Memorandum submitted by Mitsubishi Electric
UK
1.0 SUMMARY
The UK needs a radical overhaul of the way we
heat domestic residential buildings.
26% of the U.K's overall CO2 emissions
come from domestic heating, lighting and appliances.
73% of household CO2 emissions come
from space heating and hot water demands.
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%.
Heat pump technology is already well used for
commercial buildings and in other countries.
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.
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.
There will be a greater need to cool homes but
the use of air conditioning equipment is not sustainable or necessary.
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.
Grants for air source heat pumps should be included
in the Low Carbon Buildings Programme.
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
Mitsubishi Electric (Living Environmental Systems
Division, UK) is one of the largest suppliers of cooling and heating
equipment for buildings in the UK.
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.
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.
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
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.
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.
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)).
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.
One of the main advantages of heat pumps is
their flexibility in application, eg a heat pump using air as
a heat source in under floor, radiator or fan coil heating systems.
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 45C and achieve an annual COP of 3.4 If used
with underfloor heating at 35C 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
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
24C 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.
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.
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 and Heat Recovery
Heat recovery plant has the ability to operate
in bypass mode to provide free cooling from the ambient air during
the summer period.
This table shows the ambient temperatures in
London, between 8am and 6pm, over 2006:
| Temp Range | No. of hours
| % of Total |
| T<8.0C | 877 | 21.99
|
| 8.0C-20C | 2,314 |
58.029 |
| T<20.0C | 797 | 19.99
|
From this graph, we can see that for over 58% of the time
the temperature was between 8C and 20C, allowing free
cooling when the air conditioning set point was 21C in cooling
mode. If the set-point is higher, then free cooling is increased.
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.
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 24C will not be exceeded
between 10 pm and 6 am. 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
The following key data addresses the heating and cooling
of a three bedroom semi-detached house built to 2006 building
regulations.
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.
Annual heating requirements
| Water heating load, assuming
160 Litres per day @ 55C
| 3,066 kWh |
| Space heating load with standard trickle vent
| 5,093 kWh |
| Total | 8,159 kWh
|
Heat with condensing Gas Boiler of 93% efficiency
| Gas consumed | 8,811 kWh |
| CO2 emitted | 1,674 kg
|
Heat with Heat Pump with annual COP of 3.02
| Electricity consumed | 2,703 kWh
|
| CO2 emitted | 1,162 kg
|
| Saving in CO2 emissions using a heat pump
| 512kg (31%) |
5.1 Further Reducing Heat Load
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%.
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
Over 1.6 million 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
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:
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
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 24C 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 24C is zero.
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
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.
A full electronic copy of the Green Gateway initiative is
available from www.greengatewayinitiative.co.uk
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