eIQ’s parallel solar technology solves panel mismatch for aggregate and hot-mix facility
Granite Construction’s new 1.2-MW solar system is up and running at its aggregate and hot-mix facility. The company has its eyes on a four-year return-on-investment, improved power management, optimization of its solar modules and the benefits of a parallel construction, rather than modules set in series.
A key cog in the system’s photovoltaic array is the reduced complexity of San Jose, Calif.-based eIQ Energy Inc.’s parallel solar technology, which boosts the output voltage of copper indium selenium (CIS) thin-film solar modules to the optimum level for the array’s central inverters.
These inverters feed solar energy into the power grid and are expected to offset up to 50% of the facility’s total energy requirements. Commissioned in October and operating since spring, Granite is already seeing favorable results.
“The project took a while to complete, and we had decisions to make,” says Sean Kilgrow, Granite’s director of renewable energy business development. “But we’ve been up for a few months and things are running great, with no problems at all.”
Hurdles To Clear
Finding panels for the project was difficult — and more expensive than panel prices now, Kilgrow says. Granite first began seeking out prices in 2009. According to Kilgrow, Granite’s suppliers had committed most, if not all, inventories to foreign projects, particularly in Germany.
Andrew Truitt, principal of Truitt Renewable Energy Consulting and senior energy consultant of Denver-based SRA International, says the demand and cost for solar panels peaked from 2004 to 2005, when costs were as much as $4.50 per watt. Today, the cost is closer to $1 to $1.50 per watt, he says.
Eventually, Granite found panels – 13,716 of them, to be exact. They ran about $2 a watt, Kilgrow says. About 10,000 of the panels were 85-watts, while the rest were 80-watt panels. This was problematic because panel mismatch can harm performance. Panels degrade at different rates, and if one panel goes out in a common series the entire series goes out.
“We had a very large investment in panels,” Kilgrow says. “Today, the cost of these panels is 50 percent of what they were when we purchased them. To protect our investment and keep the project pointed toward savings and success, we had to consider a power-management solution.”
Oliver Janssen, chief business officer of eIQ Energy, feels that “power management” only partially describes the performance of the company’s vBoost DC Parallel System.
“The eIQ energy solution was less expensive to install than comparable series architecture,” Janssen says. “It also provides long-term operational benefits by minimizing the effects of shading, soiling, panel mismatch and other issues that can reduce the electrical output of panels wired in series.”
Providing Balance
Janssen describes the eIQ system as a complete electrical balancing system.
“Modules within the photovoltaic array produce DC power, and an inverter converts it to AC power. In between is where eIQ, the electrical-balancing system, equalizes everything outside of the solar inverter.”
In series architecture, each solar module puts out different voltages. If a grid needs 350 volts, a series will add it up no matter where it comes from. With eIQ and in a parallel architecture, each solar module puts out 350 volts, Janssen says.
Panel mismatch, in particular, was a significant concern in Granite’s solar system. The output of the lowest panel greatly affects how the system produces power, according to Truitt. There can be huge power swings.
eIQ’s vBoost system solved the problem. It put intelligence for the system into the field and away from the inverter — monitoring every fourth panel in the array rather than only at the solar inverter. Measuring at the solar inverter means waiting for more panels to go bad to find areas of inefficiency, Janssen says. eIQ’s system includes data monitoring, which means the grid can be assessed from a desktop.
In a system of this size, the largest of any at an aggregate facility, it is more important to be able to shut down sections of the grid, Kilgrow says. This is especially true in California, where Pacific Gas & Electric (PG&E) rewards curtailment with a net-energy-metering program under which it rewards performance.
“Curtailment is rewarded by the state,” Kilgrow says. “Monitoring the field on every fourth panel allows us to pinpoint where we’re using the most energy, and where using energy has the most value. So we can curtail, realize benefits and keep our energy focused on generating business and making profits — and we get rewarded for it.”
Performance bonuses, efficiency and safety were major considerations when planning and financing the system, Kilgrow says. Granite is rewarded about 20 cents per kilowatt hour, for which PG&E writes them checks on a regular basis. This was attractive to financers of the costly project. They wanted guarantees that Granite would know what was going on and be able to communicate it to them, if necessary.
Finally, safety is a major benefit of Granite’s system. On a sunny day, for example, a company might see a peak in voltage, perhaps even lethal voltage. eIQ’s system identifies the location of the problem and allows managers to dispatch maintenance personnel to the right solar modules. Inverters alone can’t see specifically what’s causing problems, Janssen says.
Looking into the future, Truitt says lower module costs will at some point make optimizers less economical. Rather than invest in optimizers, one could simply buy more solar modules at a lesser cost. But users of eIQ’s electrical-balancing technology feel quite happy with its output and efficiency in any climate.
“We’re pleased using eIQ’s technology,” Kilgrow says. “The economic benefits of their parallel structure made this project more affordable for us to build renewable energy at our facilities here in California.” SPW
By: Timothy N. Troy/Contributing Editor
