Demonstration af mikrokraftvarme baseret på danske brændselsceller - Fase 1

Transcription

1 Energiforskningsprogrammet PSO-F&U 2006 Demonstration af mikrokraftvarme baseret på danske brændselsceller - Fase 1 Energinet.dk project no. PSO Ventures Solar Inverters Page 1 of 35

2 Summary...3 WP 1 Minimum configuration of the µchp systems... 5 WP 1.1 The SOFC minimum configuration... 5 WP 1.2 LT-PEM FC minimum configuration... 6 WP 1.3 Analysis on µchp...10 WP 2: Development test programme and test of complete systems...10 WP 2.1 Development of test programme for the systems...10 WP 2.2 SOFC system test...11 WP 2.2 LT-PEM system test...12 WP 2.2 HT-PEM system test...13 WP 3: Common activities for all technologies...13 WP 3.1: Optimised heat utilisation system for the µchp unit...13 WP 3.2 Development and installation of heat storage facility...14 WP 3.3 Specification of inverter for fuel cell based µchp units...14 WP 3.4 The LT-PEM reformer system...16 WP 3.5 Installation of Pre reformer (System) for SOFC units:...17 WP 3.6 Development and installation of air supply pump...17 WP 3.7 Development and installation of control device...19 WP 3.8 Development of communication system...19 WP 3.9 Finalizing the systems...20 WP 4 Test, monitoring and optimisation...23 WP 4.1 and WP WP 4.3 Optimisation of BoP components...25 WP 5 Preparation of beta-test...27 WP 5.1 Development and test of control strategies...27 WP 5.2 Safety and authority approvals...27 WP 5.3 Selection of hosts for the 10 β-units...28 WP 5.4 System and project specification of the 10 β-units...28 WP 5.5 Manufacturing preparation for the 10 β-units...30 WP 6 Preparation of cluster demonstration...30 WP 6.1 Development of communication system for coordinated market operation...30 WP 6.2 Payment tariffs...31 WP 6.3 Selection of demonstration hosts (for phase 3)...31 WP 6.4 Education of installers and service technicians...31 WP 7: Project management and communication...32 WP 7.1 Project management...32 WP 7.2 Contracts...33 WP 7.3 Q/A...33 WP 7.4 Reporting...33 Page 2 of 35

3 Summary "Demonstration of micro CHP based on Danish fuel cells, phase 1" in short DKμCHP is the first part of a three phase project. This is the reporting covering phase 1. In Phase 1 - Micro CHP prototypes were developed and tested at a third party, and the results from these first tests provided valuable input, enabling the next versions of the fuel cell based combined heat and power units to be improved. In Phase 2, a number of prototypes will be demonstrated at "professional end users" and in Phase 3 approximately a 100 units will be demonstrated in private homes at "real end users". The full project runs from 2006 to The project includes fuel cells of 3 different technologies: LT- PEMFC, HT-PEMFC and SOFC. Two types of fuel are used, both hydrogen and natural gas and choice of fuel is dependent on fuel cell technology and availability at the installation sites. In the first part of Phase 1, µchp units in minimum configuration were developed and tested at a third party lab DGC. In the second half of Phase 1, close to full configuration was tested at DGC. The HT-PEMFC based unit was included late in Phase 1. As a consequence, only minimum configuration of HT-PEMFC was tested. The µchp units working with LT-PEM fuel cells are developed to be demonstrated with hydrogen as fuel. The Applied LT-PEM fuel cell stack is rated for 2,5 kwe, and was integrated in a stainless steel housing with gas preparation and control electronics and a third party DC/AC inverter. The hydrogen fuelled unit showed an electrical efficiency close to 50% (LHV) on the DC output. The overall efficiency at condensing operation was measured to 90% (LHV) when operated at 70% of full load. The third party inverter was not living up to expectations as it reduced the electrical efficiency to 40%. At lower loads the efficiency was reduced. Important learning s from the test at a third part includes issues on humidification, fuel purging, and heat loss to the surroundings, noise level and start/stop procedures. Adaption to load variation was fast. The µchp units working with HT-PEM fuel cells are developed to be demonstrated with natural gas, but in Phase 1 the test was conducted with hydrogen and at a minimum configuration based on one stack. The test at the DGC lab showed start-up time of minutes with an electrical efficiency of 40 58% (LHV) highest at low loads. In the operation point of the final design an efficiency of 50% is expected. Calculations based on the data measured at the test show a potential system efficiency of 85-90% (LHV). Adaption to load variation was fast. The µchp units working with SOFC are developed to be demonstrated with natural gas as fuel. The applied planar SOFC tandem stack consist of 2 parallel stacks designed for operating at 750 C to 810 C. I first test system (February 2007) the stack was operated at 760 C to 780 C and delivered 1320We DC. The second iterations included a new design of the hot box, heat-up components, catalytic partial oxidation, and burner, heat exchanger for water heating, humidifier, de-sulphurizer and control components. The second iteration (End of 2007) the new system was operated at natural gas a too low temperature (616 C to 686 C) due to system issues. As a consequence the unit delivered only 1080We. Operating on natural gas the unit showed and electrical efficiency of 31% (LHV) relative to fuel input. Total efficiency of 76% at nominal base load is seen. The start-up and cool-down time at the DGC lab was 8 hours. During this period the unit should be purged with Page 3 of 35

4 forming gas. Important learning s from the tests included that gas use during start/stop should be reduced by a faster start-up procedure, the need for DI-water is significant, heat exchanger need to have a higher capacity and after treatment of flue gas need to be improved. Better air tightness of the insulated hotbox will keep the stacks at a more optimum operation temperature and improve the λ ratio for better opportunities of condensing off gases. The testing of the later unit was 2 times 3 hours at operational conditions. The heat storage system with at separate storage for domestic hot water and hot water for heating were integrated with control components and pumps. The test showed, that improvements are needed in both insulation, stratification and placing of pipe connections. The DC/AC inverter was specified both electrical and magnetic and a mock-up was specified, constructed and tested in the lab. The base was build for the construction in Phase 2. Test systems for control and communication were developed and tested. In parallel to the development and integration of the fuel cell technologies, great effort has been done to establish a platform for the long-term cooperation, in terms of team spirit and legal/contractual basis. Furthermore, the important preparations for the future prototype demonstration (Phase 2) and the large-scale implementation (Phase 3) are in good progress. Safety and authority approvals have been investigated. Discussions with the municipalities of Sønderborg and Lolland are ongoing and furthermore, utilities in the regions Syd Energi and SEAS-NVE are showing a keen interest in the project, and have expressed their interest, also, in contributing to financing the tests. In corporations with the utility companies and the municipalities, a model for the cooperation with the Host Project has been drafted and specific locations for the test sites for Phase 2 have been selected. Specifications for the units to be tested in Phase 2 are in place and manufacturing concepts studied. The preparations for the Phase 3 demonstrations are being considered. A parallel project on a control system for a virtual power plant operation has started. Investigations on the possibilities on adjusting tariffs have started. Location of potential demonstration sites for Phase 3 has started. Initiatives on education of installers and service technicians have been taken. The activities will continue. Phase 2 has started. Financing of the Phase 2 and 3 have partly been secured by the Danish Energy Authority. Page 4 of 35

5 WP 1 Minimum configuration of the µchp systems WP 1.1 The SOFC minimum configuration The SOFC stack implemented in the system was supplied by Topsoe Fuel Cell (TOFC), the SOFC stack is a Boxer Stack and consists of two cross-flow stacks, each of the two stacks has 75 cells and the maximum rated unit output is approx 1.5 kw DC (gross). The stack operating temperature is approximately 750 ºC. The Stack has been implemented in an insulated hotbox, designed to have an outside temperature of 60 C and an estimated surface heat loss of approximately 600 Watts. Figure 1: The Boxer Stack Figure 2: The Boxer Stack implemented in the hotbox Dantherm has been in charge of specifying the P&ID and choosing balance of plant (BoP) components for the system, based on the process flow diagram (PFD) specified by TOFC. Major BoP components in the minimum configuration unit include: Electrical heat torches (three pieces) Catalytic burner, ignition system Air/air (high temperature heat exchanger) Air/water heat exchanger Flue gas exhaust fan Temperature and pressure probes with transducers Mass flow controllers (two pieces for air, one for N2 and one for H2) Page 5 of 35

6 Beside these components Dantherm has developed a control unit (see WP 3.7) and safety system for the specific unit. The safety system consists of a bottle of forming gas for the anode side and a bottle of nitrogen for the cathode side, which will flush and protect the fuel cell stack in case of a safety shot down, emergency stop or a power blackout. Results: The SOFC minimum configuration has been tested out of the Lab and valuable experience has been gained. The SOFC minimum configuration has reproduced the SOFC stack performance from the TOFC laboratory test ovens. Data and operation experience is gained as a base for further system development and a more autonomous controlled system. The Dantherm Prototype Control unit performed perfectly during operation. Challenges are detected in terms of heat loss; reduction of the hot box volume and more compact hot parts in the complete system is required. Gas leakages from the hotbox during startup and operation were prevented by a suction blower. This solution will be used in the complete system. Additionally the vacuum generated in the hot box will make the CE Marking less complicated. The thermal problems in the upper part of the hotbox that was detected during the first test series, causing deformation of the hotbox, has been a valuable experience and resulted in a redesign of the hotbox for the complete system. WP 1.2 LT-PEM FC minimum configuration IRD has designed and constructed a LT PEM CHP prototype (Fig. 3). The first prototype was aimed for latter integration with a fuel processor and therefore constructed with an open-end fuel circuit. The LT PEM µchp is integrated into a stainless steel cabinet with the following dimensions: Width 58 cm, height cm, and depth 70.5 cm. The cabinet is divided into the following three parts (Figure 3): 1 An upper part with the LT PEM FC module including the control electronics and the control screen on the cabinet door. 2 A center drawer with a keyboard for control 3 A lower part firstly aimed for the fuel processor, but latter (see discussion below) used to implement a commercial available inverter. The complete cabinet weighs 60 kg excluding the inverter ( 40 kg). The following documents have been prepared for the open-end LT PEM µchp: Jacobsen, S & Grahl-Madsen, L (2006): Safety Guideline.MicroCHP-PEM-INS , 1-5 Page 6 of 35

7 Jacobsen, S & Grahl-Madsen, L (2006): Instrument Data Sheet; PEM Fuel Cell Power Generator, MicroCHP-PEM. MicroCHP-PEM-LST , 1-5 Jacobsen, S; Grahl-Madsen, L & Kaas, J (2006): Operation Manual MicroCHP-PEM-INS , 1-19 A wiring diagram and a P&I diagram was also made at IRD as part of the documentation. Two persons from DGC attended a full day training course at IRD before the unit was shipped for further testing at DGC. The results from the DGC test mentioned latter in this report all referrer to the open-end version of the LT PEM µchp-unit. However, the constructed LT-PEM unit was latter modified for dead-end pure hydrogen operation as some project partners were uncertain of success with the development of the reformat gas clean up and integration of the fuel processor with the LT PEM unit. Simultaneously at IRD a commercial available inverter for grid connection was integrated into the unit. Furthermore, IRD has prepared a spare LT PEM stack in reserve to assure a continuous project flow. Page 7 of 35

8 The reconstruction of the LT PEM unit has entailed that IRD has spend much more manpower in this WP than originally planned. Figure 3. The constructed LT PEM µchp unit. A: Front view of the closed cabinet. B: Picture of the cabinet interior. Parasitic Power (W) Parasitic power consumption in - stand-by mode: 85 W - ready mode: 105 W ,000 1,250 1,500 µchp Power (W) Figure 4: Measured parasitic power consumption during operation of the LT PEM µchp unit. The data shown are measured by DGC (Näslund & de Wit 2007) on the IRD µchp-unit, and in full accordance with internal IRD-measurements. Page 8 of 35

9 % 75 Efficiency (%) % 48.6% Heat ext. heat exch. Heat fuel cell Electricity Figure 5: Measured efficiency of the first version of the LT PEM µchp aimed for reformat (open fuel end) operation. NB; please note that this µchp was not equipped with a DC AC inverter. All data are measured by DGC (Näslund & de Wit 2007) on the IRD µchp-unit. Figure 6: An example of the actual inverter efficiency (89%) measured at IRD. FCG Power (%) 48.6 Grid Power (%), cf Heat fuel cell (%) Condensation heat (%), not implemented 10.0 Combined efficiency (H 2) Table 1: Summary of the obtained efficiencies for the LT PEM µchp in the open-end fuel configuration (H2=1.2) when fuelled with pure hydrogen (cf. Näslund & de Wit 2007). 120 Efficiency (%) Electricity 100 Overall, incl. ext heat exch. Overall, exkl. ext heat exch Stack current (A) Figure 7: Electric and overall efficiencies of the dead-end LT PEM µchp (Näslund & de Wit 2007) tested with the DC AC inverter. Page 9 of 35

10 WP 1.3 Analysis on µchp This report comprises works and conclusions concerning mini/micro CHP units. No new analysis has been made, so the results presented all derive from other origins. This collection has been made to facilitate access to prior works for those involved in the Danish PSO 2006 project Demonstration of micro CHP based on Danish Fuel Cells, phase 1. The overall conclusions derived from the material presented are as follows: Despite the fact that such small CHP units often have lower power and overall efficiency, from an energy point of view they can compete with larger, highly efficient CHP plants and central boiler stations due to the fact that distribution losses are avoided. There is intense international activity concerning development of micro CHP units. Several prime mover technologies are being used. Examples of commercial and near-commercial units can be found in separate chapter + appendices. Although Denmark is the European leader concerning use of CHP, a huge CHP installation potential outside the district heating supplied areas still exist (approx 2000 MWe). This analysis has covered only CHP units < 15 kwe, annual operation > 4000 hours and for natural gas or oil supplied houses with a central heating system installed. A huge fraction of this potential is within a CHP unit size of some 1-4 kwe. The annual CO2 reduction will be > 1 million tonnes per 1000 MWe CHP installed. Analyses of electricity demand profiles for individual houses show that a typical consumer hardly exists. The consumption pattern relies closely on the inhabitant behaviour. A number of different operation/control strategies have been analysed by simulation for the same single-family house. These analyses showed that a heating need based operation strategy will lead to units of a size of approx. 1-4 kwe, the best annual utilisation of the heat potential (seen as a CHP resource) and the highest coverage of internal electricity demand though some electricity has been exported to outside the house. Electricity based operation strategies will lead to quite small units and poor utilisation of the heating. A control system that allows various strategies will be beneficial as future needs and tariffs are difficult to foresee. Supplementary or backup heating is needed. A number of the products on the market have such integrated in their micro CHP products. Also, a heat storage facility will be beneficial. The present Danish tariffs and conditions for grid connection/sales favours own electricity governed operations strategy. This gives poor utilisation of heating as a base for CHP production. With the present Danish gas and electricity tariffs including energy taxation the annual profit to cover investment will in the best case be some 400 Euro per kwe. WP 2: Development test programme and test of complete systems WP 2.1 Development of test programme for the systems The test programme consists of a number of steady-state tests with various electric and thermal loads, return water temperatures etc. Some additional load step tests will also be performed. Page 10 of 35

11 As far as possible the tests agreed should be the same for the different units to be tested in order to evaluate and compare the fuel cell technologies in the same kind of installations. Differences are made due to the opportunities of each technology. According to the project plan the first series of test (the minimum configuration of the CHP units) will be made with hydrogen (hydrogen/nitrogen mixture) as fuel. Performance tests regarding electric and thermal efficiency in a number of steady-state tests (various return water temperature, water flow, electric and thermal load etc) enabling energy balance diagrams are to be made. An Ideal test programme has been drafted. A key focus point is energy balances in various operation points. This is included in the drafted test programme. Also dynamic performance (including start up time and warm/cold start) is considered vital information. As the units at this moment are not yet developed, we do not know if the proposed test programme will be feasible for the actual testing s. WP 2.2 SOFC system test The test series in the minimum configuration shows that the unit works both with respect to the fuel cell stack(s), the Balance of Plant components and the control and safety systems. The gas consumption during heating up and cooling down is significant, as is time. This indicated that the unit, as a cogeneration unit, should be constantly heated and in operation to achieve the best performance regarding power efficiency. At best, a power production efficiency of some 23 % (LHV) was measured in this first test system. The unit was not optimised with efficiency in mind at this stage. The unit and the fuel cell gas requirements was not optimised with respect to power efficiency at this stage. Significant surplus fuel is recommended at present in the operation guidelines. Better energetic performance could be obtained with less outer surface and even more insulation; this is not feasible with the present system components, stack size and design of the insulated casing. The surface losses are estimated to be > 600 W, which is significant for at unit targeting domestic use and should be no more than 200 W. It should be kept in mind that the unit is expected to perform better when using natural gas as feed stock. A hydrogen/n2 mixture is not the best fuel for SOFC stacks. The results obtained and parallel R&D work of stack and BoP components supports that a power production efficiency of > 35% is to be expected for the natural gas fed SOFC unit (complete cogeneration system) to arrive at the DGC lab later Page 11 of 35

12 WP 2.2 LT-PEM system test The tests with the hydrogen fuelled IRD low-temperature PEM fuel cell CHP unit (2 kwe) have shown a basically well operating unit which has good communication possibilities over the Internet. Several performance targets for 2008 have been fulfilled. However, different aspects of moisture and water handling have been found to be critical. The hydrogen fuelled CHP unit has a high electrical efficiency, close to 50%, with DC output. The overall efficiency was measured to 90%. The efficiency decreases with an inverter and 40% electric efficiency was measured at approximately 70% load. The electric efficiency exceeds 30% in the whole operating range. The overall efficiency exceeds 85% at high loads and drops to approximately 70% at low loads due to heat loss. The system has excellent short start up, shut down and load varying performance at hydrogen operation. Equipped with an inverter the output can be at least 25% immediately after the software start sequence from ambient conditions. The performance target on this subject seems fulfilled. The embedded software offers fine opportunities for observing the actual process state, safe operation, error diagnostics and data acquisition. Remote operation has been verified and the current monitoring and control system seems suitable for virtual power plant operation. Water and moisture handling have been a concern during the entire test programme. Initially the fuel humidification caused condensation and flooding in the cell and it was decided to abandon the humidification. The condensation problem in the cell stack remained for different reasons. Also, the air humidifier suffered from drying problems. Improvements in design and operation have reduced the problems. These problems can partly be explained by the intermittent operation of the fuel cell unit, not representative for the operation at a normal user. The understanding of water and moisture handling in PEM fuel cells has improved considerably during the tests. The tests made outside the manufacturer have shown the importance of detailed installation and operation manuals and descriptions. A distinct progress has been made on this topic and it may be used in future fuel cell design and field tests. A few recommendations for improvements and considerations for future fuel cell units are: Humidification of the fuel. The DGC solution did not work and droplets from the air humidification probably caused problems. A humidification unit should be integrated in the unit. Fuel temperature should all time be reduced to 5 10 C lower than the actual stack temperature to minimise the risk of condensation in the stack. This should be clearly stated in the operational manual unless humidification is included in the fuel cell unit. Page 12 of 35

13 The dead-end operation includes a fuel purge operation which involves regular high flows. A small fuel buffer in the fuel cell unit or similar arrangement should be considered in order to make the unit less sensitive to the site fuel supply system sizing. Problems have occurred due to a dry air humidifier. To simplify the maintenance and decrease the service time an arrangement to fill the humidifier without the need to dismantle the unit would be advantageous. The heat loss from the unit was determined to W. This is 5% or more of the nominal fuel input. The loss has to be reduced by at least 50%. An insulated fuel cell stack will probably accomplish this and also increase safety. A heat storage increases the heat loss from the entire system. Since the IRD fuel cell unit will not include a reformer for natural gas in phase 2 and 3 the cabinet may be enlarged to accommodate a heat storage in the lower part. It will also secure an efficient heat insulation of the connecting pipes and simplify the installation. The control system operates well but the need for a specified shut-down procedure should be investigated, for example to remove remaining water. It should also be checked if input parameters are within possible limits. The cathode air fan noise may be disturbing at high loads. WP 2.2 HT-PEM system test Based on the test at Danish Gas Technology Centre (DGC) of the high temperature (HT) PEM based power module (hydrogen fuelled) it can be concluded: Connecting the unit was easy, no extra gasses were needed. Heating up took some minutes for the unit tested. This is faster than for SOFC based units and slower than for low temperature (LT) PEM units. The net electrical efficiency measured was in the range of 40 58% (LHV basis), highest at low loads. At the expected micro CHP design operating point the measured efficiency was above 50%. Taking into account both the expected BOP electric consumption for a complete HT-PEM micro CHP unit and the expected heat losses, the net overall efficiency can be calculated to reach approx % (LHV basis. Good, almost instant load response was seen during the test series. WP 3: Common activities for all technologies WP 3.1: Optimised heat utilisation system for the µchp unit Models for simulation of LT-PEM FC and SOFC were built, and components were tested against the simulation models. Suitable components have been chosen for the heat utilisation system, and a heat management system for fuel cell co-gen systems has been designed and integrated at the bottom of the heat storage. The heat utilisation system heats up a small loop close to the FC, and when it reaches a suitable temperature, it starts charging the heat storage. Testing shows promising results, and controls the temperature levels as planned. However the system needs further work Page 13 of 35

14 before it reaches a commercial state, as it is too large and demands too much manual labour for installation at the moment. WP 3.2 Development and installation of heat storage facility A heat storage with separate tanks for domestic hot water and hot water for heating purposes has been tested at DGC. The inner tank is for Domestic hot water and is the largest. The heat storage and the heat management system are designed to reduce the need for circulation pumps, and therefore only has 5 connections. The system design is shown in the figure below. Figure 8: Diagram of the heat utilisation system and the heat storage The heat storage was tested using a simulation of a fuel cell at DGC in Hørsholm. The main results from the test at DGC are as follows: Heat losses from the system need to be addressed, as too much heat is lost. Further insulation and placing of the connections should be investigated, to minimise heat losses. The temperature stratification of the water in the heat storage was not as good as seen in more ordinary heat storages, and needs to be addressed. Means of optimisation have been suggested (placement of connection pipes, insulation, stratifies etc.) WP 3.3 Specification of inverter for fuel cell based µchp units The first step was to specify the inverter. The specification included all the design parameters and instructions provided by the project partners. This was completed in August of As well, planning and research were carried out to ensure there were adequate time and resources to complete this phase of the project. First, a Risk Assessment was carried out to fully consider all potential risks to both PowerLynx/DSI and the project itself. This work detailed risk for the entire project, not just Phase 1. A detailed Fuel Cell Inverter Project Plan was also created. This plan set detailed milestones and time frames for work on the inverter up to the end of 2007, which stretched into the second phase of the project. Page 14 of 35

15 Finally, a patent search was carried out for power conversion in µchp systems and fuel cells (Patent Search for Existing FC Systems). This was a precaution as well as research into existing products in order to get a feel for the path of commercial/viable developments in the industry. In this stage the topology for the inverter was selected. A detailed review of existing literature was carried out to find the most suitable choice for an inverter topology for this high current, low voltage application. This included research papers, theses, and established converter texts. After careful consideration the choice was narrowed to 2 topologies; the buck and boost. These two topologies were studied and discussed in depth. After careful consideration, it was decided that the isolated boost topology would be chosen. This provided excellent synergy with existing PowerLynx/DSI inverters, as much of the circuitry is similar or identical to proven and tested technologies. It was also decided to use the same topology for all the types of FC system (SOFC, LT-PEM, and HT-PEM). In this manner a more robust and versatile PCB could be designed for both high current (up to 60A continuous) and higher voltage (over 100V). Once the topology was selected, a mock-up was constructed to verify the design. Firstly, the mockup was specified. This was done with input from the stack suppliers/project partners, and was completed in November of Design of the magnetics were designed and specified in parallel with the mock-up spec. These are critical components in the inverter, and proper design and construction is crucial to an efficiently operating inverter. The boost inductor, transformer, snubber inductor, and SMPS transformer were all specified and designed for optimum operation of a low current high power inverter. Mock-ups of each of these components were created in house. After the prototype was specified, it was assembled in house. This was done using a PowerLynx/DSI 1.5kW unit on a 3kW heat sink in order to provide space for the magnetics and power switches, which would be mounted off of the PCB (directly on the heat sink) for measurement/practical reasons. The DC/AC board used in the mock-up was nearly identical to the commercially used DSI inverter sold today. However, extensive alterations were made on the medium voltage DC/DC board. This is the stage that takes the input power from the fuel cell and steps it up to a range that can be efficiently converted to grid voltage. After completion of the mock-up and magnetics, a high current power supply was acquired in order to begin tests in house. Testing was done in order to get a clearer idea of problem areas in the inverters performance. The main areas focused on were the power switching, snubber operation, and signal measurement. These areas were all potential sources of the most significant losses and inverter efficiency. The switching was studied extensively, as the high current and discrete switches all differed greatly from Page 15 of 35

16 current DSI designs. The snubber was also analyzed and was of great interest, as the high change in current coupled with the large stray inductance presented significant switching challenges. All of these areas were influenced by a stray inductance problem in the mock-up caused by excessive use of wire to conduct signals/power. As well, switching speed proved to be a troublesome issue, as high current switches with low resistance can have lower switching times than products used in the present DSI inverter. Faster switches have been selected for the first PCB prototype to be constructed in phase 2. A detailed Orcad schematic was also created for the new DC/DC board. After study of the mock-up performance, it was decided that the DC/DC conversion stage be split into two PCB boards; a power board for the high power flow, and a control board for measurement and control. This would make the design of each board more efficient, and provide a more optimized solution than having all of this stage on one PCB. Phase 1 proved to be a very successful and educational phase for DSI. Much was learned about the design challenges facing the project team in Phase 2, when the mock-up will be implemented on a PCB. As well as specifying and defining what will be accomplished during the project, many contacts with the project partners were established. These contacts can and will be nurtured and strengthened in the next phase of the project to the benefit of all involved entities. WP 3.4 The LT-PEM reformer system Based on Dantherms own experience with many foreign reformer systems together with the experience which was collected in the consortium and via international news media, a reformer from HyGear in Holland was chosen. The reformer did not initially fit into the control algorithm planned for the system concept and was due to this entirely reconfigured and fitted to the system concept, the change in controls also led to a lot of minor changes to the hardware. The reformer was successfully reconfigured to start and operate with 100% automatic control, it was estimated, from temperature data, that the gas quality was good in several steady state values. Along the project duration there was a consortium decision to stop the work with reformation to LT-PEM and the work with optimizing the reformer for dynamic operation and integration with a LT-PEM stack was ceased Page 16 of 35

17 Figure 9: Reformer for LT-PEM Work done: The controls and tubing was changed on the reformer to be able feed on anode waste gas. The reformer was changed to be able to run in hibernation mode, this included control change and bypass hardware implementation. Preparation to integrate with LT-PEM stack was done, including output signals to; power electronics controller; bypass valve; and gas ready signal. WP 3.5 Installation of Pre reformer (System) for SOFC units: The desulphurising unit containing ST-101 was not used in the testing. Dantherm has chosen to use a second desulphurising unit. The ST-101 has some disadvantages and will not be used further in this project. WP 3.6 Development and installation of air supply pump Data from the current systems have been gathered in order to get a clear view of the demand for the air supply unit. The different types that are available on the market and are capable of delivering the amounts and pressures have been identified, and their performance evaluated. Page 17 of 35

18 Principle Type Suitable for: 1 Axial ventilator 2 Centrifugal ventilator 3 Turboblower 4 Regenerative blower 5 Rotary vane Displacement blower 6 Roots blower Displacement blower 7 Rotary screw compressor Dynamic blower HT- PEM Non pulsating flow Oil free Available in many sizes Low cost and decent state of development Dynamic blower HT- PEM Non pulsating flow Oil free Available in many sizes Low cost and decent state of development Dynamic blower All Non pulsating flow Oil free Higher pressure than 1&2 Dynamic blower All Available in suitable configurations Relatively compact Is used in various fuel cell systems Displacement blower All All All + - Non pulsating flow Low noise Relatively compact pulsating low Can be oil free Can be efficient depending on tolerances in housing pulsating low Can be oil free Can be efficient depending on tolerances in housing Not suitable for all sizes Poor turn down Not suitable for all sizes Poor turn down High speed rotation Noise Demanding production Poor turn down Noise originating from pumping principle Low efficiency Poor turn down Most needs lubrication in air stream Low efficiency Wear due to contacting surfaces, very sensible to particles Not available in the sizes required Subject to wear due to tight tolerances Complex construction/manufacture of screw Used most for higher pressure ratios Page 18 of 35

19 8 Piston compressor Displacement blower 9 Diaphragm pump Displacement blower All Efficiency can be ok Pulsating flow Most need oil Used most for higher pressure ratios All Table 2. Comparison of the different blower technologies Low cost Simple construction Pulsating flow Normally limited lifetime Efficiency low Due to the different characteristics of the fuel cell units, it has not been possible to choose a blower principle that would fit the specifications for all 3 types. Due to that fact, the fuel cell systems will still be based on purchased blowers, which match the relevant specifications depending on fuel cell type. WP 3.7 Development and installation of control device Results: The test experiences with the control system on the minimum configuration were very positive. The system showed very good measuring precision, data logging capability, and there were no stability issues whatsoever. The power consumption of the control system was about 30 Watt, which is very low for a pc-hardware based control solution. The system also proved to be flexible and easy to use in practical development situations, contributing to a reduction of the development time for system control algorithms and user interface. WP 3.8 Development of communication system The equipment securing the communication between the heat storage and the fc-unit are under development, and the communication to the system operator will be possible using the same equipment. A development model is build and is now ready for testing of a number of functions. A Tablet PC hosting the User Panel. The Tablet PC has a Z-Wave gateway to connect wireless to the Fuel Cell and Heat storage. RS232 / USB Z-Wave Wireless self-healing mesh network A Control Box with wireless communication to the User Panel and wired communication to the local unit (Fuel Cell, Inverter and Heat storage. One Control Box for the Fuel Cell and Inverter and one Control Box for the Heat Storage. RS485 Analog Page 19 of 35

20 Figure 10: System view A tablet-pc is chosen for the first versions of the Man Machine Interface, as a large degree of flexibility is needed in the first units the picture below is from the first test of communicating with the Dantherm data logging and fuel cell control system. Figure 11: Testing of connections and software In this scope of work, a first version of the High-level Architecture Specification has been written, in order to secure the documentation of the work. The purpose of this high-level architecture specification is to: Describe the high-level static architecture and dynamic behaviour for the Dansk Mikrokraftvarme demonstration Provide a basis for project planning Be used as a reference for the architecture for the following design and implementation phases Provide input to the development of product documentation The document will be available on the Projects SharePoint webpage. The work in this task will continue with further work specifying the available menus and functions available for the user on the MMI screen. WP 3.9 Finalizing the systems Purpose The development of a SOFC CPO μchp system had the following main goals: Page 20 of 35

21 Demonstration of the SOFC technology, integrated in a real system, where the fuel input is natural gas and the output is heat and electrical power Validation of system performance and efficiency (See WP 4.1) To gain experience for further improvement through real operating conditions in a natural gas fuelled SOFC μchp system To point out key components for system improvements, based on energy balances SOFC stack behaviour and performance in a natural gas system Out of the lab experience (safety and logistics) The SOFC CPO system The SOFC CPO system is a μchp system, converting natural gas to heat and electrical power. Based on the experiences from developing, fabricating and testing the SOFC minimum configuration in WP 1.1, it was decided to change the first actual SOFC system concept, to a new improved concept, including a Catalytic Partial Oxidation unit (CPO) for natural gas processing. Dantherm was in charge of designing the unit and the control system. Topsoe Fuel Cell was in charge of supplying the SOFC stack and the CPO and DGC was responsible for testing the system. The unit s outside dimensions are: mm (height width depth). The stack and some BoP components are located inside the hotbox, consisting of high-temperature insulation, as the stack temperature during operation must be between 750 C and 810 C. Internal heat exchange for preheating of air and fuel is used to largest possible extent. And final, a water-based cooling circuit in the unit is transferring surplus thermal load. The SOFC stack implemented in the system was supplied by Topsoe Fuel Cell A/S (TOFC), the SOFC stack is a Boxer Stack and consists of two cross-flow stacks, each of the two stacks has 75 cells and the maximum rated unit output is approx 1.5 kw DC (gross). The stack operating temperature is between 750ºC and 810 C. The Stack has been implemented in an insulated hotbox, designed to have an outside temperature of approx. 60 C and an estimated surface heat loss of approximately 600 Watts. The CPO unit is implemented in the lower part of the hotbox insulation and supplied with DI water, air and de-sulphurized natural gas for the fuel preparation. The thermal integration of the CPO unit and a new developed start-up method was tested successfully in a sub-system, and implemented with success in the SOFC CPO system. Page 21 of 35

22 The CPO system development consists of all the following sub-components: Natural Gas desulphurization unit Catalytic Partial Oxidation unit (Supplied by TOFC) DI water supply system Vaporizer for DI water CPO air supply system Fuel supply system (Natural gas and forming gas) Figure 12: Inside the Hotbox Figure 13: The SOFC CPO System in operation Figure 14: SOFC CPO System (Open frame) Results: The SOFC CPO system test at DGC was a success. The SOFC stack had a maximum electrical power output of 1080 We, as the temperature was not in above the minimum operation temperature of 750 C due to some system issues on temperature control in the test. The mechanical design and overall system concept performed fine. The new concept under Page 22 of 35

23 pressure in the system has been stated successfully in line with the CPO System integration and the new CPO setup procedure. The electrical efficiency for the unit at nominal load is approx. 31% compared to fuel input (LHV reference). If electric input for heating and fan operation is also included in the energy input the electrical efficiency is some 24% pressure in the system has been tested successfully in line with the CPO System integration and the new CPO startup procedure Total efficiency for the unit at nominal load is approx. 76%; taking into account both fuel and electrical energy input. If the exhaust is cooled to the water return temperature total efficiency will be 80% The logistics to DGC and installation went smoothly, experience from the minimum configuration was a big advantage 8 hours for heating up the system and 8 hours to cool down. Data and operation experience was gained as a base for further system development and a more autonomous controlled system. The Dantherm Prototype Control unit performed perfectly. A new more compact control unit will be used in the future systems Challenges are still detected in terms of heat loss, reduction and airtightness of the hotbox, stack and CPO volume is needed to reach the future efficiency goals. Effects of the under pressure in the stack and system still needs to be verified for a longer test period, as this is the first test with this concept. There is on doubt that the under pressure generated in the hotbox will make the CE-marking less complicated Gas leakages from the hotbox during startup and operation were prevented by a suction blower. This solution will be used in the complete system. Additionally the under pressure generated in the hotbox will make the CE-marking less complicated WP 4 Test, monitoring and optimisation WP 4.1 Functional tests SOFC-CPO unit An improved version of the SOFC based unit was tested at the DGC-Labs late This micro CHP unit was fitted with a CPO fuel processing unit and was natural gas fuelled. The natural gas needs to be de-sulphurised; this was done via absorption device on the DGC gas supply line, see fig.15. Page 23 of 35

24 Fig 15 e-sulphurisation unit -Conmtrould DGC natural gas supply line. Figure 16 The SOFC-CPO unit The SOFC-CPO unit has been improved since the minimum configuration version. Significant volume reduction has been made despite the fact that the unit now contains even more components. Significant volume reductions have been achieved compared to the unit in the minimum configuration. This has been made despite the fact that the unit now includes even more Balance of Plant components. Starting time has also been reduced significantly compared to the minimum configuration tests. Electrical efficiency at nominal load was approx. 31% relative to fuel input (LHV basis). Total efficiency of the CHP unit is approx. 76% at nominal load. Both fuel and electrical energy input is taken into account in this number. If the exhaust is cooled to the return water temperature measurements of heat recovery in the external heat exchanger indicate that the total efficiency can go up to 80% at nominal load. The unit is not fitted with an DC to AC inverter and the efficiencies stated are with DC reference. Efficiencies drops at part load operation, the unit should from an efficiency point of view be kept at nominal load. Possible improvements might be: Less surface losses (better insulation), less own electric consumption (may follow as a result of improved insulation) and improved air tightness. The unit operates at a high air to fuel ration and dilution air increases air excess in the final exhaust. The latter makes condensing mode operation more difficult to obtain. The unit needs Formier gas during start up and cooling down. In the tested version it also needs external DI water supply. WP 4.2 Functional tests IRD LT PEM unit Page 24 of 35

25 The completed LT-PEM version is hydrogen fuelled (dead end fuel supply line) and a DC->AV (230 Volt) inverter fitted unit. The used inverter can be seen at the lower part of figure 3B When using a dead end fuel supply, fuel purging is needed. This is integrated in the units control system. Functional tests were made at the DGC Lab. The findings at these tests were: Electrical efficiency approx. 40% (LCV basis) Total efficiency > 85% (LCV basis) Measured efficiencies at various loads can be seen in figure 7. Improved electrical efficiency is to be inspected by using the inverter developed within the project. Short start up time was measured, operation at 25% electrical load possible almost immidiately after start, heating followed some minutes later. Excellent load response was seen. Performance targets (2008) seems to be fulfilled. Problems were seen regarding moisture/condensation in the cell stack, partly caused by intermittent operation of the unit during the test period. The understanding of water and moisture handling in PEM fuel cells have improved during the tests and lead to sign and operation manual alterations. WP 4.3 Optimisation of BoP components During the first phase of the SOFC system development, a lot of experience and knowledge has been gained on BoP components. The BoP components have been specified and the knowledge has been shared with the project partners. At the moment, TOFC has developed a new SOFC counter flow stack which possibly can reduce the numbers of cells in a 1,5 kw stack from 150 cells to 100 cells and at the same time reduce the pressure loss. This means that the volume, complexity and integration of the boxer stack will be simplified and contribute to radical system improvements, this will also reflect as a positive impact on the parasitic losses from the BoP components in the next system. BoP Concepts In order to make the system less complex, more efficient and easier to pass the CE marking, the following concepts was developed and implemented in the SOFC CPO System: Under pressure in the system is relevant in case of a gas leakage - for safety reasons Under pressure can also facilitate the low pressure in the natural gas grid and the use of a CPO air blower A new developed CPO start-up procedure is saving components and complexity Thermal integration of the CPO unit inside the hotbox Condensate system for recycling of DI water in the next version Burner development and integration DI water vaporizer for the fuel processing Page 25 of 35

26 BoP Components Dantherm has been in charge of specifying the P&ID and selecting some of the most efficient BoP components available on the market. Major BoP components in the SOFC CPO system include: Electrical heat torch for preheating the natural gas Electrical heating elements to preheating of the hotbox DI water pump Air/air (high temperature heat exchanger) Air/water heat exchanger Flue gas exhaust blower CPO blower Flow meters Air filters Temperature and pressure sensors Mass flow controller for natural gas Valves Figure 17: SOFC stack and BoP Figure 18: BoP Compartment Page 26 of 35

27 WP 5 Preparation of beta-test WP 5.1 Development and test of control strategies During Phase 1 of DK microchp, several bilateral discussions have been ongoing on the subject of control of the units. A note covering the different aspects has been produced, and a Danish version is available at the collaboration site. The overall conclusion on the controlling issues of the unit is, that it will be a mix of the 2 overall strategies load following and heat following. In real life this means, that even if you choose the load following strategy, the μchp units will still have to secure that the right amount of heat is available, both for heating the house and for the production of domestic hot water. To secure the function as power plant meaning that the power production capability of the unit can be utilised if it is needed on the surrounding grid the use of heat storage has been decided on from the start of the project. An auxiliary burner for peak production of thermal heat is to be integrated in the commercial unit. WP 5.2 Safety and authority approvals In the case of stationary fuel cell plants for CHP operation we would recommend the following: To comply with the Gas Appliances Directive. To comply with a number of other directives. To CE mark the fuel cell plant when it is not a test plant installed in a laboratory. Installation of the fuel cell plant must comply with the requirements of the Danish Gas Regulations. To comply with the Pressure Equipment Directive. Pressure vessels below 0.5 bar have particularly gentle rules. Furthermore, it is necessary to obtain a construction approval from the Danish Working Environment Authority. The installation must comply with the requirements of the local fire protection authorities. In the case of a larger installation it might be necessary to obtain a building permission. A number of international standards are being prepared to facilitate compliance with the above mentioned directives. The standards are primarily aiming to describe a standardised way to comply with the Gas Appliances Directive. It is DGC s recommendation to respect not only the legislation in force, but also the standards that CEN and IEC s TC105 are drafting; some of which have already been published. Many Gas Regulations requirements severely affect the construction and design of the plant. To achieve efficient implementation of the requirements of the Gas Appliances Directive it is necessary to acquaint oneself with these requirements very early in the process - e.g. when entering into the actual design phase from the conceptual phase. Correspondingly, experience shows that it is necessary to involve relevant authorities in the installation work very early in the process and, at any rate, prior to any practical installation work. Page 27 of 35