Written By: Brad Templeton
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Recently the French originated demonstration boat the Energy Observer stopped for a visit to San Francisco, on its way around the world, having come from the Galapagos and on its way to Hawai`i. The boat uses solar power, hydrogen and battery energy storage and a small amount of high-tech wind.
On board are 200 square meters of solar panels, 1500kg of batteries, tanks for 63kg of hydrogen (good for 1MWH of electricity and another 1MWH of heat) along with electric motors, solid computer-controlled “ocean wing” sails and a desalinator and hydrogen generator to refuel the hydrogen tanks. It travels only 5mph without wind, though can do more — and even regenerate electricity — when the winds get strong enough.
Using renewable wind power to move ships is of course a very ancient technique, and it’s well understood and efficient. Sailing ships have issues when becalmed, and in sailing in narrow channels, but otherwise it’s not clear this ship is a better idea than a sailboat with a small motor system. It is more to demonstrate and play with technologies, and the operators are reluctant to give concrete numbers on costs. That’s unfortunate because any story about energy is vastly reduced in meaning without examination of the economics — even if it’s the future promised economics rather than today’s. Indeed, inattention to economics has led to some really stupid renewable energy projects and even some very stupid laws. Nonetheless, the ship is a cool project, even if it doesn’t deliver information as meaningful as it should.
Hydrogen is a controversial energy storage fuel. It’s not an energy source, but rather a competitor for things like lithium batteries. Many had high hopes for it in cars, but for now it has lost the battle to batteries. Toyota sells the Mirai hydrogen vehicle in very small numbers, but with only a few filling stations available, and the hydrogen coming from fossil fuels, it’s not clear why anybody buys one. Hydrogen’s advantages such as weight and refuel time (when there aren’t any stations) aren’t very powerful in a car compared to its disadvantages — higher cost for fuel and fuel cells, offering less than 50% efficiency, having no refueling infrastructure, non-green sourcing, bulky tanks and much more. Some of those can be fixed, but others are difficult.
This has left us to investigate hydrogen in other areas — large vehicles like trucks and buses, aircraft (where weight is hugely important) and now, ships. There is also research on grid storage, though the low efficiency of conversion is a sticking point. The greatest promise is in aircraft. Hydrogen is actually the best fuel around in terms of energy per kg, but at present storing a kg of hydrogen requires 5 to 12kg of tank, which eliminates a lot of that — but even at that poor ratio it still wins in aircraft.
In a ship, the Energy Observer crew believe that batteries would weigh more than 10 tons. While they don’t say the weight of their H2 system, it probably is more in the range of a ton. Weight is not quite as crucial for ships but that much extra weight comes at a cost. In addition, the EO reduces the waste of fuel cells by making use of the excess heat to provide heat on the ship. Normally the total cycle of hydrogen as storage is less than 50% efficient, which is not good when batteries can deliver 90% or more. Heat though, is certainly needed for a passenger vessel at sea. A cargo vessel might not need so much.
The ship uses up the H2 in operation when there is no wind. The H2 recharges the batteries and provides heat, then the batteries run all systems. With enough wind, the solar panels can instead recharge the batteries and make new H2 using desalinated water and electrolysis. Their goal is to not use any net H2 on a typical day, but if winds and sun are poor, they will use it up, but plan their missions to leave with enough H2 to handle such situations. While docked, the panels and shore power build up the H2, or in theory, they might some day find H2 refilling at a “hydrogen marina.” When they left for Hawai`i from San Francisco, they only filled the H2 tank partially because they did not need it all the way full.
The ship used to be a racing catamaran, but instead of sails it has two “ocean wing” fixed-shape sails. These solid wings can generate as much thrust as cloth sails twice their size. They are small, to not block the sun, but they are also computer controlled, allowing them to be used without much crew effort or requiring any skill. When the wind is really strong, the propellers and motors can spin in reverse to generate electricity to build up more H2. Full sized sails would do better though, and could be put up at night with no risk of blocking the sun. They seem to have shied away from traditional sail and wind power in spite of their well established value. Before they had the ocean wings, they tried installing wind turbines, which failed for obvious reasons.
Life on board is spartan. The catamaran’s cabin is small for a crew of 8. Also on board is a small science sub-crew taking the opportunity to study the oceans and wildlife on such an unusual voyage.
A ship has the space for H2 tanks and the ability to generate it, so this can make sense. I don’t think a future vessel would look like the Energy Observer, but hybrids of electric drive and traditional sail, adding what solar power can be had make sense. Every inch of the deck is solar panels, and there are even panels to get the sunlight reflecting off the water. As panels get cheap this makes sense, though you don’t want to forgo useful sails because of the shade they will cast if the wind will give you more than the sun.
It’s possible to foresee solar/wind/electric recreational boats. Operating recreational boats is highly polluting and expensive. Sailboats are clean and cheap but a lot of work and under many limitations. A hybrid, using electric power, could be an answer there, as well as an answer for the big cargo ships.
What next for Hydrogen?
Hydrogen may not power cars, but it has some chance at other vehicles that want to avoid burning fossil fuel:
- Aircraft care immensely about weight. Batteries today can give only modest range to electric aircraft. It’s either H2 or synthetic/biofuel hybrid power trains there.
- One special type of aircraft is quite interesting, the airship. While people have been scared of H2 there since the Hindenberg, it’s important to realize that H2 can be more than a lift gas, it can be the power fuel. It’s the only fuel that has negative weight, and you don’t need to pressurize it with big heavy tanks in an airship.
- Trucks are looking at H2 because the battery weight for a truck takes up a large part of their 40 ton limit, and trucks have a harder time stopping for long enough to charge it. The 50% energy loss is trouble, but the weight limit is a legal requirement.
- Grid storage with over 50% loss is a serious problem. But with H2, if you want more capacity, you just need more tanks. Doubling the tanks doesn’t double the cost, but doubling batteries does double the cost.
Other types of energy storage are not standing still, though. There are experiments with newer batteries, flywheels, aluminum, synthetic hydrocarbon fuels and more underway. It’s a space ripe for change.