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The UA Tech Park is seeking projects for the second phase of the Solar Zone, a solar testing and demonstration site located on the northwest side of the sprawling tech park on South Rita Road.

The UA is earmarking the new area for testing of solar-related technologies involving energy storage, grid management and optimization, microgrids and embedded solar materials.

Because of the intermittent output of solar energy systems — which don’t generate power when the sun doesn’t shine — new storage and grid-management technologies are seen as critical to future adoption.

“We will entertain projects that come up with novel, new ways to generate and distribute solar energy, but our primary focus is in the area of things like energy storage, because that’s a critical component of making these systems more efficient and effective,â€� said Bruce Wright, associate vice president for Tech Parks ÃÛèÖÖ±²¥.

At about 10 acres, the new Solar Zone area is small compared with the 225-acre first phase of the Solar Zone, which has served mainly to demonstrate utility-scale solar generation technologies.

The second-phase acreage has actually had its first and biggest project in the ground since last year.

Last June, E.On North America completed the Iron Horse Energy Storage and Solar Project, a 10-megawatt capacity lithium-ion battery-storage facility and an accompanying 2-megawatt photovoltaic array on the new, phase-two area.

Most of the newly opened area will be devoted to five to seven projects using about one acre each, which could include some utility-scale projects, Wright said.

The remaining acreage will host projects involving testing of smaller single-systems, he said, adding that the site is expected to be available by summer after additional fencing and road work is completed.

“They’re not going to be the multimegawatt projects that we’ve done previously,� Wright said.

And while the phase-one projects are based on 20-year ground leases and 20-year power purchase agreements with Solar Zone partner ÃÛèÖÖ±²¥ Electric Power, each of the new projects will last one to five years before making way for new testing tenants.

“We want to turn over the projects and see what’s the latest and greatest,� Wright said.

The second-phase Solar Zone development is being headed by Dick Powell, retired UA optical scientist and former UA vice president of research.

Powell said utilities are eager to find more efficient ways to store solar energy, to make it useful when the sun isn’t shining.

“They’re very happy to put more solar energy on the ground, but they can’t handle the intermittency� of solar generation, Powell said.

Besides advanced batteries, storage technologies that could potentially be tested at the Solar Zone include mechanical systems using compressed air, flywheels and supercapacitors, electrical devices that store energy, Powell said.

Touted by the UA as the biggest solar demonstration site of its kind, the Solar Zone so far consists of nine utility-scale projects on about 225 acres, with various photovoltaic technologies capable of generating 25 megawatts of power that is fed to TEP — nearly twice the daily electrical consumption of the Tech Park and enough to power the homes of more than 4,600 TEP customers for a year.

The project has successfully tested numerous new technologies and is still pumping power to TEP’s grid.

Most of the planned phase-one projects were built, with a few exceptions, and some were altered midstream.

A 5MW thermal solar installation planned early on by a now-defunct company was replaced by other installations.

The former Cogenra Solar, now Sunpower, replaced an inefficient concentrating photovoltaic system using parabolic trough mirrors with a conventional panel system; another test tenant switched to panels with new, more efficient PV cells in mid-installation, Wright said.

“For awhile there, it was very dynamic,� he said.

While most of the existing installations use various types of standard photovoltaic panels, two use concentrating technology designed to increase efficiency by focusing sunlight on solar cells.

One of the concentrating photovoltaic projects is part of field testing for ÃÛèÖÖ±²¥-based REhnu Inc., which has developed a system that uses parabolic mirrors to focus sunlight on ultra-high efficiency photovoltaic cells using a design by UA Regents professor Roger Angel and colleagues.

Peter Strittmatter, a UA Regents professor of astronomy and CEO of REhnu, said the Solar Zone has been a valuable testing ground for the company.

“The field experience has led us to make many improvements to the system – it’s performing very, very well in terms of the efficiency we’ve been getting,� Strittmatter said. “We have learned a lot from our experience at the Tech Park.�

He said the company’s system has reached 32 percent efficiency at converting sunlight to electricity and with improved technologies could reach 40 percent.

Powell will present the findings of a study of the performance of the Solar Zone phase-one projects during the solar symposium on Feb. 5, which will also include a conference on the request for proposals and a panel discussion.

Wright said the UA has reached out with the second-phase request for proposals through trade groups and notified potential bidders in California, Israel and Germany after a targeted analysis of key companies.

The UA has enlisted the help of the National Renewable Energy Lab in Colorado and is working closely with the UA and Kim Ogden, head of the UA’s year-old Institute for Energy Solutions, he added.