Photovoltaic (PV) modules make electricity from sunlight, and are incredibly simple, effective, and durable. They sit in the sun and collect energy from the sun, with no moving parts. The power it collects can run your electrical appliances, charge your batteries, or make electricity to sell back to the utility grid.
A PV array is the energy collector and does so by the photovoltaic effect. When sunlight hits a PV cell, the cell absorbs some of the photons and the photons’ energy is transferred to an electron in the semiconductor material. This electron then becomes part of the electrical circuit.
Most PV cells fall into one of two basic categories: crystalline silicon or thin-film. Crystalline silicon modules can be made from either monocrystalline, multicrystalline, or ribbon silicon. Thin-film is a term for a range of different technologies, including amorphous silicon. Crystalline modules currently capture more than 80% of the solar marketplace.
To use the energy from the solar array, you will need other components, such as inverters, charge controllers and maybe batteries, which make up a solar-electric system. The components required are dependent on the system type you use. System types include:
A stand-alone home solar electric or PV system operates "off-grid" -- it isn't connected to a electricity distribution grid operated by a utility.
A stand-alone PV system makes sense if any of the following apply:
You live in a remote location where the system would be more cost effective than extending a power line to a grid.
You're considering a hybrid electric system -- one that uses both a PV system and a small wind electric system.
You need minimal amounts of power; e.g., irrigation control equipment and remote sensors.
These systems require a battery bank to store the solar electricity for use during nighttime or cloudy weather, a charge controller to protect the battery bank from overcharging, an inverter to convert the DC PV array power to AC household power.
This system combines the benefits of a grid tied system with the convenience of a battery backed, off the grid system. These systems are becoming very popular because they provide all the benefits of a grid tied system and net metering. This smart system continues to generate power from the full solar array during a power outage unlike other systems that must shut down to prevent back feeding the commercial grid. The system requires the addition of a critical circuit panel to be used during outages. The smart inverter prioritizes the use of solar first to keep the batteries topped off and only uses the grid if necessary. During a grid failure, the system supplies power to the critical panel from the battery bank and solar array. This system would replace the typical propane backup generator.
A grid-connected home solar electric or 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 is required to purchase the power through a metering and rate arrangement.
Net metering is the best arrangement. Under this arrangement, the power provider essentially pays you retail price for the electricity you feed back into the grid.
Photovoltaic (PV) cells convert sunlight directly into electricity. PV cells are the solar cells that are often used to power calculators and watches. PV cells are made of semiconducting materials similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic effect.
One of the first things that most people ask about solar power is, "what size solar power system do I need to eliminate my power bill?"
Buying a solar energy system will likely increase your home’s value. A recent study found that solar panels are viewed as upgrades, just like a renovated kitchen or a finished basement, and home buyers across the country have been willing to pay a premium of about $15,000 for a home with an average-sized solar array. Additionally, there is evidence homes with solar panels sell faster than those without. In 2008, homes with energy efficient features and PV were found to sell faster than homes that consume more energy. Keep in mind, these studies focused on homeowner-owned solar arrays.
Since your solar panels generate DC (direct current), we need some kind of device to convert DC into AC (alternating current), in order to power your electrical appliances.. This is where the solar inverter comes in.
Craftsman Construction Is proud to announce it has forged a strategic alliance with Shenandoah Energy Services LLC (SES) to be our exclusive Solar Energy provider. Ed Kelly Principal at SES stated, “we are very happy to have forged an alliance with Craftsman Construction and are confident we can meet their level of quality expectations”. We feel Shenandoah Energy Services, LLC will bring great value to local homeowners in search of alternative energy for their homes.
This is a common question! On average, solar panels and the mounting equipment weigh 2-4 lbs per square foot, which is usually within the acceptable limits of your roof.
What do kWp and kWh mean? Watts are the units used to measure energy use or production and a kilowatt is a 1000 watts. kWp stands for kilowatt peak, which is the power that a solar panel will produce if it has ideal conditions.
Absolutely. The major contributor to global warming is the emissions of carbon dioxide from power stations burning fossil fuels. This is changing our climate and causing more severe weather patterns around the whole planet. Every time we use our electricity we are contributing to this massive problem. Everyone needs to do their bit!
When the grid power goes down, the grid-tied solar electric system goes down, too. This is to prevent any accidental back-feeding of solar electricity to the grid which might endanger line-workers. However, a new generation of battery backup technology is available, providing clean backup power in event of a power outage.
Every kilowatt of solar array takes about 75 square feet. So a typical 3kw array (twelve panels) will take a roof area about 11′ tall by 20′ wide (two rows of six).
This is a list of components that may be included in your PV system:
Solar panels/modules – The tools to collect the sun’s power and produce direct current (DC) power.
Inverter – Converts DC power into alternating current (AC) power, which we use in our homes. There are two types of inverters: central and micro.
Service/utility meter – This meter is a bidirectional smart meter that can keep track of any excess kWh production that you may send back to the grid.
Kilowatt-hour meter – This meter keeps track of the kilowatt-hours your system has produced since the system was turned on. Note: Not all systems have a kilowatt-hour meter installed.
AC disconnect - This is a device that the utility can use to turn off your PV system in an emergency or service situation. Note: Not all systems have an AC disconnect.
Conduit – Conduit is the housing for your PV system’s wiring. Conduit is usually rigid piping such as EMT (electrical metallic tubing), flexible aluminum or PVC (polyvinyl chloride).
At any time of the day, a customer's solar system may produce more or less electricity than they need for their home or business. When the system's production exceeds the customer demand, the excess energy generation automatically goes through the electric meter into the utility grid, running the meter backwards to credit the customer account. At other times of the day, the customer's electric demand may be higher than the renewable energy system is producing, and the customer relies on additional power needs from the utility. Switching between solar system's power and the utility grid power is instantaneous-customers never notice any interruption in the flow of power.
It’s important to minimize shading because solar panels operate at optimal output when their entire surface is fully exposed to direct sunlight. The system will still produce energy if it is shaded but its output will lessen.
A PV system that is designed, installed, and maintained well will operate for more than 30 years. The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years. The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly. Experience has shown that most problems occur because of poor or sloppy system installation.
The solar industry has a language all their own. Here is a list of terminology that will help you in your search to understand solar energy installation and cost.
Alternating Current (AC) - The flow of electricity that constantly changes direction between positive and negative sides. Almost all power produced by electric utilities in the United States moves in current that shifts direction at a rate of 60 times per second.
Ambient Temperature - The temperature of the surrounding area.
Amorphous Silicon - A thin-film, silicon photovoltaic cell having no crystalline structure. Manufactured by depositing layers of doped silicon on a substrate. See also single-crystal silicon an polycrystalline silicon.
Ampere (Amp) - The unit of measure that indicates how much electricity flows through a conductor. It is like using cubic feet per second to measure the flow of water. For example, a 1,200-watt, 120-volt hair dryer pulls 10 amperes of electric current (amps = watts/volts).
Ampere-Hour (Ah/AH) - A measure of the flow of current (in amperes) over one hour; used to measure battery capacity.
Annual Solar Savings - The annual solar savings of a solar building is the energy savings attributable to a solar feature relative to the energy requirements of a non-solar building.
Avoided Cost - The amount of money an electric utility would need to spend for the next increment of electric generation to produce or purchase.
Azimuth Angle - The angle between true south and the point on the horizon directly below the sun.
Battery - Batteries are often sold with a solar electric system. The primary purpose is to store the electricity not immediately used, which could be used at some later time.
BIPV (Building-Integrated Photovoltaic’s) - A term for the design and integration of photovoltaic (PV) technology into the building envelope, typically replacing conventional building materials. This integration may be in vertical facades, replacing view glass, spandrel glass, or other facade material; into semitransparent skylight systems; into roofing systems, replacing traditional roofing materials; into shading "eyebrows" over windows; or other building envelope systems.
Btu (British Thermal Unit) - The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit; equal to 252 calories.
Capacity Factor - The ratio of the average load on (or power output of) an electricity generating unit or system to the capacity rating of the unit or system over a specified period of time.
Circuit - One or more conductors through which electricity flows.
Concentrator - A photovoltaic module, which includes optical components such as lenses (Fresnel lens) to direct and concentrate sunlight onto a solar cell of smaller area. Most concentrator arrays must directly face or track the sun. They can increase the power flux of sunlight hundreds of times.
Converter - An electrical apparatus that changes the quantity or quality of electrical energy.
Crystalline Silicon - A type of photovoltaic cell made from a slice of single-crystal silicon or polycrystalline silicon.
Customer Load - The amount of power your site uses. Load may be expressed in kilowatts (capacity) or kilowatt-hours (energy). A site's peak kilowatts generally refers to when electric demand requirements are highest.
Demand - The level at which electricity is delivered to end-users at a given point in time. Electric demand in measured in kilowatts.
Direct Current (DC) - The flow of electricity that flows continuously in one direction. Frequency - The number of cycles through which an alternating current moves in each second. Standard electric utility frequency in the United States is 60 cycles per second, or 60 Hertz (Hz).
Electrical Grid - The electricity transmission and distribution system that links power plants to customers through high-power transmission line service.
Energy - The capability of doing work; different forms of energy can be converted to other forms, but the total amount of energy remains the same.
Energy Audit - A survey that shows how much energy used in a home, which helps find ways to use less energy.
Fixed Tilt Array - A photovoltaic array set in at a fixed angle with respect to horizontal.
Grid-Connected System - a solar electric or photovoltaic (PV) system, in which the PV array acts like a central generating plant, supplying power to the grid.
Hertz - The unit of electromagnetic frequency that is equal to one cycle per second.
Interconnection - The linkage of transmission lines between two utilities, or between a utility and an end-user, enabling power to be moved in either direction.
Insolation - The solar power density incident on a surface of stated area and orientation. It is commonly expressed as average irradiance in watts per square meter (W/m2) or kilowatt-hours per square meter per day (kW·h/(m2·day)) (or hours/day). In the case of photovoltaics it is commonly measured as kWh/(kWp·y) (kilowatt hours per year per kilowatt peak rating)
Inverter - A device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid.
Irradiance - The direct, diffuse, and reflected solar radiation that strikes a surface. Usually expressed in kilowatts per square meter. Irradiance multiplied by time equals insolation.
Kilowatt (kW) - 1,000 watts. A unit of measure of the amount of electricity needed to operate given equipment. For example, a one kW system is enough power to illuminate 10 light bulbs at 100 watts each. (volts x amps = watts)
Kilowatt-hour (kWh) - The amount of kW produced over a period of time, or one kilowatt of electricity supplied for one hour. For example, a one kW system, if operating at full capacity for 5 hours will produce (or use) 5 kWh of electricity.
Maximum Power Point (MPP) - The point on the current-voltage (I-V) curve of a module under illumination, where the product of current and voltage is maximum. For a typical silicon cell, this is at about 0.45 volts.
Megawatt - One thousand kilowatts or one million watts. One megawatt is enough to power 1,000 average California homes. Meter - A device that measures levels and volumes of customer's electricity use.
Mounting Equipment - Equipment/apparatus used to fasten solar (PV) modules to the roof. Peak Load - The highest electrical demand within a particular period of time.
Multicrystalline - A semiconductor (photovoltaic) material composed of variously oriented, small, individual crystals. Sometimes referred to as polycrystalline or semicrystalline.
National Electrical Code (NEC) - Contains guidelines for all types of electrical installations. The 1984 and later editions of the NEC contain Article 690, "Solar Photovoltaic Systems" which should be followed when installing a PV system.
Net Metering - In the fall of 1998, New York State Governor George Pataki signed the Solar Choice Act, which requires all the investor owned electric utilities in NYS to allow residential customers to interconnect PV (solar electric) systems to the utility's distribution systems. These grid-connected PV systems allow residential customers to run their electric meters backwards, offsetting their normal utility bill. Other than the renewable energy system, no special equipment is needed.
One-Axis Tracking - A system capable of rotating about one axis.
Orientation - Placement with respect to the cardinal directions, N, S, E, W; azimuth is the measure of orientation from north.
Peak Sun Hours - The equivalent number of hours per day when solar irradiance averages 1,000 w/m2. For example, six peak sun hours means that the energy received during total daylight hours equals the energy that would have been received had the irradiance for six hours been 1,000 w/m2.
Photovoltaic Cell or Module or Panel (PV) - A device that produces an electric reaction to light, thereby producing electricity.
Photovoltaic (PV) Array - An interconnected system of PV modules that function as a single electricity-producing unit. The modules are assembled as a discrete structure, with common support or mounting. In smaller systems, an array can consist of a single module.
Photovoltaic (PV) Conversion Efficiency - The ratio of the electric power produced by a photovoltaic device to the power of the sunlight incident on the device.
Polycrystalline Silicon - A material used to make photovoltaic cells, which consist of many crystals unlike single-crystal silicon.
Solar Energy - Heat and light radiated from the sun.
Solar Panel - Devices that collect energy from the sun (solar energy). This is usually solar photovoltaic (PV) modules that use solar cells to convert light from the sun into electricity, or solar thermal (heat) collectors that use the sun's energy to heat water or another fluid such as oil or antifreeze.
Solar Resource - The amount of solar insolation a site receives, usually measured in kWh/m2/day, which is equivalent to the number of peak sun hours.
Solar Thermal - The process of concentrating sunlight to create high temperatures that are needed to heat fluids, like water (solar hot water) or to vaporize fluid to drive a turbine for electric power generation.
Stand-Alone System - An autonomous or hybrid photovoltaic system not connected to a grid. May or may not have storage, but most stand-alone systems require batteries or some other form of storage.
Storage - Storage refers to saving surplus electricity produced by a photovoltaic (PV) system. Generally, batteries are used as storage devices.
String - A number of photovoltaic modules or panels interconnected electrically in series to produce the operating voltage required by the load.
Tracking Equipment - Structure that houses PV modules and that can automatically follow the sun across the sky throughout the day to maximize output.
Utility Grid - The interconnection of electricity generation plants through the transmission and distribution lines to customers. The grid also refers to the interconnection of utilities through the electric transmission and distribution systems.
Volt (V) - The amount of force required to drive a steady current of one ampere through a resistance of one ohm. Electrical systems of most homes and offices use 120 volts. (volts - watts/amps) (volts = amperes x resistance)
Watt (W) - Electric measurement of power at one point in time, as capacity or demand. For example, light bulbs are classified by wattage. (1,000 watts = 1 kilowatt).