|
|
| ECO-RTG drive system minimizes energy consumption at container terminals | | Twice as efficient | Due to rising oil prices and environmental considerations, it is more important than ever for the shipping industry and ports to reduce their operating costs and emissions. As container terminals consume a huge amount of energy, the saving potentials here are also particularly high. Working together, Siemens and APM Terminals have developed a revolutionary, extremely energy-efficient RTG (Rubber Tired Gantry) drive system. To date, this ECO-RTG system has provided APM Terminals with energy savings of 50 % compared to crane systems in use to date.
The ECO-RTG is based on a rugged drive system for hybrid buses which has made Siemens the leading supplier in this sector. The small converter units can be installed directly in the engine compartment, saving a great deal of space. A large plant room is therefore not required when installing the system on an RTG crane.
The drive system stores energy which is generated during the lowering and braking of the freight and released again during raising and acceleration. The efficient design makes it possible for a large proportion of the energy stored to be utilized.
A DUO converter unit powers the DC busbar. A microprocessor (DICO control unit) designed for the application and connected via a CAN bus calculates the energy requirement and controls the engine revolutions accordingly. This guarantees an intelligent supply of energy, enabling the engine to work very efficiently.
The DUO unit comprises two different converters which can be used either as rectifiers or inverters. Also included are one or two phases / phase conductors for the connection of a brake resistor (if no energy store is available). The units are extremely rugged in design. As they are also designed to operate in a hot and dusty environment, they can be mounted in close proximity to the diesel engine in the engine compartment.
Key to this technology is the use of a variable speed diesel generator. This flexible solution allows the energy requirement of the drive system to be tuned precisely to the output of the diesel generator. The result is a significant increase in efficiency.
Outstanding results in practical test
APM Terminals in Algeciras, Spain, offered to refurbish one of its RTGs accordingly. In a benchmark test for container operation, 30 sequences were simulated in an operating time of one hour and 45 minutes. The crane moved as in normal operation, handling different sizes of container. The conventional RTG crane consumed 16.1 liters of fuel per hour while the prototype of the ECO-RTG crane used only 8.1 liters per hour, i.e. half that of the conventional crane.
On the basis of these results, APM Terminals decided to order 20 RTG cranes fitted with the ECO-RTG drive system from the Zhenua Port Machinery Company (ZPMC) in Shanghai. The first ten cranes came into operation at the end of 2006. Their markedly lower fuel consumption was evident as early as February of 2007, with an average consumption of 9.2 liters per hour. This means that, taken together, the CO2 output of all 20 cranes will be an estimated 4,100 tons of CO2 less per year - this is equivalent to the annual CO2 output of 1,200 cars. Other benefits of the new system are a considerably lower maintenance requirement and, owing to the significantly reduced diesel consumption, fewer refueling stops.
Convincing benefits in the cost assessment
One of the most important decision-making criteria for determining which RTG setup to purchase is the Total Cost of Ownership (TCO), i.e. the overall costs of an investment incurred over its entire lifecycle. The initial purchase price is, of course, an important variable in the calculation of the TCO. However, variable operating costs such as the actual diesel consumption also play a large part. The ECO-RTG hybrid drive system is specially designed for fast growing, flexible and innovative container terminal operators, which are confronted with rising fuel prices.
The amortization period for the additional costs of an ECO-RTG crane compared with a conventional RTG crane is less than four years - and that is more than convincing with an RTG service life of 20 years. So it is hardly surprising that, in 2005 and 2006, several container terminal operators, in Morocco, China and India for example, decided to order RTG cranes with the ECO-RTG drive system.
Ideas 3 / 2007 | |
|
|
|
