Rule #1 of deploying hydrogen: Electrify first

By Eriko Shrestha and Tianyi Sun  

There is extraordinary excitement today over zero and low carbon hydrogen. But can it live up to the silver-bullet hype? 

Case in point: Evidence indicates that in certain applications, green hydrogen made using wind or solar power could indeed yield a big climate benefit over fossil fuels. And in applications where other clean alternatives are lacking, it could be one of our best decarbonization tools.  

But producing hydrogen, green or blue,  requires a lot of energy. We did the math for two widely talked about use cases, replacing fossil fuels with green hydrogen for home heating and road transportation, and found green hydrogen on average requires three to seven times more energy than direct electrification. 

Molecules vs. Electrons 

To understand the tradeoffs, we compared the total energy required to perform the same tasks using either green hydrogen or direct electrification.  

Our team looked at home heating and road transportation because both can be powered by either green hydrogen or direct electrification; the technologies are already on the market or will be commercialized within this decade; and because there is sufficient energy data in existing scientific literature for a robust evaluation.   

Across the board, results show that direct electrification is the much better option for decarbonization. Direct electrification can maximize the number of homes and cars benefitting from clean energy; achieve faster decarbonization; and save money compared to green hydrogen, given our still limited renewable energy capacity. 

Energy intensity ratios of green hydrogen to direct electrification for different technologies. The full pathway (production, transport, delivery, and end-use) energy intensity of each use case is defined as the renewable energy required at the source (e.g., the electricity from a solar or wind farm) divided by the energy output to power an application. Median estimates of energy intensity ratios are represented by circles and full ranges of estimates are represented by the horizontal bars. The process energy efficiency ranges are from existing literature. More details on methodology can be found here.

Hydrogen home heating: 7x more renewable energy required on average

Using green hydrogen in combustion boilers — as with natural gas today — has been widely discussed as a low-carbon alternative for home heating. But we find that electric heat pumps can do the job better in all but the most extreme climates (below -10°F (-23°C). They are highly efficient – so much so that their efficiency can exceed 100%, because they can capture ambient heat from the air or ground (and do the reverse for cooling).

Comparing the energy intensity — the ratio of energy required for green hydrogen compared to direct electrification (see here for data)— we found that a green hydrogen boiler can require on average seven times (and up to 16 times)  as much renewable energy as heating via a heat pump to do the same job. This aligns with other published research (e.g. Ueckerdt et al., 2021) which finds that the hydrogen-based e-fuel pathway for gas boilers use 6 to 14 times more energy than electric heat pumps.

Hydrogen road transportation:  3-4x more renewable energy required on average

We’ve long heard about cars, trucks and other vehicles using hydrogen fuel cells that convert onboard hydrogen into electric power to drive the vehicle. Fuel cells can be used across a range of transportation modes, including light-duty vehicles, heavy-duty trucks, and transit fleets. There’s even a fuel cell-powered locomotive.

These applications can also be electrified directly using batteries or — for trains — the overhead wires already used in many places. Based on data from available scientific literature and hydrogen supply chain models, we calculate that it requires on average three- to four times (and up to nine times) the energy to power a green hydrogen fuel cell vehicle as it does a battery electric one.

(This assumes hydrogen is transported from production to refueling sites as a liquid. Moving hydrogen as a gas would still require more energy overall than direct electrification.) 

In addition to the energy needed to convert renewable electricity into hydrogen fuel — and then back again in the case of fuel cells — it can also involve additional energy-intensive processes, such as compressing and or liquefying hydrogen for transport and storage. 

Renewable electricity, on the other hand does not require conversions into a different state and is less energy intensive for transmission, distribution, and end use.  

Hydrogen’s own warming power

What’s more, hydrogen itself has powerful indirect warming effects when released into the atmosphere – a crucial fact that even experts underestimate. Based on the latest science, the actual warming power of hydrogen in the atmosphere is two- to six times higher than standard estimates (depending on the timeframe). 

That means that when compared pound-for-pound over a 20-year timeframe, hydrogen has 30 times the warming power of carbon dioxide, which can severely undermine the intended climate benefits of hydrogen in the near-term. 

This powerful warming effect happens no matter how the hydrogen is produced. And because hydrogen molecules are so small, it is highly prone to leakage. If production and distribution systems aren’t managed properly, even “clean” hydrogen could increase warming for decades relative to the fossil fuel it replaces. 

Bottom line 

Global renewable energy supplies continue to grow at a remarkable rate, but we’re still a long way from displacing fossil fuels. In a world where renewable capacity is constrained and demand is rising, we need to maximize the climate benefit of every electron.  

The story is different when it comes to those industrial uses and challenging transport applications where direct electrification or other alternatives are infeasible. Here, green hydrogen could be exactly what we need. But we think it’s a bad idea for green hydrogen production to compete with electrification in cases where direct electrification is readily available.   

Taking into account our analysis and the potential for green hydrogen, here are our suggestions for its use:  

• Assess how to produce green hydrogen using excess electric power that would otherwise be curtailed, or with new solar or wind energy, so that it is not diverting clean power away from other applications.  
• Control hydrogen emissions from both leaks and operational venting and purging. Development of detection technologies and implementation of best practices and mitigation efforts require further research. 
• Use practices that improve the energy intensity of hydrogen by co-locating hydrogen production near the end-uses  to reduce distribution and conversion energy losses. Clustering can also help minimize hydrogen leakage. 

For more information on the methodology and literature behind this analysis, click here.  

Research for this blog was done with support from Naomi Cohen-Shields and Grace Endy.