Solar energy : utilization in building operations

In the face of increasing concern over global warming and climate change, interest in the utilizzation of solar energy for building operations is rapidly growing. In this entry, the importance of using renewable energy in building operations is first introduced. This is followed by a general overview on the energy from the sun and the methods to utilize solar energy. Possible applications of solar energy in building operations are then discussed, which include the use of solar energy in the forms of daylighting, hot water heating, space heating and cooling, and building-integrated photovoltaics.

Thermal fatigue analysis of solar panel structure for micro-satellite applications

Thermal fatigue analysis based on 2D finite difference and 3D finite element methods is carried out to study the performance of solar panel structure during micro-satellite life time. Solar panel primary structure consists of honeycomb structure and composite laminates. The 2D finite difference (I-DEAS) model yields predictions of the temperature profile during one orbit. Then, 3D finite element analysis (ANSYS) is applied to predict thermal fatigue damage of solar panel structure. Meshing the whole structure with 2D multi-layer shell elements with sandwich option is not efficient, as it misses thermal response of the honeycomb structure. So we applied a mixed approach between 3D solid and 2D shell elements to model the solar panel structure without the sandwich option.

DESIGN, ANALYSIS, AND RELIABILTY OF SOLAR PANEL ROTATION MECHANISM FOR MICROSATELLITE

Solar array rotation mechanism provides a hinged joint between the solar panel and satellite body, smooth rotation of the solar array into deployed position and its fixation in this position. After unlocking of solar panel (while in orbit), rotation bracket turns towards ready-to-work position under the action of driving spring. During deployment, once reached the required operating angle (defined by power subsystem engineer), the rotation bracket collides with the fixed bracket that is mounted on body of the satellite, to stop rotation. Due to the effect of collision force that may alter the rotation mechanism function, design of centrifugal brake is essential. At stoppage moment micro-switches activate final position sensor and a stopper locks the rotation bracket. Design of spring and centrifugal brake components, static finite element stress analysis of primary structure body of rotation mechanism at stoppage moment have been obtained. Last, reliability analysis of rotation mechanism is evaluated. The benefit of this study is to aid in the design of rotation mechanism that can be used in micro-satellite applications.

Combined solar and pellet heating systems for single-family houses : How to achieve decreased electricity usage, increased system efficiency and increased solar gains

In Sweden, there are about 0.5 million single-family houses that are heated by electricity alone, and rising electricity costs force the conversion to other heating sources such as heat pumps and wood pellet heating systems. Pellet heating systems for single-family houses are currently a strongly growing market. Future lack of wood fuels is possible even in Sweden, and combining wood pellet heating with solar heating will help to save the bio-fuel resources. The objectives of this thesis are to investigate how the electrically heated single-family houses can be converted to pellet and solar heating systems, and how the annual efficiency and solar gains can be increased in such systems. The possible reduction of CO-emissions by combining pellet heating with solar heating has also been investigated. Systems with pellet stoves (both with and without a water jacket), pellet boilers and solar heating have been simulated. Different system concepts have been compared in order to investigate the most promising solutions. Modifications in system design and control strategies have been carried out in order to increase the system efficiency and the solar gains. Possibilities for increasing the solar gains have been limited to investigation of DHW-units for hot water production and the use of hot water for heating of dishwashers and washing machines via a heat exchanger instead of electricity (heat-fed appliances). Computer models of pellet stoves, boilers, DHW-units and heat-fed appliances have been developed and the parameters for the models have been identified from measurements on real components. The conformity between the models and the measurements has been checked. The systems with wood pellet stoves have been simulated in three different multi-zone buildings, simulated in detail with heat distribution through door openings between the zones. For the other simulations, either a single-zone house model or a load file has been used. Simulations were carried out for Stockholm, Sweden, but for the simulations with heat-fed machines also for Miami, USA. The foremost result of this thesis is the increased understanding of the dynamic operation of combined pellet and solar heating systems for single-family houses. The results show that electricity savings and annual system efficiency is strongly affected by the system design and the control strategy. Large reductions in pellet consumption are possible by combining pellet boilers with solar heating (a reduction larger than the solar gains if the system is properly designed). In addition, large reductions in carbon monoxide emissions are possible. To achieve these reductions it is required that the hot water production and the connection of the radiator circuit is moved to a well insulated, solar heated buffer store so that the boiler can be turned off during the periods when the solar collectors cover the heating demand. The amount of electricity replaced using systems with pellet stoves is very dependant on the house plan, the system design, if internal doors are open or closed and the comfort requirements. Proper system design and control strategies are crucial to obtain high electricity savings and high comfort with pellet stove systems. The investigated technologies for increasing the solar gains (DHW-units and heat-fed appliances) significantly increase the solar gains, but for the heat-fed appliances the market introduction is difficult due to the limited financial savings and the need for a new heat distribution system. The applications closest to market introduction could be for communal laundries and for use in sunny climates where the dominating part of the heat can be covered by solar heating. The DHW-unit is economical but competes with the internal finned-tube heat exchanger which is the totally dominating technology for hot water preparation in solar combisystems for single-family houses.

SOLAR PANEL MODELING ON SUITABLE ROOFS AT COLBY

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Solar Panel Modeling on Suitable Roofs at Colby

With the recent construction of Colby Green and the current plans for the construction of several new buildings, the total area for future development on campus has declined. The goal of this study was to illustrate existing campus development and to determine where future growth could occur. GIS was used in determining the different soil systems on campus, the current use of the land, and the boundaries of the Colby property. The project shows what potential obstacles the college will have in attempting to expand the campus and proposes where the best options are for construction.

Explicit Expressions for Solar Panel Equivalent Circuit Parameters Based on Analytical Formulation and the Lambert W-Function

Due to the high dependence of photovoltaic energy efficiency on environmental conditions (temperature, irradiation...), it is quite important to perform some analysis focusing on the characteristics of photovoltaic devices in order to optimize energy production, even for small-scale users. The use of equivalent circuits is the preferred option to analyze solar cells/panels performance. However, the aforementioned small-scale users rarely have the equipment or expertise to perform large testing/calculation campaigns, the only information available for them being the manufacturer datasheet. The solution to this problem is the development of new and simple methods to define equivalent circuits able to reproduce the behavior of the panel for any working condition, from a very small amount of information. In the present work a direct and completely explicit method to extract solar cell parameters from the manufacturer datasheet is presented and tested. This method is based on analytical formulation which includes the use of the Lambert W-function to turn the series resistor equation explicit. The presented method is used to analyze commercial solar panel performance (i.e., the current-voltage–I-V–curve) at different levels of irradiation and temperature. The analysis performed is based only on the information included in the manufacturer’s datasheet.

Explicit expressions for solar panel equivalent circuit parameters based on analytical formulation and the Lambert W - Function

Due to the high dependence of photovoltaic energy efficiency on environmental conditions (temperature, irradiation...), it is quite important to perform some analysis focusing on the characteristics of photovoltaic devices in order to optimize energy production, even for small-scale users. The use of equivalent circuits is the preferred option to analyze solar cells/panels performance. However, the aforementioned small-scale users rarely have the equipment or expertise to perform large testing/calculation campaigns, the only information available for them being the manufacturer datasheet. The solution to this problem is the development of new and simple methods to define equivalent circuits able to reproduce the behavior of the panel for any working condition, from a very small amount of information. In the present work a direct and completely explicit method to extract solar cell parameters from the manufacturer datasheet is presented and tested. This method is based on analytical formulation which includes the use of the Lambert W-function to turn the series resistor equation explicit. The presented method is used to analyze the performance (i.e., the I - V curve) of a commercial solar panel at different levels of irradiation and temperature. The analysis performed is based only on the information included in the manufacturer's datasheet.

Nonlinear dynamics of a satellite with deployable solar panel arrays

The multibody dynamics of a satellite in circular orbit, modeled as a central body with two hinge-connected deployable solar panel arrays, is investigated. Typically, the solar panel arrays are deployed in orbit using preloaded torsional springs at the hinges in a near symmetrical accordion manner, to minimize the shock loads at the hinges. There are five degrees of freedom of the interconnected rigid bodies, composed of coupled attitude motions (pitch, yaw and roll) of the central body plus relative rotations of the solar panel arrays. The dynamical equations of motion of the satellite system are derived using Kane's equations. These are then used to investigate the dynamic behavior of the system during solar panel deployment via the 7-8th-order Runge-Kutta integration algorithms and results are compared with approximate analytical solutions. Chaotic attitude motions of the completely deployed satellite in circular orbit under the influence of the gravity-gradient torques are subsequently investigated analytically using Melnikov's method and confirmed via numerical integration. The Hamiltonian equations in terms of Deprit's variables are used to facilitate the analysis. (C) 2003 Published by Elsevier Ltd.

Increased health care utilization and increased antiretroviral use in HIV-infected individuals with mental health disorders

Objectives The aims of the study were to describe the prevalence and associations of mental health disorder (MHD) among a cohort of HIV-infected patients attending the Victorian HIV/AIDS Service between 1984 and 2000, and to examine whether antiretroviral therapy use or mortality was influenced by MHD (defined as a record of service provision by psychiatric services on the Victorian Psychiatric Case Register). It was hypothesized that HIV-positive individuals with MHD would have poorer treatment outcomes, reduced responses to highly active antiretroviral therapy (HAART) and increased mortality compared with those without MHD. Methods This is a retrospective cohort of 2981 individuals (73% of the Victorian population diagnosed with HIV infection) captured on an HIV database which was electronically matched with the public Victorian Psychiatric Case Register (VPCR) (accounting for 95% of public system psychiatry service provision). The prevalence, dates and recorded specifics of mental health disorders at the time of the electronic match on 1 June 2000 are described. The association with recorded MHD, gender, age, AIDS illness, HIV exposure category, duration and type of antiviral therapy, treatment era (prior to 1986, post-1987 and pre-HAART, and post-HAART) on hospitalization and mortality at 1 September 2001 was assessed. Results Five hundred and twenty-five individuals (17.6% of the Victorian HIV-positive population) were recorded with MHD, most frequently coded as attributable to substance dependence/abuse or affective disorder. MHD was diagnosed prior to HIV in 33% and, of those diagnosed after HIV, 93.8% were recorded more than 1 year after the HIV diagnosis. Schizophrenia was recorded in 6% of the population with MHD. Hospitalizations for both psychiatric and nonpsychiatric illness were more frequent in those with MHD (relative risk 5.4; 95% confidence interval 3.7, 8.2). The total number of antiretrovirals used (median 6.4 agents vs 5.5 agents) was greater in those with MHD. When adjusted for antiretroviral treatment era, HIV exposure category, CD4 cell count and antiretroviral therapy, survival was not affected by MHD. Conclusions MHD is frequent in this population with HIV infection and is associated with increased healthcare utilization but not with reduced survival.

Feasibility of a solar panel-powered liquid desiccant cooling system for greenhouses

To investigate the technical feasibility of a novel cooling system for commercial greenhouses, knowledge of the state of the art in greenhouse cooling is required. An extensive literature review was carried out that highlighted the physical processes of greenhouse cooling and showed the limitations of the conventional technology. The proposed cooling system utilises liquid desiccant technology; hence knowledge of liquid desiccant cooling is also a prerequisite before designing such a system. Extensive literature reviews on solar liquid desiccant regenerators and desiccators, which are essential parts of liquid desiccant cooling systems, were carried out to identify their advantages and disadvantages. In response to the findings, a regenerator and a desiccator were designed and constructed in lab. An important factor of liquid desiccant cooling is the choice of liquid desiccant itself. The hygroscopicity of the liquid desiccant affects the performance of the system. Bitterns, which are magnesium-rich brines derived from seawater, are proposed as an alternative liquid desiccant for cooling greenhouses. A thorough experimental and theoretical study was carried out in order to determine the properties of concentrated bitterns. It was concluded that their properties resemble pure magnesium chloride solutions. Therefore, magnesium chloride solution was used in laboratory experiments to assess the performance of the regenerator and the desiccator. To predict the whole system performance, the physical processes of heat and mass transfer were modelled using gPROMS® advanced process modelling software. The model was validated against the experimental results. Consequently it was used to model a commercials-scale greenhouse in several hot coastal areas in the tropics and sub-tropics. These case studies show that the system, when compared to evaporative cooling, achieves 3oC-5.6oC temperature drop inside the greenhouse in hot and humid places (RH>70%) and 2oC-4oC temperature drop in hot and dry places (50%

Optimization of Energy Distribution in Solar Panel Array Configurations by Graph Theory and Minkowski’s Paths

Nowadays, the development of the photovoltaic (PV) technology is consolidated as a source of renewable energy. The research in the topic of maximum improvement on the energy efficiency of the PV plants is today a major challenge. The main requirement for this purpose is to know the performance of each of the PV modules that integrate the PV field in real time. In this respect, a PLC communications based Smart Monitoring and Communications Module, which is able to monitor at PV level their operating parameters, has been developed at the University of Malaga. With this device you can check if any of the panels is suffering any type of overriding performance, due to a malfunction or partial shadowing of its surface. Since these fluctuations in electricity production from a single panel affect the overall sum of all panels that conform a string, it is necessary to isolate the problem and modify the routes of energy through alternative paths in case of PV panels array configuration.

Green roofs : understanding their benefits for Australia

Summary of Actions Towards Sustainable Outcomes Environmental Issues / Principal Impacts The increased growth of cities is intensifying its impact on people and the environment through: • increased use of energy for the heating and cooling of more buildings, leading to urban heat islands and more greenhouse gas emissions • increased amount of hard surfaces contributing to higher temperatures in cities and more stormwater runoff • degraded air quality and noise impact • reduced urban biodiversity • compromised health and general well-being of people Basic Strategies In many design situations boundaries and constraints limit the application of cutting EDGe actions. In these circumstances designers should at least consider the following: • Consider green roofs early in the design process in consultation with all stakeholders to enable maximised integration with building systems and to mitigate building cost (avoid constructing as a retrofit). • Design of the green roof as part of a building’s structural, mechanical and hydraulic systems could lead to structural efficiency, the ability to optimise cooling benefits and better integrated water recycling systems. • Inform the selection of the type of green roof by considering its function, for example designing for social activity, required maintenance/access regime, recycling of water or habitat regeneration or a combination of uses. • Evaluate existing surroundings to determine possible links to the natural environment and choice of vegetation for the green roof with availability of local plant supply and expertise. Cutting EDGe Strategies • Create green roofs to contribute positively to the environment through reduced urban heat island effect and building temperatures, to improved stormwater quality, increased natural habitats, provision of social spaces and opportunity for increased local food supply. • Maximise solar panel efficiency by incorporating with design of green roof. • Integrate multiple functions for a single green roof such as grey water recycling, food production, more bio-diverse plantings, air quality improvement and provision of delightful spaces for social interaction. Synergies & references • BEDP Environment Design Guide DES 53: Roof and Facade Gardens GEN 4: Positive Development – designing for Net Positive Impacts TEC 26: Living Walls - a way to green the built environment • Green Roofs Australia: www.greenroofs.wordpress.com • International Green Roof Association: www.igra-world.com • Green Roofs for Healthy Cities (USA): www.greenroofs.org • Centre for Urban Greenery and Ecology (Singapore): http://research.cuge.com.sg