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H O T W AT E R
The future of storage
By Yan Evans, technical director of Andrews Water Heaters and Potterton Commercial
W
hilst there is an Though these are often first fired storage water heaters. available that produces heat as The next logical step is to offered through the use of
increasing need choice units in the food and Design engineers are once opposed to electricity, there is consider an LZC solution to direct-fired water heating and a
to understand other process industries, they again having to satisfy the the primary requirement for work on each aspect of the solar thermal cold water pre-
which of the have proved a popular architect’s and developer’s stored water. system i.e. a low carbon heating heat system. However, it might
available Low alternative for system designers specifications but this time in This type of energy cannot be solution with separated low be possible to effect further
and Zero Carbon (LZC) in many types of commercial relation to energy saving and used instantaneously, whether carbon hot water solution. carbon footprint reductions,
Technologies can work together buildings. reduced carbon solutions that generated by solar thermal In this scenario, using solar depending on the application.
to optimise system energy The separation concept and meet increasingly stringent arrays, either via flat plate or thermal solutions to pre-heat Although ground source heat
efficiency, it is also important to the use of high recovery direct- building regulations and evacuated tube collectors, by the cold water feed into a direct- pumps are electrical appliances,
go back to basics with regard to fired water heaters found favour planning approvals with caveats ground source or air source fired storage water heater can they are classed as renewable
the design of the conventional with architects initially because for inclusion of 10-15% of LZC heat pumps, or by Combined result in a dramatic reduction in technology because energy in
part of the hot water system and it reduces the size of plant room technologies. So now energy Heat & Power (CHP) products. the amount of gas required to the ground is used to initiate
consider what is the most required due to reduced stored savings, running costs and It therefore has to be stored so raise the temperature of water and sustain the operation of the
effective combined solution. water requirements, especially carbon footprint are just as it can be drawn upon as and from a cold water inlet from refrigeration cycle. Where a
For many years now if the system is decentralised important as space premiums. when it is needed and, to date, a around 10°C to a hot water building has sufficient base
separation of the heating and with units installed close to the A heating system that can meet well insulated water storage outlet of 60°C. Seasonal thermal load to support the
hot water loads has been point of use. Whichever way, the criteria on efficiency and cylinder is the preferred variations in the available operation of say, a ground
recognised as the most energy the amount of sales floor area, suitability for integration with method. This enables irradiation mean that the source heat pump and a small-
efficient way of delivering these or lettable space, can be the new and emerging LZC conventionally generated contribution delivered by the scale CHP unit, the latter could
services in commercial, maximised. technologies will have a positive energy to be used on an ‘as solar thermal solution in the generate the power needed to
industrial and public buildings. bearing on all these objectives. required’ basis, to top up the summer months is far greater operate the heat pump. This
Whilst the principle was first Heading back to stored We are therefore most likely to temperature of the stored water than in the winter. would result in a significant
introduced when direct gas- water see a return to a higher during periods where demand Sizing the solar thermal reduction in the overall carbon
fired storage water heaters It was perhaps fortuitous that proportion of commercial exceeds the capability of the system so that during the footprint of the plant room.
came onto the UK market, it the industry developed in this heating and water heating LZC technology. Water storage summer there is little or no Similarly, it may be possible
proved just as effective when way because it happens to lend systems that incorporate a (indirect cylinders or buffer primary heating appliance to use a CHP unit to power an
instantaneous or constant flow itself particularly well to higher degree of hot water vessels) can also assist in operation could enable air source heat pump that is
type appliances became an integration of LZC technologies storage. preventing engine and condensing storage water pre-heating the cold water into a
option for larger load and higher with today’s high efficiency This is because behind every compressor based products heaters, with gross efficiencies direct-fired water heater, as an
peak demand applications. condensing boilers and direct LZC technology currently from cycling on and off of up to 98%, to work in alternative to a solar thermal
too frequently which could lead harmony with solar thermal solution. This could be
to premature component solutions to deliver an ultra-low advantageous where, for
failure. carbon hot water generating instance, the solar thermal
solution. route is not an option because
Integrating technologies there may be insufficient roof
A typical example of the Cutting carbon and costs space for the solar arrays or
progression is a building that 30 What could be done to reduce lack of other space with suitable
years ago would have been carbon emissions and save south facing orientation to
most likely to have had two running costs on the space maximise the performance of
large cast iron boilers, to allow heating system? A ground the solar collector array.
for standby operation and source heat pump could be
maintenance shut-down. This installed to satisfy the base Selection and control
would have been oversized for thermal load, with conventional From just these few examples it
the average heating and hot high efficiency condensing can be seen how a hydraulic
water load of the entire building boilers providing schematic for a plant room that
to allow for peak differentials supplementary heat during includes conventional fossil
and would fire in summer periods of peak demand. fuelled appliances working in
months to heat the hot water Ground source heat pumps harmony with suitable LZC
calorifier only. harness the solar energy stored technologies can be designed to
The monumental in the earth from incident solar optimise plant room
inefficiencies of these times rays, which is captured through performance and carbon
have gradually been addressed ground loop pipes buried within emissions. Caution is however
on both the heating and hot a trench or deep bore holes. essential, as the equipment
water side by the introduction of These heat pumps achieve the needs careful selection – so that
independently fired water best performance when operational conflict does not
heaters and the more recent delivering low-grade heat to occur. As well as considered
development of smaller, much say, an underfloor heating and informed equipment
more compact yet high output system. selection, the appropriate
commercial boilers, which can This type of installation control of the operation and
operate in modular formats and would maximise performance interface of a variety of heat
now have the benefit of through water outlet sources is critical to the
condensing technology. temperature control, enabling success of such installations.
Increasingly, solar thermal heating boilers to be used for A well thought out control
systems are being utilised in the higher temperature radiator strategy will ensure that energy
conjunction with a boiler or a circuits only as required. efficiencies and carbon dioxide
direct fired water heater and a This provides a low carbon reductions are maximised
storage cylinder to reduce space heating solution to with no compromise in the
primary fuel consumption and compliment the low carbon hot provision of space heating and
carbon emissions. water generating solution hot water.
24 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2009
VISIT OUR WEBSITE: www.bsee.co.uk
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