Alternative energy: The solar sandwich

With a new technology win photovoltaic manufacturers twice as much electricity from sunlight as before. Corporations promise of solar energy for the future, which is as cheap as electricity from coal power plants. This is made possible a record yield with a simple trick.

A strong magnifying glass and a sheet of newspaper – all it takes to light a campfire. At least as long as the sun shines strong: She has so much energy that the paper bursts into flames when the concentrated solar rays hit it.

Use this as simple and effective principle to the photovoltaics industry. Companies and research institutes working on innovative solar modules, which are equipped with special lenses. As a magnifying glass to concentrate the rays of the sun around the 500- to 1000-fold – and hence their energy content. The solar cells can thus gain very small area much electricity.

The CPV technology (Concentrated Photovoltaics) scientists achieve in the laboratory is already efficiencies of 40 percent and more. For factory-made CPV modules figure is still 30 per cent. An enormously high value – the commercial silicon modules are just half.

And while manufacturers of conventional modules tedious to every tenth of a percent more efficient fight the concentrator specialist screw the efficiency of their products in the shortest time equal to whole percentage points upwards. The end of the story is far from being achieved: “I assume that we are at the cellular level to break the fifty percent mark in the next few years,” says Andreas Bett from the Fraunhofer Institute for Solar Energy Systems, the large proportion of the has development of this technology. Bed is the end of October awarded the German Environmental Award, he is one of three winners this year.

Solar Power Industry – The dirty side of clean electricity

To improve the environmental performance of their systems, the solar industry is working on more environmentally friendly manufacturing processes and efficient recycling systems.

Anyone investing in a photovoltaic system, usually has clear goals: He wants to protect the environment and sell the solar power profitably. Thanks to generous funding the sun harvest is now economically very attractive in many countries. In the environmental performance but there is a catch: While convert solar light into electricity without emissions, but their preparation takes a lot of energy.

“In a typical Central European exposure it takes two and a half years for a conventional crystalline system has generated the energy that has gone into their production,” said Mariska de Wild-Scholten by the Dutch company SmartGreen scans. The company specializes in the life cycle analysis of photovoltaic technology.

Thin film production is hardly effective: Compared with the crystalline technique in which one silicon blocks, first into thick slices (wafers) sawed to then further process, the thin film fabrication, although less costly; to produce the corresponding modules, it is sufficient to coat a cheap glass with a wafer-thin semiconducting layer. Nevertheless, the energy payback time of these systems amounts to, depending on the semiconductor material used, up to two years, so de Wild-Scholten.

Compared to gas and coal power plants, photovoltaics (PV) has of course still a very good ecological balance. While never recoup Fossil fuel-fired power plants because of their constant carbon dioxide emissions in energy and environmental technology, bring solar cells at a lifetime of 30 years at least twelve times as much energy in, as their production has consumed. But the carbon dioxide emissions in the solar industry could rise overall concern: Last year, the high demand the world module production operation according to the US market research firm iSuppli to 8,000 megawatts (MW) to a peak of 18,000 MW, 2011 are modules with a total capacity of 26,000 MW running from the tapes. This increases the amount of carbon dioxide, the solar plants blown into the air each year by several million tons.

In order to maintain its green image, the industry wants to limit their emissions. Triple Green – triple green – is the motto: first modules generate green electricity, are second on resources produced and thirdly recycled after their lifetime in ecologically built, supplied with green energy plants. For the organization of Altmodul recycling in Europe, the association PV Cycle was founded in 2007 specifically.

So far, the industry defiled their clean but at the beginning of the solar value chain, in the Siemens-reactors for silicon production. The semiconductor is manufactured using melting, purification and distillation processes at high temperatures of quartz. The energy needed for this game a solar system after nine months again explains the Wild-Scholten. The wafer and cell production is anything but environmentally friendly: For wafer cleaning, car manufacturers acids and alkalis. For electrical alignment bringing phosphorus and boron in the cells, and the soldering lead comes into play. These chemicals and heavy metals can be found later in the effluents of the factory again.

Thin film modules are not acceptable. Some are made of cadmium telluride (CdTe), a compound of two elements, which are health and environmental hazard when they are released. When thin film silicon manufacturers cleaned their vacuum chambers with nitrogen trifluoride (NF3). The greenhouse gas reacts with the silicon that sticks to the coating on the walls of the chambers. So careful also operate the business – something NF3 always escapes: “17 percent of the nitrogen trifluoride produced reach during its product life cycle in the atmosphere”, explains Andreas Weisheit, responsible for the PV business of Munich gas supplier Linde.