How does solar panel work?

Solar photovoltaic (PV) panels are composed of solar cells that convert sunlight into direct current (DC) electricity. The DC electrical charge is then converted into alternating current (AC) electricity by a power inverter so that it can be used for your household electricity needs. Many cells are assembled to create a module (also called a panel), and many modules can be linked together to form a solar array.

What is a kilowatt (KW) ?

A kilowatt is a measure of electrical power that is equivalent to 1,000 watts. Kilowatts and watts both describe a rate of energy transfer; a watt is defined as one joule per second. Your electrical bill charges you for electricity in terms of kilowatt hours (kWh). One kilowatt-hour is a unit of energy that is equivalent to one kilowatt of power expended for one hour of time. For example, a hair dryer that is rated at 1,000 watts (1 kW) and operates for one hour will use one kilowatt-hour of energy.

What benefits does solar provide?

Solar is a fuel-free energy resource, which means it is an infinite and inexhaustible resource with no volatile fuel costs. Solar is also an emissions free energy resource that avoids polluting our air and water. After the up-front initial cost, solar provides immediate energy savings and greater energy stability. Solar also reduces line losses on the grid and provides energy to the grid during the daytime, when energy is most expensive and in high demand.

What are solar PV panels made of?

The majority of solar PV cells are made from crystalline silicon. Silicon is the second most common element in Earth’s crust (after oxygen) and, by mass, is the eighth most common element in the universe. In addition to crystalline silicon cells, solar panels can be made of cadmium telluride, copper indium gallium se lenide, gallium arsenide multijunction, thin film silicon, and other materials. The most com mon type of installation uses a flat-plate module which contains silicon cells encased in an encapsulant material for protection and sandwiched between a transparent glass or plastic cover and a metal, glass, or plastic backing to provide structural support. The entire module is usually encased in a metal frame.

How long do solar panels last?

Solar panels have an expected lifespan of at least 25 years (there are panels installed in the 1970s that are still generating power), and they are typically warranted for 25 years. They are generally made with tempered glass that is rated to withstand a direct vertical impact of a one-inch diameter hail stone traveling 50 miles per hour.

How much energy is used to make solar panels?

Most solar cells and modules are made of crystalline silicon, which uses wafers of purified silicon. Purifying and crystallizing silicon are the most energy-intensive parts of the manufacturing process, but other parts of the process that consume energy include cutting the silicon into wafers, processing the wafers into cells, assembling the cells into modules, encapsulating them in glass and frames, and the overhead energy used by manufacturing facilities. The PV industry generally uses “off-grade” silicon from the microelectronics industry that is then recrystallized. While producing energy with photovoltaic (PV) cells does not emit pollution or use energy resources, producing the panels themselves does consume energy, which, depending on the energy source, produces pollution and CO2 emissions. According to a 2004 National Renewable Energy Laboratory study that analyzes several different panel technologies, it takes 1 – 4 years for the energy savings accumulated by producing electricity from solar to equal the energy cost of producing the panel. Solar panels generally have life expectancies of 30 years, so 87% – 97% of the energy produced by the panels is clean energy (i.e. no pollution and/or greenhouse gas emissions). This 2004 NREL study assumes 1,700 kilo watt-hours per square meter of solar insolation.

What is the difference between an off-grid and grid-tied system?

A grid-tied system is a solar PV system connected to the utility grid, which allows homeowners to receive electricity from both the solar PV system and the utility. This type of system is made possible with a net metering arrangement with the utility (see above), which allows homeowners to receive fair credit for the electricity they produce. However, a grid-tied system will not continue to pro vide power during a utility power outage. Due to current regulations and equipment requirements, grid-tied solar PV systems are designed to shut off when any change to the in coming power source (from the utility) is detected. This is a safety measure. A grid-tied system can have power during blackouts with the use of battery backup systems. Systems with battery backups allow you to keep using electricity generated by your solar panels when the grid goes down (the electricity produced from the solar PV system is stored in the batteries, for later use). Battery backups are made up of banks of deep-cycle batters that are charged by both the panels on your roof and by the grid. Battery backups decrease the efficiency of your solar system overall because some of the power you generate must be diverted to charge and maintain the batteries. The batteries also have to be maintained and replaced periodically. The system and the batteries can be customized to cover a certain amount of electricity from key appliances it the home (i.e. refrigerator, lights, stove, etc); the system doesn’t need to be sized to cover the entirety of the home’s electricity usage (as the system is typically used for emergency back-up). However, battery backup systems are typically more costly than a standard grid-tied solar PV system. An off-grid solar system does not connect to the utility grid at all. As such, the solar PV system must be sized to cover the entirety of a homeowner’s electricity usage. Almost all off-grid systems require a backup energy source for times of high energy use or low solar production.

Can I install a battery to back up my solar system?

It is possible to have your house stay powered during blackouts, just as it is possible to take your house completely off of the grid. Systems with battery backups allow you to continue using the energy generated by your solar panels during a blackout, but they are more costly than a simpler system. Battery backups are made up of banks of deep-cycle batteries that are charged by both the panels on your roof and by the grid. Battery backups decrease the efficiency of your solar system overall because some of the power you generate must be diverted to charge and maintain the batteries. Batteries also must be maintained and replaced periodically, adding costs to
the system. They add significant complexity to the installation of the system and therefore add significant cost increases, but they are an option for those who are interested.

How will I know if solar can work for me?

Solar panels work best when they are installed facing south or west. If you have a large area of the roof that faces either south or west and does not receive significant amounts of shading, your home is probably suitable for rooftop solar panels. Fire code does mandate that there is a minimum distance between solar pan els and the edge of your roof for safety purposes, so you can not cover 100% of your roof space with solar panels. If you have a flat roof, or you do not have optimal roof space due to shading issues, you will either need to mount the solar panels on an angled rack or use a ground- or pole-mounted system located on an auxiliary structure (like a garage) or in a sunny part of your yard. If your roof is very steep, some contractors may charge an extra fee to install solar. Most buildings can accommodate rooftop solar installations, as long as you have some sunny, south- or west-facing roof space.

What solar system would work best for me?

The size of your system will depend on your current energy usage, the level of energy efficiency of your home or business, the available usable roof space, your budget and financing options, and the percentage of your energy consumption you want to offset with solar. It is recommended that you first take steps to make your home or business as efficient as possible before (or in conjunction with) making your solar investment.

How much does solar cost?

The cost of solar depends on the application, technology, size, and available residential and/or commercial incentives. Four factors that help keep solar costs low are economies of scale, competition in the marketplace, module and inverter prices (which fluctuate with supply and demand), and strong policies and programs to pro mote solar energy. The other important thing to remember is that solar is a fuel-free, clean, and inexhaustible resource that is not subject to fuel volatility, carbon risk, or limitations of fuel availability – solar provides price-stable and secure energy for decades to come.

Are financing options available for residential solar?

There are several financing options available to help homeowners defray the upfront cost of a solar installation.

What is the return on investment?

Unfortunately, this figure will vary widely is no easy answer to this question. The time it takes you to recover your investment will depend on the technology you select, your energy efficiency and usage habits, your current and future electricity rates, the system size and configuration, and available incentives. Depending on your usage and the size system you put in, you could see a return of 3-7% on your investment in the first year – a very good rate. Overall, your return on investment varies depend ing on how much electricity you use and what size system you install, however with current solar system costs, assuming you undersize your solar system and can take tax credits, most homeowners will recoup their upfront investment well before the 25-year life expectancy of the panel is reached. Solar is one of the few things consumers can purchase that does provide a financial return on their investment; imagine what the ROI would be for the car that you fill with gas every week! One of the biggest benefits of solar is the fact that it is an inexhaustible, clean, and price-stable resource that will last well over 20 years. Investing in solar today helps you mitigate future risks, fuel volatility, and uncertainty, while also improving your self-reliance and energy independence.

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