Are you clear about
Renewable and Low
Carbon Energy?
Renewable energy is energy derived from sources that are
naturally occurring and either infinitely abundant, such as wind
or sunlight, or can regenerate in relatively short periods of time,
such as wood from trees.
Low carbon is a term used to describe energy that is derived
from (often renewable) energy sources that require some
initial fossil-fuel based energy input in order to exploit the
resource. The energy from these sources is referred to as low
carbon because each unit of energy derived has a significantly
lower level of greenhouse gas emissions associated with it
than if it had been derived solely from fossil fuels.
Are you Clear About Carbon? - Information Sheet 3 | November 2013
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The main types of renewable energy:
Hydroelectric power describes the
production of electrical power through
the gravitational force of falling or
flowing water. Hydroelectric power (or
hydro) supplies around 20% of the world’s electricity.
Norway produces virtually all of its electricity from hydro
whilst Iceland and Austria produce over 70% of their
electricity from hydro plants.
Wave energy generation technology
is at a very early stage of development
and a range of methods exist to try and
capture and convert wave energy into
electricity.
Biofuels are derived from plant
matter, organic waste and sewage.
Typical biofuels include biomethane,
bioethanol, biodiesel and biobutanol.
These fuels can be burnt to produce
heat and power, to run vehicles or
to power fuel cells. Biogas is also a
type of biofuel and is produced by the
anaerobic breakdown of organic matter
(without oxygen). Biogas is being increasingly used in
transport, in particular in countries such as Sweden and
Germany.
Are you Clear About Carbon? - Information Sheet 3 | November 2013
Biomass most often refers to organic
matter such as timber and crops grown
specifically to be burnt to generate heat
and power. Biomass can be classed
as carbon neutral because the carbon
released in the combustion process
is offset by the carbon trapped in the
organic matter by photosynthesis during its growth. To
be truly renewable biomass needs to be produced using
sustainable cropping and replanting systems. This also
ensures that the carbon is reabsorbed in a continuous
cycle. The most popular UK biomass crops are short
rotation coppice willow and poplar, miscanthus (also
known as Elephant Grass), reed canary grass and oil
seed rape. As well as specifically grown crops, other
agricultural by-products can also be used as biomass such
as straw, grain husks, waste wood and animal wastes such
as slurry and chicken litter.
Wind turbines convert energy from
the wind into electricity through a
generator. The UK has more usable wind
power than any other European country.
There are 354 UK grid-connected wind
farms containing 3,153 wind turbines
with the capacity to generate 6855 Mega Watts (MW)
(source BWEA, August 2012). Large-scale wind turbine
farms on and offshore are planned to become a major
supplier of electricity to the National Grid in the next
twenty years
Solar Photovoltaic (PV) cells use
ultraviolet light from the sun to generate
electricity. Solar PV cells can be arranged
in panels on a building’s roof, walls
or windows to provide electricity for
use in the building. With the latest PV
technology, cells can also be integrated into roof tiles and
groups of solar PV cells can be added together to provide
increasing levels of power. PV power stations, which are
typically referred to as ‘solar farms’ or ‘solar parks’, are
becoming increasingly widespread in the UK and supply
electricity directly to the National Grid through PV panels
mounted onto the ground. Solar PV cells only generate
electricity during daylight hours and have reduced
generation on cloudy and dull days. Solar PV generation
will often need to be supplemented by electricity supply
from another source.
Solar thermal uses the radiation from
the sun to heat water in a panel, often
sited on a roof, which in turn can supply
that heat to a hot water or a wet heating
system. Solar thermal is particularly
effective for producing hot water or low temperature
heating systems such as under-floor heating.
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What are the main types
of low carbon energy?
Hydrogen fuel cells
effectively store energy
like a battery. They
are commonly applied
alongside solar PV or wind
turbines to capture energy
during periods of generation which can
then be released when there is low or
no generation. The technology uses
electricity to break down hydrocarbons,
such as natural gas or methane, and
capture the hydrogen released from this
process. The captured hydrogen can then
be used as a fuel source which releases
electricity when exposed to an oxidising
agent which is usually oxygen in air.
Unlike conventional batteries, hydrogen
fuel cells do not require large amounts of
metals, which makes them cheaper, and
do not allow stored energy to leach away
over time.
sited at, or close to, the point of energy
consumption. This means that less
electricity is lost through distribution across
large distances, which in turn reduces the
amount of fuel that needs to be burnt to
deliver the same amount of energy.
Energy from waste
in its simplest form is
the capture of heat
from the burning of
waste materials. If CHP
technology is used then
electricity can also be
generated from this combustion. Most
waste streams will require input of a fuel
to initiate and regulate combustion and
the combustion of the waste will give rise
to emissions of cabon dioxide (CO2) and
nitrogen dioxide (NO2).
Nuclear power stations generating
Combined heat and power (CHP)
technology captures heat energy from
combustion (e.g. from burning natural
gas) for water and space heating as well
as generating electricity from pressurised
steam and gases. A key benefit of this
technology is that CHP units are typically
electricity do not lead to the emission
of GHGs. However, the extraction,
processing and safe disposal of nuclear
fuel along with the decommissioning of
power stations all demand energy from
another source which will be likely to emit
GHGs. Over its life, the GHG emissions
Are you Clear About Carbon? - Information Sheet 3 | November 2013
associated with the energy generated
from nuclear sources is lower than the
fossil fuel equivalents and therefore it
can be considered a source of low carbon
energy. France generates around 80% of
its electricity from nuclear energy.
Ground source heat
pumps (GSHP) extract
warmth from the ground
and convert this into
a higher temperature.
They effectively work
on the same principles as a fridge or air
conditioning unit, only in reverse. In a
fridge the heat is moved from inside to
outside, while a heat pump moves heat
stored underground to a building interior.
The heat energy is then taken up by a
hot water or heating system for use in a
building. GSHPs require electricity to drive
them but can be extremely efficient with
one unit of electricity likely to produce 3-4
units of heat energy.
Air source heat pumps (ASHPs) work
on the same principle
as GSHPs but extract
the heat from the air.
Installation of ASHPs
is much simpler and
cheaper but the available
heat is not as reliable
and systems are likely to be less efficient
than equivalent sized GSHP units. ASHPs
require electricity to drive them, but in an
efficient system one unit of electricity can
generate three units of heat. Efficiency
is reduced as air temperatures fall, but
the process of compressing air releases
heat energy even when ambient air
temperatures are below freezing.
Deep geothermal
extracts heat energy that
has been absorbed by the
earth’s crust and which
increases with depth. In
geothermal reservoirs,
which can be several
miles below ground, underground water
temperatures can reach 700 degrees.
Hot water or steam is piped up to the
surface to generate electricity (usually
by turning turbines), with the cooled
water often pumped back down to the
source to replenish it. Electric or fuel
powered pumps are required to return
the water, forced up under pressure, back
into the reservoir to complete the cycle.
Geothermal energy is more accessible
where the earth’s crust is thin, such as
in Iceland, where geothermal energy
contributes a significant proportion of
the country’s energy supply. The UK’s first
functional deep geothermal power plant is
under construction in Newcastle in North
East England.
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Energy Mix in the UK 2009-10
The chart below shows the UK energy mix based on information
provided by energy suppliers for the year 2011-12. The
importance of renewables has grown significantly over the past
few years but needs to grow further if it is to reach Government
targets of 15% by 2020.
What the government is doing
to increase renewable energy
generation capacity in the UK:
The Renewables Obligation
(RO) is currently the main
financial incentive for largescale renewable electricity.
41% Gas
29% Coal
19% Nuclear
9%
Renewables
2% Other
Source: DECC, 2012.
Note – figures have been rounded
It requires licensed electricity suppliers to
source a specific and annually increasing
proportion of their sales from eligible
renewable sources. Generators are issued
with Renewable Obligation Certificates
(ROCs) for every megawatt hour (MWh) of
eligible electricity produced. ROCs can be
sold on to suppliers either with or without
the associated electricity.
Further information on the RO &
ROCs is available on the Ofgem or
DECC websites.
The Feed-in Tariff Scheme
(FITS) is a Government scheme
that provides an additional
payment (above market
rates) for renewable energy
generated by households or
smaller scale generating sites.
The Tariffs give three financial
benefits:
– A payment for electricity produced, even
if used on site.
– Additional bonus payments for
electricity exported into the grid.
– A reduction in electricity bills as a result
of using energy produced on site.
FITs only apply to renewable electricity
generation but the Renewable Heat
Incentive (RHI) aims to give similar
support to a growth in renewable heat
generation.
Further information on FITs and
the RHI can be found on the GOV.
UK, Ofgem or DECC websites.
Are you Clear About Carbon? - Information Sheet 3 | November 2013
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