Controlled environments, including laboratories and cleanrooms, consume tremendous amounts of energy, making them highly visible targets for efficiency initiatives. Comfort, safety, and quality control objectives often restrict building owners’ and facility managers’ ideas about potential energy savings. Standard operating practices and rules of thumb have morphed into pseudo-code requirements. As research begins to question these practices (and even standards), designers and operators grapple with the ultimate challenge: becoming more energy efficient without compromising the performance of critical facilities.
The energy savings opportunity in critical environments seems obvious. On average, labs consume 5 to 10X more energy per ft2 than typical office space, with highly specialized facilities such as vivariums and cleanrooms greatly surpassing those averages. The single largest energy component within these facilities is ventilation, which can account for 45 to 65% of energy use. Typical research facilities operate at eight to 15 air changes/hr (ACH); vivariums often operate at 12 to 25 ACH. Cleanroom rates begin at 15 ACH for Class 8 environments and top out at an amazing 750 ACH!
Variable air volume (VAV) control systems equipped with demand control ventilation (DCV) solutions are now widely recognized as a successful way to balance energy efficiency with comfort and quality objectives.
The promise of DCV
DCV involves highly sophisticated environmental sampling and monitoring infrastructure. With DCV, air samples are routed to special sensors that analyze conditions and then interface with the building management system, which automatically adjusts airflow in response. The people responsible for indoor environmental quality (IEQ) in the facility are the ones who determine the appropriate parameters. Airflow is tailored to the needs of each specific room or zone, rather than general “rules of thumb.”
Fig. 1. A graphic “dashboard” interface is an easy tool for helping facilities gauge the financial effect of adjustments in air change rates. All graphics courtesy of Aircuity
By monitoring individual room conditions and varying make-up air volume based on those conditions, building owners are realizing significant energy savings while maintaining a high standard of IEQ.
Despite the success to date of DCV deployment in multiple types of facilities, questions remain:
• To what extent can DCV be used to optimize energy consumption without compromising performance and quality?
• How can managers, users, researchers, and quality assurance personnel be confident about the conditions of their facilities when implementing energy-efficiency initiatives that seek to lower their air change rates from previously established constant volume rates?
During the past few years, ideas about critical-environment management have undergone a sea change. Rather than prescribing strict operational processes, regulatory and accreditation organizations have begun to adopt performance-based metrics that involve actual environmental conditions, leaving the “how to” process of achieving those performance metrics to facilities personnel.
Research labs (such as conventional “wet” chemistry and biology labs) have been highly involved in this trend, and their experiences will eventually begin to influence developments in other types of critical environments, including cleanrooms. Opportunity and confusion have both arisen, as researchers and facilities personnel strive (and sometimes struggle) to agree on management protocols that will consistently meet or exceed stipulated environmental conditions. The door has been opened to new approaches that may include energy-efficiency projects, but how best to proceed?
Data, data, data
Information services that can alert facilities personnel regarding the condition and performance of the spaces they manage will help build the confidence required to continue the expansion of DCV. In fact, the availability of information services that can document compliance with IEQ performance metrics may well be the driving incentive for implementing a monitoring and control strategy.
Fig. 2. A “comfort analysis” for a vivarium includes a shaded box indicating the acceptable range of temperature and relative humidity parameters for a particular species (in this case, mice). The dots represent real-time sampling of temperature and humidity. Dots clustered in the box indicate acceptable conditions; the other diagram indicates problems.
Information solutions must be multi-faceted, providing multiple perspectives relevant to different audiences. EH&S professionals will want to examine IEQ and building performance data, while energy managers will likely be more interested in monthly savings and identifying issues that may be impacting those savings.
Other key attributes of effective monitoring systems include:
• Visual displays of analyzed information, not just raw data.
• Short- and long-term trend information.
• Alerts for high-priority issues based on persistence or pervasiveness, not just simple parameter thresholds.
• Automated summary reports that can provide high-level views of how a facility is operating.
Information services have evolved to help organizations manage their critical environments proactively and report performance information in meaningful ways to building owners, facility managers, EH&S personnel, and accreditation and regulatory bodies.
Graphics improve understanding
The diagrams on these pages illustrate some easy-to-understand, yet sophisticated, IEQ graphics. Fig. 1 is a dual display showing both the flow reduction over the previous month and the average ACH rates during that period. ACH monitoring is important to help building owners meet regulatory guidelines and determine if energy savings objectives are being reached, and to give managers, users, and/or researchers peace of mind that ventilation rates are appropriate for the conditions.
Continuous monitoring and reporting can also provide tremendous insight, showing how activities within a space directly affect the amount of airborne contaminants.
Combining parameters on a graph can quickly and easily illuminate adherence to (or departure from) prescribed IEQ boundaries. Fig. 2 comprises a “comfort analysis” graph in a vivarium, plotting humidity and temperature measurements. The shaded box reflects the acceptable ranges for a particular species; in one of the diagrams parameters are being met, but in the other, something has gone awry.
How far can DCV extend into critical environments? Given the fact that even a modest air change improvement of 10% can reduce energy consumption by almost 27%, the boundaries will continue to be tested. The new ANSI Z.9 regulation for fume hood airflow requirements resulted from years of analysis that challenged the status quo. Research relevant to controlled environments is underway now; the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has recently commissioned a study to determine how DCV may be applied to cleanrooms.
As DCV applications expand, monitoring and reporting capabilities will play an increasingly important role in helping companies, institutions, and other organizations achieve significant greenhouse gas reductions while maintaining high-quality, high-performance critical environments.
Chuck McKinney is VP/marketing for Aircuity Inc. The company’s patented OptiNet technology offers demand-based control solutions for both critical environments and commercial offices, significantly reducing energy consumption and greenhouse gas emissions while maintaining quality parameters.
This article appeared in the February 2013 issue of Controlled Environments.