APPENDIX 4: GLOSSARY OF TERMS AND ABBREVIATIONS
Biofuel: This term covers
those fuels derived from organic material (see biomass), whether
solid, liquid or gaseous (see biogas). The term is used to differentiate
these fuels from fossil fuels which are ultimately derived from
organic matter but are the result of geological processes. Example
biofuels include: wood chip pellets (solid), ethanol derived from
sugar cane (liquid) and anaerobic digester (gas).
Biogas: This term would
typically be used to describe the gas produced by the anaerobic
(meaning in the absence of oxygen) breakdown of organic material
(see biomass). It includes gas from landfill sites and from purpose-built
anaerobic digesters that may take agricultural waste as their
feedstock. Whilst the composition of the gas will depend on the
source organic material, it is usually a combination of methane
and carbon dioxide which can then be combusted for electricity
generation, to provide heating, or both.
Biomass: Biomass is a
term used to describe organic material which can either be used
directly as a fuel source (for example wood), or can be processed
into a usable fuel (see biofuel and biogas). The material may
be waste from other processes such as agriculture or forestry,
or may be grown specifically for use as a fuel or feedstock to
convert into biofuel. Biomass combustion technologies for electricity
generation and CHP are widely used in some parts of Europe and
are commercial technologies that can be cost competitive with
fossil fuels if a low cost biomass feedstock (such as waste wood)
is available.
CHP: Combined Heat and
Power (CHP) technologies aim to increase the overall efficiency
of combustion-based electricity generation by using the waste
heat from the process to supply a heat demand. The heat demand
may be for industrial processes or for space heating. Industrial-scale
CHP plants combined with district heating systems to distribute
the heat output to public and private buildings are a well established
technology, common in some parts of Europe.
EC: European Commission.
EU: European Union.
FiT: Feed-in tariff.
GoO: Guarantee of Origin.
Ground/air heat pumps:
The basic principle of these devices is that they convert the
low-grade diffuse heat energy in the ground or air to a high-grade
concentrated heat source suitable for space and water heating.
The process is similar to a refrigerator operating in reverse,
and requires an electrical energy input to drive the pump. The
heat output from the process is typically two to four times more
than the energy required to drive the pump, with air-source devices
typically being toward the lower end of this range and ground-source
typically being towards the upper end of the range.
GW: GigaWatt (a measure
of instantaneous power, one billion (thousand million) Watts).
The unit of power installed capacities of countries and large
power stations are often denominated in.
GWh: GigaWatt hour (a
measure of energy, one GigaWatt of power delivered for one hour).
Hydro power: Hydro (or
hydro-electric) power harnesses the kinetic energy of water as
it runs down from a high level catchment area to a lower level,
typically in mountain regions. The energy of the flowing water
is captured either by exploiting the natural force of streams
and rivers, or by constructing a hydro-electric dam. The water
flow is directed towards a turbine generator to produce electricity.
Since river flow is rain-fall dependent, this resource is subject
to seasonal and longer term climatic fluctuations. Hydro power
can also provide a relatively high capacity means of storing energy
and is often used for peak electricity load demand since it is
easily brought on and off-line. Hydro-power is exploited commercially
world wide, contributing around 17% of global electricity supply.
There is limited potential for expansion in the UK.
KW: kiloWatt (a measure
of instantaneous power, one thousand Watts).
KWh: kiloWatt hour (a
measure of energy, one kiloWatt of power delivered for one hour).
The unit domestic electricity bills are denominated in.
MEP: Member of the European
Parliament.
Mtoe: Million tonne of
oil equivalent is a unit of energy: the amount of energy released
by burning one tonne of crude oil.
MW: MegaWatt (a measure
of instantaneous power, one million Watts).
MWh: MegaWatt hour (a
measure of energy, one mega Watt of power delivered for one hour).
The unit sales of wholesale electricity are often denominated
in.
RO: Renewables Obligation.
ROC: Renewables Obligation
Certificate.
Smart meters: Advanced
electricity meters. 'Smart' is a generic term used to cover a
range of devices, from enhanced meters that provide real-time
and readily-understood electricity consumption information to
consumers, through to devices which monitor the demand/supply
balance on the electricity grid and are able to shut down appropriate
appliances when supply is insufficient to meet demand. The aim
of the former is to encourage consumers to reduce electricity
consumption, the aim of the latter is to smooth out demand/supply
fluctuations.
Solar Photovoltaics: Solar
photovoltaics (PV) convert sunlight directly into electricity.
Photons of light liberate electrons in an appropriate semi-conducting
material. Unlike almost all other technologies for generating
electricity they have no moving parts and do not depend upon kinetic
or thermal energy. Current commercial devices are manufactured
from silicon-based semi-conducting material. PV can be utilised
in a range of scales from tiny cells for electronic goods to large
arrays. The most common application for power generation is building
integrated PV where panels made of PV are mounted on domestic
or commercial buildings. Other semiconductors can also be used
and novel materials and designs are being actively researched
throughout the world. The technology is commercially available
but is relatively expensive compared to other commercial renewable
technologies such as wind and hydro power. Research efforts are
focused on cost reduction.
Tidal stream and barrage:
Tidal stream power exploits the kinetic energy of tidal currents.
Most designs use underwater turbine generators similar to wind
turbines. Energy capture is optimised in areas of powerful currents
where natural flows are concentrated between obstructions, for
example at the entrances to bays and rivers, around headlands,
or between land masses separated by water. Tidal barrages exploit
the potential energy in the height difference between high tides
and low tides by impounding the receding tide. The barrage is
a form of dam across a river or estuary that blocks tidal water
during its ebb phase and then releases the water through a turbine
generator to create electricity. Tidal barrages typically have
a greater visual and environmental impact than tidal stream devices
and there are a limited number of suitable sites for barrages
around the world. Unlike some renewable energy sources, both tidal
stream and barrages benefit from being predictable.
TW: TeraWatt (a measure
of instantaneous power, one trillion (thousand billion) Watts).
TWh: TeraWatt hour (a
measure of energy, one TeraWatt of power delivered for one hour).
The unit national annual consumption of electricity is often denominated
in.
Watt: Measure of instantaneous
power, one Joule per second.
Wave power: Electricity generated from ocean waves.
The fledgling wave power industry is characterised by a plethora
of device types but they all seek to harness the energy in rising
and falling wave fronts to generate electricity. No technology
has established a dominant position although the oscillating water
column (OWC) based devices for shoreline generation have been
demonstrated effectively. For offshore power generation, the 'Pelamis'
articulated floating tube device is possibly the nearest to commercial-scale
deployment. At present only a small number of demonstration devices
are in operation world-wide. Reflecting the early stage of wave
power, costs are generally high compared to more developed options
such as wind power.
Wind power: Electricity
generated from the wind. The basic principle involves harnessing
the energy of a moving air stream to rotate a shaft to which an
electrical generator is attached. This is a well-established technology
and the dominant design for large-scale power generation is the
tower-mounted horizontal axis turbine where the turbine blades
face into the wind direction. Turbines for commercial electricity
generation are usually clustered together to create 'wind farms'.
Wind power is the most commercially advanced renewable energy
technology (apart from hydro), with around 90 GW installed worldwide.
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