A recent study published by Bloomberg Finance L.P. and The Business Council for Sustainable Energy shows that since 1980, energy intensity of commercial buildings has decreased more than 40 percent, which can be attributed, in part, to higher levels of efficiency in new buildings and improvements to hardware and operations relating to HVAC systems within older buildings.
The study further notes that although a commercial building in 2012 had far more electricity-consuming appliances than its equivalent in 1980, buildings today are not consuming substantially more electricity per square foot than they were then. In other words, increased electricity use has been offset by improvements to HVAC and lighting efficiency.
With building owners and managers looking to wring savings from every square foot of space, manufacturers have introduced a wide array of advanced energy-efficient technologies that are designed to lower utility bills without compromising comfort.
Monitoring and Harvesting
Electricity usage is typically one of a building’s biggest expenses, so monitoring that usage in real-time can help owners and managers make more informed decisions regarding their utility bills. TED [The Energy Detective] Pro Commercial’s three-phase electricity monitor is designed to do just that by transmitting data over the existing wiring of the building, to a router or display. From the breaker panel, the data is sent to an energy control center, which can be plugged in anywhere in the office/building.
“TED saves energy by providing real-time comprehensive electricity data in both kWh and dollar amounts,” said Melissa Lacas, director of marketing, Energy Inc., Charleston, S.C. “By projecting monthly bills; providing accurate usage every second, minute, hour, day, and month; consumers can make more informed decisions on their electricity usage. TED Pro will also tell users how efficient — or not efficient — their HVAC system is.”
TED Pro Commercial is a stand-alone device that can be installed in retrofit applications, as well as new construction, and provides energy savings averaging 12.6 percent per month, noted Lacas. “However, when integrated with an energy-efficient HVAC system, TED has the ability to monitor HVAC independently, thus providing more data, resulting in more savings.”
Another energy-saving technology recently introduced by Titus involves harvesting light energy to power the electronic logic in its EOS and Solar Plexicon diffusers. This technology senses supply air temperature and operates the drive mechanism that directs the airflow in the appropriate pattern to utilize the full performance benefit of either heated or cooled supply air in the occupied space.
“When using a manually adjusted diffuser in the past, the conventional recommendation was to split the airflow pattern between horizontal and vertical discharge, which conservatively wasted up to 30 percent of the energy cost in misdirected airflow,” said Mark Costello, grilles, registers, and diffusers product manager, Titus, Plano, Texas.
As a plenum slot diffuser, the EOS is designed for perimeter applications, where 100 percent of supply air airflow is delivered either horizontally in a cooling pattern or vertically in heating mode. The Solar Plexicon combines the fully stratified system cooling efficiency of displacement diffusion with a fully mixed system floor-level heating pattern, thereby eliminating the use of a split system and dual controls, noted Costello.
Both the EOS and Solar Plexicon energy-harvesting diffusers are fully self-contained devices that can be used in new construction and retrofit applications.
Variable-speed technology has been incorporated into HVAC systems for quite a few years in order to optimize the efficiency of the entire system. Today, new algorithms are delivering significant energy savings and stability, and establishing a new level of efficiency for commercial buildings, noted Tom Neuberger, product manager, Eaton Corp., Menomonee Falls, Wis.
An example of this is the Active Energy Control algorithm, which has been incorporated into Eaton’s new H-Max Series variable-frequency drives. The algorithm reduces the input power of an induction motor used to drive a variable-torque load, like a fan or pump, by dynamically adjusting the motor’s operating point based on its load conditions, providing power savings and improving energy efficiency.
The energy-optimizing algorithm begins when the drive is commanded to start the motor following a reference frequency, said Neuberger. “To ensure motor stability, the algorithm initially sets the drive output voltage at the same level as the voltage based on the linear V/Hz method for the same reference frequency. It then begins to reduce the voltage incrementally to optimize the energy usage. Meanwhile, the algorithm monitors several real-time parameters to prevent the motor from entering conditions that may lead to instability. When the motor enters the optimal zone of operation, the drive-output voltage stays at the same level until there is a change triggered by commands to the drive, such as a change in the reference frequency or a change in some real-time parameters. After the output voltage stabilizes, the drive keeps monitoring the motor’s real-time parameters to prevent instability conditions.”
The H-Max Series drive can be used in both retrofit and new construction applications in order to reduce energy consumption, improve reliability, and extend equipment life.
OEMs are also incorporating variable-speed technology in a variety of new ways. For example, Lennox Industries Inc.’s Multi-Stage Air Volume (MSAV®) technology uses a variable-frequency drive and patent-pending control algorithms to lower airflow in multiple modes of operation — including part-load cooling, heating, ventilation, and free-cooling operation — resulting in year-round energy savings.
As Mike Ray, senior product manager, commercial rooftops, Lennox Commercial, Richardson, Texas, explained, “When the compressors are not operating, the unit normally runs in a constant airflow mode, which, on a non-MSAV unit, is considered full speed and uses more energy. When an MSAV unit runs in a constant airflow mode, airflow is reduced by 45 percent and fan power usage can be reduced by up to 75 percent. For example, on an Energence® rooftop unit with MSAV, the fan power savings can be as high as 75 percent.”
MSAV is a factory-installed option for packaged units that are 7.5 tons or larger. These units can be applied to any one- or two-story commercial building that requires a two-stage packaged unit or split system, such as offices, retail stores, hospitals, schools, hotels, places of
worship, and restaurants.
The Condenser Fan Pak from Schneider Electric applies floating high-pressure control with variable speed for efficient operation of the condenser section of air-cooled chillers and refrigeration racks. This stand-alone, plug-and-play, energy-savings solution can be applied to any existing air-cooled chiller using any refrigerant, and it can also be integrated into a building automation system (BAS).
This technology uses variable-speed drives to control the operation of the condenser fans. By monitoring the outside air temperature and refrigeration high-side pressures, the floating high-pressure algorithm is able to reduce the high-pressure set point under which the compressors are operating, said Bob Gray, HVACR business segment manager, Schneider Electric, Knightdale, N.C.
“The condensing temperature of the condenser floats with the variance of the outside air temperature, which decreases the operating pressure and reduces the lift of the compressor,” said Gray. “This reduces the
amount of work required to produce cooling, there by reducing the energy consumption of the air-cooled chiller up to 25 percent. For the typical commercial building, the Condenser Fan Pak can be applied to any air-cooled chiller without replacing the main controller or control panel, and payback time is typically less than three years.”
Saving With IAQ
IAQ is an important consideration for any conscientious building owner or manager, yet it can be expensive to meet ASHRAE’s IAQ standard. In order to reduce the energy costs associated with delivering fresh air, manufacturers have come up with some innovative products that can temper the air and maintain comfort, while reducing energy usage.
A new energy recovery ventilator (ERV) from RenewAire, for example, recovers a high percentage of the energy contained in the stale indoor air exhausted outdoors without the energy penalty. The ERV’s static-plate core has hydroscopic resin plates that transfer both heat and water vapor from the exhaust air to precondition the ventilation air using the available energy in the exhaust air leaving the building, said Robert Ward, marketing director, RenewAire LLC, Madison, Wis.
“During summer, humid ventilation air is preconditioned using the relatively cool and dry exhaust air, while during winter, ventilation air is preheated and humidified using the relatively warmer and wetter exhaust air,” said Ward. “This is all accomplished passively without any rotating desiccant wheels or pumped liquid desiccant. In addition, the hydroscopic resin plates separate incoming and exhaust airstreams, so the two never come in contact, thus it is AHRI [Air-Conditioning, Heating & Refrigeration Institute]-certified for zero exhaust air transfer at normal, balanced operating conditions.”
RenewAire’s ERV can be used to condition ventilation air in new construction or replacement situations, and is being used in small and large installations from Maine to Arizona. Ward noted that the ERV substantially reduces air conditioning and heating energy costs, while reducing the size of heating and cooling equipment required to condition ventilation air.
Advantix Systems recently introduced the DTRT rooftop unit, which uses liquid desiccant technology to provide clean air and precise humidity control at a significant energy savings. The liquid desiccant, a nontoxic lithium-chloride solution that is essentially saltwater, removes humidity from the air while simultaneously cooling and scrubbing it free of bacteria, said Hannah Choi Granade, president, Advantix Systems, Sunrise, Fla.
“Salt has a natural affinity for water, so the technology has the ability to deliver precise humidity control without overcooling, which is the process used by conventional HVAC systems,” said Granade. “Also, liquid desiccant is a natural disinfectant, improving air quality and removing odors without the need of expensive filters. The salt solution removes almost all airborne bacteria and microorganisms in a single pass and eliminates condensation points in the systems such as drip pans and condensate lines, which often produce algae and bacteria build-up.”
The energy savings from the DTRT’s simultaneous dehumidifying, cooling, and purification processes make it an energy-efficient option for a broad range of commercial enterprises, including health care, fitness centers, schools, hotels, and food processing facilities. Granade noted that the technology reduces energy consumption 30-50 percent in the core product line and, when integrated with renewable energy or waste heat, energy consumption can be reduced by as much as 80 percent.
Even though most building owners and managers want to save energy, many are not aware of the options available to them. It is up to contractors to communicate the benefits of these energy-saving technologies to customers, so that they can make the best decisions for their facilities. As Ray added, “Building owners are beginning to understand the importance of offering new energy-saving technologies to their tenants and occupants. They recognize the financial benefits available when energy-saving technology is applied to their operations.”
Publication date: 5/6/2013