Solar car

A Solar car is an automobile powered by solar energy obtained from solar panels on the car. Solar cars are not currently a practical form of transportation as they can only operate during the day and can only carry one or two passengers. However, they are raced in competitions such as the World Solar Challenge and the American Solar Challenge. These events are often sponsored by Government agencies such as the United States Department of Energy keen to promote the development of alternative energy technology such as solar cells. Such challenges are often entered by universities to develop their students engineering and technological skills as well as motor vehicle manufacurers such as GM and Honda.

1 Solar vehicles
2 Solar car races
3 See also
4 External links

Solar vehicles

Drivers cockpit

Drivers cockpits are normally single-seat with a few cars containing room for a second passenger. They are hot from the solar panel and very cramped with few of the comforts of a normal automobile. They contain some of the features available to drivers of traditional vehicles such as brakes, accelerator, signals, rear view mirrors, ventilation and often cruise control. They also have a two way radio for communication with their support crews.

Solar cars are fitted with gauges seen in conventional motor cars and the drivers main priority is to keep an eye on these gauges to spot possible problems. Drivers also have a safety harness and optionally a helmet similar to racing car drivers.

Electrical system

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. Lead-acid batteries are less expensive and easier to work with but have less power to weight ratio. Typically, solar cars use voltages between 84 and 108 volts.

Power electronics monitor and regulate the car's electricity. Components of the power electronics include the peak power trackers, the motor controller and the data acquisition system.

The peak power trackers manage the power coming from the solar array to maximise the power and either deliver it to be stored in the battery or used in the motor. They also protect the batteries from overcharging. The motor controller manages the electricity flowing to the motor according to signals flowing from the accelerator.

Many solar 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. One such system utilizes Controller Area Network (CAN).

Drive train

The setup of the motor and transmission is unique in solar cars. The electric motor normally drives only one wheel at the back of the car due to the low amount of power it generates. Solar car motors are normally rated at between 2 and 5 horsepower (2 and 4 kW) and the most common type of motor is a dual-winding DC brushless. The dual-winding motor is sometimes also used as a transmission because multi-geared transmissions are rarely used.

There are three basic types of transmissions used in solar cars:

a single reduction direct drive

a variable ratio drive belt

a hub motor

There are several varieties of each type. The most common is the direct drive transmission.

Mechanical systems

The mechanical sytems 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 cars have a wide range of suspensions because of varying bodies and chassis. The most common front suspension is the double-A-arm suspension found in traditional cars. The rear suspension is often a trailer-arm suspension found in motor cycles.

Solar cars are required to meet rigorous standards for brakes. Disc brakes are the most commonly used due to their good braking ability and ability to adjust. Mechanical and hydraulic brakes are both widely used with the brakes designed to move freely by minimise brake drag.

Steering systems for solar cars also vary. The major design factors for steering systems are efficiency, reliability and precision alignment to minimise tire wear and power loss. The popularity of solar car racing has led to some tire manufacturers designing tires for solar vehicles. This has increased overall safety and performance.

Solar array

The solar array consists of hundreds of photovoltaic solar cells converting sunlight into electricity. Cars can use a variety of solar cell technologies; most often polycrystalline silicon, monocrystalline silicon, or gallium arsenide. The cells are wired together into strings while strings are often wired together to form a panel. Panels normally have voltages close to the nominal battery voltage. The main aim is to get as many cells in as small a space as possible. Designers encapsulate the cells to protect them from the weather and breakage.

The power produced by the solar array depends on the weather conditions, the position of the sun and the capacity of the array. At noon on a bright day, a good array can produce well over 1 kilowatt (1.3 hp).

Bodies and chassis

Solar cars have very distinctive shapes as there are no established standards for design. Designers aim to minimise drag, maximise exposure to the sun, minimise weight and make vehicles as safe as possible.

In chassis design the aim is to maximise strength and safety while keeping the weight as low as possible. There are three main types of chassis:

space frame

semi-monocoque or carbon beam

monocoque

The space frame uses a welded or tubed structure to support the body which is a lightweight composite shell attached to the body separately and the loads. The semi-monocoque chassis uses composite beams and bulkheads to support the weight and is integrated into the belly with the top sections often being attached to the body. A monocoque structure uses the body of the car to support the weight.

Composite materials are widely used in solar cars. Carbon fibre, Kevlar and fibreglass are common composite structural materials while foam and honeycomb are commonly used filler materials. Epoxy resins are used to bond these materials together. Carbon fibre and kevlar structures can be as strong as steel but with a much lighter weight.

Solar car races

The two most notable solar car races are the World Solar Challenge and the North American Solar Challenge. They are contested by a variety of university and corporate teams. Corporate teams contest the race both to give its design teams experience in working with alternative energy sources and advanced materials. GM and Honda are among the companies who have sponsored solar teams. University teams enter the races because it gives their students experience in designing high technology cars and working with environmental and advanced materials technology. These races are often sponsored by agencies such as the US Department of Energy keen to promote renewable energy sources.

The cars require intensive support teams similar in size to professional motor racing teams. This is especially the case with the World Solar Challenge where sections of the race run through very remote country.

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

External links

Categories: Electric vehicles