NavigaTE Explainer

Published — August 23, 2023

The NavigaTE Explainer is developed to help demystify NavigaTE. The document explains NavigaTE in simple terms, elaborating on the model choices that are made without delving into the equations.

The NavigaTE Explainer does not explain the assumptions used in the model, only the model choices.

Get a sneak peek of the chapters below.

Chapter 01



NavigaTE is a simulation model that projects how the global fleet may evolve under various conditions. It is developed to provide insights into shipping’s transition towards net-zero emissions.

The NavigaTE model simulates the development of the global fleet by imitating the industry’s decision-making on newbuilding, retrofitting, and fueling of vessels. By tracking these decisions, the model can estimate if a given set of economic, technological, and regulatory conditions are likely to lead global shipping towards net-zero emissions by 2050. Furthermore, the model can be used to quantify the transition impact of e.g., novel technologies, regulatory levers, fuel availability constraints, and the timing thereof.

The NavigaTE model covers shipping’s entire value chain from fuel feedstocks to vessel operations. This end-to-end view allows the model to indicate which constraints are likely to determine the transition pace for shipping.

It is important to remember that NavigaTE is only a model. It uses general methods for predicting complex human behavior and does not account for all possible options. Therefore, the results should be interpreted qualitatively, not quantitatively. Hence, NavigaTE only brings value when the results are analyzed and put into a broader context.

Illustrative transition model workflow around NavigaTE

Chapter 02

Vessel selection criteria


NavigaTE models the global fleet by a set of representative vessel types. These representative vessels are usually defined by segment (e.g., bulk carrier or tanker), size (e.g., 35k dwt or 100k dwt) and engine technology (e.g., dual-fuel methanol). The modeled decisions of the representative vessel regarding fuel choice, energy efficiency retrofit, fuel conversion, and more, are thus representative for hundreds or possibly thousands of vessels.

NavigaTE tracks the age of vessels and based on that scraps older vessels and replaces them with newbuilds to satisfy a certain trade volume. In the early years of the simulation, the newbuilds are determined by the orderbook, and later it is decided by a combination of the expected cost and inertia (past decisions influencing current decisions).

As older vessels are scrapped and replaced by newbuilds with a different engine technology (e.g., dual-fuel methanol or ammonia), the overall fleet’s ability to operate on alternative fuel grows.

Example of fleet development for a representative vessel

Ammonia, Methanol, Methane & Fuel oil refers to engine technology, not fuels.

Chapter 03

Energy efficiency


Energy efficiency is for modeling purposes split into two categories, namely energy efficiency and alternative power. Energy efficiency (e.g., air lubrication) reduces the energy demand of the vessel but yields diminishing returns as more technologies are installed. Alternative power (e.g., Flettner rotors) satisfies part of the energy demand of the vessel and is consequently subtracted from the energy demand.

Energy efficiency and alternative power can be installed either on newbuilds or retrofitted onto existing vessels. The decision whether to install on newbuilds or retrofit is based on a business case where the expected future fuel savings are compared to the cost of installing and maintaining the technology.

The fraction of the fleet that will install a given technology depends on the payback period and age of the vessel.

Illustration of the fleet installing a technology as a function of payback period

Note: The uptake curve can be varied to test its sensitivity.

Chapter 04

Fuel conversions


It is possible for a vessel to convert to a different fuel technology, namely change the engine, tanks, etc. to enable the ability to operate on alternative fuels.

The decision of whether to perform a fuel conversion has two main dependencies. First, there must be a positive business case based on the cost of expected future fuel consumption. Secondly, there must be a greater supply of these fuels than there is demand. If there is no surplus of supply, it makes better financial sense to postpone the fuel conversion until there is.

Example of a decision regarding fuel conversion of existing vessels

1: Currently limited to bulk carriers, containers and tankers due to limited data.

Chapter 05

Fuel selection criteria


Fuels are used to satisfy the energy demand of the vessels. Based on a certain operational profile, the amount of energy efficiency and alternative power, NavigaTE calculates the energy demand that must be satisfied by consuming fuels in the power system of the vessel.

The decision of which fuels to bunker in a given year is determined for the entire fleet simultaneously. The underlying idea is that each vessel will bunker as cheaply as possible while satisfying all necessary technical requirements, e.g., bunkering enough to meet the energy demand. Since the supply of certain fuels is limited, the cheapest option is not always available in sufficient quantities and a combination of fuels must be bunkered across the fleet.

Example of a fuel distribution

Chapter 06

Fuel cost and emissions


The cost and emissions of different fuel pathways are calculated using a bottom-up approach. This means that the production of the fuel is broken down into smaller components, such as the production of feedstock (e.g., e-hydrogen. For each production process, CAPEX, OPEX, energy demand, cost of feedstock, and emissions are assigned. If a feedstock is itself produced, then that process is further broken down and calculated.

Ultimately the costs and emissions of each individual process and feedstock in the branch are added up yielding the overall cost and emissions associated with the given fuel pathway.

Bottom-up calculation for production of a fuel (e-methanol example)

1: Renewable electricity is currently considered a feedstock based on an assumption of mega-plants with stand-alone electricity generation. 2: A bunker fuel is a fuel that can be used onboard a vessel.

Chapter 07

Fuel availability


The availability of fuels is determined in three ways. The simplest is that the fuel is unconstrained, such as fuel oil and LNG. The second is that a forecast of the fuel supply in any given year is provided directly to the model. The last is that the model chooses which fuels to ramp up based on the cost, scalability, and demand.

For the last option, a forecast is provided of how many fuel plants can be built per year. The model then decides which types of plants to build, based on the size of the plants, the cost of the fuel and the demand from the fuel. All these parameters may change in time which allows the model to dynamically ramp-up different production capacity at different times.

Example of user-provided fuel availability constraints (EJ/year)

Chapter 08

Identifying bottlenecks


The pace of the transition is determined by a combination of the roll-out of energy efficiency and use of alternative fuels. While energy efficiency is a crucial component in decarbonizing the industry, it cannot bring the emissions to zero. Therefore, the uptake of alternative fuel becomes the determining factor for the pace of the transition. The uptake of alternative fuel is determined by multiple factors, the demand from the vessels able to operate on them, the supply of the fuels, the cost, and inertia related to e.g., offtake agreements.

At any given time, the pace of the transition will be limited by one of these factors. NavigaTE helps to identify which of them is likely to be the bottleneck in the transition.

Demand, supply, and consumption for a single fuel pathway (all constraints)

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