Solar Electric

Photovoltaic (PV) systems are solar electric systems that produce electricity directly from sunlight. PV systems produce clean, reliable energy which can be used in a wide variety of applications. You are likely familiar with the small PV modules which have been used in solar watches and calculators since the 1970’s. Whether your goal is to reduce your carbon footprint, lower or eliminate your electric bill, charge batteries in remote areas, or power your lap-top at the beach, it can be done with today’s PV systems.

How Does It Work?

Solar cells, the basic building blocks of a PV system electric system roof top of semi-conductor materials. When a photon of sunlight strikes these materials, the solar energy knocks electrons loose from their atoms. This phenomenon is called the “photoelectric effect.” The free electrons then travel through a circuit built into the solar cell to form an electrical current. Only sunlight of certain wavelengths will work efficiently to create electricity. PV systems can produce energy on cloudy days, but not as much as on sunny days.

The basic PV solar cell typically only produces a small amount of power. To produce more power, solar cells can be interconnected to form panels or modules. The output of a typical solar panel is 80 to 240 watts. To make more power, panels are then connected in groups called an array. PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a pole with a tracking device that follows the sun, allowing them to capture more sunlight over the course of a day. Because of their modularity, the professional system designers on our Prudent Living team can design a system to meet any electrical demand, no matter how large or small.

What Is Included In A PV System?

In addition to solar panels, a small solar electric system consists of other parts called, balance-of-system components. Some of these components are: mounting racks for the panels, wiring, inverter (to electrical current from direct to alternating), batteries, and a stand-by generator. The balance-of-system components required will depend on the type of system being used.

The simplest PV system is known as a grid-connected system. A grid-connected PV system receives back up power from a utility’s grid when the PV system is not producing enough power. When the system produces excess power, the utility will purchase the power through a net-metering agreement. Under this arrangement, your electric meter will spin forward when you are using more power than you are generating, and spin backward when you are making more power than you are using. You are only billed for the difference, or the net power, used. The basic components of a grid connected, net metered PV system are shown in the illustration below.

A stand alone electric PV system is designed to operate independently of the electrical grid, or off-grid. These systems are primarily used in remote locations where it is more cost effective than extending the power line to the grid. In addition to the PV panels and inverter(s), a typical stand alone PV system will also include batteries to store electricity for periods when the sun is not shining, components to control the charging of the batteries, and a back-up generator of some kind to provide power during extended periods of cloudy weather.

A third type of system is the hybrid electrical system which combines wind or micro-hydro power with solar technologies. The hybrid system offers several advantages over either single system and are generally designed so that the technologies compliment each other, in order to accommodate seasonal climate variations.

Is Solar Electric Right for Me?

A proper evaluation of your site is vital to determine whether solar electric is right for you and to ensure that your system will perform as expected. The amount of electricity generated at a particular site depends on how much of the sun’s energy reaches it. Some questions you will want to consider are:

Do you have clear and unobstructed access to sunlight for all or most of the day, throughout the year? Even partial shading of a solar array will substantially lower system output. Is your roof orientated toward the south, and is it large enough to accommodate a solar array? Pole mounted arrays are an option, but will significantly increase the cost of the system.