For 13-year-old Jia Quan, a middle school student in Beijing, his only impression of solar energy in the past was that it could be converted into electricity and stored in a battery. Some road lamps somewhere in Beijing were the only kind of application of solar energy he encountered.

It amazed him that solar energy could do much more than he ever expected. The teenager learned of this potential as he listened to a report on solar energy utilization presented by Signe Antvorskov, an engineer from Denmark working on household energy efficiency. According to Antvorskov, who appeared at the International Solar Energy Society's Solar World Congress in Beijing, held between September 18-21, solar cells can help indoor heating, ventilation, and even cooling.

In the house pictures she displayed, the roof shingles are coated with photovoltaic cells made of amorphous silicon and look much like ordinary roofing shingles. The electricity generated from the roof can basically satisfy a household's daily need.

Nowadays, solar energy technology offers an exciting potential for development of sustainable and eco-friendly energy systems.

Besides electricity generation, another important utilization of solar energy so far is for heating purpose, according to Yin Zhiqiang, professor of Department of Electronic Engineering of Tsinghua University.

Owing to a high cost of electricity generation from solar energy, China has focused on the solar heat potential, accounting for more than half of the world's use for such technology. A major part of thermal utilization in China is for low-temperature hot water in common households. It is expected that a further progress of it, producing higher-temperature water, can also be applied to industrial and agricultural production.

Compared to a solar cell, which can only utilize approximately 9 to 15 percent of energy from the sun, a solar water heater is more efficient and can convert as high as 50 percent of solar energy.

According to Yin, the invention of the vacuum solar collecting glass tube has made solar energy also available for northern residents in cold winter, as the vacuum tubes have good thermal insulation properties and the water does not freeze.

Due to environmental concerns, more cities are forbidding burning coal for heating. Compared to the high cost of burning oil and gas, solar energy can be a cheaper and clean alternative, Yin believes.

Because a large water tank is usually placed on a building's roof as part of the solar power apparatus, it is not aesthetically pleasing. And while installing a water pump can allow the water tank to be on the ground, it is an expensive exercise. So a compact arrangement of the collector and tank is still widely applied, according to Yin.

A major challenge of using the thermal heater in the cities is applying it on high-rise buildings, because the energy collected cannot satisfy the use of every household, particularly those living in the lower stories.

By the end of 2006, statistics show that 90 million square meters of solar water heating was already in use around the country. That could save more than 10 million tons of standard coal being burned each year. However, it only occupies a tiny part of the total energy consumption in China, which used more than 2 billion tons of coal in 2006. It is estimated that 500 million square meters of solar water heating will be installed by the year of 2020.

(China Daily 09/24/2007 page8)