Research is underway at Oak Ridge National Laboratory (ORNL) that could lead to entirely new, highly energy-efficient ways of lighting buildings using the power of sunlight. In addition to providing light, the hybrid lighting system will convert sunlight to electricity much more efficiently than conventional solar technologies using thermo-photovoltaic cells. In commercial buildings today, lighting consumes more electric energy than any other building end-use. It accounts for more than a third of all electricity consumed for commercial use in the United States. Typically, less than 25% of that energy actually produces light; the rest generates heat that increases the need for air-conditioning. ORNL is developing a system to reduce the energy required for lighting and the air-conditioning loads associated with it, while generating power for other uses.
The system uses roof-mounted concentrators to collect and separate the visible and infrared portions of sunlight. The visible portion is distributed through large-diameter optical fibers to hybrid luminaires. (Hybrid luminaires are lighting fixtures that contain both electric lamps and fiber optics for direct sunlight distribution.) When sunlight is plentiful, the fiber optics in the luminaries, provide all or most of the light needed in an area. Unlike conventional electric lamps, they produce little heat. During times of little or no sunlight, sensor-controlled electric lamps will operate to maintain the
desired illumination level.
A second use of the hybrid lighting collector system is to provide sunlight for enhanced practical photosynthesis carbon dioxide mitigation. In this project the hybrid lighting collector system is
being used to provide sunlight to a lab-scale photobioreactor for growing algae that is being used for CO2 mitigation. The end goal of this project is to provide a photobioreactor that can be used to mitigate CO2 in fossil fuel fire power plants.
This paper will discuss the development and operating
experience to date of two hybrid lighting solar collectors installed at ORNL and at Ohio University. The first hybrid lighting collector system was tested at ORNL and then installed at Ohio University in June of 2002. A second collector of the same design was installed at ORNL in September of 2002. The Ohio University collector system has been running continually since its installation while the ORNL unit has been operated in a research mode on most sunny days. They have operated with very little human interaction and this paper will summarize the development, operating experience, collection efficiency, as well as providing information on additional data being collected as part of the system operation.
Under a program sponsored by the Department of Energy, the Oak Ridge complex is developing a `Portal-of-the-Future', or `smart portal.' This is a security portal for vehicular traffic which is intended to quickly detect explosives, hidden passengers, etc. It uses several technologies, including microwaves, weigh-in-motion, digital image processing, and electroacoustic wavelet-based heartbeat detection. A novel component of particular interest is the Enclosed Space Detection System (ESDS), which detects the presence of persons hiding in a vehicle. The system operates by detecting the presence of a human ballistocardiographic signature. Each time the heart beats, it generates a small but measurable shock wave that propagates through the body. The wave, whose graph is called a ballistocardiogram, is the mechanical analog of the electrocardiograms, which is routinely used for medical diagnosis. The wave is, in turn, coupled to any surface or object with which the body is in contact. If the body is located in an enclosed space, this will result in a measurable deflection of the surface of the enclosure. Independent testing has shown ESDS to be highly reliable. The technologies used in the smart portal operate in real time and allow vehicles to be checked through the portal in much less time than would be required for human inspection. Although not originally developed for commercial transportation, the smart portal has the potential to solve several transportation problems. It could relieve congestion at international highway border crossings by reducing the time required to inspect each vehicle while increasing the level of security. It can reduce highway congestion at the entrance of secure facilities such as prisons. Also, it could provide security at intermodal transfer points, such as airport parking lots and car ferry terminals.
Optical fiber sensor elements were embedded in ceramic matrix composite (CMC) specimens fabricated at the Oak Ridge National Laboratory using a rapid chemical vapor infiltration (CVI) process. The silica and sapphire optical fiber sensors were placed between adjacent layers of interwoven NicalonR fibers during the stacking of a preform. This preform was then coated with pyrolytic carbon, used as an interface layer, and then densified with additional silicon carbide through CVI. This paper discusses the survivability of both the silica and sapphire optical fiber sensor elements, and suggests the possibility of using embedded optical fiber sensor elements inside high temperature composites for both fabrication monitoring and subsequent in-service lifetime monitoring at high temperatures.
Optical time-domain reflectometry (OTDR) is a simple and rugged technique for measuring quantities such as strain that affect the propagation of light in an optical fiber. For engineering applications of OTDR, it is important to know the repeatable limits of its performance. The authors constructed an OTDR-based, submillimeter resolution, strain measurement system from off-the-shelf components. The system repeatably resolves changes in time of flight to within +/- 2 ps. Using a 1 m, single-mode fiber as a gauge and observing the time of flight between Fresnel reflections, we observed a repeatable sensitivity of 400 microstrains. Using the same fiber to connect the legs of a 3 dB directional coupler to form a loop, we observed a repeatable sensitivity of 200 microstrains. Realizable changes to the system that should improve the repeatable sensitivity to 20 microstrains or less are discussed.
A novel technique for measuring several physical parameters suing a transparent, silicone- rubber optical fiber is described. A discussion of the physical and optical characteristics of the fiber is provided along with preliminary experimental results on various present and future sensor applications. These applications include fiber-optic sensors for detecting and measuring temperature, humidity/moisture, force, and static and dynamic pressure.
Over the past decade, the demand from both government and private industry for small, lightweight, vehicle weight-in-motion (WIM) systems has grown substantially. During the 1980s, several techniques for weighing vehicles in motion were developed that include piezoelectric cables, capacitive mats, and hydraulic and bending-plate load cells. These different systems have advantages and disadvantages that trade off between accuracy, physical size, and system complexity. The smaller portable systems demonstrate medium to poor accuracy and repeatability while the larger more accurate systems are nonportable. A small, lightweight, and portable WIM system based on a fiber-optic pressure transducer has been developed by Oak Ridge National Laboratory (ORNL) to meet the demands of government and industry. The algorithm for extracting vehicle weight from the time-dependent sensor response is developed and presented in this report, along with data collected by the system for several classes of vehicles. These results show that the ORNL fiber-optic WIM system is a viable alternative to other commercial systems that are currently available.
Exp erimental results on a portable, low speed fiber-optic weigh-in-motion system are described that demonstrate the applicability of fiber-optic-based sensors in transportation, defense, and law enforcement applications where accurate weight determination of moving vehicles is necessary. Results are given on the systems' dynamic range (0.1—30 metric tons), velocity range (up to 5 km/h), accuracy error (0.5—3.0%), and repeatability. Also included in the paper is a discussion of the sources of error associated with low speed weigh-in-motion systems and methods of minimizing these errors for practical deployment.
A proposed multiplexed fiber-optic sensor system capable of analyzing a composite material during its curing cycle and over its service lifetime is presented. The sensor is composed of two independent sensing schemes that will ultimately be multiplexed onto a specialized singlemode/multimode optical fiber. The first sensing scheme is a fiber-optic viscosity and temperature sensor used for composite cure analyses. This sensor is based on (1) the laser-induced viscositydependent fluorescence phenomena observed in epoxy-based composite materials and (2) the temperature-dependent decay-time fluorescence phenomena observed in thermographic phosphors. The second sensor is based on a low-finesse, single-mode fiber-optic Fabry-Perot interferometer and is used as a strain/vibration sensor for lifetime nondestructive evaluations on composites. Exp erimental results have determined that these sensor concepts are feasible alternatives to cureanalysis monitors and conventional strain-analysis techniques.