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EU approves Mercedes-Benz ECO Thermo engine cover as fuel-saving Eco-innovation

Phantom graphics of the Mercedes-Benz S 300 BlueTEC HYBRID showing ECO Thermo engine cover. Click to enlarge.

The European Commission has approved the new ECO Thermo Cover engine compartment encapsulation in the Mercedes-Benz S 300 BlueTEC HYBRID (earlier post) as a manufacturer’s Eco-innovation. Insulating buildings saves energy; Mercedes engineers have adopted a similar idea in the car.

With insulating partitions in the engine compartment and a radiator shutter that is closed when the car is at a standstill, the heat inside the Mercedes-Benz S 300 BlueTEC HYBRID remains in the engine compartment, even if the vehicle is stopped for some time. When the engine is started again, the higher temperatures reduce friction in the engine, minimize cold-start losses, and cut CO2 emissions. Tests performed at Mercedes-Benz indicate an average fuel saving of up to 1.5 liters per full 70-liter tank (i.e., around 2.1%) over the course of a year.

Thermographic image of the Mercedes-Benz S 300 BlueTEC HYBRID without (left) and with (right) ECO Thermo Cover. Click to enlarge.

Mercedes-Benz has been working together with the EU’s Joint Research Center to develop a procedure for verifying the potential savings, and it has become the first automotive manufacturer to successfully apply for allowance of ECO Innovation Credits in the field of thermal energy storage. The CO2 reduction due to the ECO Thermo Cover has now been certified by the EU.

ECO-innovations were defined in CO2 legislation in 2009, although the EU has only approved four since then.The EU approves innovative technologies that offer potential savings during actual driving, in particular those technologies which can not be taken into account in the New European Driving Cycle (NEDC).

Under the Regulation, a technology can qualify as an Eco-innovation if it is new to the market; contributes to significant CO2 savings and is not otherwise taken into account in determining the level of CO2 emissions from vehicles. The technology should also aim at improving vehicle propulsion or the energy consumption of devices that are mandatory, without compromising vehicle safety.

This means, for example, that solar panels converting sunlight into electric energy could potentially qualify as an Eco-innovation but an energy-efficient in-car music system would not.

The ECO Thermo Cover has no effect in the NEDC laboratory tests because, in these prescribed consumption tests, the vehicle always has to be cooled down to the same test station temperature.

Other examples of approved automotive Eco-innovations are:

  • Audi’s use of LEDs in the low beam headlamp, the high beam headlamp and the licence plate lamp.

  • Valeo’s Efficient Generation Alternator, with an efficiency of at least 77%, reduces CO2 emissions by at least 1g CO2/km.



Less heat wasted = less fuel consumed?

If all heat created by ICEs was recuperated, the 100 mpg ICEVs would be around?


No. They are just keeping the block warm.


Well, this reduces the fuel consumption under normal driving conditions. However, the EU (and other test cycles as e.g. the US) driving cycle has such a long soak period that this has no effect at all in the test. Thus, it is generally a nice feature if the legislation allows credits for such innovations, i.e. measures that offer “off-cycle” improvements. Better insulation would increase the credits and, possibly, also show a small effect in the driving cycle and help to get quick heating of the passenger compartment after cold starts. However, 100% storage of all waste heat energy would not give us 100 mpg. You can only keep the engine fully warm. The ultimate potential can easily be shown by driving two test cycles after each other where the second one obviously is conducted with a fully warmed-up engine. I do not have the numbers of this comparison (i.e. the ultimate potential) in my head but I could check some old measurements if some of you would be very interested in such a comparison.

Utilizing waste heat from a combustion engine in some other way, e.g. rankine cycle or thermoelectrics, are other options. The potential here is in the exhaust, since the energy from the cooling system is at too low temperature and can principally only be stored as heat for utilization as such. The efficiency will not be that good for exhaust energy recovery either, since the temperature level here is also relatively low, i.e. compared to the ~2000°C we have in the combustion chamber. However, this is still an improvement potential that e.g. fuel cell cars (with low-temperature FC stack) or electric cars do not have. Albeit from recovery of energy, the biggest potential for improving ICEs still lie in reducing the waste heat. Strange as it might sound, many features used today, such as e.g. turbocharging, downsizing and direct injection, actually decrease waste heat. Thermal insulation of the engine components that actually would not improve efficiency of the engine could shift waste heat from coolant to exhaust and thereby, increasing the potential for energy recovery. Not much has been done in this field for the last 2-3 decades.


I saw a patent (GB2502117 - A thermal management device for the oil sump of a vehicle utilising the coolant system) of Ford Global Technologies which proposes a more advanced solution. This can be applied at conventional or hybrid vehicles and describes a thermal management device of an oil sump. The heat is accumulated from a previous driving cycle so that the coolant and the oil have a higher temperature than the environment during the cold start, permitting a quick warm-up of the engine. Comparing with Mercedes solution, Ford concept is cheaper and can be applied to low and medium cost vehicles, having superior benefits.

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