Energy storage systems that supplement power plants can bolster the environmental footprint of offshore vessel operations
Onboard batteries will reduce load demand on generators and improve efficiency of propulsion systems for transit and dynamic positioning (DP). Energy, stored and released to augment power from engines and generators, can cut fuel consumption on average by 20% and engine running time by more than 40%.
This is the experience of Kongsberg Maritime’s SAVe Energy battery system, installed on DP2 platform support vessels (PSVs) operated by Golden Energy Offshore. Kongsberg installed its battery packs on PSVs NS Orla and NS Frayja in 2019 and has been monitoring energy efficiency and performance for nine months.
Kongsberg data scientist Joakim Kjølleberg says data analysed from these vessels determines the size and capabilities of batteries for future projects. “By utilising a redundant battery connected to the main switchboard in DP operations, we are able to reduce total engine running hours by 43%,” says Mr Kjølleberg. “The increased load and improved efficiency helps the vessel’s crew achieve operational fuel savings of 20%.”
Golden Energy Offshore vessels are connected to power sources in port to charge batteries and run onboard systems. This reduces annual greenhouse gas emissions by around 1,000 tonnes and NOx by three tonnes.
The SAVe Energy concept is a liquid-cooled battery system in a modular design that can be scaled according to energy and power requirements. It can be used for peak shaving, spinning reserve and for full battery power for offshore vessels and workboats.
During co-operation with Golden Energy Offshore, Kongsberg customised its vessel performance and energy consumption service to include battery performance monitoring.
Changes to power supply for the DP systems required re-examination of class and redundancy. In 2019, DNV GL introduced a Battery class notation that applies to lithium-ion batteries of more than 20 kWh installed on vessels and offshore drilling rigs. The classification society also updated its rules for battery installations for DP and propulsion assistance.
DNV GL also updated its rules for DP to include batteries as a spinning reserve and a redundant power source, for DP2 and DP3 vessels.
In November 2019, Northern Ocean’s West Mira became the first semi-submersible drilling rig to secure DNV GL’s Battery (Power) class notation. It has a hybrid power plant using lithium-ion batteries as spinning reserve in DP and supplying power during peak load times.
By using the four converter-battery systems, Northern Ocean estimates it will reduce runtime of the rig’s diesel engines by 42%, cutting CO2 emissions by 15% and NOx by 12%. Its batteries are a back-up to prevent blackout situations and to provide power to thrusters if there is loss of all running machinery on affected switchboard segments.
Technology for delivering power, control and position referencing to DP systems will be presented and discussed at Riviera Maritime Media’s European Dynamic Positioning Conference, in London, on 4 February 2020. For more information, please visit: www.rivieramm.com/events/european-dynamic-positioning-conference