Alan McDonnell, president of US-based Non-Synchronous Energy Electronics, LLC (NSEE) is trying to convince operators that by adopting variable-speed generators they can cut fuel consumption by at least 45%, while at the same time significantly reduce emissions.  
“The current situation is similar to that prior to the changeover to AC motors on cranes. It took a lot of convincing before operators began to specify AC motors, rather than DC motors, despite the fact that they offered a whole raft of benefits. Today, the fight is to get container terminals to buy into the variable-speed generator concept and abandon the more wasteful use of fixed-speed generators,” says Mr McDonnell. 
His company claims that it would take two years or less to make a return on investment, if existing RTGs operating for around 5,000 hours per year are retro-fitted. Indeed, experience suggests that by going slightly further, and fitting a smaller engine to most RTGs and adding some limited energy storage capacity, fuel savings could reach a staggering 65%.  
“The technology works. It can be retro-fitted to any RTG currently in operation and the savings that would be derived are wholly real. The problem is that most terminals and equipment suppliers we have spoken to so far are unwilling to share the cost of funding an initial long term trial. In fact, it appears that many container terminals are currently making so much money that they are simply not that interested in trying to cut their fuel costs,” claims Mr McDonnell.  
He bases a lot of his calculations around diesel costing in the region of $3.00 per gallon or around $0.90 per litre, which is currently the case in the US. Rates in other parts of the world are often higher, as would be the case across Europe, so savings could be even more interesting.  
The technological fix NSEE is suggesting is relatively simple. Most RTG engines are sized for the peak power required during heavy lifting, in which they are usually engaged for less than 2% of the time. Normally, they work at high speed using low power, which is the least efficient state in which they should be operated. By putting in power electronics, it is possible to keep the engine idling when no lift is being undertaken, thereby massively cutting back on emissions. However, the key to smooth operation is being able to bring the engine back up to speed just prior to the RTG engaging lift mode.    
While Alan McDonnell is seeking to retrofit RTGs with variable speed generators, several manufacturers are now offering this solution in new builds.  
However, Jorma Merimaa, RTG chief electrical engineer at Konecranes does not believe that all future RTGs will be equipped with variable speed generators. This is because alternatives, such as the cable reel RTG, are also gaining favour.  
“Fuel saving systems are more expensive and therefore not favoured by all of our customers, even though the majority do want to go down this road. This is because the higher the oil price, the shorter the payback time. Indeed, while initial investment costs are higher, the product can pay for itself within a couple of years because of the big savings in fuel costs,” he says.  
Konecranes has developed its own proprietary energy saving system, the first of which was installed last autumn. Many other customers have subsequently also signed up to the concept.  
Marko Rasinen, Kalmar's RTG sales office manager, says that fitting RTGs with variable speed generators is one way to save fuel costs and reduce pollution. However, the company's Zero Emission RTG, which works off of mains power, reduces operational costs even more and cuts exhaust pollution to zero. This solution also results in much lower operational noise levels.  
“Variable speed generators nevertheless provide good payback and customers are very interested in the technology. Kalmar is currently working on projects which will incorporate this solution,” he says.