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: