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A solar vehicle is an electric vehicle powered by a type of renewable energy, by soloa energy obtained from solar panels on the surface (generally, the roof) of the vehicle. Photovoltaic (PV) cells convert the Sun's energy directly into electrical energy. Solar vehicles are not practical day-to-day transportation devices at present, but are primarily demonstration vehicles and engineering exercises, often sponsored by government agencies.

Solar cars

Solar cars combine technology typically used in the aerospace, bicycle, alternative energy and automotive industries. The design of a solar vehicle is severely limited by the energy input into the car (batteries and power from the sun). Virtually all solar cars ever built have been for the purpose of solar car races (with notable exceptions).

Like many race cars, the driver's cockpit usually only contains room for one person, although a few cars do contain room for a second passenger. They contain some of the features available to drivers of traditional vehicles such as brakes, accelerator, turn signals, rear view mirrors (or camera), ventilation, and sometimes cruise control. A radio for communication with their support crews is almost always included.

Solar cars are often fitted with gauges as seen in conventional cars. Aside from keeping the car on the road, the driver's main priority is to keep an eye on these gauges to spot possible problems. Cars without gauges available for the driver will almost always feature wireless telemetry. Wireless telemetry allows the driver's team to monitor the car's energy consumption, solar energy capture and other parameters and free the driver to concentrate on just driving.

Electrical and mechanical systems

The electrical system is the most important part of the car's systems as it controls all of the power that comes into and leaves the system. The battery pack plays the same role in a solar car that a petrol tank plays in a normal car in storing power for future use. Solar cars use a range of batteries including lead-acid batteries, nickel-metal hydride batteries (NiMH), Nickel-Cadmium batteries (NiCd), Lithium ion batteries and Lithium polymer batteries.

Many solar race cars have complex data acquisition systems that monitor the whole electrical system while even the most basic cars have systems that provide information on battery voltage and current to the driver.

The mechanical systems of a solar car are designed to keep friction and weight to a minimum while maintaining strength. Designers normally use titanium and composites to ensure a good strength-to-weight ratio.

Solar cars usually have three wheels, but some have four. Three wheelers usually have two front wheels and one rear wheel: the front wheels steer and the rear wheel follows. Four wheel vehicles are set up like normal cars or similarly to three wheeled vehicles with the two rear wheels close together.

Solar array

The solar array consists of hundreds of photovoltaic solar cells converting sunlight into electricity. The larger arrays in use can produce over 2 kilowatts (2.6 hp).

The solar array can be mounted in several ways:

horizontal. This most common arrangement gives most overall power during most of the day in low latitudes or higher latitude summers and offers little interaction with the wind. Horizontal arrays can be integrated or be in the form of a free canopy.
vertical. This arrangement is sometimes found in free standing or integrated sails to harness wind energy.^[1] Useful solar power is limited to mornings, evenings, or winters and when the vehicle is pointing in the right direction.
adjustable. Free solar arrays can often be tilted around the axis of travel in order to increase power when the sun is low and well to the side. An alternative is to tilt the whole vehicle when parked. Two-axis adjustment is only found on marine vehicles, where the aerodynamic resistance is of less importance than with road vehicles.
integrated. Some vehicles cover every available surface with solar cells. Some of the cells will be at an optimal angle whereas others will be shaded.
trailer. Solar trailers are especially useful for retrofitting existing vehicles with little stability, e.g. bicycles. Some trailers also include the batteries and others also the drive motor.
remote. By mounting the solar array at a stationary location instead of the vehicle, power can be maximised and resistance minimized. The virtual grid-connection however involves more electrical losses than with true solar vehicles and the battery must be larger.

The choice of solar array geometry involves an optimization between power output, aerodynamic resistance and vehicle mass, as well as practical considerations. For example, a free horizontal canopy gives 2-3 times the surface area of a vehicle with integrated cells but offers better cooling of the cells and shading of the riders. There are also thin flexible solar arrays in development.

Races

The two most notable solar car races are the World Solar Challenge and the North American Solar Challenge, overland road rally-style competitions contested by a variety of university and corporate teams.

The World Solar Challenge features a field of competitors from around the world who race to cross the Australian continent, over a distance of 3000 km. The increasingly high speeds of the 2005 race participants has led to the rules being changed for future solar cars starting in the 2007 race.

The North American Solar Challenge, previously known as the 'American Solar Challenge' and 'Sunrayce USA', features mostly collegiate teams racing in timed intervals in the United States and Canada. This race also changed rules for the most recent race due to teams reaching the regulated speed limits. The most recent North American Solar Challenge ran from July 13-22, 2008, from Dallas, Texas to Calgary, Alberta. The next race is expected to run in the summer of 2010. ^[2]

There are other distance races, such as Suzuki, Phaethon, and the World Solar Rally. Suzuki is a yearly track race in Japan and Phaethon was part of the Cultural Olympiad in Greece right before the 2004 Olympics.

Solar bicycles and motorcycles

A solar bicycle or tricycle has the advantage of very low weight and can use the riders foot power to supplement the power generated by the solar panel roof. In this way, a comparatively simple and inexpensive vehicle can be driven without the use of any fossil fuels. ^[3]

Solar photovoltaics assisted electric powered India's first Quadricycle developed since 1996, in Gujarat state's SURAT city.^[4]

The first solar "cars" were actually tricycles or quadricycles built with bicycle technology. These were called solarmobiles at the first solar race, the Tour de Sol in Switzerland in 1985 with 72 participants, half using exclusively solar power and half solar-human-powered hybrids. A few true solar bicycles were built, either with a large solar roof, a small rear panel, or a trailer with a solar panel. Later more practical solar bicycles were built with foldable panels to be set up only during parking. Even later the panels were left at home, feeding into the electric mains, and the bicycles charged from the mains. Today highly developed electric bicycles are available and these use so little power that it costs little to buy the equivalent amount of solar electricity. The "solar" has evolved from actual hardware to an indirect accounting system. The same system also works for electric motorcycles, which were also first developed for the Tour de Sol. This is rapidly becoming an era of solar production.

Solar ships

Japan's biggest shipping line Nippon Yusen KK and Nippon Oil Corporation said solar panels capable of generating 40 kilowatts of electricity would be placed on top of a 60,000 tonne car carrier ship to be used by Toyota Motor Corporation ^[5].

Practical applications

The Venturi Astrolab in 2006 was hailed as the world's first commercial electro-solar hybrid car, and it was originally due to be released in January 2008.^[6]

In May 2007 a partnership of Canadian companies lead by Hymotion altered a Toyota Prius to use solar cells to generate up to 240 watts of electrical power in full sunshine. This is reported as permitting up to 15 km extra range on a sunny summer day^[7] while using only the electric motors.

One practical application for solar powered vehicles is possibly golf carts, some of which are used relatively little but spend most of their time parked in the sun.

An inventor from Michigan, USA has built a street legal, licensed, insured, solar charged electric scooter. It has a top speed controlled at a bit over 30 mph, and uses fold-out solar panels to charge the batteries while parked.^[8]

A Swiss project, called "Solartaxi," has circumnavigated the world. The first time in history a solar powered vehicle is going around the world, covering 50000 km in 18 months and crossing 40 countries. It is a road-worthy solar car with a trailer, carrying a 6 m² sized solar array. The Solartaxi has Zebra batteries, which permit a range of 400 km without recharging. The car can also run for 200 km without the trailer. Its maximum speed is 90 km/h. The car weighs 500 kg and the trailer weighs 200 kg. According to team leader Louis Palmer, the car in mass production could be produced for 16000 Euro. Solartaxi has toured the World from July 2007 till December 2008 to show that solutions to stop global warming are available and to encourage people in pursuing alternatives to fossil fuel.^[9]

Solar Electrical Vehicles ^[10] is adding convex solar cells to the roof of hybrid electric vehicles ^[11].

Limitations and challenges

Battery electric vehicles fitted with solar cells would extend their range and allow recharging while parked anywhere in the sun. However, with present and near-term engineering considerations, it seems that the more likely place for solar cells will generally be on the roofs of buildings, where they are always exposed to the sky and weight is largely irrelevant, rather than on vehicle roofs, where size is limited. Energy from rooftop panels can be stored in batteries for future use.

Plug-in hybrid and solar vehicles

An interesting variant of the electric vehicle is the triple hybrid vehicle—the PHEV that has solar panels as well to assist.

The 2009 Toyota Prius will have an option to mount solar panels on the roof. They will provide an additional 300 watts of charge while parked, and also act as a sun shade.

References

^ The Leading Edge, Tamai, Goro, Robert Bentley, Inc., 1999, p. 137
^ Official NASC Website
^ www.solartricycle.com
^ Innovative Transport Vehicle Development
^ http://www.enn.com/energy/article/38019
^ The first commercial solar-electric hybrid car
^ Hymotion modified Prius using solar power
^ PVScooter
^ Solar taxi
^ http://www.solarelectricalvehicles.com/
^ http://www.treehugger.com/files/2007/05/solar_hybrid_ca.php

External links

News

Uncle Sam Rolls In a 100-MPG Solar Plug-In Hybrid.

[Wind-1] The Leading Edge, Tamai, Goro, Robert Bentley, Inc., 1999, p. 137

[2] Official NASC Website

[3] www.solartricycle.com

[4] Innovative Transport Vehicle Development

[5] ttp://www.enn.com/energy/article/38019

[6] The first commercial solar-electric hybrid car

[7] Hymotion modified Prius using solar power

[scooter-8] PVScooter

[9] Solar taxi

[10] ttp://www.solarelectricalvehicles.com/

[11] ttp://www.treehugger.com/files/2007/05/solar_hybrid_ca.php

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 {{refimprove|date=December 2008}}
-A '''solar vehicle''' is an [[electric vehicle]] powered by a type of [[renewable energy]], by [[solar power|solar energy]] obtained from [[solar panel]]s on the surface (generally, the roof) of the vehicle.  [[Photovoltaic]] (PV) cells convert the Sun's energy directly into [[electrical energy]]. Solar vehicles are not practical day-to-day transportation devices at present, but are primarily demonstration vehicles and engineering exercises, often sponsored by government agencies.
+A '''solar vehicle''' is an [[electric vehicle]] powered by a type of [[renewable energy]], by [[solar power|soloa energy]] obtained from [[solar panel]]s on the surface (generally, the roof) of the vehicle.  [[Photovoltaic]] (PV) cells convert the Sun's energy directly into [[electrical energy]]. Solar vehicles are not practical day-to-day transportation devices at present, but are primarily demonstration vehicles and engineering exercises, often sponsored by government agencies.
 ==Solar cars==