Sean Convery, P.E., Cator, Ruma & Associates, Co.
As sustainability in the architectural/engineering/construction (A/E/C) design industry continues to grow in significance, it is now more vital than ever to be progressive in design. The very nature of laboratories presents our industry with a blank canvas (or Petri dish) of opportunity to devise imaginative designs that will move our trade as a whole toward sustainable goals. Oftentimes, the most ingenious ideas are generated by improving upon tried and true systems. This approach offers creative solutions that are integrated with reliable technology to seamlessly combine innovation and usability. To that end, in the following abstract, we would like to focus on two specific methodologies that increase laboratory energy efficiencies and operational characteristics by applying common technologies in new ways: point of use cooling and heat recovery heat pumps. Though simple, these methods contribute to the improvement of the overall heating, ventilation, and air conditioning (HVAC) system efficiency to build a more sustainable laboratory.
The first method to present is to apply point of use cooling at spaces with high heat-rejecting laboratory equipment, in lieu of utilizing the main air handling that must then exhaust the conditioned air after one use. Laboratory designs are moving toward putting high heat gain equipment (-80°C freezers, etc.) into equipment/freezer rooms or linear equipment rooms. Since these types of spaces are constantly cooled, taking advantage of re-circulated air from fan-coil units or other point-cooling devices will reduce/remove supply and exhaust air from the building systems, which saves fan energy, cooling energy, and heating energy. In dense -80°C freezer rooms with eight or more freezers, it has been leaned that these rooms could best be served in a manner similar to data centers: provide cold air supply down the middle between the two rows of freezers and locate return/exhaust grilles around the perimeter to allow the heat to rise straight up from the back of the freezers and out of the space. If the return/exhaust is simply at the opposite end of the room by the thermostat, the hot air can falsely load the thermostat as well as provide a temperature gradient across the room, thereby unnecessarily triggering the cooling system.
The second approach to present revolves around minimizing air pressure drop on heat recovery systems and increasing the amount of time the heat recovery system remains online. This can be accomplished by avoiding the typical run-around heat recovery system and instead utilizing a heat recovery heat pump. This heat pump can be used to reject the heat to the heating system rather than the air-handling unit (see Figure 1: Heat Recovery Heat Pump One-Line Diagram). This provides heat for the reheat system, which operates year-round in most laboratories, whereas a conventional run-around loop has to shut off when outdoor air temperature is between 45°F and 85°F because the parasitic losses of pumping exceed the recovered energy. Also, the exhaust coil for the heat pump system can be a four-row coil in lieu of a six- or eight-row coil (normally found in a run-around system), thereby reducing the pressure drop from 0.7" to 0.4" on a typical system.
|Figure 1: Heat Recovery Heat Pump One-Line Diagram|
Another way to use the heat pump is in a water-to-water application if there is a simultaneous heating and cooling requirement. In this conception, the heat pump is placed in a side stream configuration on the chilled water return and on heating water return systems, which results in pre-cooling the chilled water return and pre-heating the heating water return on the way back to the central plant.
Though often not thought of as the most consequential system in a laboratory, HVAC and exhaust systems have the potential to present forward-thinking A/E/C teams with many possibilities to develop energy-efficient and sustainable designs. Simplicity can give rise to revolutionary solutions. The two approaches discussed in this abstract—point of use cooling and heat recovery heat pumps—are both inventive ways to apply established technologies in laboratories to increase HVAC and exhaust system efficiency. By combining the technologies we know best with a bit of vision, we can continue to meet the challenges of a constantly-changing built environment in the same spirit in which our industry has always been grounded—earnest ingenuity.
Sean Convery joined Cator, Ruma & Associates, Co., a mechanical/electrical/engineering consulting firm of 80 persons, in 1995, and worked his way from a graduate entry-level engineer to a senior associate in the mechanical department. He has a Bachelor of Science in mechanical engineering and is a professional engineer in Colorado. Mr. Convery has a broad array of experience in the design of mechanical systems focusing on higher education campuses, wet and dry research laboratories, utility and service infrastructure upgrades, and central plants. He has an extensive, successful relationship with Colorado State University, having completed over 65 projects, the majority of them laboratories including Biosafety Level 3 (BSL-3) laboratories. Laboratories at Colorado State University include the BioEnvironmental Hazards Research Laboratory, the Rocky Mountain Regional Biocontainment Laboratory, and the Veterinary Diagnostic Medicine Center, all containing BSL-3 laboratories. More recent laboratories include the Colorado State University Research Innovation Center (LEED® Gold pending), Front Range Community College Sunlight Peak Science Building (LEED Gold pending), University of Colorado Boulder Systems Biotechnology Building (LEED Gold pending), and University of Colorado Denver Research Complex Energy Efficiency upgrades. Mr. Convery has also received Engineering Excellence Awards from the American Council of Engineering Companies in Colorado for his award-winning designs at complex laboratory campuses. In 2002, he was a spokesman at an ASHRAE Engineers' Technical Conference in Denver regarding the BioEnvironmental Hazards Research Laboratory.