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TECHNICAL COLUMN Alernative powertrains and fuels - with Ray Brown Throughout a series of articles this year we have reviewed a number of new technologies, which are used within the conventional motor vehicle utilising conventional fuels. This article will look at the latest and emergent technologies for alternative powertrains and fuels in response to the necessity to meet Greenhouse emission policies by reducing carbon dioxide emissions and increasing energy sustainability using renewable resources. ALTERNATIVE POWERTRAINS Flexible Fuel vehicles (FFV) A Flexible Fuel vehicle is an alternative fuel vehicle with an internal combustion engine designed to run on more than fuel, usually petrol blended with either ethanol or methanol, stored in a common fuel tank. Flex-fuel engines are capable of burning any proportion of the resulting blend in the combustion chamber, as fuel injection and spark timing are adjusted automatically according to the actual blend detected by electronic sensors. Though technology exists to allow ethanol FFVs to run on any mixture of petrol and ethanol, from pure petrol up to 100 percent ethanol (E100) North American and European flex-fuel vehicles are optimised to run on a maximum blend of 15 percent petrol and 85 percent ethanol (E85). This limit in ethanol is set to reduce ethanol emissions at low temperature and to avoid cold starting problems. The model T Ford was the first commercially available flex-fuel vehicle. The engine was capable of running on petrol or ethanol or a mix of both by adjusting the mixture screw on the carburettor. Holden have already announced that they will introduce a flex-fuel Commodore in 2010, which will run any ethanol blended fuel from E10 to E85, but also run on normal petrol should the need arise. E85 is not widely available in Australia as yet, but as usual, the market is expected to respond to any increased demand. V8 Supercars made the switch to E85 at the beginning of the 2009 season. Hybrid vehicles A hybrid vehicle is one that combines two or more sources of power that can directly or indirectly provide motive power. Most hybrid cars on the road are petrol x electric vehicles although some manufacturers have announced plans for diesel x electric hybrid cars. Combining the power sources of a conventional engine and electric motor can be done in two ways. For a parallel hybrid, both the engine and electric motor turn the transmission at the same time to power the wheels. In a series hybrid, the conventional petrol engine turns a generator that either charges the on-board batteries, or powers the electric motor, which powers the wheels. Using advanced electronics the electric motor can act as a motor as well as a generator. The key to the performance of a hybrid car is that the petrol engine can be smaller than that found in a conventional car, as the operation of the engine can be optimised for maximum efficiency and, when accelerating, the electric motor can be called upon for support. The Toyota Prius is a parallel hybrid vehicle but with the addition of Toyota Hybrid System (THS) provides some of the benefits of a series hybrid. THS is a power split device using a planetary gear set, which optimises efficiency and reduces emissions by allowing the engine to stay within its most efficient load and speed range. It allows the car to operate as a parallel hybrid – the electric motor or the engine can power the car by itself, or they can both power the car. This device also allows the car to operate like a series hybrid, in that the engine can operate independently to vehicle speed charging the batteries or providing power Readers are invited to send technical enquiries of a general nature to brownrc@bigpond.net.au to the wheels as needed. The planetary gear set eliminates the need for a transmission and allows the generator to start the engine so no starter motor is required. Plug-in hybrid vehicles Plug-in hybrid electric vehicles (PHEVs) are hybrid cars (HEV) with an added battery. As the name suggests, plug-in hybrids – which perform and look like regular cars – can be plugged into to a 240-volt outlet and charged. Plug-ins run on stored energy for much of a typical days running – depending on the size of the battery, up to 100 Km per charge – and when the charge is used up, automatically keep running on the engine. Toyota, General Motors, Ford, Volkswagen and Volvo have scheduled introduction of production of PHEVs from 2010 onwards. The General Motors Chevrolet ‘Volt’, due for introduction into the market during 2010, is an example of a plug-in hybrid vehicle. This global compact vehicle will have a 120kW electric drive motor with lithium-ion battery pack of 136 kW peak power, a 53 kW generator and a 1.0L, 3-cylinder turbocharged engine. The vehicle platform has been designed as a modular concept to accommodate a range of energy sources to meet the specific needs and infrastructure of a given market. Energy sources include fuel cell providing electricity supplied by hydrogen, full batteryelectric using grid charging or a multiplicity of fuel types to power the range extending internal combustion engine. Mercedes Benz concept ‘blueZERO’ also utilises a modular design approach for its PHEV. PHEVs have the potential to enhance electrical generation and demand. Electrical demand varies greatly; demand is generally high during the day and low at night. Charging PHEV batteries at night would take advantage of low demand. As vehicle-to-grid capabilities are developed, PHEV battery capacity could also be used to help meet peak electricity demands. PHEV owners would charge their vehicles while demand and electricity prices are low, and when their vehicles are idle, sell electricity back to the grid when demand and prices are high. This may allow utilities to avoid building extra generation capacity to meet peak demands. FIG 1: Mercedes Benz ‘blueZERO’ modular concept for Electromobility 20 AU T O M O T I V E A F T E R M A R K E T M AG A Z I N E D E C E M B E R 2 0 0 9 www.aaaa.com.au
TECHNICAL COLUMN Alternative fuels The long-term objectives of alternative fuels for automotive use are sustainability and greenhouse gas reduction and therefore little is gained by looking at fossil fuels except where these are in abundant supply relative to the availability of oil. With the diversification of fuels available, it is necessary to consider the complete ‘fuel’ chain to understand the total impact on the environment from production, processing, transportation, distribution etc through to the use in a vehicle. One such study was conducted by Toyota in conjunction with Mizuho Research Institute to estimate Greenhouse Gas Emissions (GHG) on a “Well to Wheel” (fuel extraction through to power at the wheels) basis for many different fuel types. Using an index of 1 for petrol, some of the results are very interesting. For example a petrol hybrid is 0.45 (lower score means lower GHG impact), a diesel hybrid about 0.35, LPG and CNG are approximately the same at 0.8, for electricity produced by coal 1.2 (worse than petrol) whereas for nuclear power generation the result is 0; ethanol produced from sugar cane 0.2 and synthetic diesel produced from biomass 0.1. A fuel cell using CNG is 0.4 whereas a fuel cell using liquid hydrogen is 0.2. Apart from Greenhouse Gas Emissions, other factors that must be considered to establish the viability of an alternative fuel include cost, infrastructure, supply potential and usability which will now be examined in more detail for fuel types which are the most likely to meet these criteria. Ethanol Ethanol, also known as Ethyl Alcohol, is a clear and colourless liquid, which is produced from vegetable and plant based materials. Today most ethanol is produced from starch and sugar based feedstock such as corn, sugar cane etc. Given the potential impact on food production, much research is being undertaken to use cellulosic feedstock. Cellulosic feedstock includes agricultural and forest residues, grasses, municipal waste and trees. The reason that ethanol scores so highly in the “Well to Wheel” index is that the carbon dioxide used to convert feedstock to ethanol is a little more than the carbon dioxide captured by the crops during growth. Ethanol works well in internal combustion engines as it is a highoctane fuel, suitable for high compression ratio engines, but contains about 34 percent less energy than petrol. Low-level blends such as E10 (90 percent petrol, 10 percent ethanol) are readily available in Australia and high level blends up to E85 (85 percent ethanol, 15 percent petrol) are available in countries such as USA, Brazil and Sweden. Synthetic diesel Synthetic diesel is a method of producing diesel fuel from natural gas, which is one Earth’s cleanest and most abundant natural resources. Synthetic diesel is made by using a conversion technology called the Fisher-Tropsch process, which converts natural gas into the synthetic diesel, which can then be used in any petroleum diesel fuel application. Synthetic diesel provides numerous economic and environmental benefits over typical petroleum diesel. First of all, synthetic diesel is sulphur free and free of other petroleum by-products. This means that synthetic diesel is significantly cleaner, cleaner burning and can be formulated for superior cold weather performance and fuel system lubricity. Because synthetic diesel has fewer contaminants, it is lower in toxicity and it also has a higher cetane rating, like octane for petrol, it offers better performance over regular petroleum diesel. Synthetic diesel can be blended with standard diesel and stringent diesel exhaust emission standards are compelling the petroleum industry to revisit FIG 2: Mercedes Benz ‘B’ Class Fuel Cell vehicle synthetic diesel to competitively produce aromatic and sulphur complying diesel fuel. Since the late 1990’s nearly every major oil company announced plans to build pilot plants or commercial plants to produce synthetically derived diesel fuel. Shell is currently building the largest gas to oil refinery in the world in Qatar, and when completed, will have a capacity of 140,000 barrels/day of diesel and other products. Fuel cells Fuel Cells have been extensively used throughout the space program and many vehicle manufacturers believe that fuel cells are the technology of the future. Mercedes Benz will release a limited production version of a fuel cell ‘B’ series next year as will Honda with the FCX Clarity. Fuel cells convert the chemical energy in hydrogen to electricity, with pure water and potentially useful heat as the only by-products. Hydrogen powered fuel cells are not only pollution free, but also have more than twice the efficiency of traditional combustion technologies. A combustion-based power plant generates electricity at efficiencies of 35 percent while fuel cells are up to 60 percent efficient. The conventional automotive engine is around 20 percent efficient in converting the chemical energy of petrol into power at the wheels. Hydrogen fuel cell vehicles, which use electric motors, are much more efficient using 40-60 percent of the fuel energy. There are a number of ways that hydrogen can be provided to the fuel cell. Hydrogen gas can be stored as a gas or liquid hydrogen but to carry gaseous hydrogen it must be compressed at very high pressures in special fuel tanks similar to compressed natural gas. Liquid nitrogen, used in the space shuttle, is super-cold so the fuel tank would need to cope with high pressures and be super insulated. Another way to provide hydrogen to the fuel cell is to use a ‘reformer’. A reformer is a device that removes the hydrogen from hydrocarbon fuels, like methanol, natural gas, LPG or petrol. When a fuel other than hydrogen is used, the fuel cell is no longer zero emission, but still very low emitting. The challenges facing fuel cell development are to reduce cost and improve durability to cope with the dynamics and vibration of a motor vehicle. In addition, the distribution costs of hydrogen on a large scale to fuel motor vehicles will be prohibitive and it is likely that initial use of this technology will be via the use of an onboard reformer using methanol, natural gas or LPG as the fuel. Whilst highly speculative, a 100 year forecast of automotive fuel supply by General Motors and Shell shows that petroleum based fuels will continue to dominate energy demand (around 78 percent) until 2050, By the end of the century, petroleum based fuel energy demand will drop to around 25 percent whereas synthetic fuels and bio-fuels will account for 50 percent and hydrogen/electricity will meet the other 15 percent. AU T O M O T I V E A F T E R M A R K E T M AG A Z I N E D E C E M B E R 2 0 0 9 21
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