The estimate was calculated by mathematical models that manage the operation of diesel generators and batteries; the system was validated on real vessels.
Researchers from the Research Centre for Greenhouse Gas Innovation (RCGI), at the University of São Paulo (USP), demonstrated that diesel-electric platform support vessels (PSVs) could reduce pollutant emissions by more than 15%. The team developed mathematical models that simulate the vessels’ powertrain operation and emissions. The model also optimized the onboard diesel generators in order to improve fuel efficiency and manage the lithium-ion batteries.
PSVs are widely used vessels in the oil and gas industry that transport supplies from ports to platforms. In the diesel-electric models, a set of diesel generators produce the electrical energy necessary to propel the ship.
Using data obtained from a real vessel, two mathematical models of a diesel-electric PSV powertrain were developed. One used HOMER PRO software to estimate the entire course of the voyage, and the other used MATLAB software to monitor and manage the powertrain without any previous information about future conditions and maneuvers. The results of the simulations were validated with data from a real travels — a distinctive feature of the study, which was published in the journal Applied Energy.
“The generator models decide when to activate, decrease or increase power according to the travelling conditions. The models for the batteries turn them on or off based on these factors and the charge level. We also analyzed what battery size should be installed for best results, since each vessel requires a specific size”, explains Bruno Souza Carmo, professor at the Department of Mechanical Engineering at USP’s Polytechnic School, director of the RCGI Decarbonization Program and coordinator of the research.
A partnership with a company in the maritime industry that shared five months of telemetry data – a tool that collects vessels’ real-time data, such as the levels of gas emissions into the atmosphere – provided the preliminary data from the vessels and allowed the validation of the generator models.
Significant reduction in emissions – “In the study, we found that the emissions measured in the field were the same our models calculated, which validated the generator algorithm. The battery models were validated based on literature data, since this equipment, which is new to the market, were not used in the vessels we monitored”, says the project coordinator. “Just by optimizing the generators, we were able to reduce emissions by 10%. By adding batteries to the models, we were able to reduce emissions by another 5%,” he adds.
These figures were calculated summing up the volume reduction of three pollutants emitted by the vessels. Carbon dioxide (CO2) had the most significant reduction. Its levels decreased by between 16% and 26%, depending on the generator load and the configuration applied, since several trips were analyzed. Emissions of particulate matter, which is a mixture of several solid or liquid pollutants released into the atmosphere, also reduced significantly from 25% to 65%.
However, nitrogen oxides (NOx) emissions increased by up to 20% in some tests, despite a reduction of up to 6% in others. “This happened because we increased the combustion temperature to optimize generators energy efficiency, which increases the output of nitrogen oxides. However, it is possible to correct this problem with catalytic converters — a solution already used in the automotive industry, which has the same issue,” explains Carmo.
Urgent change – According to the research coordinator at RCGI, the technologies developed by his group for the maritime industry are viable because they do not require large investments. “Some companies sell unexpensive systems and batteries that are prepared for this adaptation. However, the biggest cost results from the interruption of the ship’s operation, which is required to adapt the vessel and perform safety tests. This is not common practice in an industry that has operated the same ships, with virtually no changes, for many years.”