Green technologies hit fast forward

The drive for alternative automotive fuel sources means that motor vehicle technology is going through an exceptional rate of technical development and change. Hybrid and battery electric vehicles are becoming more and more commonplace and advances are taking place not only with regard to electric drives, but also alternative fuels and components such as turbochargers, with huge consequential improvements in power and performance per unit weight as well as enhanced fuel economy. However, while some still see fuel cells as a way forward, and battery electric delivery vehicles are definitely the solution of choice for short runs with lots of stops and starts, it would seem that the internal combustion engine is likely to remain the power plant of choice for most vehicles, albeit in a greatly improved form. Jason King, the chief engineer of Ricardo, described at the recent Cenex LCV 2010 event at Millbrook how he expected the HyBoost project to reduce the carbon emissions of a two litre Ford Focus engine from 169g/km to 99.7g/km, and hopefully to the 89g/km achieved by the hybrid Toyota Prius, but at much lower cost. A crucial part of the development is an electrically-driven supercharger which we assume to be the VTES (Variable Torque Enhancement System) supercharger made by collaborating company, Controlled Power Technologies (CPT). The turbine is driven by a switched reluctance motor and can accelerate from idle to its maximum speed of 70,000 rpm in less than one third of a second. CPT recommends using their electric superchargers in series with a conventional supercharger. The VTES technology can also be used to reduce soot and particulate emissions from diesel engines. Supercharged design An alternative suitable supercharger for such projects could be the 'TurboClaw' being developed by Dynamic Boosting Systems, a spinout from Imperial College, London. Invented by DBS founder and managing director Dr Shahram Etemad, it uses a flat impeller with a very high forward sweep. Dr Etemad said that the design delivers the same amount of air at 50,000 rpm as a conventional centrifugal turbo impeller delivers at 100,000 rpm. Using a software model developed by AVL Powertrain, he said it should allow a one litre engine to have the performance of a conventional 1.4 litre engine. According to Rik Alewijnse, design team leader with AVL Powertrain, the design also has other applications because: "It sits in the design space between a screw compressor and a centrifugal turbo impeller in terms of mass flow and speed", adding that its shape is easily injection mouldable, because it is flat, instead of being three dimensionally curved. Efficiency comes, he said, because, "There is no pressure rise in the impeller, it all happens in the diffuser." Another aspect of the Hyboost project involves having a starter/generator. One of the participants is Valeo, which makes the StARS - (Starter Alternator Reversible System). An improved starter/generator system that allows drivers to change their minds about stopping in traffic is the 'SpeedStart' developed by CPT. With a conventional starter motor adapted for stop/start, the engine cannot be prevented from shutting down when rpm drops below a certain speed, prior to restart. With the new system, the driver can leave the vehicle in gear in gear and no matter how low the engine rpm, an instant restart is achieved by simply coming off the brake pedal, in less time than it takes the driver to move their foot to the accelerator. To achieve this, the company uses a liquid-cooled, switched reluctance machine which generates peak currents of 205A, a maximum continuous output of 2.7kW and has a starting torque of 72Nm. Response time to establish full current in its windings is less than 10ms. It is claimed that the stop/start capability provides a 3% to 5% reduction in CO2 emissions. The increased efficiency of the switched reluctance machine gives a further 1%. If additionally used to provide regenerative charging during vehicle deceleration, this provides a further 3% to 5%. Stop-start system Also on display at the event was a Ford Transit van equipped with an Ashwoods Automotive retrofit system as well as one of the company's hybrid add-on transmissions. The company claims that the stop-start system can be fitted by a competent mechanic in less than an hour and reduces fuel consumption and emissions by 5% to 10%. It shuts down the engine when the vehicle is at rest, and automatically restarts the engine when the drive pushes the clutch pedal. The add-on hybrid transmission takes power from and delivers power to the rear differential via a pulley and toothed belt which drives and is driven by a permanent magnet brushless motor generator. When the brakes are applied, energy is taken from the transmission to drive the motor generator to produce power which is stored in a lithium ion battery within an intelligent power pack module beneath the sliding door. During acceleration, power is drawn from the battery and sent to the motor generator to assist acceleration. Detection of braking, accelerator position and speed is achieved by plugging into the vehicle CANbus. A simple dashboard display shows what is happening and suggests changing gears up or down to improve fuel economy. Fuel and carbon savings are said to be 15% to 25%, depending on the vehicle drive cycle. The vehicle drives like a normal transit and should the system fail, it reverts to being a conventional vehicle. One of its big attractions is that it requires no hole drilling or other vehicle modification, attaching to holes that are already there. This ensures that there is no effect on vehicle warranty. The retro fit stop start similarly has no effect on vehicle warranty. Ford has endorsed the system and Ashwoods managing director Mark Roberts told us that the system is to be offered through a number of Ford dealerships. It takes about four hours to install. Since its launch in 2009, more than 130 hybrid equipped vans have been delivered. The Department of Transport recently selected Ashwoods as the sole supplier of more than 130 hybrid vans for its Low Carbon Vehicle Procurement Programme (LCVPP), managed by Cenex. Roberts said that this had allowed them to reduce the cost of the system by 10%. I expect costs to reduce by 25% when sales hit 500 vehicles – at which point it will make sense for the man in the street to buy one." Most of the other vehicles at the LCV event were demonstrating either battery electric propulsion or use of alternative fuels. Roberts said his business originally started out doing conversions to use liquefied petroleum gas, but he did not see much future in this. Much more future is seen in using methane, either in the form of compressed natural gas or biogas, or biologically derived methanol and ethanol. Lotus has a demonstrator sports car that can run on either gasoline, methanol or ethanol, but use of ethanol may be criticised on the grounds that it presently comes from agricultural products, reducing land available for growing food and encouraging the cutting down of forests. Methanol is mostly made from natural gas, so it makes sense to use natural gas directly. Natural gas is mostly methane, but so is biogas, which offers the advantage that it can be made by fermenting waste organic matter out of the presence of air, and is a natural product produced by most rubbish dumps. The difference is that biogas is only about 60% methane, whereas natural gas as delivered is usually about 95%, although engines can be made to run on either. There are more than 125,000 biogas digesters in Nepal, more than two million in India and around five million in China. Most are used to produce gas for cooking as an alternative to wood or fossil fuels. However, they show the real practicability of moving to a methane-based mechanical economy, rather than the idea of a hydrogen-based economy, with hydrogen consumed in fuel cells. The big problem with hydrogen is that when used for fuel cells, it has to be extremely pure, and is mostly made by the steam reforming of natural gas. The fuel cells also remain prohibitively expensive at the present time and are likely to remain so for the immediately foreseeable future. India is moving towards increasing the number of vehicles running on compressed biogas. The Indian Institute of Technology Delhi has a patent on a new process for increasing the methane content to around the 95% methane normally found in natural gas. A number of companies in the UK are currently running delivery vans on biogas-derived methane using systems and fuel supplied by Gasrec, which supplies liquid 'biomethane', produced by processing biogas so as to improve its quality as a fuel. Equipment to produce and process biogas is sold by, among others, Biogas Products, based in Warley in the West Midlands. According to the company's Tony Smith, they supply Danish made 'BioGasclean' scrubbers to remove hydrogen sulphide, which is essential if the gas is going to be used in engines, and Italian made membrane gas holders. At the LCV event, Sean Hill of GENeco brought a VW Beetle converted to run on biogas derived methane by the Greenfuel company in Bath. The car is started using petrol and when the engine is up to temperature, the system automatically switches to methane. The remaining sector of low or zero carbon vehicles are those running on rechargeable batteries. Battery electric fork lift trucks and milk floats have been in use for decades. China has announced that it intends to spend $15 billion to develop new hybrid and electric vehicles. A quick search on alibaba.com shows 3,492 different electric car offerings from Chinese manufacturers and recent visitors report large numbers of electric vehicles on the streets of Chinese cities, including around 120 million electric bikes. The main limitation to their greater use in the West is the batteries. Lead acid batteries have an energy density of 30 to 40Wh/kg whereas lithium ion batteries have an energy density of 100 to 250 Wh/kg but they cost more. Nonetheless, both Allied Electric in Glasgow uses lithium-ion for their Peugeot derived vans and people carriers as does Smith Electric Vehicles for their Ford derived vans, minibuses and small trucks. Both Allied Electric and Smith Electric Vehicles claim 100 mile ranges for their products and Johnny Swinhoe, mechanical design engineer with Smith Electric Vehicles insisted that they were economically viable, despite the cost of the batteries. Swinhoe says that the electric drive train for the company's 'Edison' panel van and minibus uses a 90kW induction motor and battery packs with capacities from 36kWh to 50kWh. When we asked whether that meant that endurance might be rather short, he explained that the 90kW is the peak draw – most of the time the power consumption is a lot less, and energy is also routinely recovered during regenerative braking. Smith Electric Vehicles US has announced an order for 176 120kW 7.5-12 tonne 'Newton' electric trucks from snack food company Frito-Lay. While most of the presently commercially viable electric vehicle projects in Europe seem to involve delivery vans, Siemens, working with Ruf Automobile has developed a 'Greenster' electric sports car based on a Porsche 911. It has a 270kW motor producing 950Nm torque and can reach 142mph. It has a range of 125miles and can be charged in less than an hour from a 400V outlet. 0 to 100km/h takes 5s. The 205 mph C-X75 hybrid supercar that Bladon Jets in Ellesmere has been developing with Jaguar. At its heart are two mid-mounted micro gas turbines that can either charge the car's batteries or provide supplementary power to the electric motors.