So, you’ve heard this before, but solar power today is really on the verge of going mainstream. How do we know that, this time, the odds are better than ever? By following the money.

First, homeowners are buying and installing rooftop systems at an increasingly rapid clip, even as they cut back on other home improvements. And, second, a combination of utility, manufacturer and government investment is targeting new technology that takes large numbers of residential systems as a given, seeking to turn their customers’ solar panels into generating assets.

Overall, 2009 was a strong year for the solar industry, with revenues—including those for concentrating solar installations and utility-scale photovoltaic (PV) projects—growing 38 percent to reach $4 billion, according to the Solar Energy Industry Association (SEIA). But it was particularly good for residential installers. The capacity of these rooftop PV installations reached 156 MW in 2009, a 100 percent increase over the corresponding figure for 2008, according to SEIA numbers.

The addition of all these small-scale, distributed generation systems poses challenges for utilities, especially given the intermittent nature of PV electricity production. But, with communications capabilities advancing almost as quickly as PV adoption, grid managers are beginning to see residential systems as potential aids in their efforts to improve grid stability.

Two important efforts are now underway to develop the hardware and software needed to unite customers’ systems with grid-stability goals. Both of these programs are focused on the inverter, the vital link through which PV-generated direct current (DC) is converted to alternating current (AC) usable by both homeowners and utilities. Those leading these efforts see the need for greater integration of distributed resources into larger grid operations.

“One of the principles of the smart grid is engaging the customer and their equipment,” said Brian Seal, a senior project manager at the Electric Power Research Institute (EPRI), a utility-funded research group. He’s heading up EPRI’s participation in a public/private effort to develop standardized messaging protocols that will allow utilities to gain maximum advantage from growing networks of small generation sources.

“Already, there are stability issues and voltage-regulation issues that could be mitigated with two-way communication,” he said, noting the importance of standards in an environment where multiple systems and manufacturers are entering the marketplace. “When you get to smaller systems, with very diverse brands, it becomes an unmanageable mess from a communications perspective.”

Running in parallel with the work to enhance communications over a network of inverters is a three-year project to improve the operation of individual inverters at the point of installation. Called the Solar Energy Grid Integration Systems (SEGIS) Initiative, the program is bringing together manufacturers and government and utility researchers, all under the guidance of the Sandia National Laboratory in Albuquerque, N.M. It has just entered its third and final phase of work developing new inverter hardware.

In the first stage, SEGIS researchers challenged a pool of manufacturers to develop new-product concepts, with associated market feasibility information. The resulting proposals were narrowed down to five options, some serving different applications, for prototype development, an effort completed this summer. These prototypes now are in a pilot production phase, aiming for commercialization by next summer.

Among the capabilities product developers are pursuing is the ability to ramp PV power supplies up and down, rather than turning them on or off like a light switch, to help prevent stability-threatening voltage issues. Manufacturers also are looking at using inverters to provide volt-ampere reactive control and at ways to provide some degree of ride-through during utility-side disturbances.

Of course, the kind of leap forward such functionality offers will require more than just an even swap-out of equipment. For example, the Underwriters Laboratories’ UL 1547 standard, which covers PV system inverters and other interconnection devices, needs rethinking. This guideline, developed to protect lineworkers from islanding conditions, calls for automatically disconnecting PV operations at any sign of line trouble, even in those situations in which the added electricity could improve the grid’s stability. A revised version, addressing new capabilities, is now in the draft review stage as UL 1547-8.

These developments also could mean a bit of work for electrical contractors involved in PV installation, or those considering expanding into this growing market. Getting up to speed on new equipment and standards will require time and a willingness to be flexible as this evolving technology expands from its current early-adopter market presence into the mainstream.

As is probably obvious, these communications-intensive developments all are a piece of a larger smart grid vision. The clear dividing line—the meter—that once separated utilities from their customers is becoming just another data point in network that is reaching out to—and into—customer operations.

“I think the smart grid, in general, is asking the question of how much more efficient and reliable can our electric power system be if we stop cutting the customer out of the picture,” Seal said.


ROSS is a freelance writer located in Brewster, Mass. He can be reached at chuck@chuck-ross.com.