The best way of propelling any vehicle, on land or water, is using electricity. Electric motors are very efficient wasting very little energy as heat and they produce no emissions. In addition, an electric motor uses no energy while the vehicle is stationary whereas an internal combustion engine uses fuel just ticking over. Electric motors are smooth and quiet whereas internal combustion engines are noisy, smelly and vibratory. The electricity an electric motor uses can be generated using environmentally friendly methods such as wind or solar power.
Storing That Energy
So why aren’t all boats electrically powered? The answer is that you need to store the energy used on a boat, both for propulsion and for domestic use. For the two forms of propulsion discussed above, the two corresponding ways of storing energy are.
Diesel. This stores a lot of energy in a small space – a simple metal tank. A boat fuel tank can typically hold enough fuel for several weeks cruising. It can also be easily topped up from a local garage or marina.
Electricity. This must be stored in expensive, bulky batteries. Unfortunately a large battery pack is required for even a single days cruising. This is fine if your boat is always moored up every night where there is a shore supply but if you are cruising for any length of time, this would require a charging point at every mooring. This is currently a long way off.
Best of Both Worlds
An increasingly common compromise is to us hybrid technology. Here both electric and internal combustion engines are fitted. A moderate sized battery pack can be used giving a relatively short range because the diesel engine is always available for longer distances. However, the bottom line is that if you are travelling away form a shore supply, for any period, most if not all of your energy will be coming from diesel. So why bother?
Well, hybrid technology is already in use. Hybrid cars are quite common on the roads these days, for instance the Toyota Prius. The advantage here is that the internal combustion engine can be turned off when stationary or moving slowly to save fuel. For road use, high powers are only required for acceleration so a smaller engine can be used with the electric motor providing extra power when required for acceleration.
Hybrid on the Water
But what about marine applications of hybrid technology and more specifically inland waterways. Plenty of hybrid boat drives already exist – here’s a few of them.
BAE Systems “Hybridrive”. A serial system used for small commercial vessels and larger yachts.
Greenline Hybrid. A parallel system using same unit as generator and motor. It also features an array of solar panels on the roof.
Dse Hybrid – pictured. Seemingly now defunct, they claimed to be able to run on their solar panels. Perhaps possible in Florida but not in the North of England.
Hybrid-Marine. A parallel system aimed at UK inland waterways and sailing boats.
The Thames Electric Launch Company Ltd. Mostly famous for
Edwin Osborn . Not a commercial producer of hybrid boats but a guy who converted his own boat. I’ve included a link to his site because he has come to a lot of the same conclusions that I have.
OK so there are people using hybrid technology in boats but why? We still don’t have a compelling reason for using hybrid propulsion. In the next article, I shall look at the justification for using a hybrid technology and the different hybrid configurations available.