We all know that HVAC has the highest contribution to the overall energy spent in a building. In a standard pharmaceutical facility, it can consist of up to 60% of the consumed energy.
Optimizing the energy management in HVAC and related black utilities can provide substantial savings in terms of money and CO2 tons released to the atmosphere. In this post, we are going to discuss a few tips on energy savings in Pharmaceutical HVAC design and how to reduce energy consumption. The challenge is double because we should not compromise GMP regulations or safety requirements.
LEED (Leadership in Energy and Environmental Design)
LEED is a green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council (USGBC), it includes a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighbourhoods, which aims to help to building owners and operators be environmentally responsible and use resources efficiently.
The LEED rating system has seven areas of concentration: Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, Indoor Environmental Quality, Innovation in Design Process and Regional Priority. Projects obtain credits in these areas to achieve certification.
Ways to reduce energy consumption in pharmaceutical HVAC
Reduce the Outdoor airflow
Normally, we design the outdoor airflow to satisfy overpressure ventilation requirements. A rule of the thumb for concept design stages is to set the airflow requirements about 10-20% of the total air supply flow, and sometimes this premise is maintained until the final design. The reality is often that in most cases we require less than 10%. So, accurate analysis of the required airflow and later balancing of the system can reduce substantially the energy consumed for the make-up air.
Use of high-efficiency fans
Any fan should be provided with a VSD (Variable Speed Drive). This is the minimum consideration in terms of energy saving. Together with a flow transmitter, the system will control the required flow as the filter get clogged. Efficiency minimum IE4 for the motors is an excellent choice. The price of these motors is higher, but you should bear in mind that the operation cost during the fan lifecycle exceeds widely the purchase cost.
EC stands for electronically commutated. An EC fan has a brushless, permanent magnet DC motor with onboard electronics available for controlling a fan rotor. The efficiency class is the highest, IE5. The only problem is that a single fan can hardly provide the high static pressure normally required in pharmaceutical applications. Fan manufacturers solve this by providing a fan array in parallel. On the other hand, this allows the possibility to furnish redundancy in case of failure of one of the fans.
Avoid excessive Air Changes per Hour (ACH)
You can find the definition of ACH in the post About Air Changes. There is an industry-standard establishing a relationship between GMP classification and Air Changes. In most cases, this is achieved, but note the following:
- Energy consumption increases as per ACH does
- Optimal ACH depends on particle generation velocity
- By increasing ACH you can reduce the recovery time
In some companies, there is the wrong assumption that by increasing the air change rate you will get a better quality of air. This is true only partially, so we should apply a scientific rationale to determine the optimal ACH.
Rationale outdoor temperature design
As discussed in our post Determining Outdoor Design Conditions, outdoor design conditions have a big impact on building energy consumption. This consumption is higher as the outdoor air percentage used in our systems is higher.
Oversized outdoor conditions prompt us to size up cooling/heating equipment, but with the warranty that we will keep indoor conditions within the established limits.
On the other hand, undersized conditions will require less installed power, but during hottest/coolest days of the year indoor conditions suffers.
. Tightness is important!
Cleanrooms are usually submitted to positive differential pressure, as discussed in the post Leakages Calculation. In order to achieve this differential pressure, a makeup airflow is necessary to provide to the system. To condition, this airflow is expensive, including humidifying or dehumidifying, so we should decrease the leakages through our system that will become energy losses:
- Provide and test good airtight ductwork construction, as described here Pharmaceutical HVAC Ductwork
- Provide good airtight cleanroom construction, according to VDI 2083
- Avoid unnecessary high differential pressure between rooms. 5-10 Pa between the same classification rooms and about 15 Pa between different classification rooms are normally accepted.
Schedule unoccupied conditions
Pharmaceutical HVAC systems usually run 24 hours per day, and only stop for a few weeks per year during shutdowns. But in some cases, processes only take place for one or two shifts (8-16 hours out of 24). If this is your case, a good energy-saving measure is to modify the HVAC system setpoints during non-occupied periods by:
– Decrease the supply airflow (decrease ACH). As there are no people working and processes ongoing either, the particle generating rate is lower.
– Increase temperature setpoint in cooling mode, say 2 degC, as there is no need to satisfy comfort nor process conditions.
– Decrease temperature setpoint in heating mode.
It’s important to remark that if you apply these actions you should validate the occupied – non occupied switchover conditions.
Process challenges
We must not lose sight of the HVAC reason of being: to protect the processes and/or the personnel. At this point, we clearly know that with the higher level of cleanliness we require, we will need more amount of energy. And in parallel, as bigger as our cleanroom is, we will require more energy as well, independently of its classification.
Based on these premises, in terms of energy reduction, we should ask ourselves about process constraints, like for example:
- Can we design the process in a more reduced space without compromising GMP and/or ergonomics?
- Can we use closed processes? Closed processes usually require less classification level.
- Is it feasible to use RABS / Isolator technology? If aseptic processing can be carried out in a RABS or Isolator, the surrounding area could be designed in a lower classification.
- Try to install large heat-generating equipment or pieces of equipment outside the cleanroom. This will reduce the need for cooling, and we will need only to provide good ventilation
