While production at Lotus remains a traditional, hands-on affair, the company’s engineering division is looking at the potential of methanol as a renewable fuel
Play the association game with automotive terms and ‘handbuilt’ invariably ends up paired with ‘Rolls-Royce’. But this quintessentially British (yet German-owned) company is not the only UK-based carmaker to eschew robotics in favour of hands-on attention to detail. Lotus Cars, also believes that this is the right way to go about building its 3,000 cars each year. In an age where automation is put forward as being the only way for a modern car company to make money, the investment is paying for itself with improved economies of scale, the production line at Lotus is noteworthy for the complete absence of robots. From the gluing of the two-piece clamshells that wrap the front and rear of the cars to the on-line calibration of steering geometry, everything on the Lotus production line is completed manually. And, not to put too fine a point on it, this involves a lot of work. With the space used for the company’s second production line currently home to the fenced-off development area for the latest Lotus model, referred to only as ‘Project Eagle’, all four of the current Lotus models (Elise, Exige, Europa and 211) are being produced on just one line.
Federalising the car
“The guys on the shopfloor are dealing with 40 minute takt times,” says Iain Snary, Lotus’s Manufacturing Engineer Manager. “The next car might be a different product with its own 40-minute takt time process, with further possible process changes to accommodate the market-specific components based on territory requirements.” What Snary is talking about here are changes to cars that will be shipped to overseas markets to meet local regulations – what you might call the ‘federalisation’ of the car. These are completed on the production line, further adding to the complexity. “We federalise all our cars during the standard build process, nothing is done locally in the USA,” Snary explains. Indeed, the variation in models running on the same production line has, according to Snary, forced a rethink in the lineside delivery structure.
“We’ve a variety of continuous improvements being carried out on the production line, from a standpoint of leaner manufacturing, in terms of waste, while being a lot smarter in how materials are presented lineside, particularly as we’re building off only one line. With all the products coming off the same line, certain line stages are very tight in terms of materials presentation, so we’ve been reviewing what’s sensible when looking at kitting of parts, for example.” Despite the lack of automation, many of the carmaking processes, including quality checks, are similar to those found in automated facilities, the majority of which were instituted when this current production line was being developed. “The facility we’re in at the moment was built eight years ago, initially for the Vauxhall VX220/Opel Speedster; the first in Vauxhall’s VX-badged range of products,” says Snary. “GM had very specific quality standards for this model, which we had to meet, but when the Mark II Elise was put into production it benefited from those improvements.”
While Lotus does fabricate parts in-house, the construction of other key components is outsourced to third-party companies. For example, almost all the resin transfer moulded (RTM) panelling, including the front and rear clams, rear panel and all the closures (doors, boot lid and bonnet), are manufactured by SOTIRA (Les Societes de Transformation Industrielle de Resines Armees) in France. Made from a sheet moulding compound that either has resin in the sheeting or has resin injected into the mould, the rough panelling is shipped to Hethel for final preparation and painting. “We’ve made carbon fibre structures for other manufacturers, such as Aston Martin, but we don’t currently use this material on our standard Lotus product range,” explains Snary.
Was the outsourcing of these parts by design or by default? “A bit of both, though in the main, it’s by design,” says Snary. And the choice of suppliers? “Because of the volumes we produce, our hands are sometimes tied commercially as to which suppliers we use.” The search for suitable parts suppliers has taken Lotus around the world. “We’re now sourcing things globally, windscreens are coming from South America (Peru) and quite a few parts are coming from China, India and South Africa.” Similar to panelling, Lotus chassis fabrication is also outsourced, the work completed by what was formerly HoldenHydro (Holden Lightweight Structures Limited) and is now Lotus Lightweight Structures Limited, the company having been purchased by Lotus in May this year. David Jenkinson, Materials and Process Technologies Manager explains: “It’s the chassis that has made (our) products such a success. It features stiffness, strength and overall function. A part can be said to be successfully designed when it performs more than one function. The chassis does this, carrying both the suspension and body, while still retaining crash characteristics.”
Safety in hand
Chassis and panelling apart, many of the remaining components are manufactured in-house, including the rear subframes (fabricated steel which is then galvanized), suspension wishbones, rear diffuser panels and a variety of underpinnings and internal brackets. Also constructed in-house is the front crash assembly, the importance of which Jenkinson is keen to point out. “We’ve invested a lot of research and development budget into developing the front crash structure, discovering the best way to layer and form the fibre (material) to achieve the desired ‘progressive crashability’. The unit is designed to deform in a predictive manner. In an impact, it is able to absorb energy over its whole length, yet its material structure, reduced weight and small size allows greater flexibility in packaging space, translating to a smaller front overhang in comparison to a vehicle using steel for the same crash structure.” Like the front crash assembly, Lotus constructs seats for all its models. “Once we had fulfilled the contract to produce composite structures for Aston Martin’s V12 Vanquish, we decided to fill that capacity by bringing production of the seats back in-house,” says Snary. Made of GRP, the body of the seats is made using an RTM injection process, with all covers and stitching completed in a dedicated trim shop. “We’ve recently added ProBax inserts to all our seats,” adds Snary. “These correct the driver’s posture, positioning the legs correctly and improving circulation. Our research has shown that over long distances, poor circulation is a major contributor to tiredness and we think ProBax can help improve long-term driver comfort.”
Preparing for production
One of the few automated processes in the production process is the robot water-jet cutting of some of the panels manufactured in-house. “We have robots for these intensive operations,” says Jenkinson, “and for other procedures that demand high-tolerance cutting and joining.”
Once the panels have been trimmed and cleaned, the sections are then bonded. “Our glues are not epoxy based,” says Snary. “We use a variety of structural adhesives to bond the various materials and sections of the vehicles. Currently we use a Plexus product for the bonded body assemblies, and a Betamate product is used to secure bodyside panels and crash structure assemblies to the chassis. Depending on the adhesive and required process time, some bonded joints require heat curing. Selecting the right adhesive for its application is key and we always follow a robust testing and validation programme for any new application.”
While the panels are being prepared the car on which they will be fixed is making its way along the production line. In contrast to most automated vehicle manufacturers, where production involves adding the engine, suspension and interior components to a completed body, Lotus starts with the bare chassis and adds everything possible to it. “Our assembly line is the reverse of most larger OEMs, whereby we build the body around the completed chassis. If we built the body first, it would be virtually impossible to install the cars’ internal parts,” says Jenkinson. As a chassis progresses along the production line, it is either lifted (via an overhead transfer line) or rolled on a trolley between each station. As the production schedule requires, manpower can be shifted from one station to another, a benefit of having a remarkably low turnover in personnel. “We can distribute personnel depending on the number of jobs expected at a station,” says Jenkinson. “In fact,” he continues, “we have a good combination of Lotus workers with ex-OEM employees. Each group brings different insights to the production process and we take the best from both worlds.”
Fuel for thought
While Lotus is world-renowned for its chassis and suspension engineering, a lesser-known, but equally important engineering division researches renewable fuel technology. While many companies have invested in developing hybrid and fuel cell applications, Lotus has chosen to research alcohol-based fuels, primarily ethanol and methanol. Typically, the company has taken a lead in investigating how to successfully implement these fuels. It has developed a new tri-fuel (methanol, ethanol and gasoline) system, currently being tested on an adapted Exige SC, namely the 270E Tri-fuel that appeared at the Geneva Motor Show. But beyond that, the company has also formulated what would appear to be a viable, long-term solution to the sourcing of the fuel itself.
Adapting existing engines to make the most efficient use of methanol is the first order of business. “The fuel system is the first thing that needs to be addressed with any alcohol fuel, as the fuel is so aggressive compared to gasoline,” explains James Turner, Chief Engineer of Powertrain Research. “Alcohol attacks nylon and that sort of plastic, causing the lining to swell, restricting the flow area. Also, not so much with methanol, but magnesium dissolves in ethanol, so you have to be fully knowledgeable about the characteristics of the fuels in order to specify everything that’s going to come into contact with the fuels. Actually, that sounds a lot worse than it is. Most fuel lines are tested with methanol because it is an aggressive compound; if it can handle methanol, it can handle gasoline.
“Engine-wise, in terms of alcohol combustion, there are pluses and minuses. The pluses are thermal efficiency. Where as we measure efficiency in terms of miles-per-gallon, the important thing is the energy the engine is using. Engineers measure thermal efficiency using the power measured on the dynamometer divided by the product of the fuel flow rate and multiplied by the energy content. It’s divided by the rate you push energy into the engine. So a very good thermal efficiency for a small engine would be 40 per cent, peak thermal energy – 40 per cent of the fuel energy you put in is turned into useful energy at the flywheel; 60 per cent is lost through heat, whether it’s friction, through the cooling system, or out of the exhaust. The man in the street pays for 100 per cent, but we can’t convert 100 per cent of the energy that he’s bought into useful power. “What that means is that it removes miles per gallon out of the equation of thermal energy. Miles per gallon is something you don’t want to get hung up when talking about alcohol fuels because they don’t contain the same energy as gasoline; it’s about 25 per cent less. We’re all conditioned to think in terms of miles-per-gallon because it’s easier to think in terms of volume flow than to get your mind around energy, but energy is what you pay for. You might buy fuel by the litre, but the volume the fuel occupies is of no practical use. It’s the energy it contains that gets you from A to B. So we have to move to a thought process that’s about the energy.
“The way that you can realise efficiency is more of a function of the fuel itself. If you take methanol, it’s very high octane, with a rating of up to 120 and beyond, where standard premium gasoline is 93. This allows engines to run at much higher compression ratios, with more boost, allowing you to downsize the engine and make it more efficient. Methanol and ethanol both posses characteristics that are very useful in an engine, but most of all they have a very high latent heat. In forcing it to evaporate through an injector, it removes a lot of heat from the air, which also helps to crank the boost up. Methanol and ethanol are perfect fuels for spark ignition engines.”
Lotus even has a plan for that, according to Turner. “The only practical way we have of making ethanol now is by taking some food stock, but that’s not acceptable in the long term. Instead there are new processes, sometimes called third-generation processes, that take waste (such as cardboard) to which you add enzymes and then distil it. This gives you bioethanol. But you can also make methanol from bio routes as well, from biogas; if you burn it rich with oxygen effectively it doesn’t go fully to CO2 and hydrogen, it goes to methanol and water. There are other benefits to methanol as a fuel. For example, owing to the OH portion of the methanol molecule allowing weak polar bonds, it allows the molecule to assume a molecular weight of not 32 but 128, well within the liquid range. This explains how methanol and ethanol can effectively bond with gasoline (in flex-ethanol and gasoline, and tri-fuel systems), and also how methanol is highly miscible in water. In fact, this is one of the reasons that methanol is favoured as a fuel in racing, the fact that water can put out a methanol fire.
Methanol can also be made using other methods. “Any hydrocarbon feedstock can be used to make methanol,” says Turner. “It’s the simplest of the alcohols, the first product in the Fischer-Tropsch reaction, what some companies use to make gasoline. You could put anything in the front of a Fischer-Tropsch reaction which has a hydrocarbon basis, biomass, gas, coal, even oil. But one of the best ways of making methanol is to use carbon dioxide and hydrogen, using a methanol synthesis reaction, a rich-combustion reaction. This is an exothermic reaction, which is one of the reasons its good to use carbon dioxide, so you can use some of that heat and the hydrogen can be electrolyzed using energy from renewable sources.” If we’re making hydrogen, why not use that as the fuel source?
“Hydrogen has been talked about as the energy solution of the future, but that’s not feasible. From a practicality point of view you can only store 20 per cent of the energy per unit volume with hydrogen at 700 bar or liquified that you can store with gasoline. So your tanks will have to be a lot bigger. But the killer is that hydrogen is so difficult to store, transport and distribute. To pressurise hydrogen to 700 bar means that I have to invest 15 per cent of the energy that that tank contains to pressurise the tank, and that’s an irreversible loss. But that looks pretty attractive compared to liquefaction. Hydrogen is the lightest element, so therefore it has the lowest boiling point: 20 degrees absolute. What that requires, from a plant point of view, is expander plants, propane refrigeration, all manner of storage solutions. If an efficient plant was to be built of a large enough size to service the hydrogen economy, each tank would require an investment of 30 to 40 per cent of the energy contained to liquify the product. On top of that, you need anywhere up to four times more lorries for liquifaction and twenty-two times more for pressurisation, because the tanks are so heavy. This equates to a situation where for every wind turbine built to electrolyze water, three more would have to be built to overcome the inefficiencies in the system.
“Alternatively, you could concentrate on batteries,” continues Turner. “The laws of thermodynamics say that there will always be an energy loss between states of energy and batteries have the fewest number of changes.
But the economics of batteries are against you, as they are so expensive. The energetics remove hydrogen from the equation in the short term and the economics are against batteries, in the short term at least. So what do you do? For us, the logical choice is methanol. Methanol’s a liquid, it stays where you put it, inside its container and we can distribute it using a modified version of the infrastructure we have at the moment. Furthermore, we can burn it in modified versions of what we all produce at the moment.” This is a very attractive model, especially for developing nations looking to implement alternative fuel strategies for their rapidly expanding populations. According to Turner, at 100,000 units per year, it costs approximately €10,000 per car to adapt it to use hydrogen and €25,000 for a batterypowered vehicle. These are unacceptable prices in most developing economies, where transportation is required to be safe, reliable and above all, cheap.
And where will the CO2 be sourced for methanol production? “Currently, there are fines being levied on power stations and other operations that produce CO2. Here you’ve got the basis of an economic argument. Rather then paying the fines, invest in making methanol, take it off site and burn it in cars. What you’re essentially doing is taking some people’s pain away and giving them something they can sell. Ultimately, though, the atmosphere is the place to source your CO2. The way you do that is to use potassium hydroxide to collect the gas, bring it back to the processing plant, heat it and it releases the CO2. From there you take your CO2 in a concentrated steam next door to where you have your hydrogen, combine the two in a shift reaction, using the heat caused to extract further CO2 from the potassium hydroxide. It’s an idea put forward by George Olah, a methanol specialist at the University of California, author of ‘The Methanol Economy’.”
And that’s not the end of the methanol story. The product also lends itself to making other, more complex hydrocarbon molecules. Meaning that for every dashboard made from methanol-synthesized plastic, CO2 is being permanently removed from the atmosphere.
“You cannot achieve zero per cent emissions from an internal combustion engine that’s running on fossil fuel. The laws of thermodynamics dictate that that is impossible to achieve. But if I make a renewable fuel, I can outmanoeuvre thermodynamics from the point of view of fossil CO2. “Every step in this process is doable, or has been done. What we need is to link them all together and you can use economics to drive the process.” So how long will it be before customers can buy a Lotus with a tri-fuel adaptation?
“I don’t know,” says Turner, “because we still have to push the infrastructure, but we’re not doing this from Lotus’ point of view. What we’ve done is draw this line between different elements of the problem, from one end to the other. What we need now is investigation from a proper lifecyclist, to see if all the solutions we have devised can be brought together in one workable solution.”