Carol Brzozowski 2017-01-17 17:43:30
Efficiency is the buzzword for innovations in HVAC technologies. “Government mandates are requiring higher efficiencies overall from the building, which includes everything from the HVAC all the way to the glass in the door,” points out Steve Ulm, spokesperson for SEMCO. “Efficiency is driving the construction industry as a whole.” SEMCO offers entire HVAC systems or parts that go into an overall system that a mechanical engineer or a mechanical consulting firm may put together, says Ulm. “We’re always looking to improve the efficiencies of our products,” he adds. “That may be finding new motors or fans that can rate better energy performance within the device. We do a lot of energy recovery—primarily rotational or wheels energy recovery—and we’re always trying to find ways of improving our own energy recovery to make the overall system more efficient.” HVAC innovations that battle humidity is another trend Ulm also notes. “You’ve got to get the humidity out to be able to deal with it for most applications,” he says. “That’s driving the more tactical aspects of HVAC development to where we developed a product that will work to bring the humidity down to a much more manageable level so the system is more efficient overall.” One of the functions of SEMCO wheels is to pre-condition the air coming into an HVAC system. “It can help capture and pull out that humidity much better than someone using a coil system where they may be trying to dry or cool the air to bring the humidity down. That’s one of the more tactical pieces in the overall picture we’re seeing a great deal of because of the temperature and humidity fluctuations—some of this wild weather is certainly an issue,” says Ulm. SEMCO also offers a line of desiccant-based products and systems designed to recover energy, increase ventilation, and control humidity. The solutions meet ASHRAE 62 requirements of providing continuous ventilation while controlling humidity under any operating condition. The technology was recently used in a hybrid HVAC design at George Rogers Clark High School (GRCHS) in Winchester, KY. The results were 35% lower monthly utility costs and improved indoor air quality and comfort, which prompted a 1.5% increase in school attendance. The high school uses a geothermal-based chilled water loop, combined with SEMCO chilled beams and dedicated outdoor air systems (DOAS) for its HVAC system. At 300,000 square feet, GRCHS ranks among the largest nationwide, but records a 31.9-k/BTU energy use index (EUI), significantly less than the 68-k/BTU EUI of an average-sized US school. The driving factor for the increased efficiency is a hybrid HVAC design with a geothermal well field supplying active chilled beams and dual wheel outdoor air dehumidification systems, among other cutting-edge technologies. Paul Christy, superintendent of Clark County Public Schools, and former district director of operations, oversaw the high school’s HVAC design team. The group included engineer Charles H. Wade, vice president of KTA Engineers; Mark Saunier, president of Comfort & Process Solutions; and SEMCO engineers. D.W. Wilburn Construction Co. oversaw the construction and HVAC installation. Initial plans specified a conventional 200-foot, 80-well geothermal field with ground source heat pumps (GSHPs). Christy chose to optimize the design by replacing the proposed 350 heat pumps with 542 active chilled beams and six SEMCO Pinnacle Series DOAS heat recovery systems based on visiting a similar system at Furman University in Greenville, SC, and reviewing SEMCO’s building energy simulation report. The IQHC chilled beams, supplied by a water-to-water \GSHP by ClimateMaster, Oklahoma City, OK, feature a field-adjustable, 12-slot nozzle for areas with excessive solar gain or heat loss. The GRCHS maintenance staff is trained to adjust volume and up to a 45-degree angle directional airflow for hotspots with each chilled beams’ hand-operated levers for the greatest airflow flexibility efficiency. The nozzle adjustment additionally provides a unilateral, disproportional, or equal air volume from each side, designed for ideal room coverage and flexible distribution possibilities without relocating the device. The chilled beams are designed to never develop condensation due to five rooftop DOAS units ranging from 3,700 to 14,500 cfm supplying them with semi-neutral, super dry air. One 7,000-cfm DOAS is located in a mechanical room. Areas such as the cafeteria and gym were deemed unsuitable for the chilled beams, using their own DOAS to distribute cooling and heating via the GSHP loop. In addition to energy savings, other benefits GRCHS derived from the HVAC system include: • 2,000-square-feet of storage space savings that would otherwise have housed heat pumps in two mechanical rooms; • Reduced maintenance because chilled beams require no filters and moving parts, thus eliminating periodic classroom-interrupting maintenance tasks; • Less piping due to only two of every classroom’s four chilled beams being four-piped—chilled beam piping diameters are smaller than the original configuration of piping heat pumps to each classroom; • Reduced ductwork because chilled beams require only six-inch-supply take-offs and half the air volume of a traditional system; • Quieter classroom environments due to chilled beams being approximately 10 to 15 db quieter than heat pumps; and • Better temperature and humidity control by independently controlling each load. A building energy simulation report, using the Carrier hourly analysis program (HAP) in conjunction with SEMCO’s supplemental Pinnacle hourly energy analysis module, compared the estimated annual energy consumption of the high school’s three most likely HVAC approaches. One approach: a DX-based outdoor air system, including a total energy recovery wheel and hot gas reheat capabilities preconditioning the outdoor air delivered directly to the classroom spaces served by individual GSHPs. A second approach: a DOAS incorporating both energy recovery and passive dehumidification wheels served by a GSHP to precondition outdoor air delivered directly to the classroom spaces served by individual GSHPs. A third approach: a DOAS and active chilled beams combination, all served by a GSHP chiller to condition the media center and all classrooms. The conclusion: the Neuton pump modules combined with chilled beams result in the most energy efficient system available. Dan Diehl, CEO of Aircuity, explains that the efficiency of HVAC devices is of paramount concern, along with the intelligence, data output, and connectivity. “Chillers, air handling units, fans, and drives are all sold with some level of intelligence built-in and need to be connected to the larger control and enterprise-wide information management systems,” he says. The impact of these changes on HVAC performance is that clients are more aware of true life cycle costs, change in performance, and the monthly, weekly, daily, and hourly performance of their systems, notes Diehl. “Also, with greater efficiency has come improved performance and design,” he says. “We see more end-users spending money on the best life cycle cost—overall costs including energy and maintenance—versus just looking at first cost. “Most end-users didn’t care to know about HVAC versus lobby decorations and other aesthetic concerns. Now there is an awareness about the Occupant Indoor Environmental Quality and overall health and productivity of the office, lab, or multi-purpose space, and so HVAC is a much higher concern for the top-tier companies such as Apple, Google, and PNC Bank, among others.” Kevin McNamara, senior vice president for air conditioning systems at LG Electronics USA, notes that his company is also observing a growing interest in energy-efficient facilities of all shapes, sizes, and designs. “Though some of this has been done through stricter building codes and energy conservation programs such as LEED and ENERGY STAR certifications, more and more building owners are demanding higher efficiency cooling and heating systems without sacrificing comfort,” he adds. In other parts of the world, Variable Refrigerant Flow (VRF) systems are a dominant technology, because they offer exceptional advantages including reduced energy consumption, modular design, comfort on demand, superior zoning capabilities, and quiet, efficient operation, says McNamara. “For the same reasons, the HVAC market in the United States is evolving, and VRF technology is rapidly gaining acceptance and use,” he adds. VRF systems such as those developed by LG are engineered to greatly minimize the numerous efficiency losses found in conventional HVAC systems and to provide sustainable energy benefits in both commercial and residential spaces, says McNamara. “There’s also a movement happening in HVAC technology to fit in with the growing interest of smart buildings,” he says. “Centralized controllers provide building owners, facilities managers, and maintenance personnel with the ability to manage the entire LG air system from a single location. “This allows convenient management of AC units and other facilities equipment—even on multiple sites—which helps ensure the highest energy savings are realized from the system. The other benefit is data being collected, then analyzed and, in turn, becoming knowledge that can be acted upon.” HVAC performance is improved by these changes in the sense that owners and ownership groups are getting much more involved in order to make an informed and qualified decision, says McNamara. “A conscious effort to look long term, at all data points, as well as the desire to break free from conventional paradigms leads, to the goal of superior performance from the investment in HVAC systems, has been a huge change over the past decade,” he points out. “We believe the HVAC technology in general has already started to shift from traditional systems toward advanced integrated HVAC systems that are based on VRF designs,” says McNamara. “With time, we’ll continue to see more and more integrated solutions for heating and cooling that LG has been focused on.” A case in point: the restoration of the Bexar County Courthouse in Bexar County, TX. Built in 1896 in San Antonio and listed on the National Registry of Historic Places, the courthouse features a sandstone, granite, and terra cotta exterior and a courtroom with 25-foot tall coffered ceilings with gilded moldings, millwork, and decorative windows placed high on the walls. Its conventional air conditioning system brought comfort to occupants, but the ductwork and drop ceiling required by the system blocked the windows and balcony and hid the ornate ceiling. The Texas Historic Courthouse Preservation Program provided matching funds for a $9 million renovation project completed in 2015 to restore the structure to its original 1896 appearance while maintaining comfort. The challenge focuses on the building’s steeply sloped decorative roof, which prohibited the installation of mechanical equipment on the roof. There was no room for equipment on the ground. The new HVAC system had to be inconspicuous and quiet as to avoid interfering with courtroom proceedings. A central chiller plant supplied chilled water to the previously installed, conventional HVAC system and to several other area buildings; changing the chilled water source was not an option. Texas Air Systems utilized LG Electronics’ VRF technology to create a solution to maintain the historic building’s integrity while ensuring air-conditioned comfort for its occupants. The company utilized 84 tons of LG water-cooled source units and 47 indoor units to match the courthouse aesthetics. The compact LG VRF systems were installed to work around the unique ceiling structure and meet the project’s design and architectural challenges. Pre-construction testing with a custom-built model unit offered assurances the design would provide the quiet operation needed in the courtroom. The project’s design engineer, controls contractor, mechanical contractor, and Texas Air Systems team redesigned the water loop to supply water to the LG water source units and allow the existing system to continue to function as originally designed. An LG BACnet gateway integrated the LG controls into an existing wide-area automation network, enabling Bexar County officials to monitor the system from a remote location controlling multiple buildings in the area. Variable frequency drives (VFDs) have been around for 20 years or so, and in the beginning, they had some issues with reliability and other issues that have now been solved, notes Larry Gardner, product marketing manager for HVAC drives, Yaskawa America. In a white paper titled “Five Reasons for VFDs in HVAC Applications,” Gardner likens some of today’s HVAC systems to driving a car with the gas pedal to the floor and controlling the speed with the brake. “Induction motors with across-the-line starters have only one speed—full—and then mechanical dampers, vanes, or valves restrict the flow depending on the need,” he points out. Yaskawa’s VFDs enable a method of control analogous to driving a car in varying the speed of the engine to match the requirement of speed and acceleration for the traffic at hand and using the brake only when necessary, notes Gardner. VFDs employ sophisticated electronic designs to accomplish the basic task of taking in constant AC voltage and a frequency input (typically 230V or 460V, 60Hz three-phase in the US), rectify it to DC, and then electronically generate a variable voltage and frequency to drive an induction motor, Gardner points out. “Since the motor’s speed is dependent on the frequency, its speed will vary accordingly. Voltage varies as needed by the load, by virtue of the selectable parameters built into the drive,” he says. “Besides the variable frequency and voltage, today’s drives have myriad other functions built-in for control and monitoring of the work to be done.” HVAC-specific drives can benefit a system in five ways, Gardner notes. Energy efficiency is first among them. Motors running at full speed use maximum power. The nature of HVAC loads is that power consumed varies with the cube of the speed. “That means if the demand of the system requires only 75% of full output and the VFD drives the motor at the associated three-fourths speed, it only consumes 42% of its full speed power,” says Gardner. “At 50% speed, it uses only 13% power. In typical commercial buildings, peak load conditions that require full speed occur less than 5% of the time.” In across-the-line starts, an induction motor’s inrush current is many times at its full load amperage rating, as it tries to get to full speed as fast as possible. VFDs can be configured to ramp up to speed and down at a deliberate rate most suitable to the application, resulting in additional savings, notes Gardner. While such an energy-efficient approach makes sense in new installations, energy costs can also be derived in retrofit installations with an ROI equal to the VFD’s cost in a year or less, he adds. The second major benefit to VFD comes in the mechanical life, says Gardner. “Across-the-line motor starts put tremendous stress on the mechanical components that transfer the motor’s shaft rotation to pumps, fans, or other parts of the HVAC system,” he says. “Belts, pulleys, gears, pumps, and fans all sustain the majority of their wear and tear during starts and stops in traditional systems. VFDs can be configured to ramp up to speed and ramp down to stop at rates much gentler on a system’s components.” Additionally, VFDs have the ability to be programmed to avoid speeds known to suffer from resonant mechanical frequencies that have the potential to damage equipment or are particularly noisy, Gardner adds. VFDs are designed with a wide range of monitoring capabilities enabling actions to be taken to prevent failures, including sensing and responding to overcurrent and overvoltage conditions, overtorque and undertorque, among others. Broken belts as the result of undertorque and jammed impellers resulting from overtorque are conditions a VFD can sense, says Gardner, adding that actions for each are programmable to match the need, such as shutting down and generating an alarm. A third benefit offered by VFD is controls to match the needs of HVAC applications, which are primarily moving air and water. “Beyond specific speed and torque control to match the needs of fans and pumps driven by motors up to 500 horsepower and larger, a wide range of other VFD functionalities can often perform the functions of separate controllers,” points out Gardner. Drives have extensive proportional-integral capability to continuously calculate an error value as the difference between a measured process variable and a desired set point, and make the necessary adjustments to the motor speed, he says, adding that real-time clocks provide the ability to set schedules for operation by time or calendar. A fourth benefit is connectivity. VFDs come with communication protocols built-in or as options for a wide range of networks, such as BACnet, Metasys, Apogee, Modbus, and others, to provide connection to a building automation system (BAS), Gardner points out. “The BAS can give the VFD a signal to vary its speed according to the demand of the System,” he says. “Monitors in the VFD sense conditions, status, and any problems, then send those back to the central BAS. VFD displays can be mounted on the drive or an enclosure door to give operators real-time information on system status. Problems are dealt with and logged for future reference.” The fifth benefit speaks to how equipment is evolving: earlier challenges with VFDs are being mitigated, Gardner points out. Early VFDs and some current designs cause significant current and voltage harmonics, which are momentary fluctuations outside the power grid’s pure sinusoidal voltage and frequency. “These harmonics result in circulating currents above and beyond those necessary to drive the motor, and that must be handled by all parts of the electrical infrastructure, including the motor, conductors, and transformers,” says Gardner. “If system harmonic content becomes significant, oversizing of source components and/or harmonic reduction may be required.” Gardner points out that the significance of the effects of harmonics depends largely on the proportion of the load that is producing harmonics and the degree of harmonics produced by the VFD and other nonlinear loads, such as battery chargers and electronic ballasts. Modern drives have harmonics suppression features built in, such as DC link chokes, he says. “A newer design drive, though, produces virtually no harmonics,” he says. “Whereas traditional VFDs use the AC to DC to AC approach, Yaskawa’s Matrix drives skip the DC bus and go directly from constant AC voltage and frequency to variable AC.” While the drive design is more expensive than the traditional VFD, that cost can be less expensive and require significantly less space than other harmonics mitigation techniques, such as multi-pulse transformers, Gardner says, adding that Matrix drives are designed with the added benefit of sending braking energy back on the grid. Peter Walter, HVAC drives market manager at ABB notes, “The whole of an HVAC system has always been greater than the sum of its parts. Over the last decade, the equipment that makes up these parts has evolved and adapted to meet the changing needs of both users and owners. “HVAC equipment has evolved to not only better control the environment, but to better become a more sustainable and integral part of it.” Demands for improved air quality, increased energy savings, autonomous building intelligence, precise environmental control, sustainability, and reduced operating costs have driven HVAC equipment and equipment manufacturers to new levels of performance, he adds. The combination of ultra-high efficiency motor designs and versatile VFDs on the fan, pump, compressor, and even some chiller equipment, has brought energy savings to new level, Walter notes. “Recent improvements in motor design and construction provide even more efficient equipment operation at reduced speeds,” he says. “HVAC equipment manufacturers offer increasingly robust products. Manufacturers’ equipment design efforts have increased focus on reducing maintenance and downtime and making more sustainable products. Reducing both the physical and carbon footprint are objectives of equipment manufacturers to save space and the environment.” Climate control can be done with more precision by using equipment with greater output accuracy or granularity, notes Walter. “Whether a space is occupied by living things or archived treasures, deviation of several degrees in a set temperature or humidity is not often tolerated today,” he says. “HVAC equipment has evolved to address this demand for tighter control of the climate. Throughout the HVAC system, pieces of equipment can now independently and collaboratively fine-tune their part of the whole. “Building automation brings the parts together. Intelligent building automation systems can collect, analyze, and act upon data obtained from the many parts of an HVAC system. In order to connect to the BAS, individual pieces of HVAC equipment have, by necessity, evolved to include sophisticated communications capability and system interoperability.” DE Carol Brzozowski specializes in topics related to energy and technology.
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