Gordon P. Sharp, Aircuity, Inc.
Analyzing a laboratory's HVAC energy consumption is often quite difficult due to the unique characteristics of laboratories. Conventional commercial or widely available energy analysis programs are typically not the best approach, particularly when different control strategies and systems are employed to reduce energy use. On the other hand, custom spreadsheet- and product-based energy analysis programs often do not model the complex interactions between the many energy savings approaches that are often used together.
However, a holistic laboratory energy analysis and return on investment tool has recently been developed that evaluates the combined savings of multiple laboratory energy efficiency measures such as chilled beams, heat recovery, demand-based control, variable air volume (VAV) fume hood control, evaporative cooling, and other approaches using typical meteorological year 3 temperature and humidity data for 1,700 United States and international cities. In addition to energy savings, the analysis tool can model the impact on the first cost of various strategies. One of the benefits of the tool is its ease of use and ability to rapidly analyze a laboratory design.
For at least the next six to nine months, this tool is being made available to the laboratory design and operations community on a complimentary basis; after that it may be available from the International Institute of Sustainable Laboratories (I2SL) for a reasonable annual license and support fee. The only requirement to obtain this tool is to attend a six- to seven-hour-long hands-on training class on proper use of the tool, taught by the tool's creators.
The presentation at the Labs21 2012 Annual Conference provided examples of how the tool can be used to help compare and determine the most cost-effective and impactful energy savings approaches for a laboratory project's design given its climate, energy costs, and many other factors.
Holistic View of the Relative Impacts of Multiple Energy Saving Approaches
Figure 1 shows a holistic view of some of the most impactful laboratory energy savings approaches, with the lower approaches having the greatest impact and the higher approaches typically having the least impact. This figure also illustrates that the foundation for laboratory energy savings is usually a VAV control system that by itself may not enable significant savings but is required to enable other approaches to reduce laboratory flows, save energy, and even lower capital costs. The next most important energy savings approach (and often a further enabling approach for the approaches above it in the energy pyramid) is demand-based control and, when relevant, the related use of low-VAV fume hood minimums.
The Labs21 conference presentation provided a case study of the energy savings impacts of many energy-saving approaches for a typical laboratory in the Boston area. This analysis assumed a baseline case with a fixed 6 ACH minimum air flow and energy costs of $0.125/kWh for electricity and $1.00/therm heating costs for a facility with 50,000 square feet of net laboratory space.
Impact of Demand-Based Control for a Boston Laboratory
Figure 2 shows some of the results of the analysis. The baseline case using 6 ACH shows an HVAC energy use of $390,000. The proposed case using demand-based control reduced the energy use by about $200,000 or 51 percent.The presentation went on to show the relative savings of the other energy-saving approaches shown by Figure 1. However, as is typically the case, the most impactful approach to saving energy was reducing the airflow with VAV control combined with demand-based control.