Heat Pumps Come in Many Styles
Alternative systems look for their share in the heat pump market
Not that long ago, if a conversation centered on heat pumps, it was fairly safe to assume that the equipment referred to ducted, split-system, electric, air-source units. That assumption started to change a few years ago with the growing popularity of ductless heat pumps. And geothermal heat pumps. And VRF systems. Now, there are multiple types of heat pumps available, including gas-powered systems and so-called magic box units, which contain an air-source heat pump to help improve IAQ.
While these alternative units still comprise just a fraction of the heat pump market, manufacturers are hopeful sales will grow once end users and contractors learn about the benefits of the technology.
Until recently, electricity was typically cheaper than natural gas, which helped create a strong demand for traditional air-source heat pumps. That scenario started to change a few years ago, when prices for natural gas began to drop. For Yanmar America, this meant the time was right to bring its gas-powered heat pump (GHP) to the U.S.
Even though Yanmar is just now introducing its GHP technology to America, the company has been around for a century and has installed hundreds of thousands of GHP systems worldwide over the past 29 years. “The systems have just achieved EPA compliance for use in the U.S., so they are new to the market,” said Chris Dockery, product integration manager, Yanmar America. “Our GHP is designed for commercial applications and is popular in warm climates as well as cold climates, where it performs extremely well due to our engine heat recovery technology.”
Using variable refrigerant flow (VRF) technology, Yanmar’s GHP is powered by an engine that runs off of natural gas instead of electricity. When operating, natural gas is pumped into the GHP’s condensing unit to start the engine, which then uses a belt to start the compressors. The GHP can heat, cool, or simultaneously heat and cool up to 29 different zones at the same time, depending on the facility’s requirements, said Dockery. “Our system modulates and turns off indoor units in zones that no longer require heating or cooling, and our systems can be ducted or non-ducted, depending on the requirements of the facility.”
A GHP offers other benefits as well, noted Dockery, including high efficiencies at part-load conditions and up to 90 percent less electrical consumption due to the use of natural gas. “And because our GHP uses less electricity, electrical demand charges may be reduced or eliminated. In addition, our GHP system offers substantially lower life cycle costs due to lowered operating and infrastructure costs and greater efficiency. In fact, overall operating costs can be reduced 30-70 percent, depending on local utility costs.”
Yanmar’s GHP systems do not cost significantly more than VRF or heat pump systems, said Dockery, and they are installed the same way as traditional VRF systems. Maintenance is required every 10,000 hours of engine run time, and units can last as long as a traditional VRF or heat pump system. “Right now, we offer 8-, 10-, 12-, and 14-ton two-pipe models [heating or cooling], as well as a 14-ton three-pipe system [simultaneous heating and cooling]. We are looking forward to architects, engineers, contractors, and natural gas utilities learning more about our systems so they can promote them to their customers.”
Robur Corp. and its parent company Robur S.p.A. have been in business for almost 60 years, perfecting gas-fired absorption cooling technology, which has resulted in both air-source and ground-/water-source heat pumps. With this technology, heat that is gained from an outside renewable energy source (air, ground, or water) is combined with the gas-operated absorption cycle of the heat pump, providing hot water at a very high heating efficiency. For cooling, the absorption cycle transfers heat from the indoor space to the outside energy source.
The air-source heat pump is essentially an air-cooled absorption chiller with a reversing valve and defrost cycle, explained Rick Halbig, sales manager, Robur Corp. “This unit produces either chilled water for cooling or hot water for heating. In the cooling mode, heat from the indoor space is dissipated to the outdoors, and, in the heating mode, heat is gained from the outdoors. The water- or ground-source heat pump provides chilled and hot water simultaneously.”
Robur’s gas-fired absorption technology combines the advantages of an electric heat pump with a high-efficiency gas boiler, said Halbig. “Benefits include using economical natural gas as the primary energy source; utilization of renewable energy sources; heating efficiencies exceeding 100 percent; hydronic cooling and heating flexibility; and, depending on the model, the ability to provide or supplement domestic hot water requirements.”
Due to the size of the equipment, Robur’s systems are best suited for commercial or large residential applications that require 5-50 ton of cooling and 100-1,500 MBtuh of heating. The high heating efficiency of Robur’s heat pumps means they are ideal for cold climates, and air-source units can provide stable heating operation at outdoor temperatures down to minus 20°F, said Halbig. “This greatly reduces the need for backup heat. Our ground- and water-source units are designed to be installed indoors; therefore, their cold climate installation range is virtually unlimited.”
While Robur’s heat pumps may cost more initially, operational savings and equipment longevity can often be greater than that of electric heat pumps, said Halbig. “Because the Robur units have no compressor or engine, their lifespans are exceptional. Ultimately, cooling and heating with gas reduces the use of water by reducing electrical power generation and provides a smaller carbon footprint.”
THE MAGIC BOX
Two years ago, Build Equinox introduced the Conditioning Energy Recovery Ventilator (CERV) in response to its extensive research that revealed the air quality in today’s homes is poor. “Conventional residences historically rely on infiltrated air for ventilation, and infiltrated air is not fresh air,” said Ty Newell, vice president, Build Equinox. “Current ventilation technologies are based on simple fan settings or timers for introducing fresh air, which means a home is either overventilated or underventilated, but rarely ventilated at the proper rate.”
The CERV is a demand-controlled ventilation (DCV) system that incorporates both volatile organic compound (VOC) and CO2 sensors for monitoring and controlling a home’s air quality as well as a heat pump for energy exchange between fresh-air and exhaust airstreams. “This exchange allows the system to deliver filtered, conditioned fresh air to a home rather than air that is not quite at comfort conditions, as in simple heat recovery ventilation (HRV) and energy recovery ventilation (ERV) systems,” explained Newell.
There is one basic CERV fresh-air ventilation system, which consists of two dorm-refrigerator-sized modules. One module is the heat pump module, which contains the sealed system heat pump, and the second is the fresh-air module, which contains dampers for switching airflows from fresh air to recirculation modes as well as changing from heating to cooling modes. The fresh-air module also contains the CERV’s controller and all sensors (CO2, volatile organic compounds, indoor temperature and relative humidity, and outdoor temperature and humidity).
Two insulated ducts connect the CERV to the outside — one for fresh air and the other for exhaust air. The fresh-air module is often stacked on top of the heat pump module, and insulated duct manifolds connect the two modules. Two additional ducts — an insulated house fresh-air supply duct and an uninsulated house exhaust duct — are also connected to the CERV. A thermally insulated filter box is placed as close as possible to the fresh-air inlet in order to keep the fresh-air inlet duct clean.
“Two whisper-quiet fans, which are included with the CERV, are connected to the house’s fresh-air supply duct and to the exhaust air duct,” said Newell. “Power wiring is connected to the modules, and a condensate drain line is connected to the heat pump module. No external control or sensor wiring is required, as the CERV’s sensors and controls are integrated inside the fresh-air module. Once power is switched on, the CERV begins communicating with its wireless handheld controller and through the online CERV-ICE controller app.”
When fresh air is required in the winter, the CERV first filters outside air to a level based on a homeowner’s MERV filter preferences (using a standard filter size). Fresh air is heated by passing through the CERV’s condenser section, and indoor air is exhausted at the same rate as fresh air is delivered for balanced ventilation of the home. Indoor exhaust air passes through the CERV’s evaporator section, where exhaust air is cooled and moisture is condensed. The combined sensible and latent cooling energies combine with the compressor’s energy and are delivered as heat to the home, with delivery temperatures averaging 85°-95°F.
When a home’s air quality levels are satisfied in the winter, the CERV operates in recirculation heating mode, during which indoor air passes through the heat pump’s condenser section while outdoor air passes through the evaporator section. “We reverse airflow rather than the more conventional heat pump refrigerant reversing valve,” said Newell. “This strategy allows us to optimize the condenser and evaporator for their heating and cooling/dehumidification duties.”
During the summer, the CERV operates in a similar (but opposite) fashion, with a fresh-air cooling/dehumidification mode and a recirculation cooling/dehumidification mode. “The CERV’s intelligent algorithms also determine when outdoor conditions are nicer than indoor conditions, allowing it to operate in free ventilation mode, where the heat pump is not activated,” said Newell.
CERVs operate in all climates and in residential applications ranging 500-5,000 square feet. In high-performance homes, the CERV’s heat pump capacity can contribute a significant fraction of a home’s comfort conditioning energy; however, all homes should have a primary heating and cooling system for comfort management at design-day conditions, said Newell. “CERVs can be integrated into homes with many different types of comfort conditioning systems, including geothermal heat pumps, mini-split air-source heat pumps, central heat pumps, wood stoves, radiant floors, and radiant panels. The CERV automatically delivers fresh air when needed, in the amount needed, providing homeowners with the peace-of-mind that they are living in a healthy indoor environment.”
Publication date: 5/23/2016