Solar-Driven Sorption Chillers for Residential Space Cooling: A Review of Recent Developments and Possible Applications in Canada

Energy use for space cooling has increased by 156% from 1990 to 2010 in the Canadian residential sector. In many parts of the country, the increasing use of electrically driven air-conditioners has begun to shift the peak load on the electricity grid from the coldest days of winter to the hottest days of summer. Many of Canada’s major electric utilities providers rely on fossil fuels to generate the additional capacity needed to meet the peak demand, resulting in significant greenhouse gas emissions. Solar-driven sorption chillers remain one of the possible solutions for shaving the peak loads experienced by the electricity grid. This paper presents a review of the recent developments in the research of adsorption and absorption chillers, as well as a comparison of the two technologies based on the latest published experimental results found in the literature. Adsorption chillers continue to evolve in their design, including the use of new consolidated and composite adsorbents, the integration of coated adsorbers into internal heat exchangers, and newly developed advanced cycles for heat and mass recovery. While the physical design of adsorption chillers continues to be advanced, the development of absorption chillers for solar cooling applications has largely been focused on optimizing the system as a whole through improved control strategies and the implementation of newly developed high performance solar collectors. Finally, the paper aims to assess the current state of development of solar-driven sorption chillers to provide insight into their applicability in the Canadian residential sector, as well as the remaining challenges facing this technology.

From Passive to Active Pitch Regulation of Wind Turbines: Optimization Method With Numerical Validation

An optimization method that changes the control strategy of the Horizontal Axis Wind Turbine (HAWT) from passive- to active-pitch has been developed. The method aims to keep the rated power constant by adjusting the blade pitch angle while matching the rotor and the drive torques. The method is applied to an optimized wind turbine model. Further, numerical simulations were performed to validate the developed method and for further investigations of the flow behavior over the blades.

Energy Consumption Prediction of University Buildings in China and Strategies for Energy Efficiency Management

In 2007, Chinese Ministry of Education (MOE) and Ministry of Housing & Urban-Rural Development (MOHURD) carried out the Campus Resource Conservation Actions, in order to take full use of resources and to improve the energy efficiency. However, due to the large amounts of universities, the total energy consumption and the energy efficiency situation have no objective statistics. Taking modeling the energy consumption of university buildings as the starting point, this paper analyzes the characteristics of university buildings in China. Then, we do the prediction, trend and potential analysis of the total energy consumption in 2020. In addition, four strategies for energy efficiency management are carried out, which might be helpful for all the university managers and related departments.

Investigating the Potential of Urban Land Uses to Support Sustainable Energy Principles Using a Spatial Analysis Model

The underpinning elements of sustainable communities are centered on economic security, renewable energy resources, reliable infrastructure, and ecological protection. The geomorphology of urban areas is altered due to human activity leading to change in land use characteristics and resources availability. Research has shown that global population has increased drastically over the last three decades resulting in depleted efficiency of regional resources. Because of this, obtaining sustainable energy platforms is a world-wide concern. In evaluating the ability of urban communities to support sustainable elements, both spatial and temporal influences must be considered. As a result a spatial analysis model will be used to assess the geomorphological and land use aspects of urban watersheds to support sustainable communities’ platform. These data will provide insight in essential components in need of environmental restoration that contribute to future renewable resources which can then be applied on a global scale.

Deployment of Fuel Cell Electric Buses in Transit Agencies: Hydrogen Fueling Infrastructure Scenarios

For transit agencies looking to implement Zero Emission Vehicles (ZEV), Fuel Cell Electric Buses (FCEBs) represent an opportunity because of the similar range and refueling times compared to conventional buses, but with improved fuel economy. To assure an environmentally sensitive hydrogen infrastructure that can respond to the wide range of needs and limitations of transit agencies, a systematic evaluation of options is essential. This paper illustrates the systematic evaluation of different hydrogen infrastructure scenarios for a transit agency. The Orange County Transportation Authority (OCTA) in California was selected for the study. Three different hydrogen infrastructure configurations are evaluated and compared to the existing paradigm of compressed natural gas buses and diesel buses. One additional scenario is analyzed in order to compare feasibility and environmental benefits of FCEBs with Plug-in Electric Buses. Each scenario represents (1) a specific mix and percentage of contribution from the various hydrogen generation technologies (e.g., on-site electrolysis, central SMR, and on-site SMR), (2) defined paths to obtain the corresponding feedstock for each generation process (e.g., biogas, natural gas, renewable energies), (3) detailed hydrogen distribution system (e.g., mix of gaseous/liquid truck delivery), and (4) the spatial allocation of the generation location and fueling locations (e.g., on-site / off-site refueling station) while also accounting for constraints specific to the OCTA bases. This systematic evaluation provides Well-to-Wheel (WTW) impacts of energy and water consumption, greenhouse gases and criteria pollutant emissions of the processes and infrastructure required to deploy FCEBs and Plug-in Electric Buses at OCTA. In addition, this evaluation includes a detailed analysis of the space requirements and operations modifications that may be necessary, but yet feasible, for the placement of such infrastructure.

Design of a Mobile Probe to Predict Convection Heat Transfer on Building Integrated Photovoltaic (BIPV) at University of Technology Sydney (UTS)

In the absence of a simple technique to predict convection heat transfer on building integrated photovoltaic (BIPV) surfaces, a mobile probe with two thermocouples was designed. Thermal boundary layers on vertical flat surfaces of a photovoltaic (PV) and a metallic plate were traversed. The plate consisted of twelve heaters where heat flux and surface temperature were controlled and measured. Uniform heat flux condition was developed on the heaters to closely simulate non-uniform temperature distribution on vertical PV modules. The two thermocouples on the probe measured local air temperature and contact temperature with the wall surface. Experimental results were presented in the forms of local Nusselt numbers versus Rayleigh numbers “Nu=a * (Ra)b”, and surface temperature versus dimensionless height [Ts -T∞= c*(z/h)d]. The constant values for “a”, “b”, “c” and “d” were determined from the best curve-fitting to the power-law relation. The convection heat transfer predictions from the empirical correlations were found to be in consistent with those predictions made by a number of correlations published in the open literature. A simple technique is then proposed to employ two experimental data from the probe to refine empirical correlations as the operational conditions change. A flexible technique to update correlations is of prime significance requirement in thermal design and operation of BIPV modules. The work is in progress to further extend the correlation to predict the combined radiation and convection on inclined PVs and channels.

Exergetic Efficiency: A Detailed Reaction Mechanism Analysis of Hydrogen Combustion With Singlet Oxygen

In previous work the authors have demonstrated that when hydrogen is combusted in stoichiometric proportions at 1 atm and 1200 K, and singlet oxygen comprises 0–20% of the oxidizer, an optimal range of exergetic efficiency exists. The maximum exergetic efficiency occurs at approximately 10%. Over this range, roughly 60% of the total exergy destruction occurs prior to ignition. This is a significant result because it suggests that the exergetic efficiency of combustion might be improved at a fundamental level by chemical means, thereby inherently increasing the efficiency of fuel use for a desired energy application. The objective of the study presented in this paper is to analyze the reaction mechanisms for combustion with varying percentages of singlet oxygen, to determine which reaction pathways most influence the observed trends in exergy destruction and exergetic efficiency. This was accomplished by performing both sensitivity and rate-of-production analyses of the hydrogen-oxygen combustion mechanism. The results of the analysis show that the presence of singlet oxygen governs the rate of production of hydroxyl and other key radicals. These key radicals directly affect the phenomenological processes associated with chemical induction and thermal induction during ignition. Therefore, the observed optimum exergetic efficiency correlates to the quantity of singlet oxygen in the inlet charge that minimizes exergy destruction by fostering chemical reactions due to radical formation to a greater extent than thermal heat release. The results of this analysis are noteworthy and provide new insight regarding how the exergetic efficiency of combustion may be optimized by introducing singlet oxygen, thereby altering the reaction pathways to enhance energy conversion in a fundamental way that could have important implications for improved fuel use.

Response Surface Based Optimization of Solar Collector Integrated With an Ammonia-Water Combined Power/Cooling Cycle Supported by Exergy Analysis

Finding optimal operating conditions of solar-based power and cooling systems is always a challenge. Performance of these systems is highly dependent on several important parameters, which not only impact the long-term efficiency but also its technical and economic feasibility. This paper studies the operation/configuration problem of an ammonia-water power and cooling cycle using an exergetic analysis. Thermodynamic performance of the combined cycle was addressed by using analysis of variance and multiple linear regression analysis. Modeling was done in Matlab®, using Refprop 9.0 to calculate the thermodynamic properties of the ammonia-water mixture. Convergence issues were observed on the thermodynamic properties estimation carried out by Refprop when the stream had high ammonia mass fraction. To solve this issue an averaging algorithm was implemented online to estimate such properties using pure ammonia data and high, but stable, ammonia concentration data. After this implementation, small differences between current and reference model were seen. Optimum operating conditions were obtained using response surface technique. The response variable used was the ratio between exergetic efficiency and exergy destruction. Results showed that the response variable is mainly influenced by the ammonia concentration, pressure ratio, turbine efficiency and temperature gradient in the heat exchanger. Finally integration of the power/cooling cycle with a solar field was performed using two types of concentrated solar collectors: Linear Fresnel Collector (LFC) and Parabolic Trough Collector (PTC). The analysis showed that LFC technology can be a viable alternative for small scale applications combined with power/cooling systems.

Assessment of Photovoltaic Surface Texturing on Transmittance Effects and Glint/Glare Impacts

Standard glass and polymer covers on photovoltaic modules can partially reflect the sunlight causing glint and glare. Glint and glare from large photovoltaic installations can be significant and have the potential to create hazards for motorists, air-traffic controllers and pilots flying near installations. In this work, the reflectance, surface roughness and reflected solar beam spread were measured from various photovoltaic modules acquired from seven different manufacturers. The surface texturing of the PV modules varied from smooth to roughly textured. Correlations between the measured surface texturing (roughness parameters) and beam spread (subtended angle) were determined. These correlations were then used to assess surface texturing effects on transmittance and ocular impacts of glare from photovoltaic module covers. The results can be used to drive the designs for photovoltaic surface texturing to improve transmittance and minimize glint/glare.

Numerical Simulation Study for the Performance of a Large Solar Hot Water System With Horizontal Storage Tank

A large solar hot water system can be utilized to provide driving energy for heating system, heat-driven cooling system, as well as to provide hot water. This research addresses the effects of the storage tank design parameters on the performance of a large-scale solar hot water system with a horizontal storage tank. Most literatures only considered the stratification performance of the thermal storage tank itself instead of considering the overall system performance. Also, there is lack of experimental research data available for the design purpose. Therefore, this study employs a numerical simulation technique to study the design parameters effect of a horizontal thermal storage tank on the performance of a large-scale solar hot water system. In this study, the ANSYS-CFX program is employed to calculate the flow and temperature distributions inside horizontal thermal storage tank. Then the inlets and outlets of the tank are combined with the TRNSYS program to simulate the entire system performance under the weather of three representative cities of Taiwan, (Taipei, Taichung and, Kaohsiung). The results of the present study indicate that the vertical stratification baffles in the tank have important effects on system performance improvement. Quantitative increase of solar fraction of the total load is obtained. The comparison with the system with vertical storage tank is provided. The results of the present study can provide important reference for the large solar hot water system design in improving system efficiency.