This report describes how the electrolysis of water to generate hydrogen can be used in conjunction with renewable energy sources to provide a number of benefits. It begins with a brief summary of the fundamentals of water electrolysis and the available electrolyser technologies. It then looks at how electrolysis has been applied in the past and its applicability to, and suitability for, energy use.
One of the chief advantages of electrolysis is that it can be applied at a great range of scales. The report first examines its use at smaller scales, in off-grid or localised power generation, where it is a key component to enable smart, secure and flexible distributed energy systems that include renewables such as wind and solar power. True independence from the grid is difficult to achieve and in many instances electrolysis can be the crucial missing link.
One of the most exciting aspects of the technology currently is its emergence as a candidate for large-scale renewable energy storage – without a doubt one of the biggest challenges facing society in its efforts to move away from fossil fuels. Many nations support an increased contribution from wind and solar power, which are difficult to harness but potentially ‘unlimited’, unlike bioenergy. However, these sources provide a variable output which is difficult for the electricity grid to accept while maintaining its stability, and this places a real and fundamental limit on how much of this energy can currently be incorporated into the supply.
This limit can be circumvented if the renewable energy can be stored at times of excess production, buffering the effect of variability on the grid and providing a more predictable supply. But energy storage at the scale needed for a global shift away from carbon is a significant technological challenge that cannot be satisfactorily met with existing technology. As this report describes, using clean electricity to drive water electrolysis and produce hydrogen in large quantities as an energy storage medium is in fact one of the most viable options available to us.
Hydrogen’s advantages as a clean energy carrier are numerous because it can link all forms of energy use, allowing for greater integration, greater flexibility and greater efficiency overall. Hydrogen can be produced by electrolysis driven by either distributed renewables or grid electricity and then stored (in small or terawatt-hour-scale quantities and in a variety of ways). From there, it can fuel on-demand electricity or combined heat and power (CHP) generation, or it could instead be used in other ways: for example, as a vehicle fuel, or supplied to industry as a commodity or feedstock, or chemically combined with carbon to produce synthetic hydrocarbon fuels.
There are synergies to be explored; for example if hydrogen from electrolysis is used to renewably upgrade the carbon dioxide (CO2) fraction of biogas. Hydrogen can also be injected into the natural gas network, either in methanated form or directly, to increase the proportion of renewable energy in grid gas. Gas has been combusted for many years to generate electricity and heat, but electrolysis and hydrogen for the first time provide a link between the electricity and gas grids in the opposite direction.
These connections and synergies are the central theme of this report.
A list of electrolyser manufacturers can be found in our Industry Directory by selecting Electrolysers from the Technology tab in the filter.
2. Electrolyser Technology
2.1 General Principles
2.2 Proton Exchange Membrane Electrolysers
2.3 Alkaline Electrolysers
2.4 Solid Oxide Electrolysers
2.5 Reversible Fuel Cells
3. Application of Water Electrolysis
3.1 Existing Markets
3.2 Energy Applications
4. Electrolysers in Distributed Applications
4.1 Distributed Electricity Generation
4.2 Household and Building Energy
4.3 Autonomous Backup and Remote Power
4.4 Stranded and Localised Grids
Special Feature: German Hybrid Power Plants
5. Electrolysers and the Electricity Grid
5.1 Grid Requirements
5.2 The Renewables Challenge
5.3 Managing the Integration
5.4 The Role of Electrolysers
6. Markets for Hydrogen
6.1 Centralised Power Generation
6.2 Hydrogen Injection into the Natural Gas Grid
6.3 Hydrogen for Transportation
6.4 Production of Synthetic Fuels
6.5 Industrial Uses of Hydrogen