Performance analysis & energy benefits of a desiccant based solar assisted trigeneration system in a building

In this paper, performance details and operational benefits of a large scale solar trigeneration system that provides for solar assisted desiccant cooling, heating and hot water generation installed in a teaching institute building have been reported. A two-rotor desiccant system designed for handling 12 000 m3/hr of air was integrated into existing plant to provide a net reduction in energy consumption over the pre-existing heating ventilation and air-conditioning and domestic hot water systems. The system is controlled and monitored by a building management system which has been used to investigate and analyse the typical system behaviour. Heat from solar energy contributed consistently to reduce gas usage for water heating and on an annual basis showed a reduction of 21% of consumed energy. The solar energy contribution for space heating varied over winter months and during some months it was observed to contribute more than 50% of the total energy requirements for space heating. Under suitable ambient conditions, approximately 35% of total building cooling load was met by the solar driven desiccant cooling system. Continuous monitoring has also helped understand some of the operational issues of the system.     

Measurements of solar radiation and illuminance on vertical surfaces and daylighting implications

There is a growing concern about the rapid development of infrastructure and building projects and their likely impacts on the environment. Particular concerns have been raised about office building developments and energy consumption issues. In recent years, there has been increasing interest in using daylight to save energy in buildings. Lighting control integrated with daylighting is recognised as an important and useful strategy in terms of energy-efficient building design. It is believed that proper daylighting schemes can help reduce the electrical demand and contribute to achieving environmentally sustainable building developments. This paper presents a simple method for estimating the likely energy savings in electric lighting due to daylighting and the possible cooling penalty. Vertical solar radiation and illuminance data measurements are described. Cumulative frequency distributions of daylight availability are reported. The likely energy savings in office buildings are determined based on on–off and top-up controls, and the energy and environmental implications are discussed.     

Maximising the light output of a Luminescent Solar Concentrator

Luminescent Solar Concentrators (LSC's) are currently being developed so that sunlight may be more fully utilised in place of conventional lighting sources. In order to optimise the light output of an LSC, various collector properties including fluorescent dye concentration, collector dimensions and matrix quality have been investigated. This study, involving measurement and computer modelling of the light transport in a single colour LSC, shows that luminous output is highly sensitive to weak extinction processes in the emission spectral band. These fine details in the loss spectrum play a key role in determining the output and efficiency of an LSC system. The separation of dye and matrix losses enables a quantitative study of the effect of matrix optical quality on performance.     

Looking into the Danish energy system: Lesson to be learned by other communities

Industrialization, development and social transformation has brought together issues of over exploitation of limited energy resource base (e.g. fossil fuel), accelerated threats of energy insecurity, and liberation of greenhouse gas emissions across the continents. The global challenge for the 21st century and way ahead is to find other means of satisfying energy needs, diversifying the energy supply, up-scaling the make-up of renewable energy to a greater extent, optimization of energy consumption and supply system. Denmark has been continuously moving towards optimization of energy production, usage and its overall management, during and even after the first global oil crisis. The country has been delivering its priority in the development of renewable energy and standing the country an energy self sufficient from last three decades. Country's overall consumption of energy has decreased than that of the decades of 1980 and 1990s, with wider range of energy mix and saving options. The Danish government has strategized to make the country fossil fuel free by 2050, where special attention and interventions is required to boost up its development of renewable energy in the country. The past efforts of the Danish government in the energy development has helped not only making the country ‘energy self sufficient’, but also lowering the level of carbon dioxide in the atmosphere. Danish energy policy and strategies have been found more conducive and reflective of the joint EU priorities on the matter of dealing with climate change and energy security. All the past progress and its allied policies seem to be quite supportive in fulfilling its strategies for greener future. This review paper will discuss on the past efforts of Danish government in energy management and highlights on some political initiatives, which have been realised to support the country moving towards clean and green energy future.     

Dye-sensitized solar cells based on natural and artificial phycobiliproteins to capture low light underwater

We developed dye-sensitized solar cells (DSSCs) based on natural and artificial phycobiliproteins (PBPs) to capture low light underwater. We assembled DSSCs with seven types of PBPs as sensitizers and studied their photoelectric properties. The results showed that the PBPs could markedly improve the photoelectrical properties of the DSSCs. The sensitization achieved by B-phycoerythrin (B-PE) from Porphyridium cruentum was superior to that of the other PBPs. The short-circuit current density, open circuit voltage, fill factor, and photoelectric conversion efficiency of the DSSC containing B-PE with a mesoporous titanium dioxide film as a photoelectrode were 3.236 mA/cm², 0.545 V, 0.569, and 1%, respectively. The DSSC based on B-PE displayed its highest photoelectric conversion efficiency between 525 and 570 nm. However, the maximum photoelectric conversion efficiencies of the DSSCs based on C-phycocyanin from Spirulina platensis and artificial PBPs were observed around 690 nm. DSSCs containing B-PE show great potential for use in underwater photovoltaic applications.     

A marketable all-electric solar house: A report of a Solar Decathlon project

This paper reports a design and building process of a net-zero-energy modular house, named ElementHouse, which was entered for the 2007 Solar Decathlon competition that was organized by the U.S. Department of Energy. This paper discusses the development of the ElementHouse from its initial concept to the actual construction, which integrated multi-disciplinary knowledge of architecture, mechanical engineering, and electrical engineering. By employing computer-aided simulation tools, several design approaches were developed to achieve the optimal balance among function, aesthetics, economy, and energy—a challenge in many sustainable building designs. A simplified energy model helped to form the building configuration at the preliminary design stage by showing how energy use is affected by various parameters, leading to optimization studies that provided design guidelines towards an energy-efficient building envelope and opening design. Energy modelling also estimated the annual energy use and electricity generation, as well as the costs associated with long-term operation of the house. The energy demand estimate and its daily power profile helped to design the photovoltaic (PV) system. The modular configuration of the building and its roof structure was then iteratively altered to accommodate the PV panels in such a way as to generate the most power and to facilitate interstate transportation of ElementHouse. With the progress of the design process, detailed energy simulation using EnergyPlus provided more accurate estimates of power use and generation and, coupled with daylighting simulation performed with Radiance, permitted finalizing the building envelope, opening, and electric lighting design. The building envelope embraced the passive and low energy philosophy to minimize the annual heating and cooling load and to optimize natural lighting. By illustrating the whole picture of ElementHouse design, this paper discusses a way of effectively designing and building a comfortable and affordable solar house.     

Determination of the origin of the illumination vector due to vertical windows under Moon-Spencer sky conditions (uniformly overcast)

This paper provides a procedure of easy approximation to obtain the direction of the illumination vector for a window under an overcast sky.When working with uniform skies, it is simple to demonstrate that the direction of the illumination vector is determined by the centre of the window and the illuminated point.However, when a luminance distribution is produced such as that specified by the Moon-Spencer law, the origin of the vector is no longer the centre of the window, but some point within a fragment of the window. In this paper, this fragment of window is delimited.     

Energy savings of office buildings by the use of semi-transparent solar cells for windows

The study investigated a PV window that consists of a double glazed window with semi-transparent solar cells. The window provides natural light transmission as well as electricity production. The effect of the PV window on energy consumption of office buildings was analyzed in terms of heating and cooling loads, daylighting, and electricity production. The purposes of the study were to find the optimum solar cell transmittance and window to wall ratio (WWR), and to estimate energy savings of the building. A standard floor of an office building was modeled to run computer simulation, and annual energy simulation was performed with EnergyPlus. The results showed that the solar cell transmittance of 40% and WWR of 50% achieved the minimum electricity consumption in the building when artificial lighting was controlled with daylighting. The optimum solar cell transmittance for PV windows in different orientation was also presented. By using the optimum PV window, the electricity consumption was reduced by 55% compared to the single glazed window with WWR of 30% and no lighting control.     

Experimental and numerical analysis of natural ventilation with combined light/vent pipes

Both experimental and numerical procedures were developed for studying natural ventilation in combined light/vent pipes. An experimental tracer gas technique was used to measure ventilation rates in a test cell. Two different pipe terminals were simultaneously used, dividing the cell in two identical volumes, in order to allow a direct comparison of their performance. A 3D numerical model was developed using ansys5.5/flotran. Experimental and numerical results are shown and compared. It is concluded that pipe terminals significantly enhance ventilation, that one type of terminal has a better performance and that the numerical model underestimates measured flows.     

Profits or preferences? Assessing the adoption of residential solar thermal technologies

Solar thermal technologies offer the potential to meet a substantial share of residential water and space heating needs in the EU, but current levels of adoption are low. This paper uses data from a large sample of German households to assess the effects of geographic, residence, and household characteristics on the adoption of solar thermal water and space heating technologies. In addition, the impact of solar thermal technology adoption on household energy expenditures is estimated after controlling for observed household heterogeneity in geographic, residential, and household characteristics. While evidence is found of moderate household energy expenditure savings from combined solar water and space heating systems, the findings generally confirm that low in-home energy cost savings and fixed housing stocks limit the diffusion of residential solar thermal technologies. Little evidence is found of differential adoption by distinct socio-economic groups.     

A methodology for the electrical energy system planning of Tamil Nadu state (India)

In this paper, an energy planning optimisation procedure of a selected territory is illustrated and applied using an energy flow optimisation model. The developed approach takes into account various electricity generating options to meet the energy needs of various demand sectors. Energy saving techniques and hybrid technologies are considered and various scenarios are developed by assessing the contribution of renewable energy technologies over the planning period. The procedure aims to reduce the total actualised cost of energy generation over selected time horizon and predicts the additional installations required along with the existing facilities to meet the energy demand. At the same time the role of renewable energy technologies and of energy saving measures is evaluated by imposing suitable constraints on CO₂ emissions and primary energy sources exploitation. The procedure is applied to the territory of Tamil Nadu state (India) by considering different energy planning scenarios.     

Experimental analysis of model predictive control for an energy efficient building heating system

Low energy buildings have attracted lots of attention in recent years. Most of the research is focused on the building construction or alternative energy sources. In contrary, this paper presents a general methodology of minimizing energy consumption using current energy sources and minimal retrofitting, but instead making use of advanced control techniques. We focus on the analysis of energy savings that can be achieved in a building heating system by applying model predictive control (MPC) and using weather predictions. The basic formulation of MPC is described with emphasis on the building control application and tested in a two months experiment performed on a real building in Prague, Czech Republic.     

Development and assessment of a novel solar heliostat-based multigeneration system

In this paper, a comprehensive study on thermodynamic analysis and assessment, through energy and exergy approaches, is conducted for a multigenerational solar based integrated energy system. The system proposed in this study is based on heliostat solar system integrated with steam turbine. The system is also integrated with seawater reverse osmosis desalination unit and absorption cooling system. The desalination unit operates with energy recovery through the utilization of Pelton turbine. The system produces cooling, heating, fresh water and hydrogen through electrolysis. It is furthermore designed to cover the demand of 4 MW electric power with the production of 1.25 kg/h of hydrogen and 90 kg/s of fresh water. The system advisor model software is applied on a case study for the solar heliostat optimization analysis.     

Towards green buildings: Glass as a building element—the use and misuse in the gulf region

The recent economic growth in the Gulf region notably in Dubai, United Arab Emirates (UAE) has led to a colossal number of buildings that has been constructed in the past 5 years. In the last decade, a total glazed building's façades became the icon of Dubai. This large area of glazing in each façade needs protection against overheating and sun glare in summer. According to leader in energy and environmental design (LEED) glass selection becomes a main element in this equation to contribute towards achieving a green building. The aim of this paper is to investigate the problems associated with misuse of glass, as a building element in UAE particularly in Dubai. Inadequate design with ill-selected glass/glazing type may lead not only to poor daylighting in building interiors but also contribute significantly to fatigue, insomnia, seasonal affective disorder (SAD) and above all increase CO₂ emission.The purpose of the study is to specify the required improvements to permit natural, ‘free’ daylight to filter through the building façade into interior space, especially with the right type of glass. This paper examines the status of buildings in Dubai in terms of glass type, visible light transmittance, reflection (out/in) and relative heat gain. A quantitative analysis is conducted to assess the impact of glass on the building users' performance in terms of daylight environment. A recent built high-rise office building was selected in the investigation to asses whether selected glass provide the recommended daylight factor (DF) and daylight level (DL) according to IES standards. The results revealed that most the glass/glazing was misused in 70% of buildings in intermediate and low performance groups. The DF and DD in the selected office building were unexpectedly tremendous and found far beyond the recommended level due to the use of spectrally selective glazing (clear on both sides).     

Method for simulating predictive control of building systems operation in the early stages of building design

A method for simulating predictive control of building systems operation in the early stages of building design is presented. The method uses building simulation based on weather forecasts to predict whether there is a future heating or cooling requirement. This information enables the thermal control systems of the building to respond proactively to keep the operational temperature within the thermal comfort range with the minimum use of energy. The method is implemented in an existing building simulation tool designed to inform decisions in the early stages of building design through parametric analysis. This enables building designers to predict the performance of the method and include it as a part of the solution space. The method furthermore facilitates the task of configuring appropriate building systems control schemes in the tool, and it eliminates time consuming manual reconfiguration when making parametric analysis. A test case featuring an office located in Copenhagen, Denmark, indicates that the method has a potential to save energy and improve thermal comfort compared to more conventional systems control. Further investigations of this potential and the general performance of the method are, however, needed before implementing it in a real building design.     

Performance of a combined solar heating system for residential applications in Greece

Combined solar heating is an emerging technology that offers the potential for realising more efficient use of solar thermal energy in order to cover space heating and domestic hot-water loads. This paper is focused on small-scale applications of single-family residential dwellings in Greece. A system-level model was developed and validated. The model was exercised to evaluate strategies for optimal design and operation of solar combisystems (SCSs), using a range of performance criteria as objective functions for optimisation. The effect of SCS design and operating variables on steady-state system performance has been investigated. System design and operation optimisation has been performed through the integration and synthesis of system-level modelling with system optimal design, optimisation, and annual simulation studies to provide a comprehensive assessment.     

A user-friendly procedure to visualize the hourly quantitative performance of daylighting systems

The paper reports on the academic experience of teaching daylighting to undergraduate architectural students. The case of teaching daylighting in the architectural professional program at Oklahoma State University is used as a case study. The paper provides a brief survey of the existing design-assisting tools and methods often used, in architectural education, to design and evaluate daylighting systems. These tools are the ones normally found in textbooks that are used to teach regular and/or advanced environmental control courses. As a result of the experimentation with the use of such handy methods in the architectural design studio, a limited benefit was observed. Although these tools can provide a good understanding of the issues and variables that may affect the performance of daylighting systems, students seldom use them in a design studio setting. In contrast, the suggested simplified procedure proved to be user-friendly. It was also found to be capable of visualizing the hourly performance of daylighting systems, and consequently building a comprehensive understanding of the performance of daylighting systems. This hands-on procedure provides quick and meaningful evaluation that can help students to further develop their daylighting designs to meet the predefined goals.The paper does not intend to present a new method of daylighting systems design and/or evaluation. However, it will present a procedure that helped architectural students to visualize, further develop, and comprehensively understand the performance of their daylighting designs.     

Performances of the Barra–Costantini passive heating system under Algerian climate conditions

The present work studies the Barra–Costantini passive solar heating system, with particular emphasis on the aspect of economics. The system which is studied is developed by Barra and Constantini. This system seems to be well adapted to the climatic and economic conditions in Algeria. In the first part of this work, an ideal model representing the thermal behavior of a room provided with the heating device is elaborated. The results of this model are compared with the results of an experimental study carried out on an Italian site. Initially, the model was used to determine the temperature variation for the different elements of a room with the Barra–Costantini (B-C) system. The model is then used for conditions corresponding to several Algerian sites. This study makes it possible to quantify the energy savings obtained by the addition of the B-C system to a traditional gas heating system. The introduction of a ratio between the cost of energy and the cost of equipment makes it possible to conclude that only the intervention of the authorities can make the passive solar system economically viable.     

A genetic algorithm solution to the design of slat-type shading system

This article presents a technique for the design of slat-type blinds based on the their relative light intensity distribution under a uniform light source. The technique offers a new approach using a genetic algorithm in order to evolve the design according to a set of parameters.     

Abnormally high photocurrent of a degraded organic solar cell under chopped light

Photocurrent of an organic solar cell under chopped monochromatic light was studied at different stages, i.e. just after fabrication (without degradation) and after serious degradation. A large photocurrent under chopped light was observed for a seriously degraded device, unexpected from intuitionistic reckoning. This work demonstrates that both light bias and chopper frequency affect the photocurrent measurement of an organic solar cell, especially for a degraded device. The influence of light bias and chopper frequency is explained as the result of traps produced during the degradation of an organic solar cell. Thus measuring photocurrent under one sun light bias at low chopper frequency is suggested to more accurately determine the external quantum efficiency.