In our previous article on ‘electric cars’, we made the point that if the energy source isn’t green, then the electric car isn’t as green as we would like to believe. “Solar cars” are also considered ‘electric cars’, but in theory their power source is the energy of the sun. They use photovoltaic cells to convert energy from sunlight into electricity.
Let’s start at the beginning to get a better understanding of the process. Alexandre-Edmond Becquerel (24 March 1820 – 11 May 1891) was born in Paris. In 1839, at the tender age of 19, he was experimenting in his father’s laboratory, and created the world’s first photovoltaic cell. A photovoltaic (PV) cell (which is also known as a ‘solar’ cell) is an electronic component that generates electricity when exposed to photons, or particles of light. As a result of his discovery, this process (i.e. the photovoltaic effect) is also known as the “Becquerel effect”. Only many, many years later in the 1960s did these cells find their first practical application – in satellite technology. From the end of the 80s, solar panels (which are made up of PV cells) started becoming popular – and the variety of uses has steadily grown from there. In a nutshell, a photovoltaic cell is made of semiconductor materials that absorb the photons emitted by the sun and generate a flow of electrons.
Lithium-ion batteries are, unfortunately, extensively used in solar powered cars owing to their high charging-discharging efficiency, high charging density, and light weight. Lithium-ion batteries can provide three times the energy density of conventional rechargeable lead batteries. It is estimated that these batteries will account for over 90% of the market share through 2031. Yet, as we saw in our previous article, there are many and varied issues surrounding Lithium – not least of which is the limited availability (and consequent high prices) and non-green, water-intensive mining issues. We’ll explore the issues of battery alternative in another article.
The expected advantages of solar cars are the money saved on fuel, the fact that they are sustainable and environmentally-friendly (or theoretically more so that vehicles running on fossil fuels), there are no additional costs other than replacing the batteries, and they do not cause noise pollution or air pollution (after manufacture).
A major disadvantage of solar power is the lack of reliability at the energy source. As it relies on the sun, electricity cannot be generated during the night, or when there is continuous bad weather. Which means you either need to store excess energy made during the day or connect to an alternate power source such as the local utility grid. I am told that, on a clear day, the earth’s surface receives a little over 1 kWh of solar energy per square meter (actually around 1370 watts at “peak sun hours”). If there are four hours of full sun per day, and the efficiency of the cell is about 20%, then you’re likely to get 0.80 kWh per day. An average electric car consumes approximately 0,20 kWh/km. Do the maths and you’ll see the issue with pure solar power…
Excessive solar panels on a car have three issues – space (and the consequent lack of aerodynamics), weight and cost. Solar films have been developed, which are much lighter – but also less efficient… Factor in the weight of the battery / batteries, and you have real issues. Even an accumulation of dirt on the car could create less efficient charging. Whilst there has been great progress on all fronts, so far none of the vehicles rely on solar energy alone. Many designs are not practical in real life, mostly accommodating one person and no luggage. Safety also remains an issue, as they are built with ultralight materials that would likely not survive even a minor crash.
The Lightyear 0 is an innovative solar car which is road-legal, and the first deliveries are expected as early as November this year. The vehicle promises to give drivers in excess of 1000 km between charges. It charges on-the-go, gaining up to 70 km of range per day from the sun alone. These vehicles are built to charge from the sun or, if needed, even a regular household socket! It is a fascinating development, and worth visiting their web site / googling the subject (see details in info box).
Pictured above is the “Lightyear 0”.
Solar Car Challenges the world over are fertile ground for much innovation in this field. Who knows? The answers to the solar challenges just may come from a high school student! Our very own Sasol Solar Challenge is about to take place 09 – 16 September right here in South Africa. There are entries from all over the world, a wide variety of different classes and the rules vary for each. Beyond being great fun, very real progress is made each year in the search for solar solutions for transportation.
#SolarChallenge #RenewableEnergy #Technology #FutureMobility #SasolSolarChallenge
Jacqui Ikin & The Cross Country Team
The Lightyear 0: