Death to the Iron Genny

I have seen the future and it looks pretty darn good. I was at the Miami Boat Show this past weekend and saw lots of cool stuff, but my favorite by far was from Solomon Technologies. I’d heard and read about their stuff before, but this was the first time I’d seen it installed in a boat and got to talk with company representatives.

What is it? Simply put, it is a system that replaces a sailboat’s diesel engine(s) with electric motors, but it is really much more than that because the change impacts the boat’s entire electrical system.

What are the benefits?
• More efficient use of fossil fuels
• Simplified maintenance
• Extended cruising range
• Increased reliability
• Improved onboard power availability

Obviously, the electric motors need DC power so there is a pretty significant battery bank to drive them. The standard installation requires 12 4D batteries to produce 144V. At 135 lbs apiece, this is 1,620 lbs of batteries! The 144V bank is in addition to the existing 12V house bank.

Batteries need to be charged and this can be done in a variety of ways depending on the power needs and usage characteristics of the boat. When the boat is plugged in at the dock, the fastest and most efficient method has always been and remains to be plugging into shore power and using an AC battery charger.

The beauty is in the variety of ways the batteries can be charged away from the dock, the primary means of which is by “regenerative sailing”. Ordinarily, a propeller shaft has to be locked when the boat is sailing and the engine is off. Otherwise, it will turn the crankshaft which is bad for the engine. Locking the propeller has roughly the same effect as dragging a bucket in the water. To combat this, performance sensitive boats use feathering props that fold up when dragged through the water and open again when the engine spins the shaft. However, with an electric motor the freewheeling of a sailboat propeller can be turned back into electricity to charge the batteries and have a minimal impact on sailing performance. This is a similar principle to using the braking action of a hybrid automobile to recharge the batteries.

When not sailing, the typical sailboat battery charging techniques apply, such as solar, wind, and diesel generators. These may or may not be necessary as situations and usage patterns dictate.

So why is this so much better? Diesel engines are a pain in the butt to maintain. They are complicated contraptions and can be rather difficult to keep in good working order. They have a lot of moving parts what with the necessary water/fuel/oil pumps and filters, alternators, transmissions, and belts to hold it all together. And those are all parts that need regular service. The engine needs its oil checked every few hours while underway and completely changed at regular intervals. An electric motor has none of those things and since it can easily spin up to 15,000 RPMs, there isn’t even a transmission.

Diesels create heat and noise which makes living with them very annoying. And since they are large, need to be readily accessible for maintenance, and must go on the centerline of the boat they usually either take very prominent positions on the boat or are very difficult to work on. An electric motor is nearly silent, is much smaller, and does not need to be as accessible for maintenance.

A diesel engine transfers fuel to thrust very inefficiently. By the time it powers all the needed pumps, alternator, and transmission, a 30 HP diesel may only deliver 16 HP to the propeller, losing 47% along the way. An electric motor on the other hand has much less to overcome and can deliver 90% of its rated horsepower to the prop. This means that a diesel can be replaced by not only a smaller motor, but a weaker one too.

Most applications will still include a generator to charge the batteries, but a generator is a much smaller and simpler device than a diesel engine. Usually they are contained in their own sound-insulated boxes with fuel and air going in, and exhaust and electricity coming out. Because the generator’s one task is to charge the batteries it can be tuned to do this as efficiently as possible. While twin diesels will consume 2.5 gallons/hour for motoring, the efficient generator should only consume 0.8 gallons/hour to keep the batteries charged.

With the availability of a high-voltage battery bank and the recent improvements in inverter technology, it is now much more feasible to run high voltage appliances away from the dock. It used to be that you either had to be plugged in or have the generator running to have air conditioning. Now the air conditioner can be run through the inverter and the generator will only kick on when needed to bring the batteries back up to charge.

I struck up a conversation with the guy minding the boat with the Solomon rig installed, assuming him to be a sales rep for the boat builder. I started with “I know I should probably ask the Solomon guys, but…” and then proceeded to ask something about maintenance. I was surprised at how well he could answer the question. He was obviously well-versed and excited about the technology.

Several minutes into the conversation he mentioned that he lived aboard a Lagoon 47 with a Solomon setup. This struck me as odd that a sales rep would live on a million dollar catamaran, and must have looked at him stupid because he then explained that he was the inventor of the technology and founder of the company. Sure enough, it was right on his nametag that I hadn’t bothered to look at. He lives on his boat in Tarpon Springs, about 15 miles north of my house.

He said that he had his boat’s fuel tanks reduced to make room for the batteries, had the engines removed to make room for the motors, and only added a net 200 lbs to the boat. The boat stays mostly at anchor and does not generate much power through sailing, but instead relies mostly on solar and the generator. Even with reduced tanks he says that he can generate enough electricity to stay on the hook for 6 months. He gives no regard for power consumption and runs the air conditioner as much as he wants.

So if he can sit for 6 months without refueling, it stands to reason that a boat can go a heck of a lot longer when sailing.

Of course it isn’t all peaches and light. The install is likely to cost upwards of $40K and batteries don’t last forever. Since 4Ds cost about $400 apiece you should budget about $1,000 per year for new batteries. But given the fuel costs, maintenance hassle, reliability, and eventual engine rebuild/replacement it may very well be worthwhile to switch. Hopefully prices will come down, the government will offer some clean energy incentives, and these things will become standard equipment.