DNV GL: Battery power improves performance

DNV GL informed that it is cooperating with industry partners to determine how the industry can benefit from advances in alternative power engineering, especially in battery technology, to enhance the offshore oil and gas sector.

Offshore vessels offer an attractive business case for hybrid power solutions incorporating batteries. While the common diesel-electric power and propulsion systems are quite flexible, they tend to operate inefficiently when running at very low loads for extended periods of time while occasional peak loads are expected. Furthermore, battery systems can provide backup power to meet the strict redundancy requirements for dynamic positioning (DP).

However, manufacturers must meet many regulations and requirements, and standardization is an urgent concern to overcome cost hurdles. Questions regarding economic feasibility, battery capacity, reliability and safety, and specific applications must be answered for the industry to embrace the technology.

These are the topics two industry initiatives have been addressing:

• FellowSHIP IV, a two-year joint project of DNV GL, Wärtsilä Norway and Eidesvik Offshore : It is studying the applicability of maritime hybrid battery power systems under a life cycle perspective;
• “Hybrid Power” Joint Industry Project recently completed by DNV GL, Taratec Corporation, BG Group, Seacor Marine, ABB, Samsung Heavy Industries, Cummins, C-Rate Solutions and the University of Sao Paulo: It has assessed barriers to the adoption of hybrid power, associated technical challenges and potential benefits.

The FellowSHIP IV project, scheduled to end in 2017, uses continuous condition and performance measurements conducted on a 442 kWh Li-ion battery system on board the platform supply vessel (PSV) Viking Lady, to gain insight into the actual operation of a maritime battery system. In addition, a variety of simulations are being performed to draw conclusions regarding fuel savings, emission reductions, power management strategies, design improvements, operational benefits, cost-saving potential and competitive advantages.

The Hybrid Power JIP, tasked with challenging established industry practices and determining the best role for alternative power, has identified specific challenges and quantified all benefits of hybrid power systems. The team found that hybrid power architectures are technically feasible for tugs, OSVs, shuttle tankers, and drill ships, with viable return on investment (ROI) and payback periods.

The JIP team analysed four ship types with selected operational profiles to quantify the fuel, emissions, and reliability benefits of hybrid power, including dynamic positioning, industrial services such as drilling, propulsion and backup power. The result is a multifaceted value proposition:

• operational efficiency is improved by balancing diesel engine loads and avoiding wasteful idling periods
• reducing engine running time also cuts CO2 and other noxious emissions.

Batteries can be optimized either for fuel efficiency or for backup power, depending on the given application. In hybrid DP operations, batteries can supply load for approximately one third of the operating time, reducing generator cycles and responding faster than a generator set. As for backup power applications, economic feasibility depends on the ratio of investment cost vs desired duration of backup power availability.

Fire safety is a key concern for battery rooms, which must be designed to be functionally independent of the conventional architecture of the vessel, with fully independent ventilation, cooling and fire suppression systems and a sophisticated, integrated control system.

Payback times for battery systems range between zero and 7,700 engine operating hours. Efficiency improvements of up to 34 per cent were achieved in model studies. Hybrid power technology thus offers tangible benefits; whether they can be reaped will depend on the regulatory environment and a high-quality supply chain.