Biogas electric hybrid bus Evaluation of the Baltic Biogas Bus investments & activities in Västerås Sweden 2013-2014
This publication has been produced with the assistance of the European Union (http://europa.eu). The content of this publication is the sole responsibility of Baltic Biogas Bus and can in no way be taken to reflect the views of the European Union.
Contents 1.
Introduction ............................................................................... 3
2.
Developing the new hybrid bus ......................................................... 4
3.
Piloting the new hybrid bus ............................................................. 6
4.
Comparison between the hybrid bus and conventional buses ...................... 6
5.
Users’ experience ........................................................................ 9
6.
Spin off .................................................................................... 11
7.
Conclusions ............................................................................... 11
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1. Introduction The Baltic Biogas Bus project is a EU-funded project aiming to encourage cities and regions around the Baltic Sea to use biogas as a fuel for public transport. Increased use of biogas in urban traffic will reduce emissions of fossil carbon dioxide and also help reduce other air emissions and noise. The project has addressed these issues by enhancing upgrading of biogas to fuel quality and energy efficiency of vehicles in eight countries in the Baltic Sea Region. To address the second task, biogas electric hybrid buses were procured by the lead project partner Västerås Lokaltrafik (VL) in Sweden and HOG Energi and Skyss in Norway. This report is an evaluation report on the biogas electric hybrid bus obtained by VL, with the aim to analyse the energy efficiency and environmental impact of the bus in comparison with the more conventional biogas buses and diesel buses in VL’s bus fleet. Results from a comparison like this give a wider perspective on the environmental impacts and the cost-effectiveness of the hybrid bus.
Figure 1. The new biogas electric hybrid bus in Västerås. Source: Västerås Lokaltrafik.
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2. Developing the new hybrid bus VL together with its 550 employees provides an average of 35 000 costumers per day public transport services in Västmanland County in Sweden. One of VL’s goals is to have a 100 percent fossil free operation no later than 2020. The main renewable fuel used in the company’s bus fleet is biogas. Today, VL owns 170 buses of which 130 are powered by biogas, one bus is the new biogas electric hybrid bus and the remaining buses are diesel buses. Following these strategic investments, 75 percent of VL’s regional bus fleet is running on biogas. The bus fleet is continuously upgraded and every year approximately 15 diesel buses are replaced by biogas buses. Three depots in Sala, Köping and Västerås are adapted to provide the biogas buses with fuel. A fourth and last depot of VL in Fagersta, is currently being adapted, and in year 2015 VL is expecting to be able to run biogas buses in the whole operating area of VL.
Figure 2. Västmanland County’s location in Sweden is marked on the map to the left. The map to the right is showing the municipalities in the county. VL has depots in Fagersta, Sala, Köping and Västerås. Source: Västerås Lokaltrafik. 4 www.balticbiogasbus.eu
VL has a long tradition in being in the front line of technical developments and finding new sustainable solutions for public transport systems. The company has set ambitious environmental goals and buying the biogas electric hybrid bus is a result of VL’s objective to increase energy efficiency in the biogas buses. VL ordered the biogas electric hybrid bus from the Polish company Solaris, at the same time as ordering other, conventional biogas buses. The hybrid bus was designed to be identical to the new biogas buses, except for the driveline and heating system. This means that the energy efficiency of the hybrid bus easily can be compared with the efficiency of the biogas buses.
Figure 3. The almost finished biogas electric hybrid bus in the Polish factory. Source: Västerås Lokaltrafik.
The developing of the hybrid bus was carried out in close dialogue between Solaris and VL. VL gave input on how to develop the heating system as well as how to adapt the bus’s function and technique to Swedish conditions. The collaboration was enhanced by representatives from VL travelling to Solaris in Poland for common meetings and for visits in the factory.
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3. Piloting the new hybrid bus The biogas electric hybrid bus, named Solaris E12 Hybrid, is a pilot project that is being tested in regular traffic in Västmanland’s public traffic system. Below is a list of technical specifications of the hybrid bus: -
The hybrid bus is 12 meter long.
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Has an electric traction system with 160 kW traction motor TSA and 160 kWh Li-ion batteries Solaris.
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Has a CNG/biogas based heating system with 30 kW preheater and two CNG tanks à 214 litres.
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Takes 31 passengers.
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Weighs 18 000 kilograms in total.
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100kW fast charging with ”plug-in” at the Västerås depot. Time needed for depot charge is 2-3 hours, which allows about 5 hours operation in city traffic.
The biogas heating system allows all of the battery capacity to be used for driving the bus, which improves the range. The batteries are therefore also smaller and have a lower weight compared to a vehicle where both drive and heating/cooling runs on batteries. The separate biogas heating system also lowers the pressure on the electrical batteries during cold winters. VL has long been working with eco-driving and achieved positive results with the biogas buses. The eco-driving system, Pilotfish, is installed in the hybrid bus as well, with necessary adaptions (e.g. the electricity being generated when braking).
4. Comparison between the hybrid bus and conventional buses The hybrid bus has been tested in regular traffic since its arrival in Västerås. Continuous monitoring will be carried out after the end date of the project and the evaluation will be updated with time, as more data becomes available. The results from the comparison of the new bus and conventional buses should thus be viewed as indicative.
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Electric hybrid bus
Biogas bus
Diesel bus
Fuel consumption
0,12 Nm3/km biogas
0,46 Nm3/km biogas1
0,45 liter/km
Energy factor1)
9,7 kWh/Nm3
9,7 kWh/Nm3
9,8 kWh/liter (Nm3)
Energy use
2,12 kWh/km
4,46 kWh/km
4,41 kWh/km
Cost/km
1,1 kr/km biogas
4,4 kr/km
4,3 kr/km
0 kg/Nm3 biogas clean biogas
0 kg/Nm3 clean biogas
2,41 kg/l3)
1,6 kg/Nm3 mix of biogas and natural gas2)
1,6 kg/Nm3 mix of biogas and natural gas2)
0,96 kWh/km electricity
0,96 kr/km electricity 2,10 kr/km total
CO2 factor
0 kg/kWh electricity
CO2/km
0 kg/km clean biogas and electricity 0,19 kg/km mix of biogas and natural gas, electricity
0 kg/km clean biogas
1,08 kg/km
0,74 kg/km mix of biogas and natural gas
1) Source: Energimyndigheten, i.e. National Energy Authority Sweden 2) Source: Institute of Energy and Transport , EU 3) Source: Svenska Petroleum & Biodrivmedel Institutet
The table presents the fuel consumption, energy use, costs and CO2 emissions of the hybrid bus, biogas buses and diesel buses in VL’s fleet in December 2014. The figures in the table are results of VL’s measurements, if nothing else is stated as a source. The energy content in one cubic meter gas corresponds approximately to one liter diesel. Results show that the fuel consumption and energy use of biogas buses and diesel buses are similar, while the CO2 emissions of the biogas buses being significantly lower. Comparisons between emissions from normal diesel buses and biogas buses
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Biogas: the methane gas used by VL buses mostly contains 100% biogas. The gas used by VL contains some part fossil gas at times. 7 www.balticbiogasbus.eu
made in the Baltic Biogas Bus project show that using biogas as fuel instead of diesel also decreases NOx emissions. Results also show that the biogas electric hybrid bus is twice as energy efficient as the conventional buses and has substantially lower fuel consumption. The hybrid is therefore also much cheaper to operate in city traffic and has significantly lower CO2 emissions. In the hybrid bus electricity is used for the driveline instead of biogas. The end-ofpipe-emissions from operating the bus with electricity of course zero. To achieve zero or near-zero emissions from a life-cycle perspective, it is of course of outmost importance to use clean electricity, i.e. electricity from renewable sources. About 50 percent of a bus’ total energy need during the winter is used for other purposes than propelling the bus, especially for heating. In conventional biogas buses and diesel buses, the heat is provided from the combustion engine, which means that during summer season, this energy is not used. In the electric hybrid bus, no biogas will be needed for heating the hybrid bus during summer, and this energy can thus be saved. This results in the energy used for heating the hybrid bus being zero when no heating (or cooling) is needed. . Another environmental advantage with the hybrid bus is silence. The quiet hybrid bus decreases noise levels in the city and reduces hazardous impacts on people’s health due to noise. When purchasing the biogas electric hybrid bus, it is more expensive than conventional biogas buses. VL’s expectations are though that operational costs will be lower, as fuelling is cheaper, maintenance is cheaper or similar to conventional buses, and the lifespan is similar to or longer than that of conventional biogas buses. The positive economic development over time for biogas as fuel in buses is due to new gas buses having more efficient engines and lower maintenance costs. A same kind of development can be topical for hybrid buses as well in the future, which will lower the costs for hybrid buses. Maintenance intervals for the driveline of the hybrid bus are estimated by supplier to be every 500 000 kilometers. This is to compare to the interval for biogas buses’ engine with 15 000 kilometers. The maintenance cost is though analysed in this report due to the short operating time of the bus. Expectations though that the maintenance costs will be lower for the hybrid bus than for conventional buses.
the the not are the
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5. Users’ experience Drivers and passengers’ impressions on the biogas electric hybrid bus give valuable information for the monitoring and evaluation efforts on the operation of the bus in practice.
Figure 4. Functions of the bus are being presented by the bus driver on the press release. Source: Jonas Forsberg.
Drivers and technical staff at VL have participated in a training course on the maintenance of the bus and on how to drive and charge it. The course was held by Solaris, with particular focus on the safety issues concerning the electricity use in the bus. Even though the actual driving function is similar in the hybrid bus as in conventional buses, VL’s drivers appreciate the hybrid bus since it feels easy and flexible to drive. The engine is strong and runs smoothly. The bus has a good torque and ground traits that make the bus well suited to city traffic. One driver even refer driving the hybrid biogas bus to driving a tram. Since trips with the hybrid bus is not as rough or bumpy as with conventional buses, the hybrid bus contributes to better trips for its passengers. The hybrid bus also has good instrumentation that is easy to read and understand. The heating system has so far been functioning very well.
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People have approached the bus and given positive comments on the silence of the bus. Passengers have also responded positively on VL’s investment in this new kind of hybrid bus with less environmental impact than conventional buses.
Figure 5. The hybrid biogas bus was introduced in Västerås with a press release in December 2014. Politicians, civil servants, journalists and representatives from VL participated on a trip with the bus in the city centre of Västerås. The responds of the participants were positive: the bus helps fulfilling the environmental goals of Västerås by allowing a better air quality and a better noise level in the city. An article on the hybrid bus was presented in Västerås’s local newspaper Vestmanlands Läns Tidning. Source of picture: Jonas Forsberg.
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6. Spin off The Baltic Biogas Bus project and the biogas electric hybrid bus have been important stepping stones in VL’s proceeding work on improving the technical and environmental performance of its bus fleet. In the proceeding evaluation of the biogas electric hybrid bus, VL will focus on: - Clean electricity as power to the hybrid bus - Inductive charging at bus stops that would lead to smaller batteries and cheaper buses - Additional traffic safety analysis - Replacement scheme for diesel buses, to replace them with biogas buses, hybrid biogas buses or electric buses - Maintenance costs of the hybrid bus - Driveline of the hybrid bus - Charging capacity of the hybrid bus Biogas electric hybrid buses together with these kinds of solutions are seen by VL to be the future of public transport systems.
7. Conclusions The new biogas electric hybrid bus is energy efficient, has lower fuel consumption and has lower CO2 emissions. At the same time as is cost-effective, and indications are that the bus will not be more costly than conventional biogas buses and diesel buses. Drivers and passengers appreciate its flexibility, silence and lower environmental impact. Proceeding evaluations of the biogas electric hybrid bus will give a foundation for further improvements of the bus’s and VL’s bus fleet’s technical and environmental performance in the future.
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