With supplies of fossil fuels rapidly dwindling, the pressure is on to develop renewable sources of energy. The sun is the primary energy source of all life in the planet, and many believe that solar power could be the ultimate carbon-neutral solution.

A prototype Roof Solar Collector

A prototype Roof Solar Collector © Nakhon Phanom University

The use of solar panels is gaining popularity, but existing technologies are expensive and inefficient. New research across Asia aims to change this, using innovative new technologies to ensure continued improvement.

Solar power goes organic

Much work is focused on developing solar cells made of low-cost materials that are cheap and easy to manufacture. These take advantage of the photoelectrical properties of organic pigments or dyes, and are known as ‘dye sensitised solar cells’ (DSSCs).

DSSCs typically contain a layer of light-absorbing dye, such as a ruthenium dye, along with a layer of titanium dioxide (TiO2) particles to maximise the surface area. When sunlight hits the dye, photons with sufficient energy are absorbed and the dye enters an excited state, which causes negatively charged electrons to be passed on to the TiO2. The electrons lost by the dye are replaced by those stripped from iodide ions in an electrolyte, a substance carrying charged particles.

This is a popular emerging technology, and these kinds of solar panel are expected to make a significant commercial impact within this decade. At the moment, however, they are very inefficient.

An on-going project led by Menandro Marquez and Florentino Sumera at the University of the Philippines Diliman is finding new ways to fabricate DSSCs in an attempt to cut costs and boost efficiency. The materials used as sensitisers consist of polyaniline, which is cheap and lightweight, coupled with an organic dye. The team are planning to go one step further and incorporate natural dyes taken from native plants in the Philippines to try and reduce local costs.

Record breakers

Meanwhile, at the National Institute for Materials Science (NIMS) in Japan the world efficiency record for a DSSC was recently broken. The highest energy conversion efficiency in DSSCs had remained at 11.1 per cent since 2006, but the NIMS Photovoltaic Materials Unit has succeeded in improving conversion efficiency to 11.4 per cent. This was made possible by the development of a new additive material which makes the dye even more sensitive to light. This improves the efficiency of the cells in the visible light region by approximately 80 per cent therefore increasing the amount of electrical current generated.

Solar panels with higher conversion efficiency are more cost effective, and scientists hope that over the next few years this kind of technology will help boost their popularity as a renewable source of electricity.

Using the sun to keep cool

Scientists at Nakhon Phanom and Chiang Mai Universities in Thailand are using the sun’s energy in a very different way. They’ve developed Roof Solar Collectors (RSCs), which could help cool down and ventilate houses in an environmentally friendly way, reducing the need for expensive air conditioning.

Roof Solar Collectors use the sun’s energy to cool down houses

Roof Solar Collectors use the sun’s energy to cool down houses © Nakhon Phanom University

The technology itself is beautifully simple: energy from the sun heats up the roof tiles, and this in turn heats up the air inside the ‘chimney’ – a space between the roof and the ceiling. Because of the tendency of hot air to rise, the warmed air travels up the chimney and out into the atmosphere. This movement causes the warmest air in the house to be drawn into the chimney, leaving much cooler air behind.

The team have been carrying out laboratory-scale experiments to try and optimise the design, focusing on the relationship between heat flux (rate at which heat is transferred) and the rate at which the air flows. At the moment, RSCs can decrease heat load from roofs by around 58 per cent, and provide good ventilation inside houses. Given that RSCs are straightforward to construct, and the materials involved fairly inexpensive, this technology could make a real difference in developing countries.

For further information contact:

M. Marquez and Dr Sumera
Institute of Chemistry
University of the Philippines Diliman
Email: m_c.marquez@yahoo.com
Dr Liyuan Han
Photovoltaic Materials Unit
National Institute for Materials Science, Japan
Email: Han.Liyuan@nims.go.jp
Mr Narongrit Auppapong
Nakhon Phanom University
Email: narong.aup@hotmail.com
Dr Yottana Khunatorn
Department of Mechanical Engineering
Chiang Mai University, Thailand
Email: piakman@dome.eng.cmu.ac.th