Explore the potential of oil-free technology
40% Up to
greater energy efficiency with oil-free solutions.
Climate change regulations, new demands for energy efficiency, higher expectation of comfort levels, and pressure to reduce overall cost of ownership drive current development in HVAC marketplace. Oil-free technology can help you keep up with shifting global regulations and stay ahead of the curve.
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Decarbonization Goals and the Potential of Oil-free Technology
Many organizations today are working to identify ways to meet decarbonization goals, reducing their dependence on carbonrich fossil fuels such as coal, natural gas, oil, and propane. Their goal: to dramatically reduce their emissions of the greenhouse gases implicated in climate change, while, hopefully, also decreasing their energy costs and bolstering organizational reputation at the same time. Heating buildings consumes the largest amount of energy and produces the highest COâ‚‚ emissions. So, the focus is on planning for a resilient and efficient system that can provide affordable heat for all. To minimize investments, energy demand must be reduced by applying energy efficiency measures to buildings and optimizing the performance of technical building systems. There is also a need to establish efficient, decarbonized heating supply systems that put a focus on supply-side renewable energy. The nature of renewable primary energy supply will force the demand and supply sides to become much more integrated. This will in turn call for new applications and technologies like demand-side flexibility and thermal or electrical energy storage. As an example of the potential, in the Heat Roadmap Europe (HRE) studies 1 and 2, it has been shown that increasing district heating to cover 50 percent of the total heat demand, together with a 40 GW heat pump capacity, can address up to 15 percent of total heat demand. In periods with a surplus of renewable electricity, heat pumps are
supposed to continue operating and using thermal storage to capture excess heat due to unused compressor capacity. Heat pumps can be introduced effectively on a mass scale as decentralized zero carbon heat suppliers. Smaller heat pumps can boost flow temperatures for apartments or multi-apartment buildings, while large heat pumps can supply heat to the grid via ground source. Modeling suggests that, when used in electric heat pump applications, oil-free, magnetic bearing centrifugal compressors can provide up to 40 percent greater energy efficiency and lower resulting emissions compared to constant speed positive displacement screw compressor-based heat pumps, driving significant operating cost savings and substantial reduction in carbon footprint. When compared to variable speed positive displacement screw compressors — a more efficient heat pump technology, modeling suggests that a significant 15-20 percent reduction in emissions and 10-15 percent reduction in energy costs can be realized. And, when replacing or as an alternative to a high efficiency condensing boiler, the operating costs can be reduced by 35 percent and the CO2 emissions by 59 percent. This emissions reduction estimate increases as renewables are integrated into the power grid. These comparative improvements can further increase over time because oil-free, magnetic bearing centrifugal compressors
maintain performance over the long term, whereas the performance of positive displacement screw compressor-based heat pumps can degrade as much as 10 percent in the first five years and 20 percent within the first ten. This degradation process is driven by a combination of the mechanical degradation of the positive displacement compression sealing process as well as oildriven heat transfer degradation. In short, this is an innovation that will be of significant interest to heat pump designers, manufacturers, energy management consultants, and, especially, any commercial or industrial facility interested in decreasing their carbon footprint, increasing energy efficiency, and reducing heating costs.
Episode 5 For more discussion on decarbonization policies and trends in North America, listen to ENVISIONEERING EXCHANGE PODCAST, EPISODE 5.
Episode 6 For more discussion on the potential of heat pump and oil-free technology to address the technology gap caused by decarbonization, check out our ENVISIONEERING EXCHANGE PODCAST, EPISODE 6.
Oil-free Compressor Technology Oil-free, magnetic bearing compressor technology eliminates complex oil and refrigerant lubrication management systems resulting in a simplified chiller design, increased reliability and reduced maintenance.
Oil-free, magnetic bearings and integrated variable speed drive delivers industry leading efficiency with no performance degradation over the life of the compressor. Permanent magnet synchronous motor provides high efficiency and enables compact design.
Two stage compression design provides flexibility to use for water-cooled and aircooled chiller applications.
Watch Danfoss TurbocorÂŽ Technology
Zero Performance Degradation
25%
Oiled Compressors
15% 10%
Oil-Free Compressors
20% loss in efficiency
20% EFFICIENCY LOSS
Without oil in the system, there is no performance degradation due to oil contamination or mechanical wear. This, along with the contact-free operation enabled by magnetic bearings means the performance remains consistent over the life of the compressor.
Performance Degradation Over Time*
No change in efficiency over time
10% loss in efficiency
5% 0%
5
10
Life of the Compressor
YEARS OF OPERATION *Source: Tsinghua University Study 2014
Reduced Maintenance While long-term performance is a key advantage for oil-free compressor technology, there are additional benefits in terms of maintenance. Removing oil from the chiller system results in a more simplified chiller design that eliminates frequent maintenance tasks required on traditional oiled chiller systems.
refrigerant from the oil to prevent dilution) and an oil pump (circulates the oil through the system). A chiller using oil-free compressor technology eliminates these components and provides a design with significantly fewer mechanical parts and reduced complexity.
A chiller with a typical oil management system includes components such as an oil separator (separates the oil from the refrigerant), oil cooler (reduces the temp of the oil because hot oil loses some of its lubrication properties), oil heater (boils off
Eliminating the oil management system means common maintenance tasks associated with oil are no longer necessary, resulting in annual savings of $3,650 or lifetime savings of $83,950 in maintenance costs assuming a 23-year chiller life expectancy.
Chiller with an oil management system Oil separator
Required maintenance tasks for oiled chillers:
Oil separator Check valve
Check oil level Daily
Check valve
Oil heater
Change oil
Oil heater
Annually $1,600
Evaporator Oil cooler
Oil cooler
EXV
Oil pump
Replace oil filter Bi-annually
Oil pump
$2,000
Inspect / maintain key components - oil pump, sump heater
Condenser
Weekly
Oil analysis Annually
Oil-free chiller
$50
The above five maintenance tasks are no longer required on oil-free chiller systems. Oil-free compressors: Benefits
Evaporator
Filter
EXV
Check valve
$
Energy and cost savings
Zero performance degradation
Low sound and vibration
Less complexity
High reliability
Reduced maintenance
Compact and light weight
Low-GWP refrigerants (R513A, HFO1234ze(E))
Condenser
CASE STUDY | OIL-FREE COMPRESSORS MAINTAIN CONSISTENT PERFORMANCE OVER TIME
Oil-free Compressors Maintain Consistent Performance Over Time Cooling large buildings typically requires the use of air or water-cooled chillers that produce chilled water, which then cools the air. About 39 percent of buildings over 100,000 square feet use chilled-water systems employing various compressor designs. Selecting the right chiller and compressor requires a specifying engineer to determine the building’s cooling load and the proper chiller capacity.1 Calculations are also done to determine the return on investment between different systems by comparing the energy cost per ton of refrigeration along with the operational costs. When buying a new chiller, specifying engineers and facility owners naturally focus on efficiency ratings to estimate the chiller’s annual energy costs. In addition to the chiller’s performance ratings, however, there is another variable worth considering: How will the chiller and the chiller’s compressors maintain their rated performance in real-world operating conditions years after the purchase has been made? A significant factor that affects chiller performance over time is the oil used by the chiller’s compressor. Oil is used to form a seal that prevents refrigerant from returning to the suction port as well as lubricate the compressor bearings, gears and shaft seals. While necessary for operation, over time, the oil becomes entrained in the refrigerant and circulates throughout the system. Eventually, the oil coats the heat exchanger tubes, which creates a thermal barrier that degrades efficiency—a problem known as “oil fouling.”
A number of independent third-party studies detail the consequences of oil fouling, which include: • A drop in heat transfer ratio from 1.0 to 0.65 at oil concentrations as low as 10 percent.2 • A loss of 10 percent efficiency after five years, 20 percent efficiency loss after 10 years in oil-lubricated chillers at Tsinghua University, China.3 • As much as 30 percent performance degradation in other cases.4
Hershey’s Chocolate World Data Center (Hershey, Pennsylvania, USA)
Performance degradation over time is not only due to oil fouling. Another study shows that traditional oiled compressors, specifically screw compressors, suffer significant performance degradation due to excessive bearing wear, capacity slide damage, and other factors over years of operation.5 This study concluded that screw compressor wear significantly impacts performance by the fifth year of operation, and subsequent performance degradation was found to be as high as 26 percent on average after 15 years of operation. To avoid mechanical wear and oil-related performance problems, Danfoss offers variable-speed centrifugal semi-hermetic compressors that employ oil-free magnetic bearings. With Danfoss Turbocor® compressors, chiller manufacturers are able to eliminate complex oil management systems that conventional chillers need to lubricate mechanical compressor bearings. Theoretically, an oil-free hermetic compressor design avoids the frictional inefficiency, degradation and maintenance issues associated with conventional oiled compressors. But how does it compare in actual practice after years of operation? To find out, Danfoss initiated a research project in 2018 to compare the present-day performance of Danfoss Turbocor® compressors in operation for 10 or more years with their performance when originally installed. The study sought to determine if oil-free compressors experienced the same performance degradation found in traditional oiled compressor types—or whether they maintained their original level of performance. The study confirmed that Danfoss Turbocor® compressors with oil-free magnetic-bearings maintained consistent performance over a 10-year period.
Application The Hershey Company is a global confectionery leader famous for its chocolates, sweets, and snacks. In 1973, it opened Hershey’s Chocolate World in Hershey, Pennsylvania, and then expanded to locations that today range from Times Square to Dubai to Shanghai. To serve chocolate customers and fans worldwide, Hershey’s Chocolate World also operates a data center located in Hershey. The data center operates around the clock using a chiller providing cooling for the electronic equipment.
Cooling technology To handle these conditions, the data center employs one 180-ton (600 kWr) Smardt WA062.2 water-cooled chiller using two Danfoss Turbocor® TT300 oil-free centrifugal compressors. Optimized for R-134a refrigerant, each compressor provides up to a nominal 90 tons of refrigeration utilizing two-stage centrifugal compression.
Performance testing The two compressors submitted for performance testing incurred over 38,967
and 38,928 hours of operation, respectively, resulting from 24/7 operation in datacenter cooling for more than 10 years. In January 2018, the compressors were removed from the chiller and replaced with new TT300 compressors. The existing compressors were sent to Danfoss’ test laboratory at Innovation Park in Tallahassee, Florida. TT300 Compressor One tested at 48.0 kW per ton of refrigeration (TR) and Compressor Two, 49.0 kW/TR, at pressures, RPMs, and capacities shown in Tables 1 and 2. (Although no official test standard pertains to standalone centrifugal compressors, AHRI 540-2015 was used as a test reference as explained below.) These results fall within the AHRI 5402015 uncertainty limits for the verification of published ratings for an application envelope with 95 percent for minimum mass flow and minimum refrigerating capacity and with 105 percent maximum power input. These results were then compared with the original test parameters for each compressor when they were tested and shipped in 2007 from the Danfoss factory to the chiller manufacturer.
CASE STUDY (CONTINUED)
Test results and conclusions • Tested deviation over a decade: From its original 2007 power test value of 46.8 kW, Compressor One deviated 2.56 percent higher 11 years later (Table 1). Mass flow was 2.13 percent higher. From its original 48.7 kW value, Compressor Two deviated 0.62 percent higher for power consumption (Table 2) and was 0.15 percent higher in mass flow. • Performance consistency: The range of deviation for kW and mass flow (Tables 1 and 2) were all within the acceptable uncertainty limits for performance per AHRI 540-2015.
This range approximates the expected performance values for new compressors. The results show the Danfoss Turbocor® TT300 oil-free compressor experienced no significant performance degradation over an 11-year period. This evidence indicates the compressors provided consistent, longlasting performance that is likely to extend over the life of the chiller. • Customer satisfaction: Steven C. Miller, senior maintenance specialist for The Hershey Company Data Center, notes that “in a data center, reliability is everything. This chiller with Danfoss Turbocor® TT300
magnetic-bearing compressors has been, and still is, an extremely reliable chiller. Operational and maintenance costs are way down, because there have been very few repairs over the 10+ years this chiller has been in service. We originally selected this technology due to low noise levels and a track record of success at other sites. In our case, the chiller with Danfoss Turbocor® compressors has met and exceeded my expectations regarding performance.”
Table 1: Compressor 1 performance values for Hershey’s Chocolate World data center TT300 Compressor (90 tons nominal)
Suction Pressure
Discharge Pressure
RPM
Power (kW)
Mass Flow Rate (kg/min)
2007 test
359.33
918.88
31905
46.8
101.08
2018 test
362.1
919.75
30656
48.0
103.23
Deviation
0.77%
0.09%
-3.91%
2.56%
2.13%
Table 2: Compressor 2 performance values for Hershey’s Chocolate World data center
1
TT300 Compressor (90 tons nominal)
Suction Pressure
Discharge Pressure
RPM
Power (kW)
Mass Flow Rate (kg/min)
2007 test
353.0
912.39
32002
46.7
100.18
2018 test
354.74
914.91
32005
49.0
100.33
Deviation
0.49%
0.28%
0.01%
0.62%
0.15%
“Heating and Cooling.” Energy Star. Accessed October 30, 2018. https://www.energystar.gov/sites/default/files/buildings/tools/EPA_BUM_CH9_HVAC.pdf, page 3.
2
“ASHRAE Research Project Report RP-751: Experimental Determination of the Effect of Oil on Heat Transfer in Flooded Evaporators with R-123, R-134A.” ASHRAE. 1999.
3
Ray Good. “Emerging Oil Free Technologies.” Accessed October 30, 2018. https://utahashrae.org/images/downloads/Chapter_Meeting/slc_ashrae_emerging_oil_ free_technologies_final.pdf, slide 14.
4
“Improving the Energy Efficiency of Air Conditioning and Refrigeration Systems.” Power Knot. Accessed October 30, 2018. http://www.powerknot.
com/2017/03/02/improving-the-energy-efficiency-of-air-conditioning-and-refrigeration-systems. 5
Ying Zheng and Michael Bellstedt (Minus40 Pty Ltd). “Final Report: Compressor Degradation Assessment and Wear Mitigation Strategy.” Meat & Livestock Australia Limited, North Sydney NSW, Australia. December 2014, page 19.
PRODUCT HIGHLIGHT
Danfoss Turbocor® VTT and VTX oil-free, magnetic bearing compressor Danfoss Turbocor® VTT1200
The Danfoss Turbocor® VTT1200 (Variable Twin Turbo) compressor brings the benefits of oil-free, magnetic bearing technology up to 400 tons / 1430 kW. The large capacity design results in an oil-free chiller system up to 3200 tons / 11,250 kW or larger in a multiple compressor configuration. The VTT1200 compressor, optimized for watercooled chiller applications, uses the patented IntraFlow™ technology which extends the stable operating range and increases the turn down capability of the chiller. The result is a compressor that minimizes the risk of surge while maintaining peak full- and part-load efficiency.
Danfoss Turbocor® VTX1600 The 450 ton / 1600 kW nominal capacity rating of Danfoss Turbocor® VTX1600 compressor allows for a multiple compressor configuration up to 3600 tons / 12,660 kW or larger. The VTX1600 compressor uses an advanced aero design that gives industry leading full-load efficiency with no performance degradation over the life of the compressor. Combined with the advanced IGV design, the VTX1600 provides outstanding unloading capability even at constant entering condenser operating conditions.
ChillerROI App The Danfoss ChillerROI app simplifies the decision-making process by allowing you to estimate the return on investment (ROI) using a few pieces of basic information. Simply enter the parameters into the app, and you’ll get a side-by-side comparison that displays the expected long- and short-term costs. Then, you can choose the best chiller for the situation.
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