Detailed information on energy research

Projektinfo 10/2011

On-board power supply with fuel cells Liquid gas fuelled system enables standalone off-grid power supply

You reach your final destination for the day, switch off the engine of your motorhome, and sit back to enjoy the view. Cicadas chirping and the music of nature are the only sounds you can hear. And then, far away from the nearest mains outlet, you get your laptop out to check your emails and plan your route for the next day. Quietly, and with low emissions, the electrical power you need is produced by your own on-board fuel cell generator. You know that with the fuel cell, your vehicle battery will always be fully charged. Now that the funded research and testing work has been done, fuel cell hybrid systems are ready for the market.

A fuel cell system in leisure vehicles offers an alternative to conventional electricity generation and storage options: fuel cells are between 2 and 5 times more efficient at producing electricity than a combination of combustion engine and alternator. They run on liquid gas (propane or butane). In addition to motorhomes, these systems can also supply electrical energy for boats and cabins, or traffic control systems and measuring equipment, where mains power is unavailable. Modern-day “nomads” want a high level of comfort without having to rely on campsites, which means using electrical appliances such as air conditioning units, lighting, entertainment electronics and compressor coolboxes. The new on-board auxiliary power unit (APU) has been specially developed for leisure requirements with sporadic usage at weekends or for holidays. It copes equally well with con-tinuous and intermittent usage, or with months of not being used. This fuel cell

This research project is funded by the:

Federal Ministry of Economics and Technology (BMWi)

unit operates as part of a hybrid system in conjunction with the vehicle battery. It works at any time of day, doesn’t depend on sunlight and only emits very low l evels of noise and exhaust gases. As such, this system is different to photovoltaic systems or generators. Find-ing fuel for the fuel cell is very easy thanks to the wide-spread availability of liquid gas. Especially in camping applications, liquid gas is state of the art and is used for cooking, heating and cooling.A service life of at least 3,000 operating hours is antici-pated. This is equivalent to using the fuel cell for 750 days at four hours per day. In terms of the average amount of time that leisure vehicles are used – 20 to 50 days per year – this equates to many years of use out of the system.Leisure applications are very well suited to spreading the use of fuel cells because power generation is less price-sensitive in these applications than in everyday domestic use. The manufacturer estimates the electricity generation costs to be around EUR 0.50/kWh (depending on the costs of filling the liquid gas bottles) – which is well within the normal price range for electricity on campsites.

What can the system do?The reformer fuel cell system is designed as a battery charger for leisure vehicles. It combines a liquid gas reformer system based on micro-structured components with a high-temperature polymer electrolyte membrane fuel cell. This is known as a high temperature proton exchange membrane fuel cell (HTPEM-FC). The APU switches on automatically depending on the battery’s charge state and power consumption in the leisure vehicle. Assuming typical usage of 0.3 – 1 kWh per day, the fuel cell system will operate for between one and four hours each day. At 17 – 20 A, the charge current meets battery manufacturers’ recommendations of at least 1/10th of the battery capacity for the batteries usually fitted in motorhomes, which have a capacity of between 70 and 210 Ah. An 11-kg liquid gas bottle is enough to generate up to 28 kWh of electricity.Compared to conventional technologies such as combustion engines, fuel cells score points for long operating times, very quiet running and very low emissions. In contrast to photovoltaic systems they produce electrical energy regardless of the time of day, location or amount of sunlight. Compared to batteries, fuel cells weigh less and have significantly longer service lives.It is easy to install the system in a leisure vehicle. All that is required is a fresh air supply, an exhaust gas / exhaust air duct, the gas connection and an electrical connection to the vehicle battery. Because production volumes are still low, initially the unit will cost around 6,500 euros. As the volume of units being manufactured increases, prices are expected to fall.

Research and development for a market-ready fuel cell systemThe VeGA fuel cell system was developed by Truma Geräte-technik GmbH & Co. KG in partnership with Institut für Mikrotechnik Mainz GmbH (IMM). Truma concentrated on the fuel cell and the system as a whole, while IMM focussed on the liquid gas reformer system.Support for the development of the fuel cell system was provided under the German Federal Government’s Fifth Energy Research Programme, by the National Innovation

Programme for Hydrogen and Fuel Cell Technology (NIP), and by other federal and state initiatives in Germany. As well as the basic and detail design of the reformer system, fuel cell stack and balance of plant (BoP) components – including the dosing system, water circuit, desulphurisation system, system controller and power electronics – the supported projects initially focused on system development, followed by system optimisa-tion.The aim was to develop a fuel cell system that combined simple process technology with optimised production technology. New manufacturing methods and processes suitable for large-scale production were designed and tested by Truma and participating suppliers for a large number of com-ponents and sub-systems. This particularly applied to the reformer system, where special catalyst coating methods and joining techniques had to be developed for the reformer components.Practical testing of marketable applications for the fuel cell system began in the summer of 2008 as part of the National Innovation Programme for Hydrogen and Fuel Cell Technology (NIP). Selected end customers and lei-sure vehicle manufacturers examined around 200 systems in a multi-stage field test. The market launch of the mobile energy plant is planned for early 2012.

How does the fuel cell system work?PEM fuel cell systems require hydrogen or a hydrogen-rich gas in order to operate. Fuels such as natural gas or liquefied gas (LPG), biogas, methanol, ethanol and dimethyl ether (DME) have to be processed before they can be used. This takes place in the reformer. Following the reformation and gas cleaning process, the (hydrogen-rich) gas can be used in the fuel cell. Fig.1 provides a schematic diagram of the process.

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Fig. 1 How a reformer fuel cell system works – process flow from the liquid gas bottle to the leisure vehicle battery. Source: Truma Gerätetechnik

Desulphurisation

Removes odorants and sulphurous components from the liquid gas

Inputströme

Gas supply

Battery

Micro-structured reformer system

Converts liquid gas into hydrogenous gas

High-temperature PEM fuel cell

Electrochemically converts the hydrogen content (together with air) into electrical power, waste heat and product water

Charging electronics

Charge the vehicle battery

Fuel cell system

DesulphurisationIn this step, odours and other sulphurous compounds are removed down to the limit of detection. Odorants are added to liquid gas for safety reasons. These sulphurous gas components can damage the catalyst materials in the reformer and fuel cell even at ppm concentrations. An upstream desul-phurisation unit with a replaceable filter cartridge is used to reliably remove these components from the supplied gas.

Reformer systemA catalyst in the reformer converts liquid gas into a hydrogenous gas. To ensure the safety and long-term stability of the process, a steam reformation process is used. The reformer system is based on micro-structured compo-nents which are designed as a plate reactor. This simple, modular design enables short start-up times, high process stability and a precise level of control.

Fuel cellIn the fuel cell, the hydrogen-rich gas is combined with oxygen (from the air) in an electrochemical reaction which produces electricity, heat and water.Using a high temperature PEM (HT-PEM) fuel cell allows the gas fine-cleaning stage, required in conventional reformer systems, to be completely eliminated. Due to their higher operating temperatures of 140 – 200 °C, HT-PEM fuel cells tolerate a significantly higher level of CO impurities in the reformed gas than low temperature PEM (LT-PEM) fuel cells which have an operating tempera-ture of 60 – 80 °C. An advantage over LT-PEM fuel cell systems is the simpler reformer system. It is easier to cool the fuel cell stack and there is no need for complex hu-midification equipment in the water management system. Exhaust gas, ex-

Fig. 3 Fuel cell system in the rear external storage compartment of a motorhome. Source: Truma Gerätetechnik

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Fig. 2 Configuration of the fuel cell APU for use with liquid gas. Source: Truma Gerätetechnik

haust air and cooling air are dissipated via a combined exhaust air / exhaust gas duct.

Charging electronicsElectricity from the fuel cell is fed into the vehicle battery via an electronic charging system which works in a similar way to a conventional battery charger. The charging electronics are compatible with different battery types (lead-acid, gel, absorbed glass mat).

A different system uses methanol SFC Energy AG produces a fuel cell APU system which runs on methanol. It utilises a direct methanol fuel cell (DMFC). This is a modified PEM fuel cell which can use methanol directly without an upstream reformer. Deliv-ering 40 to 105 W, these units cost between 2,300 and 5,400 euros depending on their power output. They consume around 0.9 l of methanol per kWh, which means fuel costs work out at around 3.50 to 5.50 euros per kWh based on 5-l or 10-l fuel cartridges.The company has participated in research projects to reduce the specific stack costs and to develop an inno-vative and cost-effective new range of accessories.

DC/DC converter HT-PEM fuel cell

Reformer system

Water recovery

Controller

Desulphurisation

Media supply (gas, air, water)

How it works

Water is split into hydrogen and oxygen by electrolysis. In a fuel cell, this chemical reaction takes place in the opposite direction: hydrogen and oxygen react with each other, releasing energy and leaving water as a final product.A fuel cell converts the chemical energy in a fuel and an oxidising agent directly into electricity. The cell consists of two gas-permeable electrodes and an ion-conducting electrolyte layer which separates the gases. At the anode, a catalyst splits the supplied hydrogen into electrons and ions. The hydrogen ions migrate through the electrolyte to the cathode, and the electrons flow as electrical current via the conductor. At the cathode, the electrons and hydrogen ions combine with the supplied oxygen to form water. A single fuel cell generates a voltage of 0.5 – 0.7 V: to obtain a higher voltage, multiple cells are connected in series to form a stack.

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Fuel cells conquer the market VeGA is a fuel cell system for supplying on-board power in leisure vehicles which uses liquid gas, a readily available fuel. It is helping fuel cell technology become more widely used, since hydrogen is not yet available at every filling station.At present, the system is used in less price-sensitive niche markets such as the leisure market. A number of technological and economic hurdles need to be overcome before there is a wider market launch. For example, manufacturing costs and system complexity need to be reduced. This is also the goal of funding for projects aimed at the simplification of processes and manufacturing techniques and at increasing reliability and service life.If fuel cell APUs prove successful in everyday use, this can also be seen as a large-scale reliability test for further mobile and stationary applications. In addition to on-board power supplies, fuel cells could also be used as a range extender to supplement battery storage systems in electric vehicles, if fuel cells can successfully deliver long-term performance in conjunction with battery technologies.Fuel cells convert a fuel gas into electrical energy quietly and with low emissions. As part of a renewable energy economy, wind, solar or bioenergy can be stored in the form of methane or hydrogen and utilised very efficiently via fuel cells in mobile applications. Suitable filling station infrastructure (going far beyond on-board power supplies) would enable a step towards sustainable mobility and towards an energy supply that is not dependent on wind and the time of day.Mobile fuel cell systems enable standalone, efficient and reliable electricity generation for off-grid requirements. In addition to camping and sailing, these also include off-grid applications in mountain cabins, traffic control systems and measuring equipment as well as business and IT solutions (uninterruptible power supply or emergency power generation). In the low output range it is also possible to power smartphones, laptops or entertainment electronics via fuel cells.Work on fuel cell technology will continue to be a funding priority of the German Federal Government‘s Sixth Energy Research Programme over the coming years.

Project participants >> Project partners:

Truma Gerätetechnik GmbH & Co. KG, Putzbrunn, Germany, www.truma.com Institut für Mikrotechnik Mainz GmbH, Mainz, Germany, www.imm-mainz.de

Links and literature (in German)>> NOW GmbH (National Organisation Hydrogen and Fuel Cell Technology): www.now-gmbh.de

Projects supported by the German Federal Government for the development of fuel cells: www.forschungsjahrbuch.de; www.foerderportal.bund.de/foekat | Bavarian Hydrogen Initiative: www.wiba.de | Brennstoffzellen + Batterie-Allianz Baden-Württemberg: www.bba-bw.de | Fuel Cell and Hydrogen Network NRW: www.brennstoffzelle-nrw.de Bodenseeprojekt: www.bodenseeprojekt.de | www.sfc.com

>> Bundesministerium für Wirtschaft und Technologie (BMWI), Berlin (Hrsg.): Forschung für eine umweltschonende, zuverlässige und bezahlbare Energieversorgung. Das 6. Energieforschungsprogramm der Bundesregierung. 2011. www.bmwi.de Kraft und Wärme koppeln. BINE basisEnergie Nr. 21

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Project organisationFederal Ministry of Economics and Technology (BMWi) 11019 Berlin Germany

Project Management Organisation Jülich Research Centre Jülich Dr. Jochen Seier 52425 Jülich Germany

Project number 0327174, 0327770, 0327770A,B,C, 03BS201, 03BS102C, 03BS210

ImprintISSN0937 - 8367

Publisher FIZ Karlsruhe · Leibniz Institute for Information InfrastructureHermann-von-Helmholtz-Platz 1 76344 Eggenstein-LeopoldshafenGermany

AuthorGerhard Hirn

Cover imageTruma Gerätetechnik GmbH & Co KG

CopyrightText and illustrations from this publication can only be used if permission has been granted by the BINE editorial team. We would be delighted to hear from you.

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