Saft has been awarded a contract by MJ EcoPower Hybrid Systems to supply lithium-ion batteries for four new hybrid-powered mobile RTG (Rubber Tired Gantry) cranes serving Houston Harbor in Texas. Saft called the contract an important breakthrough in the US hybrid RTG crane market, which is set for growth as operators seek to drive down their fuel costs while reducing emissions. There are up to 600 existing RTG cranes in US harbors that could potentially be retrofitted with hybrid power systems, while around 150 new cranes are built every year for the global market.
RTGs play an important logistics role in ports and harbors, where they are used to transport and stack shipping containers during ship loading and unloading. Normally, the electric motors for the movement and hoisting functions are powered by a diesel generator often kept idling 24/7 to ensure that the crane is always ready for operation.
MJ EcoPower Hybrid Systems has developed an innovative alternative approach for its EcoCrane systems that replaces the conventional diesel power plant (typically rated at 400 to 750 kW) with a much smaller diesel generator set of 100 to 150 kW combined with a battery-based energy storage unit.
In previous installations at ports and railyards, EcoCrane systems based on lead-acid batteries have demonstrated dramatic fuel savings of up to 70% as well as reducing emissions from 87 to 98% depending on the emissions category. Regular battery-only running also makes the crane operations much quieter, improving working conditions for operators and reducing noise impact on the local environment, as well as improving the machine responsiveness.
For the Houston cranes, MJ EcoPower Hybrid Systems is replacing the lead-acid batteries with Saft Li-ion batteries to supply the normal operating power as well as providing regenerative storage for energy captured as the crane hoist lowers containers. The small diesel generator will only need to be started to recharge the batteries when required—it will be turned off for around 50% of the shift.
Saft is supplying a fully integrated energy storage solution including battery management systems.