Glossary

Alternative Energy
The use of energy produced using non-carbon resources e.g. solar, wind, water, thermal.

Biomass
This is the organic materials produced by plants and trees. The term ‘biomass’ is intended to refer to materials that do not go directly into foods or consumer products, but may have alternative industrial uses. Common sources of biomass are (1) agricultural wastes eg straw and manure from cattle, poultry etc (2) wood materials, e.g. wood, bark, sawdust, mill scrap; (3) municipal waste such as, waste paper (4) energy crops, such as  poplar and willow.

Biofuel
This is any fuel derived from biomass. It is a renewable energy source, unlike petroleum, coal and nuclear fuels. The energy of the sun during the growth of plants, is ‘captured’ through the process of photosynthesis. A common biofuel is biodiesel which is used in vehicles.  Biofuels can be made from oil rich crops such as rapeseed, linseed etc. Some companies also make biodiesel from waste vegetable oil from restaurants and chip shops.

AC
Alternating Current The direction of electrical current reverses, usually many (60) times per second. Electricity transmission networks use AC because voltage can be controlled with relative ease.

Ampere or (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. One ampere is equal to 6.235 x 10 18
electrons per second passing a given point in a circuit.

Array
Any number of Photovoltaic modules connected together electrically to provide a single electrical output or system which produces DC power.

Cell - Solar
The smallest, basic Photovoltaic device that generates electricity when exposed to light.

Carbon Dioxide CO2
This is a colourless, odourless, tasteless gas, about 1.5 times heavy as air. The decay (slow oxidation) of all organic materials produces CO2.

Carbon Index
An addendum to the SAP rating, which measures the CO2 ‘created’ in use, expresses as a measure if the CO2/m² of floor area. One method of satisfying the building regulations re: thermal properties.

Carbon Neutral
A term used to describe a building design that consumes no fuels that will release carbon dioxide or that  uses renewable fuels as an energy sources to ensure that the total production of CO2 related to a building or project is zero.

Coefficient Performance (CoP)
An example of CoP; a geothermal heat pump, operating at CoP 3.5 is able to move 3.5kWh of heat for every 1 kWh it consumes. This can also be viewed as an efficiency of 135% which, compares very favourably to high efficiency (condensing) gas burning furnaces (90-99% efficient) and electrical heating (100%). The CoP of air source heat pump may be 2.0 (200% efficiency) at low outdoor temperatures before its backup electrical resistance heating coils are turned on.


DC Direct Current
A one way flow of electric current. Typical sources of direct currents are electric cells, rectified power units and direct current generators. This is the current flow produced by a solar system. To be used for typical 120 volt or 220 volt household appliances, it must be converted to AC (alternating current).

Efficiency
The ratio of power output of a Photovoltaic cell to the incident power from the sun or simulated sun sources under specified standard insolation conditions.

Electric Current
The rate at which electricity flows through an electrical conductor, usually measured in amperes (amps).

Electricity
Energy resulting from the flow of charge particles, such as electrons or ions.

Electrons
A negatively charged particle. The movement of electrons in an electrical
conductor constitutes an electric current.

Facade
The face of a building especially the principal face.

Future Proofing
To design in an ability to adapt to future trends, this maybe in the form of lifestyle trends or the availability of resources such as fuel.

Greenhouse Effect
A term used to describe the heating up of the earth by radiation from the sun being trapped with the atmosphere by atmospheric gases. These gases act as insulators preventing radiated heat from the warming of the earth from escaping to space. The gases are found naturally in the atmosphere but in recent decades, levels of some (carbon dioxide and methane in particular) have increased due to human activity.

Grid
Transmission line network used to distribute electric power.

Grid Connected System
A PV system that is connected to the national grids by an inverter. The inverter will export unused electricity to the grid earning the user money. A Grid Connected PV system usually is made from Photovoltaic Modules and a Grid Connected Inverter.

Heat Recovery
The use of heat exchangers to extract heat from waste air or water, and transfer it into an incoming air supply.

Inverter
A device that converts electricity from DC to AC.

kWh
Unit of energy used to perform work (energy and work are equivalent in units, energy being the potential value and work the achieved value).

Thermal unit:
One kWh = 3400 BTU. Can be compared to 860 calories (food value).

kWp
Kilo   watt peak, maximum output under ideal conditions.

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).

Maximum Power
The power at the point on the current-voltage characteristic where the
product of current and voltage is a maximum (measured in watts).

Module
The smallest non divisible, self-contained and environmentally protected physical structure housing interconnected Photovoltaic cells and providing a single DC electrical output.

Off-Grid System
A system which operates independently of the utility lines. An off-grid system is made up from, PV Modules, Charge Controller, Battery Bank and an Inverter. It may draw additional power from a generator and is not capable of providing power to the utility.

Ozone
A colourless, toxic, unstable gas formed from oxygen and electrical discharge or ultra violet light. Ozone is a pollutant when it occurs at ground level usually as a result of high traffic concentrations. However, natural ozone at high levels in the atmosphere prevents harmful ultraviolet rays from reaching the surface of the earth.

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.

Passive
A building term describing a structure or component that needs no mechanical assistance to operate. For instance; passive solar design uses the structure of the building and it’s solar orientation to collect energy from the sun.

Passive Stack Ventilation
The use of building shape and design to produce sufficient natural ventilation without the use of electrically powered fans. Stack ventilation uses vertical ducts to simulate natural airflow due to the ‘flue’ effect.

Peak Watts
The measurement of electricity produced by a solar generator at noon on a sunny day, under predetermined standard conditions.

Photon
The actual (physical) particle unit of light, as the electron is of electric charge and the atom and molecule are of matter. Light has both wave properties and particle properties. Violet light has relatively short wavelength and higher energy in its photons; red light has longer wavelength, lower-energy photons. The wavelength and/or energy spectrum of the sun extends in both directions beyond the visible range of light, of course, and the silicon module solar cell can capture some energy in both of these invisible zones. Photons not captured by the cell are either reflected or converted to heat in the solar array.

Photovoltaic Cell - PV Cell
A device composed of specially prepared semiconductor material or material combinations exhibiting the ability to convert incident solar energy directly into electrical energy.

Photovoltaic Effect
The phenomenon that occurs when photons, the 'particles' in a beam of light, knock electrons loose from the atoms they strike. When this property of light is combined with the properties of semiconductors, electrons flow in one direction across a junction, setting up a voltage. With the addition of circuitry, current will flow and electric power will be available.

Photovoltaic System
An installed arrangement of solar modules and other equipment generating power for a given application.

Recycling
The reprocessing (breaking down and reforming) of an existing material to manufacture a new material for a new use.

Reuse or Reclaimed
The reuse of whole and intact building materials in their originally produced form. Often referred to as architectural salvage.

Renewable Resources
Materials or energy sources which can be replaces, hopefully within the lifetime of the product e.g. timber can be re-grown.

Renewables/Non-Renewables
Material from a source that is renewable (e.g. wood) versus that which is not or which has a finite non-renewable supply (e.g. fossil fuels).

Resource Depletion
The specification of certain materials, products or processes can lead to habitat damage, environmental degradation, and rarity e.g. fossil fuels, peat and Welsh slates.

SAP Rating
An energy rating system for housing which measures the energy cost in £/m² floor area. Now a pre-requisite for calculating the carbon index which is one method of satisfying the building regulations re thermal performance on housing and also for calculating solar pv energy generation.

Semiconductor
A material such as silicon, which has a crystalline structure that will allow current to flow under certain conditions. Semiconductors are usually less conductive than metals but not an insulator like rubber.

Silicon
A non-metallic element, that when specially treated, is sensitive to light and capable of transforming light into electricity. Silicon is the basic material of most beach sand, and is the raw material used to manufacture most photovoltaic cells.

Solar Cell
The basic photovoltaic device which generates electricity when exposed to sunlight.

Solar Panel
A collection of solar modules connected in series, in parallel, or in series-
parallel combination to provide greater voltage, current, or power than can be furnished by a single solar module. Solar panels can be provided to furnish any desired voltage, current, or power. They are made up as a complete assembly. Larger collections of solar panels are usually called solar arrays.

Stand Alone System
See Off-Grid System.

Storage Battery
A device capable of transforming energy from electric to chemical form and vice versa. The reactions are almost completely reversible. During discharge, chemical energy is converted to electric energy and is consumed in an external circuit or apparatus.

Tilt Angle
A fixed angle measured from the horizontal to which a solar array is tilted. The tilt angle is chosen to maximize the array output. Depending upon latitude, season and time of day this angle will vary.

Tracking Array
An array that is mounted on a movable structure that attempts to follow the path of the sun. Some tracking arrays are single axis while others are dual.

Voltage
A measure of the force or "push" given the electrons in an electrical circuit; a measure of electrical potential. One volt produces one amp of current when acting against a resistance of one ohm.

Water Conservation
The design of water usage and waste systems to minimise wastage, reduce flooding and un-necessary re-processing to ensure that an essential primary resource remains readily available.

Watt
Unit of power. Power is the rate of using energy to do work.