Solar Electric Systems

Photovoltaic (PV) systems are solar electric systems that produce electricity directly from sunlight.

PV systems produce clean, reliable energy that can be used in a wide variety of applications. You are likely familiar with the small PV modules which have been used in watches and calculators since the 1970’s. The products and systems offered by RES-TEC are simply a modern version of that same technology. Whether you 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, RES-TEC has the products you need.

How does it Work?

Solar cells, the basic building blocks of a PV system, consist 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.” These free electrons then travel through a circuit built into the solar cell to form an electrical current. Only sunlight of a 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 at RES-TEC 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 the solar panels, a small solar electric system consists of other parts called the balance-of-system components, such as mounting racks for the panels, wiring, inverter, batteries, and a stand-by generator.

The balance-of-system equipment required will depend on the type of system being used. Please visit our Electrical Components page for more information on these balance-of-system components.

The simplest photovoltaic 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 below. The following link has more detailed information and typical system components and costs of a RES-TEC Grid Inter-tied System.

A stand-alone electric PV system is designed to operate independent 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. The following link has more detailed information and typical system components and costs of a RES-TEC Off-Grid System.

A third type of system is called a hybrid electrical system, which combines wind or micro-hydro power with solar technologies. The hybrid system offers several advantages over either single system, and it is designed so that both systems complement each other through seasonal climate variations.

Is PV Right for Me?

A proper evaluation of your site is vital to ensuring 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.
  • What is your main reason for considering a solar PV system? Lowering electric bills? Reducing your environmental impact? Easing the demand on the electrical grid?

If you would like to explore your options further, Contact Us. We will schedule an appointment to visit your site in order to perform a thorough evaluation of your potential solar resource. The design team at RES-TEC will generate a basic system design, and provide a proposal showing the estimated system cost, expected annual system performance estimate, carbon foot-print reduction calculation, and system pay-back times. We provide this service at no charge to our valued customers and look forward to working together with you to bring more green energy to the Green Mountains!



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Renewable Energy Systems & Technologies

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