Hybrid-electric power systems are generating more interest, and the business case is beginning to power up initiatives to validate this relatively new technology, writes ABS vice president technology Gareth Burton
Oceangoing vessels, offshore support vessels and offshore installations require electrical power for most things that we often take for granted onshore. At sea, power systems need to cope with almost all elements of energy demand from communications and navigation systems to crew comfort to reliable propulsion systems.
Costs of energy use are key considerations for vessel operators, but there are hopes that hybrid-electric power systems will offer both financial savings and improved environmental performance through lowered emissions.
For the maritime sector, decarbonising marine transport is a critical, yet complex process as new hybrid-electric power systems are being assessed for a number of considerations. Among these are: improving a vessel’s efficiency, increasing its available onboard space and reducing its weight to allow extra space for crew accommodations, cargo and supplies; increasing vessel reliability, power /take-off modes, and voyage range; emissions and acoustic noise reduction above and below the water line; and the capacity to extend this technology to all vessel types, ports and marinas.
How hybrid-electric power systems work
Hybrid-electric power systems can combine internal combustion engine-driven generators and shaft generators, or motors driven by a main engine with an energy storage system (ESS) consisting of batteries and supercapacitors. They can also use other non-traditional sources of power such as fuel cells to form the power generation and propulsion system of the vessel.
The architecture of a hybrid system is designed specifically for the requirements of each individual vessel and each component can be optimised for maximum efficiency. The combination of two or more new technologies when conventional power generation is not installed on board is categorised as a hybrid-electric power system.
Operational flexibility in propulsion techniques
As a result of a greater number of energy components, hybrid-electric power systems offer operational flexibility for vessel operators and owners.
Fuel and battery sources allow for more choice and possibilities on how to manage a typical vessel’s propulsion system, and at various phases of a journey, to help reduce energy consumption compared with traditional power units.
The perception of hybrid-electric power systems is that it is a system that requires an increase in the necessary front-end expenditure, especially during a vessel’s design phase, and that a greater complexity in operation means increased fragility, leading to more inspections and more cost. This is not necessarily the case.
More and more, engine manufacturers are seeing a compelling argument for hybrid power beyond the cleanliness and efficiency gains; hybrid-electric power systems allow for lower horsepower options and more compact engines to be used on board, as well as providing OEMs and vessel owners with an array of options to optimise their fuel or power choice based on energy preference and fuel availability.
Modularity is also important for the most versatile solution and for the largest variety of applications. Hybrid-power configurations allow ship designers and retrofit contractors to select from a range of modular drive systems including diesel, gas, hybrid, electric and hydrogen-based technologies. No one-size-fits-all vessels which is why tailor-made systems can be applied across different vessel types that operate on different routes and for different purposes. From research vessels and icebreakers to ferries, cruise ships, cargo vessels and superyachts, the industry is focused on using clean power technologies that deliver safety while at sea, reduced operational costs, lower emissions and increased vessel value.
Popularity is key to hybrid power growth
Hybrid power sources can revolutionise energy consumption across the maritime industry and heavily reduce emissions, as well as fuel and maintenance costs. With IMO’s greenhouse gas (GHG) strategy, adopted in 2018, setting ambitious targets to reduce total annual GHG emissions by at least 50% by 2050 compared with 2008, hybrid-electric power systems could revolutionise how the seafaring industry is powered. It seeks to reduce CO2 emissions per transport work, as an average across international shipping, by at least 40% by 2030, and a 70% reduction by 2050 compared to 2008.
According to Siemens Energy, 81% of the world’s 91,000 ships are small- or medium-sized and could potentially be converted to electric or hybrid electric using current technology. A study on the electrification of the European ferry fleet, conducted by Siemens Energy and the non-profit environmental organisation Bellona, shows that Europe can reduce CO2-emissions in key countries by nearly 50%, saving 800,000 tonnes of CO2 annually.
Batteries and other solutions have evolved to allow for faster release of energy when needed and have dropped in price in a relatively short period of time, making them more realistic options in hybrid-power solutions for marine applications. Hybrid-electric power systems increase the value proposition at the procurement stage and throughout a vessel’s life. Zero-emissiosn and zero-noise are targets for the shipping industry, and the roll out of hybrid-electric technologies is already having a positive impact. These systems enable engines to be downsized and to use hybrid-power systems for peak-load. Alternatively, the output from a ship’s diesel engine can be reduced, allowing lower fuel consumption.
Diesel-electric hybrid ferries are already transitioning to combine diesel power with electric battery power. More projects in different parts of the world are beginning to emerge with particular interest from across the cruise sector where often ships sail in environmentally protected and highly regulated waters and where hybrid power systems provide an environmentally friendly power-based solution.
Saving on fuel and maintenance costs
While the pressure to reduce fuel consumption and emissions has increased, the operating profile of ships has become increasingly diverse. For example, offshore vessels perform numerous tasks such as transit and critical dynamic positioning operations, while naval ships perform traditional patrol operations in the open sea and are also deployed in littoral operations. These and other varied operational profiles have led to a growing variety of power and propulsion architectures. When applying hybrid-electric power, the vessel-specific operational profiles require detailed analysis to find the right combination of power and propulsion architecture that matches the operator’s need and use of the vessel.
Data is already identifying some substantial direct and indirect cost savings. Hybrid-electric power systems is a technology that will reduce fuel consumption substantially with the potential of allowing for periods of emissions-free sailing.
In cruise operations, vessels tend to sail long distances. Batteries allow vessel operators to manage the load fluctuations on the engine to help it run more smoothly. Likewise, smaller cruise vessels sailing in inland waterways and harbours can use hybrid-electric power to navigate successfully and drive down local emissions levels.
Charging ahead on design and solutions
With the increasing and impressive array of hybrid power technologies making inroads into the maritime and shipping sector, there is a nod to the automotive industry which has been seen as a catalyst for this type of technology. For example, plug-in vessels need a mooring or berth to recharge, much like an electric car at an automotive station.
While the ‘plug-in’ nature of sea-based transport systems is in the short-term very popular, the longer term possibilities will extend with improved electric solutions as battery technology itself further evolves with the use of smarter materials and cell life to increase single-charge operating journey times.
The designing of fuel-efficient marine hybrid electric systems HEPS and advanced lightweight materials for these systems represent upcoming trends in the market. An expanding product portfolio coupled with the latest hybrid power technology trends are the factors to boost market growth.
Hybrids could soon become the power standard with guidance
In any new technology application, the decision to adopt clean energy sources using hybrid systems centres on a coupling of benefits and value for the operator. Hybrid-electric power systems are part of the growing clean energy system.
To support awareness, training, and knowledge-share across the maritime industry on hybrid electric power systems, ABS has developed and released industry guidance,
Practical Considerations for Hybrid Electric Power Systems Onboard Vessels, which explores the different forms of hybrid-electric power systems and their application on board.
ABS believe hybrid-electric systems are a viable option to support the maritime industry in meeting its IMO GHG reduction targets. A wide variety of applications at sea with diverse operational profiles are creating multiple power and propulsion architectures. This latest insight from ABS is designed to support the international shipping industry in capitalising on the potential of hybrid-electric power systems technologies with a focus on safety and sustainability.
