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“Green Machine” Organic Rankine Cycle April 30, 2013
Presenters:
Vamshi K. Avadhanula**, Ph.D. Candidate Mechanical Engineering Department, Alaska Center for Energy and Power
University of Alaska Fairbanks (**Academic Advisor: Dr.Chuen-Sen Lin)
Daisy Huang, Research Engineer Alaska Center for Energy and Power
University of Alaska Fairbanks
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What is the Organic Rankine Cycle? Why are we interested in the Organic Rankine
Cycle? Selection of Green Machine as test system Partnership with Tanana Chiefs Conference 600-hour test in ACEP laboratory Deployment to a TCC community
Outline
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What is a Rankine Cycle?
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• The Rankine Cycle extracts energy when a working fluid undergoes a phase transformation between liquid and steam.
• The Rankine Cycle is widely used both in fossil fuel power generation and in solar thermal, biomass, and nuclear power plants, generating about 90% of all electric power used worldwide today.
The working fluid is boiled by the heat source.
The steam powers a turbine.
After the useable energy is released, the steam condenses back to a liquid, expelling its own waste heat in the process.
What is the Organic Rankine Cycle?
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• The Organic Rankine Cycle operates on the same principle, only it uses as a working fluid an organic compound specially chosen to boil at a lower temperature, enabling it to extract power from lower temperature heat sources.
• The Organic Rankine Cycle is what is used to power the hotel and resort at Chena Hot Springs, which is the lowest temperature geothermal resource to be used for commercial power production in the world.
Why are we interested in the Organic Rankine Cycle?
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• Organic Rankine Cycle can use lower-temperature heat to generate power, enabling us to use energy resources that otherwise could not be tapped.
• This particular study examines using “waste heat” from a village power plant that would otherwise be vented.
• The rural villages in Alaska annually consume a total of about 370,000 MWh of electrical energy, which comes from individual diesel-fired generator sets
• During off-peak times, the generators are running at less than full capacity; the ratio of electrical power produced to fuel energy consumed is generally less than 40%.
• The rest of the fuel energy is lost as heat. While some power plants utilize a portion of this for other heating needs such as space and water heating, the majority of this energy in Alaska is wasted.
Why did we choose the Green Machine?
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• Using the Organic Rankine Cycle to extract power from either low-quality or secondary heat sources is a mature technology (first prototyped in 1961) in larger scales.
• However, utilizing an ORC on the small scales that would apply to an Alaskan village is new.
• The Green Machine is the ORC machine on the market that is the best fit for Alaskan conditions: • Small scale (50 kW target) • Robust design that transports well. • Does not require expertise to operate and maintain. • Maintenance requirements are infrequent and inexpensive.
• The Green Machine is estimated to increase overall fuel efficiency by 3-4%, and reduce CO2 emissions by 22.2 pounds for every gallon of diesel conserved.
Partnership with Tanana Chiefs Conference
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• The Tanana Chiefs Conference is a non-profit consortium of 42 communities in Interior Alaska.
• In 2010, ACEP partnered with TCC to obtain and test a 50 kW Green Machine under a grant from the Alaska Energy Authority.
• ACEP tested the Green Machine for 600 hours at the UAF power plant and collected and analyzed the data, finding promising results.
• TCC selected an Alaskan community whose power company would be willing to field test the Green Machine.
• The Green Machine will be installed into the Tok power plant in the Summer of 2013.
Reliability and Performance Testing
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• Reliability test was conducted for 600hr – at full load of the power unit i.e. 50kW output.
• Reliability test supply conditions: Hot water - 104.4oC (220oF) and 36.4m3/hr (160gpm) – cold water supply condition of 10oC (50oF) and 36.4m3/hr (160gpm).
• Performance test was conducted to evaluate the power unit at different heat source and heat sink conditions.
Hot water temperatures, oC
(oF)
Hot water flow rate, m3/hr (gpm)
Cold water temperatures, oC
(oF)
Cold water flow rate, m3/hr
(gpm) 68.33 (155) 27.25 (120) 10 (50) 27.25 (120) 79.44 (175) 36.34 (160) 20 (68) 36.34 (160) 90.56 (195) 45.4 (200) 45.4 (200) 101.67 (215) 56.8 (250) 107.22 (225) 68.1 (300)
Experimental Setup
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Consisted mainly of four components:
• Heat Source Loop
• Heat Sink Loop
• Electrical system
• Instrumentation
Experimental Setup – Heat Source and Heat Sink loops
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Experimental Setup – Electrical System
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Experimental Setup – Instrumentation
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Consisted mainly of three components:
• Parameters to be measured – Hot water flow rate, inlet and outlet temperatures to power unit; Cold water flow rate, inlet and outlet temperatures to power unit; Electrical power output of power unit; Electrical power consumed by power unit pump, Hot water pump power, and Cold water pump power.
• Instrumentation – Type-K thermocouples, flow meters and electrical meters were installed.
• Data Collection – NI DAQ system was used – 30min data collection at 1sec interval - Stored in excel format.
Data Reduction
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Total component cost Steam loop cost = 8997.22 Power unit cost = 119388.00
Hot water loop cost = 16762.03 Cold water loop cost = 14613.57 Electrical system cost = 3567.91 Instrumentation cost = 21246.25
Structural material cost = 5409.22 Miscellaneous parts and other costs = 948.38
Maintenance parts – One-time cost= 415.94 Total component cost = 191348.52
• Operating power output (𝑃𝑂𝑂) = 𝑃𝑁𝑁𝑁 − 𝑃𝑂𝑃𝑃𝑃,𝐶𝐶
• For estimating fuel saved – 3.7kWh/lit (14kWh/gal). • 363 power unit working days per year with two days for maintenance. Economic Analysis • Initial capital ($280,500) = Component cost ($191,500) + Installation cost ($89,000) • Annual maintenance cost = $7,600 • Diesel fuel cost = $5/gal
Reliability Test Results
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Reliability Test Results
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Reliability Test Results
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Parameter Value Average hot water supply temperature to power unit (𝑇𝐻𝐶,𝑖𝑖,𝑂) 104.2oC (219.7oF)
Average hot water flow rate to power unit (𝑉𝐻𝐶) 36.28m3/hr (159.8gpm) Average cold water supply temperature to power unit (𝑇𝐶𝐶,𝑖𝑖,𝑂) 9.7oC (49.4oF)
Average cold water flow rate to power unit (𝑉𝐶𝐶) 37.15m3/hr (163.6gpm) Power unit electrical power output (𝑃𝑁𝑁𝑁) 47.8kW
Power unit pump power consumption (𝑃𝑂𝑃𝑃𝑃,𝑂) 3.61kW Hot water pump power consumption (𝑃𝑂𝑃𝑃𝑃,𝐻𝐶) 1.76kW Cold water pump power consumption (𝑃𝑂𝑃𝑃𝑃,𝐶𝐶) 1.76kW
System operating power output (𝑃𝑂𝑂) 46.04kW Heat supply by hot water to power unit evaporator (𝑄𝐻𝐶,𝑆𝑃) 610.4kW
Screw expander efficiency (𝜂𝑆𝑆) 8.4% Power unit efficiency (𝜂𝑁𝑁𝑁) 7.8%
System operating efficiency (𝜂𝑂𝑂) 7.5% Diesel fuel saved per year (𝐹𝑆/𝑌) 106,060.2Lit (28,018.12gal)
Dollar amount saved on diesel fuel per year (𝐹$/𝑌) $140,090.6/year Emissions reductions
Oxides of nitrogen (NOX) 1372.8kg/year (3026.7lb/year) Hydrocarbons (HC) 156.9kg/year (345.9lb/year)
Particulate matter (PM) 39.2kg/year (86.5lb/year) Carbon monoxide (CO) 1372.8kg/year (3026.7lb/year) Carbon dioxide (CO2) 282135.5kg/year (311tons/year)
Payback period Payback period @ 0% interest on capital 2years Payback period @ 10% interest on capital 2.3years
Performance Test Results – Heat Input
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Performance Test Results – Heat Rejected
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Performance Test Results – Operating Power Output
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Performance Curves – Heat Input
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Performance Curves – Heat Rejected
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Performance Curves – Operating Power Output
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Performance Curves – System Operating Efficiency
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Performance Curves – Payback Period
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Performance Curves – Annual CO2 Reductions
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Example using Performance Curves • 2MW Diesel engine located in Tok, Alaska was selected for evaluation.
• Tok annual electrical load is 10,902.6MWh in 2011. Average engine load 1700kW.
• Year round ground water temperature in Tok 10oC (50oF)
Diesel Engine Caterpillar C175-16 Brake power 1.9MW (2588BHP)
Number of cylinders 16 Compression ratio 16.7
Speed 1200rpm Jacket water temperature 90.5oC (195oF)
Jacket water flow rate 120m3/h (528gpm) Aspiration Turbocharged (no EGR)
Percent load
Brake power, hp (MW)
Diesel fuel consumption,
lit/s (gpm)
Heat rejection to jacket water,
kW
Exhaust temperature,
oC
Heat present in exhaust at
176.6oC (350oF), kW
100 2588 (1.9) 0.131 (2.08) 1009.3 417.8 (784.04) 869.9 75 1941 (1.4) 0.101 (1.61) 753.9 404.1 (759.38) 686.7 50 1294 (1.0) 0.070 (1.12) 510.4 398.6 (749.48) 478.3 25 647 (0.5) 0.040 (0.63) 294.1 340.4 (644.72) 231.3
65.7 1700 (1.3) 0.090 (1.42) 663.2 402 (755.6) 609.1
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Example using Performance Curves Parameter Jacket water heat only Jacket water + Exhaust heat
Hot water supply temperature to ORC power unit 90.5oC (195oF) 107.2oC (225oF)
Hot water flow rate to ORC power unit 45.4m3/h (200gpm) 45.4m3/h (200gpm)
Heat input to evaporator of ORC power unit 477.3kW 617.7kW
System operating power output 33kW (288.2MWh/year) 45.7kW (398.5MWh/year) System operating efficiency 7% 7.4%
Diesel fuel saved 77930lit/year (20588gal/year) 107760lit/year (28460gal/year) Dollar amount saved on diesel
fuel $103000/year $142350/year
Payback period @ 0% interest 3years 2years Payback period @ 10% interest 3.6years 2.3years Reductions in CO2 emissions 230 short-tons/year 316 short-tons/year Reductions in NOX emissions 2225 lb/year 3075 lb/year Reductions in HC emissions 255 lb/year 350 lb/year Reductions in CO emissions 2225 lb/year 3075 lb/year Reductions in PM emissions 65 lb/year 90 lb/year
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Conclusions • Application of this 50kW ORC power unit for waste heat recovery application
from stationary diesel gen-sets is expected reliable and feasible in rural Alaska as the maintenance requirement and level of expertise required to operate the power unit is expected minimal.
• Performance curves were plotted for heat input to evaporator, heat rejected to cold water, system operating power output, efficiency, payback period and CO2 emission reductions with respect to hot water supply temperature for 10oC and 20oC cold water supply temperatures respectively.
• Considerable amount of annual emissions and CO2 (GHG) reductions could be obtained if the ORC power unit was operated year round on waste heat from diesel engines.
• Considering the 370,000MW-h of electrical consumption of whole Alaska and taking 38% fuel efficiency of diesel engine, nearly 486,800MW-h of heat energy is present in jacket water and exhaust heat. Using this waste heat, at 7% ORC efficiency, about 34080MW-h of electricity can possibly be generated which would increase the diesel engine fuel efficiency to 41.5%, with CO2 reductions of 27000short-tons/year, fuel savings of 9214800lit/year (2434300gal/year) and fuel cost savings of $12,171,500/year.
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Take-Homes • The Green Machine ORC system appears to be a good candidate
for Alaskan applications. • Efficiency of a diesel power plant may be improved by about 10% (i.e.
about 4% of fuel efficiency) using an Organic Rankine Cycle (ORC) system, using waste heat contained in diesel engine jacket water and exhaust.
• The system is considered very reliable; under normal operating conditions, no technical problems are expected for long-term operation; moreover, no advanced technology background is needed for operation and maintenance.
• Based on the reliability testing results (at full capacity of the Green Machine), the estimated payback time is 2.1 years for a 0% interest rate and 2.4 years for a 10% interest rate.
• Field testing will take place this summer of 2013 in the Tok power plant. We are very excited!
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Acknowledgements • Authors gratefully acknowledge the financial support provided by
Alaska Energy Authority, Denali Commission, and Alaska Department of Environmental Conservation.
• Authors would also like to thank Gwen Holdmann, Brent Sheets and Ross Coen from Alaska Center for Energy and Power for providing managerial assistance to complete this project on time.
• Authors acknowledge ACEP for providing tools and equipment for installation, UAF Power Plant for providing lab space for performing the experiment and UAF Facilities Services for providing personnel during installation of tough and heavy components.
► Alaska Center for Energy and Power ► Tanana Chiefs Conference ► Alaska Energy Authority
Participants & Funding Sources
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Performance Curves – Payback Period - $3/gal
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Performance Curves – Payback Period - $10/gal
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