More info on Renault's Optifuel Lab: Using cameras instead of external mirrors, a 30cm "nose", a bulge in the trailer's roof, "Kammed" wheel skirts on the trailer, and 70cm-long Kamm trailing edges, reduced fuel consumption by 13%, compared to normal trucks.
Unfortunately, the production version of of this Renault is much less futuristic: no wheel skirts on the trailer, large mirrors instead of cameras, no trailer roof bulge, no "nose".
But others have improved the aerodynamics of trucks and trailers, and even taken it further, Don-Bur's Teardrop trailer for DHL, for example. The British version's roof is 4.2-4.6 meters above the road surface, and is 9-12% more efficient than a normal trailer. DHL calculated that the extra cost of this trailer pays for itself within one year.
The continental version must respect the 4m height restriction, so the trailer had to be reworked: smaller wheels (215/75 R17.5) help lower the payload area to allow normal cargo height (internal height is between 2883mm and 2279mm), but pneumatic suspention raises the floor when docking.
MAN also showed a teardrop trailer on its Concept (see link in
Vekke's post), it reduces Cd by 34% and fuel consumption by 10%.
The next step in research will be belly pans.
The articles also give some random info on the costs and gains of certain modifications. For example,
- Optimalization of transmission gearing costs 1500EUR and saves 6% (urban), 4% (extra urban), 1% (highway).
- Supersingle tires save 6%/4%/3% and cost 200EUR extra, but have a shorter life than regular tires.
- Reducing weight by 1000kg (without adding extra cargo) saves 0.7 (highway) to 2.0 (urban) liters per 100km and costs 5000-40000EUR depending on matrials used.
- Teardrop trailer costs 3000EUR more, but saves 7-12%.