Innovators in Working Green HVAC Systems
When we design a job for our customer, green systems are always part of our proposal. A green HVAC system benefits the building owner, tenant and most importantly, our environment.
Variable Air Volume (VAV)
VAV systems maintain a constant air temperature of approximately 58 degrees. The VAV terminal meters air into the space at 58 degrees to maintain a constant space temperature. This system works well in buildings that require temperature control in multiple rooms and floors such as office buildings, schools and hospitals.
Variable Volume/Variable Temperature (VV/T)
VV/T was developed for smaller buildings. The system supplies cooling and heating through an electronically controlled damper system to maintain space temperature. This system only uses the amount of energy required to maintain space temperature.
Water Source Heat Pump
Water source heat pump is a water-cooled A/C unit with a reversing valve in the cooling system that allows the unit to supply heating or cooling. This system can operate at a balance point where approximately half the units are on heating and half are on cooling. At this point, no energy from a boiler or cooling tower is required. This system is very efficient.
|*The above systems require a source of energy such as boilers, furnaces, electric heat or standard cooling systems. Some applications of the above systems qualify for green LEED (Leadership in Energy and Environmental Design) points. LEED was developed by the U.S. Green Building Council (USGBC) and provides standards for environmentally sustainable construction points.|
The most widely recognized green system is geothermal. This is a water source heat pump system that uses ground wells, water in lakes or water wells. These systems need no other source of heat to heat the water when it’s cold or to cool the water when it’s warm outdoors. Most systems use circulating water wells. Well depths average from 150 feet to 500 feet. It takes about 150 bore feet (depth of a well) to handle one ton of air conditioning and heating. A building that requires 150-200 tons requires a large area for a well field. Good well field design allows 18 to 20 feet of spacing between wells.
Variable Refrigerant Flow (VRF)/Variable Frequency Drive (VFD)
In Europe and Asia the cost of electricity is three to four times more than the cost here in the United States. For around 25 years now, places such as these have been using a super high efficient “green” system called variable refrigerant flow (VRF) which is an air-to-air heat pump system. Instead of using the ground (wells) it uses the outside air. The compressors in these units operate with a variable frequency drive (VFD). This varies the flow of refrigerant. As the speed of the compressor slows down, the flow of refrigerant also slows down and reduces the capacity of the system. The unit follows the load of the space in heating or cooling without the compressor starting and stopping to maintain temperature. This system is quiet, has low maintenance and a long life cycle because it is not going on and off. Installation of this type of system is approximately 25% less than the geothermal system.