BSEE


COMBINED HEAT & POWER


Comfort cooling unit reimagined with increased energy saving systems


Artus went on to find success in landmark commercial projects such as the WeWork flexible office space at 10 Devonshire Square in central London, where efficient and quiet cooling along with aesthetics, were key considerations. Two years on, and the team at the Yorkshire-based company has continued their work with Arup, to develop the next generation of comfort cooling for commercial and residential spaces.


A Efficiency


Artus™ supplies the same cooling load with dramatically lower energy consumption than alternative comparable systems. This offers the opportunity for operational savings and has a dramatically lower environmental impact, which is rewarded by way of more BREEAM points than its alternatives.


. The energy savings are greater than those achieved by using active chilled beams, but at a low installation cost, comparable with fan coil units


Artus Advantage  Efficient water temperatures


Here, Darren Farrar, marketing manager of Airedale International, explains how these new developments can be employed to meet evolving industry demands:


Large heat exchanger


Artus has a large coil on three sides, giving a large face area and a more effective heat exchanger. The low fan velocity, a quarter of typical FCU speeds, gives a very low pressure drop, and requires minimum fan input. Instead of a specific fan power of around 0.23 watts/litre/second for a typical fan coil unit, the SFP for Artus is 0.08, a saving of 65%.


Model building used for energy calculations


Our energy analysis has been done using the relatively simplistic UK Building Regulations Part L (BRUKL) calculation. This is a compliance tool, suitable for comparing systems, but not suitable for producing absolute figures. The base case was a building that was just compliant with Part L 2013, and with design assumptions based on the British Council of Offices Guide. We then tried out the effect of improvements from various schemes, such a standard Fan Coil System, Artus, Artus Advantage and Active Chilled Beams. The layout of Artus units for a floor of the model building, with conventional temperatures for cooling (6/12F&R) and heating (60/50F&R), is shown below. Control zones conforming to the BCO Guide are shown in dotted lines, with one Artus per control zone. The average density is 29.6m2 per unit (78 units).


iredale International, working in partnership with inventor Roger Olsen of Arup, first launched its original Artus™ to solve some of the issues associated with inefficient and cumbersome comfort cooling systems.


Energy saving


The BRUKL calculation gives the regulated energy, of which the energy cooling, heating and terminal units is a part – 30% in the case of a standard FCU. The pie chart illustrates this.


The graph compares the energy used by the four systems, with a standard Fan Coil Unit as 100%. The energy needed for circulating pumps and ventilation systems is not included on the assumption that it will be similar for all of the systems.


Layout of Artus units with conventional chilled water temperatures


Artus Advantage is a design technique which uses higher water temperatures that require less energy to produce cooling and heating. With elevated cooling water temperatures (e.g. 14/17Flow & Return) it is possible to use chillers with far better efficiencies; free/adiabatic cooling; ground source heat pump/chillers; or even direct use of groundwater with no chiller required at all. For heating with heat pumps there is a similar pattern. The efficiency of a heat pump working with warm water (35/30 F&R) is much better than if it produces hotter water (60/50 F&R) as it does not have to work so hard.


We tried the effect of using Artus and Artus Advantage by doing energy modelling on a simplified model building of just under 10,000m2 floor area.


Standard fan coil unit


Terminal unit specific fan power (W/lit/sec) Unit density, m2/unit Cooling source


0.23 31.25 Air cooled chiller


Cooling water temps F&R  6/12 Chiller/ adiabatic cooler SEER 3.79 Heating source pump


2.56


Artus (conventional Artus Advantage. FCU temperatures). Single coil Two coil option.


0.08 29.6


Air cooled chiller 6/12


3.79


Heating water temps F&R  60/50 Heat pump SCoP For model 10,000m2


building BRUKL (kWh/m2/year) 43.71 2.56 40.70 0.08


Active chilled beam changeover option N/A


21 (for Artus Pro: 29.6) TBC AC chiller + free/


10


adiabatic cooling adiabatic cooling 14/17 10


AC chiller + free/ 14/17


Air source heat pump Air source heat pump Air source heat pump Air source heat 60/50


35/30 4.5


35.46


60/50 4.5


36.52


22 BUILDING SERVICES & ENVIRONMENTAL ENGINEER OCTOBER 2020


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