Technology Heat pumps
There are around 1.6m domestic
boilers replaced every year, so there
is a huge potential to replace these
with heat pumps to reduce energy
consumption – Graham Wright
> heating technology that can offer better coefficients
of performance (COPs) than a gas-fired boiler is to
be welcomed,” he adds.
Clearly, heat pumps are seen as a key element in
this strategy, and the most appropriate choice will
depend on a number of factors. For example, the
electrical load for dwellings has doubled since 1970
and is typically around 5,000 kWh/year. Much of this
will be dissipated as heat so, combined with better-
insulated buildings, the overall effect is to further
reduce space heating requirements.
This trend, therefore, increases the potential
opportunity to use lower heating capacity
Sanyo’s CO2 heat pump, recently launched in the UK, was tested at this cottage on Exmoor, Devon technologies such as heat pumps. >
Product profile Sanyo aims for wider marketplace
Sanyo recently launched its ECO carbon a compensated heating circuit so that
dioxide-based heat pump in the UK – a as ambient temperatures rise, the flow
system that, the company claims, overcomes temperature to the heating system can be
many of the barriers that have limited decreased to improve the SEER.
the wider use of heat pumps for heating, The 9kW version is said to be suitable for
especially in the domestic sector. a 140 sq m house with a heating load of 65W
In particular, its ability to generate higher per sq m. But for newer homes with improved
water temperatures as a result of the higher insulation, this could increase to a 240 sq m
discharge temperatures of CO2 refrigerant is house. In most cases, supplementary heating
said to eliminate the need for supplementary would be needed to ‘top up’ DHW if the heat
electric heating in many applications. pump is used primarily for space heating.
Output temperatures up to 90 degrees C To deal with the high pressures involved,
from the ECO are theoretically possible, Sanyo has developed what is claimed to be
though the system used in the UK is designed the world’s first two-stage rotary compressor
not to exceed 65 degrees C. This, says the for use with CO2. The compressor has
company, can be achieved at outside ambient been engineered to ensure effective load
temperatures down to minus 25 degrees C. dispersion, necessary to accommodate the
Sanyo’s stated COP figure for the model high working pressures and minimise the risk
is “up to 3.7”, though this is for a water of leaks. Sanyo’s ECO carbon dioxide-based heat pump
temperature of 35 degrees C at an ambient The compressor also offers quiet operation,
temperature of 15 degrees C. If water is claims Sanyo, with the 9kW version operating Exmoor, supplying both heating and hot water
supplied at 65 degrees with an ambient at noise levels of 47dB(A) at 1m – lower systems. The outdoor unit was installed in a
temperature of 7 degrees C, the COP falls to than many split-system air conditioners and temperature-controlled workshop, allowing
2.7. The more meaningful Seasonal Energy an important consideration for domestic the temperature of the ‘outside’ air to be
Efficiency Ratio (SEER) is 3.7 for water at applications. controlled between 20 degrees C and minus
35 degrees C and 2.6 for water at 65 degrees C. Currently, these units are only available in 2 degrees C.
The inverter-controlled ECO system capacities up to 9kW because of the need for The system’s performance was monitored
consists of an outdoor heat pump unit, special compressors, but the company says it for four months. A COP of 3.7 was recorded
containing the compressor and CO2 is working on larger compressors that would with water at 35 degrees C and an ambient
refrigerant circuit with 1.4kg of refrigerant, extend the application possibilities. temperature of 15 degrees C. A COP of 2.71
linked to a thermal store containing a In its first UK trial, a 9kW Sanyo ECO CO2 was recorded with a flow temperature of
heat exchanger for hot water supply. The heat pump replaced an existing oil-fired boiler 65 degrees C, at an outside temperature of
system also incorporates controls with at a 200-year-old, three-bedroom cottage on 7 degrees C.
50 CIBSE Journal May 2009 www.cibsejournal.com
CIBSEmay09 pp48-50,52 pumps.indd 50 5/1/09 10:14:35 AM
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