Improved Utilization of Industrial Process Heat: Testing of a 50kW and 280kW Organic Rankine Cycle in Alaska using Heat Rejected from a
Stationary Diesel Power Plants
Vamshi Krishna Avadhanula§,†, Gwen Holdmann†, Chuen-Sen Lin§,†, Thomas H. Johnson†
§Department of Mechanical Engineering, †Alaska Center for Energy and Power
University of Alaska Fairbanks
Fairbanks, Alaska, USA
Experimental Setup
1. Heat Recovery in Alaska
Most of rural Alaska is powered by isolated dieselpowered generator sets, which run at less than full
capacity during off-peak times; the ratio of electrical
power produced to fuel energy consumed in generally less
than 40%. The rest of the fuel energy is lost in the form of
waste heat through the charge air cooler (after cooler), the
jacket liquid cooler, friction, and exhaust. This waste heat
has low heat flux value (amount of heat rate) and low
grade (i.e. low temperature) form of heat energy. Diesel
engine jacket liquid (usually water or glycol/water
mixture) and exhaust accounts for about 20% and 30% of
the total fuel energy respectively. Here it should be noted
that the size of diesel gen-sets vary from about 100kW to
3MW in electrical capacity. While some of that waste heat
energy is used for other heating needs such as space and
water heating [1], the rest is lost to atmosphere. The goal
of adding organic Rankine cycle (ORC) products to an
existing power plant is to reclaim some of this waste heat
to generate a bit more power which thereby increases the
overall efficiency of the power plant.
2. What is Organic Rankine Cycle?
As given in Figure-1, basic principle of ORC system is
similar to that of steam Rankine cycle system except that
the working fluid is organic (such as R134a, R245fa,
R123, ammonia etc.) instead of steam. The basic
components of ORC are pump, evaporator, expander, and
condenser. The liquid refrigerant from the condenser is
pumped at high pressure to evaporator. In evaporator the
refrigerant is heated to the required superheated or
saturated condition. This high pressure working fluid is
converted to low pressure liquid or vapor/liquid mixture
(to the condenser pressure) using an expander which is
connected to the generator to produce power. The low
pressure refrigerant from the expander is cooled to the
desired state in condenser and the liquid portion is again
pumped back to evaporator and the cycle continues.
Figure-1: Schematic of a typical organic Rankine cycle
3. Testing the 50kW Green Machine
ORC
Green Machine (GM) is a 50kW organic Rankine cycle
(ORC) system manufactured by ElectraTherm, Inc. which
could be a potential waste heat recovery application for rural
Alaska. Table below gives the characteristics of this 50kW
ORC power unit. Research team at University of Alaska
Fairbanks (UAF) has designed an experimental setup for
testing the Green Machine for reliability (endurance) and
performance. The purpose of this experiment is to collect
data with input matches the possible diesel engine waste
heat condition. The collected data could be used to estimate
the performance and economic benefit of installing this
power unit on individual village diesel generator.
#
1
2
3
4
5
6
7
8
9
10
11
Component
ORC power unit
Expansions joints
Solenoid valve
Ball valve
Steam trap
Drain
Temperature mixer
Ultrasonic flow meter
VFD Pump
Expansion tank
Rolairtrol air separator
#
12
13
14
15
16
17
18
19
20
21
22
Component
Pressure relief valve
Steam-to-hot water heat exchanger
Steam control valve with actuator
Manual control valve
Pump (Constant flow rate)
Hydrant source (Cooling water source)
Cooling water from GM (Hydrant sink)
By-pass for temperature control on coolant side
Steam inlet
Steam condensate outlet
3-way butterfly valve with actuator
#
23
Component
Check valve
Figure-4 GM ORC net power output and net efficiency versus hot water
supply temperature
5. General
Conclusions for
Application of ORC in WHR from
Diesel Gen-Sets
Figure-2 Experimental setup for testing 50kW ORC power unit
Data Reduction and Economic Analysis
• Operating power output (𝑃𝑂𝑂 ) = 𝑃𝑁𝑁𝑁 − 𝑃𝑃𝑃𝑃𝑃,𝐶𝐶 (Expander
power – ORC pump power – Cold water pump power)
• Assumed diesel engine fuel efficiency – 3.7kWh/lit
(14kWh/gal).
• 363 power unit working days per year with two days for
maintenance.
• Annual maintenance cost = $7,600
Results for Green Machine ORC
Green Machine ORC Reliability Test Results
Parameter
Value
Average hot water supply temperature to
104.2oC (219.7oF)
power unit (𝑇𝐻𝐻,𝑖𝑖,𝑃 )
Average hot water flow rate to power unit
36.28m3/hr (159.8gpm)
(𝑉𝐻𝐻 )
Average cold water supply temperature to
9.7oC (49.4oF)
power unit (𝑇𝐶𝐶,𝑖𝑖,𝑃 )
Average cold water flow rate to power
37.15m3/hr (163.6gpm)
unit (𝑉𝐶𝐶 )
Power unit electrical power output (𝑃𝑁𝑁𝑁 )
47.8kW
Power unit pump power consumption
3.61kW
(𝑃𝑃𝑃𝑃𝑃,𝑃 )
Hot water pump power consumption
1.76kW
(𝑃𝑃𝑃𝑃𝑃,𝐻𝐻 )
Cold water pump power consumption
1.76kW
(𝑃𝑃𝑃𝑃𝑃,𝐶𝐶 )
System operating power output (𝑃𝑂𝑂 )
46.04kW
Heat supply by hot water to power unit
610.4kW
evaporator (𝑄𝐻𝐻,𝑆𝑆 )
Screw expander efficiency (𝜂𝑆𝑆 )
8.4%
7.8%
Power unit efficiency (𝜂𝑁𝑁𝑁 )
7.5%
System operating efficiency (𝜂𝑂𝑂 )
Diesel fuel saved per year (𝐹𝑆/𝑌 )
106,060.2Lit (28,018.12gal)
Dollar amount saved on diesel fuel per
$140,090.6/year
year (𝐹$/𝑌 )
Emissions reductions
1372.8kg/year (3026.7lb/year)
Oxides of nitrogen (NOX)
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)
282135.5kg/year (311tons/year)
Carbon dioxide (CO2)
Payback period
Payback period @ 0% interest on capital
2years
Payback period @ 10% interest on capital
2.3years
Figure-5 GM ORC Payback period for Different ORC Power Outputs,
Fuel Prices, and Capital Costs
4.Field Application of 280kW UTC
ORC
A 280kW ORC power unit manufactured by United
Technologies Corporation was installed in a diesel
powerhouse in Cordova, Alaska in early 2013. The
specifications of the ORC and the EMD diesel engine are
given in Table-4 below.
UTC ORC SPECS
195oF Evaporator Inlet
Temperature
165oF Evaporator Outlet
Temperator
1100gpm Hot Water Flow Rate
EMD Diesel Engine SPECS
195oF Jacket Water Outlet
Temperature
165oF Jacket Water Return
Temperature
1150gpm Rated Jacket Water Flow
Rate
280kW Turbine Electrical Power
Output
3700kW Rated Power
260kW ORC Net Power Output
35kW Radiator Electrical Power
Consumption
1. From the above two ORCs, the application of this
technology for WHR from diesel engines, it was
observed that the SFC of diesel engine increased by
3.5% in both the ORC applications.
2. Application of 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.
3. The installation and operation costs of cooling system,
which depend on the availability of the type and
capacity of the cooling source at the test site, may
become one of the dominate factors for ORC
application.
4. 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.
Conclusions from Green Machine ORC
Testing
1. The effect of cooling water flow rate on GM
performance showed minimal effect for the range
tested.
2. Unless the GM power output is less that 10kW, a pay
back period of less than 10 years can be achieved.
3. 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 27000shorttons/year,
fuel
savings
of
9214800lit/year
(2434300gal/year) and fuel cost savings of
$12,171,500/year.
Conclusions from UTC ORC Testing
1. Average net power output of the UTC ORC is about
138.83kW.
2. Without ORC, the rated engine SFC is 13.82kWh/gal;
with ORC SFC is 14.32kWh/gal which is about 3.6%
improvement in SFC.
3. Payback period of less than 10years could be
achieved.
Green Machine ORC Performance Test Results
(Figure-3, Figure-4 and Figure-5)
Characteristics of the 50kW ORC power unit
Figure-8 UTC ORC Pay period for Different ORC Power
Outputs, Fuel Prices, and Capital Costs
Figure-6 Schematic for UTC ORC 280kW unit installed in Cordova, Alaska
Parameter
Limitation
Heat source supply
65.5oC (150oF) – 107.2oC (225oF)
temperature
Heat source supply flow
27.2m3/h (120gpm) – 68.1m3/h (300gpm)
rate
Heat sink supply
43.3oC (110oF)
temperature
Expander power output
10kW – 50kW
Expander rotational speed
4860rpm
Results for UTC ORC
Observations:
 28,546 kWh – ORC Power Production to Date
(4/24/2013)
 214 Total Turbine Run Time Hours (4/24/2013)
with ORC Online
Testing Schedule
The experimental setup was designed to perform reliability
and performance test on the 50kW ORC power unit.
Partnership with Tanana Chiefs Conference
(TCC)
• 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 50kW
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.
Acknowledgements
Reliability test is conducted at full load gross power output
of the power unit (i.e. 50kW screw expander power output)
for 600hrs at hot water supply condition of 104.4oC (220oF)
and 36.4m3/hr (160gpm) and cold water supply condition of
10oC to 20oC (50oF to 68oF) and 36.4m3/hr (160gpm).
• 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 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.
Table below gives the performance test schedule at which
the 50kW ORC power unit was tested.
Table Various hot water and cold water flow rates at which power unit
was tested for performance
Hot water
Cold water
Hot water flow
Cold water flow
temperatures,
temperatures,
rate, m3/hr (gpm)
rate, m3/hr (gpm)
oC (oF)
oC (oF)
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)
107.2 (225)
68.1 (300)
References
Figure-3: Green Machine ORC system operating power output vs. Hot
water supply temperature
1. Lin, C.S., “Capture of heat energy from diesel engine
exhaust”, Final report prepared for National Energy
Figure-7 UTC ORC operating power output and efficiency for various flow
Technology Laboratory, DOE Award # DE-FC26parasitic power versus jacket water supply temperature
01NT41248, November, 2008.
2. Avadhanula, V. K., Lin, C. S., Johnson, T., “Testing a
50kW ORC at Different Heating and Cooling Source
Conditions to Map the Performance Characteristics”,
SAE Technical Paper # 2013-01-1649, April 2013.