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Hydrogen Storage Tanks: The Types, The Pitfalls, and the Solutions.
Why Are Hydrogen Storage Vessels so Popular?
With growing interest in lowering carbon footprints, Hydrogen Storage Tanks are rising in popularity. Political and business entities are on-board with this activity, pushing the envelope for Hydrogen’s uses in everyday society by enacting new policies and initiatives. However, Hydrogen Storage comes with specific challenges. For one thing, how do you select the type of Hydrogen Storage Tank for your application? What materials should you utilize? How can you prevent Hydrogen Embrittlement? Read on to find the answers and see how Didion Vessel can assist you in designing and manufacturing your storage tanks.
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The Basics About Hydrogen Storage Tanks
Hydrogen is naturally gaseous at room temperature and has a lower density and higher mass than other fuels. So, how can it be efficiently stored? One way is by changing Hydrogen’s external physical conditions (such as lowering the temperature and/or increasing the pressure). Much thought is being put into making Hydrogen storage vessels more compact and economical. What are some types of Hydrogen Storage Tanks?
TYPE I Hydrogen Storage Vessels: All Metal Design
This type of Hydrogen Tank is the least expensive to manufacture, is fabricated from an all-metal cylinder, and can be built to huge sizes. These are the heaviest Hydrogen Storage Tanks and usually operate at lower pressures than the other types of vessels listed.
Standard ASME Section VIII, Division 1 tanks typically have a maximum pressure of 3,000 psi (200 Bar). However, tanks built to ASME Section VIII Division 2 or 3 can have pressures up to and beyond 15,000 psi (1,000 Bar).
The mass of the metal required to contain the pressure in a Type I Tank usually only allows for 1% to 2% hydrogen storage compared to the cylinder mass. So, the mass of hydrogen stored to the mass of cylinder ratio is very low. While these vessels are large and have a big footprint, they are the most cost-effective solution.
The Type I Hydrogen Tanks also include liquid hydrogen storage vessels or Cryogenic Dewars. The benefit? The high density of liquid allows more Hydrogen to be stored while minimizing the vessel’s size. These vessels are more expensive than the Type I Gaseous Storage Tanks and come with a hurdle: BOG.
Boil-off gas (BOG) is a unique challenge to cryogenic liquids. To remain in its liquid phase, hydrogen must maintain cryogenic temperatures. If temperatures rise in the vessel, the hydrogen will boil, changing from a compact liquid into an expanding gas. The danger? If left unchecked, this will push your vessel beyond its design pressure.
Those who choose a Cryogenic Dewar must calculate the amount of insulation needed to keep their hydrogen at the correct temperature, minimizing BOG losses. Vents are also necessary, as they allow excess gas to escape. No matter how good your insulation is, there is will always be some BOG that must be vented.
Type II: All Metal With Carbon Fiber
These cylinders are all metal and are hoop wrapped (wrapped around the straight cylinder portion) with composite material. This type is similar to Type I in that the stored hydrogen mass to cylinder mass ratio is very low. These vessels are also heavy and thick-walled. Standard tanks usually have a maximum pressure of 4,500 psi (300 Bars).
Type III: Composite With Metallic Lining
This Hydrogen Storage tank has a much more efficient capacity: up to four times that of standard Type I vessels. This means smaller and lighter cylinders can be used to store the same amount of hydrogen. These vessels are fully wrapped composite cylinders and have a metallic lining. They are non-load bearing. Standard tanks usually have a maximum pressure of 10,000 psi (700 Bars).
Type IV: Composite With Non-Metallic Lining
This style has the same efficient storage capacity as the Type III’s. They are fully wrapped composite cylinders with non-metallic liners, usually consisting of some sort of polymer (like high-density polyethylene). Type IV Vessels are non-load bearing.
Standard tanks typically have a maximum pressure of 10,000 psi (700 Bars). Type III & IV tanks are the priciest of all the Hydrogen Storage Tanks due to the current expense of carbon fiber composite material. Although, many believe that the cost of carbon fiber will lower in the future.
Type III: Composite With Metallic Lining
This Hydrogen Storage tank has a much more efficient capacity: up to four times that of standard Type I vessels. This means smaller and lighter cylinders can be used to store the same amount of hydrogen. These vessels are fully wrapped composite cylinders and have a metallic lining. They are non-load bearing. Standard tanks usually have a maximum pressure of 10,000 psi (700 Bars).
Type III: Composite With Metallic Lining
This style has the same efficient storage capacity as the Type III’s. They are fully wrapped composite cylinders with non-metallic liners, usually consisting of some sort of polymer (like high-density polyethylene). Type IV Vessels are non-load bearing.
Standard tanks typically have a maximum pressure of 10,000 psi (700 Bars). Type III & IV tanks are the priciest of all the Hydrogen Storage Tanks due to the current expense of carbon fiber composite material. Although, many believe that the cost of carbon fiber will lower in the future.
Didion Vessel: Your Type I Hydrogen Storage Tank Solution
We are uniquely qualified to manufacture Hydrogen vessels. Why? We have experience in building these for customers such as NASA. We are one of few certified to build to ASME Section VIII Division 3, which includes the ability to meet Article KD-10 requirements. This allows us to manufacture Type I vessels at much higher pressures than most.
Within this ASME division and article, special attention is given to Fatigue Life Evaluation Using Fracture Mechanics, Vessel Material Qualification, and Fatigue Crack Growth Rate tests. These are all invaluable steps for lowering the risk of Hydrogen Embrittlement, keeping your equipment and employees safe.
Stop Hydrogen Embrittlement Before it Starts
Hydrogen Storage vessels are especially susceptible to embrittlement. How can you minimize this? By controlling the hydrogen factors, stress factors, and vessel material factors.
- Hydrogen factors include things such as the pressure, temperature, and purity of the gas.
- Stress factors include externally applied stresses, such as maximum applied stress, number of cycles, stress risers, etc. They also have internal residual stresses developed during processes such as fabrication, welding, or heat treating.
- Material factors primarily involve selecting a material with excellent hydrogen resistance at your operating pressure and temperature
It’s essential to get these factors right when planning and building your Hydrogen Storage Tank system. Didion Vessel can help give you guidance in this process. Consider the following:
Selecting the Proper Materials
We can help you select the right material for the operating pressure and temperature of your application by identifying materials with the right combination of needed tensile strength and hydrogen resistance. Hydrogen resistance is determined by Fracture mechanics tests performed on specimens that are soaked in high-pressure gaseous hydrogen for up to 5,000 hours in some cases.
Proper Welding Procedures
We will use welding procedures that are proven to be hydrogen resistant in the same fracture mechanics testing that we perform on the base material. We also take great care is to avoid hydrogen pickup during the welding process, by selecting the proper shielding gas, using dry welding electrodes, and properly cleaning the weld joint.
Minimize Stress Factors
We will design your vessel in a way that maximizes the number of operation cycles your hydrogen storage tank can be rated for, and take safety and cost into consideration. Reducing the maximum applied stress, minimizing stress risers, and carefully considering the fabrication plan are all ways of accomplishing this.
Feel free to contact us for assistance at 419-483-2226, sales@didionvessel.com.