Eco Jargon Busting
Learn the meaning behind the eco words used in the energy world.
In all areas of life there are the ‘in’ words and the jargon that those in the know use all the time. However when you enter a new sector it can be very confusing – with abbreviations and acronyms left right and centre. The list below will provide a basic definition of some of the words used in the energy world……
A fuel (usually a liquid fuel used for road transport) that is produced from plants grown for the purpose or, more rarely, from kitchen or animal wastes. Examples of biofuel include alcohols (mainly bioethanol from fermented sugar from beet, sugarcane, wheat or maize), and biodiesel from vegetable oils, such as rapeseed or palm oil, or from waste cooking oils or fats (tallow).
Biofuels are seen by some environmentalists as an essential way to help combat global warming, as they directly replace petrol or diesel used by road vehicles. Petroleum products used in transport are the largest single use of fossil fuels, responsible for around a third of the CO2
emissions contributing to climate change. However other environmentalists are less sure about their benefit, as in many cases the savings from switching to biofuels are partly lost in carbon emissions producing the biofuels - from fertilisers, transport and processing the fuel. They argue instead that it is better to focus on improving public transport and the efficiency of vehicles.
Expanding the area of land used to grow energy crops for biofuels also risks creating a shortage of land for food crops. There have already been some instances of food price rises that have been attributed to crops being diverted for energy production (especially of maize) and there are concerns that rising demand for agricultural land could lead to deforestation in parts of the world such as South East Asia as new palm oil plantations are created. On the other hand, it makes real sense to utilise all possible waste vegetable oils, and biofuels may have a future role to play in aviation.
It is also possible to produce gaseous biofuels, such as methane, from anaerobic digestion of farming waste (such as slurry), and these have the added benefit of avoiding the risk of natural decomposition of waste forming methane under uncontrolled conditions that can itself form a significant global greenhouse gas. Historically solid biofuels, including wood pellets and chips, have also been used to power transport through fuelling steam engines or heating to create a gas that can be used in an internal combustion engine. These forms of biofuels may become important again in the future.
Carbon Dioxide (CO2) is a colourless gas that is given off by all living creatures, and when fossil fuels (such as coal, oil or gas) are burnt. Carbon Dioxide is re-absorbed by plants as the essential building block in the creating of solid plant matter - and this cycle of emission and re-absorption is called known as the carbon cycle. Carbon Dioxide in the atmosphere traps heat from the sun and a certain level is needed to order to keep the surface temperature habitable. However as more Carbon Dioxide is released into the atmosphere from burning fossil fuels, the earth's temperature is beginning to rise. This effect is known as Global Warming or Global Climate Change, as the resultant change in temperature can vary widely in different parts of the globe.
The carbon cycle from plants and animals is normally broadly in balance, with few changes to the amount of CO2
in the atmosphere or level of global temperatures over periods of many thousand years. However, since mankind started burning fossil-derived fuels, which had previously stored carbon underground for millions of years, the level of CO2
has started to rise sharply - from around 280 parts per million (ppm) in 1800 to around 384ppm today (2007 data). This has already led to a small increase in global average temperatures, and is believed to have led to more extreme weather occurrences.
Scientists are able to model future rises in atmospheric CO2
levels based on the forecast use of fossil fuels. They can also estimate what might happen to the global climate, including rises to sea levels resulting from polar ice caps melting, at different levels of CO2
. The consensus view is that total CO2
levels must be kept below 550ppm (and ideally below 450ppm) if the worst effects of climate change are to be avoided. Even at this level average temperatures may rise by at least 2°C, with some loss of coastal land and other productive agricultural areas.
A Carbon Footprint measures that amount of carbon dioxide that is left behind as a result of your activities.
Typically your carbon footprint will be expressed as an equivalent amount of tonnes of carbon dioxide (CO2
) emitted as a result of the energy you have used in a year. Sometimes it only looks at the CO2
resulting from your direct use of energy from fossil fuels - for example, the energy you have used in terms of gas (for heating), electricity (for light or power) or petrol (for transport).
But as this can under-estimate your contribution to global climate change, your carbon footprint is often extended to include the CO2
that was generated from the hidden energy in goods and services that you consume - for example the energy used in growing and processing the food that you eat, or the energy in the steel in the car that you may drive. This type of energy is often called "embodied energy" and the associated "embodied carbon" emissions can often exceed the direct emissions. Recent research by the Carbon Trust, for example, has shown that the embodied carbon dioxide in a 25g packet of cheese & onion crisps is around 75g - three times the weight of the food itself!
As global climate change is caused by several other gases as well as CO2
, your footprint may also be measured including the effect of these other gases, which include methane and several gases used as refrigerants.
Carbon footprints are not just calculated for individuals. It is possible to create a carbon footprint for a household, for a company, or even for an entire country. If you would like to find out about your own carbon footprint, why not visit our Carbon Workout
which includes a calculator to work out your own carbon footprint, and suggestions for actions that you can take to shrink your carbon footprint. And if you are a business or institution, then visit our simple carbon calculator
Climate Change (also sometime known as "Global Warming") is used to describe changes to the earth's climate - including air temperature, rainfall, storms and secondary effects such as ice cover and sea levels. Although there is always some degree of natural climate change, mankind is currently facing a very rapid shift in climate, due mainly to the emission of greenhouse gases, especially Carbon Dioxide (CO2) through the burning of fossil fuels such as coal, gas and oil.
Man-induced Global Climate Change due to rising CO2
levels was first identified by the Swedish chemist Svante Arrhenius around one hundred years ago, and has been generally accepted by scientists as a serious issue for over 25 years. Since the 1990s, the Inter-Governmental Panel on Climate Change (IPCC) has been studying the problem and concluded that urgent action needs to be taken to cut CO2
emissions (for example through improving energy efficiency and switching to renewable energy sources).
If allowed to go unchecked, the main effects of Global Climate Change are likely to include:
- Increasing temperatures across the globe, especially in Northern polar latitudes, leading to a speeding up of glaciers and melting of much of the Arctic ice sheet;
- More erratic rainfall, with droughts in some areas and floods in others, as part of a pattern of weather destabilisation;
- Rising sea levels (from the melting ice), with a loss of some Pacific islands and low-lying coastal areas (including parts of East Anglia, the Netherlands and Bangladesh);
- Loss of productive land (from sea level rises and droughts), with a risk of food shortages;
- Reduction in wildlife species, due to habitat loss and the inability of plants (and some animals) to migrate to new areas with more favourable climatic conditions.
Contraction & Convergence
At the moment developed countries, such as the UK, USA and other European countries have much higher annual emissions of carbon dioxide (CO2) per person than developing countries such as India. As CO2 is the main gas causing global climate change, this is felt to be unfair and unsustainable in the long term. Contraction & Convergence is the term used for the process under which developed countries will cut their CO2 emissions much faster than developing countries, so that by some future date (often seen as being 2100) all countries will emit roughly the same level of greenhouse gases per person.
The concept of Contraction & Convergence was first developed by the Global Commons Institute (GCI) as a way of encouraging a more equitable split of targets under international agreements such as the Kyoto protocol. By setting out a route plan under which it could be seen that all countries would eventually have an equal right to pollute, it could encourage developing countries to subscribe to a process that some felt would otherwise favour industrialised countries that already had high emissions of CO2
Scientists are still uncertain exactly what target level of CO2
emissions should be set, if the worst climate change effects are to be avoided. Many think that an ultimate CO2
concentration in the atmosphere of 550ppm (550 parts per million) is the absolute maximum, but that 450ppm would be a "safer" target. And it is also still not clear exactly what maximum level of emissions will be necessary in order to meet either of these target figures. Again, there seems to be a general consensus that emissions from a country like the UK should fall by at least 60% by 2050, and by 80% by 2100, although some scientists believe that this is not enough. In terms of individual emissions, this means that the current average figure of just over 5 tonnes of CO2
per UK resident will need to fall to under 2 tonnes by 2050, and under a tonne by 2100. If it helps, one tonne of CO2
at normal room temperature could fill 73,500 basket balls or 12 average sized living rooms, and an average African elephant weighs between 4 and 7 tonnes!
If you would like to see what your current emissions are, compare them to the 2 tonne ceiling for 2050 and discover how you may be able to reduce them, then you can calculate your emissions on our Carbon Workout
A condensing boiler is a type of boiler which achieves enhanced efficiency by incorporating an additional heat exchanger. This uses the heat in the exhaust gases from the boiler to preheat the water as it enters the boiler, and so recapturing energy that would otherwise be lost. When a condensing boiler is working at peak efficiency the water vapour produced by the consumption of gas or oil in the boiler condenses back into liquid water - hence the name "condensing boiler". Condensing boilers can have operating efficiencies of up to 95% in normal domestic use, compared to 70%-80% with a conventional design.
There is more information on our Condensing Boiler page.
In order to reduce the risk of adverse climate change, it is necessary to cut emissions of the main greenhouse gases, of which Carbon Dioxide (CO2) is the most important. This can be done through international agreements (such as the Kyoto protocol) or by national or regional Governments setting a limit (a "cap") on emissions from within their territory. However as it is not equally easy for all sectors or companies in a country to make the necessary cuts in CO2 emissions, a number of schemes have been set up through which a body (such as a company) that makes more than the required savings of CO2 can sell its surplus allowances to emit CO2 to another body that has a shortfall. This process is known as Emissions Trading.
Emissions trading can take place directly between companies, or between nations. However it is most commonly undertaken on an exchange, as this gives a greater transparency in pricing. Many emissions are traded as a result of internationally agreed programmes to cut CO2
emissions, including the EU Emissions Trading Scheme (ETS).
Greenhouse gas is a collective term used to describe a number of gases, Carbon Dioxide (CO2) being the greatest by volume, which act to trap heat (infra red radiation) in the atmosphere and lead to warming of the earth's surface. The Earth's average surface temperature is about 20-30°C warmer than it would be without the greenhouse effect. In common usage, "greenhouse effect" may refer either to the natural greenhouse effect due to naturally occurring greenhouse gases, or to the enhanced greenhouse effect which results from gases emitted as a result of human activities.
There are six main types of greenhouse gas. Although Carbon Dioxide (CO2
) is by far the greatest contributor to the greenhouse effect, a kilogramme of CO2
actually has a lot less effect than the same mass of one of the other gases. The global warming potential in the table below shows the equivalent amount of CO2
that would be need to have the same effect as a single unit of the other gas. As they are so much more potent, it is vitally important that even very low levels of emissions of these other gases are avoided.
CO2 equivalents of greenhouse gases
|Carbon Dioxide (CO2)
|Nitrous Oxide (N2O)
|Hydro-Fluoro Carbons (HFCs)
||From 140 to 9,800
||From 4,800 to 9,200
|Sulphur Hexafluoride (SF6)
Ground Source Heat Pump
A Ground Source Heat Pump, or GSHP, is a way of collecting energy from the ground and using it to warm or cool a building. This uses the earth as either a heat source, when operating in heating mode, or as a heat sink when operating in cooling mode. All Ground Source Heat Pumps have an external loop containing water or a water/antifreeze mixture, and a smaller internal loop used to heat or cool the building. Both loops pass through a heat exchanger inside the heat pump unit.
The external collector loops can either be laid in trenches (often using coiled water pipes popularly known as "slinkies", or run through a number of vertical boreholes. These are both types of closed loops, as the water stays in the collector circuit. It is also possible to have a so-called "open" loop, where water is extracted from a source, such as a lake or river, and then returned to the same source a little distance away, although open loops are only rarely used in the UK.
Another variant is an Air Source Heat Pump (ASHP), where air is used as the source of the heat or cooling fluid; air source heat pumps systems can either transfer the heat to an internal water circuit (as is the case with GSHPs), or to another air supply, for use with warm air heating systems, a method that is more popular in North America.
Ground (and Air) Source Heat Pumps work especially well with low temperature underfloor central heating systems, as they operate most effectively when raising water to a temperature of no more than 40°C. Although all the energy used to heat the building comes from the surrounding earth, water or air, some electrical energy is needed to drive the system and pump the fluids around. The overall efficiency of a system is measured by the ratio of useful heat delivered to the building divided by the energy used to operate the system; this is known as its Coefficient of Performance and will typically be between 3.0 and 4.0 for a well designed system.
Ground Source Systems are sometimes known (especially in Europe) as Geothermal systems, although they should not be confused with geothermal heating systems using hot aquifers or hot dry rocks that do not need a heat pump.
For more information about GSHPs, please visit the home page of the Ground Source Heat Pump Association
Hydro, Hydropower or Hydroelectric Power (HEP)
Energy in moving water can be harnessed and used to generate electricity. Since water is about a thousand times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts of energy. There are many ways energy can be harnessed from of water including tidal power, waver power and hydro. Hydroelectric power is a term often reserved for large-scale hydroelectric dams, which can have a mixed effect on the environment if not well located; small-scale hydropower can include the conversion of old mill streams to generate electricity.
The goal of insulation used in building construction is to slow down heat transfer. The same materials are required to keep buildings cooler in hot climates, or warmer in cold climates. As more insulation is installed, more comfort (thermal and soundproofing) is created, and operating costs are lowered. Insulation is most often used in the loft and in the cavities of walls, but it can also be installed under floors or attached to the inside or exterior of walls where there are no cavities to fill. For more information, see our insulation advice page.
Light tubes are a way of allowing natural daylight to be used deep inside a building.
Lighting into the interior of buildings can be substantially boosted by the inclusion of light tubes (often known as Sun Pipes after one of the leading UK suppliers). These reflect and intensify natural daylight through a highly polished mirror-finish aluminium tube to illuminate the space below. Light tubes typically have a clear polycarbonate top dome (which may be prismatically shaped to capture sunlight from varying angles during the day) to "gather" the light and at the lower end of the tube an opaque ceiling lens evenly diffuses the daylight into the space below. Due to the high reflectivity of the actual tube, they can bend round corners with only limited loss of light transmission, and are particularly useful for reaching into enclosed areas such as store rooms or toilets. On a bright day, a typical light tube provides illumination equivalent to a 500W tungsten bulb; even on a dull day it can still equal a 150W bulb. Some light tubes are available with an integrated ventilation tube, to provide additional natural ventilation into the same enclosed area.
Photovoltaics (PV) use solar cells (often arranged into larger modules) to convert light from the sun into electricity.
Although they were originally used on spacecraft and in small items like solar calculators, large scale photovoltaic arrays - normally mounted on a building's roof - can generate a significant proportion of the energy used inside that building.
Roof mounted PV should be oriented within 45% of South facing and ideally inclined at the around the same angle as the building's latitude, although they can be mounted into glazed units, sometimes as a building façade. The maximum output of a PV array is expressed in kilowatts-peak (kWp), which is the electrical power that it should provide under near ideal conditions. In the UK a well-positioned PV array will generate around 750hWh of electrical energy for every 1kWp installed. PV panels will produce some power under most daylight conditions, but work best in sunny weather. If a PV array is to power a typical UK home or to be connected to the UK grid, the power first needs converting from a low voltage direct current to 230V AC through an inverter. It is common for a large array to be arranged in a number of "strings" of panels, each of which is linked to separate inverter.
Although PV is one of the more expensive renewable energy technologies, it is especially useful when a building contains a seasonal energy requirement (eg. for refrigeration), or where a building is not connected to an electricity grid.
Technically, most photovoltaic panels are constructed from PV cells made from polycrystalline silicon slices, but there are other technologies becoming available. Amorphous silicon is a little cheaper and less rigid, but has a lower output per square metre of array due to having a lower conversion efficiency (ie. turns a lower proportion of the sun's energy into electrical energy). There are also some amorphous silicon products that can be bought pre-bonded to commercial roof coverings to make installation easier. Crystalline cells can also be found in the UK in smaller panels sold as "solar slates" or "solar tiles". Other higher efficiency types of PV being developed include thin film systems (using Cadmium Telluride) and Copper Indium Selenide (CIS), but suffer at the moment from higher costs and the risks associated with the use of toxic metals; researchers are also looking at polymer based cells.
Air travel is at least 2.7 times more damaging than would be explained simply by its CO2 emissions, because at high altitudes the vapour trails and emissions of ozone from aircraft engines also have a significant global warming effect. This effect is sometimes known as "Radiative Forcing".
The Inter-Governmental Panel on Climate Change (IPCC) use a factor of 2.7 as their reference scenario for the radiative forcing effect of flights. The Royal Commission on Environmental Pollution (RECP) report "The environmental effects of civil aircraft in flight
" explains the contributory elements in some detail, including contrails (vapour trails), high level ozone and an offset from the destruction of atmospheric methane by flights. However the effect is not
as often stated due to CO2
emitted at high altitudes being more damaging than CO2
emissions at low altitudes as is sometimes (erroneously) suggested. Strictly speaking, "radiative forcing" should be the term applied to all global warming effects from greenhouse gases relative to CO2
and not just kept to the additional effect from flights. CO2
at ground level (or dry CO2
at high altitudes) has a radiative forcing effect of 1.0. RECP's own estimate is that the "total radiative forcing due to aviation is probably some three times that due to the carbon dioxide emissions alone. This contrasts with factors generally in the range 1 - 1.5 for most other human activities".
Renewable Energy is energy taken from a resource that is naturally replenished and cannot run out over time. This contrasts with fossil fuels such as coal, oil or gas and nuclear power, based on uranium, all of which have finite resources. Renewable sources of energy produce fewer greenhouse gases than fossil fuels and so contribute less to global climate change.
The main types of renewable energy include:
- Solar Thermal Energy - most commonly found in the UK as Solar Water Heating, but can also contribute to space heating;
- Solar Electricity - generated from Photovoltaic Cells (PV);
- Solar Energy stored in the earth, water or air, and typically recovered by using a Ground Source Heat Pump;
- Wind Energy;
- Hydro, including large scale HEP from reservoirs and smaller millstream or run of river schemes;
- Wave Energy (either shore-based or offshore);
- Tidal Energy - from barrages or tidal flows or currents;
- Biomass - woody or grass-like plants grown for combustion to generate heat or electricity;
- Biofuels - liquid or gaseous fuels from plants (or more rarely animal sources), generally used in transport.
The following are often included with renewable energy:
- Passive Solar Design - arranging buildings so that they make maximum use of natural daylight and of the sun for winter heating, yet are shaded from the summer sun to prevent seasonal overheating;
- Geothermal Energy - using the earth's own internal energy to produce hot water for heating or electrical generation. (This is not strictly renewable, but is a carbon-free source of almost unlimited energy.)
Solar Thermal and Solar Water Heating
These usually consist of systems in which water is heated by the sun via a solar panel (solar thermal collector). Solar hot water systems are made up of sun collectors, a storage tank to store the hot water and a circulation loop to move the hot water from the collector to the tank. Air-based solar thermal systems pass air through a heat exchanger to pre-heat air for space (room) heating.
More information about Solar Heating Systems.
Wood pellets are a type of wood fuel, generally made from compacted sawdust. They are usually produced as a bye-product of sawmilling and other wood transformation activities. The pellets are extremely dense and can be produced with a low humidity content (below 10%) that allows them to be burned with a very high combustion efficiency. Pellet heating systems provide a low net CO2 solution, because the quantity of CO2 emitted during combustion is equal to the CO2 absorbed by the tree during its growth. Using the high efficiency burners developed in recent years, other emissions (such as NOx) are also very low, making this one of the cleanest heating options available.
More information about Wood Pellets.