Generating new ideas for meeting future energy needs
Glossary
electrolysis. Chemical reactions brought about by passing electricity through a solution. The following equation illustrates the process of the electrolysis of water (H2O).
2H2O + electricity → 2H2 + O2
electrolyte. A substance that produces ions (particles with an electric charge) when dissolved in water. The resulting solution (which can also be referred to as an electrolyte) conducts electricity.
fuel cell. A device that converts energy from chemical reactions directly into electrical energy. The simplest fuel cell 'burns' hydrogen in a flameless chemical reaction to produce electricity. In order to 'burn' the hydrogen a fuel cell needs a source of oxygen and this is usually obtained from air. The only by-product from this type of fuel cell is water.
For more information about fuel cells see our Nova topic Fuelling the 21st century.
gasification. A process that exposes a solid fuel to heat in the presence of limited oxygen to produce a gaseous fuel. This fuel contains hydrogen but also other gases such as carbon monoxide, carbon dioxide, nitrogen, and methane. Under suitable circumstances, gasification can produce synthesis gas, a mixture of just hydrogen and carbon monoxide.
genetic engineering. A set of procedures whereby a specific piece of DNA can be excised from a chromosome and inserted into the DNA of a chromosome of a different organism.
greenhouse gas. A gas that is transparent to incoming solar radiation and absorbs some of the longer wavelength infrared radiation (heat) that the Earth radiates back. The result is that some of the heat given off by the planet accumulates, making the surface and the lower atmosphere warmer. For more information see The greenhouse effect (CSIRO Atmospheric Research, Australia).
hydrocarbon. Compound containing only the two elements, carbon and hydrogen.
kilowatt, megawatt, gigawatt. The basic unit of power (the rate at which energy is used) in the metric system is the watt (W); a kilowatt is 1000 watts. A watt is a very small amount of power and in most mechanical applications we count power in kilowatts. A kilowatt is about equal to the heat energy put out by a single bar radiator, and is also about equal to the power expended by a person running up stairs. A car engine typically produces 50 to 100 kilowatts.
photosynthesis. The biochemical process in which green plants (and some microorganisms) use energy from light to synthesise carbohydrates from carbon dioxide and water. Photosynthesis can be shown as:
CO2 + H2O + energy → [CH2O] + O2
photovoltaic (PV) cells. Also known as solar cells. A photovoltaic cell is made of thin wafers of two slightly different types of silicon. One, doped with tiny quantities of boron, is called P-type (P for positive) and contains positively charged 'holes', which are missing electrons. (Electrons are negatively charged particles that orbit the nuclei of atoms.) The other type of silicon is doped with small amounts of phosphorus and is called N-type (N for negative). It contains extra electrons. Putting these two thin P and N materials together produces a junction which, when exposed to light, will produce a movement of electrons – and that constitutes an electric current. Photovoltaic cells thus convert light energy into electrical energy.
plate tectonics. The theory that the Earth's surface is made up of huge plates that have moved very slowly during geological history, and continue to move, thus changing the position of continent and oceans. The plates are about 100 kilometres thick and move at a rate of about 1-12 centimetres per year.
potential energy and kinetic energy. Potential energy is stored or supressed energy. For example, the wound-up spring of a toy has potential energy. Kinetic energy is the energy associated with a moving object (energy of motion). In the example of the toy, potential energy is converted into kinetic energy when the toy is set running.
For more information see Energy basics (Nova: Science in the news, Australian Academy of Science).
pyrolysis. A process which involves heating biomass to drive off the volatile matter, leaving behind the black residue we know as charcoal. Pyrolysis can be used to produce ‘biochar’ from waste plant matter as a means of removing carbon dioxide from the atmosphere.
turbine. A device in which a stream of water or gas turns a bladed wheel, converting the kinetic energy of the fluid flow into mechanical energy available from the turbine shaft. The earliest turbines were water wheels. Now, steam turbines are driven by jets of high-temperature steam; gas turbines are driven by burning fuel vapour; and wind turbines use the power of moving air.
Page updated August 2006.