Energy efficiency & emission cuts
Energy efficiency means using less energy to provide the same
service. For example, a compact fluorescent bulb is more efficient than
a traditional incandescent bulb as it uses much less electrical energy
to produce the same amount of light. Similarly, an efficient boiler
takes less fuel to heat a home to a given temperature than a less
efficient model.
The phrase ‘energy efficiency’ is often used as a shorthand to
describe any kind of energy-saving measure, though technically it should
be distinguished from energy conservation – a broader term which can
also include forgoing a service rather than changing the efficiency with
which it is provided. Examples of energy conservation include turning
down a thermostat in the winter or walking to the shops rather than
driving there.
Increasing energy efficiency often costs money up-front but in many
cases this capital outlay will be paid back in the form of reduced
energy costs within a short time period. This makes efficiency
improvements an attractive starting point for reducing carbon emissions.
The scope of the savings – and the techniques required – depend on
the situation and location. For homes in cool countries such as the UK,
the most effective measures include increasing insulation, draught
proofing, installing good-quality double-glazed windows and switching to
more efficient appliances and light bulbs. The Committee on Climate
Change (CCC) estimates that these improvements could reduce annual CO2
emissions from British homes by around 17 million tonnes by 2020 –
around a tenth of the 2008 residential total.
By contrast, increasing efficiency in non-domestic buildings often
means focusing on ventilation and air-conditioning, in addition to
lighting, heating and appliances. Many such buildings have achieved
savings of around 25% after undergoing a refit to increase efficiency.
Energy-intensive industries, such as iron, steel and cement manufacture,
have become more efficient over time due to new equipment and better
re-use of waste heat. For example, a hot pipe containing a chemical that
needs to be cooled can be used to heat up other chemicals (this is known
as ‘heat integration’). Motors are used widely in industry for a variety
of tasks, such as pumping, mixing and driving conveyor belts. The
installation of efficient, correctly sized motors and drives can result
in energy savings of 20–25%.
Vehicles have also become more energy efficient over the decades
thanks to factors such as improved engines and lighter, more aerodynamic
designs. The potential exists for further improvements and in EU the
emissions of the average new car is set to decrease from 150 to 95 grams
of CO2 per km by 2020. The CCC forecasts that the introduction of
efficiency improvements to cars, vans and HGVs could reduce CO2
emissions in the UK by 12.3 million tonnes by 2020 – around 10% of total
for surface transport in 2008.
Improving energy efficiency does not necessarily translate into
reduced CO2 emissions: the savings depend on the situation. If the
energy is supplied from fossil fuels – such as petrol in a car or
electricity from a coal-fired plant – then improved efficiency will cut
emissions. But if the energy is supplied by a low-carbon source such as
electricity from nuclear or renewables, then improving efficiency may
have little impact on emissions. (When comparing electric and
non-electric appliances, it’s important to consider the efficiency of
the power generation, too: switching from a 90% efficient gas boiler to
a ‘100% efficient’ electric heater will increase energy use and
emissions if the electricity comes from regular fossil fuel power
plants, which themselves are highly inefficient, losing much of the
energy in their fuel as waste heat.)
Energy efficiency is always a good idea. Whether it results in energy
savings depends on what we do with the money we saved. In some cases,
efficiency savings can be offset by changes in user behaviour – the
so-called ‘rebound effect’. One example would be that insulating a home
may make it more economic for the resident to maintain a higher
temperature, increasing the standard of comfort but reducing the energy
savings.
Nonetheless, improving energy efficiency is a key tool for reducing
CO2 emissions, alongside energy conservation and low-carbon energy
sources such as renewables and carbon capture and storage.
Guardian.co.uk
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