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UNIVERSITY LABORATORIES Energy efficiency under the microscope
he energy consumption of laboratories is often more than three to four times that of offices on a square metre basis. This can mean that laboratory buildings are responsible for between 50% and 80% of the total energy-related (non-residential) carbon emissions of research-intensive universities. Reduction of energy usage in the laboratory requires extremely careful consideration. It is essential that inadequate air management does not compromise health and safety. The integrity of testing and research carried out in the laboratories also relies on the correct environmental conditions being maintained. Significant energy savings can still be achieved, however, by tackling air handling of lab- specific equipment such as fume cupboards.
T Fume cupboard efficiency
Ian Thomas, Product Technical Manager – Air Products, TROX UK, explores the energy‐saving opportunities in university laboratories and how these can be achieved by tackling air handling of lab‐ specific equipment such as fume cupboards.
When fume cupboard sashes are open, the volumes of air required to maintain a safe working environment for laboratory personnel increase significantly. For example, a 900mm wide cupboard with a maximum sash height of 500mm and face velocity of 0.5 m/s would extract approximately 225 l/s of conditioned air from the room. This would be fixed on a constant volume cupboard, whereas on a variable volume cupboard the minimum air volume could be around 55 l/s when the sash is down. Converting from constant volume to variable volume would therefore save 170 l/s when the sash is in the down position for a single cupboard.
Energy wastage often occurs because sashes are left open unnecessarily when laboratory personnel are not working at the fume cupboards. Visual reminders in the laboratory can help, but there are also devices such as PIR (passive infrared) sensors or auto sash closers capable of saving energy automatically.
When the PIR sensor identifies that no one is present at the fume cupboard, for more than the set time, it will trigger a visual or audible alarm to indicate that the sash has been left up. The auto sash closer can work in conjunction with this to close the sash automatically, thereby returning the fume cupboard to reduced air flow and preventing it from drawing conditioned air from the laboratory unnecessarily. If the fume cupboards were installed some years previously, simply retrofitting the control technology on the fume cupboard could also improve energy efficiency.
Laboratory air management systems
A more comprehensive method for improving energy efficiency is the installation of a room air management system to automatically control all input and extract air for the laboratory. This is increasingly popular as it ensures the room balance (and therefore operator safety) is maintained automatically. All devices are connected locally (within the room) by a digital network. There are three airflow drivers: uThe number of air changes necessary to meet the safety requirement.
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A more comprehensive method for improving energy efficiency is the installation of a room air management system to automatically control all input and extract air for the laboratory.
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uTROX EASYLAB’s automatic exhaust air optimisation will enable the room extract VAV unit to close when the required room air change rate is being met by the fume cupboards or other technical extract in the room.
uThe supply air required for cooling/heating the laboratory to a comfortable temperature for occupants. uThe supply air needed to replenish air exhausted by fume hoods.
The room air management system (for example TROX’s EASYLAB system) manages the supply and extract controllers in order that they respond rapidly to changes in extract volumes by the technical extract (for example fume cupboards) to ensure the correct air flow balance and room pressure at all times.
This approach to lab air management has a significant impact on energy efficiency, as it prevents unnecessary supply of conditioned air to the space. Room air management systems have the added advantage of offsetting one form of exhaust air against another. For example, if the fume cupboards are open and extracting air, there is not the same requirement for the room system to carry out this process. By scaling down room exhaust air extraction in line with fume cupboard extraction, the room air management system is able to prevent over- supply and extraction of conditioned air from the space. TROX EASYLAB’s automatic exhaust air optimisation will enable the room extract VAV unit to close when the required room air change rate is being met by the fume cupboards or other technical extract in the room. This further reduces the total extract volume.
It is also important to explore opportunities to reduce energy consumption, without impacting safety, by reducing air change rates when laboratories are unoccupied, harnessing occupancy sensing technology and local overrides.
www.troxuk.co.uk
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