Reducing Dredgers Fuel Consumption

Dredging companies are eager to reduce fuel costs to lower their operational costs, while industry regulations on exhaust gas emissions are becoming increasingly strict.

In the latest edition of IHC Insight, Erik van der Blom and Leonard den Boer of IHC Holland’s R&D department explain why it’s important to consider fuel consumption at the design stage of a vessel and outline the progress made in the project.

IHC is constantly improving the efficiency of its dredging vessel designs and aiming for a lower cost of ownership for its customers. This can be measured as a cost price per dredged cubic meter of soil. An important part of the cost price per cubic meter is fuel expenses. These account for approximately 20-30% of the operation costs of a trailing suction hopper dredger.

This explains why any parties interested in buying new vessels are constantly looking at fuel consumption, without wanting to make a significant increase in investment.

As well as a major cost driver, fuel consumption is topical because of the current trend of sustainability within the dredging industry. At the same time, regulation and legislation are becoming more stringent: in the USA, the EPA Tier 4 emission regulations are becoming effective, requesting another major step in the reduction of emissions, especially for NOX. Worldwide the IMO is preparing the Energy Efficiency Design Index (EEDI), defining steps in the reduction of C02 emissions.

“In the Netherlands, for example, the Ministry for Infrastructure and Environment (Rijkswaterstaat) is encouraging C02 reduction in dredging projects with the C02 performance ladder (prestatieladder),” said Erik.

As fuel consumption is the major contributor to the environmental impact of dredging equipment, it should therefore be a starting point in the design of dredging vessels. This is why the R&D department at IHC Holland has been investigating the impact of vessel design on fuel savings.

“Every dredging customer is looking to reduce fuel costs because of its impact on operational costs,” said Leonard. “And almost every company is looking at fuel-saving possibilities. We are looking at possibilities specifically for dredging vessels, with specific designs and operational profiles.”

Measurements of operational profiles

To understand the fuel consumption of a dredging vessel, its operational profile during the dredge cycle is essential as a starting point. For example, dredging gravel at a depth of 50m is completely different to sucking up mud in a small harbor and discharging it just outside the jetties.

Water depths, soil to be dredged, sailing speed limitations and the amount of manoeuvring required – all have an effect on the operational profile influencing the fuel consumption per cubic meter.

To get an insight into the operational power consumption of dredgers, IHC took measurements from different vessels on various dredging activities. These included harbor maintenance and land reclamation, and the findings were that the average power consumption was significantly lower than assumed.

“To collect the data, we took measurements on vessels working in the field. It was a real eye-opener to discover that for much of the time, the vessels were operating at partial power – more than we thought,” said Leonard. “The partial power conditions present a great opportunity for fuel saving.”

These insights can be translated into the effects on the dredgers’ systems and the fuel consumption, using knowledge of mechanical and electrical engineering, hydrodynamics and soil mechanics. Once all the parameters and relations have been established, the design variables that play a significant role in the overall fuel consumption of a dredger can be identified.

IHC Insight