Integrated solar lighting for pedestrian crosswalk visibility.

PDFTech Reporthttp://ntl.bts.gov/lib/60000/60500/60599/FDOT-BDV31-977-62-rpt.pdfTask Order # 977-62Master Agreement Order # BDV31CrosswalksSolar energyPedestrian safetyLighting equipmentStreet lightingFloridaFlorida. Dept. of TransportationScheffe, JonathanUniversity of FloridaFlorida. Dept. of TransportationUS Transportation CollectionThis report is written for the Florida Department of Transportation (FDOT) to aid in their assessment of the viability of solar-driven lighting of pedestrian crosswalks or other traffic bearing areas to enhance safety. The goal of the solarized crosswalk is to provide power for lighting and/or illumination using integrated lighting to enhance pavement markings and visibility; it should also provide service during power failures and in remote areas without nearby electrical utilities. Other potential traffic bearing areas include parking lots, shared-use/multi-use trails, motor vehicle traffic ways, etc. The FDOT is primarily interested in mature technologies that have the potential to meet these demands.The primary technology of interest for FDOT is a device that may be integrated directly into the surface of the crosswalk or pavement; this device would include the solar energy harvesting device (e.g. photovoltaic module), the light emitting devices and energy storage. Primary concerns of FDOT include the friction on the surface, the load bearing capacity and the cost. If the viability of utilizing solar panel technologies that are directly integrated into the crosswalk or pavement is low, FDOT is also interested in using solar power at a site external to the crosswalk or pavement to illuminate it from above or with in-pavement lighting. FDOT is ultimately interested in commercially available technologies but would also be interested to learn of technologies being developed at the lab scale.While the use of photovoltaic modules is ubiquitous for remote power generation applications, the results of this analysis indicate that only a handful of companies are currently developing photovoltaic (PV) modules for direct integration in roadways. These technologies are motivated by using the extensive area available on roadways as power generating potential. Some, such as Solar Roadways\uc2\uae provide the ability to integrate sensors and lighting into roadways surfaces for a multitude of potential applications related to so-called \ue2\u20ac\u153smart roads\ue2\u20ac?. Nevertheless this technology faces several potential hurdles, as will be discussed, and also are not designed with energy storage in mind; one pre-requisite of the FDOT. Furthermore, this analysis indicates that there are no technologies available today that are commercially available; all companies developing solar roadway technologies are still in there development and demonstration phase. The major concerns that arise when considering these technologies are 1) their mechanical durability and 2) their optical durability, meaning how transparent do the surfaces stay over time after deposition of dust and other debris and scratching of the surface from interaction of vehicles and small particulates. The former is often addressed by the companies but the latter is not.One alternative possibility that this analysis has uncovered is the use of photo-luminescent stones that may be directly integrated into roadway surfaces. This passive approach has been realized by a Dutch company Heijmans, for lighting bike paths during the nighttime. Because this is a completely passive approach, there are concerns about the duration of lighting, as well as the structural and chemical stability of the materials over long periods of time. Nevertheless, this approach should be considered a very cost effective solution.Beyond these two possibilities we discuss the feasibility of providing decentralized power for lighting by integrating PV modules off the side of the road or integrating thermo-electric modules directly into the roadway (to meet the original objectives of FDOT). The latter has some distinct advantages compared to integrating PV modules into roadway surfaces because they do not need to see direct exposure to the sunlight. The total power generation is substantially less but if the goal is only to provide lighting then thermoelectric power generation may be a suitable alternative