By Steve Rizer
Could a pair of new developments in the photovoltaics (PV) industry make owners, architects, and others in the construction community more receptive of the technology when it comes time to plan their building projects?
In one recent development, Konarka’s Power Plastic solar panels have been integrated into Dri-Design’s metal rainscreen panels for building façade applications, the first commercial application of its kind and an integrated solution that Konarka believes represents a “great opportunity” for building owners seeking to meet their net-zero-energy goals. In the other development, the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) has released a new repeatable test protocol for solar arrays, an accomplishment that the lab believes can lead to more than a 12 percent improvement in system performance.
Konarka, which develops a lightweight, flexible organic solar film that converts light to electricity, said that the integration of its Power Plastic solar panels into Dri-Design’s metal rainscreen panels offers a recurring revenue stream for building owners, tax credits, and renewable energy credits, where applicable, along with “aesthetically pleasing” designs for architects.
Konarka’s solar films are suited for integration into various building materials, including glass, plastics, steel, composites, and fabrics. The company believes the technology offers “creative architects and product designers superior, widespread latitude with several color and transparency options across a wide range of sizes enabled by [the company’s] roll-to-roll continuous manufacturing process.”
The Dri-Design Wall Panel System is a dry joint, pressure-equalized rainscreen system used throughout the United States to clad commercial buildings of all sizes.
More Details about the Repeatable Test Protocol
The new, repeatable test protocol that NREL released simulates real shade conditions and can predict with much greater precision the effects of shade on a solar array, according to the lab. “The new test demonstrated that under heavy shading conditions the use of microinverters instead of typical string inverters can help mitigate the impacts of shade by improving system performance by more than 12 percent.”
“Photovoltaic (PV) Shading Testbed for Module-level Power Electronics” was co-authored by NREL senior engineers Chris Deline and Jenya Meydbray as well as Jason Forrest and Matt Donovan of PV Evolution Labs of Davis, Calif. DOE paid for the research.
Shade significantly impacts PV performance and is considered in PV system design, NREL stated. “The effects of shade can vary depending on the configuration of the PV modules, the extent of the shade, and the use of shade-mitigating power electronics in the system. The industry currently lacks representative, repeatable test procedures for evaluating the annual effect of shade on different PV systems equipped with different shade-mitigation devices.”
The new report details a repeatable test procedure for simulating shaded operation of a PV system and an analysis model for converting these measurements into annual performance forecasts.
Shade measurements from more than 60 residential installations provide the basis for the shading conditions employed during the test, which are analyzed for three typical shade scenarios – “light,” “moderate,” and “heavy” shading. The relative performance of a system using shade mitigation devices is compared against an identical system equipped with a reference string inverter for these three shade scenarios, providing an annual performance improvement score.
Combined with additional derates such as annual shade loss and inverter CEC efficiency, this annual shade improvement score can allow performance modeling software such as PV Watts http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/ and System Advisor Model https://sam.nrel.gov/ to better predict annual performance for PV systems that use shade-mitigating power electronics, NREL said. “It also allows an accurate comparison between different devices.”
An initial application of the test protocol was conducted by PV Evolution Labs, showing the shaded performance benefit of microinverters compared with a typical string inverter on identical 8-kilowatt solar arrays. The microinverter was found to increase system production by 3.7 percent under light shading, 7.8 percent under moderate shading, and 12.3 percent under heavy shading, relative to the reference string inverter case. Additional detail is provided in the report to allow duplication of the test method for different power electronics devices and test installations.
“Standard test methodologies using applicable test conditions should provide value to the PV community since products can be compared by a common metric and accurate information can be collected about devices’ annual performance benefit,” according to NREL.
“This is a major step in establishing new and realistic testing standards for PV power electronics,” said David Briggs of Enphase Energy, a microinverter manufacturer.
But what does NREL’s accomplishment mean for PV in the construction marketplace?
Chris Deline, an engineer in NREL’s PV center, told ConstructionPro Week (CPW) that the lab’s announcement about the repeatable test protocol highlights “some recent testing capability that we (and our partner PV Evolution Labs) have developed. The idea is to be able to put a better value on the performance improvements provided by certain types of PV power electronics such as microinverters and DC converters. As such, the test bed itself is not going to be providing big cost reductions, or enabling new technologies. It may provide a better understanding of how emerging technologies like microinverters will affect the performance of systems.”
In an email interview, Deline provided the following additional comments about the repeatable test protocol, Konarka’s accomplishment, and PV in the marketplace:
CPW: Regarding the PV Shading Testbed, is this a breakthrough that PV manufacturers can use and benefit from immediately, or is it the type of development that will take years to engender an improvement across the PV industry? How long will it take for this breakthrough to have a tangible effect on the industry and prices?
Deline: The new test bed is available immediately, so manufacturers can begin testing their products on it now.
CPW: What estimates, if any, can you provide about what exactly that tangible effect will be? In other words, by what amounts could manufacturing costs, prices, etc., eventually be reduced as a result of this breakthrough?
Deline: Tangible effects are hard to tell. My hope is that it will start bringing some of the marketing claims of these devices into better alignment with what will be achieved in reality.
CPW: What other breakthroughs in PV, if any, does NREL see occurring anytime soon, either within NREL or elsewhere? When may such breakthroughs occur?
Deline: Breakthroughs in PV may include module-integrated electronics where microinverters or power optimizers are embedded into the panel itself – no additional wiring or setup needed. One obvious question about this technology is the reliability of the electronics, and how frequently you’d have to go up to a roof to replace a panel because the inverter blew.
CPW: Konarka’s power plastic solar panels have been integrated into Dri-Design’s metal rainscreen panels for building facade applications, the first commercial application of its kind. Konarka sees this as a great opportunity to help building owners achieve their net-zero-energy goals. Does NREL agree? In your opinion, how significant is this development for solar films to better penetrate the green-building marketplace, either via rainscreens or other building materials such as glass, steel, and plastics?
Deline: [Building-integrated PV] applications are currently a niche market because of cost and efficiency considerations. If the economics pencil out on the panel side (cost competitive with the current ~$1/Watt of [crystalline silicon]), then there should be some additional advantages from reduced racking and installation cost, particularly if the panel is pre-integrated with the building component. In this particular instance, the product is targeting vertical wall space that would ordinarily not be covered by conventional PV panels. When they say that their market is ‘net zero’ buildings, that implies that the rooftop is already covered by conventional PV, and the builder needs to increase their power production through cladding of vertical wall space through additional PV. It’s a neat application that isn’t served by conventional PV at this point. I would expect it to be rather high cost right now, but organic PV is expected to come down in price and improve in efficiency as it reaches mass-scale production. For custom architectural projects like this, I think that it’s great to be able to get PV in many different forms.
CPW: Regarding PV in general, what is it going to take -- whether a change in policy, a change in culture within the construction community, or something else -- for PV to become more commonplace in new construction/retrofits of buildings?
Deline: In the next few years, it will be more cost effective to produce electricity from PV than to buy it from the utility (in certain places like the west -- it’s already there in Hawaii and almost there in California). However, for homeowners, cost is not actually the main driver -- it’s perceived cost and the hassle of dealing with quotes and contractors rather than just continuing to pay the utility bill and not worrying about it. In new construction, building codes and standards requiring ‘PV-ready’ construction and financial incentives to builders will continue to help adoption of PV. For retrofit, good outreach and advertising by the solar industry will help adoption to show customers how much money they could be saving. One issue is the higher up-front cost of PV. Even if it saves money in the long run, the higher up-front cost will give customers pause since you don’t usually think about your electric bill 10 years from now when you’re buying a house now. New financing schemes like PACE [Property Assessed Clean Energy] and solar leases help to amortize the up-front cost through regular payments over the years.
CPW: In making the case for PV, what is the best argument you can make for why owners, designers, and others in the construction community should embrace PV?
Deline: I think the best argument for PV is that it is a good financial investment. With the low prices of panels, the relatively large subsidies now, and the uncertain price of natural gas in the future, depending on the location, it’s a no-brainer, particularly if the homeowner can get financing so there’s little up-front cost. Of course, there are the additional benefits of using clean, non-polluting renewable energy.
CPW: Other comments?
Deline: I think that another emerging technology that could greatly increase the penetration of PV is pre-integrated roofing membrane solar panels, like for flat warehouse roofs. If you think about the amount of flat commercial roof space on Walmarts and Home Depots around the country, having an easy-to-install membrane roofing product with PV built-in could really see widespread adoption. Products like this are being developed by Carlisle, for instance (http://www1.eere.energy.gov/solar/sunshot/extreme_bos.html).
