# Basics

• Although hydrogen if a good fuel, its storage can be complicated. Thus this page was made.

# Cost

• Quote for a 350/700 bar type 3 80L tank is \$3150 below quoted
• Storage in this tank is 2.5 gal fuel equivalent at 350 bar
• Optimal conversion of fuel to electricity is 14 kWh_e/gal. See Fuel Consumption.
• Thus the storage cost is \$90 (tank alone, no plumbing) per kWh_e at these costs. Double pressure to 700 and add 100% for plumbing and cost is at \$90 for this storage, 4x less than Lithium Ion batteries, and equivalent to Saturated Water thermal storage.
• These are critical numbers to understand to transcend resource conflicts

# High Pressure Hydrogen Storage

• 350-700 bar - [1] - - \$3150 - 1400 gallons STP - 4.8 or 2.4 kg hydrogen at 700 or 350 bar. This is about 2.5 or 5 gallons of fuel equivalent. For a 100 mpg car, this is 250 or 500 mile range.
• Electrolyzers can produce hydrogen at pressure, so a compressor is not needed.
• A high pressure steel tank is about \$500 - [2]
• The simplest tank that can be used is a steel tank for up to 200 bar. This appears to be the lowest cost option. [3]
• Standard tanks are 55" high and 9" wide. with 45x9 inch usable size. 50L? - about 12 gallon, yes, 50L. If 200 atmospheres, that is 2400 gallon equivalent. 4 of these store 10000 gallons - 1.7 gallon gasoline equivalent - but the efficiency of a hydrogen engine is 2x that of gasoline, so it's effectively 3.4 gallons by comparison. That is acceptable for a microcar, though cylinder weight is 143 each or 572 lb for the tanks themselves - a significant tradeoff for a 750 lb microcar. In the first iteration, a microcar could use 1 of these as a proof of concept for a 100 mile designed range at 750 lb of weight.

## Calculations

• Compare to propane tank, 1000 gal, 100 PSI -

## Storage Tank Suppliers

• 700 bar, 20 gallon - [5]. RFQ submitted 1/27/18
• In-ground storage, 2200 PSI - 14"x40' - [6]
• Low, medium, and high pressure storage options - [7]
• Pictures of storage tanks - [8]
• Mahytec Storage

# Sorbent/Lattice Based Storage Methods

## Carbon

• SUPPOSEDLY Activated Carbon (and hyped carbon metamaterials) do this well?
• Investigation of room temperature hydrogen storage in biomass derived activated carbon sounds almost directly ose applicable
• The Paper's Abstract:
• "Overcoming the barrier of hydrogen storage is a promising avenue to a zero emission fuel economy. In the present study, we demonstrate that a balance between pore size, pore volume and large surface area of activated Carbon material helps in achieving increased hydrogen uptake at room temperature and moderate pressures. The activated carbon material, synthesized using a biomass precursor and the KOH activation process, furnishes a high surface area of ∼2090 m2/g and a pore volume of 1.44 cm3/g.The hydrogen adsorption studies exhibits a good hydrogen uptake capacity of ∼1.06 wt% at 15 bar equilibrium hydrogen pressure and 25 °C signifying that this activated carbon prepared using biomass Palimera sprout can be used for catalyst support material for enhancing the hydrogen uptake capacity by spill over mechanism."

### Napkin Math

#### Givens Used

• Activated Carbon has a density of ~2000-2100 kg/m3?
• Using 2000kg/m^3 for math
• And The Paper Said Activated Carbon has an uptake capacity of ∼1.06 wt% at 15 bar

#### User:Eric 's math attempt

• So a 1L tank or so should have ~0.001m^3 internal volume
• And 1000L would have ~m^3 internal volume
• Quick Search on 1g=1mole=how many liters of ambient ( STP ) hydrogen gas?
• So a 1 liter tank should hold ~2 grams of carbon?
• And a 1000L tank should hold 1 kilo
• 1gg of hydrogen2 = 44.8 Ambient Liters?
• So a 1 Liter Tank with Activated Carbon at 15 bar holds 2 grams, or 44.8 Ambient Liters of H2 Gas?

#### Comparison of this method to UHP

• 0.264172 L = 1 USG
• 3.78541 L = 1 USG
• 5299.576 L = 2400 USG
• 15 or so bar vs 700 or 350 bar
• ∼1.06 wt% (+ add 15 bar tank mass to the lower divide) vs 42 kg/m3
• User:Eric lost in conversion maths hell; HELP NEEDED

# Cryogenic Liquid Storage

• Ultra High Density
• Can be done using a Dewar, a pure hydrogen gas source, and a cheap cryocooler
• A diy cryocooler could possibly be made to reduce costs further

# Storage as a Synthesized Fuel

• Convert to Methane by the Sabatier Reaction
• That can be compressed/liquified as is or it could be further converted into other fuels:
• Methanol can be made from methane via the following process Listed Here
• Dimethyl Ether can be made from Methanol This Details How
• Dimethyl Ether Can be Catalytically Converted to Hydrocarbons such as Gasoline This Details How
• Hydrogen + Carbon Monoxide can be directly converted to hydrocarbons via the Fischer Tropsch Process

# Risks

1. Presentation to DOE from China, 2010, with links to contacts, https://www.energy.gov/sites/prod/files/2014/03/f12/cng_h2_workshop_4_zheng.pdf
2. Good overview, EU, With description of hydrogen storage cylinders , http://www.hyresponse.eu/files/Lectures/Safety_of_hydrogen_storage_notes.pdf
3. Lower Flammability limit 4%, http://www.hyresponse.eu/files/Lectures/Safety_of_hydrogen_storage_notes.pdf
4. Sales reflect acceptable safety with 20,000 fuel cell vehicles on the road and growing strong. https://www.statista.com/statistics/644545/global-sales-of-fuel-cell-vehicles/