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The electric warship VII - the reality The electric warship VII - the reality Commander GT Little, Royal Navy Eng(Hons), MSc, MCGI, psc(j), Royal Navy, Commander SS Young, MSc, CEng, MIMechE, Royal Navy, and Commander JM Newell, BSc, MSc, CEng, FIMarEST, Royal Navy Integrated electric propulsion (IEP) is an everyday reality as the power system solution for naval platforms, embracing recent advances in enabling technologies to deliver costeffective, survivable, power-dense solutions in a variety of applications. Founded on the Marine Engineering Development Strategy (MEDS) and supported by significant progress in the commercial marine sector, the defence community has embraced the potential of IEP and is now looking at more advanced integrated full electric propulsion (IFEP) solutions for future platforms. This paper follows on from the earlier series of ‘Hodge-Mattick’ electric warship papers and the ‘Newell-Young’ paper Beyond Electric Ship, and in doing so looks to put the United Kingdom Ministry of Defence’s (MoD) programmes and strategies into context, review the issues surrounding the introduction of IEP and provide an update on progress towards achieving the electric warship. AUTHORS’ BIOGRAPHIES Commander Graeme Little, Royal Navy, joined the Royal Navy in 1984 as a marine engineer officer. On completion of his basic training in 1985 he joined Royal Naval Engineering College (RNEC) Manadon to study for a first degree in marine engineering. Following successful professional training he joined HMS Birmingham in 1990 as the Deputy Marine Engineer Officer. He subsequently read for an MSc in electrical marine engineering at RNEC Manadon followed in 1994 by an appointment to the Ship Support Agency as the project officer responsible for electric propulsion systems. On promotion to Lieutenant Commander in 1996 he joined HMS Sutherland as the Marine Engineer Officer. Following Staff Course, he was promoted to Commander in 2000 and was appointed to the Warship Support Agency as the head of the Electrical Power and Propulsion Systems specialist group where he is now serving. Commander Stuart Young, Royal Navy, joined the Royal Navy in 1977 and completed undergraduate and post-graduate training at the Royal Naval Engineering College in Plymouth. He has undertaken a number of appointments at sea, including Marine Engineer Officer of HMS Norfolk, the Royal Navy’s first CODLAG frigate. Shore appointments have included project officer for the procurement of Warship Machinery Operator and Maintainer Trainers, lecturer at the Royal Naval Engineering College and Marine Engineering Liaison Officer with the United States Navy, based in Washington DC. He is currently the Electric Ship Programme Manager within the UK’s Defence Procurement Agency. No. B2 Electric warship new Commander John Newell, Royal Navy, joined the Royal Navy as an artificer apprentice in 1976 and joined BRNC Dartmouth on promotion in 1978. On completion of his degree at RNEC Manadon and initial training as a marine engineer he served as the Deputy Marine Engineer Officer in HMS Sirius. He subsequently took a MSc in electrical marine engineering and served in the MoD as the project officer for pollution control equipment. He then served as the Marine Engineer Officer in HMS Boxer before undertaking the French Staff Course in Paris. On return to the UK he spent 15 months with the Joint Planning Staff precursor to the Permanent Joint Headquarters (PJHQ) before becoming one of the appointers. He was promoted to Commander in 1997 and was appointed as the head of the Electrical Power Distribution and Propulsion Systems specialist group within the Ship Support Agency in March 1998. Commander Newell joined HMS Albion as Senior Naval Officer and Marine Engineer Officer in January 2001. INTRODUCTION I n recent years a variety of papers, seminars and conferences have sought to provide detail and promote discussion on the diverse range of issues that make up the electric warship concept. The same period has also seen a huge amount of progress in enabling technologies that have made integrated electric propulsion the system of choice for many new naval ships. This paper looks to review the MoD’s Marine Engineering Development Strategy (MEDS), examining its role within the framework of the Equipment Pillar of the Royal Naval Strategic 3 Journal of Marine Design and Operations 3 14/2/03, 11:47 am The electric warship VII - the reality Plan and the Smart Acquisition Initiative. Recent progress and successes will be reviewed along with a look at the enabling technologies and the ‘road map’ for managing the successful introduction of such technologies. The aim of the paper is to provide the wider naval marine community with clarity of the MoD’s programme and to invite debate for marine systems of the future. Perhaps by way of an overview it is worth reviewing the trends in power and propulsion systems in recent years, noting that the reality of electric propulsion was successfully introduced in 1920 in HMS Adventure and has seen widespread use in the submarine community. In the last decade of the 20th century, the Type 23 frigate demonstrated the benefits that an electric architecture can bring to bear with the hybrid power distribution and propulsion system known as Combined Diesel Electric and Gas (CODLAG). Building on the success of the Type 23 and the step change in technology driven by the commercial sector, electric propulsion is the reality as we enter the 21st century, with two Auxiliary Oilers (AO) and two Landing Platform Docks (LPD) shortly to enter service. Both classes have integrated electric propulsion and bring turnkey commercial solutions to satisfy a naval application. An artist’s impression of the LPD(R) is at Fig 1 together with an outline schematic of the power generation and propulsion system at Fig 2. Hard on the heels will be the replacement survey vessels, Type 45 destroyer and the Advanced Landing Ship Logistics, all embracing electric propulsion. The Type 45 solution is driven by the requirement for a power dense system with reduced whole life costs and challenging signature targets. The goal has been met by exploiting the commercial market and incorporating the United States’ integrated power system (IPS)-derived advanced induction motor (AIM) development and the WR21 ICR gas turbine. WHY ELECTRIC PROPULSION AND WHAT IS IT? Electric propulsion brings together efficiency, flexibility, survivability and, perhaps most importantly, reductions in cost of ownership. Captured simply, reduced numbers of prime movers, integrated systems, flexibility in layout and proven commercial precedent make it a credible solution to the requirement. Electric propulsion systems fall into three broad categories, namely hybrid, integrated (IEP) and integrated full (IFEP). The terms electric ship and electric warship are also used. They can be defined as follows: ● Hybrid - similar to the T23 frigate, where mechanical drive and electric drive systems are combined. ● IEP - where a common power source is utilised for both ship services and propulsion system, with the propulsion being purely electric. T45, AO and LPD(R) are examples. ● IFEP - takes the IEP concept further by incorporating advanced power electronics and energy storage into the architecture to give further cost and operational benefits. ● Electric ship - incorporates advanced prime movers and widespread electrification of auxiliaries into the IFEP architecture. ● Electric warship - where novel high-power weapons and sensors are incorporated to take advantage of the high system powers available. 4 Electric warship new Fig 3 looks to put the various system configurations into context. THE MARINE ENGINEERING DEVELOPMENT STRATEGY The current strategy The first Marine Engineering Development Strategy was endorsed in 1996. It aimed to achieve significant life cycle cost reductions, whilst meeting naval requirements, by exploiting world-wide industrial and commercial developments. Only if naval requirements could not be met would development of specific equipment be funded. It envisaged achieving this through the development and introduction of advanced-cycle gas turbines within an integrated full electric propulsion architecture and the electrification of auxiliaries. Development of industry partnering and international co-operation opportunities was encouraged. Much has been achieved. Since 1996 every major ship ordered for the Royal Navy has had an integrated electric propulsion system. The selection of IEP for the T45 means that life cycle cost benefits will now be achieved earlier than envisaged in 1996. The electric ship technology demonstrator is expected to start testing in spring 2002. This builds on the T45 concept and introduces new power conversion systems and advanced energy storage concepts to accrue further LCC benefits with high system integrity, particularly under damage or fault conditions. The Marine Engineering Development Programme (MEDP) is more than just electric ship, it covers all marine engineering technologies where MoD-funded work is needed to ensure that new technologies meet the requirements of future ships. Work either recently completed or currently on-going includes. ● Integrated waste management. ● Fire-fighting systems. ● Upper deck systems. ● Improved roll-stabilisation. ● Composite pressure vessels. ● Non-thermal plasma for Nox/particulate removal for diesel exhausts. ● Fuel cross-flow micro-filtration. ● Electrical actuation of hydrodynamic control surfaces. The Equipment Pillar The Marine Engineering Development Strategy does not exist in isolation and its pursuit over the next two to three years is a key element of the Equipment Pillar of the Royal Naval Strategic Plan. The Equipment Pillar outlines the Navy’s concerns regarding reliability, manning levels and through-life costs of current equipment and indicates how these could be improved by: ● Exploiting the concept of smart acquisition, closely aligning needs of through-life fighting power with specifiers and designers of equipment, focusing on ease of operation, maintenance, reliability and longevity, efficient manning and operating costs. ● Seeking innovative ways of monitoring and employing trends in technology, especially encouraging potential for non-warfighting technology to improve conduct of routine business. Journal of Marine Design and Operations 4 14/2/03, 11:47 am No. B2 The electric warship VII - the reality THE DRIVERS FOR CHANGE Technology Technical progress over the last five years has been far more rapid than envisaged in 1996. The step change to integrated power architectures, with all the ensuing benefits, has now been taken. Future development will be more evolutionary rather than revolutionary, and the benefits will be obtained through equipment, rather than system development. Development of the first ICR gas turbine (the WR21) has been completed and the engine system selected as the primary power source in the T45. Propulsion motor technology has allowed a power-dense advanced induction motor to be selected for the T45. Many manufacturers around the world are now developing permanent magnet motors of various topologies, and major breakthroughs have recently been achieved in superconducting motor technology. Semiconductor development continues unabated, as predicted, and further major advances are expected over the next few years. In many areas, commercial shipping has embraced future technologies earlier than navies; podded drives are an excellent example of an equipment now in widespread commercial use whilst still under assessment by the major navies. Fuel cell development, driven by automotive requirements, is progressing rapidly and to the extent that offthe-shelf solutions may be available within the foreseeable future. The choice of fuel, and its production, transportation and storage remains a major issue. As a result, further MoD-funded development — except to address shock or signature issues and other specific naval issues — is probably unnecessary but technology assessment in order to ascertain suitability is very important. This assessment is best conducted through the medium of the proposed Ministry-led Marine Engineering Centre of Excellence, utilising the available expertise to make strategic decisions that have the full backing of both MoD and industry. These achievements and a re-assessment of trends need to be reflected in any revised development strategy. Smart Acquisition - The new environment Smart Acquisition was introduced within the Ministry of Defence in 1999 and adds clarity to the acquisition process which was not available to the original strategy in 1996. It refined the concept of capability-led requirements and defined a new acquisition cycle, with clear decision points and therefore clear windows in which technologies needed to be sufficiently mature in order to be selected as candidate solutions. It defined incremental acquisition and technology insertion. More investment during the early project stages is encouraged is order to reduce risk, and close liaison with industry is regarded as essential. Although the original strategy anticipated many aspects of smart acquisition, the revised strategy needs to stress further how marine engineering development fits into the smart acquisition framework. Risk Risk management is a key tool in the acquisition process. In the assessment phase the user’s requirements will be developed into the more detailed system requirements. At each stage the risk associated with attaining the requirements will be assessed. The technology development and demonstration within the MEDP is a primary means of mitigating this risk. In addition the technology specialists within the proposed Marine Engineering Centre of Excellence (primarily the Marine Equipment Integrated Projects No. B2 Electric warship new teams within the UK’s Warship Support Agency) can advise on the risks associated with attaining the required capability. Thus a dialogue needs to be established between all the relevant stakeholders. Environmental Royal Navy ships are required to operate world-wide and must therefore comply with all applicable environmental legislation. Indeed, the long life-cycle of warships means that the design must anticipate future requirements. Commercial waste treatment technologies may be applicable to the naval requirement but would need to be made significantly more compact to facilitate installation on a surface warship or submarine. Furthermore, warships are required to stay at sea for far longer periods and shore support facilities for disposal of waste stored onboard may not be available. The goal of achieving a zero-emission warship, across the operational profile, remains. The environmental impact of ships throughout their life cycle must also be assessed and minimised. This requires examination of environmental impact during build, in-service maintenance and on disposal. Within the automotive industry the manufacturer’s responsibilities are clear cut and increasing. Similar trends can be expected in other fields, including marine. The future availability of fossil fuels must also be considered. Fossil fuels are predicted to remain in significant use for 40 years or more. However, cost will increase through this time frame and at some point it will become more cost-effective to use an alternative. The Royal Navy will be governed by commercial trends in this respect but needs to monitor trends closely and initiate development to ensure that warships can operate within the wider future fuel economy. Operational The operational capabilities required from future warships continue to develop. Specific capabilities of future power and auxiliary systems will, of course, vary but there will be a number of requirements that are generic. These include: ● Increasing power density, to minimise impact on overall ship design. ● Extended range, requiring highly efficient power systems. ● High availability. ● Low manning. ● Increased stealth and improved signature control. A STRATEGY FOR THE 21ST CENTURY Taking these factors into account, the following strategy for marine engineering development in support of the Royal Navy’s future capability requirements is proposed: ● Maintain awareness of technology and its capabilities by monitoring and assessing technology innovation and industrial capabilities and trends whilst maintaining the Electric Ship Programme Office as a focal point for the monitoring of industrial and commercial technology trends and utilising the Marine Engineering Centre of Excellence for the dissemination and assessment of applicable technologies. ● Identify the warship acquisition risks which can be mitigated through marine engineering system solutions. ● Develop mitigation strategies that satisfy the prime contractor (or potential prime contractor), satisfy the DEC 5 Journal of Marine Design and Operations 5 14/2/03, 11:47 am The electric warship VII - the reality and Warship IPT and are within our ability to fund and manage to completion within required time-scales. Build on success of original MEDS and the electric ship concept, with emphasis on facilitation of incremental acquisition and technology insertion through the use of open systems. Maintain focus on LCC reductions through equipment development within the IFEP architecture, technology trends, including fuel cells, podded drives and smart systems, and integration of high-power weapons and sensors. Take into account external influences, including increasing environmental legislation and trends in future fuels. Gain effective pull-through into service by ensuring that sufficient de-risking is undertaken, results of de-risking are available for those who need it (whilst protecting IPR) and industrial capability to deliver solutions is maintained, particularly through competition. Maximise value-for-money through international co-operation. ● ● ● ● ● Thus the aim of the Marine Engineering Development Strategy is: To achieve the required capability whilst generating ongoing reductions in life-cycle costs, through the leveraging of technology to mitigate the associated warship acquisition risks. THE ELECTRIC WARSHIP - EXPOSED As discussed previously, the all-electric ship embodies the IFEP concept with the additional enablers of advanced-cycle gas turbines and wider electrification of auxiliaries. It is however the IFEP architecture and possible solutions which offer the most exciting possibilities; in terms of operability, capability and reduced cost of ownership. The framework that is IFEP is founded on a number of enabling subsystems; high power generation, high power distribution, energy storage and conversion, low power distribution, automation systems and propulsion systems. Within these baseline sub-systems a bespoke architecture can be produced, an example of which is at Fig 4. The overall concept for the baseline architecture is one of flexibility of design solution with a range of technologies able to meet the demands of the system. It is these technologies which have been the focus of MEDP and the marine engineering community and will form the basis of the next section. Before reviewing the technologies it is worth highlighting the importance of a generic baseline solution in the context of understanding and maximising the synergy between various platform architectures; a key theme in realising the potential of IFEP. Given a generic baseline allows system level design assessments to be made together with supporting a technology development focus. It must, however, be remembered that at the system and sub-system level a number of themes need to be understood if the system is to be optimised effectively, these include: hullform; power system architecture; energy storage; operability; user demands; and, field effects. Hullform. The hullform solution drives the IFEP solution, primarily from a power density perspective but with support- 6 Electric warship new ing considerations of signature, survivability and shock. The spectrum of hullforms is bounded by the larger carrier-based hullform (steel is cheap and air is free solution - although this is not an entirely valid statement) and the exacting requirements of a submarine platform. The middle ground occupied by the destroyer and frigate, whether multi- or monohull, completes the picture. This is not the entire picture as IFEP is also relevant to smaller vessels, but the requirements that set the main contenders apart is installed power which is significantly greater than those anticipated for minor war vessels. The huge benefit of the IFEP solution is that premised on the currently-accepted range of hullforms possible for warships driven by naval architecture and weapon and sensor solutions, the IFEP concept can be designed to fit. This will not go unchallenged as the required bounds of power density from both gravimetric and volumetric perspectives are placed under considerable pressure and the demands for increases in both are made. Power system architecture. At the heart of the ‘power station’ is the system architecture, on which the solution will hang; in the case of IFEP a number of options are still presented as viable. The traditional architecture of a ring distribution with centralised switchboards and electrical distribution centres (EDCs) offers, in most part, a good baseline solution against which other ‘more novel’ solutions can be gauged. Novel approaches to EDC architectures provide inherent flexibility and system redundancy with further enhancement possible using change-over switches and uninterruptible power supplies (UPS). Looking at a slightly more novel approach leads us to the much courted ‘zonal concept’, whereby the distribution system, together with all the supporting systems, is zoned with at least two methods of supplying energy within a zone. Central to this architecture is a zonal power supply unit (ZPSU) and zonal energy storage unit (ZESU). Extremely attractive, the zonal concept infers increased survivability and operability but not without an element of technology and integration risk; a decision that will be informed by the MoD’s energy storage philosophy. Energy storage. A wide range of technologies exist to support a profusion of possible requirements; indeed it is this that supports the need for a platform, if not pan-platform, energy storage philosophy. The requirements range from the equipmentbased UPS, commonly found in weapons and sensors, through sub-system requirements such as steering, to the most onerous demands of propulsive ride-through, more of which later. Again, this issue is far from concluded and cannot be viewed in isolation, as together with architecture and the ZPSU/ZESU debate, this needs a much broader focus. Assessment of technologies will be based on demonstration in the ESTD and the MoD’s energy storage strategy. Operability. Often described as the panacea for the platform systems, IFEP and its variants, provides a huge step forward in flexibility of operation and system survivability, to name but two. However, a note of caution - realising the full potential of the plant can only be achieved if it is fully understood and not, as some protagonists suggest, left to ‘come out in the wash’ as more is understood and experience gained. Operability is a key strand and must be understood at the earliest point in the design process. Central to the operability debate is the issue of single generator Journal of Marine Design and Operations 6 14/2/03, 11:47 am No. B2 The electric warship VII - the reality operation (SGO), a subject which has attracted a huge amount of interest, notably from the operating community. The technical community has not helped themselves on this one as the term SGO conjures up all sorts of issues in the minds of the operators. However they have now been articulated clearly and it has been demonstrated, with some clarity, that SGO does not result in reduced system availability when balanced against the ship handling constraints, operational state and provision of energy storage. The concept of minimum generator operation (MGO) embraces SGO fully and is perhaps a far more relevant description of the operating procedures. User demands. As wider electrification becomes a reality the demands on the power system increase, this is best illustrated as we focus on the possible next generation of weapons and sensors, or indeed those of aircraft launch and recovery. The user demands need to be understood from the outset if the design solution is to be flexible enough to accommodate technology insertion and, indeed, the capacity to support demands from the outset. Not just confined to weapon systems and sensors, the implication of increased electrification of auxiliary systems needs to be understood and quantified. Field effects. Subject to much recent focus for both inservice and newbuild projects, the effects of electromagnetic fields have been raised as an area of concern for hybrid and IEP installations, from signature and safety perspectives. Whilst the issue cannot be dismissed out of hand it equally must not be made too much of, and a number of approaches are in hand to manage this effectively. From a safety perspective, measurements are being taken on current classes and it is planned to carry out similar trials onboard LPD(R) and AO as they enter service. Any potential further problems can be reduced significantly by up front design and focus on shielding and installation. The issue of signatures is being assessed but cannot be discussed in this paper. The generic baseline and system framework allows for a more holistic approach to system and platform design, primarily from a technology insertion perspective - an important point as the platform visions of the future begin to move into and out of focus! Outwith these system design issues, it must be recognised that a range of enabling technologies are central to IFEP, a number of which, together with the review of risks are outlined in the next section. Framing the technology As mentioned previously, the key thread must be understanding and managing the risk, both from equipment and platform perspectives. To articulate the technical risk requires a formal risk review across the enabling technologies, the outcome of which will provide generic and platform-specific risk assessments across the technology, thereby framing the technology issues and underpinning future development. Fig 5 captures the high-level technology enablers within which the analysis will be undertaken. Before reviewing the technologies it is worth reiterating the central themes for MEDS and AES; power density, risk, whole-life costs, efficiency, environment and survivability. These criteria frame the focus on technology of power generation, high power distribution, energy storage and distribution, and low power distribution. Power generation, Gas turbines are established as the No. B2 Electric warship new power-dense, efficient and environmentally-sound solution to the problem of installed power. Coupled with conventional generator technologies, the high power generation capability, vested currently in the WR21 GTA and the ACL GTA looks to provide the surface platforms with the bulk of their power well into the late part of the 21st century. Technology focus for the future is reliant on established construction techniques with possible trends to super-conducting and permanent magnet technology. Before moving away from generation it is worthy of note to raise the issue of fuel cells. The jury is still out and the MoD focus has, at best, until recently been uncoordinated. Whilst the short term possibilities are limited, advances in fuel storage and cell technology will undoubtedly make fuel cells a future attractive low power energy source. Industry is developing the fuel cell as a clean and efficient source of energy. Future work may concentrate on the use of alternative fuels (eg methanol or hydrogen) and its safe storage and handling in a shipboard environment. This work will be driven by the need to identify an alternative to conventional fossil fuels by the middle of the 21st century. High power distribution, The ac/dc debate is still far from resolved, indeed which way we fall will primarily be driven by the industrial focus and the level of risk. The ac/dc subject is as emotive as ever and the decision point is fast approaching. Switchgear and cables cannot be readily divorced from this debate and will play a key role in the solution. Switchgear rated for the perceived IFEP architectures is on the limits of its capability and a number of options such as the hybrid switch and novel breakers are being assessed for their applicability to marine systems. Related to this are the issues of switchboard design and a possible trend away from centralised to, perhaps, distributed switching and thereafter, perhaps, embedded protection - one step at a time possibly, but this is an area that we must progress as the exacting protection and switching requirements increase. The last issue within this area is that of cables, and whilst we are confident that the issues of EM fields, buildability and shock can be managed with existing technology, we need to look at how we might embrace busbars or more novel systems for the future. At present all such systems are prohibitively expensive for the gains in ease of build and similar. Energy storage and conversion, Noting the profusion of possible solutions to meet the varied demands on energy storage, it is difficult to progress any one technology without having articulated the architecture and energy storage philosophy. In general terms, the industrial base is making the enabling technology available, it is how we grasp this technology for the naval marine environment that presents the greatest challenge. Returning briefly to ESTD, flywheel technology and a regenerative fuel cell are being assessed for power system suitability at the zonal and bulk levels of power. Low power distribution, Not wishing to open the ac/dc debate or indeed repeat the high-power discussion, this section is best left looked at from a system perspective. System issues are very much architecture-dependent and we must be aware of the importance of the transversal issue with the high-power system. Current solutions include transformed supplies but the technology is ‘here and now’ for bi-directional static power converters and perhaps presents a viable solution for platform incremental acquisition. 7 Journal of Marine Design and Operations 7 14/2/03, 11:47 am The electric warship VII - the reality SWITCHGEAR - THE DC CHALLENGE - A FOCUS Not a focus for previous electric warship papers, switchgear is however worthy of mention as a key enabling technology, particularly for a potential dc distribution system where the interruption of fault currents is more onerous than for comparable ac systems. The reason for this is simply that an ac circuit breaker can interrupt at or around current zero whereas a dc breaker must create a current zero either by forcing the current to zero by controlling the arc voltage or, creating a current zero by commutating the current around an opening contact. In addition the dc circuit breaker design is driven by the arc energy that can be dissipated, mindful that a dc breaker will be much larger than its equivalent rated ac counterpart, and the need to minimise the rise of fault current. The technology solutions to these problems are high-speed air circuit breakers and hybrid breakers. Air circuit breakers. The mechanism during a fault is the control of the arc within the arc chute whereby an increased resistance of an established arc reduces the circuit current so that the arc cannot be maintained by the circuit voltage and the current is reduced to zero. The control of the arc is achieved by natural electromagnetic and thermal forces assisted by a magnetic field; technology which is well established. Currently available at up to 3kV, 8kA with a breaking capacity of 60kA, the move to voltages in excess of 5.6kV for the electric warship application will need development, but the more onerous rating is containable within current technology. Hybrid circuit breakers. Combining a fast mechanical switch and power electronics, hybrid circuit breakers utilise either zero current or zero voltage switching, both of which are illustrated at Fig 6 and described below. Zero current switching. The mechanical switch carries the load current until a short circuit is detected whereby the switch opens, the power electronic switch is then triggered and a resonant current is established in the L-C network with a reverse current flow at the mechanical switch. The voltage across the capacitor rises and the varistor begins to conduct, which dissipates the inductive energy within the circuit and the current drops to zero. Zero voltage switching. The mechanical and power electronic switches are triggered simultaneously but the time constants of the mechanical switch allows a parallel conducting path to be established within the power electronics. As the mechanical switch opens, the arc voltage shifts the current flow fully to the parallel power electronics path. The commutation provided by the power electronics then extinguishes the arc and with the electronic switch turned off with the mechanical switch open, the remaining energy is dissipated within the varistor. Issues. The hybrid breakers provide improved current limiting overfast-acting air circuit breakers with a significant reduction, almost elimination, of arcing. The hybrid variants are very similar but the trade-off is between the bulky resonant circuit required in the zero current switch compared to the need for switchgear development. The technology has been implemented in prototype designs but no production arrangements have been taken forward. In a marine application the constraints are the mechanical and power electronic switches, with current limiting only achievable at the planned ratings if the mechanical opening force and time to open are in the order of 35kN and 1.6 milliseconds1. Propulsion systems. A huge subject area, broadly captured 8 Electric warship new by the propulsion motor (PM) system and the transmission/ propulsor system. Comprising a drive and motor, power density and signature direct these technologies which have seen a huge amount of industrial and government effort in recent years. The advanced induction motor (AIM) is currently the preferred solution, and is shown at Fig 7, but the industry pack of chasing technologies is focused on taking PM system developments to meet the demands of pods, low displacement and novel hullform applications. Whether it will be a derivative of the AIM, a permanent magnet machine or indeed a super-conducting machine, is a long way from being resolved, indeed the MoD is actively pursuing a PM strategy to assess where best to focus its efforts and, perhaps more importantly, its money! Again industry is actively pursuing and solving the technical issues surrounding the novel PM technologies and this looks to be an area of significant industry-led work in the near term. In support of this, power electronic devices and system developments continue apace and a number of maturing PM system combinations now feature advanced pulsed width modulated (PWM) converters. The three technology areas - conventional, permanent magnet and superconducting - all offer high power density (volumetric and gravimetric) efficient solutions. Whilst the technologies are all at varying stages of maturity, the key is that they would all seem to have a role to play in the next generation of warships, albeit not all technologies are suited to all applications. Fig 8 looks to provide a snapshot of motor technology to put each of the contender technologies into perspective. Of course Fig 8 is only half of the story, particularly the power densities, and the motor technologies cannot be compared in isolation; any longer term assessment will need to include the converter and auxiliaries and this is the subject of the MoD’s propulsion motor strategy. Platform management systems (PMS). These have long been the key to achieving manpower savings, and work is underway on how to specify systems, in performance requirements terms, which support the operating and manning philosophies of the future navy. This work will be further enhanced by developments in smart systems, which will be able to identify failures and damage, and reconfigure themselves automatically without operator intervention. DELIVERING CAPABILITY Returning to the theme of strategy and how this and the technology can be embraced and engaged as platform system solutions, Fig 9 puts forward a roadmap for technology within the framework of capability, requirement and timescales. These bounds are extremely pertinent to the longer term focus of the electric warship concept and system design and technology integration for future platforms. The key thread throughout is risk and how it is identified, owned and managed by the various stakeholders; notably the MoD, the prime contractors’ offices (PCOs), system integrators and equipment suppliers the balance of which needs to be developed if the capability is to be delivered. Mindful of the common thread of risk, the roadmap looks to capture the main themes and how the stakeholders need to be integrated and relevant to ensure that the obvious synergy is exploited. Within the bounds of the roadmap, here are a few thoughts. Procurement of future platforms is now focused on delivering capability by the most cost-effective means, with the key themes being that of ‘requirements engineering’ and risk Journal of Marine Design and Operations 8 14/2/03, 11:47 am No. B2 The electric warship VII - the reality aversion - basically PCOs are tasked to deliver a capability to time and cost, and they are not paid enough to embrace additional risk. It is in the management of the dichotomy of risk aversion and the introduction of technology in which the MoD can be most effective with the combination of MEDP, partnerships with industry and collaboration. It is the MoD’s informed customer status and ability to identify and mitigate risk that underpins much of the Smart Procurement Initiative - notably the balance of COTs, development of commercial solutions and bespoke naval development. How then against such a background can it be ensured that the work being undertaken within the MEDP programme is not nugatory and that our future ships fully embrace IFEP? The answer is, in principle, easy to identify; in practice it is much harder to implement. Fundamentally it is imperative that the risks are captured from technical, programme and platform perspectives so that a coherent risk register is maintained - this functionality is vested with the Electric Ship Programme Office, thereafter the key is how to translate the risk process into design, development and technology insertion. In making this transition it is essential that PCOs and the wider industrial base are ‘onboard’. The drivers here, in addition to those of risk management, are the need to reduce cost of ownership with effective support packages, the emphasis towards commercial off the shelf equipments, and the trend away from naval standards towards best practice, wherever that may be vested. The AO, LPD(R) and Type 45 have been provided as almost turnkey solutions, thereby minimising risk and therefore cost. As system and equipment trends move away from the commercial sector, the overriding issue must be ‘partnership’ and this is the area in which the MoD can bring a huge amount of experience and knowledge to bear. A key focus for technology insertion and de-risking is the Electric Ship Technology Demonstrator (ESTD). ELECTRIC SHIP TECHNOLOGY DEMONSTRATOR The ESTD is a joint programme between the UK and France which looks to de-risk IFEP technology so that it becomes an attractive option for future ship propulsion system prime contractors. The schematic of ESTD is at Fig 10. Broadly speaking it includes a half ship set of equipment with representative power generation and distribution systems linked by two static power converters. The 20 MW propulsion motor drives a dynamic fourquadrant load, enabling the system to be demonstrated throughout the complete operating envelope. The zonal distribution system, and inclusion of both zonal and bulk energy storage complete the picture. The supporting aims of ESTD are: ● To identify and de-risk IFEP system integration issues, including system stability, fault identification and protection and harmonic distortion levels. ● To validate equipment and system software models to reduce or eliminate need for shore testing of future war ship power/propulsion systems. ● To generate ILS data. ● To assess signature issues. ● To inform future platform baseline designs and provide supporting evidence for technology pull-through. ● To support the development of power and propulsion requirements for future warships. ● Inclusion of some T45-specific equipment will also allow No. B2 Electric warship new the facility to be used for shore integration testing (SIT) for Type 45 systems once the majority of ESTD testing has been completed. One of the key issues for ESTD is how it will be utilised beyond the current testing programme to manage technology insertion and incremental system design; this presents a unique opportunity for the wider naval power system stakeholders to be engaged in this important programme. THE REALITY - AN INSIDE VIEW This section will look at the all electric warship from the reality of a practitioner’s perspective with the emphasis on operating challenges related in the most part to LPD(R) experiences but equally applicable to the wider concept. The single line diagram at Fig 2 should be used to support references to the LPD(R) system. There are several key features that will make electrical propulsion a success or a failure in warships. We must of course adopt a safe system of work but with many examples available from industry, the merchant marine and of course the Royal Fleet Auxiliary (RFA), this is a well-trodden path. More crucially we must differentiate between an all electric ship and an all electric warship in that we take these latter platforms into operational theatres where we can expect some damage, even if minor, and we cannot afford to take away propulsion or electrical services from the command. This leads to a focus on operation, fire-fighting and damage control, equipment design, onboard organisation and training, all of which are discussed below: Safe system of work and compartment access A safe system of work to include Health and Safety and other statutory requirements is essential if the system is to be operated safely, noting the requirement to have established procedures for maintenance and operation by naval and civilian personnel. Wherever possible standard RN practice has been adopted but high voltage requires additional precautions including hazard markings for compartments, hazard signage, restricted access procedures and CCTV monitoring of all compartments designated HV. Routines are required both by contractors and visitors with restricted access regulations controlled by either a ‘day pass’ or ‘contractors pass’. Contractors requiring access to HV compartments will need to be briefed on the hazards and will require a limitation of access prior to unescorted access/work in these spaces. None of these issues is insurmountable but they need to feature in the baseline design for an IFEP solution as the presence of HV will limit access and require control procedures. System operation and manning of HV spaces The HV system will be operated via the platform management system (PMS). For the LPD(R) system, the normal practice will be to run continuously in parallel, de-isolated with the minimum number of generators required (minimum generator operation (MGO) leading to single generator operation (SGO)) at State 3. At State 1, all generators may be required but the system will remain de-isolated. Because of the late change to electric propulsion during the design phase of the LPD contract, some HV equipment built to IP23 is located in main machinery spaces. This means that the spaces concerned need to be disconnected from the live system before any water-based extinguishers can be used to tackle a fire 9 Journal of Marine Design and Operations 9 14/2/03, 11:47 am The electric warship VII - the reality or before any attempt is made to control a flood. System disconnection procedures for the isolation of the HV system in the event of fire/floods need careful consideration to ensure that the appropriate action is taken without endangering personnel and maximising availability of the propulsion system to the command. Likewise, careful thought must be given when operating in SGO mode to ensure that a total electrical failure (TLF) does not occur if the affected compartment contains the only running prime mover. It is also possible to lose main motor excitation if isolations are carried out in the incorrect sequence. A series of hard-wired trips allow rapid disconnection of the HV system. The PMS system consists of a Pentium-based PC system communicating via a dual redundant ethernet with batterybacked power supplies. This reversionary power source is located in the forward switchboard and could perhaps be split into zoned power supplies to make the system more resilient to action damage in upgrades or future platforms. Manning of machinery spaces at State 1 should not be unduly affected by the possible hazards of exposure to HV (we have for a long time manned magazines), but should be primarily driven by the operational gains of manning secondary or local machinery control positions as well as the ability to carry out immediate first aid action. This approach must also be balanced against the availability of manpower and the increased risk of exposure to injury from action damage within a large machinery space. Hence HV compartments will not be manned at State 3 but will be at State 1. The mobile party (the cavalry!) needs to be best located to cover all main machinery spaces; particularly any unmanned at State 1. They need good communications and a high degree of individual protection. Fire-fighting and damage control The recommended fire-fighting approach is to always maintain a continuous aggressive attack using appropriate first aid fire-fighting appliances. Should high voltage equipment within the compartment be correctly protected by correctly IP-rated enclosures, then AFFF and HPSW hoses may be used without restriction, although the inherent dangers of unprotected lower voltage systems must also be taken into account. Should the compartment become untenable it should be evacuated and closed down prior to using the fixed suppression system. The process of closing down and isolating the compartment should be initiated as early as reasonably possible with the available manpower. How then to first aid fire-fight in HV compartments? The suggested solution is to replace AFFF extinguishers and hose reels with portable CO2 and dry powder extinguishers to maintain the aggressive attack without isolating equipment, although compartment isolation prior to initial attack on the fire could also be considered. Kill Cards will indicate HV compartments and also compartments through which HV cables pass, and how to isolate power to these cables. There is however no need to isolate spaces prior to CO2 drench although direct injection of CO2 onto HV equipment is not supported. Electrical isolations for fire-fighting and the use of foam blankets will depend on the IP rating of high voltage equipment which should be a minimum of IP55 for a compartment below the waterline and/or with fluid systems running through it (low voltage systems must also be considered). The ability to isolate equipment from outside the compartment is essential and there should be a 10 Electric warship new clear indication at the compartment entrance, and possibly on the equipment, as to whether high voltage equipment is still live. Normal re-entry into any space requires the fire-fighting team to be protected behind a water wall. Whilst this may remain sensible during peacetime operations, it probably is not if we wish to protect the HV system from water ingress and maintain propulsion to the command at State 1. Fig 11 summarises the range of fire and flood scenarios. Equipment design The selection of IP ratings for equipment must take into due consideration the siting and possible consequences of fire-fighting and flooding taking place in the immediate vicinity. We cannot afford to evacuate a space and abandon the prime movers or other equipment contained within. The number of systems adjacent to HV equipment should be minimised and, where unavoidable, pipework should be continuous. CO2 injection ports on HV equipment will not be fitted; rather compartment or equipment fire suppression systems should be installed. Onboard organisation and qualifications The organisation to be employed for the ‘day to day’ operation/maintenance of the HV system is shown at Fig 12. Training There is the requirement for the provision of a training/joining video for the education of the ship’s company not involved in the day-to-day working of HV equipment. This video may also have to be made available to potential contractors to also make them aware of the potential hazards. Training organisations such as FOST will be required to input proposed training scenarios and also they will have to be informed of any limitations that HV may place on proposed training (eg charged hoses, training smoke, etc). FOST currently use exercise smoke during operational sea training and this may have an impact on HV installations. High voltage policy The preceding paragraphs highlight a number of themes for high voltage systems, all of which will be captured in the MLS1sponsored HV Policy Document. The document looks to provide the wider naval marine power system community with guidance on the specification, design, installation, test and operation of HV power systems in warships together with the wider issues of training and infrastructure. In the longer term it is hoped to incorporate the policy guidelines within the requirements documentation for future platforms, notably on all safety-related issues but in the near term the plan is to issue the document for ‘buy in’ from the wider naval power system community. THE CHALLENGES Notwithstanding the specific technical issues mentioned, a number of other challenges also face the effective implementation of IFEP. Whilst not exhaustive, the Top ‘X’ challenges includes integration, electrical standards, equipment strategies, maintaining innovation whilst minimising risk, embracing automation and system analysis. The following takes each of these issues in turn. Integration. The integration of the complex IFEP architecture is a significant challenge to system and equipment designers and an area which needs the requisite focus at all stages of the design process. Integration issues include system stability, operability, Journal of Marine Design and Operations 10 14/2/03, 11:47 am No. B2 The electric warship VII - the reality compatibility - notably EMC, physical issues and system transversals. Experience has shown that the transversals issue is the most difficult to manage as boundaries are established between systems and sub-systems; the management of which needs system level co-ordination. On the theme of integration, the physical integration and buildability of solutions is extremely important and must be a significant focus during the design process. Electrical standards. Existing power system standards are not sufficiently robust to support IFEP and IEP architectures. Fundamentally, standards reflect conventional systems and are not sufficiently flexible to be adapted to suit novel systems. In support of this a review is being undertaken to propose a policy for IEP and IFEP systems covering issues as diverse as power system standards, safety, Design constraints and working practices. This is even more relevant in view of the high voltage implications. The MoD’s HV Policy Document will look to provide the framework for naval marine power system standards. Equipment strategies. Building on the themes of risk, the overarching MEDS and its implementation through the centre of marine engineering excellence, equipment and system strategies are essential to the electric warship aspirations. A number of strategies are being written which look to draw together the requirements, platform risks, timescales and industry focus to produce the supporting justification for equipment development, the outcome of which will inform development and the wider stakeholding community. Within DOpsE, a Directorate of the Warship Support Agency, system strategies are being produced to support medium (10 year) and long (25 year) term visions, which look to provide a coherent focus across the marine engineering community embracing the MEDP and elements of both the Corporate (CRP) and Applied (ARP) Research Programmes. Innovation. Innovation will always be constrained by risk and the desire to minimise any impact on the performance, cost and acquisition timescales of a future warship. However, without innovation, technology will stagnate and the future Royal Navy will face increasing support costs and degrading performance and capability compared to other, more adventurous, navies. A balance must therefore be struck. This can be achieved through establishing a thorough appreciation of future technologies and their assessment, through the MEDP and the expert eye of the Marine Engineering Centre of Excellence. The risks associated with innovation can then be fully quantified, and effective, focused risk-mitigation put in place. As a result the likelihood of the pull-through of innovative technologies into service by the warship prime contractor will be enhanced. Wider strategy. The marine engineering aspects are focused, but the lack of coherent strategies or, in some cases, coherency between strategies in the wider naval service creates difficulties. Notably, the lack of a weapon engineering equivalent to MEDS remains a concern and it is imperative that the future requirements of combat systems are identified as a priority to ensure that the platform solution can meet the demands, primarily in terms of power requirements and possible requirements for pulsed energy. Manning, support and similar strategies do, however, exist but it is essential that coherency is maintained between them. Automation. Central to the platform system solution, the platform management system (PMS) and its derivatives provide the operability and functionality of the system - the main concern however is that of integration. PMS needs to be embraced at the outset and become an integral part of the design solution. Often seen as the ‘cure all’ for system functionality and integration, it is important that it is not left to pick up the design deficiencies from the system and equipment integration. System analysis. As the focus moves away from platform shore test facilities, a function of cost and time, the emphasis on alternative mechanisms to assess system and equipment performance has come to the fore. The spectrum of activities in support of the analysis is bounded by full scale test and simulation balanced with prototyping and equipment tests. The trend towards simulation is worthy of note, with both MoD and industry embracing it to balance equipment and system development. The strength of this approach is flexibility and cost, and the ability to model at component, equipment, sub-system and system levels. Already naval marine power system modelling has produced a modelling blockset to assess system and sub-system issues in a ‘fuel to thrust’ approach, the outline schematic for which is at Fig 13. The functionality of the models allows assessment of dynamic performance, system transients, external impacts and bounds of operation. Validation of models remains a key theme along with the issue of models containing proprietary information, which must be resolved if the goals are to be realised. The simulation vision is to maintain a database of models for all power systems and equipment, with all new systems and equipment being delivered with a validated model - wishful thinking, perhaps, but essential if we are to realise the full potential of simulation. SUMMARY The last year has seen a huge amount of activity in both the electric ship and electric warship arenas, notably with the reality of the electric warship and the coming of age of the integrated electric propulsion concept in the guise of LPD(R) and Type 45. In support of these vessels and within the framework of smart acquisition, the marine engineering development plan has sought to maintain momentum and relevance with a number of notable successes, primarily that of ESTD. The emphasis is now, as ever, on cost-effective capability for the marine engineering solution and it is hoped that this paper has gone some way to demonstrate how the MoD is looking to take this forward in partnership with industry with the focus very much towards incremental acquisition and technology insertion. REFERENCES 1.EA Technology Report 5435, HV DC Switchgear Feasibility Study dated 3 Jul 01. © Controller, Her Majesty’s Stationery Office, London 2001. © British Crown Copyright 2001/MoD. Published with the permission of the Controller of Her Britannic Majesty’s Stationery Office. No. B2 Electric warship new 11 Journal of Marine Design and Operations 11 14/2/03, 11:47 am The electric warship VII - the reality Fig 1: The reality of the electric ship Fig 3: The usual suspects Fig 4: Baseline architecture or marker in the sand 12 Electric warship new Journal of Marine Design and Operations 12 14/2/03, 11:47 am No. B2 The electric warship VII - the reality Fig 2: LPD(R); the single line diagram No. B2 Electric warship new 13 Journal of Marine Design and Operations 13 14/2/03, 11:47 am The electric warship VII - the reality Fig 5: Framing the technology Fig 6: The hybrid switch schematic Fig 7: The advanced induction motor 14 Electric warship new Journal of Marine Design and Operations 14 14/2/03, 11:47 am No. B2 The electric warship VII - the reality Fig 8: Motor development compared Fig 9: A technology roadmap Fig 10: ESTD schematic No. B2 Electric warship new 15 Journal of Marine Design and Operations 15 14/2/03, 11:47 am The electric warship VII - the reality Fig 11: Fire and flood scenarios and responses PERSONNEL TRAINING Authorising Authority (FOSF ashore) Authorising Engineer (MEO-May have nominated deputies) Authorised Persons Competent Person (CP) HV Aware (Remainder of ship's company) MEOOW1 HVA MCQ +AP+local assessment AP+local assessment Video + detailed briefing Video + briefing As CP Fig 12: Onboard organisation Fig 13: IEP Model; the software realisation 16 Electric warship new Journal of Marine Design and Operations 16 14/2/03, 11:47 am No. B2