COMMUNITIES AND LOCAL GOVERNMENT COMMITTEE INQUIRY: EXISTING HOUSING AND CLIMATE CHANGE
Memorandum by Mitsubishi Electric UK
1.0 EXECUTIVE SUMMARY
q The
UK needs a radical overhaul of the way we heat domestic residential buildings.
q 26%
of the U.K's overall CO2 emissions come from domestic heating,
lighting and appliances.
q 73%
of household CO2 emissions come from space heating and hot water
demands.
q Heat
pumps sourcing energy from the ground or the air and used for water and space
heating in homes are three times more efficient than 93% efficient condensing
gas boilers and can reduce CO2 emissions by up to 40%.
q Heat pump technology is already well
used for commercial buildings and in other countries.
q Electrically powered ground
source heat pumps draw on the natural energy in the earth generating up to four
times more efficient heat production than that offered by a conventional gas
boiler with substantial reductions in CO2 emissions.
q Electrically powered air
source heat pumps are slightly less efficient than ground sourced, but are
cheaper to install and maintain and offer greater flexibility for heating
homes.
q There will be a
greater need to cool homes but the use of air conditioning equipment is not
sustainable or necessary.
q Heat recovery units save
energy in ventilation and therefore help to reduce the amount of heating
required when introducing fresh air into more thermally efficient air tight
homes.
q Grants for air source heat pumps should be included in the
Low Carbon Buildings Programme.
q The use of free cooling through heat
recovery units obviates the need for air conditioners.
2.0 NEED FOR CHANGE IN HEATING
AND COOLING OF BUILDINGS
q Mitsubishi Electric (Living
Environmental Systems Division, UK) is one of the largest suppliers of cooling
and heating equipment for buildings in the UK.
q The Company has recently produced a
policy paper entitled the Green Gateway
Initiative which calls for a radical change to the way we heat and cool
both commercial and domestic properties in the UK to improve energy efficiency
and drive down CO2 emissions.
q Managing the internal temperatures of
the environment in which we live has to keep pace with the new technologies
that are available and the incremental savings in CO2 that are eminently achievable. The engrained thinking of using fossil fuel boilers for
central heating and hot water needs to be revisited both environmentally and
economically.
q In Mitsubishi Electric LES' view it is the optimisation of grid electricity and the effective use of locally
generated renewable electricity that is key to the future of any sustainable
domestic energy policy. Cleaner forms of electricity from either nuclear or
renewables (either grid or on-site) are better employed in the residential sector
by driving efficiencies at the point of use.
We are focusing on driving new technology, already proven in the
commercial sector, and improved further for use in the residential sector. Much
of this focus centres on heat pumps using 'free' energy in the air and ground
for heating and cooling. This is where the most
significant single source of CO2 reduction can be
delivered.
3.0 HEAT PUMP TECHNOLOGY TO REDUCE CO2
EMISSIONS
3.1 Heat Pumps for Heating
q Heat Pumps are movers of heat energy. They upgrade
naturally occurring low temperature heat into useful high temperature heat, and
vice versa to provide cooling. They take the heat from natural sources (air,
the earth or water) to warm a building. Therefore, the amount of energy used is
much less in a heat pump, significantly lowering costs and carbon emissions.
q In countries such as France and Sweden, heat pumps
are often used as a primary source for heating and hot water. With improvements
in technology heat pumps offer unrivalled efficiencies and are proven to
deliver this in a range of different environments.
q The operational characteristics of a heat pump are totally different
to those of an electric or gas boiler. With a conventional boiler, one kilowatt
of energy 'in' gives less than one kilowatt of heat to the building. With a
typical electrically driven heat pump, one kilowatt of energy 'in' gives a heat
output in excess of 3 kilowatts - a 300% increase in energy efficiency
and this will grow as technology develops. (This ratio is known
as the Coefficient of Performance (COP)).
q Building Regulations recognise the benefits of heat
pump technology. The 2005 Government SAP (Standard Assessment Procedure)
documents state the standard level of efficiency for different heating plant as
follows:
- Ground-to-air heat pump (electric) 320%
- Water-to-air heat pump (electric) 300%
- Air-to-air heat pump (electric) 250%
- Gas-fired, ground or water source 120%
- Gas-fired, air source 110%
- Single point gas water heater (instantaneous at point
of use) 70%
Electrically powered heat pumps sourcing energy from
the ground or the air and used for water and space heating in homes are more
than three times more efficient than gas boilers and can reduce CO2
emissions by up to 40%.
A modern inverter driven air to water heat pump that
could be used to replace a gas boiler can have an average annual efficiency of
300~360%. The technology is already
well used for both domestic and commercial buildings and in other countries.
q One of the main advantages of heat pumps is their
flexibility in application, e.g. a heat pump using air as a heat source in
under floor, radiator or fan coil heating systems.
q Heat Pumps can provide air to air or air to water
heating. An air to water heat pump can be used with conventional radiators at
45ºC and achieve an annual COP of 3.4 If used with underfloor heating at 35 ºC
this would increase to 3.7. The benefits of using a Heat Pump Boiler in an under floor heating system include:
- Does not waste energy by raising the flow temperature
high then dropping it for entry in to the under-floor system as a gas boiler
does
- Costs less to run due to
lower power consumption
- Reliable, long lasting and maintenance free
- No hot air in front of glass, no heat loss through
windows
- Less heat loss through ceiling and walls than
traditional radiators using a gas boiler
4.0 COOLING HOMES
q As climate change affects the length and heat of the summer
periods, and with more efficient house insulation,
there is the increased threat of over heating in summer. Without any form of
cooling, UK night time bedroom temperatures will exceed 240C for up to 164
hours per year - approximately 20 days per year. This has the potential to
increase sales of air conditioning for use in homes and, indeed, data
from the Energy Saving Trust indicates that sales of domestic air conditioners
increased from 32,800 in 2005-06 to 72,300 in 2006-07.
q The purchase of an "A" rated air
conditioner, and its associated energy consumption, results in additional
carbon dioxide (CO2) emissions of around 138 kgCO2 /year.
The 72,300 domestic air conditioners purchased in 2006-07 would therefore be
expected to increase CO2 emissions by at least 9,900 tonnes CO2
per year.
q Although a major supplier of air
conditioners, Mitsubishi Electric (LES) does not support the growth of air
conditioning in the residential market which it considers is neither necessary nor sustainable.
Instead, alternative ways to cool homes, using free cooling and ventilation,
are available and should be actively examined and promoted.
There will be a greater need to cool homes but the use of air conditioning equipment is not sustainable or necessary.
4.1 Free
Cooling & Heat Recovery
q Heat recovery
plant has the ability to operate in bypass mode to provide free cooling from
the ambient air during the summer period.
q This table shows the ambient temperatures in London,
between 8am and 6pm, over 2006:
q From this graph, we can see that for over 58% of the
time the temperature was between 8ºC and 20ºC, allowing free cooling when the
air conditioning set point was 21ºC in cooling mode. If the set-point is
higher, then free cooling is increased.
q Units that recover waste energy reduce overall energy
costs by extracting stale air and then recovering the heating or cooling energy
to either warm or cool incoming fresh air. By utilising this energy, the system
can save up to 30% on initial capital costs of heating and cooling plant, as
well as giving 20-50% lower energy costs.
q When the outdoor temperature is lower than the
indoor temperature in the summer, fresh outdoor cool air is used to reduce the
indoor air temperature. The result is that 24ºC will not be exceeded between
10pm and 6am. Mechanical air conditioning is therefore not necessary to
maintain night time comfort.
Heat recovery units use cooler outdoor air to reduce
indoor temperatures without the need for extra cooling so saving energy.
5.0 HOW FURTHER IMPROVEMENTS MIGHT BE ACHIEVED
q The following key data addresses the heating and
cooling of a 3 bedroom semi-detached house built to 2006 building regulations.
q
The Company
has produced this study to put forward an evidence-based case against the
continued use of gas boilers and to build the case for solutions that are made
possible through free cooling & heat recovery.
5.1 Further Reducing Heat Load
q By making the house air tight (not using trickle vent
systems) and ventilating with heat recovery equipment, the space heating load
of the building can be reduced by 39%.
q As detailed
earlier, the free cooling function of these products can then prevent the need
to install mechanical cooling for night time comfort, saving future potential
increases in energy consumption.
5.2 Using Heat
Pumps For The Refurbishment Of Existing Housing Stock
q Over 1.6m
domestic gas boilers are sold in the UK every year. Modern gas boilers are
efficient, but the technology has reached the summit of its possible energy
efficiency
q
Looking at existing houses, there
would be a 14% reduction in CO2 emissions by replacing an old gas
boiler (with an efficiency of 80%) with a new gas boiler (with an efficiency of
93%). The reduction is more substantial if the old gas boiler is replaced with
a heat pump with a COP of resulting in a 38% reduction in CO2
emissions, as shown in the graph below:
q A COP of 3 is
conservative. Based on new technology now available, a typical heat pump system
with a seasonal COP of 3.4 vs a typical existing gas boiler running at 70%
efficiency will have carbon savings of over 50%.
Grants for air source heat pumps should be included
in the Low Carbon Buildings Programme.
5.3 2016
Building Regulations and Improved Insulation
q As we move towards 2016, building insulation levels
will further increase with an expected reduction in space heating load of over
50%. Ventilating a house will become more important as insulation and air
tightness increases. The forecasted number of hours when a bedroom will exceed
24ºC during night time will rise to 690 without any active ventilation
strategy. If heat recovery ventilation is used and the free cooling mode
activated, the number of night time hours above 24ºC is zero.
q The advantages of using a heat pump for space heating
will increase as electricity generation becomes cleaner. Electricity generated
from a renewable source can provide zero emission heating and provide greater
than 3kW of heat for each 1kW generated.
5.4 Expected Outcome
q If all new residential build used heat pumps and heat
recovery units and all the domestic gas boilers replaced each year were
replaced with heat pumps, by 2020 the potential annual saving in CO2 would
be 14.7 million tonnes out of a total of 155 mt accounted for by the
residential sector as end users.
Replacing
a gas boiler in an average house with a heat pump could lead to a reduction of
CO2 emissions of 38% on average.
The
use of free cooling through heat recovery units obviates the need for air
conditioners.
