Alternating Current (AC)
Electricity that flows back and forth at a set frequency. AC is created by most power stations and transmitted through the electricity grid to power users. back to topBiomass
Organic material formed by living or recently dead plants. Biomass such as wood is a source of chemical potential energy. The chemical potential energy is the result of photosynthesis transforming the sun’s energy into a stored form. Biomass can be used as a fuel in power generation with less impact on global warming than burning fossil fuels. back to topCarbon cycle
One of the Earth’s most important cycles along with the water cycle. The carbon cycle exchanges and recycles carbon in its various forms (carbon dioxide, methane, biomass, coal, oil etc) between the reservoirs of oceans, atmosphere, land surface, earths crust, plants and animals. By burning fossil fuels long stored underground we are upsetting the balance of carbon dioxide in the atmosphere leading to Global Warming. back to topCarbon dioxide
Carbon dioxide (CO2) is a naturally occurring gas in the atmosphere. It is released into the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal), and wood and wood products are burned. For most countries carbon dioxide is the dominant greenhouse gas emission caused by human activities. In New Zealand, the greenhouse gas methane is also very significant because of the country’s extensive pastoral agriculture activities. back to topConduction band
The range of energy levels which an electron can exist in above the valence band, separated by a band-gap. Electrons within this energy range are free to move away from their parent atoms and are able to transport energy through the material. back to topClimate change
Climate change refers to the variation in the Earth’s global climate or in regional climates over time. It describes changes in the variability or average state of the atmosphere-or average weather-over time scales ranging from decades to millions of years. These changes may come from processes internal to the Earth, be driven by external forces (e.g. variations in sunlight intensity) or, most recently, be caused by human activities. back to topDiode
An electronic component formed by a p-type and an n-type semi-conductor placed in contact with each other to form a junction. The electric field created at the junction only allows negative or positive charges to flow in one direction. LEDs and photovoltaic cells are types of diode. back to topDoping
Doping is the process of adding small amounts of other elements into the crystal lattice of a pure element or compound to radically alter its electrical properties. Silicon, a Group IV element, is doped with Group III elements such as boron to form p-type silicon (see entry). When doped with Group V elements such as phosphorous, n-type silicon (see entry) is formed. back to topDirect Current (DC)(I)
Electricity that only flows in one direction around a circuit. A direct current or DC is created by batteries and photovoltaic cells. back to topDistribution board
The board which takes the incoming electrical power and distributes it to different circuits within the building such as lighting, hot water heating etc. Each circuit is protected by a fuse or circuit breaker. back to topEfficiency
Ratio of output power to input power of a device. Easy to remember as ‘what you get’ divided by ‘what you put in’. back to topElectrical energy
Energy is required to push electrons through the various components of a circuit. This is generally provided by a power supply that sets up an electric potential (energy) difference between its terminals. back to topElectric field
The electric field is due to the built-in voltage. The electric field acts on free electrons that are released by photons, forcing them to move in one direction only (towards the top layer). Force = electron charge x electric field strength. back to topElectron
Sub-atomic particle of negative charge that surrounds the positively charged nucleus of an atom. Electrons can be bound to their parent atom in electron shells, involved with bonding to neighbouring atoms or they can become free and mobile if they gain enough energy to escape the electrostatic attraction of the nucleus. back to topEnergy
Necessary for things to change, or events to happen. Energy can exist purely by itself as light, or it can be a varying property of matter (kinetic and potential energy). Energy always obeys the Conservation of Energy Law. A quantity measured in Joules. back to topFossil fuels
Fuels formed slowly over millions of years from buried and fossilised biomass (plants or animals). Most living things decompose when they die which releases carbon back into the atmosphere and to the carbon cycle. If the biomass is quickly buried without the chance to fully decompose the carbon can be stored geologically as coal, oil or natural gas and is removed from the active carbon cycle. back to topFree electrons
Electrons that are not bound to their parent atoms but are free to move around the crystal lattice and can carry energy. back to topFrequency
The number of times a pattern or process is completely repeated in one second. The frequency of a wave is the number of times its crest or trough is repeated in one second. Units are Hertz (Hz), or per second (s-1). Frequency (f) is related to wavelength (λ) and wave velocity (v) by the wave equation v = fλ. back to topGlobal warming
Global warming is the observed increase in the average temperature of the Earth’s atmosphere and oceans in recent decades. back to topGreenhouse effect
The process in which the absorption of infrared radiation by an atmosphere warms a planet. The natural greenhouse effect is due to naturally occurring greenhouse gases, while the enhanced greenhouse effect results from gases emitted because of human activities. back to topGreenhouse gas
Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occurring greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases. back to topGrid-connected
A premises is generally said to have obtained grid connection when its electricity is supplied from the national electricity grid. back to topIncident power
The rate at which energy strikes the surface of, for example, a photovoltaic cell or module. back to topInsulation
Insulation is a material such as wool, polystyrene, glass wool, mineral wool, paper-based insulation and polyester that reduces unwanted heat loss or gain in a building. back to topInverse square law
If something, e.g. light or sound radiates uniformly into space from a point source, then, at a distance d from the source, the power flux will be given by, P/πd2 where P is the total power emitted by the source. The flux decreases as the inverse square of the distance from the source. back to topInverter
Electronic device that converts the DC electrical power from the photovoltaic modules to standard AC (230V at 50 Hz) used in the home by appliances.. back to topIsolating transformer
The term ‘isolating transformer’ is normally applied to mains transformers providing isolation rather than voltage transformation. back to topJunction box
A special box that is glued in place over the positive and negative connection points on the solar module to keep the connections waterproof. back to topKilowatt hour
The energy represented by 1 kilowatt of power consumed for a period of 1 hour. back to topLinear regression
A mathematical technique for finding the equation of a straight line that best fits a set of data, and evaluating the fit. back to top back to top
