A new system is promised to deliver optimised management of multiple engines and considerable potential savings as a result
At the Europort exhibition in Rotterdam, Caterpillar Marine displayed its new Multi-Engine Optimizer (MEO) tool for the first time. MEO is loaded with optimised test data that is then used to operate a vessel’s various engines in conjunction to achieve the optimal performance.
MEO leverages proprietary performance data and patented control algorithms to provide intelligence for power-management systems. MEO works by advising power-management systems on which engines to operate, and enables the use of dynamic asymmetric loads to drive the combination of engines and loads to create the lowest possible fuel consumption.
Speaking to Marine Propulsion, Caterpillar Marine product manager Dra Wiersema said: “MEO allows users to use variable-speed and constant-speed generators on a single bus. This means that they can leverage the low-load advantages of variable speed with the high-load advantages of constant speed.”
The MEO’s simulation tool then allows users to view the fuel consumption of any combination of power sources. By using the estimate of a vessel’s load profile, it becomes possible to construct the engineroom that best meets the end user’s requirements.
“The most common question about MEO is, 'How much can MEO save?' While our response will not be initially satisfying, the truthful answer is, 'It depends,'” said Mr Wiersema.
The system has been tested on a number of vessels and has seen fuel economy savings of between 5% and more than 15%. Mr Wiersema explained that the results achieved very much depend on engineroom configuration and vessel load profile.
MEO is designed for multi-engine installations that have multiple load factors. Obviously a single engine installation has no opportunity for MEO, but even a multiple engine installation that spends most of its operating hours in the 75-90% load range will also not provide an opportunity for MEO.
Furthermore, if on a four similarly-sized engine installation there are only four load steps of 20%, 40%, 60% and 80%, then a basic power-management system can be utilised to trigger single-engine operation at 20%, two-engine operation at 40%, and so on. At each of the four load points, that combination of engines will be operating at peak efficiency with no room for MEO-driven improvements.
Caterpillar, though, believes MEO will not lack for opportunity because there are enough vessels that work with significantly differentiated load characteristics. Further, just because a vessel's load characteristics seem simple, it does not mean the crew will operate in the best interests of fuel efficiency. This is where MEO can deliver results.
Operating in a North Sea environment one OSV achieved 7% over a 23-week period with weekly savings ranging from 2-14%, depending on the vessel loads. High-percentage savings are not synonymous with high load. Whether MEO can provide savings is dependent on the engine options, the capability of the existing power-management device, the load, the willingness of the crew to use MEO and the duration of the load changes. Mr Wiersema explained: “Sometimes a mid-range load point under operational constraints is a good MEO situation, and in other vessels it might be a bad MEO situation. Again, it depends.”
In terms of the vessels that can benefit from the system, Mr Wiersema is clear. “It is likely your vessel will benefit from MEO if you have a vessel with multiple engines and a load profile that spends less than 60% of its time within any 15% band of the vessel's maximum power."
The 700 mm-wide MEO cabinet can be installed in an engineroom or control room, and requires no more than six wire connections.
“MEO is viewed by marine societies as an advisory system, and will have type-approval certification. As an advisory system, MEO can be turned off at any time, allowing the existing power-management device to return to its normal operating procedures to provide an extra layer of protection and safety,” said Mr Wiersema.
By mixing and matching engines and independent load points, MEO allows engines to provide power at their most efficient point. Compared with the common scenario of engines operating at an equally shared load, MEO creates an unlimited combination of virtual enginerooms to match each particular vessel load.
The performance maps and control algorithms give MEO the ability to manage different types of engines and power sources on the same bus. Customers can now choose combinations of Cat and MaK engines that best match the customer load profile (e.g. a set of high-speed engines for low-load situations that provide additional power to the set of medium-speed engines during high-load situations).
Mr Wiersema said one of the key factors in MEO’s favour is that its effects can easily be measured. “Simply put, MEO measures fuel and MEO can be turned off. You cannot turn off a hull coating, you cannot turn off your drive motors, you cannot turn off your propeller design, but you can turn MEO off and see the consequences," he said.
MEO’s capability to provide fuel savings increases significantly when the combination of different engine types is customised to the vessel load characteristics. By leveraging different sized engines, customers can limit engine wear due to low-load operation, reduce fuel consumption and improve emissions by having engine combinations that allow engines to operate in their peak efficiency zones at multiple vessel load points.
Depending on the degree of difference between engines, many power-management systems are not able to maintain a stable bus in an environment of load variability. The different ability of each engine to respond to a load can cause a breaker to trip due to voltage fluctuations. MEO fuel maps and control algorithms prevent excessive voltage fluctuations, enabling the customisation of vessel engineroom configurations.
This ability extends to include the combination of constant-speed generator sets with variable-speed generator sets. Since as a general rule constant-speed power is most efficient above 50% load and variable-speed power is most efficient below 50% load, the combination of larger constant-speed gensets with smaller variable-speed gensets has the potential to be one of the most efficient power packages possible, even when accounting for the power conversion losses of the power electronics.
Mr Wiersema concluded: “MEO does not help manage how load is delivered to the engines from the power consumers, but from the power-management perspective we believe it is to the benefit of our customers to say that with access to the proprietary fuel, emission and response maps, a broad MEO-adaptable product line and the use of the patented control algorithms, it will be difficult to beat the efficiency of MEO. Under certain circumstances some systems may get close, but if MEO is functioning properly it simply cannot be beaten."