Research Publications
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Item Seakeeping analysis of an indian research vessel /(Elsevier, 2017-05-01) Ramesh, U. S. ; Pavan Kumar, G. V. V.A multidisciplinary research vessel Sagar Manjusha was considered for seakeeping analysis, which was exclusively used for deployment, maintenance and retrieval of data buoys, Tsunami buoys and so on. During rough sea conditions, the ship undergoes extreme rolling, which hinders deployment/retrieval operation. It also leads to seasickness for scientists and crew onboard. An experimental study was carried out to improve its seakeeping qualities. Ship Motion Reference Unit (MRU) data and the corresponding wave climate data were collected to study seakeeping capabilities. A model test was carried out in a towing tank facility and the design was optimized based on outcomes of test results. An Anti-Roll Tank (ART) was fabricated and installed on boatdeck. Inclination test was carried out in the presence of Indian Register of Shipping surveyor. Stability booklet was prepared as per class recommendation and the procedure was accepted by the class. It was observed during testing in rough sea condition that ship rolling had reduced by considerable amount, which in turn improved comfort and safety during extreme sea conditions. This experiment resulted in a transformation of an innovative idea into best outcome so that similar problems can be solved and the ship’s comfort, safety, productivity and so on can be improved considerably. Seakeeping analysis and installation of ART resulted in improvement in the safety of vessel, onboard machineries, instrument used for scientific research and quality of life onboard.Item Underwater noise radiated by fishing vessels in visakhapatnam fishing harbor /(Journal of Offshore Structure and Technology, 2019-04-24) Kumar, G. V. V. Pavan ; Ramesh, U. S.The sound has always been a better measure to understand the oceans. Among the various sources of underwater noise, mainly physical, biological and anthropogenic, it is seen that through the increase in anthropogenic noise in the oceans, the ambient noise levels are rising. Fishing vessel radiated noise has been a major concern in the fisheries acoustic scientific community due to the possible effects on altering the natural activities of the target species. The fishing vessel noise signature shall be valuable in building a quiet vessel with effective combination of the machinery in opposing excessive noise levels. In the present paper, the measurements of the underwater noise levels within the Visakhapatnam fishing harbor (VFH) limits are detailed to understand the fishing vessel radiated noise levels. The VFH is a bay spreading over 22 ha next to the Visakhapatnam Port channel entrance. At VHF, there are around 700 fishing boats engaged in fishing activity within the coast of Andhra Pradesh. A vertical omni-directional hydrophone and TASCAM handheld linear PCM recorder was deployed at five different locations with deployment depth of 2 m within the VHF bay. Fast Fourier Transformation spectral analysis program is used to post-process the time domain signal to the frequency domain. The measured data helped to understand the ambient noise levels within the VFH limits being ~120 dB re 1 μPa and with a distant boat idling having peak amplitude 136.97 dB re 1 μPa at peak frequency of 425 Hz. The regular fishing vessel movement recorded peak amplitude 160.39 dB re 1 μPa at peak frequency of 425 Hz. The changes in the ambient noise levels due to the fishing vessel movement recorded a significant increase in sound pressure levels (SPL) by about 20 dB. The increase in SPL is mainly due to propeller and machinery radiated noise which is clearly identified in lower frequency range <500 Hz. The measurements also helped to understand the effect of each vessel type on the ambient levels due to vessel movements, mainly during entrance and exit within the VHF bay. However, the noise pollution due to vessel movement has similar effects on the local environment, i.e., the residential area close to VFH.Item Energy management and charging portfolio analysis for future battery powered harbor vessels /(IEEE, 2023-05-11) Ramesh, U. S.This article intends to provide key insights to the marine designers and port authorities for adapting battery-operated zero emission electric harbor vessels (ZEE-HVs) and plan the resources for charging infrastructure. The present study is a cumulatively coordinated analysis of various significant aspects concerning the adaptation of ZEE-HVs for short-endurance commercial maritime operations. The sizing of onboard battery energy systems (OBES) is discussed for different short-endurance ZEE-HVs by considering the speed-resistance characteristics of the hull and open-water characteristics of the propeller without limiting their operations for specific load profiles/operating cycles. Charging portfolio selection is critical for a marine vessel as the OBES size is several times higher than a regular electric vehicle's battery. Hence charging portfolio selection criteria are presented to select a suitable battery charging protocol for each ZEE-HV as per the OBES ratings and available idle times on a typical day. Since the port is a commercial spot, uncertainty in resource planning leads to penalties and loss of goodwill. Therefore, Monte Carlo-based iterative analytical method is adopted to forecast the ZEE-HVs' maximum possible charging power demand on a typical day. By the load forecast data, optimal sizing of the load peak shaving battery (LPSB) was performed to limit load fluctuations at the port grid. The synergy of ZEE-HVs with LPSB and bi-directional charge-discharge controller is pivotal for effectively administering the seaport shore charging facility, which is demonstrated for a typical energy management cycle.Item Energy management and charging portfolio analysis for future battery powered harbor vessels /(IEEE, 2020-12-16) Ramesh, U. S.The growth in Battery Powered Harbor Vessels (BPHV) signifies the necessity for a study on charging infrastructure and energy management at the seaport. This paper analyzes the charging portfolio specifications and energy management for different types of prospective BPHV at Visakhapatnam port. A brief study was conducted to identify the suitable charging method for regularly operated BPHV like Mooring Launch (ML), Pilot Launch (PL), Fishing Vessel (FV), and Tug Boats (TB). An iterative analytical study is characterized to forecast the BPHV charging load demand over a 24-hour duration and performed optimal sizing of Shore Battery Bank (SBB) to shave the critical load peaks and limit load fluctuations at the port grid. The energy management at the prospective seaport charging infrastructure is presented with relevant results by discussing the significance of Active Line Conditioner (ALC) and Bidirectional DC-DC Converter (BDC).Item Sizing of energy storage system for a battery operated short endurance marine vessel /(IEEE, 2020-01-01) Ramesh, U. S.Conventional marine vessels are operated by either diesel or diesel-electric propulsion which results in the production of harmful emissions that affect the lives inhabiting near the harbor. By employing the Battery-operated Electric Propulsion (BEP) system, harmful emissions released by marine vessels will be reduced to zero. In this study, a harbor tugboat with 30 tonne weight carrying capacity, maneuvering at 9 knot speed is considered for the sizing of BEP. The effective power demanded by the marine vessel when operating at rated speed with full weight is calculated from the hydrostatic and speed power analysis, and the designing of a suitable propeller is discussed. The power train is presented with the calculation of power rating for each component of BEP. Battery count and its total weight are evaluated with different types of Li-ion batteries which are commercially used in electric vehicles and a suitable one is identified for BEP application. Sizing of the supercapacitor for DC link and battery buffer is presented. For the short endurance operation of a marine vessel, the weight of the battery based energy storage system (ESS) is compared with the conventional diesel-electric generator.Item Underwater noise levels in Indian waters off the coast of Mormugao Port /(Taylor & Francis, 2019-06-25) Kumar, G. V. V. Pavan; Ramesh, U. S.Among various factors influencing the ocean noise levels, shipping traffic radiated underwater noise levels were identified as the major contributors. The increase in ambient noise levels due to natural and anthropogenic sources threatens the marine species communication. India has a coastline of 7,516.6 Km with 12 major and ∼187 minor ports. The hydrophone system measured for 39 days helped in investigating the distant shipping traffic lane noise levels and its influence on ambient noise levels of the region. The ocean noise levels measurement were ∼115 dB re 1 µPa for the prevailing environmental conditions. The noise exposure levels were ∼10 dB higher at <1 kHz due to ship passage to and from the port. The fish noise dominated the ambient sea noise mostly at high frequencies >1 kHz. The maximum and minimum range of shipping noise spectra for both the month’s data indicated peak sound pressure level in the lower frequency. Thus, the outcome of the measurements helped in understanding ocean noise levels off the coast of Mormugao Port and the influence of shipping traffic. A similar study for longer duration shall be useful to develop specific traffic lanes in the port entrance which is free from the mammal movements.Item Coordinated control of electric tugboats considering inductive power transfer for better fuel efficiency /(IEEE, 2018-12-01) Ramesh, U. S.Developments in the shipping industry have necessitated the use of numerous tugboats at harbors for high revenue growth. Over the time, electrification has gained significant potential in transport sector in view of meeting the strict emission norms. Lately, the tugboats are powered with diesel electric generators and energy storage systems to meet its propulsion and auxiliary loads. Optimal use of power sources leads to have better fuel use efficiency with reduced footprint of greenhouse gases. This paper presents an optimization technique for scheduling available power sources to meet onboard load demand. Furthermore, to transfer surplus electric power available in an electric marine vessel to the tugboats in operation nearby, the concept of wireless inductive power transfer (WIPT) is proposed for contactless charging and discharging of tugboat batteries. In addition, doubly fed induction machine (DFIM) as variable speed generator is considered in this paper for tugboat power generation in the interest of better operational efficiency at part load operation. From the test results, it is observed that the tugboat with 50 kWh battery storage system offers 21.4% of fuel saving and 25.5% of fuel saving with proposed WIPT, when compared with conventional tugboat. Further, an additional 2.6% of fuel saving is achieved by adopting DFIM for tugboat power generation.Item Fuel Minimization in Diesel-Electric Tugboat Considering Flywheel Energy Storage System /(IEEE, 2018-06-01) Ramesh, U. S.Energy storage system plays an important role in electric propelled marine vessels for efficient power management. This paper considers flywheel storage system in place of battery storage for reducing fuel consumption in a diesel-electric tugboat. To achieve fuel efficiency, optimal scheduling and controlling of energy sources and energy storage devices take place in consideration with tugboat load demand. A simple fuel optimization problem considering flywheel and battery storage system is formulated. Economic analysis is done in consideration of both the storage systems. Furthermore, DFIM as variable speed generation is considered in this research for tugboat power generation in the interest of better efficiency at part load operation. Fuel usage at fixed speed and variable speed diesel engine with flywheel and battery ESS are correlated. From the test results, it is observed that the adoption of 50kWh battery and 50kWh flywheel ESS offers 21.4% and 23% of fuel reduction in comparison with diesel-mechanical propelled tugboat. Whereas the adoption of variable speed operation of diesel generator with 50kWh flywheel offers 25.6% of fuel reduction.Item Optimization with load prediction in asynchronous generator driven tugboat propulsion system /(IEEE, 2017-12-01) Ramesh, U. S.Mostly tugboats are powered by diesel-electric generators for meeting power of auxiliary loads and of electric motors for propulsive load. This paper proposes the optimal fuel management in diesel-electric generators considering doubly fed asynchronous machine (DFAM) as generator. An optimization problem is formulated to schedule the available power sources aiming for best possible fuel efficiency. The performance of optimal control strategies critically depends on future load applied in generator. Considering this for predicting tugboat load demand a simple predictive methodology is proposed based on the average mode time per cycle. The proposed control mechanism is able to respond to any sudden load change and also to emergency halt condition. DFAM as generator is considered for improving the system efficiency at low load region. Speed of the diesel engine is decided by the load demand. Output voltage and frequency of DFAM at variable speeds are regulated by power electronic convertors, connected in rotor circuit.Item Control strategy for fuel saving in asynchronous generator driven electric tugboats /(IEEE, 2016-01-01) Ramesh, U. S.Usually electric tugboats are equipped with diesel engine based electric generator for power production, battery for supplying power to auxiliary loads and electric motors for propulsion. This paper proposes control strategies for diesel engine and electric generators used in electric tugboat to improve energy efficiency of the system. Doubly fed induction machine (DFIM), asynchronous in nature, is considered in this research which serves as generator (power production). The speed of diesel engine is controlled in accordance with the power demanded by the tug. Output voltage and frequency of generator during sub-synchronous operation are regulated by controlling its rotor current with the help of power electronic convertors. Comparison of fuel consumption at fixed and variable speeds of operation is performed. From the test results, it is observed that the variable speed operation of diesel generator offers significant reduction in fuel consumption.