Exposure of Polymeric Glazing Materials Using NREL’s Ultra-Accelerated Weathering System (UAWs)

NREL’s Ultra-Accelerated Weathering System (UAWS) selectively reflects and concentrates natural sunlight ultraviolet irradiance below 475 nm onto exposed samples to provide accelerated weathering of materials while keeping samples within realistic temperature limits. This paper will explain the design and implementation of the UAWS which allow it to simulate the effect of years of weathering in weeks of exposure. Exposure chamber design and instrumentation will be discussed for both a prototype UAWS used to test glazing samples as well as a commercial version of UAWS. Candidate polymeric glazing materials have been subjected to accelerated exposure testing at a light intensity level of up to 50 UV suns for an equivalent outdoor exposure in Miami, FL exceeding 15 years. Samples include an impact modified acrylic, fiberglass, and polycarbonate having several thin UV-screening coatings. Concurrent exposure is carried out for identical sample sets at two different temperatures to allow thermal effects to be quantified along with resistance to UV.

Optimized Preparation of Moringa Oleifera Methyl Esters Using Sulfated Tin Oxide as Heterogenous Catalyst

Fatty acid methyl esters (biodiesel), prepared from transesterification of vegetable oils or animal fats, have gained great importance in substituting petroleum based diesel for combating environmental problems and higher diesel prices. Moringa oleifera fatty acids are among the newly investigated potentials for biodiesel production in recent years. In getting rid of soap formation and thus large waste washing water from biodiesel produced from homogenous catalysts, the use of heterogeneous catalysts is currently preferred due to easily separation and purification of the final products. In this study, biodiesel was produced from moringa oleifera oil using sulfated tin oxide enhanced with SiO2 (SO42−/SnO2−SiO2) as super acid solid catalyst. The experimental design was done using design of experiment (DoE), specifically, response surface methodology based on three-variable central composite design (CCD) with alpha (α) = 2. The reaction parameters in the optimization process were reaction temperature (60°C to 180°C), reaction period (1 to 3 hrs) and methanol to oil ratio (1:6 to 1:24 mol/mol). It was observed that the yield up to 84wt% of moringa oleifera methyl esters can be obtained with reaction conditions of 150°C temperature, 150 minutes reaction time and 1:19.5 methanol to oil ratio, while catalyst concentration and agitation speed are kept at 3wt% and 350 rpm respectively.

Concepts Developed for a Multi-Phased, Vertical Axis Wind Turbine System With an Adjustable Inlet Air Scoop and Exit Drag Curtain

A conceptual design is presented of a roof-top type, MULTI-PHASED VERTICAL AXIS WIND TURBINE SYSTEM with an ADJUSTABLE INLET AIR SCOOP and EXIT DRAG CURTAIN at a 100 Watt to 50 kWe commercial scale. The MULTI-PHASED VERTICAL AXIS WIND TURBINE (MVAWT) SYSTEM is cost effective in an environmentally friendly manner. It is especially useful in areas where it can benefit from the wind velocity increasing and streamlining effects that may occur around small hills, roof tops and tall buildings. The MVAWT system concentrates, collects and utilizes the available energy in the wind by way of a naturally yawed, downwind seeking, vertical axis orientated flow tube and integrated air turbine assembly with adjustable inlet air scoop and outlet drag sections mounted on the flow tube. The MVAWT system’s air turbine is a combination radial or mixed out-flow and reaction cross-flow type centrifugal fan design as mounted on the discharge end of the flow tube. This air turbine, being more of a radial instead of an axial flow or propeller type design, can potentially exceed the Betz limit of 59.26% energy recovery or effectiveness from the maximum energy available from the wind flowing through the inlet flow tube. A low pressure drop screen can be provided at the inlet and outlet to protect flying birds and mammals from being drawn into the integrated flow tube and air turbine assembly. Additionally, access to the rotating components for inspection and maintenance purposes is much safer, easier and less costly than with conventional propeller type wind turbine systems mounted on tall towers. No multiple staged wind turbine system as described herein has as yet been researched as to its technical feasibility and developed to the point of a prototype demonstration at a commercial size. Such parameters as overall performance, energy conversion efficiency, costs (installed, operating and maintenance), system reliability, public acceptance and environmental impacts have not yet been truly assessed. A Phase I - technical feasibility assessment and Phase II - prototype demonstration program for a nominal 10 kWe sized Multi-Phased Vertical Axis Wind Turbine system with an average power output in a 16 mph wind of as much as 2 kWe (kW-hr / hr) and as much as 10 kWe (kW-hr / hr) at a 28 mph wind velocity is suggested to provide this essential information to both the authors and the public at large.

Effect of High Temperatures and Heating Rates on High Strength Concrete for Use as Thermal Energy Storage

In recent years due to rising energy costs as well as an increased interest in the reduction of greenhouse gas emissions, there is great interest in developing alternative sources of energy. One of the most viable alternative energy resources is solar energy. Concentrating solar power (CSP) technologies have been identified as an option for meeting utility needs in the U.S. Southwest. Areas where CSP technologies can be improved are improved heat transfer fluid (HTF) and improved methods of thermal energy storage (TES). One viable option for TES storage media is concrete. The material costs of concrete can be very inexpensive and the costs/ kWhthermal, which is based on the operating temperature, are reported to be approximately $1. Researchers using concrete as a TES storage media have achieved maximum operating temperatures of 400°C. However, there are concerns for using concrete as the TES medium, and these concerns center on the effects and the limitations that the high temperatures may have on the concrete. As the concrete temperature increases, decomposition of the calcium hydroxide (CH) occurs at 500°C, and there is significant strength loss due to degeneration of the calcium silicate hydrates (C-S-H). Additionally concrete exposed to high temperatures has a propensity to spall explosively. This proposed paper examines the effect of heating rates on high performance concrete mixtures. Concrete mixtures with water to cementitious material ratios (w/cm) of 0.15 to 0.30 and compressive strengths of up to 180 MPa (26 ksi) were cast and subjected to heating rates of 3, 5, 7, and 9° C/min. These concrete mixtures are to be used in tests modules where molten salt is used as the heat transfer fluid. Molten salt becomes liquid at temperatures exceeding 220°C and therefore the concrete will be exposed to high initial temperatures and subsequently at controlled heating rates up to desired operating temperatures. Preliminary results consistently show that concrete mixtures without polypropylene fibres (PP) cannot resist temperatures beyond 500° C, regardless of the heating rate employed. These mixtures spall at higher temperatures when heated at a faster rate (7° C/min). Additionally, mixtures which incorporate PP fibres can withstand temperatures up to 600° C without spalling irrespective of the heating rate.

The Analysis and Application of Energy-Internet in the Low-Carbon Community

The energy-Internet is a new energy supply method based on urban compact and densely populated community in a low-carbon city. The principle is to connect small energy generation stations and combined heat and power system (CHP) based on distributed energy technology and renewable energy into a network in the urban district. In this way, the cooling, heating and electricity could all back each other up. Each building of the community could collect the energy and then put that energy into the energy-internet to supply the heating and power to buildings. The power in the energy-internet could also be used for charging electric vehicles. So the energy use in the urban community would be basically self-sufficient. The energy generation stations in the energy-internet could be solar power, wind power, biomass cogeneration (including refuse power generation), household fuel cell, low-grade heat in rivers, lakes, urban sewage and soil. In this way, large-scale renewable energy and unused energy could be fully used and applied in a compact and dense community. If the energy-internet is suitable designed, the equipment capacity, energy consumption and CO2 emission of the community could be greatly reduced, energy efficiency could be optimized and improved and the heat island effect could also be alleviated. This article explores three major problems of the construction of energy internet and their solutions: namely, the location and layout of the energy station, the environmental economic dispatch model of the energy internet with power dispatching as an example, the optimal path design of hot water pipe network combined with graph theory and genetic algorithms.

Thermal Computational Model to Analyze PV Modules: Preliminary Results

A computational model of a PV module was implemented to describe its thermal behaviour considering the geographical conditions of the Yucatan Peninsula, Mexico. In order to analyze the effects of non uniform illumination on the thermal profiles of a PV module, a reflecting surface was added adjacent to a PV module edge. A finite difference formulation was used to represents the thermal patterns of each PV describing the thermal conditions of each particular solar cell within the PV module. The mathematical model and the preliminary results obtained for two time instants are presented using real meteorological data to reflect the effect of the wind patterns.

Comparison of Different Time Series Methods for Short-Term Forecasting of Wind Power Production

Reliable short-term predictions of the wind power production are critical for both wind farm operations and power system management, where the time scales can vary in the order of several seconds, minutes, hours and days. This comprehensive study mainly aims to quantitatively evaluate and compare the performances of different Box & Jenkins models and backpropagation (BP) neural networks in forecasting the wind power production one-hour ahead. The data employed is the hourly power outputs of an N.E.G. Micon 900-kilowatt wind turbine, which is installed to the east of Valley City, North Dakota. For each type of Box & Jenkins models tested, the model parameters are estimated to determine the corresponding optimal models. For BP network models, different input layer sizes, hidden layer sizes, and learning rates are examined. The evaluation metrics are mean absolute error and root mean squared error. Besides, the persistence model is also employed for purpose of comparison. The results show that in general both best performing Box & Jenkins and BP models can provide better forecasts than the persistence model, while the difference between the Box & Jenkins and BP models is actually insignificant.

Performance Optimization and Parametric Analysis of a Class of Solar-Driven Heat Engines

A class of solar-driven heat engines is modeled as a combined system consisting of a solar collector and a unified heat engine, in which muti-irreversibilities including not only the finite rate heat transfer and the internal irreversibility, but also radiation-convection heat loss from the solar collector to the ambience are taken into account. The maximum overall efficiency of the system, the optimal operating temperature of the solar collector, the optimal temperatures of the working fluid and the optimal ratio of heat transfer areas are calculated by using numerical calculation method. The influences of radiation-convection heat loss of the collector and internal irreversibility on the cyclic performances of the solar-driven heat engine system are revealed. The results obtained in the present paper are more general than those in literature and the performance characteristics of several solar-driven heat engines such as Carnot, Brayton, Braysson and so on can be directly derived from them.

Implementation of Solar Thermal Driven Absorption Cooling in the Southeast

A 35,000 ft2 [3,251 m2] Creative Arts instruction building is being constructed on the campus of Haywood Community College in Clyde, NC (∼25 miles [40 km] west of Asheville). The building’s HVAC system consists of a solar absorption chiller, two parallel back-up electric chillers, and radiant floor heating with condensing boiler back-up. Hot water is to be heated by 117 solar thermal panels with thermal energy storage in a 12,000 gallon [45,000 liters] insulated tank and service to both the absorption chiller and the radiant under-floor heating system. Peak cooling loads and unfavorable solar conditions are to be handled by parallel electric chillers, operated in sequence to achieve maximum performance. Emergency radiant under-floor heating hot water back-up is to be handled by gas-fired condensing boilers in the event of unavailable solar heated hot water. This paper will examine the extensive modeling process required of the system as performed in EnergyPlus, how preliminary modeling results influenced the control and design strategy, the annual behavior of the system and the importance of controllability.

Installation and Operation of Southern Nevada Water Authority High Concentration Amonix Multi-Junction System

The Southern Nevada Water Authority contracted with Amonix, Inc. in 2008 to procure 220 kWdc of their latest generation multi-junction cell High Concentration Photovoltaic system. This paper describes the installation of the six HCPV systems including the design layout of the field, installation of the foundations, the PV modules, and tracking control systems. In addition, the basic operation and features of the Amonix HCPV system are discussed, along with data showing the performance of each system since the start of operation.