Commercial/ Industrial CO2 Heat Pumps
Commercial and Industrial Heat Pumps: CO2 Models Producing Hot Water vs. Electric Water Heater
Air- or water-source heat pumps that use CO2 as a refrigerant and can produce hot air or hot water while simultaneously generating chilled water or air.
Item ID: 293
Multiple Energy Systems--Combined Space Conditioning and Water Heating
Technical Advisory Group: 2014 Commercial Building TAG (#9)
Average TAG Rating: 3.07 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:
- Industrial applications over commercial.
Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
Average TAG Rating: 2.85 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:
- They show promise and we need to transition off high GWP refrigerants.
- I assume these are not the residential CO2 HPWH's, and are instead, larger, custom built-up units; these will be very expensive and difficult to permit and maintain, limiting the cost-effective applications.
- I am less aware of the state of commercially available products in this area.
- This is emerging. Commercial is likely to be well-suited to the attributes of CO2 systems: high lift, but high cost.
- We will need to identify market segment for the technology to be accepted in the marketplace.
- I do not know much about the effeceincy or field performance of the SE systems.
- Too expensive due to high pressure requirements.
- Seems more targeted at buildings with process loads that generate waste heat.
Transcritical carbon dioxide (CO2) industrial heat pumps are widely used for commercial and industrial applications in Japan. Mayekawa Manufacturing Company (MYCOM) offers commercial/industrial water heating EcoCute CO2 heat pumps with ratings up to 90 kW. This water-source CO2 heat pump water heater (HPWH) can supply 5,800 gallons per day of water at 194°F. This equipment typically costs 25% to 35% more than a boiler for water heating. This technology can be very useful for generating water hot enough for radiant floor heating and many industrial processes. For example, CO2 industrial heat pumps can extract the heat from fresh milk prior to refrigeration and use it to generate hot water for washing. These units require compressors that operate between 600 to 1,700 pounds per square inch gauge (psig). The heat pump Coefficient of Performance (COP) is not negatively impacted from high-pressure operation because the compressors operate at a low pressure ratio. MYCOM has obtained Underwriters Laboratories (UL) listings for their industrial heat pump products so, unlike the residential-scale version of this technology (E3TNW #389 Carbon-Dioxide Heat Pump Water Heaters), they are available for immediate purchase in the U.S.
MYCOM also offers the Sirocco CO2 hot air heat pump. This unit can boost the temperature of low-grade waste heat to provide air at temperatures between 170°F and 250°F. The Sirocco CO2 air-to-air heat pump is ideal for recovering heat from hot gas streams and boosting it to temperatures suitable for industrial drying or other process heating requirements. The air source heat pump costs 40% more than a standard heat pump.
Carnot Refrigeration and Alfa Laval offer transcritical CO2 refrigeration equipment with a capacity up to 2,000 kW. Their systems are installed in supermarkets and refrigerated perishable food storage warehouses, used for beverage cooling and ice-making, and for industrial applications and in sports facilities (ice rinks) where simultaneous heating and cooling is required.
Potential applications for CO2 heat pumps include dairies, food processing plants, wineries, and industrial drying. CO2 heat pump water heaters can achieve a COP of 4.2. COP depends on both temperature boost and the temperature of the water or air supply. When providing simultaneous heating and cooling flows, the COP can approach 8.0.
Baseline Description: Electric Resistance Hot Water Heat
Baseline Energy Use: 2.6 kWh per year per square foot
In this study for the California Energy Commission (CEC) Hot Water Roadmapping Workshop, "The Importance of Hot Water in Commercial Buildings in California," Fisher Nickel reported a total California commercial sector water heating load of 870 million therms (of which 90% was served by natural gas) (Delagah 2013). Approximately 20% of natural gas water heaters are of the condensing type, while 10% of commercial sector water heating was done with electricity.
Prorating by population (34%) indicates that the Northwest commercial sector water heating load is 296 million therms equivalent. With commercial sector floor space in the Northwest totaling 2.7 billion sf and assuming a gas-fired water heating efficiency of 80%, this equates to about 2.6 kWh of electrical energy equivalent per sf. Note that this comparative analysis assumes that commercial sector hot water use is similar in California and Washington states.
In contrast to California, the 2009 NEEA Commercial Building Stock Assessment (CBSA) indicates that about 52.4% of the Northwest floor space of 2.7 billion sf is served by electric hot water heaters (NEEA, 12/21/2009).
Manufacturer's Energy Savings Claims:
When equipped with a 30 hp (25 kW) compressor motor, the commercial version of the EcoCute can deliver up to 340,000 Btu/hour of hot water with a COP exceeding 4.0 in heating-only mode, although this is only with moderate source temperatures. A water source EcoCute installed at the Somerston Vineyards in CA uses both chilled water and condenser water as a heat source. The combined COP is 4.8 (Wilson 2013). Energy savings are based on the baseline system performance.
Transcritical CO2 refrigeration is a proven technology in Canada. Carnot Refrigeration makes transcritical CO2 refrigeration equipment with a capacity up to 2,000 kW. They claim energy savings up to 25% and savings on operating costs up to 31.5% compared with conventional refrigeration systems. Their systems are installed in supermarkets, refrigerated perishable food storage warehouses, industrial applications, and sports facilities (ice rinks), where simultaneous heating and cooling is required (Shecco).
Best Estimate of Energy Savings:
"Typical" Savings: 70%
Energy Savings Reliability: 3 - Limited Assessment
Electrical energy savings are based on a water heating COP of 4.2 at moderate ambient temperatures. The baseline system consists of electric resistance water heating. One of the advantages of using R744 HPWHs is that relatively high temperatures (185°F) can be achieved at a high COP without using supplemental electric heaters.
Energy Use of Emerging Technology:
.8 kWh per square foot per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
The Northwest region has 2.7 billion sf of commercial sector floor space. About 54.2% of the floor space is served by electrically heated water (Table C-WH2 of the 2009 CBSA). This indicates that CO2 heat pumps can potentially save electrical energy by replacing electrical resistance water heating that is currently being used to serve 1.46 billion sf of floor space.
Energy savings from industrial electrical water heating are expected to be limited because heated process water is often obtained through steam heating, waste heat recovery, or natural gas-fired condensing water heaters. These natural gas-fired units have low fuel costs because condensing water heaters can be up to 98% efficient using a cold water source. Using CO2 heat pumps to provide hot water at industrial sites would likely result in fuel savings instead of electrical energy savings. Therefore, industrial applications are not counted in technical potential estimates. For dual-fuel utilities, the technical potential would be greater.
Regional Technical Potential:
2.66 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: square foot
Estimating the equipment and installation costs is difficult because they are application specific. Feasibility studies must be completed for any industrial application. In a case study for a California winery, the integrated heat pump heating and cooling system resulted in a 25% price premium versus installing a separate propane boiler (water heater) and glycol chiller system. These additional costs were expected to be recovered in three years. This price premium is expected to drop as production increases. However, there are additional costs related to the installation of high-pressure refrigerant lines; see End User Drawbacks below for details.
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
The CO2 transcritical cycle has many benefits for energy savings versus traditional HFC/HFO (hydrofluorocarbon/hydrofluoroolefin) refrigerant-based systems. However, proper design and application are essential for savings to be realized. The CO2 heat pump energy savings depend on ambient air and fluid temperatures. Inlet conditions, the temperature boost, COP, annual operating hours, and the baseline technology greatly affect the return on investment. A detailed evaluation of system configurations is necessary to optimize an application. Depending on the end users’ current fuel source, cost for heating water, and current electrical rates, CO2 systems can offer very good energy savings along with the environmental benefit of using a natural refrigerant.
Reference and Citations:
Northwest Commercial Building Stock Assessment (CBSA): Final Report
Prepared by the CADMUS Group for the Northwest Energy Efficiency Alliance
Laipradt & Tiansuwan,
Simulation Analysis of CO2 Heat Pump Water Heaters: Comparative with Other Natural Working Fluids
MHI Develops Heat Pump Water Heater for Commercial use in Ambient Down to -25C Featuring the World's First CO@ Refrigerant
Mitsubishi Heavy Industries
Next Generation Refrigerant Debate – CO2 v HFC-1234yf and HC solutions
Green Cooling Association
Chapter 9: Carbon Dioxide (R744) - The New Refrigerant
Engineering Thermodynamics - A Graphical Approach
Richter, et. al.,
Comparison of R744 and R410A for Residential Heating and Cooling Applications
Air Conditioning and Refrigeration Center, University of Illinois at Urbana-Champaign
The Importance of Hot Water in Commercial Buildings in California
CEC Hot Water in Title 24: RoadmappingWorkshop
Natural Refrigerants Market Growth for North America - Case Studies
Update publications will be available in 2015 for both Japanese Best Practices and North American Case Studies.