Ulstein Power & Control designed and developed battery system for “Ecofive”

By providing a power and propulsion system with this dynamic approach to any operation mode, the ULSTEIN FX101 trawler design has taken an important step towards future-proofing, featuring properties such as excellent fuel efficiency at high operation loads and excellent fuel efficiency at low operation loads. It will adapt to any new and diverse operation profile during the ship's lifetime, supporting low fuel consumption and low emissions - there’s less sensitivity to major changes to the original intentions for the vessel.

The system is optimized for battery-assisted operations and easily interfaced with new technologies like fuel cells, solar panels, etc. Easy and intuitive mode changes encourage the operator to hunt for lower fuel consumption and less wear and tear on the ship systems.

"The system makes it comfortable to sail on low rmp", says System Architect in Ulstein Design & Solutions, Frode Sollid.

The battery system

One of the natural system extensions of a marine power and propulsion system, pursuing lower fuel consumption and lower emissions, is the battery system extension. The battery system hosts a series of opportunities. For ULSTEIN FX101, the battery system has been developed to operate both in diesel-electrical mode and in diesel-mechanical mode. The diesel-mechanical mode, with an open bus-tie breaker in the main switchboard, requires a dual-feed battery system. The dual feed system has full connectivity to both switchboard sides, even with an open bus-tie, and this way, fully maintains the battery duties in the mechanical mode.

"Another important design choice for the battery for the ULSTEIN FX101 is the ample size of the energy storage. This provides for longer periods of battery-only power, e.g. in harbours, and will eliminate the hunt for the optimal battery State of Charge (SOC) at all times since the dynamic energy reservoir is abundant. A crucial element in user-friendliness, keeping the user confident that the battery system will serve independent of any condition prior to the current stage", Sollid explaines.

Battery system functionality

A battery system can be set up and integrated into a marine power and propulsion system in different ways to serve many different purposes. For the ULSTEIN FX101 the setup of the battery system supports a range of battery system purposes. The main purpose is:

Peak shaving.

The purpose of peak shaving is to allow the battery system to take the dynamic variations induced by electrical ship loads for the diesel engine to avoid throttling to keep up with the changes.

This reduced throttling provides a more stable and efficient combustion process in the engines, resulting in reduced fuel consumption and reduced environmental footprint from diesel engines. This battery function is intended for damping uneven power demands from propeller systems operating under demanding and uneven weather conditions, damping dynamic electrical loads from the equipment on board that is started or stopped.

Increased dynamic response from the power stations

The battery is also used to increase the power system response, especially when a single diesel engine at low RPMs is used to reduce fuel consumption. In such a configuration, the diesel engine has a poor and anaemic dynamic response and does not accept quick load changes. In such engine modes, the battery makes the ship and its operations much more responsive and renders these fuel-saving conditions far more usable.

This is done by the battery due to its capability to take significant and instant load changes on behalf of the engine. The battery may continue for a period, supporting the extra electrical load. Suppose the extra load contributes to a new permanent load situation exceeding the power capability of the engine. In that case, the RPM should increase to a higher state, or an extra genset should be engaged.

"From experience, we know that the operator will very quickly resort to higher RPMs, and even starting an extra engine to make the ship more responsive. This increased dynamic response, or increased agility, we get from a single engine, at low RPMs and in fuel saving mode, assisted by a powerful battery, will eliminate the need for engaging an extra diesel engine during short load peaks", says Sollid.

Temporary load support

With one engine running at a high and optimal load and then entering a temporary load increase exceeding the power capability of one engine, the second engine needs to be engaged if there is no battery assistance. The goal of "temporary load support" is to allow the battery system to assist the power station with electrical power for a limited period to avoid a start-up of an additional engine to handle temporary load increases. These events may occur in the following situations:

- When sailing with one diesel engine on high and optimum load and the ship enters into a manoeuvre/turn, requiring more power. The battery system provides this additional power and prevents the start of an additional diesel engine in the limited period during the manoeuvre/turn.

- When sailing in bad weather with one diesel engine at high and optimum load, the power system will also get dynamic loads. This can lead to the occasional need for an additional diesel engine online. The battery will provide the additional required power and inhibit the start of an extra diesel engine.

Reverse power from trawl winches

ULSTEIN FX101 is equipped with electric trawl winches. These types of trawl winches generate several hundred kilowatts of reverse power when shooting the trawl. This reverse power is directed into the electrical grid. To fully utilize this reverse power from the winches, we may use the battery system as energy storage.

"This way, we may use lost energy to power the ship and the ship system. Either by bringing the energy into the electrical system and using it to power electrical applications directly, or alternatively, we can store the energy in the battery and use it when the need for energy is more relevant. With ample sized energy storage, the energy can be stored and used for different purposes, like an engine less stay at a harbour. A battery system makes it possible to handle energy in a time-independent way."

Pure battery operation without a diesel engine

Pure electric battery operation without the use of a diesel engine is intended mainly for use in harbour mode. The battery will support uninterrupted change-over from main power to battery power in the harbour.

To take care of a functionality such as charging the battery from shore power and conduct uninterrupted switching on and off the shore, the shore power system connection according to the IEC80005-3 standard.

"For FX101, which may need relatively large amounts of power from the shore power to supply consumers like the refrigeration system, cranes, and battery charging, etc. To support this requirement, a 690V IEC shore power directly on the 690V board has been chosen, as this voltage is available on all IEC shore power systems."

The entire need is covered The IEC80005-3 shore power can be connected and disconnected without interruption, whether the ship's power network runs on a generator or a battery. There is a time limit (30 seconds) for the parallel synchronization between generating power on land and the generating power on the ship (Main generator, port generator or battery). Consequently, we are not allowed to run shore power and battery in parallel for a longer time as a generator to remedy load peaks.

"However, with up to 600kW from shore, the entire need is probably covered by the shore power, but the system can still switch over to the battery on board for higher temporary power needs (exceeding shore power capability) and then return to shore power without blackout."

The battery can be continuously charged with shore power because then the battery runs as a consumer and not as a «generator». The battery can, therefore, still be used to take overload at load peaks, but then the battery must take over the entire load until it is transferred back to the shore connection and the battery returns to charging.

"The IEC80005-3 installation is mounted with a connection in the 690V switchboard. The entire ship's "grid" will then be energized when the ship is on shore power. The larger battery can make it possible to power the ship on battery alone for up to 10 hours through a night without an engine and without shore power."