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Fig. 1: Technical data for fuel cell heating units
© Manufacturer information

Fig. 2: Structure of a fuel cell heating unit

Fig. 3: Schematic overview showing how a fuel cell heating system functions in a residential building

Fig. 4: Fuel cell heating unit in a basement
© Vaillant GmbH

Testing fuel cells for domestic use in practice

In the Callux project, natural gas-operated fuel cell heating units are being tested in practice with private customers. Appliance manufacturers and energy supply companies are involved in the project, which is being coordinated by the Centre for Solar Energy and Hydrogen Research (ZSW). This test programme has enabled the appliance manufacturers to develop initial small production runs in conjunction with the respective supply chains. The aim is to use the data from the field test to establish the maturity of the technology in order to then start serial production of a commercially ready product.

Further measures are currently being worked on including the development of specifications and standards and, in particular, the training of specialist installers. Supported by NOW (National Organisation for Hydrogen and Fuel Cell Technology), the new technology is being developed as part of the National Hydrogen and Fuel Cell Technology Innovation Programme (NIP).

The aim of the Callux project is to further develop the devices to form systems that are suitable for everyday use. Launched in 2008, the German government’s flagship project is the largest practice test being conducted in Germany, with 232 fuel cell heating units already installed by the end of 2011. According to current plans, 500 devices are due to be installed by 2015 with both PEM and SOFC technology. By the end of 2011, more than 600,000 kWh of electricity were generated in more than one million operating hours.

The manufacturers and energy suppliers are testing the new devices as part of development and demonstration projects. The devices deployed in the field test have so far been running for an average of between 4,000 and 6,000 hours, whereby individual units have already been running for more than 15,000 hours. As of May 2012, more than 230 units were being operated as part of the Callux project. More than 1,000,000 operating hours have now been achieved in total. The EnBW energy supply company has been able to gain experience with different fuel cell systems in more than 400,000 operating hours, whereby one fuel cell has been operating for more than eight years. The lifetime has been considerably improved from device generation to device generation, and the degradation has also been considerably reduced (to less than 2% per 1,000 hours). The average electrical efficiency for all manufacturers is now more than 33%, which means that the electrical efficiency for fuel cell CHP units is considerably higher than for engine-powered CHP systems, and even double as high as systems using Stirling engines. This high efficiency in generating the higher value electrical energy is a feature that sets the fuel cell heating technology clearly apart from other CHP plants.

The fuel cell units in the field test

The first prototype devices were still very susceptible to faults during the field-testing and their performance, output and operating times were considerably less than that striven for. The manufacturers have specified the following target values for the latest systems with an output of 1,0 kWel: the service life is intended to exceed 40,000 operating hours (more than 30,000 hours have already been reached) and the costs are supposed to be halved, whereby the overall efficiency has now reached 97%. Fig. 1 provides an overview of the technical data for the various systems that have been tested in different projects.

Baxi Innotech Gamma 1.0: The low-temperature (LT) PEM fuel cell heating units from the latest test device generation have been undergoing testing in single-family homes since 2009. It is considerably smaller, more powerful and has a longer service life than the predecessor models that have been undergoing field-testing since 2005. It is deployed as a comprehensive fuel cell heating system with an integrated condensing boiler, energy manager and heat storage tank. The system can meet up to 100% of the heating requirements and more than 75% of the electricity requirements. It achieves a high efficiency with full and partial loading, and can be modulated throughout the year in accordance with requirements.

Ceramic Fuel Cells’ BlueGen micro power plant: (not participating in Callux) After 500,000 hours of field tests at customers in nine countries, an initial small-scale production run comprising 1,000 units of the SOFC fuel cell system has been available on the market since the beginning of 2012. It is mainly intended for use in Germany, the Netherlands and the UK. It can be incorporated into existing heating systems as an add-on device and remotely maintained and controlled via the Internet. Together with energy suppliers and a boiler manufacturer, the company is developing a complete fuel cell heating unit based on the system.

Hexis Galileo 1000 N: The device consists of an SOFC fuel cell module and components for converting electricity, extracting heat and providing additional heating. The main component is a double-chamber heat exchanger in which the auxiliary burner is integrated along with a ventilator, gas/air ratio control system and heating circuit pump. It is designed to meet the basic electricity requirements (4,000 – 5,000 kWh/a) and the entire heating requirements (15,000 – 30,000 kWh/a) for a typical Central European single-family home.

Vaillant fuel cell heating unit: Following comprehensive evaluation of the technology and European-wide field tests with 60 systems and more than 400,000 operating hours, the company is now focussing on the further development of a fuel cell heating unit that is based on SOFC technology. The core of the system is a stack model from Staxera GmbH. Further components have been developed in cooperation with Fraunhofer IKTS. The device is mounted on a wall and the system can be started and stopped without any significant drop in the electrical performance. Maintenance intervals are specified at every 10,000 hours. The cold start-up time has now been reduced to 2-3 hours. Together with EnBW, the first wall-hung trial device began operation at the beginning of 2012. After testing 24 devices during the first stage of the Callux project, it is now planned to test a total of 120 fuel cell heating units by 2013.


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