Jonathan Newell finds out how simulation, decentralised air handling and monitoring is bringing improved energy management to industrial cleanrooms.
Operators of cleanrooms in pharmaceutical, healthcare and advanced manufacturing operations are coming under increasing pressure to improve the efficiency of their facilities to more sustainable levels. In doing so, facilities managers are faced with the dilemma of striking the right balance between high levels of cleanliness and a reduced carbon footprint. Achieving that balance can provide significant rewards relating to reduced operating costs and a more sustainable operation.
To understand how one cleanroom supplier is helping to improve sustainability, I visited the Connect 2 Cleanrooms (C2C) factory in Lancashire and spoke to the company’s technical manager, Sam Armer.
Meeting the standard
Different industries have varying approaches to clean air facilities depending on regulatory norms. According to Armer, most of the time, pharmaceutical and medical companies have stricter controls because they take the normal ISO 14644 standard for cleanroom design, build and testing but then the GMP standard adds a few layers of compliance on top of that such as having an at rest acceptable level of contamination as well as an operational level.
Similarly in advanced manufacturing, there are various levels of stringency in the application of standards, particularly in highly regulated industries such as defence and aerospace. According to Armer, C2C’s model of being a design, build, install, test and monitoring/maintenance partner, as well as furniture, equipment and consumable supplier, is an advantage to such industries to ensure that their clean facilities are installed within the specification and are operated in accordance with continuing compliance.
On the issue of how sustainability fits 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 so 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 have a typically 2 year payback due to reduced energy requirements,” Armer explains.
C2C works with industrial partners and helps to meet the cleanliness requirements of the engineering team whilst 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 impacting 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 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 has clear energy efficiency implications. 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 filter units.
Perceived complications resulting from this approach are additional product and personnel boundaries at access and egress points, However, although there may be added zonal complexity, the benefits in terms of lower energy, reduced cost and easier compliance outweigh this.
Another approach used by C2C in designing for improved sustainability is the use of Computational Fluid Dynamics (CFD) as a simulation tool. 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, the introduction of turbulence dilutes the contamination and captures it in the return air or vents it to atmosphere. CFD can be used to assess the effectiveness of the introduction of turbulence and venting and such air flow models can fine tune the design of the facility.
CFD is also used to reduce the requirements for fan / filter units to prevent the facility from being over-specified, something that Armer is keen to avoid.
Current guidelines now don’t give recommended air change rates, which used to be in the design guidelines. This is an important factor since reducing air change rate reduces 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,” he explains.
Armer went on to explain that CFD is important to them in terms of the speed and accuracy of designing a facility that meets the specifications needed not just at installation but as an operational entity. “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 says.
Lighting plays an important role in cleanroom operations and also has an effect on energy efficiency as well as operational performance. Generally, cleanroom lighting luminance levels are such that they have high wattage requirements so the choice of lighting and the way it’s used is an important factor to consider for sustainability.
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, 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’s often a requirement for as little as 5% of the full level of lighting available. 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 those zones that are occupied. Taking such measures reduces energy bills and is another step to balancing the sustainability equation.