Authors: Dermot O’Driscoll, lead building services engineer, Biopharma Engineering Ltd
Heating, ventilating, and air conditioning (HVAC) systems represent one of the major energy consumers in a pharmaceutical facility, particularly for secondary sites and fill-finish facilities. The HVAC systems for these types of facility have been conventionally designed to provide a very conservative solution to the requirements for environmental control.
With operating costs and energy consumption considered a low priority in the design process, many HVAC systems are designed for excess air change rates, overly tight temperature and humidity setpoints and excess fresh air demand.
With the increasing demand within the pharmaceutical industry to reduce both operating costs and environmental impacts, there is a growing recognition of the need to improve the design and operation of the HVAC systems to maximise their operational efficiency.
While the focus of energy savings initiatives is often on the generation side – upgrading or replacing boilers and chillers, installing co-generation plants or switching to renewable energy sources – there is a great deal of scope to achieve significant improvements on the demand side with far lower capital investment and this should be the starting point.
In line with the current International Society for Pharmaceutical Engineering Good Practice Guide for HVAC, the starting point for optimising the HVAC for any pharmaceutical facility is a thorough assessment of the required environmental conditions. This risk-based assessment should concentrate on the fundamental requirements – what does the process require in terms of air cleanliness, temperature, humidity and recovery rate?
Setting arbitrary limits such as minimum air-change rates should be avoided, as this will tend to constrain the system design. The fundamental requirements should be identified and the air-change rates set to offset the gains in heat, moisture and viable particulate.
Optimising the operation of HVAC systems
Once the room requirements have been established, the operation of HVAC systems can then be optimised to maintain the required conditions while minimising the energy demand. A detailed survey of the HVAC setup – such as airflows, room-pressure profiles, duct pressure profiles, control strategy, room conditions and activities – should be analysed and an action plan should be developed to optimise the system operation, ranking the improvement measures based on potential energy savings, impact on operations and capital cost.
Typical low-cost measures will include reducing air-change rates, rationalising pressure profiles to reduce fresh air loads, optimising temperature and humidity limits, improving control sequences to utilise floating setpoints and deadband control.
More radical changes involve strategies such as changing three-port, constant volume chilled water and low-pressure hot water (LPHW) to two-port variable volume systems, adding air flow meters and air-volume control to allow night setback of airflows and use of free cooling while maintaining pressure profiles, adding fresh air pre-treatment and heat-recovery systems.
In Biopharma Engineering, our HVAC and automation engineers have both site and design office experience of a wide range of HVAC retrofit and optimisation projects across a wide range of bulk active pharmaceutical ingredients (APIs), secondary fill-finish and biotech facilities. We can facilitate the initial requirements and risk assessments and project scope development of what needs to be completed as well as deliver the capital equipment changes.