The solar photovoltaic metric du jour is levelized cost of energy, commonly referred to by its initials, LCOE. The equation takes into account all elements of a system’s installed cost as well as its total lifetime cost ($) and divides that by its total lifetime energy output (kilowatt-hours). Manufacturing cost per watt, conversion efficiencies, and the like may be important, but they’re just not as meaningful individually as the total LCOE package in today’s discussion (and are indeed factored into the levelized cost calculation).
In a panel discussion on the economics of solar technologies at the cleantech branch of the recent TechConnect World 2010 conference in Anaheim, First Solar’s Kii Miller put it this way: “To focus on anything else [other than LCOE] would be a mistake.”
At the event, I spoke with two new companies, situated on opposite ends of the PV value chain, that believe they can have an impact on the cost numerator and, in the latter case, the energy denominator in the LCOE equation—SunPods and Sunsonix.
Noting the high cost of balance of systems components and installation—about 30-50% of the total system cost (representing the biggest chunk of the top half of the LCOE metric)—the founders of SunPods have examined how PV is delivered and see that there must be a better, cheaper, faster way to get to what they call “solar power on demand.”
Their solution, more of a business model innovation than a technical breakthrough, involves preassembling standardized PV systems and delivering the entire unit to the field, ready for hookup—not just prefitted racks or other elements of the system, but the whole self-leveling kit and self-ballasted kaboodle, pre-engineered, premanufactured, and pretested before it leaves the factory floor.
CEO Bill Kammerer told me a pair of SunPods SP-100 solar ground-mounted energy systems, each consisting of a dozen modules rated collectively at about 2.5KW (DC), can be unloaded from a flatbed truck and set up in a matter of a few hours at an installed cost of $4-5 per watt—and even less for a larger project. The company sees its market sweetspot ranging between a single 2.5KW system (the residential market beckons and the cost calculations look promising) and hundreds of units quickly installed to create a megawatt-scale power plant.
Compare this to conventional ground-mounted installations, which can take a week or two in many cases (and months for a larger plant) and have to be largely assembled at the work site, involving everything from grading the ground to pouring the concrete to posting and setting up the posts and racks to placing and wiring the modules before testing and activating the system--at a cost in the $5.50 to $7.50 per watt range.
The systems, with a steel frame sized at 10 × 20 ft and a >2-ft adjustable range, feature telescoping legs that can be moved up to 27 inches to place the array in the proper tilt position for a particular site (something done in the factory, according to Kammerer). Another benefit of the SunPods: You can throw one in the back of the truck and take it out to a potential customer for a demo.
The company “is technology agnostic with respect to modules and inverters,” he wrote in a subsequent email. “We have supply agreements in place with a number of manufacturers of these components,” including ET Solar, Suntech, SMA, and PV Powered. SunPods manages its entire supply chain, acting as the single source for the 10-year system warranty.
Kammerer said the goal is to make the SunPods “the Model T’s of solar,” with a “tightly controlled factory assembly process,” using “standard system designs,” and leveraging “volume purchase discounts for components.”
The company is moving forward, having just signed a lease for a new 22,000 sq ft facility in San Jose, which will combine its manufacturing and administrative offices into a single location, he said in his email. “Capacity at the new location is approximately 1MW per month, with the ability to expand to 2MW per month.”
The CEO told me at TechConnect that the cycle time required for assembling a SunPod is about eight hours, with room for improvement on that turnaround time.
He noted the company’s plans to “add another assembly facility in the Los Angeles region later this year, followed by additional assembly facilities in Arizona and New Jersey over the next 12 months.” Employing a distributed manufacturing strategy, the firm “needs to have assembly centers near to the demand sources.”
“New systems in development include a SunPod incorporating a single-axis tracker and a solar shade canopy product for parking lots and carports,” Kammerer added in his email.
In addition to residential, agricultural, commercial/industrial, and government/military market verticals, the company is working with Project Navigator on deploying the modular systems on landfills and other brownfield sites in urban areas.
Calling this approach a “novel solar project development scheme,” Project Navigator’s Robert Potter told me at the show that “any capped brownfield, landfill site has the potential for PV,” with the installed capacity of the installation—which could range up to several megawatts—dependent on the size and type of site.
While the idea of using PV to help power site remediation efforts at environmentally challenged locations—and send some juice to the local grid in the bargain—has great appeal, it’s the problem of contamination at the micro scale in solar cell manufacturing that concerns Sunsonix, another potential LCOE-impacting company I spoke with at the TechConnect event.
CEO/President Helmuth Treichel, a veteran of the semiconductor manufacturing wars, told me that the idea of his company’s cleaning chemistries “was born out of frustration.”
Noting the need for a solution to combating the deleterious effect of trace iron and other metallic contamination on the diode function of crystalline-silicon, wafer-based solar cells, he and his colleagues “couldn’t believe that no one else had thought of it.”
The Sunsonix team realized that there were serious technology gaps in the cleaning of production cells, ones that if addressed could improve efficiencies while lowering costs, and as a bonus, might even have a positive impact on one of the uncomfortable truths of PV power generation—cell and module performance degradation in the field.
Here’s the issue: the deionized water and acids used as process cleaning agents in the production of silicon PV cells—which are bulk devices with critical interfaces that don’t behave under the best of circumstances—are not effective in removing iron, nickel, chromium, copper, and other transition metallics. The result is the creation of midlevel traps, severely degrading the minority carrier lifetime (and thus lower open-circuit voltage performance), which has a direct correlation to weaker conversion efficiencies.
Team Sunsonix surmised that if one could get rid of those surface contaminants, the result would be a positive pop in efficiencies. To that end, the Milpitas, CA-based company has concocted a set of proprietary cleaning chemistries and processes, called SX-E, which are biocompatible and biodegradable, and can be used as a drop-in solution on today’s c-Si cell-processing lines, according to Treichel.
The ride has been fast and exciting, with the young company’s chemistries moving from the idea stage to proven technology in a hurry, starting with tests conducted at Georgia Tech UCEP in July 2009 that showed significant increases in open circuit voltage, and continuing with work at several cell manufacturers over the course of 2010.
The first production-level testing, contamination experiments conducted offline on thousands of individually analyzed multicrystalline wafers at Moser Baer PV’s fab, revealed that the addition of SX-E into the post-texturization cleaning baths outperformed the standard cleaning methods and led to a 0.2% to 0.3% absolute cell efficiency improvement.
The company head told me that when transferred to the manufacturing line, process test results were replicated, in both batch and inline toolsets, and required no change to the equipment set or process flow. And that 0.3% is just a start—there’s a fair amount of headroom for improvement.
That few tenths of actual efficiency gained translates into a projected $3 million to $5 million in operational cost savings for a 100MW cell line that might imbibe SX-E cocktails (which also work well in post-PSG cleans), according to Treichel. The volume of chemicals used would depend on the number of bath “turns” or changes specified in the fab, he explained, noting an example where, with the current cycle of turns, a one-step clean with a shot of 300ppm SX-E mixture would suffice.
Over the course of a year, a typical manufacturing line would need the equivalent of hundreds of liters of concentrated cleaning chemicals that would then be blended into the proper dilute mixture for processing, he explained.
Sunsonix makes it own chemicals now, although larger companies have approached them about licensing the recipes and producing the solutions themselves—the kind of corporate courting that the blushing firm has not been interested in so far, he told me. Treichel added that his outfit’s value also comes in the form of the deep expertise of its core team members, who work directly with customers on their specific process needs.
As for the aforementioned uncomfortable—and largely unspoken—truth about module degradation in the field (part of the denominator in the LCOE equation), Treichel pointed out that trace metals will diffuse over time in a cell, reducing the efficiency and output of installed c-Si-based PV. This efficiency decay amounts to about 1% per year, pushing the output down to 80% of the original power rating over the 20-year-plus lifetime of the device.
Sunsonix believes that by attacking the trace-metal contamination problem at its cellular source (and every single c-Si cell already in use is contaminated), this can have a direct impact on the problem of degradation. The company sees the use of its chemistries leading to as much as a 50% deceleration of efficiency decay.
By the team’s calculations, if one takes the projection of 35GW of installed PV panels worldwide in a few years, and factors in an absolute efficiency increase of 1% combined with that 50% decrease in cell decay, the energy savings extrapolate to a whopping 4.7GW—savings that go directly to the LCOE bottom line.
One day, these two upstart companies—SunPods and Sunsonix—may see their contributions to lowering solar power’s levelized cost of energy coexist in an elegant synergy, as decontaminated, degradation-resistant cells nestle in modules racked up in preassembled plug-and-play PV systems.
(Note: Sunsonix will be sharing booth space with its friends at PCT Systems during the colocated Semicon West/Intersolar North America shows in San Francisco--Moscone South Hall, Booth 711)