Hydrogen Fuel Cell Bus Technology State of the ... - NEXTHYLIGHTS

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Hydrogen Fuel Cell Bus Technology State of the Art Review Each of these problems will need to be overcome if fuel cell buses are to occupy the „environmental bus technology‟ space currently occupied by diesel hybrid buses. Electric buses have a number of apparently fundamental limitations which will prevent their widespread adoption. In particular: The slow recharging time for the buses The high power demand for charging- which will increase the cost of charging infrastructure at bus depots The high weight of the batteries Limited range – below that required for a typical cycle These limitations would rule out a fully autonomous battery powered bus, providing, for example, an 18 hour route. There are however new options being developed which could include more limited battery capacity (or super capacitors) with fast charging at bus stops or layover areas (Figure 24, below). These could include inductive charging or small plug-in stations for short bursts of charge. Such technologies have still to be extensively tested in commercial applications and hence it is not possible to perform a comparison with fuel cell buses at present. Figure 24 Examples of an ultra-fast charging station for ultra-capacitor-powered buses (left) and a fast charging stations for battery-powered buses (right). Ultra-fast charging points recharge the buses in few seconds at each bus stop, whilst fast charging points recharge the buses at the route end only. Sources: http://ceramics.org ; http://www.proterraonline.com. Finally, it is possible to remove the batteries all together and move to a trolley bus architecture. Trolley bus systems offer a highly reliable zero emission solution. However, the drawback is the high cost of the overhead cabling infrastructure (approx. €400,000 - €1,000,000 per kilometre including substations) and the fact that the trolley bus will be fixed to particular routes limiting operational flexibility. The trolley bus architecture is therefore mainly deployed on short, heavily used inner city routes. 56
Hydrogen Fuel Cell Bus Technology State of the Art Review Table 10 Comparison between bus technologies. Colours legend: red = worst performance in comparison with benchmark (diesel buses); yellow = slightly worst performance; light green: slightly improved performance; green = better performance. A white box means absence of data or similar performance. 12m bus platform Operating benchmark Capital Cost Basic diesel bus: Approx. €170,000 - €300,000 Observed Fuel Economy figures (in urban route). Please note that fuel economy figures depend on driving cycle Diesel bus: 0.35 - 0.5litre/km (~ 3.5 – 5kWh/km) Fuel Cost ~ €0.35 – 0.5/km (assuming a taxed diesel fuel cost of €1/litre) Range ≥ 500 km (for urban service) In-Tank Energy Capacity to Weight ratio (Energy Storage System plus Engine) Bus Availability ~ 90% ~ 3.5 kWh/kg (assuming 280kg of diesel on board and a 200kW engine) Refuelling time ≤ 0.1 seconds/kWh Pollution from Exhausts CO, NOx, SOx, PMs CO2 emissions 1.15 – 1.6 kg-CO2/km (diesel fuel carbon content: 2.3kg/litre) Propulsion system durability Diesel engines have a life of approx. 7 years in heavy duty applications Approx. ≥ €1 million Battery Hybrid Fuel Cell Hybrid Diesel Trolley Approx. €1.2 - €1.8 million NA (under testing) Up to 40% improvement over an equivalent diesel route at parity of calorific content NA (under testing – it depends on actual fuel economy) ~ €0.32 – 0.9/km (assuming a hydrogen fuel cost ~ €4- 6/kg) Approx. €350,000 (serial) €500,000 (first-of-a-kind models) Up to 25% - 30% improvement over an equivalent diesel route ~ €0.23 – 0.4/km (assuming a taxed diesel fuel cost of €1/litre) < 100km Up to 500km Equal to diesel buses -- ~ 0.08 – 0.12kWh/kg ~ 1 kWh/kg (assuming 35kg of H2 on board and a 150kW FC system) NA (under testing) 55% - 80% (diesel equivalence expected for next generation buses) Up to 15 seconds/kWh (using industrial conductive recharging points) ≤ 0.45 seconds/kWh (assuming 40kg of H2 on board at 350bar) Similar to diesel buses -- 57 Approx. €500,000 - 600,000 (cost figures for western European markets) Up to 50% improvement over an equivalent diesel route ~ €0.18 /km + 20% (assuming a taxed electricity cost of €0.1/kWh) Similar to diesel buses Similar to diesel buses Equal to diesel buses -- Absent Water vapour only CO, NOx, SOx, PMs (up to 30% reduction over benchmark) Depends on the electricity carbon content. Up to 100% reduction over benchmark (e.g. renewable electricity) NA (under testing) The battery system for heavy duty application, however, has a typical warranty of 2 -3 years. Infrastructures -- Need of recharging infrastructures (at bus depots or along the bus route) Depends on the hydrogen carbon content. Up to 100% reduction over benchmark (e.g. renewable hydrogen) The fuel cell systems for heavy duty application have a typical warranty of 10,000 – 15,000hours (or 5 years). Battery: 2 -3 year warranty. Need of hydrogen refuelling infrastructures (at bus depots) and delivery networks Up to 30% reduction over benchmark Extra maintenance required by the hybridelectric drivetrain. Battery: up to 5 years warranty. Absent Depends on the electricity carbon content. Up to 100% reduction over benchmark (e.g. renewable electricity) -- Need of overhead contact wire networks throughout all bus route --
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