Efficiency Breakdown
1. Electrolysis (Electricity to Hydrogen)
- Current Efficiency: Traditional electrolysis methods, such as alkaline and PEM (Proton Exchange Membrane), typically exhibit efficiencies around 60-67%, meaning that for every unit of electricity input, only about 0.6 to 0.67 units of energy are stored as hydrogen. Newer technologies, such as solid oxide electrolysis, can achieve efficiencies close to 80% or higher under optimal conditions.
- Recent Innovations: A notable advancement comes from Hysata’s capillary-fed electrolyzer, which claims an overall efficiency of up to 95%, significantly reducing the energy required to produce hydrogen. This could potentially lower the energy consumption to around 41.5 kWh per kilogram of hydrogen produced.
2. Storage and Transport Losses
- Storing and transporting hydrogen incurs additional energy losses, typically about 10%. Compressing and transporting hydrogen requires energy that reduces the overall efficiency of the system further.
3. Fuel Cells (Hydrogen to Electricity)
- When converting hydrogen back to electricity using fuel cells, efficiencies range from 40% to 70%. Most commercial fuel cells operate around 50-65% efficiency when converting hydrogen back into electrical energy, although some combined heat and power (CHP) systems can achieve total efficiencies exceeding 90% when including heat recovery.
Overall Round-Trip Efficiency
The overall round-trip efficiency for the entire process of converting electricity to hydrogen and then back to electricity can be calculated by multiplying the efficiencies of each stage:
- Total Round-Trip Efficiency: When considering the losses in electrolysis, storage, and fuel cells, the total round-trip efficiency can range from 18% to 46% or higher, depending on specific technologies and conditions used for each step. For example, common estimates suggest that for every 1 MWh of electricity used to produce hydrogen, only about 0.18 to 0.46 MWh can be retrieved when converted back to electricity, particularly when using less efficient technologies.
In conclusion, while hydrogen has the potential to serve as a significant energy storage medium, its efficiency in the conversion processes currently falls short compared to other energy storage technologies like batteries, which can achieve efficiencies of around 90-99%. As technology advances, particularly in electrolyzers and fuel cells, these efficiencies may improve, making hydrogen a more viable option in the energy landscape.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-efficient-is-the-process-of-converting-electricity-to-hydrogen-and-back-to-electricity/
