Thinly sliced cells slash solar power costs

Startup Twin Creek Technologies is attacking the cost of solar by getting more bang from a wafer of silicon.

After four years of work, the San Jose, Calif.-based company today is coming out of stealth and introducing its product, a machine designed to slash the cost of solar cell manufacturing. The company claims its Hyperion system cuts the cost of making a solar cell in half and brings total production cost from about 85 cents a watt today to around 50 cents.

Hyperion is now being evaluated by leading solar manufacturers and the company expects to have a number of them operating by next year, according to CEO Siva Sivaram. The machine also allows solar makers to make flexible silicon cells.

In an effort to lower material costs, solar manufacturers over the years have been able to use thinner wafers. Square wafers are sawed off from ingots of very pure silicon. During production, wafers are treated and turned into solar cells. Then cells are assembled into a solar panel.

But getting beyond 200-micron thickness has problems because wafers get brittle, which limits the costs which can be saved on materials, Sivaram said. The Hyperion system uses a technique called proton induced exfoliation to create slices as thin as 20 microns from existing wafers. "It's like a ream of paper and you're taking sheets off of it," Sivaram said.

The machine blasts hydrogen ions, or protons, at silicon wafers. The protons embed themselves as a layer of bubbles. Then, the machine heats up the wafer to expand the bubbles to break off a sheet from the wafer.

This effect of hydrogen ions implanting themselves has been observed for decades, but using it for solar cell production required totally different engineering with high energy and high doses, Sivaram said. The thinner cells are as efficient as thicker ones and are flexible so they could be used for solar awnings or other building-integrated photovoltaics.

The company itself is stacked with an experienced group of executives and engineers, including co-founder and chief scientist Chris Petti. It has raised $93 million from Crosslink Capital, Benchmark Capital, Artis, DAG Ventures, and a Taiwanese funding, according to a representative.

Twin Creek Technologies has also received $30 million in loans from the state of Mississippi, where it has a demonstration plant. There solar manufacturers can come and test their specific production processes with Hyperion, Sivaram said.

If the company does sign on manufacturers to use its equipment, it could result in a significant cost reduction for solar power consumers. Sivaram estimates that getting to 50 cents a watt production costs would bring the industry to about $1 per watt installed, a price that could make solar cheaper than grid power in many places.

The effect on market prices, even if the product is purchased by many manufacturers, would take time, however. Hyperion can produce cells at a rate of six megawatts per year, which is a small fraction of the solar industry's production.

Still, Hyperion and the work of other potentially disruptive silicon cell manufacturing technologies, such as one developed by startup 1366 Technologies, point to possible breakthroughs which could benefit consumers and the industry. Right now, cutthroat price competition has led to several bankruptcies and few solar manufacturers actually making money, say analysts.

Even though Twin Creek has seen interest from solar manufacturers, Sivaram said his biggest concern is that solar manufacturers will be reluctant to adopt Twin Creek's new equipment, which costs millions of dollars. "There's no other way for the solar industry to proceed without getting more value from the materials they use," said Sivaram.