Malmö Hydrogen and CNG/Hydrogen filling station and Hythane bus project

Transcription

1 WHEC 16 / June 2006 Lyon France 1(10) Malmö Hydrogen and CNG/Hydrogen filling station and Hythane bus project Bengt Ridell Carl Bro Energikonsult AB, Sweden, bengt.ridell@carlbro.se Abstract: The hydrogen production plant and the filling station is situated in Malmö, Sweden owned and operated by E.ON Gas Sverige AB. It started operation in September The hydrogen is produced by electrolysis in direct connection to the filling station. Two buses of the local bus fleet have tested in more than two years CNG mixed with 8 % vol of hydrogen as fuel without any modifications of the lean-burn CNG engines. The Lund Institute of Technology at Lund University, Sweden, has confirmed significant improvements in fuel efficiency, more stable operation of the engine and reduction of emissions by performing bench testing of the engines. The heavier mixture with 25 vol % hydrogen has required modifications of the mapping of the engine both for ignition and the air/fuel ratio. Keywords : Hydrogen filling station, Hythane, CNG, buses, ICE

2 WHEC 16 / June 2006 Lyon France 2(10) 1. Background The largest private utility company in Sweden, E.ON Sverige AB, with its head office in Malmö has a history of being in the forefront of the technologically development. The utilities former name was Sydkraft, today it belongs to the German E.ON group. Already in 1985 Sydkraft and the Municipality of Malmö started a long-term co-operation regarding conversion from diesel to CNG on the city busses. Now in the region Skåne more than 330 buses, 80 trucks and about 1000 cars are running on CNG and biogas. In 1995 the parties both implemented use of Electric Vehicles in their fleets as a part of a large EV demonstration project in the region. This quest for testing new alternative fuelled vehicles has continued and the latest step is now to test hydrogen mixed together with natural gas for local city buses. Carl Bro Energikonsult AB has been an active partner in the Malmö hydrogen filling station project from first idea, design, project management, procurement, start up of the filling station and the follow up of the operation of the plant and the buses. 2. The hydrogen production plant and filling station, The hydrogen plant and the filling station is situated at Nobelvägen 66 in Malmö and owned and operated by E.ON Sverige Gas AB. It started operation in September At the same site there are filling stations for CNG and also electrical vehicles. The hydrogen is produced by electrolysis in direct connection to the filling station. The electricity is produced in a nearby windpower plant and distributed to the plant via the electrical grid. The hydrogen plant including the production and filling station is delivered by Stuart Energy, Canada today called Hydrogenics. Vandenborre Hydrogen Systems in Belgium now owned by Hydrogenics ltd, Canada manufactured the electrolyser unit Technical data for the electrolyser as stated by the supplier, Capacity: 36 Nm 3 H 2 /h Power consumption electrolyser: 4,2 kwh/ Nm 3 H 2 Power consumption in total: 5,5 kwh/ Nm 3 H 2 Water consumption: 36 l/h Pressure from electrolyser H2: 10 bar Power requirement: 210 kw Load area: % The above pictures show the compressed hydrogen storage at the site. The hydrogen storage is placed closed to the electrolyser unit. Dynatech, Canada delivered the pressure vessels. Pressure 393 bar Volume 4m 3

3 WHEC 16 / June 2006 Lyon France 3(10) The dispenser is delivered by FTI, Canada. It consists of two hoses one for pure compressed hydrogen and the other for the mix of hydrogen and CNG. The mixture is done in the dispenser directly while filling the vehicle fuel tank. The different fuelling options at the dispenser are, Hydrogen 350 bars Hydrogen 200 bars H2/CNG CNG with a blend of 8% vol hydrogen H2/CNG CNG with a blend of 20% vol hydrogen The backgrounds to use these four fuelling options are Hydrogen 200 bar is a classic standard for delivery of bottled industrial hydrogen and several hydrogen demonstration vehicles are using 200 bar as pressure in the fuel tank. Hydrogen 350 bar is a new standard often used for fuel cell vehicles. DaimlerChrysler Evobus has specified 350 bar as onboard storage for the hydrogen fuel on their Citaro buses used in the CUTE and other similar projects. It is also the standard for DaimlerChrysler FCell fuel cell cars and several other modern demonstration vehicles using hydrogen as fuel. H2/CNG with a blend of 8% vol hydrogen; this lean mixture of hydrogen into the CNG is considered as CNG according to the specification of natural gas. The mixture can be used directly in the current CNG city buses without any modifications of the fuel system or engine set points or hardware. H2/CNG with a blend of 20% vol hydrogen; A larger portion of the fuel is produced locally and more environmental benefits can be achieved. This heavier mix of hydrogen into the CNG cannot be considered as natural gas. A modification of the engine set points for ignition and fuel injection is required. A comprehensive safety check of the fuel system of the buses has been performed.

4 WHEC 16 / June 2006 Lyon France 4(10) 3. The bus project, engine improvements The background of the bus project to use a mixture of hydrogen and CNG are To use a locally produced fuel To improve the efficiency and the operation of the engines To decrease emissions, both local emissions and CO 2 Two buses of the local bus fleet have used CNG mixed with 8 % vol of hydrogen as fuel without any modifications of the lean-burn CNG engines. The Lund Institute of Technology at Lund University, Sweden, has confirmed significant improvements in fuel efficiency, more stable operation of the engine and reduction of emissions by performing bench testing of the engines. Measurements of efficiency, emissions, combustion variations, knocking etc have been performed during different conditions. 40 Efficiency 2000 rpm 38 NG map-ign H2 map-ign Efficiency [%] Brake efficiency in % with 8% Hydrogen mix into the CNG compared with pure CNG for different air/fuel ratios Lambda It is reasonable to expect that the brake thermal efficiency could increase with hydrogen mixed into the CNG fuel as compared to pure natural gas since the combustion duration is reduced. With reduced combustion duration the effective expansion ratio increases and more work can be extracted from the gas. This increase in efficiency is likely to be the highest where the combustion duration is long with natural gas, i.e. at lean conditions./1/.the Volvo TG100 engine used in the local city is lean burning engine and can thus profit from the use of the mixture of hydrogen and CNG as fuel. The increase in efficiency together with the reduction of the carbon content in the fuel decrease the emissions of CO 2 substantially fuel when the use of hydrogen as a fuel additive.

5 WHEC 16 / June 2006 Lyon France 5(10) Emissions [g/kwh] Emissions 2000 rpm map Ignition HC NG HC H2 NOx NG NOx H2 CO NG CO H2 Emission values from tests with 8% Hydrogen mix into the CNG compared with pure CNG for different air/fuel ratios Lambda Lambda= air/fuel ratio A mix of hydrogen into the natural gas creates a faster combustion and thus more efficient combustion. Lower emissions of HC and CO are then achieved, as the combustion is more efficient. The higher combustion temperature can though increase the NOx emissions. This can be avoided by using a higher air/fuel ratio and/or less spark advance. 7 6 COV IMEP 1300 rpm NG map-ign H2 map-ign COV IMEP [%] Lambda H2 = mix of 8% hydrogen and CNG COV: Coefficient of variation Lambda= air/fuel ratio The flame speed of hydrogen is much higher than that of hydrocarbon fuels. Adding hydrogen to natural gas is thus likely to increase the flame speed of the charge. This could be used to extend the lean limit of the natural gas engine to air/fuel rates ratios where pure natural gas provides insufficient burn rate for stable combustion./1/ Summary of the conclusion with the measurements in a laboratory with a mixture of 8 % vol into the CNG using a Volvo TG100 engine. Higher efficiency More stable combustion, due to a faster combustion (less cycle to cycle variations) A slight increase in power Lower HC and CO emissions because of higher combustion efficiency Higher or similar NOx emissions (with no changes applied to fueling or spark) Slightly higher knock tendency

6 WHEC 16 / June 2006 Lyon France 6(10) Further test with a 20% hydrogen mix in the CNG have been performed in the laboratory. These tests show significant improvements compared to pure CNG. The reduced combustion duration increases the efficiency significantly and enables the reduction of NOx emissions by using a higher air/flow ratio combined with optimised ignition timing. The reduction of CO 2 -emissions is substantial NOx vs. HC, ignition (c) NG NG+H NOx vs. HC, ignition (d) NG NG+H NOx (g/kwh) NOx (g/kwh) HC (g/kwh) HC (g/kwh) Figur 1: HC - NOx trade-off with natural gas and Hythane. The markers represent different air/fuel ratios. Intermediate ignition timing strategy. Figur 2: HC - NOx trade-off with natural gas and Hythane. The markers represent different air/fuel ratios. Retarded ignition timing strategy. The above figures show results from engine tests with 20% vol hydrogen mixed with CNG. It shows the trade-off between HC and NOx emissions when different ignition angels have been used. The different measurements shown represent different air/fuel ratios. Extreme air/fuel ratios can lead to other problems like instable engines or too high knock tendency etc. Furthermore is also the other the harmful emissions significantly decreased as the carbon content of the fuel has decreased with the heavier blending of hydrogen in the fuel. This is especially significant for the reduction of CO 2 emissions. 4. Emissions testing on the road In August 2005 one bus was selected for emission testing on the road /5/. All other measurements have been done in an engine laboratory with an engine of the same type as the one in the city buses, Volvo TG100 lean burning engines. The bus was driven both with CNG mixed with 20 % hydrogen and pure CNG. Four different the tests were performed, 1. Max power in a long uphill slope on a motorway during non rush hour conditions 2. Steady state driving on an old airstrip at velocities between 20 and 70 km/h 3. Measurements during idling 4. Start from a bus stop and acceleration up to 40 km/h During the different tests were emissions, airflow, speed and engine rpm measured. During the uphill slope tests the velocity was significantly higher, 10 km/h, when the bus used the CNG mixed with 20% vol hydrogen fuel compared to pure CNG. The positive influence from the hydrogen mixed into the CNG is because of the higher flame speed and thus more efficient burning. The lean burning engines can have some misfiring when they go very lean. The Hythane fuel gives as mentioned before a higher efficiency and in some cases also higher power to the engine. The hydrocarbon emissions were significantly lower but the NO x emissions were in this test higher with CNG mixed with hydrogen fuel. The NO x emissions were lower in the laboratory during steady conditions.

7 WHEC 16 / June 2006 Lyon France 7(10) Speed (km/h) Emissions at constant velocities between 20 and 70 km/h The CO emissions were higher with Hythane at low velocities but lower above 35 km/h this is explained by the effect of the lean burning. A gearshift at these velocities did complicate the measurements. Fuel consumption at test during constant velocities The fuel consumption was lower with the Hythane mixture compared to CNG as the efficiency is higher.

8 WHEC 16 / June 2006 Lyon France 8(10) Emissions accumulated (gram) during 24s acceleration from a bus stop The results in the graph above are based on the accumulated emissions measured during acceleration of the bus from standstill to 24s. Measurements have been made very second. These tests were made with an old engine that has been in operation in a bus during real conditions about 10 years and km. Another bus might have given different results. These conclusions are not valid for new CNG engines. The fuel consumption and thus the CO 2 -emissions have decreased up to 10%. In other tests has values higher than 20% been measured. The NO x -emissions has increased with Hythane. This increase can be avoided by a more accurate mapping of the engines air/fuel ratio and ignition set points. 5. The findings and status of the bus and vehicles operation The operation with the mixture of 8 vol % hydrogen in the natural gas started in September Two city buses have used the Hythane fuel with 8% vol hydrogen. This has been done without any modifications of the engines. The buses could then also use CNG as fuel if needed. The heavier mixture with 20% vol hydrogen in the CNG has been used since the beginning of year This has required modifications of the mapping of the engine both for ignition and the air/fuel ratio. Connecting a PC for adjustments of the control system of the bus engine did the necessary modifications. There have not been any hardware modifications done. A comprehensive study of all components regarding safety has been performed by the engine manufacture. The buses have been in operation with CNG/hydrogen mixture more than km and used about 33 tonnes of CNG mixed with hydrogen8% vol and 6 tonnes of CNG mixed with hydrogen25% vol. There have not been any operational problems what so ever caused by the fuel. The buses and the engines have been examined by hydrogen detection systems but there has not been any signs of cracks or leakage of hydrogen The fuel consumption measured by a daily journal has shown 20 30% lower fuel consumption using CNG mixed with hydrgen instead of pure CNG

9 WHEC 16 / June 2006 Lyon France 9(10) The long-term vision is to use a mixture of hydrogen and CNG in all the city buses. Several passenger cars have tested the low-grade CNG mixed with hydrogen8% vol fuel with good results. There is a foreseen project to test 10 passenger cars including taxis and other service vehicles running on CNG mixed with hydrogen for a longer test period. A few hydrogen vehicles have visited the filling station but there are not yet any demonstration projects for vehicles running on pure hydrogen.

10 References: WHEC 16 / June 2006 Lyon France 10(10) 1. Per Tunestål, Patrik Einewall, Ola Stenlåås, Bengt Johansson, Lunds Institute of Technology, department of Heat and Power Engineering, Lund, Sweden, Poosible short-term introduction of hydrogen as vehicle fuel / fuel additive, Edition Technip Paris Per Tunestål, Magnus Christensen, Patrik Einewall, Tobias Andersson, Bengt Johansson, Lunds Institute of Technology, department of Heat and Power Engineering, Lund, Sweden, Hydrogen additive for improved lean burning capability of slow and fast burning natural gas combustion chambers, Society of Automotive Engineers, Inc, USA 3. Bengt Ridell Carl Bro Energikonsult AB, Malmö Hydrogen and hydrogen /CNG filling station, paper presented at the Hydrogen and Fuel cells 2004 Conference and Trade show, Toronto, Canada, September 27, Malmö Hydrogen and hydrogen/cng filling station and Hythane bus project, Bengt Ridell Carl Bro Energikonsult AB, paper presented Risø international energy conference May 2005, Denmark 5. Owe Jönsson, SGC, Swedish Gas Centre Utveckling och demonstation av användning av metan/vätgasblandningar som bränsle i befintliga metangasdrivna bussar, final report for the Swedish Energy Agency, December 2005.