Video Scanning Hartmann Optical Testing of State-of-the-Art Parabolic Trough Concentrators

Significant progress has been made recently in solar parabolic trough technology development and deployment. Part of this success is due to the changing world energy scenario and the recognition that viable renewable energy technologies can play a role in supplying world energy needs. Part is also due to ongoing collaborative efforts by industry and the Department of Energy’s (DOE) Concentrating Solar Power Program (CSP) to enhance the state of the technology in terms of both cost and performance. Currently, there are two trough concentrator projects which the DOE CSP program is supporting. One company, Solargenix, is developing a design to be used in a 64MW plant outside of Boulder City, Nevada. This design is based on the original LUZ LS-2 trough concentrators employed at the Solar Electric Generating Systems (SEGS) plants in Southern California. Another company, Industrial Solar Technology (IST), is working on a scale-up of their design used historically for process heat applications. Very different from the LS-2 approach, this design is still in the research and development stages. One way in which the DOE CSP parabolic trough program assists industry is by providing optical testing and qualification of their concentrator designs. This paper describes the Video Scanning Hartmann Optical Test System (VSHOT) used to optically test both of these designs. The paper also presents the results of tests performed in the past year and what impact the testing has had on the developmental direction of each design.

H2 Generation by Two-Step Water Splitting With CeO2-MOx Using Concentrated Solar Thermal Energy

CeO2-MOx (M = Mn, Fe, Ni, Cu) reactive ceramics, having high melting points and high conductivities of O2−, were synthesized with the combustion method from their nitrates for solar hydrogen production. The prepared CeO2-MOx samples were solid solutions between CeO2 and MOx with the fluorite structure through XRD. Two-step water splitting reactions with CeO2-MOx reactive ceramics proceeded at 1573–1773K for the O2 releasing step and at 1273K for the H2 generation step by irradiation of infrared imaging furnace as a solar simulator. The amounts of O2 evolved in the O2 releasing reaction with CeO2-MOx and CeO2 systems increased with the increase of the reaction temperature. The amounts of H2 evolved in the H2 generation reaction with CeO2-MOx systems except for M = Cu were more than that of CeO2 system after the O2 releasing reaction at the temperatures of 1673 and 1773K. The largest amount of H2 was generated with CeO2-NiO after the O2 releasing reaction at 1573, 1673 and 1773K. The O2 releasing reaction at 1673K and H2 generation reaction at 1273K with CeO2-Fe2O3 were repeated four times with the evolving of O2 (1.3cm3/g-sample) and H2 (2.3cm3/g-sample) gases, respectively. The possibility of solar hydrogen production with CeO2-MOx (M = Mn, Fe, Ni) reactive ceramics system by using concentrated solar thermal energy was suggested.

Interrelations of Hourly and Daily Global Illuminance

It has been found that the values of ratio of hourly global illuminance to daily global illuminance, rvt, are very close to the corresponding values for global solar radiation, rt, examined from the measured data of six IDMP [1] (International Day light Measurement Programme) locations. This has been further confirmed by examining the values for rvt and rt as calculated from TMY2 [2] (Typical Metrological Year) data base for primary locations. Based on this, it has been proposed that the correlations available in literature to predict rt can be employed to predict rvt. Adequacy of the correlation due to Collares-Pereira and Rabl [3] available for rt has been examined to predict rvt as obtained from TMY2 data base for the 56 primary locations. It has been found that the values of rvt obtained from measured illuminance data of six locations have been predicted within a rms difference of 2.71% and within a rms difference of 4.3% for the 56 primary locations of TMY2 data when the correlation due to Collares-Pereira and Rabl for rt has been employed.

Numerical Study of Optimal Building Scales With Low Cooling Load in Both Hot and Mild Climatic Regions

Natural ventilation is one of the primary strategies for buildings in hot and mild climatic regions to reduce building cooling energy requirement. This paper uses a building energy simulation program and a computational fluid dynamics program to investigate the influence of building scales on building cooling energy consumption with and without natural ventilation. The study examines the energy performance of buildings with different L/W and H/W ratios in both Miami, FL and Los Angeles, CA. The simulation results show the varying trends of natural ventilation potential with increased building scale ratio of L/W and H/W. The comparison of the predicted energy consumptions for twenty buildings discloses the most energy-efficient building scales for rectangular-shape buildings in both hot and mild climates with and without natural ventilation. The study indicates that natural ventilation is more effective in mild climates than in hot climates, which may save cooling energy by 50% and vent fan energy by 70%. The paper analyzes the most suitable seasons for natural ventilation in Miami and Los Angeles. Further simulations indicate that extra cooling benefits associated with more natural ventilation cannot compensate additional heat gains through larger windows.

Research on the Energy Saving Performance of the Enthalpy Recovery Ventilator in Chinese Residential Buildings

In order to fulfill the indoor comfort and health requirements, people need to supply a large amount of outdoor fresh air into the indoor environment. In the past, because of the poor airtight performance of the residential buildings in China, there is usually no mechanical ventilator installed, almost all of the outdoor air infiltrates from the leaks through the windows and doors. Recently, in order to improve the energy saving performance, the windows and doors of the residential buildings become more and more airtight so that the outdoor air can’t infiltrate into the rooms easily, but it results in the worse and worse indoor air quality. People need supply enough outdoor fresh air into the rooms without increasing the energy consumption greatly. The installation of the enthalpy recovery ventilator (ERV) is an effective method. It can transfer heat and moisture from the exhaust air into the outdoor fresh air to save energy. Nowadays, ERV has been widely used in the commercial and industry buildings, and started in the residential buildings in China. But ERV is not always energy saving in anywhere and anytime. Its energy saving performance depends on a lot of factors, such as the outdoor environmental condition, the enthalpy effectiveness of the enthalpy recovery medium, the Coefficient of Performance (COP) of the air condition system and so on. Based on the weather data, this paper calculates the hourly energy saving performance of ERV for residential buildings that are hypothetically located in five Chinese representative cities of five different climate zones in summer. It gives the definition of the cooling ventilation season and studies the influence factors related to the energy saving performance of ERV.

Analysis of Demand Side Management Measures for Residential Buildings

As part of a utility program to explore implementation of demand charges and time of use utility rates for residential buildings, impact of commonly used energy efficiency measures on the reduction of electricity demand in residential homes are explored in this paper. The study presented in the paper focus on homes located in the Denver-Boulder area. Detailed energy audit and simulation analyses are conducted to obtain detailed data relevant to energy performance of 13 homes. Simplified analysis method is outlined to estimate the energy use of residential homes as well as electrical peak demand. Moreover, general guidelines are provided to effectively reduce peak demand for homes.

Overview of Solar Air Drying Systems in India and His Vision of Future Developments

Solar Air Drying is one of the oldest method of food preservation. For several thousand years people have been preserving grapes, herbs, Potato’s, corn, milk, fruits, vegetables, spices, meat and fish by drying. Until canning was developed at the end of the 18th century, drying was virtually the only method of food preservation. It is still the most widely used method. Solar Drying is an excellent way to preserve food and solar food dryers are an appropriate food preservation technology for a sustainable world. This technology makes it possible to dehydrate and preserve food professionally without compromising on quality, color, texture, enzymes, vitamins, taste and nutritional values of foods in the process. Food scientists have found that by reducing the moisture content of food to between 10 and 20%, bacteria, yeast, mold and enzymes are all prevented from spoiling it. India is blessed with an abundance of sunlight, water and biomass. Vigorous efforts during the past two decades are now bearing fruit as people in all walks of life are more aware of the benefits of renewable energy, especially solar energy in villages and in urban or semi-urban centers of India. Industries that can benefit from application of solar energy to heat air are Food, Textiles, Dairies, Pharma and Chemical. This paper reviews the present scenario of Solar Air Dryer and strategies for future developments in India.

Influence Factors of Energy Consumption in All Cold Outdoor Air Systems

Nowadays the safety of the air conditioning systems is paid more attention to. All cold outdoor air systems due to their particular advantages such as credible safety, better indoor air quality, saving more building space and being in favor of the energy conservation in some given conditions [1] are discussed in this paper. The composing of all cold outdoor air system is outlined and the mathematical models of energy consumption evaluation are presented. With an actual example by using the method of equivalent weight full load operation time, the influence factors to the annual primary energy consumptions in all cold outdoor air systems, such as: the dew point temperature, the COP (Coefficient of Performance) of chiller, the equivalent weight full load operation time of chiller and the efficiency of enthalpy exchanger etc. are compared and analyzed. And the optimal application modes for energy conservation of all cold outdoor air systems are proposed. These can be good references for the application of all cold outdoor air systems.

CFD-Based Parametric Analysis on the Performance of Personalized Partition Air Distribution Systems

The partition air distribution systems evaluated in this study allow occupants to control the system mode (on/off) and the supply air velocity and direction with similar flexibility as occupants in automobiles. To find optimal specifications for the partition air distribution systems that are able to achieve comfortable micro-environment, a CFD modeling tool was used to simulate the airflow and thermal performance of the partition air distribution systems in a typical office space. By analyzing the distribution characteristics of indoor air temperature, air velocity and thermal comfort index, the study assessed the performance of the partition air distribution systems with different operating parameters. The simulation results were analyzed and evaluated to assess both occupant’s thermal comfort and system energy consumption. The study shows that space cooling energy can be reduced while maintaining acceptable indoor thermal comfort level using a partition air distribution system with a higher supply air temperature.

Implementing Solar Energy in the Colorado Production Home Market

A standardized deployment of solar electric systems in the Colorado production home market is crucial to the success of the renewable portfolio standard recently adopted by Colorado voters. This research uses the Built Green® program as a context for investigating energy conservation measures (ECMs), viable within the production home market, for their efficacy in curtailing new home annual energy consumption and peak electrical demand loads. The research examines the cost effectiveness and impact of residential solar systems compared to the energy conservation measures. Colorado is a state with good solar resources and considerable production-scale residential development. However, most production homes built in the state today are not highly energy efficient. It is generally believed that improvements to energy efficiency — more insulation, better windows, more efficient appliances — are more cost-effective than solar production systems given current costs. In other words, most production homes in Colorado are not ready to don a solar home system (SHS). The analysis uses extensive energy simulation to determine energy savings of selected energy-saving home features relative to the baseline Building America Benchmark for Denver, CO. This optimization process seeks to identify the least-cost combinations of improvements, assuming present day component costs, with the greatest annual energy savings, with the ultimate goal of implementing solar energy in the Colorado production home market. The results of the analysis suggest that optimal characteristics of production home, designed to minimize total costs, are readily achievable in today’s market. Moreover, when these optimal ECMs are implemented, the marginal cost of a SHS is found to be less than additional energy efficiency. With further energy efficiency improvements, site-based solar electric systems can compete economically given current state and federal incentive programs. The results also indicate that a solar system oriented west of due south can offer significant reductions in peak demand relative to both the household and utility load profiles.