Introduction

Conclusions

Atmospheric Effects of a Hydrogen Economy

One of the goals of a hydrogen economy is to improve the atmospheric problems caused by burning fossil fuels. However, the effects of this switch on the atmosphere are unclear. This section discusses hydrogen currently in the atmosphere, some of the major problems in the atmosphere today, and the impact of a hydrogen economy on these problems. It is impossible to know exactly how a hydrogen economy will affect the atmosphere until many years after its implementation. However, computer modeling experiments are being carried out to try to predict the impact on the environment. The major problem with computer modeling is that different assumptions are made on the variables, which lead to different conclusions. Two such variables are the amount of hydrogen which would be released into the atmosphere from hydrogen leaks, and the amount of reduction of the combustion of fossil fuels. The following paragraphs summarize the effects of these two uncertain variables on the major atmospheric problems.

Hydrogen Gas Leaks

There are a lot of uncertainties in predicting the effects of hydrogen leaks on the atmosphere. One of the uncertainties is how much hydrogen will be released. Hydrogen is a product of combustion reactions, so there is currently hydrogen released to the atmosphere. Therefore, if hydrogen leak levels are low and hydrogen is produced without using combustion, then there might actually be less hydrogen gas released to the atmosphere than there is today. However, current leak rates during hydrogen transportation are around 10-20%, and right now the easiest way to make hydrogen is using energy from combustion. In a world primarily powered by hydrogen fuel, there would be approximately 60-120 Tg of hydrogen released per year, which could have significant effects on the atmosphere [1].

One of these effects is that hydrogen reacts with hydroxyl radicals to produce water. Hence if there is more H2 in the stratosphere, it will react with hydroxyl radicals so there will be more H2O in the stratosphere. Modeling studies show that this increase in H2O will cool the lower stratosphere, which could increase the size of the hole in the ozone layer. More water in the atmosphere could also lead to more cloud formation in the upper atmosphere, which could increase the albedo, thereby decreasing the amount of sunlight that makes it to the Earth’s surface [1]. Furthermore, the oxidation of H2 to H2O uses hydroxyl radicals. This will affect the lifetime of other gases in the atmosphere, which could contribute to the greenhouse effect [2], [3].

 

Reduction of Combustion

Hydrogen could be produced using renewable energy sources and its energy could be utilized with fuel cells. If using hydrogen as a fuel currency reduces the amount of combustion, then there will be less NO_x produced. This would have positive consequences on the atmosphere, such as less ozone destruction in the stratosphere, and negative consequences, such as fewer hydroxyl radicals [3].

Sources:

1. Tromp, T.K., et al., Potential environmental impact of a hydrogen economy on the stratosphere. Science, 2003. 300: p. 1740-1742.

2. Prather, M.J., An environmental experiment with H₂. Science, 2003. 302: p. 581-582.

3. Schultz, M.G., et al., Air pollution and climate-forcing impacts of a global hydrogen economy. Science, 2003. 302: p. 624-627.