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Solar Panel Payback Time

When it comes to solar cells, there is good news and there is bad news. First the bad news. Installing photovoltaic solar panels on your roof will cost you more than you save on electricity bills before the panels have to be replaced. The good news is that you will reduce your carbon footprint and save energy. That is the conclusion drawn from a study published in Inderscience International Journal of Environmental Technology and Management.

Solar and wind power, and other renewable sources, such as wave and tidal power, represent an energy source that could underpin a sustainable energy policy by minimizing our reliance on fossil fuels and at the same time reducing carbon dioxide and other pollutant emissions. The main barrier that has so far hindered the development of a steady market for such "renewable" systems has been their cost.

According to Giacomo Bizzarri of the University of Ferrara and Gianluca Morini of the University of Bologna, the amount of electricity that can be saved over the lifetime of a domestic PV panel is about 2000 kWh per square metre for thin film modules, with an expected life of 20 years, single-crystalline silicon devices with an anticipated lifespan of 25 years fare better producing 4400 kWh per square metre. However, the initial costs are about 2.5 times the value of the electricity produced, the researchers say.

The pair carried out a cost-benefit analysis and found that the total energy produced over a two-year period outweighs the energy used in manufacture, installation, and maintenance. Their analysis also shows that the manufacture and use of PV panels produces less pollution than fossil fuel based electricity generation.

The researchers say that their analysis holds even in countries with medium sunshine. This makes PV panels a viable alternative energy supply but will not save you money, unless the price of electricity rises three to four times, which will give a positive internal rate of return.

Bizzarri and Morini point out that cost should not be the only consideration. The total energy and pollution involved in sourcing the raw materials, manufacturing, installing, and maintaining any particular system should also be considered. After all, if it uses far more energy to build a wind farm or install solar panels than the energy they can produce during their lifetime then it does not make environmental or economic sense to install them.

With this in mind, the researchers analysed all the costs from cradle to grave - in terms of energy use, pollution and carbon footprint, and economic - to find out whether photovoltaic cells are a truly viable alternative energy source.

Three different kinds of PV devices were assessed: single-crystalline silicon, polycrystalline silicon, and thin film copper indium diselenide. The team considered the costs from the point of manufacture to end-of-life disposal. "Our study considers the systems through the whole of their life cycle, "from cradle to grave", the researchers explain, "leading to the estimation of the energy, economic and emission payback times."

In their assessment of the three different PV panel types on the south-facing roof of a school in Ferrara, northern Italy, the team found that the energy produced by the panels over their lifetimes considerably overcomes the energy needed during manufacture. In fact, energy costs are recovered within two years in this medium sunshine climate. The team also showed that carbon dioxide emissions are significantly lower over the PV panel lifetime from cradle-to-grave compared with conventional electricity generation. Economic costs, the team found, would only be recouped if the panels remained fully functional for more than twenty years.

The researchers suggest that their study, which takes into account all the hidden costs in terms of energy, pollution, and money, could provide a role model for policy makers considering renewable energy sources.

Albert Ang | alfa
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