Solar power windows: Connecting scientific advances to market signals

Recent materials advances have enabled researchers to envision and develop highly efficient, partially transparent photovoltaic (PV) prototypes, exposing a potentially large and untapped market for solar energy: building integrated (BI) solar powered windows. In this perspective, we assess the case for market deployment of BIPV windows, specifically intended for commercial U.S. high-rise buildings. Research and development on solar powered windows has been predicated on the hypothesis that sunlight-to-electrical power conversion efficiency (PCE) and device cost per unit area are the key figures of merit that might drive market adoption. Here we investigate the market landscape and desirability for solar powered windows by identifying and evaluating the customer needs for the commercial high-rise building window market. In the course of this assessment, we performed 150 interviews with experts across the value chain for commercial windows. We found that the market forces are complicated by a misalignment of incentives between the end users of BIPV windows and the key decision makers for building projects that could incorporate this technology. Our assessment leads us to frame new figures of merit for BIPV windows that address the underlying needs of prospective customers as well as technical metrics for energy generation. We finally discuss one possible direction for BIPV window technology in which photovoltaics are integrated with switchable windows. Here, the integrated PV converts visible and infrared light transmission into useable electricity enabling standalone, self-powered active windows that can potentially address market needs for smart windows, thereby enabling a pathway for BIPV window deployment

The CLAS12 Backward Angle Neutron Detector (BAND)

The Backward Angle Neutron Detector (BAND) of CLAS12 detects neutrons emitted at backward angles of $155^\circ$ to $175^\circ$, with momenta between $200$ and $600$ MeV/c. It is positioned 3 meters upstream of the target, consists of $18$ rows and $5$ layers of $7.2$ cm by $7.2$ cm scintillator bars, and read out on both ends by PMTs to measure time and energy deposition in the scintillator layers. Between the target and BAND there is a 2 cm thick lead wall followed by a 2 cm veto layer to suppress gammas and reject charged particles. This paper discusses the component-selection tests and the detector assembly. Timing calibrations (including offsets and time-walk) were performed using a novel pulsed-laser calibration system, resulting in time resolutions better than $250$ ps (150 ps) for energy depositions above 2 MeVee (5 MeVee). Cosmic rays and a variety of radioactive sources were used to calibration the energy response of the detector. Scintillator bar attenuation lengths were measured. The time resolution results in a neutron momentum reconstruction resolution, $\delta p/p < 1.5$\% for neutron momentum $200\le p\le 600$ MeV/c. Final performance of the BAND with CLAS12 is shown, including electron-neutral particle timing spectra and a discussion of the off-time neutral contamination as a function of energy deposition threshold.Comment: 17 pages, 25 figures, 3 tables. Accepted for publication in NIM-