Ask Joe Mechanic - Solar Powered Vehicles (Part 1)

Ask Joe Mechanic…Solar Powered Vehicles

Solar power is another source of power, which would release us from foreign dependence for energy, but it is not yet practical. The cells are expensive and it requires a large number of them to generate the power required to power a vehicle. At this time, the most practical use is to generate power to use in plug-in electric or hybrid vehicles, as opposed to using it to directly power the vehicle.

A solar vehicle is an electric vehicle powered completely or significantly by direct solar energy. Usually, photovoltaic (PV) cells contained in solar panels convert the sun's energy directly into electric energy. The term "solar vehicle" usually implies that solar energy is used to power all or part of a vehicle's propulsion. Solar power may be also used to provide power for communications or controls or other auxiliary functions.

Solar vehicles are not sold as practical day-to-day transportation devices at present, but are primarily demonstration vehicles and engineering exercises, often sponsored by government agencies. However, indirectly solar-charged vehicles are widespread and solar boats are available commercially.

Solar cars depend on PV cells to convert sunlight into electricity to drive electric motors. Unlike solar thermal energy, which converts solar energy to heat, PV cells directly convert sunlight into electricity.

Solar cars combine technology typically used in the aerospace, bicycle, alternative energy and automotive industries. The design of a solar car is severely limited by the amount of energy input into the car. Solar cars are built for solar car races or daily usage on public roads. Even the best solar cells can only collect limited power and energy over the area of a car's surface. This limits solar cars to ultra light composite bodies to save weight. Solar cars lack the safety and convenience features of conventional vehicles.

Solar cars are often fitted with gauges and/or wireless telemetry, to carefully monitor the car's energy consumption, solar energy capture and other parameters. Wireless telemetry is typically preferred as it frees the driver to concentrate on driving, which can be dangerous in such a small, lightweight car.  The Solar Electric Vehicle system was designed and engineered as an easy to install (2 to 3 hours) integrated accessory system with a custom molded low profile solar module, supplemental battery pack and a proven charge controlling system.  As an alternative, a battery-powered electric vehicle may use a solar array to recharge; the array may be connected to the general electrical distribution grid.

Solar buses are propulsed by solar energy, all or part of which is collected from stationary solar panel installations. The Tindo bus is a 100 percent solar bus that operates as free public transport service in Adelaide City as an initiative of the City Council. Bus services, which use electric buses that are partially powered by solar panels installed on the bus roof, intended to reduce energy consumption and to prolong the life cycle of the rechargeable battery of the electric bus, have been put in place in China.

Solar buses are to be distinguished from conventional buses in which electric functions of the bus such as lighting, heating or air-conditioning, but not the propulsion itself, are fed by solar energy. Such systems are more widespread as they allow bus companies to meet specific regulations, for example the anti-idling laws that are in force in several of the US states, and can be retrofitted to existing vehicle batteries without changing the conventional engine.

The first solar "cars" were actually tricycles or Quadracycles 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 used solar power exclusively while the other half used 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. With today's high performance solar cells, a front and rear PV panel on this solar bike can give sufficient assistance, where the range is not limited by batteries.

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.  In May 2007, a partnership of Canadian companies led 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 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, and solar charged electric scooter. It has a top speed controlled at a bit over 30 mph, and uses foldout solar panels to charge the batteries while parked.

Photovoltaic modules are used commercially as auxiliary power units on passenger cars in order to ventilate the car, reducing the temperature of the passenger compartment while it is parked in the sun. Vehicles such as the 2010 Prius, Aptera 2, Audi A8, and Mazda 929 have had solar sunroof options for ventilation purposes.

The area of photovoltaic modules required to power a car with conventional design is too large to be carried on board. A prototype car and trailer has been built Solar Taxi. According to the website, it is capable of 100 km/day using 6m² of standard crystalline silicon cells. Electricity is stored using a nickel/salt battery. A stationary system such as a rooftop solar panel, however, can be used to charge conventional electric vehicles.