❱❱ Zone-based air management can have a significant effect on energy without compromising cleanroom standards, main image; ceiling mounted passive infrared sensors detect the presence of people and control the lighting according to occupancy, panel image; multiple fans/filters deliver air in the right condition to where it is needed across multiple cleanroom zones without central air handling units, below; and CFD is used at the design stage to model the air flow through the cleanroom and can even simulate particle movements to eliminate potential particle traps, below


CLEANROOM LIGHTING


operations such as dehumidification, which typically includes pre-cooling, heating through the de-humidification process and then de-cooling before re- introduction to the facility, which clearly affects energy efficiency. The C2C approach is to split the AHU constituent parts to deliver the air in the required condition to each zone independently through multiple fan filters. Perceived complications resulting from


Lighting plays an important role in cleanroom operations and affects energy efficiency and operational performance. Generally, cleanroom lighting luminance levels are high wattage so the choice of lighting and the way it is used is an important factor in sustainable design. Lighting choices are made on the basis


of light spread, the avoidance of blind- spots and shadows, fittings and the ability to maintain their cleanliness (particularly with high level lighting), ambient lighting requirements versus workstation lighting, the type and shape of luminaires and any effect that light fittings have on airflow. According to C2C, ceiling space is


prioritised for air filtration rather than lighting so options are often limited,


with these requirements for ultra- cleanliness, Armer tells me that there has traditionally been a lot of waste in clean facilities because the first and primary concern is compliance. This means that the procurement process is generally led by engineers. However, the ongoing running cost is run by a facilities team, which has an influence on the procurement. “They’re now helping with the procurement process, with energy consumption in mind. An example is specifying EC (electronically commutated) motors rather than AC, which, although more expensive initially, typically have a two-year payback time due to reduced energy requirements,” Armer explains. C2C works with industrial partners and


helps to meet the cleanliness requirements of the engineering team while satisfying the needs of facilities managers to reduce running costs.


DECENTRALISED AIR HANDLING The main cost in a cleanroom is the HVAC and C2C uses a decentralised approach to air handling, encouraging users to break down large areas into smaller zones of compliance. Historically, users have opted for


ballroom cleanrooms with large areas of stringent control despite the fact that only a small localised process area may need that level of control. By focusing on


specific zones at facility design level, energy can be significantly reduced without affecting compliance. Air handling units (AHU) are mainly


designed for single zone control. “These deliver a common condition from a pressure, temperature and humidity perspective so operating multiple zones with a single air handling unit causes a need to process and re-process air to satisfy local condition requirements,” says Armer. Taking this common condition and reprocessing it can take several


particularly for higher grade cleanrooms. Another factor that Armer mentioned


was the link between lighting levels and occupancy. He made the point that in some operations with low manning levels, there is often a requirement for as little as 5 per cent of the full level of available lighting. This provides an opportunity for reducing energy consumption by linking lighting not only to occupancy but also the position of the occupants within the cleanroom. C2C provides PIR (passive infrared)


sensors for people detection within the cleanroom and only provides lighting to occupied zones. Taking such measures reduces energy bills and is another step to balancing the sustainability equation.


this approach are additional product and personnel boundaries at access and egress points. Although this may cause added zonal complexity, the benefits of lower energy use, reduced cost and easier compliance outweigh this.


SIMULATION C2C also uses computational fluid dynamics (CFD) as a simulation tool when designing for improved sustainability. Using CFD, the designers can, for example, examine the introduction, generation and retention of particles and how filtering, process control and flushing can influence overall performance. For example, introducing turbulence


dilutes the contamination and either captures it in the return air or vents it to atmosphere. CFD can be used to assess the effectiveness of introducing turbulence and venting. Such air flow models can then fine tune the design of the facility. CFD is also used to reduce the


requirements for fans and filters to prevent the facility from being over-specified, something that Armer is keen to avoid. Current guidelines do not now give


recommended air change rates, though they used to be in the design guidelines. This is important since reducing air change rate cuts energy consumption significantly. “Now, it’s possible to reduce air change levels through improved monitoring and control and the effective use of CFD in the design process,” Armer explains. He went on to explain that the speed


and accuracy which CFD affords is important when designing a facility that meets the required specifications, not just during installation but also during operation. “Once the cleanroom has been delivered,


the client puts process equipment and people into the cleanroom and all this needs to be considered when designing the facility and CFD helps to achieve this more accurately and produce a balanced system of operational efficiency and technical performance that supports an organisation’s wider contamination control strategy,” he concludes. T&TH


December 2019 /// Testing & Test Houses /// 31


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