Energy Efficiency and Variable Volume Hoods
A primary design feature of an energy-efficient laboratory is a variable volume fume hood and its control system, which maintains a constant, average fume hood face velocity during the hood's dynamic operation. According to Ahmed and Bradley (1990) energy savings will result from:
·the decrease in the exhaust flow rate from the laboratory, which results in a decrease in the amount of conditioned supply air needed; this reduces heating and cooling costs, and
·the decrease, as a function of exhaust flow rate, in the supply and exhaust fan horsepower requirements.
McDiamid (1990) adds another source of energy savings:
·the reduction in airflow when fume hoods are not in use (care must exercised to maintain proper room pressurization).
Energy savings from reduction in the loss of conditioned air can be dramatic: 60 to 70%, with two- to three-year paybacks possible. Initial HVAC capital costs will be lower because the installed chiller, boiler, and air-handling unit capacities can be smaller. There is also an opportunity, through right-sizing, diversity, and load management techniques, to operate equipment at higher efficiency levels. An example of a load management technique is an approach, sometimes referred to as "adaptive VAV", that lowers face velocity to 60 FPM when the hood is unoccupied. [Bentsen, 1997] [Wendes, 1990]
Features and benefits
Face velocity control
VAV Hood Retrofits