ENERGY SAVING
using heat recovery wherever possible for ‘free’ heating or cooling. It can then also employ a water source heat pump producing high temperature hot water primarily for domestic hot water.
One example is the Rhoss EXP/HT heat pump system. What makes this heat pump stand out is its use of cutting-edge technology which contributes to environmentally friendlier cooling/heating through reduced carbon emissions, best-available energy efficiency and improved performance.
A hybrid four-pipe heat pump like the Rhoss EXP/HT can produce simultaneous or independent cooling and heating, just like a traditional chiller or heat pump. However, what makes it exceptionally worthwhile is its use of a third heat exchanger within the machine so that, when cooling, the heating can be essentially free due to heat recovery, and vice versa.
That is why it is the preferred building cooling and heating solution for the GLA (Greater London Authority) and many planning authorities. In addition to stand-alone, low carbon
heating via operation in simple heat pump mode, the hybrid four-pipe heat pump system can provide increased system efficiency results from simultaneous cooling with heat recovery, delivering ‘free’ space heating and domestic hot water pre-heating as a by-product of cooling.
The high temperature water source heat pump efficiently boosts medium grade heat to high grade heat. This results in higher plant utilisation, with heat recovered from the cooling cycle being used to help the high temperature heat pump deliver total efficiency ratios of 7.0 to 8.0. Since it is an integrated heat pump solution, there is no need for a boiler which results in a significant plant space saving and lower equivalent CO2
emissions in operation. It is a
single source polyvalent solution, which means operational risk is reduced and maintenance is faster, cheaper and easier.
A case study has revealed a 22% operating
energy cost saving and 28% reduction in carbon emissions compared to a traditional chiller and boiler four-pipe solution (without water source heat pump). The additional cost of 28% for the hybrid heat solution over a chiller and boiler system was paid back in just over two years from the energy cost saving. The solution means there is no need to burn fossil fuels for any site heating requirement. Indeed, reduced (and still reducing) mains
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electricity carbon conversion factors make this a low carbon solution that will become lower still through its working life. The development of this type of system follows a distinct trend. Consultants are shifting away from chillers and boilers in favour of all-electric cooling and heating solutions, with demand being driven by legislation and government targets to cut carbon emissions by 80% by 2050. Of course, heat pumps have offered low
carbon heat and cooling for many years, but the decarbonisation of the electricity grid as well as renewables becoming more prevalent has strengthened the case for this technology. The carbon content of electricity – and therefore heat pumps – has halved over the last decade and, although heat pumps can cost more to install than other forms of cooling, the cost of fitting them is already plummeting, not least because familiarity is also increasing rapidly.
Heat pumps can harness otherwise ‘waste’ heat for heating. A high performance and short payback can be achieved by taking waste heat and boosting its temperature to a useful level. Air-side heat recovery (see the box)
can provide freshly filtered air into rooms while, at the same time, preserving heat that would normally be wasted. According to the Renewable Energy Hub (www.
renewableenergyhub.co.uk), heat recovery ventilation systems, for example, offer a host of benefits, which include: The supply of warm, fresh air in a constant flow – because you are creating a self-con- tained environment with a superior ventila- tion system, the air will be cleaner.
Lower energy costs and carbon emissions. Less humidity and condensation which can cause health problems and affect walls and structures over time.
Fewer irritants like pollen and pollution as the ventilation is filtered throughout the building.
Lower energy bills, because the warm air is being reconstituted, it takes the workload off the heating system.
There is, of course, no silver bullet to fix the climate change challenge. The answer in terms of comfort systems will be a mix of heating and cooling technologies – for example, heat networks in populated areas, standard heat pumps in new build situations, and, perhaps, hybrid for the futureproofing of existing technology which is known to be reliable and can be used easily by the consumer.
How heat recovery
systems work
Heat recovery systems essentially make the most of what is already there by drawing on naturally occurring warm air or water and getting it to work harder. It is often employed to reduce the heating and cooling demands (and thus energy costs and carbon emissions) of buildings. Heat can be recovered via a number of different systems such as through thermal wheels, plate heat technology, heat pumps – as in the case of the Rhoss EXP/HT, or more complex industrial processes. The technology for heat recovery systems has improved dramatically in recent years.
For example, some
Mechanical Ventilation and Heat Recovery (MVHR) systems claim to extract up to 90% of the heat from stale air before returning it to the fresh air circulating into the room to improve heating efficiency. Another option is to combine an MVHR unit with an integral heat pump , which can then also be reversed to apply cooling, offering a more efficient alternative to air conditioning.
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