Electricity by Solar Radiation  Printable view
Fig. 1   The sun is an inexhaustible source of energy.

We receive a huge amount of radiation from the sun every day. Have you imagined how much sunlight falls on Hong Kong every day? From statistics gathered at the Hong Kong Observatory [1], we know that on average Hong Kong receives about 14.5 MJ of solar radiation energy per square metre every day. So how much solar radiation energy does all of Hong Kong receive? The total land area of Hong Kong is about 109 m2 [2], this amounts to a total energy of 1.45 × 1016 J. In fact, this is about 40 times the electrical energy generated by the two power companies in Hong Kong every day during the year 2003! Could we use part of this energy, for example, to power our home appliances or our transportation system?

Is solar electricity practical?

Apparently, we could benefit greatly by turning even a very small percentage of solar radiation energy into useful electrical energy. A photovoltaic cell (solar cell) is a device that is commonly used to collect radiation energy and convert it into electrical energy. Solar cells are grouped to form flat panels for collecting sunlight. They are called solar panels. However, building very large solar arrays (collections of many solar modules or panels) to collect and convert solar energy for our daily use is very expensive and impractical. Although solar electricity is not yet a major energy source in urban areas, it is used in some developing countries and in some remote areas of developed countries. Do you know how much money you would have to invest in order to install a solar electricity system for our homes? Are there more practical applications for solar electricity? Click on the following activity to gain more insight into the use of solar electricity.

Fig. 2   A solar module can collect solar energy and convert it into electrical energy. Fig. 3   Building a large array of solar panels is very expensive. (image courtesy of DOE/ NREL)

Activity: Is solar electricity suitable for Hong Kong?