The 21st century is shaping up to be a period of intense expansion for the energy sector as governments, companies, and other organizations worldwide accelerate their efforts to meet minimums of global average temperature rise and reach sustainable net-zero carbon emissions goals. Meeting these goals will require massive investment and research across diverse fields such as renewable energy, carbon capture technologies, infrastructure, and energy storage (Megia et al., 2021).
Key stakeholders in this energy expansion have identified hydrogen energy as an important part of the emerging portfolio of technologies that will facilitate equitable and sustainable growth to meet global energy demands in the coming decades. Why hydrogen? Hydrogen is often talked about as a fuel, but scientifically it is a little different.
An Energy Carrier
Hydrogen is considered a secondary energy source when it is manufactured (using another energy source) and serves as an energy carrier. As an energy carrier, hydrogen stores, transports, and delivers energy that has been produced by other resources (solar, wind, fossil fuels, biomass, etc.), almost like a molecular battery.
How do we produce this hydrogen fuel? Today, hydrogen fuel can be produced through several methods. The most common methods today are natural gas reforming (a thermal process), and electrolysis. We will discuss these methods and other production methods in the next lesson.
Think of Hydrogen as a Battery
A helpful way to think about hydrogen is like a battery because:
- Energy (electricity) goes in → hydrogen is produced and the electrical energy is now locked as chemical bonds within the hydrogen molecules (H2) [=”charging” phase in the hydrogen energy cycle]
- Hydrogen bonds are broken, releasing energy → energy comes out [=”running” phase in the hydrogen energy cycle]
So, hydrogen is similar to a battery in that we can store energy (charge the battery), transport that stored energy (move the battery from one place to the next), and then liberate (deliver) the stored energy (run the battery) at a time when it is needed.
Hydrogen has the maximum energy content per mass of any known fuel (=high energy density), and the energy stored in its molecular structure does not dissipate over time, making it an efficient and long-lasting solution for energy storage and transportation.1Megía, P. J., Vizcaíno, A. J., Calles, J. A., & Carrero, A. (2021). Hydrogen production technologies: from fossil fuels toward renewable sources. A mini review. Energy & Fuels, 35(20), 16403-16415.
We will discuss more details about methods for “charging” the hydrogen battery and “running” the hydrogen battery in the next lessons.