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IBM's concentrator photovoltaics more efficient

John-Paul Kamath

IBM says it has developed more efficient photovoltaic cells - the technology that converts light directly into electricity - that could reduce the cost of producing solar electric power.

Any way to save money by using renewable energy would help IT managers scale their IT infrastructures while cutting energy costs. According to analyst firm IDC, about 50 cents is spent on energy for every dollar of computer hardware. This is expected to increase by 54 per cent to 71 cents over the next four years.

IBM scientists are using a large lens to concentrate the Sun's power to capture a record 230 watts onto a centimetre square solar cell.

The technology is called concentrator photovoltaics and employs the principle of using a magnifying glass to burn a leaf. IBM's concentrator photovoltaics (CPV) concentrate the sun's energy to produce more electricity per square centimetre than conventional CPV solar cells. The IBM CPV produces approximately 70 watts of usable electrical power, about five times the electrical power density generated by typical solar cells using CPV technology in solar farms.

If it can move the project from laboratory to fabrication, IBM believes it can significantly reduce the cost of a typical CPV-based system.

Solar cells have many applications. Individual cells are used for powering small devices such as electronic calculators and photovoltaic arrays can generate a form of renewable electricity, particularly useful in situations where electrical power from the grid is unavailable, as in remote areas.

Search engine giant Google has converted part of its Californian headquarters to run partly on solar power. It aims to eventually produce 30% of the power it needs at its headquarters from the sun.

The solar electricity system has a total capacity of 1.6 megawatts. It is expected to be the largest solar power installation on a business site in the US, with 9,212 solar panels.

But IBM said its system uses a much lower number of photovoltaic cells in a solar farm and concentrates more light onto each cell using larger lenses. This reduces the number of components needed and saves money.

A 'sun' is a unit of measurement equal to the solar power that can be generated at noon on a clear summer day. By moving from a 200-sun system - where about 20 watts per square centimetre of power is concentrated onto the cell - to the IBM Lab results of a 2300 sun system - where approximately 230 watts per square centimetre are concentrated onto the cell system - the IBM system cuts the number of photovoltaic cells and other components by a factor of 10.

The trick lies in IBM's ability to cool the tiny solar cell. Concentrating the equivalent of 2000 suns on such a small area generates enough heat to melt stainless steel, something the researchers experienced first hand in their experiments. But borrowing innovations from its own R&D in cooling computer chips, the team was able to cool the solar cell from greater than 1600° Celsius to just 85° Celsius. IBM has developed liquid metal thermal cooling taken from microprocessors.

GB Patnaik from the Alternative Energy Department of India has overseen the deployment of solar panels to schools in villages without power lines, to power computers.

"The cost of running solar panels to power computers in one school would cost about £1,000, which is expensive, but because some have no power at all it makes it necessary," he said.

GB Patnaik said the announcement of a breakthrough from IBM was welcomed if it eventually lowered the cost of powering computers with solar energy. However, he that factors such as bad weather affects solar energy as the primary source of power in computing.

"Solar power is useful in areas where there is no power to begin with, but even at a reduced cost, businesses would be reluctant to make it their primary source of power," Patnaik said.

IBM is exploring four main areas of photovoltaic research: using current technologies to develop cheaper and more efficient silicon solar cells developing solution-processed, thin-film photovoltaic devices concentrator photovoltaics and future-generation photovoltaic architectures based on nanostructures such as semiconductor quantum dots and nanowires.

In addition to the photovoltaic research, IBM is focused on several areas related to energy and the environment. These include: energy efficient technology and services carbon management advanced water management intelligent utility networks and intelligent transportation systems.





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