With the growing interest in renewable energy and new ways to store energy, fuel cells seem like an interesting option. However, having been on the fringes of three well-funded marine fuel cell projects that never made it to commercial viability, I know only too well the challenges to optimizing fuel cell installations in boats.
Hydrogen Storage Challenges
The most common type of fuel cell used on boats is known as a ‘proton exchange membrane’ (PEM) fuel cell. There is another technology which is potentially viable, known as a ‘solid oxide’ fuel cell (SOFC). Both require hydrogen as a fuel source. Here we run into the first problem. To store a decent amount of hydrogen in a cylinder you need extraordinarily high pressures – as high as 10,000 lbs per square inch – which requires custom-built high-pressure cylinders. These are typically expensive, heavy, and still store nowhere near the energy content of a tank of diesel or gasoline.
Then we need the hydrogen. There is no infrastructure for delivering hydrogen to a boat and as a result it must be produced through some onboard process. The three projects with which I am familiar variously tried to extract the hydrogen component from diesel fuel, the hydrogen component from propane, and the hydrogen component from seawater.
Creating Hydrogen on a Boat
Let’s look at the last first. The two components of water are hydrogen and oxygen. Through a process known as electrolysis they can be cracked apart and the hydrogen extracted. Electrolysis requires electricity. In the boat context this comes from solar power. So, we take electricity generated by solar panels to extract hydrogen from seawater to power a fuel cell to make… electricity! The electricity ‘in’ is at least twice as much as the electricity ‘out’! It’s not hard to see why this project failed. What is remarkable is millions were invested in it!!
What about cracking hydrocarbons (diesel, propane, or some other hydrocarbon) to extract the hydrogen content? The project that aimed to crack diesel to obtain the hydrogen was abandoned due to trace impurities in the diesel fuel that affected the fuel cell performance, and the one that used propane as the fuel source was abandoned due to impurities in the propane fuel. Between them I believe they spent something on the order of one hundred million U.S. dollars.
A Working Fuel Cell
There is a popular fuel cell used in boats and RVs, sold by EFOY, that uses methanol as the hydrogen source. Tens of thousands have been sold. However, these units have a high cost per kilowatt-hour of electricity produced. Over the life of the fuel cell, including the cost of fuel and potential reconditioning or replacement of the fuel cell itself, the cost of electricity can be up to 100 times higher than buying electricity from the grid, and 10 times higher than using an onboard generator or alternator.
One of the reasons for the high cost of electricity created is because the conversion ratio of methanol into electricity is low. Only about one-third the electricity is produced per liter of fuel consumed as compared to a well-optimized AC generator or an alternator on the main engine of a boat when underway. Surprisingly, this means that using fuel cells on boats may not be environmentally efficient when compared to using diesel or gasoline to generate the electricity.
There is a qualifier here. It is possible to create ‘green’ or ‘net zero’ methanol which, theoretically, produces no greenhouse gases through its production and use. However, we will soon see traditional diesel engines that can also run on the same methanol with more efficient electrical energy production than the fuel cells. Some of these engines already run on 100% hydrogenated vegetable oil (HVO) which is also nominally a ‘net zero’ fuel.
Conclusion
Fuel cells may seem like an attractive option for generating clean energy on boats, but there are significant challenges that still need to be overcome before they become a viable and cost-effective solution. These challenges include the lack of hydrogen supply on shore and no storage capabilities on boats, safety concerns associated with high-pressure storage of hydrogen, low conversion efficiency of hydrocarbons into electricity, and impurities in alternative fuel sources.
Despite the potential benefits of fuel cells, the current technology and infrastructure are not yet mature enough for widespread use. As a result, other methods of generating electricity, such as diesel generators or alternators, may still be more efficient, cost-effective, and environmentally friendly options for boaters, especially if run on the emerging ‘alternative’ fuels.
If you want to learn, how to power your boat from alternative energy sources, you should talk a look at the module on this topic which is included in our Boat Electrics 101 course!
