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December 7th, 2016
MEEN 475 – 502Section Instructor: Dr. Tanil Ozkan
TeamGus GremillionRyan Gautier
Nick AlbertJacob WalterSerdar Ozguc
Cory LuskZach Gregory
Compressed Air Energy Storage
Introduction - Compressed Air Energy Storage (CAES)
• CAES is an alternative form of energy storage to fossil fuels and chemical batteries
• Up to 30 year lifespan with minimal environmental impact
• Current implementations – Storage in large underground salt caverns
• No small-scale systems currently in use
• Issue: Diabatic compression produces low efficiency values
• Solution: Improve storage efficiency by reducing thermal losses
• Objective: Perform materials selection for a household-scale adiabatic CAES system
[2]
System Specifications
• Energy capacity: 7.2 kWh• 12 hour household consumption
• 2 components• Load-bearing pressure vessel shell
• Yield Failure SF = 4 (typical of pressure vessels)• Thermal insulation
Storage Tank
Compressor(Adiabatic Compression)
Electric Power
Valve
Outlet to turbine (electric power) or drive shaft (mech.
power)
Thermal energy loss through tank shell
Temperature Requirements
• Internal temperature = 675°C
• Adiabatic compression
• Yield Failure SF = 4
• Minimum Insulation Service Temperature = 675°C
• Minimum Shell Service Temperature = 300°C
• Permits consideration of most steels
[1]
Shell Material Selection
Function ● Pressure Containment
Constraints ● Ensure leak before yield failure or fracture failure
● Radius-Thickness Ratio = 10● Operating Temperature ≥ 300°C
Objective ● Maximize Safe Internal Pressure● Minimize Shell Thickness
Free Variables
● Material● Wall Thickness
[1]
Thermal Insulation Material Selection
Function ● Thermal Insulation
Constraints ● Operating Temperature = 675°C
Objective ● Minimize Thermal Energy Losses
Free Variables
● Material● Wall Thickness
[1]
AHP Analysis
• Shell Material Candidates:• Inconel Nickel Alloy• Grade 304 Stainless Steel• SA516-70 Carbon Steel• ASTM A841 Alloy Steel
• Insulation Material Candidates:• Fiberfrax Ceramic Fiber
Blanket• Dense Brick• Sandstone
AHP Results
Shell Material: • SA516-70 Steel has the highest score, however 304 Stainless Steel
is close and have higher operating temperature. With Stainless Steel, insulation can be placed outside the vessel.
Insulation Material:• Fiberfrax S Durablanket wins, mainly due to low thermal
conductivity.Material properties from: [4, 5, 6, 7, 8, 9, 10, 11, 12]
Shell Manufacturing Process Selection
ProcessShapeFlat Sheet
Dished Sheet
Mass1000-2000 kg
Section Thickness
40-70mm
Economic Batch Size
~1000 Units
Sand Casting X ✔ ✔ ✔
Die Casting X X X X
Investment Casting X X X ✔
Forging X ✔ ✔ ✔
Sheet Forming ✔ X X X
Powder Methods X X X X
Electro- Machining X X X X
Conventional Machining ✔ ✔ ✔ ✔
[1]
Preliminary Calculations
• Assuming the vessel is designed with a radius-thickness ratio of 10 and a yield safety factor of 4, the maximum allowable pressure was found to be 7.25 MPa.
• The temperature of atmospheric air compressed adiabatically was calculated to be 675 oC. Initial temperature and pressure are taken from the room condition.
Stress State Analysis
• Hoop stress and axial stress can be simplified with thin wall assumption.
• Ductile materials tend to fail due to shear. Hoop stress and axial stress are the principle stresses. Maximum shear stress can be calculated.
• Shear strength of steels can be estimated by using their yield strength. Estimated shear stress is higher than the maximum shear by a factor of 9.28.
Vessel Joining: Welding[13]
• The longitudinal welds take only the the hoop stress from the internal pressure; circumferential welds take the tangential stress.• Annealed properties of 304 stainless steel was used for the stress state analysis, thus welded joints are strong enough to carry the hoop stress and the maximum shear stress.•Cylindrical shell will be joined using double butt welds; hemispherical heads will be joined using lap welds.
[14]
Energy Analysis
• Energy required for 12 hours at a standard home is 7.2 kWh. Using the pressure of 7.25 MPa and 675 oC, specific internal energy of ideal air was found. Using density of air at 675 oC, required volume was estimated to be 1.94 m^3.
• Using this volume and 0.6 m radius corresponds to a pressure vessel length of 2.13 m.
• Radius to thickness ratio of 10 was used, thus wall thickness of the shell is 6 cm.
• Resulting mass for the shell is around 3900 kg.
Specifications
• Vessel Shell
• Material: Grade 304 Stainless Steel
• Section Thickness: 6 cm
• Mass: 3900 kg
• Thermal Insulation
• Material: Ceramic Fiber Blanket
• Section Thickness: 25 cm
• Outer Temperature: 53°C [3]
• Joining Method: Fasteners
Future Work
• Design vessel to meet ASME Section VIII Division 1 specifications
• Account for thermal stresses in vessel• Account for irreversibility in air
compression and expansion
Questions?
References[1] Materials and Process Selection Charts. Granta Design.[2] http://phys.org/news/2010-03-compressed-air-energy-storage-renewable.html[3] https://www.unifrax.com/wp-content/uploads/2015/05/Form-C-1421Blanket-Mat-12-14.pdf[4] http://thermal-industrial-ceramic-products.thermalproductsco.com/viewitems/thermal-products-fiberfrax-blankets/durablanket-2300f-ceramic-fiber-blanket-insulation[5] http://www.engineeringtoolbox.com[6] http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=NINC33[7] http://www.sandia.gov/matlsTechRef/chapters/SAND2008_1163.pdf[8] http://www.sciencedirect.com/science/article/pii/S026130691400199X[9] http://www.azom.com/properties.aspx?ArticleID=965[10] https://www.metalprices.com/metal/super-alloys/super-alloy-inconel-625[11] http://www.sciencedirect.com/science/article/pii/S0013794403002911[12] https://secure.anvilfire.com/thermal-ceramics-cerablanket.html[13] http://www.learneasy.info/MDME/MEMmods/MEM30006A/Pressure_Vessels/Pressure_Vessels.html[14] “Storage Tanks Detailed Analysis Report”.
Shell Material Index Derivation
Stress Intensity of a crack:
Fracture stress limit:
Yield before break:
Max stress in thin-walled pressure vessel:
Ductile failure prevented if:
Allowable pressure:
Thermal Insulation Material Index Derivation
Heat conduction:Heat stored:Total heat loss:
Total heat loss: