Annoy As Little Air As Possible

To say that the Very Light Car displays great aerodynamic efficiency is an understatement. This summer we spent a shift in the GM wind tunnel in Warren, Michigan, and we just flat-out nailed it. We recorded a 0.16 coefficient of drag: the best results ever seen in their wind tunnel, we were told.

No wonder. Our Chief of Aerodynamics is Barnaby Wainfan, the aerodynamics fellow at Northrup Grumman. The goal of aerodynamic efficiency is to punch as small a hole in the air as possible and try to close it seamlessly behind you, or as Barnaby says “annoy as little air as possible.”

Air separates as it flows around a car and inevitably creates a “dead zone” of low pressure behind, an inefficiency known as “base drag”. A way to help close the air is with a tail: either a horizontal “beaver tail”, seen on our X Prize competitor Aptera, or with the vertical “fish tail” we employ.

A big part of not annoying air is keeping it from entering the car except as necessary, such as for cooling. Contemporary cars often have oversize grills and usually exposed wheel wells: both allow air to enter and bang around inside the car. The car grabs this air and accelerates it to the speed the car is traveling and the energy for this comes from the engine.

With the Very Light Car we enclose the wheels outside the body in pods. This design allows a smaller frontal area, with each wheel pod also poking its own small hole in the air. We are deliberate about exactly where and how much air enters the car.  We then put the air back outside where it will do the most good, reintroducing it into the “dead zone”. We also avoid exposing anything to the air that we do not have to, using cameras instead of mirrors and flush-mounting the door latches. 

Drag coefficient (Cd) might be the headline number but to know actual drag you need to factor in this frontal area. When Cd and frontal area are multiplied together, the product, CdA, allows you to directly compare different cars. It turns out a Hummer H2 (which not only is huge but also has a terrible aerodynamic shape) has about 9 times the drag of the Very Light Car. Even a 2010 Prius, a car with a very good Cd (.25), has almost twice our drag.

At Edison2 we take great care and pride in making only definite and supportable claims about our car. Our drag numbers were obtained by the dedicated and competent engineers running one of the world’s top wind tunnels. We have since backed those numbers up with the best-ever coast down results measured by an equally impressive and credentialed facility.

The overall goal in aerodynamic efficiency is a car that moves through the air with minimal effort.  The ultimate would be if the only drag was the friction of air against the car’s body.  That perfection may be unattainable, but the Very Light Car comes close.



An Electric Very Light Car?

Edison2’s Very Light Car Scoffs at Electric Avenue said AutoBlog Green in January, highlighting the irony of our internal combustion engine powered car sitting in the midst of all the electrics at the Detroit Auto Show.

But electric vehicles are here to stay and an electric VLC makes sense. Our breakthroughs in platform efficiency make all vehicles way more efficient, regardless of power source, and in an electric help solve issues of cost and range.

Billions are being invested in electric vehicle technology for a number of reasons. EV’s provide a path to energy independence and with American jobs, whether in the creation of green energy sources or in the mining and processing of coal. As a new industry, electric cars have the potential to revitalize important sectors of our economy. Electric vehicles are particularly efficient in short-cycle applications, such as Postal Service vans or some predictable commuters, and the relocation of emissions to a distance can be an advantage. Night-time charging will utilize excess generating capacity, and as the electric grid becomes green so can the future of transportation.

Currently, however, electrics cars have real issues. Batteries are heavy, big and costly. With electric drives cars get heavier, performance suffers and costs go up.  Range is especially an issue, as witnessed by the numerous EVs in the 100-mile range X Prize alternative classes that made it to the knockout stage, versus only one EV in the 200-mile range mainstream class.

The hope and plan for electric cars is that the tremendous investment in battery technology will cause the weight and expense of batteries to go down, increasing range and decreasing costs of electric cars.  But another way to increase the range of electric vehicles is with VLC innovations: a car that simply takes less energy to move can go farther and faster with a smaller, lighter and less expensive battery pack.

Coming soon, perhaps: an electric Very Light Car.



X Prize Finals: Week 1

The first week of the X Prize finals is complete and the results are in.

 

Of the 12 teams that came to the finals 4 have been eliminated or have withdrawn (Amp, Tango, Tata and Spira). Very Light Cars now comprise almost a third of the entire field. It is now us against the X Tracers in the Alternative Tandem class, and us against ourselves in the Mainstream class.

Our cars did well in very challenging circumstances. Our #95 tandem car got a combined 110.8 MPGe (including almost 130 in the highway cycle), but the mainstream cars ran later each day, in windy and very hot conditions. The #98 achieved 101.3 MPGe and the #97, 95.6 MPGe.

The #97 car had to deal with a traffic situation during the test that resulted in using turbo boost to stay within lap time requirements: frustrating, given that this car already made 101.4 MPGe in the Knockout stage, and is about 5 MPGe better now because of emissions mapping improvements. This car did meet the X Prize requirement of 90 MPGe; these efficiency results will be averaged with results to come in August at the Argonne National Lab on the dynamometer (ie, no wind or heat).

We also expect to pick up another 1 – 3 MPGe because we now know there is evaporation of E85 from the X Prize supplied fuel tank. This problem was discovered by PIAXP staff, for which we are grateful. We willingly installed this tank for transparency but have had trouble due to its required location in the engine compartment. 

Monday the 26^th are the dynamic safety events (lane change, acceleration and braking) and on Tuesday the combined performance and efficiency event. This combined event is the actual race. It requires cars to exceed 100 MPGe within a maximum and minimum speed range on a course with turns. The car in each class that completes this course in the shortest time is eligible to be an X Prize winner.

The end of the week will be coast-down testing, to collect data necessary for the dyno tests at Argonne. Then the cars will be taken by the X Prize to the Argonne Labs in Chicago for emissions and efficiency testing in August.

Winners will be announced in September.

Greetings from the X Prize Finals

The Finals stage of the Automotive X Prize is underway. Twelve teams from six countries unloaded their trailers and moved into garages Sunday and began technical inspections yesterday morning. Of the 136 cars that entered the 3 categories of the X Prize a year ago only 15 remain.

The Alternative Side-By-Side class (100+ MPGe, 100 mile range, 2 passengers seated side-by-side, 0-60 in 18 seconds) finalists are Amp, (Cincinnati, OH), Aptera, (San Diego, CA), Li-ion Motors (Mooresville, North Carolina), RaceAbout Association, (Finland), Tata Motors (Coventry, UK) TW4XP (Germany), Western Washington University (Bellingham, WA) and ZAP (Santa Rosa, CA). WWU uses a hybrid drive, and the other Side-By-Sides are battery electrics.

The Tandem class – same requirements as Side-By-Side except for seating position – consists of Tango (Spokane, WA), Spira (Carrollton, IL/Thailand), X-Tracer (Switzerland), and our # 95 Very Light Car. X-Tracer has two entries, very similar 2-wheelers. The Tango and the X-Tracers are electric, while our Very Light Car and the Spira are internal combustion.

We have the Mainstream class to ourselves. Our E85 fueled #97 and #98 cars were the only entrants to survive the Knockout round.  Mainstream requires a 200-mile range and a 15-second 0 – 60: stiff requirements, especially for electrics and hybrids, helping explain our lack of finals competition. The Mainstream class comes with a $5 million prize, the Alternative classes $2.5 million each.

Not to say we have the Mainstream class wrapped up: far from it. Wednesday through Friday begins a series of efficiency events, mimicking the EPA mileage cycles and requiring a combined 100 MPGe. Dynamic safety events, such as lane-change and braking, are on Monday, with the combined performance and efficiency event on Tuesday.

This combined event is the actual race. It requires cars to exceed 100 MPGe on a course with a variety of turns, within a maximum and minimum speed range. The car that completes this course in the shortest time will be an X Prize winner (and it is possible all requirements will not be met and a category will not have a winner). The top cars in each category will spend the end of next week undergoing coast-down testing, a requirement for dynamometer testing of emissions and mileage at Argonne National Laboratory in August. Argonne also puts the cars through another stiff challenge, especially for electrics: a 40-minute hill climb on the dynamometer. The dyno efficiency results are averaged with the MIS track results, and if the combination is greater than 100 MPGe, if the emissions are met, and if the Argonne hill is successfully climbed, a champion will be announced.

 

Yesterday all three of our cars passed technical inspection. Not all cars at the finals have done so yet and some may face an early elimination. Today we are readying all three cars for the efficiency tests; Wednesday morning the urban cycle testing begins at 8:30 for the #95 car.

The finals are a complicated, lengthy series of events. It can be followed, much of it  real-time, at the Progressive Automotive X Prize website. Stay tuned.



Thoughts on MPGe

Our #97 mainstream 4-seat Very Light Car achieved 101.4 MPGe in the combined EPA cycle at the X Prize Knockout.

An interesting side note to this accomplishment is that the engine we are using is a 250 cc, one-cylinder internal combustion engine from a Yamaha WR 250R.  This small motorcycle weighs 300 lbs and gets 70 MPG, and does not have to meet tough emissions standards.

Our Very Light Car weighs over 700 lbs and gets over 100 MPGe. – while exceeding the stringent 2014 emissions standards, including cold start. How does this leap in mileage occur? Mainly two ways: the extreme platform efficiency of the Very Light Car, and improvements made to the engine. The Very Light Car adds a turbocharger, increases compression, uses extensive exhaust gas recirculation and reengineered internal parts and runs on E85. A similarly efficient gasoline engine we considered doable but would have taken longer, especially the emissions system.

The Very Light Car is not the only entry remaining in the X Prize that can be compared to an existing car’s mileage. Tata’s Indica Vista EV X (a production 4-passenger car, entered in the Alternative 2-passenger Side-by-Side class, presumably to avoid the mainstream 200-mile range requirement) gets 33 – 40 MPGe as a production car, but in the X Prize achieved much more: a combined 134.3 MPGe while running as an electric vehicle.

What explains the much greater efficiency of the X Prize Tata?  No doubt it partly reflects the efficiency of the electric motor, properly applied. But this achievement is also a function of the underlying method of measuring energy use in an electric vehicle.

Energy use in an internal combustion engine is straightforward: measure an amount of gas, drive, and measure again. For the X Prize the cars have standardized gas tanks that are removed and weighed.

Electricity use is similarly measured at the X Prize. Batteries are refilled at charging stations and metered for energy consumption: a “plug-to-wheels” formula, that accounts for losses in the charger, in the battery, and energy used by the engine to move the car. Certainly a more accurate representation than measuring the energy use motor-to-wheels, which leads to results all over the map, including some very high mileage numbers.

A problem is that electricity is only an energy carrier and thermal conversion of energy is not considered in this calculation.  In the real world for every BTU put into the American power grid for the production of electricity only 52% makes it to the plug.  This 48% loss (from energy conversion and distribution) is not accounted for in the plug-to-wheel calculation.

 This plug-to-wheel calculation is important as there are many good reasons to shift toward an electric transportation future, such as new options, existing capacity, energy independence and remote emissions. However, a more accurate number for the Tata efficiency would be 40 mpg on gasoline and (134MPGe x .52) 70 mpg as an electric.

This is a more efficient vehicle as an electric but the efficiency comes with costs: battery expense, range restriction and issues like grid capacity and resource allocation. Certainly a path worth pursuing, especially as the electric grid moves away from coal towards renewable sources of energy.

Very complicated issues – what about the efficiency of distributing gasoline or ethanol? - and the X Prize is to be commended for adopting a clear, understandable standard in MPGe.   

But the fact remains: our Very Light Car – the most efficient automotive platform ever built – has crossed the 100 MPGe threshold.