28 May 2008

Credit: IBM

IBM Research Could Lead to Reduced Costs in Solar Farm Technology

By borrowing innovations from its own R&D in cooling computer chips, the team was able to cool the solar cell from greater than 1,600 degrees Celsius to just 85 degrees Celsius.

In the same way that children in science class use a magnifying glass to burn a leaf, IBM scientists are using a large lens to concentrate the sun's power, capturing a record 230 watts onto a centimeter square solar cell, in a technology known as concentrator photovoltaics, or CPV. That energy is then converted into 70 watts of usable electrical power, about five times the electrical power density generated by typical cells using CPV technology in solar farms.

If it can overcome additional challenges to move this project out of the lab, IBM believes it can significantly reduce the cost of a typical CPV-based system. By using a much lower number of photovoltaic cells in a solar farm and concentrating more light onto each cell using larger lenses, IBM's system enables a significant cost advantage in terms of a lesser number of total components.

For instance, by moving from a 200 sun system ("one sun" is a measurement equal to the solar power incident at noon on a clear summer day), where about 20 watts per square centimeter of power is concentrated onto the cell, to a 2,300 sun system, where approximately 230 watts per square centimeter are concentrated onto the cell system, the IBM system cuts the number of photovoltaic cells and other components by a factor of 10.

"We believe IBM can bring unique skills from our vast experience in semiconductors and nanotechnology to the important field of alternative energy research," said Dr. Supratik Guha, the scientist leading photovoltaics activities at IBM Research. "This is one of many exploratory research projects incubating in our labs where we can drive big change for an entire industry while advancing the basic underlying science of solar cell technology."

The trick lies in IBM's ability to cool the tiny solar cell. Concentrating the equivalent of 2,000 suns on such a small area generates enough heat to melt stainless steel, something the researchers experienced first hand in their experiments. But by borrowing innovations from its own R&D in cooling computer chips, the team was able to cool the solar cell from greater than 1,600 degrees Celsius to just 85 degrees Celsius.

The initial results of this project were presented at the 33^rd IEEE Photovoltaic Specialists conference last week, where the IBM researchers explained in detail how their liquid metal cooling interface is able to transfer heat from the solar cell to a copper cooling plate much more efficiently than anything else available today.

The IBM research team developed a system that achieved promising results by coupling a commercial solar cell to an advanced IBM liquid metal thermal cooling system using methods developed for the microprocessor industry.

Specifically, the IBM team used a very thin layer of a liquid metal made of a gallium and indium compound that they applied between the chip and a cooling block. Such layers, called thermal interface layers, transfer the heat from the chip to the cooling block so that the chip temperature can be kept low. The company says that its liquid metal solution offers the best thermal performance available today, at low costs, and the technology was successfully developed by IBM to cool high power computer chips earlier.

Credit: IBM

While concentrator-based photovoltaics technologies have been around since the 1970s, they have received renewed interest in recent times. With very high concentrations, they have the potential to offer the lowest-cost solar electricity for large-scale power generation, provided the temperature of the cells can be kept low, and cheap and efficient optics can be developed for concentrating the light to very high levels.

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

The goal of the projects is to develop efficient photovoltaic structures that would reduce the cost, minimize the complexity and improve the flexibility of producing solar electric power.

israel21c.net
January 13, 2008

Solar energy is an exciting option to greenhouse gas producing power sources, because the sun offers unlimited power, and zero carbon emissions. But to make it a real-world energy alternative, kinks in the system need to be addressed.

One of the biggest drawbacks to using solar energy is its unreliability: the sun's rays are not constant, and the power cannot be stored. The Israeli company EDIG, working in traditional markets of electro-mechanics since 1971, believes it has the solution, in the form of a low-cost hybrid generator.

Through subsidiary EDIG Solar, the company plans to make solar energy a viable power alternative. The company's power plant is hybrid, meaning that like electric cars, the system's turbines can adapt to more than one energy source.

During a rainy day, the solar turbines can switch over and run on traditional or alternative fuel.

"It's modular, meaning it can easily be increased in size, and it is flexible in terms of fuel use. It can be powered by bio-diesel, bio-gas or fossil fuels," explains the company's CTO Pinhas Doron, an engineer.

When it comes to alternative energy options, one technology does not fit all, he says. "Every application has to be examined on its own merit, and the best solution applied to it. Our solution works well for grid connected electricity, where there is ample sun."

Based on the research of Prof. Jacob Karni, director of the Center for Energy Research at the Weizmann Institute in Israel, EDIG's technology attracts the sun and concentrates it by way of tiny mirrors on the ground.

The thermal energy generated by the sun drives turbines in a tower, the same turbines that can be powered by traditional fuel, the moment a cloud passes overhead, or at night when the sun sets.

And in doing this, "our hybrid solution addresses the issue of intermittency of solar radiation," says Doron.

Admittedly, he will not try to sell this solution to the northern states in America, or to Canadians, but it would be perfect for places where there is direct radiation, such as in the southwest USA, southern Spain, or in India, he says.

EDIG recently built a 100 kW pilot plant study in Nanjing, China. It included a power conversion unit (a solarized gas turbine and a solar receiver), which was installed on a tower, and a field of heliostats (sun-tracking mirrors).
The unit was fully operational and supplied power to the local electric grid, says Doron. "We proved our concept - we connected to the grid and operated seamlessly," he reports. The next step is building a plant in Israel's Arava Desert, which should be ready by next year.
While the company is not reinventing the "solar" wheel, its IP rests in at least two areas, says Doron. It's solar "receiver" is based on patented Weizmann technology, and the modifications on the turbine, which allows it to switch energy sources and at high temperatures, without the user noticing it, was difficult to overcome.

Of course, when the solution is being operated in hybrid mode, there are "no zero emissions," says Doron. "But during optimal conditions of sunshine, it could be. Fuel use would be minimal," he stresses.

Will this be a solar solution we can all live with? Avraham Israeli, a private consultant and previously a trade exec at Israel's Export Institute for clean technologies, recommends EDIG as the most promising solar energy company in Israel, if not the world.

"The company is implementing a technology of solar thermal electricity generation. It seems to be the most cost-effective technology in the market," he told ISRAEL21c.

And if the new hybrid plant from Israel doesn't live up to the promise and hype, there is always the sun.

Dormant since the early 1990s, Concentrated Solar Power is undergoing a renaissance in the solar-rich areas of the world including Spain and the Southwestern US, according to a new study from Emerging Energy Research, a leading research and advisory firm analyzing clean and renewable energy markets. According to EER, solar CSP is the fastest growing utility-scale renewable energy alternative after wind power, with up to $20 billion expected to be invested in solar CSP over the next five years.

"With natural gas prices tripling and current volatility expected to continue, CSP is well-positioned to compete against other electricity generation technologies in the near-to-medium term," says EER Senior Analyst Reese Tisdale. "In countries such as the US and Spain with higher solar resources, land availability, and sufficient government support to kick-start the industry, utility-scale solar CSP technology has the potential to become an integral part of the generation mix."

Posted: 14 Nov 2007 01:13 AM CST