A PV solar panel, referred to in the industry as a solar module, is constructed by connecting photovoltaic cells (or PV cells) to produce electricity. The cells are a semiconductor-based technology that converts solar radiation into direct current (DC) electricity. Solar panels for grid-connected home or business use typically use 60 or 72 PV cells.
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By utilizing PV solar cells, home or business owners are able to generate electricity from sunlight, saving money and avoiding the harmful pollution generated by traditional methods of generating electricity. This solar generated energy is used to offset or replace power that would normally be purchased from the utility.
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Net metering is a useful tool in the field of alternative energy. For owners of PV systems, net metering provides an opportunity to sell excess electricity produced to your local utility company. In North America, forty states currently have net metering policies in place. Net metering means that the amount of solar electricity produced (measured in KWh) is subtracted from your overall usage, meaning you only pay the utility for the difference (the “net” amount).
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The requirements vary depending on the size of the system and the particular state and/or utility. In some states a special meter must be obtained from the power company. Information can be found here:
http://www.seia.org/cs/federal_issues/net_metering
http://www.dsireusa.org/
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98% of PV solar panels installed in the USA are grid-tied systems, meaning that the system is tied to the power grid (local electric power utility company). The solar power is added to the grid power, reducing the amount of power that must be purchased from the utility.
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An off-grid solar energy system is where there is no connection to the utility company power grid. This type of installation requires a charge-controller, a bank of batteries and in most cases an inverter, so that electric power requir
ements can be met at night or during cloudy conditions.
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Currently, the Federal government gives a personal or business tax credit of 30% of the cost of a PV system. Many states also offer additional incentives for utilizing PV solar products.
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There are currently four main types of solar PV panels:
1. Monocyrstalline - these are made from cells created by cutting thin slices from single crystal silicon block and are higher in efficiency, but also higher in cost per watt. They are easy to spot because they have a smooth even color, usually black.
2. Polycrystalline – these are made from cells created by cutting thin slices from polycrystal silicon block and are slightly lower in efficiency, but also lower in cost per watt. Polycrystal silicon is the “chicken nugget” of silicon, made by combining many individual crystals. They are easy to spot because they have an uneven color, usually blue.
3. Multicrystalline – a different term for polycrystalline.
4. Thin film – these are made by depositing a thin layer of very finely powdered silicon (amorphous silicon) or other photovoltaic material on a substrate. These are much lower in efficiency that crystalline cells, and somewhat cheaper per watt. They are a good choice for large ground mounted utility scale solar arrays where real estate is plentiful. Their low efficiency makes them undesirable for commercial and residential applications because they consume a large amount of roof space compared to mono or poly panels.
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PV panels installed in the USA must be tested to UL 1703 standard and in California, also to IEC 61730. They can be tested and certified by any NRTL (nationally recognized testing laboratory) like UL, CSA, ETL, TUV etc. For consumer purposes, the main rating to consider is the watts rating, which is expressed at watts-peak (Wp) which is the amount of peak power produced under STC (standard test conditions).
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STC is the main set of conditions used in testing solar PV modules. Conditions are considered standard when cell temperature is 25°C and you have 1000 W/m^2 of direct insolation. STC also assumes a panel is oriented to the proper angle and elevation.
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Each system will produce a different amount of power based on the system size, orientation, insolation, etc. A quick, free telephone or email consultation with our sales team will help you be able make a good estimate of your potential. Just give us a call.
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Solar panels can be installed on the roof, on the side of a building, on the ground or on a pole. The most cost effective installation will usually be on a roof, but if roof or shading conditions prevent the use of the roof we can help you review other options.
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PV solar panels will generally produce electricity at a reduced rate under cloudy conditions. Severe clouds will interrupt the production of power.
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Solar panels are known to last 40 years or longer.
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For a grid-tied system where no batteries need be replaced, there is typically little or no maintenance required. You might consider a periodic inspection to ensure that the panels remain clear of leaves, dirt, bird droppings etc. Other than that, unless there is an equipment failure there should be no maintenance required.
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Not in a normal grid-tied PV solar installation. In a grid-tied system, the inverter will shut off if the power company grid is not also providing or able to provide power. This is more of a safety feature than a technical limitation. To have a back-up battery system, you would need to take the same steps as if there were no solar involved, i.e., install some type of UPS system. Another approach would be to install a hybrid on/off-grid system through the use of a special charger-inverter and batteries.
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Typically the best return on investment is when you target the average power in watts used during the month with the lowest electric bill. Most net metering programs do not let you carry forward a credit, meaning that when you produce more solar electricity than your total consumption, it is wasted. Actually it is not wasted, it is just given free to the power company who will sell it to someone else ;-) (Some utilities offer a program where they pay the customer for surplus electricity on the account at the end of the year...APS is one of them that does this.)
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