Patent Application
20200122983
This invention relates to a rubber-tired gantry crane (RTG) and, more particularly, relates to a battery-powered electric RTG (e-RTG) having an onboard charging system.
An RTG is a mobile gantry crane used in shipping terminals to stack and store shipping containers. Today, RTG's are commonly run on diesel-powered engine-generators that provide full operational power to the RTG. Such diesel-powered engine-generators are often sized as large as 500 horsepower or more and produce significant engine exhaust. RTGs operating in shipping terminals in California must meet strict emissions requirements set by the California Air Resources Board (CARB), including a mandate to decrease emission levels by the year 2030. Accordingly, decreasing RTG emissions is a critical objective for the improved design of RTGs. Hybrid and fully electric RTGs (e-RTGs) have been introduced that reduce or eliminate emissions.
A hybrid RTG is equipped with a propane or diesel engine-generator combined with a battery system which, together, power the motors of the RTG. With the addition of a battery system, the hybrid RTG can utilize a smaller engine-generator, about half the size of the more typical 500 HP propane or diesel engine-generators, thereby producing reduced emissions (e.g., a reduction of emissions by 50%). Additionally, a hybrid RTG can take advantage of energy recovery mechanisms, such as regenerative braking, to recharge the battery system when the RTG is performing braking or container-lowering actions, further improving energy efficiency. The engine-generator allows for rapid refueling of the hybrid RTG. Despite these improvements, hybrid RTGs still produce considerable emissions. As a result, efforts have turned to the development of fully electric e-RTGs that produce zero emissions.
Today's e-RTGs either connect directly to a power distribution infrastructure or are powered by a battery system. In an above-ground power bar system, an e-RTG connects directly to a power distribution infrastructure that includes a series of above-ground power bars supported on posts and distributed throughout the shipping terminal. In a cable reel carrier (CRC) system, an e-RTG is connected to a wheeled cable reel carrier, which carries a power cable that plugs directly into the e-RTG and connects the e-RTG to a, typically underground, power distribution infrastructure. The cable reel carrier moves in tandem with the e-RTG during operation. Both the above-ground power bar system and CRC system require considerable power distribution infrastructure to be constructed and maintained within the shipping terminal, either above ground or underground, and the associated power bars, posts and cabling introduce considerable safety hazards.
More recently, battery-powered e-RTGs have been introduced. Despite the advantages of portability, battery-powered e-RTGs suffer from several limitations that have challenged their mass-market acceptance. Battery-powered e-RTGs must be charged overnight after each day's operation and substantial work is required to install charging stations. In addition, due to the large size of each e-RTG, it is difficult to accommodate enough charging stations in the shipping terminal for the simultaneous overnight charging of multiple e-RTGs.
Thus, there remains a need for an RTG that produces less emissions than a hybrid RTG, while avoiding the need for an elaborate power distribution infrastructure or charging stations.
The present invention provides for a battery-powered e-RTG having an onboard charging system.
In one embodiment of the invention, an e-RTG includes an energy storage device, such as a rechargeable battery, disposed on and configured to provide power to the e-RTG and a charging device, such as a propane or diesel-powered engine-generator, disposed on the e-RTG and configured exclusively to charge the energy storage device.
In another embodiment of the invention, an e-RTG includes an energy storage device disposed on and configured to provide power to the e-RTG and two charging devices disposed on the e-RTG and configured exclusively to charge the energy storage device. The two charging devices include a primary charging device configured exclusively to charge the energy storage device when the e-RTG is in operation and a secondary charging device configured exclusively to charge the energy storage device when the e-RTG is idle or not in operation.
The battery-powered e-RTG according to the invention produces less emissions than a hybrid RTG, while avoiding the need for any power distribution infrastructure or charging stations.
Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:
Configurations of the Invention
A charging device (150), for example, in the form of a propane gas or diesel engine-generator, is mounted to or otherwise disposed on the RTG, for example in an onboard engine room located away from the truck lane (160) and any other hazards.
Unlike the engine-generator of a hybrid RTG, the onboard charging device (150) is configured exclusively to charge the energy storage device (120) and not to drive the motor or motors of the RTG. As a result, it can be much smaller than the typical engine-generator of a hybrid RTG. For example, a 50 horsepower or smaller propane or diesel engine-generator may be used for the charging device to provide enough power to the energy storage device to allow for the continuous operation of the e-RTG, free of interruptions. A 50-horsepower engine-generator would be about 10% the size of a 500 horsepower RTG diesel engine-generator, lowering emissions to just 10% of a conventional, fully diesel-engine powered RTG.
Being fully portable, the e-RTG of the invention requires no power distribution infrastructure. As a result, there is no need to alter the existing shipping terminal facilities, and significant costs and safety hazards can be avoided by eliminating the need for power bars, posts, cabling or any other dedicated power infrastructure.
In addition, with the e-RTG of the invention, there is no need to plug the e-RTG into a charging station after each day's operation, avoiding the need for any charging station infrastructure and the associated labor required to maintain and operate charging stations. For the e-RTG of the invention, the fuel tank of the engine-generator can be sized to be large enough, for example, for weekly or bi-weekly operation of the e-RTG without the need for refueling.
Like the hybrid RTG, the e-RTG of the invention can be rapidly refueled by simply refilling the engine-generator, for example, with propane gas or diesel delivered to the e-RTG by truck. Also like the hybrid RTG, the e-RTG of this invention can take advantage of energy recovery mechanisms, such as regenerative braking, to recharge the battery system when the e-RTG is performing braking or container-lowering actions, further improving energy efficiency. However, with the onboard charging device, i.e., engine-generator, configured exclusively to charge the energy storage device, it can be much smaller than in a comparable hybrid RTG, further reducing emissions.
In addition, as an alternative to a propane gas or diesel engine-generator, the e-RTG of the invention can utilize a hydrogen-powered engine generator for the onboard charging device. A hydrogen-powered e-RTG according to the invention would have the added benefit of producing zero noxious emissions.
Certain embodiments of a battery-powered e-RTG having an onboard charging system have thus been described and illustrated herein in detail. These embodiments are merely example implementations of the invention and are not to be taken as limiting, the spirit and scope of the invention being limited only by the terms of the appended claims and their legal equivalents.
This application claims the benefit of U.S. Provisional Application No. 62/748,330 filed Oct. 19, 2018, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62748330 | Oct 2018 | US |
