Uninterruptible and Back-up Power: Fuel Cells U Benz, D Busche, and D Lutterbeck, P21 GmbH, Brunnthal, Germany & 2009 Elsevier B.V All rights reserved Introduction Backup Power Systems for Mobile Telecommunications Telecommunication networks are a major user of backup powering systems (also termed uninterruptible power systems (UPS)) and they serve as the primary example of a fuel cell (FC) application in this article Mobile or wireless networks are often the primary source of telecommunications especially in emerging markets and developing countries where fixed line networks have not been extensively built Customers expect to continue to use their mobile phones, even when the power grid fails In extreme cases, need to be reached and need to continue with their communication The mobile network is based on a matrix of base transceiver stations (BTSs) In general, the electrical energy is provided by the electric power grid In a BTS site, the 230 VAC (volts alternating current) power is generally inverted into À 48 VDC (volts direct current) power, which is used to power the radio equipment In the case of a blackout, batteries and/or diesel generators traditionally step in to ensure continuous operation Today, the mobile network operators (MNOs) rely mainly on lead–acid batteries as the emergency power source These are accumulators that are maintained at full capacity by applying an adequate charge current during normal grid operation In the case of a (temporary) loss of the electrical power grid, the voltage level in the BTS falls below the open-circuit voltage of the battery and the batteries take over the power supply as the lead–acid batteries are discharged As soon as the electrical grid is reestablished, the batteries are recharged until they reach their full capacity, or until the grid fails once more Although batteries are the most established provider of backup power, they suffer from a number of drawbacks: Long unpredictable outage • hours andgrid loss) require largeperiods (e.g., several of battery banks The • size of the banks has to be designed for the most probable worst case The weight of the batteries can be a problem especially on rooftop sites and the costs increase with the size of the battery bank Continuous monitoring of the condition of lead–acid batteries, and therefore their available energy capacity, is impractical The available capacity falls over time and with the number of discharge cycles, especially at • • high depths of discharge (DoDs) Therefore, the operator does not know how much backup power is available at the sites Lead waste is highly toxic and it is not guaranteed that the recycling is up to the required standard Batteries suffer if they are operated at temperatures above 25 1C Consequently, the BTSs are actively cooled, especially in hot regions This is a major contributor to energy consumption and operation costs For very long backup times and for remote off-grid operation, diesel generators are generally used These diesel generators represent a very significant investment and operational cost for both fuel and maintenance and, in addition, there are problems with reliability Diesel generators contribute to air pollution and have a large carbon footprint Backup Power – Early Market for ProtonExchange Membrane Fuel Cells? Fuel cells could offer an alternative power backup to both batteries and diesel generators They are compact and lightweight and can be refueled, thereby offering extended backup power for long periods of time An FC is a highly efficient, environmentally friendly, relatively simple, and high-potential technology that generates electricity by electrochemically combining hydrogen and oxygen It is commercially available for backup power applications It has no moving parts such as an internal combustion engine, and therefore does not vibrate and produces only minimal noise The only emissions are water It does not require fossil fuels and has greater fuel-to-electrical energy efficiency than any other technology The basic principle of a proton-exchange membrane fuel cell (PEMFC) is shown in Figure Despite their high potential with respect to efficiency and environmental friendliness, until recently and for most of the broad field of potential applications, FCs showed significant disadvantages compared to established competitive technologies, such as • higher investment costs, • limited lifetime, and and a high fuel price • poor fuel availability Owing to the most recent development efforts spent on FC systems for backup power applications, the costs of FCs and FC systems have reached a commercially viable 135 136 Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells level for this application, even in moderate production volumes (Figures and 3) Backup power application requires an accumulated operational lifetime of o2000 h, which fits very well the − Direct current + lifetime expectation of today’s FCs Modern FCs not consume hydrogen when they are in standby mode and all of the components are idle When the grid fails, the system instantaneously kicks in and delivers power Industrial hydrogen has been available in various industries for more than 100 years Today, the gas industry has moved and is actively cooperating with FC companies in order to establish hydrogen as a major energy carrier This includes hydrogen distribution, as well as storage and availability at acceptable prices In summary, FCs offer a potentially attractive backup power solution, especially for the telecommunications industry, where extended run times are desired, which batteries cannot easily provide, and where diesel generators are considered to be expensive and less user friendly Target Market for Fuel Cells Main Focus – Mobile Network Operators Anode Proton-exchange membrane Cathode Figure Fuel cell (FC) principle Figure Fuel cell (FC) system Premion T 3000, 3kW 136 Mobile network operators are highly dependent on reliable electrical power to run their base stations They are the early adopters of new backup power technologies as power is critical and the infrastructure is distributed The potential market is vast There are B400 000 base stations in the European Union (EU) alone, and it is expected that 000 000 new Base transceiver systems will be set up in India The power requirements of the sites are similar – depending on the size, between and kW Not all of the BTS sites are ideally suited for the implementation of FCs Not all the regions have the same demand for backup power Not all the sites in a network have the same demand for backup power The motivation for the implementation also differs owing to different market characteristics and influencing factors Network expansion and BTS growth Mobile network operators that are in a growth/upgrade phase of their BTS networks are driven by Figure Fuel cell (FC) stack Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells building activities in • network stabilization activities emerging markets, and network growing regions, • 3G (third-generation mobile inphone standard and • technology) system (universal mobile telecommunications system (UMTS)) evolution, which is currently dominating network expansion activities in Western Europe Special requirements on reliability Base transceiver system sites require highly • and compact source of backup powerasupply reliable Environmental friendliness Mobile network operators are considering a redesign of network in order to operate their network in a more environmentally friendly way or in order to use higher call-volume handling technologies Mobile an • in beingnetwork operators with andincreasing interest perceived as ‘green’ consciously con- • sidering alternatives to traditional batteries and diesel generators, Mobile network operators increasingly concerned about prime energy usage/costs and subsequent carbon dioxide release into the environment Hence, it is believed that there is an urgent need for backup power solutions that exceed the present requirements of the BTS infrastructure, which currently utilizes existing battery solutions Market Characteristics for Backup Power Special marketplace conditions favoring a fuel cell solution Backup power can be compared to an insurance policy If the power never fails, no backup power would be required If the impact of a power outage is negligible, a form of backup would also not be needed The longer the power outages and/or the higher the impact of a blackout, the more reliable the backup power needs to be and the more effort the customer will make in improving the backup powering system In contrast to insurance policies, there are other factors that influence the backup power choice: Base • wheretransceiverasystem networks operating in regions there is higher probability of occurrence of • • power failures in terms of number of times and duration Base transceiver system networks that have experienced ongoing disappointment in the performance of traditional batteries when called upon for delivery of backup power supply Base transceiver system networks where traditional backup systems such as batteries and diesel generators are not the preferred options for reasons such as noise 137 pollution, air pollution, carbon dioxide generation, risk of theft of generators, and diesel cost Weather has a significant impact on the availability of the power grid This again favors the implementation of FCs: Mobile • volatile network operator BTS networks susceptible to weather behavior, and particularly in regions • where disturbances are highly predictable Base transceiver system networks that may be placed in extreme temperature regions (hot and cold) In general, the market can be split into three different segments, each having different characteristics influencing the power backup market and each generating different opportunities: • emerging markets, • growth markets, and • mature markets Emerging markets Examples of emerging markets include Latin America, Middle East (parts), Eastern Europe (parts), China, and India The emerging markets continue to expand their infrastructure, exerting significant power demands on inadequate grid networks, and in most cases have inclement weather especially in hot climates The challenges are the limited resources and experience in dealing with markets that are difficult to reach (even with partners), limited financial resources, and the ability to agree on enforceable legal contracts Growth markets Examples of growth markets include Middle East, South/ North Africa, Asia/Pacific, and Eastern Europe (parts) Like the emerging markets, the growth markets continue to develop their infrastructure, which have significant power demands on unreliable grid networks, and in most cases have inclement weather These markets have a great need for backup power supplies that exceed the performance range of batteries In comparison to the emerging markets, the growth markets are more reachable (including sourcing the right partners), with greater geopolitical stability, more enforceable legal systems, and better access to financing Mature markets Examples of mature markets include Western Europe and North America Fuel cells in Western Europe (WE) show significant medium- to long-term market potential Currently, the WE MNOs are slow adopters of FC products owing to power grid stability in European countries As a result, 138 Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells the required backup time in these countries is often only 30–60 per annum in some cases The MNOs are under increasing competitive pressure, in particular prices for telephony are falling Hence, they are looking to cut costs wherever possible, including infrastructure costs Market Size/Market Growth Within the global telecommunications industry, the wireless segment presents a significant growing and dynamic area In most cases, MNOs have their own network infrastructure to provide different services to their subscribers Services primarily include voice and/or data services as well as internet access services All of the different standards and services offered today can be grouped into 2G (GSM (Global System for Mobile Communications), TDMA (time division multiple access), CDMA (code division multiple access), etc.) and 3G (UMTS) technology (2G refers to second-generation mobile phone standard and technology) The wireless telecommunications market is undergoing significant changes, characterized as follows: extreme • for voicegrowth in emerging and developing markets and data, massive network expansion in emerging and de• veloping countries in Africa, Middle East, and Asia, saturation • for data, in the mature markets for voice and growth shift from 2G 3G; and • technologyaverage revenuetoper user (ARPU) decline in • Today, the majority of mobile subscribers use a GSM (2G) network and a growing number connect to UMTS (3G) However, the requirements to expand existing networks and the deployment of the latest technologies vary significantly from region to region Although the 2G extension (e.g., WE) is already stagnating and the 3G implementation is fully under way, in other regions such as Asia, Africa, Middle East, or Latin America, the 2G infrastructure will continue to be in an expansion phase until at least 2010 Even the United States had a subscriber penetration of only 74.9% in 2005 and expects a penetration of 91.1% in 2010 The WE countries have reached a subscriber penetration of 110% ỵ already Additionally, coverage requirements for mobile services are not yet complete According to Credit Suisse/GSMA (GSM Association), 20% of the world’s population not have access to mobile services (Figure 4) The most fundamental implication is that, as 3G is added to 2G and the network capacity is expanding, the networks will need to add additional equipment to the sites, which will have a huge impact on the power required Figure Distribution of world’s uncovered markets Figure Fuel cell (FC) backup power total addressable market 2005–2010 Furthermore, as subscribers increase and coverage improves, businesses will rely on mobile communications, so that the impact of a network failure will be significantly higher The MNO becomes more dependent on a stable power supply and strives to reduce investment and operational cost of backup power systems Furthermore, space will increasingly become a limiting factor According to the Canadian Imperial Bank of Commerce (CIBC) analysts, the low-power (o50 kW) alternating current (AC)/direct current (DC) backup market is ripe for penetration by FCs, as they can meet the increasing power demand of customers: longer run times and higher reliability requirements (Figure 5) Market Entry Hurdles Although the products have already reached the commercialization phase, several hurdles are still standing in the way of mass adoption: telecom network operators • need to be convinced of FCand equipment suppliers technology; turning a pilot project into large-volume contracts • requires a long lead time; further tailor-made products not just for backup • supply, but also integrated ‘alternative energy’ solu- • tions should be developed; regional coverage of sales areas such as Latin America, India, Far East, and China should be increased; Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells lack • cells of economies of scale results in high costs for fuel and fuel cell logistics; there is a high dependence on a limited number of • large customers; and customers of hydrogen although it has been • proved thatare scared more dangerous than petroleum, it is not natural gas, or liquid gas Currently, FC manufacturers are operating in an environment in which the telecom operators still have a relatively conservative impression of FC backup systems The key challenge lies in the ability to persuade key decision makers of the viability of the products as well as development of further tailor-made products for more than just a backup supply role Product Requirements for the Backup Power Market The design process for FCs as the essential part of the backup power supply for BTSs has to focus on engineering a system that delivers the following unique selling points (USPs) Affordable Innovative Technology/Low Total Cost of Ownership Cost is one of the main drivers for choosing a technology Although FCs have key advantages over batteries as backup power, they still have to compete on price (total cost of ownership (TCO) has to be lower): 139 Seamless Integration The FC’s design features allow it to integrate seamlessly with the base stations of the network operators This is achieved by being able to identify the current status of the network operator and to anticipate the future requirements of the network operator in terms of its energy requirements and associated constraints such as noise, pollution, and environmental concerns Fuel cells address these concerns and provide future proofing for the network operator: Cover a wider power to match • the required power ofrange in order right-sizedexactly a BTS The prod- • • • • ucts will allow for the lowest possible sales price at the highest possible margin Low space requirement for hydrogen storage allows for scaling the backup time according to client needs System technology can be designed to fit in 19-inch standardized size (1 inch ¼ 0.025 4m), which allows for integration in existing telecommunication infrastructures worldwide Plug-and-play installation as well as retrofitting into existing BTS installations are possible Lowest possible weight and footprint provide flexibility concerning the size of the installation site Environmental Responsibility The FC needs to reduce the carbon footprint and needs to be a recycling concept: • zero emission system eliminates environmental imprice/performance on site; • backup systems; ratio better than comparable pactssystem is tolerant to the same temperature range FC • as the other telecommunication equipment to minlow operational expenditure (OPEX) through effec• tive use of energy and high-quality system parts; imize the cooling needed; no need for air conditioner (a significant energy saver) hazardous or materials are used; and • unlike batteries or generators; and • no design enablespollutingdisassembling and recycling its for easy • low • lowerweight and lowest possible footprint result in Availability of Hydrogen building construction Proton-exchange membrane fuel cells offer significant cost reduction potential by technological evolution (like the electronics industry), and the high-volume potential for this application can accelerate this trend Reduced Maintenance Effort Maintenance costs drive the OPEX of an MNO To minimize the cost, the system needs to be predictable and inform the MNO about its status: superior shelf life simplifies stock management • opposed to an unpredictable battery system; as individual components • the whole system; and can be replaced rather than owing their fast systems • may betodesigned to start-up capabilities, FC support run without any battery Hydrogen is a widely available gas through delivery from a refinery or can be produced on-site by way of utilizing other renewable energy sources to convert water or other natural gases into hydrogen An important factor is the logistics surrounding the delivery of hydrogen to base stations, especially focusing on the ‘last mile’ Codes and Standards Fuel cells that are to be implemented in telecommunication networks have to comply with telecommunications as well as the FC application standards Not all FC standards have been finalized, approved, and implemented as of yet In these cases, the FC manufacturers often comply with the draft versions of these standards or apply equivalent standards from related technologies or applications 140 Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells lifetime • hours; between about 1000 and 5000 operational the • start-up time ofand stack within a few seconds; high efficiency; • use of air as oxidant • General codes ISO • 9001 (International Organization of Standardization) – Quality Management System Directive 93/68/EEC (European Electronical Com• mittee) – CE (Commission europe´enne (European • • • Commission)) mark Directive 2006/95/EC (European Commission) – electrical equipment FCC (Federal Communications Commission) Class B NEBS (Network Equipment Building System) GR63, GR-1089, GR-487 Table shows a summary of the high-level comparison of various FC options for BTS backup power application In the table, the suitability of the key requirements is compared This comparison reflects short- and mid-term available technologies (up to B5 years from now) (Figure 6) FC codes or equivalent 2006/42/EC Machinery • Directive 62282 – fuel cell modulesDirective DIN EN • EN 60730 – automatic electrical controls for house• hold and similar use UL (Underwriters Laboratories) listed to • (American National Standards Institute) Z21.83ANSI Direct methanol fuel cell Direct methanol fuel cells (DMFCs) are a subcategory of PEMFCs where methanol rather than hydrogen is fed directly to the FC The efficiency and energy density of DMFCs are low owing to the high permeation of methanol through the membrane and lower concentration of hydrogen Hence the membrane is thick and a high catalytic loading is needed, which increases the costs and limits the output power of the FC The DMFC has successfully entered the market where only a low power output is required (typically 100 W) and high power specific prices are accepted, e.g., Telecommunications codes ETSI Telecommunications • stitute)(European019 – temperature andStandards InEN 300 humidity in 100% Thermodynamic 75% el (%) • • • operation ETSI EN 300 132 – power supply interface at the input of telecommunications equipment ETSI EN 300 386 – EMC for telecommunications equipment ETSI ETS 300 753 – noise emitted by telecommunications equipment Products and Solutions For an FC as a backup power solution, there is a list of requirements that should be fulfilled: lowest system costs for medium class power • level inpossiblekW electrical net apower output class; the Table application SOFC Practical (approximated) PEMFC 25% What Is the Best Suitable Fuel Cell Technology for Base Transceiver Station Backup Power Application? MCFC PAFC 50% 0% 200 400 600 800 1000 1200 T (°C) Figure Operating temperature (I) and efficiency of various types of fuel cells (Zel) PAFC, phosphoric acid fuel cell; MCFC, molten carbonate fuel cell; PEMFC, proton exchange membrane fuel cell; SOFC, solid oxide fuel cell High-level comparison of different Fuel cell (FC) technology options for base transceiver station (BTS) backup power DMFC System costs at kW Lifetime Start-up time Efficiency Fuel flexibility Oxidant flexibility H2-PEMFC HT-PEMFC AFC PAFC MCFC SOFC O ỵ O ỵỵ ỵỵ ỵ ỵỵ þ O þþ O þ À O þ þþ þ þ þ þ À À À þþ ÀÀ O þ þþ À þ À À þ þ À þ ÀÀ ỵ ỵỵ ỵ ỵ ỵ þ þ DMFC, direct methanol fuel cell; PEMFC, proton exchange membrane fuel cell; AFC, alkaline fuel cell; PAFC, phospheric acid fuel cell; MFC, molten carbonate fuel cell; SOFC, solid oxide fuel cell Notes: – –, inadequate for application; –, below average; O, average; ỵ , above average; ỵ ỵ , excellent fit/performance Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells mobile homes, boats, and portable military power supplies Today’s DMFCs have a specific price per kilowatt of more than 10 000 EUR Owing to the systematic limitations of the technology, the costs per kilowatt for DMFC will not significantly decrease with increasing output power (owing to lower power density and high catalyst loading) The costs for a kW system would be prohibitive From a fuel perspective, methanol is very attractive It has a relatively high power density, is a liquid fuel, and is readily available It has to be noted however that methanol is poisonous High-temperature proton-exchange membrane fuel cell The high-temperature proton-exchange membrane fuel cell (HT-PEMFC) uses phosphoric acid as the electrolyte, which is fixed in a microporous membrane It operates at T Z160 1C and is tolerant toward carbon monoxide, an unwanted by-product in the gas reforming process in which natural gas is reformed to hydrogen for FC use Carbon monoxide poisons the catalyst when the temperatures are o150 1C The use of an HT-PEMFC would greatly improve the combination of an FC and a reformer to provide backup power without the need of hydrogen The HT-PEMFC is in the research stage or has an early development status The solution is complex, expensive, and has not yet shown appropriate reliability For backup power, the FC has to be kept at high temperatures or the system needs to be warmed up by another energy source before being activated Alkaline fuel cell The alkaline fuel cell (AFC) has the best efficiency of all FC systems Nevertheless, the power density is limited, increasing system size and costs Operating with potassium hydroxide as the electrolyte requires a very clean hydrogen source and bottled oxygen (or carbon dioxide scrubber) as the fuel and oxidant, respectively, which is a very major disadvantage for backup power application as it significantly increases operational costs Because AFCs work mostly without precious metal catalysts, there is a great cost reduction potential The AFC is the source of power for space vehicles Phosphoric acid and molten carbonate fuel cells Phosphoric acid fuel cells (PAFCs) and molten carbonate fuel cells (MCFCs) are primarily designed for higher power applications (>250 kW) and have low power densities Owing to higher temperatures and the materials involved, the kW power level cannot be accessed economically by either technology 141 Solid oxide fuel cell Although the solid oxide fuel cell (SOFC) has been seen as a good candidate for both high (up to several megawatts, for stationary power plants) and low (1–2 kW for combined heat and power in private households) power applications, very long start-up times and severe problems with thermal cycling have prevented market maturity for backup power systems The stack needs to be kept at about 800–900 1C Fuel processors in conjunction with small SOFC systems would add attractiveness toward an application as a primary power source, but reliability and endurance are not yet proven H2-PEMFC The H2-PEMFC has the most attractive overall characteristics for backup power application (see also the following sections, for further details): Operational lifetime is • backup power (B1500 hwithin the range required for for the stack) The FC full power within seconds • that only stack delivers energy buffer in the form so a short-term of ultracapacitors is required used as the oxidant • Ambient air can beoperational temperatures fit very The ambient and • well those required for backup power in a BTS Cost Drivers and Trade-Offs Although the overall system costs are the lowest compared to all other options, costs are still a significant market entry hurdle The FC system has to compete with incumbent technologies such as batteries and diesel generators that already have run through their economies of scale Proton-exchange membrane fuel cell systems still suffer from high prices of the major FC stack components, especially Proton exchange membranes (PEMs): These are often • based on a Teflon derivative Production processes • • • with Fluoron, as part of the product, are usually complex and thus costly PEMFCs require platinum or other precious metals as catalysts The amount of catalyst required depends on system operation strategy, lifetime requirement, fuel purity, and the power density target The gas diffusion layers These are usually porous carbon-based sheets The production volumes are still too small to trigger improved production technologies leading to low-cost components The bipolar plate (BPP), usually graphite composite material or metallic plates Here, as well, the production volumes are too small for high-volume and low-cost components 142 Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells Furthermore, gas supply and membrane humidity management, as part of the balance of plant system, add complexity and cost to the entire system As the stack component costs are essentially proportional to the active FC area, the preferred short- to mid-term strategy is to install a system layout with maximum power density (which is not the point of maximum efficiency) Consequently, the efficiency will not reach the technologically feasible maximum This will change as soon as the market penetration will have reached the critical level for high-volume production A second short-term strategy is to reduce the balance of plant costs by simplifying the system as much as possible Design drivers are directly determined by the product requirement specifications as well as by the basic properties of the membrane–electrode assembly (MEA) However, these strategies quite often are in conflict with each other For instance, an optimum power density would require fully humidified and pressurized gases on both sides Hydrogen recirculation pumps, water separators, and hydrogen concentration control on the anode side also improve significantly the robustness and lifetime On the cathode side, humidifiers and water separators are beneficial Compressors are good to close the water balance in conjunction with humidifiers A few of these components are commercially available and therefore require high engineering and design efforts and lead to high component prototype costs As a general rule, it can be stated that systems with higher power output need more complex peripherals to increase the power density and longevity of the FC stack The applicability of this simple rule can also be seen, looking into alternative applications: • 100 W net power output DMFC J low power density stack 1–8 kW net power output J H2-PEMFC for backup power J low pressure J no humidification feasible 30–100 kW net power output J H2-PEMFC J high pressure J full humidification required J • • It is expected that when the production volume of FCs of a given supplier reaches about 2000–5000 units per year, the economies of scale will drive down the costs to a level where the FC systems can compete with established technologies Existing Solutions and Key Players In 2007, the major players in the FC industry managed to conduct field tests with many potential customers The basic working principles of the FCs offered are identical There are however differences in the maturity of the products, the basic design layout, and the peripheral components offered: The maturity of the systems during • in the range betweenFC prototype and athis period is a low-volume • • • • • product The power range of the commercially available systems is primarily in the range between and kW As short-term energy buffer, to supply instantaneous backup power to the BTS, either lead–acid batteries or ultracapacitors are used All solutions have to comply with the established codes and standards for the telecommunications and the regional safety standards Systems for BTS indoor installation as well as for separate outdoor shelters are available The 2007 costs are estimated to be within a range of 3000–6000 EUR kWÀ1 The mid-term (2008/2009) target prices are expected to be about 50% lower Key players trying to introduce their products into the telecommunications market in 2007 are (in alphabetical order) • Dantherm Systems • Electro Power • Idatech • Hydrogenics • Plug Power • P21 • ReliOn Other companies exist but currently not play a major role Others will most probably follow soon Development Trends for Backup Power Higher sales volumes will trigger significant further progress in manufacturing technology, which, together with the economy of scale, is expected to reduce costs to a level at which a mass market may be addressed In parallel, component suppliers will develop integrated and customized components, allowing further cost reduction and better overall characteristics Trends that have already proven to be technically viable are, for example, molding • liquid injectionseals onto of stackorcomponents; integration of MEAs BPPs; • corrosion-resistant and compact metallic BPPs; • alternative low-cost membrane materials with less or • no humidification requirement; and • alternative catalysts silentcatalyst substrates; and highly efficient and blowers or compressors • Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells Another 50% or more cost reduction can be expected as soon as the volumes will exceed 50 000 units per year, allowing costs of o1000 EUR kWÀ1 With these cost and technology improvements, FCs will not only be able to substitute most of the batteries in the BTS sites but also penetrate and generate other markets for backup power Furthermore, the application may transition from pure backup power toward FC as a primary energy buffer and power source within an integrated regenerative power system Here, a preferred option may be to create hydrogen by water electrolysis from solar and/or wind energy and store it for use in an FC system, when no solar and wind energies are available 143 Hydrogen as a Fuel Depending on the backup strategy and system design, intermediate storage of hydrogen in any type of tank is required One of the most simple, compact, and cheap options to generate hydrogen is reforming of methanol Methanol can be very efficiently reformed at relatively low temperatures (about 250 1C) in a steam reforming process Processing of alternative fuels, such as natural gas, ethanol, propane, or diesel, is still in research phase Such fuel processors potentially offer attractive fuel solutions, but will represent significant challenges in terms of cost, start-up, complexity, reliability, robustness, and lifetime One of the most important challenges is to extract carbon monoxide from the reformat gas, down to levels of o40 ppm (parts per million) carbon monoxide at any time and at any load Although the hydrogen purity requirements are rather moderate for the PEMFC, hydrogen cost, storage, and availability remain a major concern for the customers Future Uninterruptible Power Supply Applications for Fuel Cells Hydrogen price Achieving the status as an energy carrier, the hydrogen cost, e.g., the price per equivalent heating value, will definitely be linked to the world’s major fossil or regenerative energy resources, such as crude oil, natural gas, coal, or ethanol This is evident, as hydrogen can be produced from each of these feedstocks via well-known processes using more or less established reforming technologies Today, the hydrogen price is several times higher per kilowatt hour (kWh) than the feedstock price Considering again the economies of scale and improvements in the production efficiency as well as the investment costs, hydrogen can economically be produced at about 40–50% higher costs compared to the costs of the primary energy source (per kWh) Hydrogen storage and distribution Fuel cells will always enhance the UPS (backup) market in the areas where the negative aspects of batteries (sensitive to temperatures, deliver limited backup, weight) and generators (heavy, noise/air pollution, high maintenance) compromise the use for a certain application The application of FCs is driven by various factors The more of the factors come to materialize, the more the FC will move into the traditional backup market and create new markets: Improvement in • building of the the distribution of hydrogen:asWith the hydrogen economy, e.g., soon as • Hydrogen may be supplied via various options, such as • bottled compressed hydrogen, in liquid form, and • cryogenic,metal or other hydrides stored in • Transportation and storage in these forms remains a problem, although a great effort is needed to solve the associated issues, e.g., development of composite tanks that are more lightweight, have larger volume, and tolerate a higher pressure On-site hydrogen generation Hydrogen can also be generated locally on-site: or alcohols and • by reforming hydrocarbons electrical energy via water electrolysis using • • • • hydrogen will be installed as an energy carrier, and the introduction of hydrogen vehicles, it is expected that the hydrogen will be a commodity such as petrol or propane gas Cost of the system: As stated before, it is expected that in the mid-term the price of an FC will fall to B1000 EUR kWÀ1, reducing the pay back period for FCs, thereby opening the door into markets where the pay back period was prohibitive and for applications in more price-sensitive markets A price of 1000 EUR kWÀ1 translates into roughly h battery backup Increase in the stack life: The longer the stack life, the more the FC will move from a backup to a prime power supply unit Availability of compact hydrogen generation plants: The availability of electrolyzer and reforming technologies support off-grid energy supply Decreased reliability of the power grid: The high economic growth in the developing and emerging economies put a lot of strain on the national power grid The economic growth also increases the expectation by the market to have an uninterrupted supply of electricity 144technRUuu…A•D€DAEr…C•Dë1TK462.3(technRUuu…FTD(AC)Tj/F21Tf7.41110TD[(alternating)-337.7(current)]TJ/F41Tf-7.4111-1.4126TD(AFC)Tj/F21T Change in • There is athe attitude toward personal safety and security: global trend toward more personal safety and higher security requirements by the business sector In addition, legislation forces telecommunication network operators to increase the standby time of their backup systems All these factors have an effect on the FC market It is expected that FCs will become a common feature in the backup power mix A few envisaged applications are described below: Military applications Often the limitation to bringing new technology to the battle field is the limit of power Fuel cells are in the focus of armies as they provide ‘silent’ uninterrupted power Various armies are currently testing FC and reforming solutions Emergency medical centers Mobile hospitals and especially mobile operating rooms require uninterrupted power Diesel generators are currently used to provide the power with all the downturns such as weight, noise pollution, and air pollution Fuel cells in combination with reformers could provide a compact and efficient alternative The units are more energy efficient, thereby reducing fuel consumption Data centers Data centers are often located in dense urban areas where the setup of generator for emergency backup always creates a headache to the operational staff Fuel cells are clean, compact, and quiet Security fencing for homes and estates Currently, batteries and generators provide the power backup for security fencing Batteries offer only limited backup, and diesel generators are too big and too costly to maintain Fuel cells deliver unlimited backup without the disadvantages of a generator Office and home automation Closely related to the above, office and home automation addresses the market for automatic door locks, building surveillance, and online control and monitoring of the building infrastructure The proper functioning of these systems is highly dependent on the availability of the power grid Motorway signs Motorway signs are often set up in areas with limited power supply Fuel cells in combination with batteries deliver the required power Residential generators When the stack life gets close to 10 000 h and hydrogen becomes a commodity, the use of FCs for home power and heating becomes a viable solution Autonomous off-grid solutions One of the greatest challenges for implementing FCs in very remote off-grid solutions is the provision of fuel Even though fuel logistics can be minimized by combining FCs with renewable energy sources, such as wind and solar power, and by means of hybridization with batteries, hydrogen logistics can be costly for locations like mountain tops, islands, and others with difficult or no road access The benefit of using an FC in such a scenario is the ‘peak shaving’ of the power demand, leading to right sizing the renewable energy components and hence to the most economical solution The basic idea is that the renewable sources such as wind and solar energy act as the primary source of power Conventionally designed systems require very large solar panels, battery banks, and wind generators to ensure 100% availability of energy during the annual climatic cycle If an FC is integrated in such a solution, the savings on the renewable components more than compensate for the cost of the FC Reformer solutions for liquid fuels, such as methanol, offer only limited advantages concerning the volume and weight of fuel to be transported per kWh Furthermore, the transients and irregular start-ups associated with the use of renewable primary sources result in technical challenges and increase system complexity and cost The benefit arising from such solutions, where still transportation of fuel to site is required, has not yet been proven in practice Only the combination of a renewable energy source and FC hybrid together with an electrolyzer can provide a fully autonomous solution that completely eliminates the need for fuel logistics Nomenclature Symbols and Units T gel operating temperature electrical efficiency Abbreviations 2G 3G AC AFC ANSI ARPU BPP BTS CDMA CE CIBC DC DMFC second-generation mobile phone standard and technology third-generation mobile phone standard and technology alternating current alkaline fuel cell American National Standards Institute average revenue per user bipolar plate base transceiver station code division multiple access ´ Commission europeenne (European Commission) Canadian Imperial Bank of Commerce direct current direct methanol fuel cell Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells DoD EC EEC ETSI EU FC FCC GSM GSMA HT-PEMFC ISO MCFC MEA MNO NEBS OPEX PAFC PEM PEMFC SOFC TCO TDMA UL UMTS UPS USP VAC VDC WE depth of discharge European Commission European Electronical Committee European Telecommunications Standards Institute European Union fuel cell Federal Communications Commission Global System for Mobile Communications GSM Association high-temperature proton-exchange membrane fuel cell International Organization of Standardization molten carbonate fuel cell membrane–electrode assembly mobile network operator Network Equipment Building System operational expenditure phosphoric acid fuel cell proton-exchange membrane proton-exchange membrane fuel cell solid oxide fuel cell total cost of ownership time division multiple access Underwriters Laboratories universal mobile telecommunications system uninterruptible power supply unique selling point volts alternating current volts direct current Western Europe 145 See also: Energy: Hydrogen Economy; Fuel Cells – Direct Alcohol Fuel Cells: Overview; Fuel Cells – Molten Carbonate Fuel Cells: Overview; Fuel Cells – Overview: Introduction; Fuel Cells – Phosphoric Acid Fuel Cells: Overview; Fuel Cells – Proton-Exchange Membrane Fuel Cells: Cells; High Temperature PEMFCs; Stacks; Systems; Fuel Cells – Solid Oxide Fuel Cells: Overview.Fuels – Hydrogen Storage: Compressed; Fuels – Safety: Hydrogen: Overview Further Reading Atkins PW and De Paula J (2006) Physikalische Chemie 4th edn Weinheim, Germany: Wiley-VCH Baehr HD and Kabelac S (2006) Thermodynamik Grundlagen und technische Anwendungen Berlin: Springer-Verlag ărme- und Stoffu Baehr HD and Stephan K (2006) Wa ăbertragung Berlin: Spinger-Verlag ămungslehre (KamprathBohl W and Elemdorf W (2005) Technische Stro Reihe) Wurzburg, Germany: Vogel Verlag ă Grote K-H and Feldhusen J (2007) Dubbel Taschenbuch fu den ăr Maschinenbau Berlin: Springer-Verlag Hamann CH and Vielstich W (2005) Elektrochemie Weinheim, Germany: Wiley-VCH Ledjeff-Hey K, Mahlendorf F, and Roes J (2006) Brennstoffzellen Entwicklung, Technologie, Anwendung Heidelberg: C.F Muller ă Verlag National Energy Technology Laboratory, US Department of Energy (2005) Fuel Cell Handbook Honolulu, HI: University Press of Pacific, International Law and Taxation Publication VDI-Gesellschaft Vefahrenstechnik und Chemieingenieurwesen (GVC) ărmeatlas Berlin: Springer-Verlag (2006) VDI-Wa Vielstich W, Lamm A, and Gasteiger HA (2003) Handbook of Fuel Cells – Fundamentals, Technology and Applications (4-volume set) Weinheim, Germany: Wiley-VCH  ... Fuel Cells – Direct Alcohol Fuel Cells: Overview; Fuel Cells – Molten Carbonate Fuel Cells: Overview; Fuel Cells – Overview: Introduction; Fuel Cells – Phosphoric Acid Fuel Cells: Overview; Fuel. .. Far East, and China should be increased; Applications – Stationary | Uninterruptible and Back-up Power: Fuel Cells lack • cells of economies of scale results in high costs for fuel and fuel cell... Overview; Fuel Cells – Proton-Exchange Membrane Fuel Cells: Cells; High Temperature PEMFCs; Stacks; Systems; Fuel Cells – Solid Oxide Fuel Cells: Overview.Fuels – Hydrogen Storage: Compressed; Fuels –