Greenvolts seeks advantage in custom cells
Greenvolts sees its investment in leading the exploitation of a new generation of III-V multi-junction solar cells as a key element of its future strategy.
The San Francisco concentrator photovoltaics (CPV) company, currently in the process of building its "GV1" power plant, is joining forces with the US National Renewable Energy Laboratory (NREL) to develop advanced cells (see related story).
The two-year project, to which NREL is committing $0.5 million and Greenvolts a "significant match" on top of this amount, will focus on the inverted metamorphic (IMM) structure "“ which until recently held the world record for solar cell efficiency.
Bob Cart, the Greenvolts CEO, told compoundsemiconductor.net that using a proprietary cell design would provide the company with a significant advantage:
"I believe long-term success for a CPV system will be the result of a close relationship between the solar cell provider and the system designer," said the CEO.
"Only then can you truly make a meaningful leap forward in overall system efficiency, reliability and cost."
Cart s plan is to provide system, optics and optoelectronic integration expertise as the NREL team works to develop a customized version of the IMM structure that is suited to Greenvolts' approach.
Rather than use transmissive optics, such as Fresnel lenses, to concentrate the Sun's rays onto the cells in their systems, Cart and his colleagues have instead decided to use parabolic mirrors "“ an approach also favored by SolFocus.
He says that this approach should ultimately deliver a much higher concentration ratio than is possible with lens-based systems.
Although it will be intimately involved in the IMM cell development, Greenvolts does not plan to manufacture its own cells in the future. Instead, a foundry partner will be employed to scale up to volume requirements.
But the 2 MW GV1 installation, currently under construction in the hills 50 miles to the east of San Francisco, will not be using the customized cell designs.
"The plan is for the GV1 project in Byron to use standard-stack multi-junction cells," said Cart. "We do not plan to retrofit the GV1 site, [and] the IMM cells will be used in future projects."
