The aim of the new system was to obtain better operational performance and lower lifecycle costs by reducing maintenance and avoiding hunting of reactive power. In the last decade, the focus on the environment
has become increasingly important, and more environmentally friendly vessels with lower emissions and better fuel economy have become the order of the day. Siemens’ answer to this issue, and to the need for improved performance and reduced lifecycle costs, was variable speed diesel engines that optimise the vessel’s operation. As Siemens was developing its new systems, Østensjø Rederi was looking for a more environmentally friendly offshore vessel than the dual-fuel options that were available on the market. Østensjø Rederi decided to research the options and generated a study to compare fuel consumption, greenhouse gas emissions, cost implications and investment for four engine types: • fixed speed diesel engines • dual-fuel engines • gas engines • variable speed diesel engines
The study showed that variable speed diesel engines achieve impressive savings in fuel consumption and emission of greenhouse gases. The results were verified by Marintek, part of the Sintef research organisation in Norway. Siemens claims that the variable speed diesel propulsion system it developed based on the studies conducted by Østensjø Rederi reduces total energy consumption by 15 per cent compared with earlier diesel-electric systems and by 23 per cent compared to gas/dual- fuel engines. Total NOx and greenhouse-gas
Bluedrive Plus C – the benefits
• lower fuel consumption • reduced greenhouse gas emissions • reduced diesel engine maintenance costs • 30 per cent less space required for electric power equipment • enhanced efficiency • low investment cost compared to gas/dual fuel systems • makes full utilisation of SCR systems and reduced NOX emissions possible • increased lifetime of diesel engines, especially for high speed engines • reduced space, volume and weight of electrical systems • increased overall efficiency of the electric system • clean power supply to all auxiliary consumers • no rectifier transformers
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emissions are lower compared with vessels using conventional
diesel-electric or gas powered
solutions. A comparison with the results obtained with dual-fuel offshore vessels with the same operating profile showed that greenhouse- gas emissions were 27 per cent lower for the variable speed diesel engine alternative. Based on these results, Østensjø Rederi chose variable speed diesel engines for its newbuild, together with Siemens’s Bluedrive C Plus electric propulsion system, which allows the operator to set the lowest possible speed to deliver the highest engine efficiency.
Compared with a range of alternatives, including fixed speed diesels, dual fuel and gas- driven engines, the Bluedrive Plus C variable speed diesel concept had the lowest level of NOx emissions, Siemens claims, and also provides the flexibility to choose different diesel engine solutions, with regard to engine type, engine numbers and manufacturer, compared to conventional diesel-electric propulsion systems. According to Siemens, dynamically-positioned (DP) offshore vessels also benefit from Bluedrive C Plus. When operating in DP mode, power consumption is normally low. The Bluedrive Plus C system slows down the diesel-engine speed to the most fuel efficient at corresponding power. However, speed can be immediately increased on demand. Reduced diesel-engine speed cuts noise and vibration across the whole vessel and brings down maintenance costs. In conventional electric propulsion plant, the diesel engines run at speeds that correspond to
electric power generation
at 50 or 60Hz; in contrast, the Bluedrive Plus C concept is completely independent of engine
speed. Using selective catalytic reduction (SCR) equipment with the Bluedrive Plus C further reduces emissions. Bluedrive Plus C controls the speed and power of the engines in line with the vessel’s total power requirement. Each engine can be set at different speeds, which means fuel economy is optimised. As only active power is fed from the generators, there are no issues with circulating reactive power, hunting of generators, or voltage control adjustments for each generator, as no reactive power is generated.
The parameters of the speed and power characteristics of the engines are set in Bluedrive Plus C according to engine type. Bluedrive Plus C includes a power management system, power plant protection system, and the generator power adaption system. All of these systems are integrated into Bluedrive Plus C’s control system in order to obtain the lowest possible specific fuel consumption and the highest availability from the electric power station. This secures the vessel’s safe operation and avoids blackouts and other undesirable incidents.
New developments in power electronics
make it possible to build the Bluedrive Plus C main switchboard as one unit that reduces the electric power equipment footprint by 30 per cent. This switchboard incorporates the generator,
bus-tie panel and frequency
converters for the main propulsion system and thrusters. Furthermore, the bus-tie breaker in Bluedrive Plus C is replaced with a beneficial electronic breaker, which can, among other things, handle unexpected operational situations. OSJ
Johannes Østensjø, chairman of Østensjø Rederi, with Alvaro Platero (right), president of Astilleros Gondan and Daniel Scavuzo, the yard’s commercial manager
Annual Offshore Support Journal Conference and Awards 2013 I 31
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