Jeff Muhs

A review on inductive charging for electric vehicles

The scarce supply of fossil fuel in the mere future has driven the development of electric vehicles (EV) worldwide. Plug-in connectors have been commonly proposed for EV charging, however, these systems have disadvantages such as safety, esthete, and operation in snow. Therefore, a new method to inductively charge the vehicle without any physical contact has been proposed. This paper presents a state of the art literature review on the recent advancements of Inductive Power Transfer (IPT) technology used in EV charging. A possible future technology to solve the inherent range anxiety problem is also presented using roadway electrification and in-motion power transfer concepts.

Design of Symmetric Voltage Cancellation Control for LCL converters in Inductive Power Transfer Systems

This paper presents a new design strategy for Symmetric Voltage Cancellation (SVC) Control used in LCL converters for Inductive Power Transfer (IPT) Systems. It was found that the operating mode that eliminated diode reverse recovery losses in the H-bridge had particularly low losses. An analytical technique is used to calculate the operating modes. Three common control schemes used in LCL converters were computed and normalized graphs are produced to aid designers in making engineering tradeoffs between more efficient switching schemes, total harmonic distortion (THD) and the overall cost of the converter. For a typical LCL converter example, total losses in the H-bridge can be reduced by a factor of 11 by restricting operation to a mode with no diode reverse recovery loss.

Design and Performance of a Solar Photobioreactor Utilizing Spatial Light Dilution

A photobioreactor with an optical system that spatially dilutes solar photosynthetic active radiation has been designed, built, and tested at the Utah State University Biofuels Center. This photobioreactor could be used to produce microalgal biomass for a number of purposes, such as feedstock for an energy conversion process, or high-value products, such as pharmaceuticals and nutraceuticals. In addition, the reactor could be used to perform services such as removing nitrates, phosphates, and other contaminants from waste water, as well as scrubbing toxic gases and carbon dioxide from flue gas. Preliminary tests were performed that compared growth and productivity kinetics of this reactor with that of a control reactor without spatial light-dilution. Tests indicated higher specific growth rates and higher areal and volumetric yields compared with the control reactor. The maximum specific growth rate, volumetric yield, and areal yield were 0.21 day ―1 , 0.059 gm l ―1 day ―1 , and 15 gm m ―2 day ―1 , respectively. Over 10 days of sequential-batch operation, the prototype photobioreactor converted direct-normal solar energy to energy stored in biomass at an average efficiency of 1 %. The areal productivity, as mass per aperture per time, was three times higher than that of the control reactor, indicating the photobioreactor design investigated holds promise.

PERFORMANCE OF NEW HYBRID SOLAR LIGHTING LUMINAIRE DESIGN

We report on the performance of a new hybrid luminaire designed to blend light from a fiber optic solar source with electric fluorescent lamps. The luminaire design studied involves a commercially-available fluorescent luminaire that had been modified to include optical elements for efficiently dispersing a fiber optic solar light source. Quantitative measurements of the hybrid luminaire’s optical efficiency and spatial intensity distribution/deviations are discussed. The effects of static differences and dynamic fluctuations in spatial intensity distribution are qualitatively discussed and potential design improvements examined.Copyright

Fiber-optic holography employing multiple beam fringe stabilization and object/reference beam intensity variability

The use of fiber optics in the field of optical holography is discussed with emphasis on the design of systems used to overcome several inherent shortcomings associated with fiber-optic holographic systems. Specifically, random environmentally induced optical phase changes within the fiber are minimized by employing a Michelson interferometer in conjunction with a closed loop feedback system. Furthermore, by using several passive single-mode couplers, complete object illumination via several illumination fibers is observed. Finally, by implementing a Mach-Zehnder interferometric technique, control of the object and reference beam intensity ratios in a fiber-optic holographic system can be accomplished. The resulting schemes are very stable and highly versatile systems suitable for remote holographic interferometric sensing and other applications where conventional holography techniques are impractical. Experimental results on fringe visibility, fringe stability, and the stabilization of object/reference beam intensity ratios are also given along with a composite summary of the overall system constraints associated with fiber-optic holographic systems.

Optical Design of an Infrared Non-Imaging Device for a Full-Spectrum Solar Energy System

A full-spectrum solar energy system is being designed by a research team lead by Oak Ridge National Laboratory and the University of Nevada, Reno. [1,2] The benchmark collector/receiver and prototype thermophotovoltaic (TPV) array have been built [3J, so the work performed here is to match the two systems together for optimal performance. It is shown that a hollow, rectangular-shaped non-imaging (NI) device only 23 cm long can effectively distribute the IR flux incident on the TPV array mounted behind the secondary mirror. Results of the ray-tracing analysis of the different systems tested are presented.

Economic Analysis of a Vertical Sheet Algal Photobioreactor for Biodiesel Production

The combination of a 100% increase in diesel fuel prices since 2002 and a new photobioreactor technology has renewed interest in producing biodiesel, a direct petroleum diesel fuel substitute, from microalgae. A new photobioreactor technology in which the microalgae are grown on vertically suspended membranes promises to increase algal productivity per acre ten-fold compared to microalgae ponds, and 400-fold compared to soybeans. This paper describes the general photobioreactor concept and assesses the economic viability of such technology given the current crude oil prospects. The majority of the data necessary for assessment are obtained from published articles, with experimental results providing the remaining necessary information. Analysis results indicate that the photobioreactor would need to be constructed and operate on the order of dollars per square foot per year.Copyright

Initial Results From an Experimental Hybrid Solar Lighting System in a Commercial Building and Overview of Related Value Propositions

This paper describes preliminary results from research on a new hybrid solar lighting (HSL) system being developed to reduce electric lighting in commercial office buildings. A physical description of HSL system components along with preliminary results from an experimental system deployed in a commercial building in Knoxville, TN are provided. Results from a systems-level, chromaticity model are compared with experimental data. A total lumen distribution efficiency of over 50% was recorded for the initial prototype having optical fibers an average of 6 m (19.5 ft) in length. The total electrical power displacement of the 1 m2 HSL proof-of-concept prototype is estimated to be between 522–2350 watts per 1000 W/m2 of incident solar radiation on the collector depending on the type of electric lights being used in conjunction with the solar lighting system. By adding the reductions in heat gain associated with reduced electric lamp use and predicted performance improvements achieved by a system redesign, the electrical power displaced in a commercial prototype could rise to between 702–3160 W (peak)/m2 of collected sunlight not including any additional electrical power that can be generated using the otherwise wasted IR energy. The color temperature of the distributed sunlight emerging from the optical fibers is approximately 5100°K and the chromaticity values in uniform color space (u′v′) are approximately (.2010, .4977). These values match well with modeled results and will vary slightly depending on the day, time, atmospheric conditions, and system configuration. The paper concludes with a discussion of new value propositions that HSL provides architects, energy providers, building owners, and occupants and briefly outlines anticipated disadvantages.Copyright

Solar Energy, Collected, Concentrated, Transported, and Distributed as Light With No Energy Conversion Via a Hybrid Solar Lighting System

Hybrid solar lighting (HSL) is a technology in which sunlight is collected and distributed via optical fibers into the interior of buildings. Analogous to hybrid electric vehicles that use both batteries and internal combustion engines to power cars, hybrid lighting employs roof-mounted collectors to concentrate sunlight into flexible optical fibers and carry it inside buildings to “hybrid” light fixtures that also contain electric lamps. As the two light sources work in tandem, control systems keep lighting levels constant by dimming the electric lights when sunlight is bright, and turning them up as the sky darkens with weather conditions or nightfall. Data indicate that on a bright, sunny day the power consumption for lighting can be reduced by 50% or more. Today, lighting in U.S. residential and commercial buildings consumes close to 5 quadrillion BTUs of primary energy and one-fifth of all electricity. In commercial buildings, one-quarter of all energy demand is for lighting. With a forecasted doubling of commercial floor space by the year 2020 comes an urgent and growing need to find more efficient ways of lighting our nation’s buildings. Typically, less than 25 percent of the electrical energy consumed for lighting actually produces light; the rest generates heat, which increases the need for air-conditioning. Unlike conventional electric lamps, the sunlight from HSL systems produces virtually no waste heat. A nationwide field trial program is under way to provide system performance data and user-feedback essential for the successful commercialization of HSL. Field trial installations include San Diego State University, San Diego, CA; Pacific Northwest National Laboratory, Richland, WA; Sacramento Municipal Utility District, Sacramento, CA; Wal-Mart, McKinney, TX; Aveda Corp., Minneapolis, MN; Staples, Long Island, NY; Braden’s Furniture, Knoxville, TN; Multipurpose Research Facility, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN; University of Nevada-Las Vegas, Las Vegas, NV; Hybrid Lighting Laboratory, ORNL, Oak Ridge, TN. This paper describes the field trial program and summarizes the results to date from the field trial installations.

First-generation hybrid solar lighting collector system development and operating experience

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.