T he disconnect enclosure houses an electrical switch rated for use in DC circuits. It also may integrate either circuit breakers or fuses, if needed.
Solar Charge Controller
AKA: controller, regulator
A charge controller’s primary function is to protect your battery bank from overcharging. It does this by monitoring the battery bank—when the bank is fully charged, the controller interrupts the flow of electricity from the PV panels.
Batteries are expensive and pretty particular about how they like to be treated. To maximize their life span, you’ll definitely want to avoid overcharging or undercharging them.
Most modern charge controllers incorporate maximum power point tracking (MPPT), which optimizes
the PV arra y’s output , incr easing the energy it produces. Some batterybased charge controllers
also include a low-voltage disconnect that prevents over discharging , which can permanently damage the battery bank.
Battery Bank
AKA: storage battery
Your PV panels will produce electricity whenever the sun shines on them. If your system is off-grid, you’ll need a battery bank—a group of batteries wired together—to store energy so you can have electricity
at night or on cloudy days. For off-grid systems, battery banks are typically sized to keep household electricity running for one to three cloudy days.
Gridintertied systems also can include battery banks to provide emergency backup power during blackouts— perfect for keeping critical electric loads operating until grid power is restored. Although similar to ordinary car batteries, the batteries used in solar-electric systems are specialized for the type of charging and discharging they’ll need to endure.
Lead-acid batteries are the most common battery used in solar-electric systems. Flooded leadacid batteries are usually the least expensive, but require adding distilled water occasionally to replenish water lost during the normal charging process.
Sealed absorbent glass mat (AGM) batteries are maintenance free and designed for grid-tied systems where the batteries are typically kept at a full state of charge. Gel-cell batteries can be a good choice to use in unheated spaces due to their freeze resistant qualities.
Inverter
Inverters transform the DC electricity produced by your PV modules into the alternating current (AC) electricity commonly used in most homes for powering lights, gadgets, and other appliances.
Grid-tied inverters synchronize the electricity they produce with the grid’s utility grade” AC electricity, allowing the system to feed solar-made electricity to the utility grid.
Most grid-tie inverters are designed to operate without batteries, but battery-based models also are available. Battery-based inverters for off-grid or grid-tie use often include a battery charger, which is capable
of charging a battery bank from either the grid or a backup generator during cloudy weather.
Most grid-intertie inverters can be installed outdoors (ideally, in the shade). Most off-grid inverters are not weatherproof and should be mounted indoors, close to the battery bank.
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