The cycle in the figure has been explained during the lectures. It shows the route to convert the hydrogen produced by water splitting into natural gas. Energy Energy H2O Energy Electrolysis H2 CO2 Combustion Water Gas Shift CH4 02 Fisher-Tropsh CO Energy The following efficiencies are considered: • Electrolysis: 70% • Water-gas shift reaction: 75% ⚫ Natural gas storage and circulation: 80% • Fischer-Tropsch reaction: 80% • Combustion: 75% A) Based on these conversion efficiencies, calculate the efficiency of the complete process. Give the answer in [%]. Another version of a hydrogen cycle in a hydrogen based economy is to directly store and convert the hydrogen into energy, as in the scheme shown here. Energy Fuel cell Storage Energy H2O Electrolysis H2 02 The following efficiencies are considered: ⚫ Electrolysis: 70% • Natural gas storage and circulation: 70% • Fuell cell: 50% B) Calculate the efficiency of the complete process. Give the answer in [%].

The cycle in the figure has been explained during the lectures. It shows the route to convert the hydrogen produced by water splitting into natural gas. Energy Energy H2O Energy Electrolysis H2 CO2 Combustion Water Gas Shift CH4 02 Fisher-Tropsh CO Energy The following efficiencies are considered: • Electrolysis: 70% • Water-gas shift reaction: 75% ⚫ Natural gas storage and circulation: 80% • Fischer-Tropsch reaction: 80% • Combustion: 75% A) Based on these conversion efficiencies, calculate the efficiency of the complete process. Give the answer in [%]. Another version of a hydrogen cycle in a hydrogen based economy is to directly store and convert the hydrogen into energy, as in the scheme shown here. Energy Fuel cell Storage Energy H2O Electrolysis H2 02 The following efficiencies are considered: ⚫ Electrolysis: 70% • Natural gas storage and circulation: 70% • Fuell cell: 50% B) Calculate the efficiency of the complete process. Give the answer in [%].