American Solar (United States)

NREL and its project partners built and commercialized the novel Solar Automated Permitting Processing Plus (SolarAPP+) software platform that delivers instant residential rooftop solar permits. The tool provides installers with a standard portal for entering permit information for residential solar systems across all Authorities Having Jurisdiction (AHJs) using SolarAPP+, thereby providing a streamlined plan review form, transparency into permitting timelines, and required specifications. The project has proven to reduce permitting timelines from as many as 20 business days to zero, delivering solar projects faster in the four participating AHJs using the platform. Streamlining permitting timelines, all else equal, results in consumers installing their systems and reducing their electricity bills faster. The continued expansion of SolarAPP+ features and adoption nationwide will expand the benefits of the SolarAPP+ beyond the current user base.

Used throughout the United States and many other countries, the National Electrical Code (NEC) is the world’s most detailed set of electrical codes pertaining to photovoltaic (PV) systems. PV and the NEC presents a straightforward explanation of the NEC in everyday language. This new edition is based on the 2020 NEC, which will be used widely until 2026, with most of the interpretations and material staying true long after. This book interprets the distinct differences between previous versions of the NEC and the 2020 NEC and clarifies how these code changes relate specifically to PV installations. Written by two of the leading authorities and educators in the field, this book will be a vital resource for solar professionals, as well as anyone preparing for a solar certification exam.

This article discusses low temperature energy recovery systems that are being installed on three Federal buildings in the Washington, DC, area. The three projects discussed use simple systems that deliver low cost heat to buildings in innovative ways. Each uses a source of low temperature heating available from within the building to reduce fossil fuel use. One system recovers heat from the ventilation return air to heat water for the hydronic reheat loop serving variable air volume boxes in the building. The second system recovers heat from an attic space below a plywood roof deck covered with asphalt shingles to heat a domestic hot water loop for a barracks. The third system recovers heat from the solar re-roofing of a building to supply heated air for swimming pool heating and for a heating, ventilating, and air conditioning system. The purpose of this article is to demonstrate the versatility of these low temperature heat recovery systems.

In order to relax the mechanical constraints of processing thin crystalline Si wafers into highly efficient solar cells, we propose a process sequence, where a significant part of the process is done on module level. The device structure is an interdigitated-back-contact cell with an amorphous silicon back surface field. The record cell reaches an independently confirmed efficiency of 18.4%. Although the device deserves further optimization, the result shows the compatibility of processing on glass with efficiencies exceeding 18%, which opens the door to a high-efficiency solar cell process where the potentially thin wafer is attached to a foreign carrier during the full processing sequence.

Metal oxides are reviewed as catalysts to convert H2O and CO2 to fuels using solar energy. For photochemical conversion, TiO2 has been found to be the most stable and useful oxide material, but it is currently limited by its large bandgap and a mismatch between its conduction band and the redox couples for water splitting and CO2 reduction. A theoretical framework has been utilized to understand the basic thermodynamics and energetics in photochemical energy conversion systems. This is applied to model systems comprised of Ag2O and AgCl to examine why the former reacts thermochemically in air, while the latter reacts photochemically. For thermochemical conversion, zinc-, ceria-, and ferrite-based redox cycles are examined and examples of high-temperature solar reactors driven by concentrated solar radiation are presented. For CO2 splitting, theoretical solar-to-fuel energy conversion efficiencies can be up to 26.8% for photochemical systems, and can exceed 30% for thermochemical systems, provided that sen...

Because of its superior long-wavelength response and stability against light-induced degradation, hydrogenated nanocrystalline silicon (nc-Si:H) has become a promising candidate to replace hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) in multijunction thin-film silicon solar cells. In this paper, we report on the development of our proprietary high-frequency (HF) glow discharge deposition technology for nc-Si:H solar cells that has resulted in high-quality nc-Si:H materials with good spatial uniformity. We studied the HF-deposited nc-Si:H material using various analytical techniques. We fabricated a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells that are deposited on textured Ag/ZnO back reflectors. Large-area cells were fabricated and encapsulated using our proprietary lightweight flexible encapsulants. National Renewable Energy Laboratory (NREL) has confirmed (1) initial aperture-area efficiency of 11.8% on an 807.8-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> encapsulated cell and (2) stable aperture-area efficiency of 11.2% on a 400-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> encapsulated cell.

We present an approach to estimating the light-trapping of thin film silicon solar cells by comparing the measured quantum efficiency spectrum and the theoretical absorptance spectrum based on ideal diffractive light scattering. The ideal diffractive absorptance enhancement is about 50 in silicon-based cells. We have surveyed published results for many nanocrystalline silicon cells; the largest empirical enhancement is about 25. We discuss the physical mechanisms leading to the reduced quantum efficiencies.

To ensure the longevity and reliability of solar modules, the PV industry has adopted a series of accelerated aging tests. Among these, the damp heat test performed at 85°C, 85% relative humidity for 1000 hrs provides the most information on the degradation of encapsulant and backsheet materials. The purpose of this work is to define the proper accelerated test conditions that represent 25 years of real field life exposure of these polymers.