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Green Energy Glossary
AC (Alternating Current) Allows for two way electricity flow from your local utility provider in order to power appliances in your home. The energy flowing form a solar PV system is DC and needs to be converted into AC to be used in a house.
AIR CHANGES PER HOUR The air tightness of a house- the number of times the home’s air is replaced by outside air in an hour caused by leaks in the duct system or cracks in the building shell.
AIR SEALING The process of sealing penetrations in the building shell, walls, floors and ceilings where outside air enters the building. Also known as Envelop Sealing
AMORPHOUS A type of solar panel which is the least expensive to produce but also the least efficient panel.
AMPERE (amp) A unit of electrical current or rate of flow of electrons. One volt across one ohm of resistance causes a current flow of one ampere.
ANNUAL FUEL UTILIZATION EFFICIENCY (AFUE) The thermal efficiency measure of combustible equipment (furnaces, boilers and water heaters). It is usually expressed as a percentage- the higher the percentage the more efficient the appliance is. It is used by Energy Star to rate appliances.
ARRAY Any number of Photovoltaic (PV) modules connected together electrically to provide a single electrical output. An array is an integrated assembly of modules or panels together with support structure (including foundation) to form a free-standing field installed unit that produces DC power.
AZIMUTH The azimuth is calculated in order to determine solar capability. It is most often defined as the angle from due north in a clockwise direction. The preferred azimuth for a solar system is due south, or 180 degrees.
CELL (battery) A single unit of an electrochemical device capable of producing direct voltage by converting chemical energy into electrical energy. A battery usually consists of several cells electrically connected together to produce higher voltages. (Sometimes the terms cell and battery are used interchangeably).
CELL (solar) The smallest, basic Photovoltaic device that generates electricity when exposed to light.
DC (Direct Current) A one way flow of electric current. This is the flow produced by a solar system. In order to be used in a home it must be converted to AC. See definition for INVERTER.
DUCT BLOWER Fans that test leakage in duct system. Maximum leakage should be below 15%.
FUEL CELLS One or more cells capable of generating an electrical current by converting the chemical energy of a fuel directly into electrical energy. A fuel cell uses hydrogen and oxygen to produce electricity, with water and heat as its only waste product. Fuel cells differ from conventional electrical cells in that the active materials such as fuel and oxygen are not contained within the cell but are supplied from outside.
EFFICIENCY The ratio of power output of a Photovoltaic cell to the incident power from the sun.
ELECTRIC CURRENT The rate at which electricity flows through an electrical conductor, usually measured in amperes (amps).
ENERGY STAR An international standard for energy efficient consumer products, used by the EPA and the Department of Energy to rate appliances, fixtures and other products.
GREENHOUSE GAS EMISSIONS Gases that trap heat in the atmosphere. Some greenhouse gases occur naturally while others are created and released solely by human activities. Using a Photovolatic system reduces the greenhouse gases your house emits.
GREEN ENERGY Sustainable energy is the sustainable provision of energy that meets the needs of the present without compromising the ability of future generations to meet their needs. Technologies that promote sustainable energy include renewable energy sources, such as hydroelectricity, solar energy, wind energy, wave power, geothermal energy, and tidal power, and also technologies designed to improve energy efficiency.
GRID Transmission line network used to distribute electric power. In Sonoma County (except Healdsburg) PG&E is our network used to deliver power.
GRID-TIED SYSTEM – Connecting your solar system directly with your electricity provider. This system allows your house to pull power from the grid when not enough power is being generated from your solar system (i.e at night etc). It also allows you to sell your excess energy back to PG&E when you produce more electricity than your house needs.
HEAT PUMP An air-source heat pump is the most common type of heat pump. The heat pump absorbs heat from the outside air and transfers the heat to the space to be heated. Air source heat pumps lose efficiency in freezing temperatures and are therefore best used in warm climates. In the cooling mode the heat pump absorbs heat from the space to be cooled and rejects the heat to the outside air.
HYBRID (Cogeneration) SYSTEM A power system consisting of two or more power generating subsystems (i.e ., the combination of a photovoltaic system and a solar thermal system.)
INCENTIVES As it pertains to a photovoltaic system, financial assistance given by the government to assist properties in the cost of a PV system.
INVERTER A device that converts electricity from DC to AC. All grid tied PV systems use an inverter because houses can only use AC current.
KILOWATT-HOUR Unit of energy used to perform work (energy and work are equivalent in units, energy being the potential value and work the achieved value). This is the billing unit for PG&E.
LOAD Refers to equipment that is powered by electricity. Usually expressed in terms of amperes or watts. In an electrical circuit, any devise or appliance that uses power (such as a light bulb or water pump).
LOADING ORDER Priority order of least expensive upgrades to most expensive upgrades for your home. Reduce your energy usage before you produce power through solar.
LOW E WINDOWS A metallic, invisible coating on windows to reduce the amount of heat transferred between the glass- from the outside the window to inside.
MICRO-INVERTER Small inverters attached to each solar module, as opposed to one large inverter for the whole system. This reduces problems with system failure due to shading.
MODULE The smallest non divisible, self-contained which interconnects Photovoltaic cells and provides a single DC output.
MONOCRYSTALLINE A type of solar panel which is usually more expensive because it is made of one crystal, not multiple crystals fused together. These types of panels suffer from decreased output at 115 degrees F or higher. If space is a concern this type of panel offers a good size/power generation ratio.
NET METERING Arrangement that permits a facility (using a meter that reads inflows and outflows of electricity) to sell any excess power it generates over its load requirement back to the electrical grid to offset consumption. (See grid- tied)
NET ZERO General term applied to a building's use with zero net energy consumption and zero carbon emissions annually.
OFF-GRID Living in a self-sufficient manner without reliance on a public utility. A true off the grid house operates independently of a utility- no electrical, or water service.
PANEL A collection of one or more modules fastened together into a single unit, often factory pre-assembled and wired, forming a field-installable unit.
PEAK LOAD The highest electrical demand within a particular period of time. PG&E’s peak load is from 1pm to 7pm (summer), and 5pm to 8pm (winter), if you are on a Time of Use rate schedule.
PHANTOM LOAD Electric power consumed by appliances when they are switched off or are in standby mode. This especially applies to appliances with a remote like a TV or MP3 player.
POLYCRYSTALLINE A type of solar panel which is less expensive to produce but slightly less efficient because it is made of several blocks of crystals, not one sheet of crystals like monocrystalline panels.
POWER The rate at which energy is generated or consumed.
PV (PHOTOVOLTAIC) CELL A device composed of specially prepared semiconductor material or material combinations exhibiting the ability to convert incident solar energy directly into electrical energy.
R-VALUE Measure an insulation’s resistance to heat flow. The higher the R-value the better insulated your house will be.
RAFTER A type of beam which supports the roof of a building. Solar array racks are bolted into the rafters for support of the system.
REBATES Amount paid by way of reduction, return, or refund on what has already been paid or contributed.
RENEWABLE ENERGY Flows of energy that are regenerative or virtually inexhaustible. Most commonly includes solar (electric and thermal), biomass, geothermal, wind, tidal, wave, and hydro power sources.
SILICON A non-metallic element, that when specially treated, is sensitive to light and capable of transforming light into electricity. Silicon is the raw material used to manufacture most photovoltaic cells.
SOLAR PANEL A collection of solar modules connected in a series, to provide greater power than can be furnished by a single solar module. Solar panels can be provided to supply any desired voltage, current, or power.. Larger collections of solar panels are usually called solar arrays.
TILT ANGLE A fixed angle measured from the horizontal to which a solar array is tilted. The tilt angle is chosen to maximize the power generated. Depending upon latitude, season and time of day this angle will vary. Also referred to as pitch.
TIME OF USE A type of rate schedule where a customer is charged more to use energy during the hours of 1pm to 7pm (summer) and 5pm to 8pm (winter). This rate schedule is helpful if you can reduce your usage during the peak load hours and use more energy during off peak hours because the off peak hours are less expensive. Customers with solar systems are often encouraged to use this rate schedule since they are most likely producing energy during the peak hours and will not need to pull from the grid during this time.
VOLTAGE A measure of the force or "push" given the electrons in an electrical circuit; a measure of electrical potential.
WATT Unit of power. Power is the rate of using energy to do work.
WEATHERIZATION Modifying a building to conserve energy. These measures often include door weather stripping, gaskets, and caulking windows etc.