Lotus Engineering, a division of Lotus, one of the world’s renowned automotive consultants unveiled its Range Extender Engine at the 63rd Frankfurt International Motor Show.  Used in series hybrid vehicles, Range Extender Engines are coupled to an electrical generator to provide a highly efficient source of energy to power the electric motor directly or charge the vehicle’s capacitors and batteries.  Mated to storage devices enables the design of a drive train that has low emissions, optimized performance and much more of an extended range.

The Range Extender Engine is a three-cylinder 1.2-liter, optimized between two power generation points, giving 15 kW of electrical power at 1,500 rpm and 35 kW at 3,500 rpm.  Designed for low mass with an integrated electrical generator it comes in at only 56 kilograms or about 123.5 pounds. Astonishing.

Lotus Range Extender Engine Generator Set. Click image for more information.

Lotus Range Extender Engine Generator Set. Click image for more information.

A successful market for series hybrid vehicles depends on acceptable driving range, so vehicle manufacturers must overcome the challenges of high vehicle cost including batteries, capacitors and charging sets.. The Lotus Range Extender Engine not only offers the advantage of a cost effective design, but also its high efficiency and low mass will also enable the downsizing of expensive batteries while maintaining vehicle efficiency and range. The engine has been designed using production methodologies and the parts procured from low volume potential production suppliers, offering a fast route to market for original equipment manufacturers wanting to source a dedicated range extender for series hybrid vehicles.

The new engine features an innovative architecture based on an aluminum monoblock that integrates the cylinder block, cylinder head and exhaust manifold in one casting. This result in reduced engine mass, assembly costs, package size and improved emissions and engine durability.

Paul Newsome, Managing Director of Lotus Engineering said, “The engine concept we have created with its optimized combustion and compact, low mass, low cost construction is a clear demonstration of the expertise and progressive approach Lotus takes for its own research and for its clients.”  The engine is being developed as part of the ‘Limo-Green’ project funded by the UK’s Technology Strategy Board, a collaboration between Lotus Engineering, Jaguar Cars Ltd, MIRA Ltd and Caparo Vehicle Technologies, for demonstrating a large, lightweight, prestigious executive saloon with less than 120 g/km CO2 emissions.

Lotus Engineering’s technical director Simon Wood points out, “Most series hybrid vehicles that are currently being developed will use adaptations of existing, conventional engines which are therefore compromised in the efficiency that they can achieve, designed as they are for a wide range of operating conditions. Designing the Lotus Range Extender purely for use in series hybrids has allowed us instead to develop an optimized engine that has high thermal efficiency, low fuel consumption, multi-fuel capability and a 35 kW peak output from a 1.2 liter, low cost architecture over the precise operating range required by a series hybrid drive train.”  Manufacturers take note, this path is the surest way to low cost builds and customer operating expenses.

The general engine specifications seem mundane if small.  But don’t make an assumption that exotic requires exotic specifications.  Lotus is coming to market with 1.2 liters in a 3 cylinder under a conventional 2 valve head topped by a single overhead cam driven by a belt.  Where the innovation takes place is in the casting where a single block is milled to form the crankshaft block, cylinder head and the exhaust manifold.  At a low 10:1 compression ratio Lotus has managed 47 bhp or better than 39 hp per liter with 107 Nm of torque.  The unit runs on gasoline, ethanol, methanol and combinations.

Taking the opportunity to just skip idle and high rpm power output is being shown by Lotus that serious continuous power can be obtained in just two running speeds.  What is missing is the overall thermal efficiency number; one specification that entrances engineers the world over.

Keep in mind that a steady state of 47 bhp is a considerable amount of raw power.  Saved back in capacitors and batteries for high power demands could offer up to several multiples of the 47 bhp for bursts whose burst time length is more a case of the capacitor storage than the power source’s gross output.  It also offers a design choice of less costly batteries, lower weights and other important choices.  For many, this writer included, range from batteries isn’t so critical as the total cost for 100 to 200 miles trips.

The opposing views will see that Lotus is a small volume manufacturer that openly states that the suppliers are as well.  That leaves the cost issue very much in mind.  But the technological developments are very likely available for moderate fees to any manufacturer looking to leapfrog ahead in the technology.

Lotus’ offering raises questions such as the thermal efficiency.  But most importantly the questions of efficiency are now becoming possible to answer.  Various combinations of generator sets, the capacitors selected for peak power and the range of choices for batteries are soon to be measurable and analyzable for overall cost to buy and operate with the choice made for motors to put the power to the wheels.

I congratulate Lotus Engineering for getting such a well thought out item to the market.  The purchase of vehicles will soon get very interesting.  We may find that 300 hp at the wheels for up to so many seconds might still have a capability of very high overall fuel mileage.  Smart choices in wind drag and overall weight added to this level of power technology well greatly extend and reduce the need for fuels and charging energy.

If the midsize sports sedan as Americans view the Brit’s “large, lightweight, prestigious executive saloon” can get to say 75 mpg and that gallon is 85% sourced from renewables such as methanol and ethanol the demand for gasoline will enter a long slow decline as well as reduce the world’s demand for crude oil.

Lets just hope that Lotus comes out with a thermal efficiency number that can be closely comparable to the numbers competitors will need to show as well.  The series hybrid market looks to get very exciting soon.


8 Comments so far

  1. antony artega on November 17, 2009 11:39 AM

    Lotus Range Extender Engine how much to buy one asap to drop in my Lotus asap….FaceBook Antony Artega

  2. Jean-Luc Fauvel on March 29, 2010 2:38 PM

    (‘This is’ – edit) The obliged transitional solution for the final step to full electric vehicle when the weight and cost of batteries will be solved (in how many years from now?).

    I am a student at the DESS, Design in transport vehicle at the UQÀM University in Montréal, Qc., Canada

  3. Tony Lease on October 6, 2010 6:41 AM

    Really in depth and informative coverage on the subject, a delight to read.

  4. Yulanda Teuscher on May 19, 2011 2:37 AM

    This post makes a lot of sense !

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