Hydrogen as a alternative energy source.

Hydrogen as a alternative energy source

I am thinking of using hydrogen to store my Solar and Wind energy in place of batteries.

There seems to be workable hydrogen electrolyze to generate hydrogen and then storing it into storage Cartridges.

I then would use a fuel cell to turn the hydrogen back into electricity.
The equipment is very expensive and need to calculate the efficiency and return on investment and will publish my results.

1. Selecting your hydrogen electrolyzer.
2. Selecting your hydrogen storage Cartridges.

Hydrogen gas has good energy density by weight, but poor energy density by volume.
Liquid hydrogen has less energy density by volume than hydrocarbon fuels such as gasoline by approximately a factor of four. This highlights the density problem for pure hydrogen: there is actually about 64% more hydrogen in a liter of gasoline (116 grams hydrogen) than there is in a liter of pure liquid hydrogen (71 grams hydrogen). This means you need big tanks but it is not very heavy.

    3.  Selecting your hydrogen fuel cell.

Benefits using Hydrogen as energy store compared to battery.

1. Clean energy storing not battery (battery acid, Lead)
2. Energy can be stored for as long as the container can retain the Hydrogen gas.
3. Battries cant store the energy for ever (Batteries do loose there charge over time so you can’t store the battery charge for a long time)
4. Batteries has a limited amount of charge and discharge cycle and therefore needs to be replaced after reaching cycle limit.

Disadvantage of Hydrogen.

1. Hydrogen gas is very explosive and should be handled with care.
2. The conversion from electricity to Hydrogen and back to Electricity is not very efficient yet.
3. The Hydrogen electrolyzers and fuel cells is very expensive.

Disadvantages of fuel cells

1. High cost of ownership (~R150,000,00 for 5kW)
2. High running cost (~R21 per kWh)
3. Monthly rental of H2 Cylinders (~R77 per  cylinder x 6)
4. Not maintenance free, requires yearly maintenance
5. Low energy density of Hydrogen (~10kWh per cylinder)
6. Refueling of Hydrogen remains a challenge, have to
7. swap/replace heavy cylinders. (~70kg each) 

Storage Tanks

Compressed hydrogen storage tanks are the most popular now since they don't require the super-cooling and super-insulation that liquid hydrogen does. Compressing hydrogen fuel into storage tanks does represent its own unique challenges though. Unlike pressurizing natural gas, hydrogen is less dense and requires better seals. In addition, hydrogen storage tanks need to be made from lighter materials such as aluminum or carbon / graphite compounds.

Storing liquid hydrogen in automobile tanks takes special handling and materials to contain and keep the fuel cool. Hydrogen does not liquefy until -253°C (20 degrees above absolute zero) such much energy must be employed to achieve such temperatures. Approximately 30 to 40-percent of the energy content of hydrogen can be lost due to the storage methods. Safety becomes an issue with the handling of liquid hydrogen as does the car's tank integrity, when storing, pressurizing and cooling the element to such extreme temperatures.
Metal hydride tanks are perhaps the future for hydrogen storage for H2 cars. Metal hydrides are specific metallic compounds and alloys that act like a sponge to both absorb and release hydrogen at consistent pressures. The life of a metal hydride storage tank is directly related to the purity of the hydrogen that is absorbed. As the metallic alloys sponge up hydrogen they also sponge up impurities as well, that will eventually clog up the tank.

1. Compressed gases: These are stored in a gaseous form at high pressures of up to 20 400 kPa in strong cylinders that contain no liquid phase.

1. Liquefied gases: These have properties enabling them to be relatively easily liquefied and stored under not excessively high pressures at ambient temperatures in cylinders containing both liquid and gas in equilibrium.

The greatest danger presented by bottled gases, which may become exposed to fire or be subjected to radiated heat, is that of explosion and possible fragmentation.

Cylinders can rupture as a result of increased internal pressure and/or the loss of tensile strength of the cylinder metal whether the contents are flammable or not.

Impact may result in rupture or may trigger progressive decomposition, which may ultimately cause the cylinder to explode, e.g. acetylene.

Gases are commonly stored in cylinders in two forms:

When cylinders are exposed to fire conditions, temperatures at which they would be in danger of bursting will rapidly be reached.

The following table is an extract from an article The Behaviour of Gas Cylinders in Fires by E G Butcher and C Cilsby, which appeared in the UK publication Fire, in May 1965.

Bursting temperatures

Cost of Hydrogen Cylanders from Afrox (2008)

Hydrogen Pricing
Cylinder rental / month R66.50 (6 cylinders = R399.00)
Refueling cost / cylinder R106.70 (3 cylinders = R320.10 per refueling)
Delivery charge R 3.50 / km (from closest Depot)
@ 5kw – 1 cylinder will provide ~2 hours of back-up power
or @1kw for 10 hours  back-up power from one cylinder.