Showing papers in "Renewable & Sustainable Energy Reviews in 1998"

Sustainable Energy Development

Abstract: In order to reach the goals indicated by the sustainable energy development the efficiency in the energy conversion use has to meet several criterions [1]. The potential for the efficiency improvement is generally underestimated. Most of the energy conversion systems consider the efficiency improvement as a separate process and their analysis reflects only the potential improvement of the process but not the potential for the efficiency improvement obtained by an exergy analysis of the energy system. Fossil fuel energy resources use is mostly conversion to heat by the combustion processes. Since the combustion process is taking place at temperatures between 900 — 1300°C and over 40% of heat is used a low temperature heat, it is indispensable to take into consideration the thermodynamic assessment of the efficiency in order to bring in line energy conversion processes and energy demand to obtain the optimum fuel utilization.

Flow and heat transfer in the air gap behind photovoltaic panels

Abstract: The impetus of this paper is to analyse numerically and experimentally the flow and heat transfer characteristics of buoyancy-driven air convection behind photovoltaic panels. Both convection and radiation heat exchanges are considered as the heat transfer mechanisms by which the thermal energy is transferred into the air. Numerical and experimental results are obtained for a channel of 7.0 m in height and the channel walls are separated by a distance of 0.23 m. In the experiment heat is supplied to the air gap from heating foil attached to one of the vertical walls. Different input heat fluxes and emissivity of the bounding surfaces are considered in order to show their effect on the heat transfer across the air layer. Detailed studies of the flow and thermal fields in the air are presented in order to explore the thermal behaviour of the air in the channel. Velocity and temperature profiles of the outlet air and the surface temperature of the heated and insulated wall is presented. The numerical results agreed well with the experimental measurements.

Financing investments in renewable energy : the impacts of policy design

Abstract: The costs of electric power projects utilizing renewable energy technologies (RETs) are highly sensitive to financing terms. Consequently, as the electricity industry is restructured and new renewables policies are created, it is important for policymakers to consider the impacts of renewables policy design on RET financing. This paper reviews the power plant financing process for renewable energy projects, estimates the impact of financing terms on levelized energy costs, and provides insights to policymakers on the important nexus between renewables policy design and financing. We review five case studies of renewable energy policies, and find that one of the key reasons that RET policies are not more effective is that project development and financing processes are frequently ignored or misunderstood when designing and implementing renewable energy policies. The case studies specifically show that policies that do not provide long-term stability or that have negative secondary impacts on investment decisions will increase financing costs, sometimes dramatically reducing the effectiveness of the program. Within U.S. electricity restructuring proceedings, new renewable energy policies are being created, and restructuring itself is changing the way RETs are financed. As these new policies are created and implemented, it is essential that policymakers acknowledge the financing difficulties faced by renewables developers and pay special attention to the impacts of renewables policy design on financing. As shown in this paper, a renewables policy that is carefully designed can reduce renewable energy costs dramatically by providing revenue certainty that will, in turn, reduce financing risk premiums.

Bioclimatism in vernacular architecture

Abstract: Any analysis of the role played by energy in architecture is faced with serious limitations due to the lack of studies in the architectural bibliography, especially studies of popular architecture. An awareness of these limitations will allow us to understand better why architects have paid little attention to the interaction of form and energy, and to the bioclimatic approach in contemporary architecture in general. The first limitation stems from the very essence of bioclimatic analysis; energy is immaterial, difficult to represent in images, changing in time and wrongfully left out of the architectural literature. This is why it is difficult to find a basic knowledge of the functional aesthetic possibilities of bioclimatism in the cultural experience of present-day architects. The second limitation to this knowledge, even more important than the previous one, is the low value given to the more anonymous popular architecture as opposed to representative architecture. The latter is the kind of architecture built by established power, which attempts to impress the observer and clashes with, dominates, and often destroys the natural environment. This style of architecture is crammed with theoretical aesthetic concerns, which would rather create artificial environments than be integrated in the natural milieu. To sum up, it is the architecture undertaken by well-known authors, found in important buildings, which have been commented and widely appreciated by architecture critics throughout history. Nowadays, representative architecture can be said to describe the architecture found in large office buildings, which embody the legacy of such works from the history of culture as the pyramids, classic shrines, medieval castles and large Gothic cathedrals, baroque and Renaissance palaces, etc. These modern buildings, clad in glass as a symbol of their modernity, are incongruously dark and require artificial lighting during the day, while the flimsy casing separating them from the outside makes it necessary to use air conditioning all year round, even when outside conditions are pleasant. We can well affirm that these buildings are so wrong that they work worse than the climate. In comparison with this type of representative architecture, we find popular architecture, performed by the people as a direct response to their needs and values. These buildings show a greater respect for the existing environment, whether natural or artificial. They do not reflect theoretical aesthetic pretensions and use local materials and techniques as far as possible, repeating over and over again the course of history models which take the constraints imposed by the climate fully into account. Our popular architecture—so often forgotten in official circles—may well be the kind which can best teach us today how to assimilate the bioclimatic approach in the practice of architectural design. However, we should not consider these solutions to be models to copy in current architecture. Our technical capacity and our cultural grounding prevent us from returning to these obsolete architecture forms, but what may be of use as a lesson and a source of inspiration is the attitude of the builders of this popular architecture, which recovers a relationship to the environment which has been lost in the more official architecture of the 20th century.

Chapter 4 : bioclimatism in vernacular architecture

Abstract: Any analysis of the role played by energy in architecture is faced with serious limitations due to the lack of studies in the architectural bibliography, especially studies of popular architecture. An awareness of these limitations will allow us to understand better why architects have paid little attention to the interaction of form and energy, and to the bioclimatic approach in contemporary architecture in general. The first limitation stems from the very essence of bioclimatic analysis; energy is immaterial, difficult to represent in images, changing in time and wrongfully left out of the architectural literature. This is why it is difficult to find a basic knowledge of the functional aesthetic possibilities of bioclimatism in the cultural experience of present-day architects. The second limitation to this knowledge, even more important than the previous one, is the low value given to the more anonymous popular architecture as opposed to representative architecture. The latter is the kind of architecture built by established power, which attempts to impress the observer and clashes with, dominates, and often destroys the natural environment. This style of architecture is crammed with theoretical aesthetic concerns, which would rather create artificial environments than be integrated in the natural milieu. To sum up, it is the architecture undertaken by well-known authors, found in important buildings, which have been commented and widely appreciated by architecture critics throughout history. Nowadays, representative architecture can be said to describe the architecture found in large office buildings, which embody the legacy of such works from the history of culture as the pyramids, classic shrines, medieval castles and large Gothic cathedrals, baroque and Renaissance palaces, etc. These modern buildings, clad in glass as a symbol of their modernity, are incongruously dark and require artificial lighting during the day, while the flimsy casing separating them from the outside makes it necessary to use air conditioning all year round, even when outside conditions are pleasant. We can well affirm that these buildings are so wrong that they work worse than the climate. In comparison with this type of representative architecture, we find popular architecture, performed by the people as a direct response to their needs and values. These buildings show a greater respect for the existing environment, whether natural or artificial. They do not reflect theoretical aesthetic pretensions and use local materials and techniques as far as possible, repeating over and over again the course of history models which take the constraints imposed by the climate fully into account. Our popular architecture—so often forgotten in official circles—may well be the kind which can best teach us today how to assimilate the bioclimatic approach in the practice of architectural design. However, we should not consider these solutions to be models to copy in current architecture. Our technical capacity and our cultural grounding prevent us from returning to these obsolete architecture forms, but what may be of use as a lesson and a source of inspiration is the attitude of the builders of this popular architecture, which recovers a relationship to the environment which has been lost in the more official architecture of the 20th century.

Passive solar urban design : ensuring the penetration of solar energy into the city

Abstract: Site layout has a big impact on the viability of passive solar heating in buildings, as tall obstructions can block low winter sun. This paper reviews a range of tools to predict solar access in obstructed situations. They range from simple angular criteria, through sunpath diagrams and solar gain indicators to computer programs. The paper then examines criteria and techniques that can be used to evaluate solar access in dense urban layouts. Ways to protect solar access to existing buildings are also examined. Many of the techniques currently available are less suited to urban areas at high latitude. The paper suggests alternative approaches.

Energy requirements of thin-film solar cell modules—a review

Abstract: In this paper a number of energy analysis studies for thin-film solar cell modules are compared and reviewed. We start with a short introduction into methodological issues related to energy analysis (of PV systems) such as system boundary definition, treatment of different (secondary) energy types and the choice of functional unit. Subsequently we review results from 6 studies on a-Si modules and 3 studies on CdTe modules. The aim is to present results in a unified format, compare them and try to clarify observed differences. Although significant differences were found, many of these differences could be explained by the choice of materials for the module encapsulation. For categories with large observed differences, like indirect process energy and capital equipment energy, we performed additional analyses in order to gain a better understanding of these aspects. Finally we present best estimates of the energy requirement for present-day a-Si and CdTe thin film modules which are between 600 and 1500 MJ (primary energy) per m fn3 module area, depending on cell and encapsulation type. This means that the energy pay-back time is below two years for a grid-connected module under 1700 kWh⧹m2⧹yr irradiation. In the near future an energy pay-back time below one year seems feasible.

Chapter 3—Principles of thermal comfort

Abstract: The human body, considered as a thermodynamic system, produces mechanical work and low temperature heat, using food (fuel) and oxygen as input. This system requires, in healthy conditions, to maintain a constant internal temperature around 37±0.5°C, otherwise the functionality of important organs like liver, spleen, etc, may be severely damaged. fn2 In order to achieve this goal, the rate of heat generation of the body must be equal to the rate of heat loss from it. The job of our thermoregulatory system is to maintain the heat balance, that is a fundamental condition for survival and necessary (but not sufficient) for comfort. Skin temperature, otherwise, is not constant, and it varies according to the part of the body and the air temperature; the absolute maximum and the minimum values, however, are 45 and 4°C (pain thresholds).

Mesoscale interactions on wind energy potential in the northern Aegean region: a case study

Abstract: Aegean coast and surrounding areas are promising higher wind power potential. In this study the reasons of the higher wind power potential in the region of the northern Aegean coast of Turkey and surrounding islands were discussed. The channel effect, route of cyclones and surface pressure gradients were evaluated over the region. Estimated results of the Weibull parameters illustrate the higher wind power potential in the region.

Effect of wind energy system performance on optimal renewable energy model—an analysis

Abstract: The Optimal Renewable Energy Model (OREM) has been developed to determine the optimum level of renewable energy sources utilisation in India for the year 2020–21. The model aims at minimising cost⧹efficiency ratio and determines the optimum allocation of different renewable energy sources for various end-uses. The extent of social acceptance level, potential limit, demand and reliability will decide the renewable energy distribution pattern and are hence used as constraints in the model. In this paper, the performance and reliability of wind energy system and its effects on OREM model has been analysed. The demonstration windfarm (4 MW) which is situated in Muppandal, a village in the southern part of India, has been selected for the study. The windfarm has 20 wind turbine machines of 200 KW capacity. The average technical availability, real availability and capacity factor have been analysed from 1991 to 1995 and they are found to be 94.1%, 76.4% and 25.5% respectively. The reliability factor of wind energy system is found to be 0.5 at 10,000 hours. The OREM model is analysed considering the above said factors for wind energy system, solar energy system and biomass energy systems. The model selects wind energy for pumping end-use to an extent of 0.3153×1015 KJ.

Chapter 6 : daylighting

Abstract: To talk of architecture is to talk of light, and above all of natural light. It is not just a physical means enabling us to see the exterior and interior material form of buildings; rather, it provides architecture with its main energy component, necessary for the existence of a rich, integrated duality of matter and energy which, beyond mere usefulness, generates an aesthetic sensation in the users. It is for this reason that great architecture has always been associated with natural lighting, generating it with and within itself. From the categorical eloquence of the single opening of the Pantheon to the magical complexity of the Germanic baroque, via the increasingly finely wrought Gothic cathedrals, natural light has been a deciding factor in the quality of space. In spite of this, the role played by light in architectural aesthetics is often ignored, great works being analysed with parameters that are concerned purely with style and geometric form. In the narrower sense of architectural quality, the aesthetic power of light is what differentiates architecture from mere construction when we visit a building. Such it has been described by the great commentators on architecture, from Vitruvius to Bruno Zeni, when they speak of light with the enthusiasm that art alone can arouse. Yet when we attempt to analyse the role of light in contemporary architecture, we find a huge vacuum. Todays representative buildings almost totally neglect the important part natural light could play in their interiors. Excessive use is made of artificial systems, and architecture is conceptualized as glass geometry, with paradoxical curtain walls that instead of communicating with the exterior, create impractical barriers. A point is thus reached where the interior environment, which is theoretically controlled, frequently becomes more inhospitable than the exterior. In such cases, architecture works worse than the climate. Today, it is essential for the architectural profession to recover the systematic use of natural light. To this end, designers should be made aware of how spaces work in conjunction with light, and the best way to do this is not by way of elegant or sophisticated technical solutions. It is sufficient to be acquainted with certain basic principles, which can be divided into two well-defined areas: the physics of light and the physiology of vision. These basic principles can lead to the practice of natural light in design with greater efficiency than would be the case with the technology of particular solutions and systems. The physics of light allows us to understand how this electromagnetic radiation behaves in architectural space. By knowing its basic laws and its interaction with the surfaces that reflect, absorb and transmit it, we can control the effect of light on buildings and its distribution in interiors. The physiology (and psychology) of vision facilitates understanding of human reactions in lit spaces. By knowing the basic principles of perception and comfort, as we design buildings we can control the relationship between light and the users of their exterior and interior environments, and in this way define the lighting aesthetically and functionally from the very start of the project. Finally, providing a building with natural light is more than just the solution of a problem of energy consumption; more, even, than an aesthetic resource easily incorporated into the architecture. Natural light in architecture must be part of a more general philosophy that reflects a more respectful, sensitive attitude in human beings towards the environment in which they live.

A guide to the Kyoto protocol: a treaty with potentially vital strategic implications for the renewables industry

Abstract: Why should renewables advocates care about the arcane business of multilateral climate negotiations? The answer is simple. Because these long-running and oft bogged-down talks have as their ultimate objective a goal with seismic implications for energy markets: substantial reductions in greenhouse gas emissions. Coming anywhere close to that goal would entail the creation of multi-hundred billion dollar markets in renewables in the years ahead. And in Kyoto last December, governments took a meaningful first step in that direction. This paper is a brief summary, and analysis of that first step. It concludes with some observations about immediate implications for the renewables industries.