Hydrogen Cars vs Electric Cars

With gas prices being so high, alternative fuel vehicles have become a popular topic. Two of the types of vehicles that tend to get a lot of press are the hydrogen fuel cell powered vehicles and electric powered vehicles. Both are lauded as the way of the future

But which of these two options are really has the better chance of being the car your children drive.

Let’s look at hydrogen fuel cells first. When burned in an engine, the only emissions giving off is water, so a hydrogen powered vehicle is a zero emission vehicle. Hydrogen is also a better fuel than gasoline, it actually has the highest energy content per unit of weight of any known fuel.

Hydrogen is also a very abundant element. While current methods for making hydrogen are done by using fossil fuels, such as natural gas, coal, and oil, American wouldn’t be dependent on foreign oil anymore. Also, hydrogen can be extracted from water, and we all know there’s a lot of water on this planet.

However, hydrogen is not without its share of drawbacks. Probably the biggest problem right now is that it would require an entire new infrastructure. While gas stations could be outfitted with hydrogen fueling stations that would take years. Also, the technology to store hydrogen efficiently is still not ready for prime time.

Then there’s the electric car. Electric cars can also be considered zero emission vehicles since they give off no emission when running. However, electric cars do require power from the electric grid, which does give off emissions. As the electric grid gets cleaner, though, so do electric cars, and electric powered cars are substantially less polluting than gasoline powered cars due to the fact that power plants are far cleaner and more efficient than an internal combustion engine in a vehicle.

The technology for mainstream electric cars is also not quite ready for all the major manufacturers to stop making gasoline powered cars, but it’s much closer than hydrogen currently is. The challenge with electric cars right now is the batteries. The batteries are both expensive and current models, like the Tesla Roadster, have a range of only 250 miles – great for commuting, but not so good for road trips. The other problem is the length of time these vehicles take to charge. It’s not simply a matter stopping at your local power station and plugging in for five minutes and leaving. A typical charging cycle for current prototypes is 4-5 hours – again, fine if you’re commuting, but impossible for a road trip. While technology is being developed to make charging your vehicle as quick as quick as filling up with gas, it has a ways to go before it’s ready, just like hydrogen fuel cells.

Fleets of electric cars will certainly be hitting the roads sooner hydrogen fuel cell cars, but which one ultimately ends up being the vehicle of choice for drivers remains to be seen as both have plenty of challenges to overcome before people will readily give up their cheap gas powered cars in favor of these alternatives.

Pipelines for Hydrogen Transportation

Pipelines represent the primary option for the most efficient transportation mode in a hydrogen energy environment. There are some issues for gaseous hydrogen delivery via pipelines:

1. High initial capital investment costs.

Although pipeline transmission offers technical and economic advantages as compared to other transportation methods, new pipeline construction imply high initial capital costs. Transporting gaseous hydrogen via existing natural gas pipelines can be a possible option to solve the costs, however more substantial modifications may be required for delivering hydrogen-natural gas mixture.

2. Material challenge.

The pipelines has always been troubled by hydrogen attack in the form Hydrogen Embrittlement (HE), Hydrogen Induced Cracking (HIC), Sulfide Stress Cracking (SSC), and Stress Corrosion Cracking (SCC) issues. Gaseous hydrogen via pipeline also need very high pressure levels (up to 3000 psi). The use of composites, fiber-reinforced polymer (FRP), for pipelines may be an alternative to resolve that issues. But, the challenges for adapting FRP pipeline technology still appear, such as:

- Evaluating the pipeline materials for hydrogen compatibility

- Developing a method for manufacturing large-diameter pipelines

- Developing a plastic liner with accpetably low hydrogen permeability

3. Hydrogen leakage and integrity monitoring sensors

Hydrogen is odorless, colorless, and tasteless and therefore undetectable by human senses. Because of that, hydrogen pipelines requires sensors for detecting hydrogen leaks and monitoring pipeline integrity. There are several sensor technologies currently available for monitoring mechanical integrity of pipelines. To apply those sensor technologies for hydrogen pipelines, some issues need to resolved, such as: characteristics of leak signal from light atomic weight of hydrogen gas, special distance resolution along the pipeline, response time, and the accuracy of alert calls.

4. Hydrogen compression

Compression is an integral aspect of gaseous hydrogen delivery via pipelines. Utilizing natural gas compression technologies for hydrogen is unreliable because (a) the hydrogen molecule is much smaller and ligher than natural gas (b) gaseous hydrogen contains only one-third he energy of natural gas. For example: this requires up to 60 stages of centrifugal compression of hydrogen as compared with four to five stages for natural gas.

Solar-Hydrogen Production Efficiency

When determining how much electricity is needed to produce H2 by solar energy, the energy requirements of generation (electrolysis), compression, liquefaction, storage, and transportation all have to be considered and added up. The energy content of 1 kg of H2 is 39.3 kWh. In order to generate 1 kg of H2 by the electrolysis of water, about 50 kWh of electric energy is required. Therefore, the efficiency of H2 generation is about 66%.

Once a kilogram of H2 is produced, it is either compressed or liquefied before storage or distribution. If handled in the high-pressure gas form, about 3 kWh of energy is required for its compression and 2.5 kWh is required for its transportation over each 100 km distance. Therefore, a total of about 6 kWh is required to compress and transport the gas over a distance of 100 km.

This energy corresponds to about 15% of the higher heating value (HHV) of the gas. As the transportation distance increases, this percentage also rises. Therefore, when transportation over long distances is required, it is more economical to transport the H2 in liquid form by trucks, rails, or ships. If handled as a cryogenic liquid, about 12 kWh is required to liquefy each kilogram of H2 and about 1 kWh is needed to store and transport it, for a total of about 13 kWh, which is about 33% of the HHV of the liquid.