Environmental Technology

Efficiency gains to save fuel

Malcolm Latarche
Malcolm Latarche

09 November 2018

Efficiency gains to save fuel

There is an unfair depiction of the shipping industry as a profligate user of fuel causing unnecessary emissions and endangering health. In reality shipowners have always been careful about the amount of fuel used and except for meeting commercial commitments are usually keen to employ any means to reduce fuel use. In doing so they are indirectly contributing to reducing ships’ environmental impact.

Nevertheless, efficiency has become a marketing tool for equipment suppliers and the shipowners themselves with claims for greener operations being made at every opportunity.

Quite obviously the amount of emissions to air is directly related to the quantity of fuel used so any reduction in fuel use contributes to improving the environmental impact of ships. Many of the series of ShipInsight guides contain sections on energy saving measures with Power and Propulsion, Paints and Coatings and Shipping Software featuring the issue quite strongly. While there is no intent to duplicate that here, a brief resume of the issues is relevant.

In addition to individual items of equipment or ship systems, the design of the ship as a whole is of vital importance. In 2011, following some years of development, the IMO rules on energy efficient design came into effect. Known as the Energy Efficiency Design Index (EEDI), ships are obliged to meet a certain efficiency standard that becomes increasingly stricter over a period of time.

Since 1 January 2013, following an initial two-year phase zero, new ship design needs to meet the reference level for their ship type. The level is tightened incrementally every five years, and so the EEDI is expected to stimulate continued innovation and technical development of all the components influencing the fuel efficiency of a ship from its design phase. Following MEDPC 71 in July 2017, the IMO is considering bringing forward the final Phase 3 of EEDI from 2025 to 2022 and introducing a more stringent Phase 4 in addition.

At MEPC 73 in October 2018, there was no real consensus on the proposal although there was support for bringing the date forward for container vessels. However, the meeting decided to take no firm decision and the matter will be further considered at MEPC 74 in May 2019.

The EEDI is a non-prescriptive, performance-based mechanism that leaves the choice of technologies to use in a specific ship design to equipment makers, shipbuilders and shipowners. As long as the required energy efficiency level is attained, ship designers and builders are free to use the most cost-efficient solutions for the ship to comply with the regulations.

The EEDI provides a specific figure for an individual ship design, expressed in grams of carbon dioxide (CO2) per ship’s capacity-mile (the smaller the EEDI the more energy efficient ship design) and is calculated by a formula based on the technical design parameters for a given ship.

Technology aimed at improving ship efficiency is frequently developed and employed partly to allow newbuildings to meet the EEDI requirements but mostly driven by operators desiring to reduce fuel costs. This is especially so when a vessel has already satisfied the EEDI requirement but the owner continues to add features improving efficiency beyond the compliance level.

Some have questioned owners’ commitment to making such improvements but there are good reasons why owners can benefit. Reducing fuel consumption when fuel costs are for the owner’s account is a clear saving but if the ship is time chartered then the owner is not responsible for providing fuel. Even so, the time charterers generally put fuel consumption high on the list of factors affecting choice of ship to charter and so a more efficient ship will have an advantage that can be a premium hire rate or the difference between employment and lay-up in a poor market. Every method of reducing fuel consumption that can be employed has the added environmental benefit of cutting exhaust emissions.

Achieving savings from fins to fouling reduction

Energy saving devices (ESDs) can come in many guises ranging from hull modifications, through to propeller/rudder combinations and appendages and adaptations to engines and machinery. Taking things a little further, the term can include means of exploiting energy from the wind, sun and waves or storing excess power by way of batteries for use later.

Today, ESDs have become linked in the minds of many to the slow steaming strategies adopted by some operators – particularly in the container trades. While it is true that some devices such as turbocharger cutouts and concepts such as variable turbine geometry have come about simultaneously with slow steaming, their use can be extended to vessels for other reasons as well.

Several means of cutting fuel use were explored in the ShipInsight Guide to ESDs and employing one or more of the devices could lead to savings from 2% to 17%. In many cases the payback period is measured in months and not years.

Interest in batteries as energy storage systems is of growing interest to many shipowners and the number and types of ships employing them is growing. There is no doubt that ships with highly variable energy loads will benefit most but all ship types have periods when energy production exceeds consumption and a battery could be charged from the ships own power sources. Using the battery for port entry and exit would definitely reduce emissions and help improve shipping’s image.

Software too has a role to play in reducing fuel use and so cutting emissions. Two types of application in particular are worthy of particular consideration; Trim optimisation and weather routeing. Both have been heavily promoted by proponents of e-navigation although the need for such software has been questioned by some who believe that it undermines the knowledge and expertise of ships’ navigating officers.

Coatings used to protect against hull fouling have different environ mental impacts. By preventing fouling they allow ships to burn less fuel and therefore play a role in reduction of exhaust emissions. However, even though TBT which was said to have had an adverse environmental effect causing problems for some marine organism has now been banned from use, some are saying that the copper-based substitutes are also hazardous.

Details on most of the current range of coatings and the technologies employed can be found in the ShipInsight Guide to Paints & Coatings. While criticisms are being directed at the replacement anti-fouling products for still having the potential to hard wildlife, the IMO has recognised the role that anti-foulings can have in preventing species transfer. In July 2011, the IMO issued RESOLUTION MEPC.207(62) “Guidelines for the control and management of ships’ biofouling to minimise the transfer of invasive aquatic species”. Currently the guidelines are purely advisory, although flag states are encouraged to ensure their use on board ships. It is expected that at some future date, the guidelines will become mandatory.

This expectation has increased recently as the IMO has pushed the question up the agenda now that the issue of ballast water treatment appears to have been finalised.