Project SINAG : The First Philippine Solar-Powered Car

What is a Solar Car

a solar car projection modelA solar car is a vehicle which runs on solar energy converted into electricity by photovoltaic cells. While solar cars are not currently a practical form of transportation they are raced in competitions such as the World Solar Challenge. These meets promote the development of alternative energy technology such as solar cells.

The following descriptions are specific to solar cars designed for "ray-ces" such as the World Solar Challenge.

Driver's cockpit

The driver's cockpit usually has a single seat with a few cars containing room for a second passenger. They are hot due to the solar panels and are very cramped, with few of the comforts of a normal automobile. They do, however, 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.

Electrical system

The solar car is propelled by an electric motor instead of the usual petrol-powered engines. It doesn't need gas. The electric motor gets its power from the Sun through a solar array or the battery pack or both. The solar array consists of hundreds of solar cells each converting the Sun's energy into electrical energy. Each cell can produce about 3 watts of power at full irradiance from the sun. The entire array is capable of producing a total peak power of about 1200 watts. This is roughly equivalent to the power consumption of a typical electric iron.

The solar cells to be used in the array are manufactured in the Philippines by Sunpower Corporation through its Laguna factory. These Sunpower cells are recognized to be the best of its class in the world providing cells that are more than 21% efficient whereas the nearest competitor has efficiencies of only around 17-18%. Each cell is about 12.5 cm by 12.5 cm in size.

Maximum power is obtained from the solar array through an electronic device called maximum power trackers or MPPT. The trackers manipulate the operating point of the array to derive the most power from it. This process is done automatically through software embedded in each MPPT.

Since the Sun will not always be up or partially blocked by clouds, the battery pack is essential in providing a second source of power for the electric motor. The pack consists of hundreds of Lithium Polymer cells which are very energy dense. When not driving the car or when traveling at low speeds and consuming very low power, the solar array can charge the battery pack. During the World Solar Challenge, the batteries can be charged by the array before and after the official race period of 8am to 5pm.

The electric motor takes the place of engines in conventional cars. The motor used is highly efficient in converting electric energy to mechanical energy needed to propel the car. The configuration of the motor is special in that it is mounted in the wheels. This helps keep the efficiency high.

The motor controller functions as the throttle control. In conventional cars, you apply pressure to the gas pedal to release varying amounts of fuel into the engine. The solar car uses the motor controller to supply varying amounts of electric current to the motor causing it to speed up or slow down.

Body and Mechanical systems

Sinag will be using a shell/body design that is very aerodynamic. Air friction offers resistance to the car while it travels. The faster the car, the greater is the resistance. To overcome the resistance to travel at a particular speed, the car has to supply enough power. To be efficient, the car shell/body should be aerodynamic to cause the air to flow smoothly through it.

The mechanical systems 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. Solar cars have a wide range of suspensions because of varying bodies and chassis. 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.

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

Solar array

The solar array consists of hundreds of photovoltaic solar cells converting sunlight into electricity. A solar array acts like a lot of very small batteries all hooked together in series. The total voltage produced is the sum of all cell voltages. 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 over 2 kilowatts (2.6 hp).