COOLING | HYBRID AIR CONDITIONING the trade off is that the cooling capacity drops off at these temperatures. If you were to design a scheme to run all year round at elevated cooling temperatures, you would, in theory, need almost double the number of units or FCUs. However, a proprietary software and control system has been developed to provide a cost-effective solution for applications designed to run at 14C/19C but with the capability of achieving peak demands by reducing the cooling temperature to 6/11C. We realised that, for most of the year, 14C/19C is fine, because the peak cooling load only occurs for about 50 hours per year; for nearly all the rest of the time, it is running at almost 50% load, says Olsen. The software overlay and intelligent control system looks at all of the units to see how hard they are working, to optimise flow temperature through the chillers using bespoke algorithms. This allows the system to drop the cooling water temperature to 6C/11C during the 50 hours of peak demand without compromising system energy efficiency for the remainder of the time. This ensures chillers are always running at the higher cooling temperature possible leading to high seasonal COP on the central plant. Under current Breeam for refurbishment and fit-out criteria, the 10% energy saving in changing from a compliant FCU to these units would give at least three Breeam points. With the bespoke controls optimisation and reporting software Results of simulated energy use comparing traditional AHU with novel unit 15 14.54 2.48 13 Energy (kWh.m-2 per year) 11 9 63% reduction in overall energy 6.04 7 5.31 5 3 1.41 6.02 2.29 1 -1 1.61 Baseline Artus with proprietary software MODELLED ENERGY USE IN AN OFFICE The team carried out an energy simulation on a 10,000m2 model building, designed to comply with Part L of the Building Regulations 2013. The modelling showed the novel units achieved a 14% reduction in total building energy, and a 63% energy reduction in the elements used for heating and cooling. Auxiliary (terminal units) Cooling Heating Total installed, to maximise energy savings in operation, it is possible to achieve up to seven. There is big benefit in heating when using a single coil as the large coil area required for cooling is ample for the heating demand. If you run the heating circuit at 80C flow/70C return, the coil will be massively oversized, says Olsen. However, he adds, the advantage of the oversized coil is that it opens up the possibility of using heat pumps for example, to run the heating system at 35C, and still get the heating you need from the one coil. Artus also offers a twin coil option more akin to a traditional FCU for where a single coil system is not appropriate. Sayce says the unit has been popular for healthcare applications, because everything that needs to be accessed, including the filters, can be reached from below by dropping the units hinged front face. In fact, the units shallow depth, when compared with a FCU, means that on a tall building of 12 storeys or more, with a maximum development height the use of these units could allow developers to squeeze in an additional floor. If a developer can add 7-8% to the floor area of a development simply by using a different HVAC system, it could impact the viability of some developments. The unit is also expected to be popular for use in cooling high-end apartments, where its low noise level, combined with its shallow nominal 200mm depth and simplified returned air paths, means it can be accommodated relatively easily without the need to increase ceiling depths. With several successful installations completed, Olsens daydream has been realised. But, hes not put away his blank sheet of paper. In response to Covid-19, hes working on a version of the unit that recirculates and cleans the air. Watch this space.... CJ The most sustainable e Commercial Air S Source Heat pump Titan Sky The Superior Natural Choice Air Source Inverter Heat pump Natural refrigerant (R290) Heating g Capacity: 30-200 kWMax H Hot water production: +63C Minimum Ambient:-20C SCOP: up to 4.12 Lowest Total Equivalent Warming Impact (TEWI) Unbeatable use of Primary energy thanks to Inverter technology No Ozone Layer impact & Nearly Zero Global warming potential Optimized Low Refrigerant Charge design 54 November 2021 www.cibsejournal.com CIBSE Nov21 pp51-52, 54 Artus.indd 54 22/10/2021 18:14