ORCA Velomobiles
The velomobile: high-tech bike or low-tech car?
Recumbent bikes with bodywork evoke a curious effect. They look as fast as a racing car or a jet fighter, but of course, they're not.
Nevertheless, thanks to the recumbent position, the minimal weight and the outstanding aerodynamics, pedalling a "velomobile" requires three to four times less energy than pedalling a normal bicycle.
This higher energy efficiency can be converted felt in terms of comfort, but can also be utilised to attain higher speeds and longer distances - regular cyclists can easily maintain a cruising speed of 40 km/h (25 mph) or more. The velomobile thus becomes an excellent alternative to the automobile for medium distances, especially in bad weather.
Basically, a velomobile is a recumbent bike with the addition of a bodywork. Recumbent bikes are considered a bit weird, but they have some interesting advantages over normal bicycles. For example, a recumbent bike has no saddle but a comfortable seat with back support, so that you sit or lie more comfortably and can keep pedalling for longer. Because of their superior aerodynamic capabilities, pedalling on a recumbent takes less effort, allowing you to travel more quickly and further than on a normal bicycle. Recumbent bikes can have two, three or four wheels. Trikes (3 wheels) and quads (4 wheels) offer the additional benefit of stability.
A velomobile - almost always a trike - offers two extra advantages over normal recumbent tricycles. The bodywork protects the rider (and mechanical parts) from the weather, so that the vehicle can be used in any season or climate. Furthermore, the aerodynamic shape of the bodywork further improves the efficiency of the vehicle, with spectacular results.
Velomobile versus bicycle
From the table below (source.pdf) one can observe that the power output required to achieve a speed of 30 kilometres per hour (18.6 mph) in a state-of-the-art velomobile (the Quest) is only 79 watts, compared to 271 watts on a normal bicycle and 444 watts on a neglected bicycle. Pedalling at a speed of 30 km/h thus requires 3.5 times less energy with a velomobile than with a normal bicycle. Going flat out (a power output of 250 watts) gives you a speed of 29 km/h (18 mph) on a normal bicycle and 50 km/h (31 mph) on a velomobile.
NASA rates the average long-term power output for a male adult at 75 watts, while fit individuals might easily sustain more than 100 watts for several hours, from 200 to 300 watts for one hour, and between 300 and 400 watts for at least 10 minutes. Lance Armstrong is said to have averaged between 475 and 500 watts for 38 minutes during an uphill climb in the 2001 Tour de France. (Source: The human powered home).
If you normally commute by bicycle, you can do two things with a velomobile: Retain the same speed as you normally do, but use 3.5 times less energy, or arrive at your destination twice as quickly with the same effort. This high efficiency greatly enlarges the range of a pedal powered vehicle. The bicycle is generally being viewed as a transport means for short distances, mostly below 5 kilometres or 3 miles (= cycling 15 minutes at a speed of 20km/h or 12.4 mph). However, the average distance of a car trip in Europe and in the US amounts to between 13 and 15 kilometres (8 and 9.3 miles).
A velomobile reaches a constant cruising speed of 35 km/h (21.7 mph) with the same energy output, so that the distance covered in 15 minutes becomes 9 kilometres (5.5 miles) instead of 5 kilometres (3 miles). At a speed of 45 km/h (not unusual for a regular cyclist) the distance covered in 15 minutes becomes more than 11 kilometres (6.8 miles). Thus, twenty minutes of pedalling on a velomobile sufficiently covers an average automobile trip. The velomobile could replace a substantial portion of car miles, especially because the vehicles also protect their occupants from wind, rain and cold.
By definition, velomobiles are built for speed. The bodywork offers a distinct advantage at higher speeds, starting at 20 to 25 km/h (12.4 to 15.5 mph). Above those speeds, almost all energy produced by a cyclist is channelled toward combating air resistance. Because of the upright position, the aerodynamics of a cyclist on a normal bicycle are disappointing. A velomobile, on the other hand, suffers less air resistance than even the most aerodynamic sports car.
At lower speeds, however, the relatively heavy (25 to 40 kilograms) velomobile becomes a disadvantage. It accelerates slower than a normal bicycle, and has considerably more difficulty climbing a hill. An electric assist motor can solve this problem in hilly regions. The motor can help the velomobile climb, while energy can be recovered from the brakes during the descent. Of course, an electric assist can also be considered on flat terrain, an option that is gaining a lot of popularity these days.
By definition, the velomobile is essentially built for longer distances. For shorter city trips the traditional bicycle is unbeatable. It accelerates faster, it is more manoeuvrable, and it is very easy to hop on and off.
Velomobile versus electric car
Dries Callebaut and Brecht Vandeputte, the Belgian designers of the WAW-velomobile, calculated how the efficiency of a velomobile relates to the efficiency of an electric automobile (using their own data and this source). During an eco-marathon earlier this year they equipped their velomobile with an electric motor, a complete substitution for pedal power. This is not really what the vehicle is intended for, but the advantage of the experiment is that it allows for an unequivocal comparison.
The energy consumption of the WAW was measured at 0.7 kWh per 100 kms (62 miles). This makes the velomobile in excess of 20 times more efficient than electric cars currently on the market. For example, the Nissan Leaf requires 15 kWh per 100 kms. The enormous difference is of course due to the enormous difference in weight. Without the battery, the Nissan weighs just over a ton, while the WAW weighs less than 30 kgs.
For a human powered velomobile the comparison is a bit more complicated and open to interpretation, because a human does not run (primarily) on electricity, but on biomass. The efficiency of a human powered velomobile thus depends on what the cyclist eats (the efficiency of an electric car also depends on how the electricity is generated). Callebaut and Vandeputte set the primary energy use to 0.6 kWh/100 km for a vegetarian diet from your own garden, to 2.4 kWh per 100 km for the average diet of the western non-vegetarian.
A human powered velomobile is thus 15 to 62 times more energy efficient than a Nissan Leaf. Not just 6 to 25 times, because we are comparing primary energy here. The 15 kWh that is consumed by the Nissan equates to around 37.5 kWh primary energy since electricity plants (in Europe) have an efficiency of 40 percent.
You can also argue that burning fat is a positive thing regardless of where food comes from, since obesity and a lack of exercise are endemic throughout the western world. The energy that is now being wasted in fitness centra, or the fat that is hanging in front of the television, could be put to good use as an oil substitute in transportation. In this view, the velomobile consumes (just as the cyclist and the pedestrian) 0,00 kWh per 100 kilometres.
ORCA Velomobiles:
compartiendo conocimiento.
PulzarStudios
Comentarios
Publicar un comentario