Image above shows a residential Grid-Connected Photovoltaic System.
1. solar panels 2. inverter 3. breaker box 4. home power and appliances
5. meter 6. utility power grid.
(1) Solar Electric or PV modules convert sunlight to electricity. The PV modules generate DC electricity - or direct current - sending it to the inverter. (2) The inverter transforms the DC power into AC electricity for ordinary household needs. (3) Existing electrical panel distributes solar electricity and utility power to (4) loads (appliances). For systems with a battery backup (optional), the inverter also regulates the charge of batteries. The electricity stored in the batteries can be used at night or during blackouts.
A valuable feature of photovoltaic systems is the ability to connect with the existing power grid which allows owners to sell excessive electricity back to the utility with a plan known as (5) Net Metering. At times when you are not using all of the electricity produced by your system, your meter will spin backwards selling the electricity back to the (6) utility power grid at retail rate.
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Systems are generally classified according to their functional and operational requirements, their component configuration, and how the equipment is connected to the other power sources and electrical loads (appliances).
Utility Intertie PV Systems (Grid-Connected)
Intertie systems use an inverter that converts the energy collected from the PV panels into conventional AC power and feeds it to your electrical circuit breaker panel. As long as there is enough electricity flowing in from your PV system, no electricity will flow in from the utility company. If your system is generating more power than you are using, the excess will flow back into the grid, turning your meter backwards. If you live in one of the majority States that allow Net Metering, then everything goes in and out through a single residential meter.
Grid-Connected System is the simplest and most cost effective way to connect PV modules to regular utility power. Grid-Connected systems can supply solar power to your home and use utility power as a backup. If utility power is reliable and well maintained in your area, and energy storage is not a priority, you don't necessarily need a battery. But if the utility power goes down, even if there is solar, the PV system will be off for the safety of the utility workers.
Grid-Connected System with Battery Backup can supply power 100% of the time: At night, on cloudy days and when the utility power is down. More Information
Both Stand-Alone and Intertie systems can operate with or without a battery. Batteries add a substantial amount of cost and maintenance to the system but it allows the systems to operate when there is no other energy input (at night, during cloudy days, or during utility power outages). Without a battery if there is no solar energy flowing in and your utility power goes down, so will your system.
Stand-Alone Solar Electric Systems
Stand-alone PV systems are designed to operate independent of the electric utility grid, and are generally designed and sized to supply certain DC and/or AC electrical loads. Stand-alone systems may be powered by a PV array only or may use utility power as a backup power source.
Stand-Alone System - Since there is no battery to store electrical energy, energy is used immediately. Common applications are direct power to DC loads, water pumping and telecommunications. With an inverter it can also power AC loads. This system only works when it's sunny.
Stand-Alone System with Battery Backup -Can supply power 100% of the time: At night, on cloudy days and when the utility power is down. Excellent for remote applications where utility grid is inaccessible; cabins, boats, RVs and for emergency backup systems. More Information
The size and type of the PV system that will meet your expectations depends on your individual needs, site location and climate. Please contact us and our engineers and consultants will gladly assist you.
PV Power generation systems are made up of interconnected components, each with a specific function. One of the major strengths of PV systems is modularity. As your needs grow, individual components can be replaced or added to provide increased capacity. The selected components will vary depending on the applications, what follows is a brief overview of the components of a typical Solar Electric PV system.
The solar array consists of PV modules which convert sunlight into electric energy. The modules are connected in series and/or parallel to provide the voltage and current levels needed. The array is usually mounted on a metal structure and tilted to face the sun. »More Information
An inverter is required when you want to power AC devices. The inverter converts the DC power, or direct current, from the solar array and batteries into AC power.
Although charge controllers can be purchased with many optional features, their main function is to maintain the batteries at the proper charge level and to protect them from overcharging.
The battery bank contains one or more deep-cycle batteries connected in series and/or parallel depending on the voltage and current capacity needed. The batteries store the power produced by the solar array and discharge it when you need it. »More Information
AC and DC loads
These are the appliances (such as lights or radios), and the components (such as water pumps and microwave repeaters), which consume the power generated by your PV array.
Balance of System
These components provide the interconnections and standard safety features required for any electrical power system. These include: array combiner box, properly sized cabling, fuses, switches, circuit breakers and meters.
In more than 35 states, customers who own PV systems can benefit from laws and regulations that require "net" electric meter reading. The customer is billed for the net electricity purchased from the utility over the entire billing period—that is, the difference between the electricity coming from the power grid and the electricity generated by the PV system. Through net metering, the customer obtains the full retail electricity rate—rather than the much lower wholesale rate—for kilowatt-hours of PV- produced electricity sent to the utility power grid. The benefits of net metering to consumers are especially significant in areas such as Hawaii and New York, which have high retail electric rates. Utilities also benefit because the solar-generated energy often coincides with their periods of "peak" demand for electricity.