Poulsen Hybrid Monorotor

Transcription

1 Poulsen Hybrid Monorotor

2 The Poulsen Hybrid Monorotor A Novel Approach to Flettner Marine Propulsion January 2012 Background The Magnus effect defines thrust developed by spinning a cylinder in an air stream and was first utilized for marine propulsion by Flettner in The cylinders are rotated by auxiliary power and create thrust dependent on the wind speed and direction relative to the course. Lately the concept has gained new interest for supplementing the engine power in cargo ships with the object of reducing fuel consumption and carbon emissions. The E-ship, launched in 2010 by wind energy company Enercon has 4 rotors, each 4 meters in diameter by 25 meters tall. Photo: E-ship At the present time two companies are proposing systems for installing multiple Flettner rotors typically 4-5 meters in diameter onto bulk carriers and other cargo vessels, claiming potential fuel savings in the order of 20% to 50%. The rotors being offered are telescoping or foldable in order to not interfere with loading and unloading of cargo. Photo: Magnuss

3 Photo: Windagain The thrust developed by a Flettner rotor depends on its projected area, and for example a 4 meter rotor about 25 meters tall may generate power in the order of 400KW at 14 knots in a 10 m/s (20 knots) crosswind. With this kind of rotors typically 4-6 systems are required per vessel in order to accomplish projected savings. Folding and telescoping collapsible rotors require modifications to vessels such as wells for stowing them below deck when collapsed and local strengthening of the deck structure and frames in order to safely absorb the large thrust forces and bending moments developed during operation. The collapsing mechanisms are expensive, add complexity and require special maintenance. As a consequence the total cost of systems and labor and downtime for installation as well as cost of use is high and increasing relatively with the number of rotors in the system.

4 The Poulsen Hybrid Monorotor The Monorotor offers a novel way of configuring and locating a Flettner propulsion system which is low in cost and contains a minimum of moving parts. It does not interfere with loading and discharging and is dimensioned, so its height does not exceed the height of the standing rig. The system is not collapsible but yet may be easily and momentarily secured in case of extreme wind or excessive roll and pitch of the vessel in the sea. A single rotor must have a large diameter in order to match the performance of the multiple slim and tall rotors currently being proposed for cargo vessels. Typically a monorotor for a Handysize vessel of 30,000 to 40,000 dwt will be 15 to 20 meters in diameter and meters tall. A cylinder this large would be a significant obstacle if placed on the main deck, besides obstructing the view ahead from the bridge. As a consequence the Poulsen Monorotor is mounted aft of the deck house and straddles the stern of the vessel with its lower edge raised 3 or 4 meters above deck so as not to impede mooring operations. An alternative solution suitable for very large vessels such as VLCC tankers and 200,000 to 3000,000 dwt bulk carriers may feature a second monorotor mounted above the focsle deck and straddling the bow. Locating the second rotor at the extreme bow does not impede loading and discharging and at the same time brings the blind sector as viewed from the bridge within or close to the 5 degree angle specified by the IACS.

5 A Monorotor system comprising 1 or 2 large diameter rotors, each generating the same amount of trust as 4 or 5 slim rotors of similar height combines the following features: Is less complex and contains fewer moving parts. The cost per ton thrust is reduced by over 50%. The supporting structure may be designed more efficiently within the ample space inside the rotor. Less reinforcement of the deck structure is required since forces may be spread over a larger area. The main support legs can be placed 10+ meters apart and in most cases connected directly to the hull plating near the corners. Interference with gear and daily operation of the vessel is minimized because the rotor is elevated 3-4 meters above deck, also raising system safety. Rotational speed is reduced from rpm to rpm thus extending bearing life and periods between scheduled maintenance. Easy installation, possibly during scheduled maintenance, may eliminate down time. Calculated Performance: 16 meters diameter x 22 meters tall Monorotor suited for a dwt vessel. Cruise speed: 14 knots Wind speed m/s Knots Rotor rpm Thrust tons Power KW HP d speed m/s About 50 KW of electric power is required to spin the Flettner rotor. Effect of Wind Direction Wind angle (degrees) Power %

6 The rotor is designed to rotate at max 60 rpm. The table shows how the thrust can be kept within the 55 ton design limit by adjusting the rotor rpm. Thrust is monitored by strain gauges located on the main axle at the point of max stress just below the lower radial bearing. A simple program can be developed for adjusting rotor rpm within safe limits while maximizing thrust. The program will also monitor wind speed and angle of roll in order to stop and park the rotor in extreme weather. When evaluating the performance of the rotor system it is important to keep in mind that it contributes thrust and thus propulsion horsepower. On the other hand, when calculating propulsion horsepower of a marine engine its rated power must be adjusted for propeller efficiency ( ). Thus, for example 2,000 Flettner horsepower equals about 2,900 engine brake horsepower. System Cost and Benefits The cost of the Model16/22 Monorotor is estimated at US$ 600,000 to 700,000 including installation. It is intended for a vessel of 35,000 to 40,000 tdw, but may be used on larger vessels as well and save the same amount of fuel under similar conditions. The system weight is about 55 tons. Models optimized for other sizes of vessels will become available as required. The Monorotor may be retrofitted onto existing bulk carriers and tankers and reduce fuel usage and carbon emissions during the life of the vessel up to 25 years from now. Equally important, Monorotor systems may be designed into new builds and include modifications in the superstructure etc. to improve efficiency. In many cases new designs may also benefit from engine optimization. For example in a Handysize vessel, due to the supplemental power generated it may be in order to reduce the size of the main engine about 20% while saving some $500,000 in cost and 50 tons of mass, approximately balancing out the cost and weight of the Monorotor installation. Also, dependent on the trade and length of the journey, it may be safe to reduce the amount of bunkers carried by up to 50 tons. The importance of any system for harvesting sustainable energy aboard an oceangoing vessel depends on world market fuel prices, and unfortunately these are expected to keep increasing, perhaps in all future. In today's market when shipping companies are struggling to break even, 20-30% fuel savings may well change the entire dynamics of the game.

7 Proposal, 2 Rotor Retrofit, VLCC Tanker

8 Comparison: 16/22 Monorotor / 2.1 MW Wind Turbine Flettner rotors harvest sustainable energy from the wind so it is relevant to compare their performance with that of land-based and off-shore wind turbines. However, for an economical comparison it is important to consider the different venues and values per KW hour of energy produced. A marine engine consumes 170g of heavy fuel per shaft KWh at a cost of $0.14 based on currently $800/ton. However, due to propeller loss only 70% of the shaft power is available for moving the vessel so the true cost of propulsion is $0.20 per Kwh, and realistically this value can be applied to energy from wind power harvested on a vessel at sea. Moreover this energy does not need to be converted to electricity and can be utilized at any time without transmission losses. For comparison, in land based wind energy systems the alternative source is coal fired or hydro electric power plants, where energy is generally rated not above $0.05/KWh at the plant, so in most venues this value must be applied to wind power as well. 16/22 Monorotor on Handysize vessel Rated output at 15m/s (29 knots. 2,500 KW Estimated average output while at sea 1000 KW Power lines and transformers none Transmission losses none Wind quality, Ocean Estimated cost, installed $ ,000 Weight of system, (steel 45%, aluminum 55%) 55 tons Installation downtime at yard. < one week Value generated.1000 KW 200 days at sea at $0.15/KWh $720,000/year Time to recover investment less than1year Reduced CO2 emissions 2,700 tons/year 2.1 MW General Electric Wind Turbine Rated output 2,100 KW Estimated average output 800 KW Infrastructure required. Service roads etc. yes Trunk power line, transformer yes Transmission lines yes Transmission losses yes Wind quality. Inland or seashore Cost $2,000,000 Weight of turbine (steel 90%, fiberglass 10%) 280 tons Value generated, 800 KW 800h/year at $0.05/KWh $320,000/year Time to recover investment >6 years Reduced CO2 emissions 3,600 tons/year

9 The Poulsen Hybrid Monorotor May be easily retrofitted onto existing vessels with minimal changes. May be incorporated in new builds in the design stage. Does not impede loading and unloading or mooring and anchoring. Does not impede view from the bridge. Is reliable and easily maintained. Minimum of moving parts. Does not require additional or specialized crew to operate. Saves 20-35% on fuel consumption dependent on wind conditions. The investment is recovered in 1 year or less. Many factors over and above the wind conditions may affect the actual efficiency, and it really does not make sense to announce potential percent fuel savings with this or any other wind propulsion system. Rather than physical efficiency of the energy conversion, the overriding factors must be return on investment, reliability, and ease of installation. The above calculations are believed to be conservative but actual performance can only be determined through sea trials with a full size prototype. January, 2012 Patents Pending.