Showing papers on "Efficient energy use published in 2008"

Energy storage systems—Characteristics and comparisons

Abstract: Electricity generated from renewable sources, which has shown remarkable growth worldwide, can rarely provide immediate response to demand as these sources do not deliver a regular supply easily adjustable to consumption needs. Thus, the growth of this decentralized production means greater network load stability problems and requires energy storage, generally using lead batteries, as a potential solution. However, lead batteries cannot withstand high cycling rates, nor can they store large amounts of energy in a small volume. That is why other types of storage technologies are being developed and implemented. This has led to the emergence of storage as a crucial element in the management of energy from renewable sources, allowing energy to be released into the grid during peak hours when it is more valuable. The work described in this paper highlights the need to store energy in order to strengthen power networks and maintain load levels. There are various types of storage methods, some of which are already in use, while others are still in development. We have taken a look at the main characteristics of the different electricity storage techniques and their field of application (permanent or portable, long- or short-term storage, maximum power required, etc.). These characteristics will serve to make comparisons in order to determine the most appropriate technique for each type of application.

Energy, environment and sustainable development

Abstract: Globally, buildings are responsible for approximately 40% of the total world annual energy consumption. Most of this energy is for the provision of lighting, heating, cooling, and air conditioning. Increasing awareness of the environmental impact of CO2 and NOx emissions and CFCs triggered a renewed interest in environmentally friendly cooling, and heating technologies. Under the 1997 Montreal Protocol, governments agreed to phase out chemicals used as refrigerants that have the potential to destroy stratospheric ozone. It was therefore considered desirable to reduce energy consumption and decrease the rate of depletion of world energy reserves and pollution of the environment. One way of reducing building energy consumption is to design building, which are more economical in their use of energy for heating, lighting, cooling, ventilation and hot water supply. Passive measures, particularly natural or hybrid ventilation rather than air-conditioning, can dramatically reduce primary energy consumption. However, exploitation of renewable energy in buildings and agricultural greenhouses can, also, significantly contribute towards reducing dependency on fossil fuels. Therefore, promoting innovative renewable applications and reinforcing the renewable energy market will contribute to preservation of the ecosystem by reducing emissions at local and global levels. This will also contribute to the amelioration of environmental conditions by replacing conventional fuels with renewable energies that produce no air pollution or greenhouse gases. The provision of good indoor environmental quality while achieving energy and cost-efficient operation of the heating, ventilating and air-conditioning (HVAC) plants in buildings represents a multi-variant problem. The comfort of building occupants is dependent on many environmental parameters including air speed, temperature, relative humidity and quality in addition to lighting and noise. The overall objective is to provide a high level of building performance (BP), which can be defined as indoor environmental quality (IEQ), energy efficiency (EE) and cost efficiency (CE). • Indoor environmental quality is the perceived condition of comfort that building occupants experience due to the physical and psychological conditions to which they are exposed by their surroundings. The main physical parameters affecting IEQ are air speed, temperature, relative humidity and quality. • Energy efficiency is related to the provision of the desired environmental conditions while consuming the minimal quantity of energy. • Cost efficiency is the financial expenditure on energy relative to the level of environmental comfort and productivity that the building occupants attained. The overall cost efficiency can be improved by improving the indoor environmental quality and the energy efficiency of a building. This article discusses the potential for such integrated systems in the stationary and portable power market in response to the critical need for a cleaner energy technology. Anticipated patterns of future energy use and consequent environmental impacts (acid precipitation, ozone depletion and the greenhouse effect or global warming) are comprehensively discussed in this paper. Throughout the theme several issues relating to renewable energies, environment and sustainable development are examined from both current and future perspectives.

Report to Congress on Server and Data Center Energy Efficiency: Public Law 109-431

Abstract: This report was prepared in response to the request from Congress stated in Public Law 109-431 (H.R. 5646),"An Act to Study and Promote the Use of Energy Efficient Computer Servers in the United States." This report assesses current trends in energy use and energy costs of data centers and servers in the U.S. (especially Federal government facilities) and outlines existing and emerging opportunities for improved energy efficiency. It also makes recommendations for pursuing these energy-efficiency opportunities broadly across the country through the use of information and incentive-based programs.

Energy aware consolidation for cloud computing

Abstract: Consolidation of applications in cloud computing environments presents a significant opportunity for energy optimization. As a first step toward enabling energy efficient consolidation, we study the inter-relationships between energy consumption, resource utilization, and performance of consolidated workloads. The study reveals the energy performance trade-offs for consolidation and shows that optimal operating points exist. We model the consolidation problem as a modified bin packing problem and illustrate it with an example. Finally, we outline the challenges in finding effective solutions to the consolidation problem.

Transportation energy data book

Abstract: The Transportation Energy Data Book: Edition 11 is a statistical compendium prepared and published by Oak Ridge National Laboratory (ORNL) under contract with the Office of Transportation Technologies in the Department of Energy (DOE). Designed for use as a desk-top reference, the data book represents an assembly and display of statistics and information that characterize transportation activity, and presents data on other factors that influence transportation energy use. The purpose of this document is to present relevant statistical data in the form of tables and graphs. Each of the major transportation modes - highway, air, water, rail, pipeline - is treated in separate chapters or sections. Chapter 1 compares US transportation data with data from seven other countries. Aggregate energy use and energy supply data for all modes are presented in Chapter 2. The highway mode, which accounts for over three-fourths of total transportation energy consumption, is dealt with in Chapter 3. Topics in this chapter include automobiles, trucks, buses, fleet automobiles, federal standards, fuel economies, and household data. Chapter 4 is a new addition to the data book series, containing information on alternative fuels and alternatively-fueled vehicles. The last chapter, Chapter 5, covers each of the nonhighway modes: air,more » water, pipeline, and rail, respectively. 92 figs., 112 tabs.« less

Energy Efficiency and Renewable Energy

Abstract: To achieve a sustained growth of 8 per cent during the period 2005–31, India would need to grow its primary energy supply by three to four times. Similarly, China’s energy demand is expected to increase by two to two-and-a-half times during the same period. By 2030, the two countries combined together would account for around 25 per cent of the total energy consumption in the world and would become two of the largest carbon dioxide (CO 2 ) emitters. The overall demand for energy in the two countries can be significantly lowered by adopting energy efficiency measures to lower energy intensity. A recent report suggests that the overall energy consumption can be reduced by 25 per cent by taking appropriate energy conservation measures in India. Also, a rapid deployment of new renewable energy technologies, both for electricity generation and for thermal applications, can result in significant reduction in demand for fossil fuels. These measures would not only result in lowering the CO 2 emissions and reducing the dependence of the two countries on energy imports, but would also assist in building of a more sustainable and efficient energy infrastructure in the two countries. Some of the common areas of interest for the two countries in energy efficiency and renewable energy are:

Energy-Efficient Cooperative Communication Based on Power Control and Selective Single-Relay in Wireless Sensor Networks

Abstract: Cooperative communication with single relay selection is a simple but effective communication scheme for energy-constrained networks. In this paper, we propose a novel selective single-relay cooperative scheme, combining selective-relay cooperative communication with physical-layer power control. Based on the MAC-layer RTS-CTS signaling, a set of potential relays compute individually the required transmission power to participate in the cooperative communication, and compete within a window of fixed length. The "best" relay is selected in a distributed fashion with minimum signaling overhead. We derive power-control solutions corresponding to two policies on relay selection: one is to minimize the energy consumption per data packet, and the other is to maximize the network lifetime. Our numerical and simulation results confirm that the proposed scheme achieves significant energy savings and prolongs the network lifetime considerably.

Y-MAC: An Energy-Efficient Multi-channel MAC Protocol for Dense Wireless Sensor Networks

Abstract: As the use of wireless sensor networks (WSNs) becomes widespread, node density tends to increase. This poses a new challenge for Medium Access Control (MAC) protocol design. Although traditional MAC protocols achieve low-power operation, they use only a single channel which limits their performance. Several multi-channel MAC protocols for WSNs have been recently proposed. One of the key observations is that these protocols are less energy efficient than single-channel MAC protocols under light traffic conditions. In this paper, we propose an energy efficient multi-channel MAC protocol, Y-MAC, for WSNs. Our goal is to achieve both high performance and energy efficiency under diverse traffic conditions. In contrast to most of previous multi-channel MAC protocols for WSNs, we implemented Y-MAC on a real sensor node platform and conducted extensive experiments to evaluate its performance. Experimental results show that Y-MAC is energy efficient and maintains high performance under high-traffic conditions.

DW-MAC: a low latency, energy efficient demand-wakeup MAC protocol for wireless sensor networks

Abstract: Duty cycling is a widely used mechanism in wireless sensor networks (WSNs) to reduce energy consumption due to idle listening, but this mechanism also introduces additional latency in packet delivery. Several schemes have been proposed to mitigate this latency, but they are mainly optimized for light traffic loads. A WSN, however, could often experience bursty and high traffic loads, such as due to broadcast or convergecast traffic. In this paper, we present a new MAC protocol, called Demand Wakeup MAC (DW-MAC), that introduces a new low-overhead scheduling algorithm that allows nodes to wake up on demand during the Sleep period of an operational cycle and ensures that data transmissions do not collide at their intended receivers. This demand wakeup adaptively increases effective channel capacity during an operational cycle as traffic load increases, allowing DW-MAC to achieve low delivery latency under a wide range of traffic loads including both unicast and broadcast traffic. We compare DW-MAC with S-MAC (with and without adaptive listening) and with RMAC using ns-2 and show that DW-MAC outperforms these protocols, with increasing benefits as traffic load increases. For example, under high unicast traffic load, DW-MAC reduces delivery latency by 70% compared to S-MAC and RMAC, and uses only 50% of the energy consumed with S-MAC with adaptive listening. Under broadcast traffic, DW-MAC reduces latency by more than 50% on average while maintaining higher energy efficiency.

Rendezvous design algorithms for wireless sensor networks with a mobile base station

Abstract: Recent research shows that significant energy saving can be achieved in wireless sensor networks with a mobile base station that collects data from sensor nodes via short-range communications. However, a major performance bottleneck of such WSNs is the significantly increased latency in data collection due to the low movement speed of mobile base stations. To address this issue, we propose a rendezvous-based data collection approach in which a subset of nodes serve as the rendezvous points that buffer and aggregate data originated from sources and transfer to the base station when it arrives. This approach combines the advantages of controlled mobility and in-network data caching and can achieve a desirable balance between network energy saving and data collection delay. We propose two efficient rendezvous design algorithms with provable performance bounds for mobile base stations with variable and fixed tracks, respectively. The effectiveness of our approach is validated through both theoretical analysis and extensive simulations.

An energy efficient Swedish pulp and paper industry – exploring barriers to and driving forces for cost-effective energy efficiency investments

Abstract: Despite the need for increased industrial energy efficiency, studies indicate that cost-effective energy efficiency measures are not always implemented, which is explained by the existence of barri ...

Nericell: using mobile smartphones for rich monitoring of road and traffic conditions

Abstract: We consider the problem of monitoring road and traffic conditions in a city. Prior work in this area has required the deployment of dedicated sensors on vehicles and/or on the roadside, or the tracking of mobile phones by service providers. Furthermore, prior work has largely focused on the developed world, with its relatively simple traffic flow patterns. In fact, traffic flow in cities of the developing regions, which comprise much of the world, tends to be much more complex owing to varied road conditions (e.g., potholed roads), chaotic traffic (e.g., a lot of braking and honking), and a heterogeneous mix of vehicles (2-wheelers, 3-wheelers, cars, buses, etc.).To monitor road and traffic conditions in such a setting, we present Nericell, a system that performs rich sensing by piggybacking on smartphones that users carry around with them. In this demo, we show the use of accelerometer to detect bumps and braking. We also use the microphone to enable honk detection. Nericell addresses several challenges including virtually reorienting the accelerometer on a phone that is at an arbitrary orientation, and performing honk detection and localization in an energy efficient manner.

Energy and environmental indicators related to construction of office buildings

Abstract: Buildings’ construction has a major determining role on the environment through consumption of land and raw materials and generation of waste. It is also a significant user of non-renewable energy and an emitter of greenhouse gases and other gaseous wastes. As environmental issues continue to become increasingly significant, buildings become more energy efficient and the energy needs for their operation decreases. Thus, the energy required for construction and consequently, for the material production, is getting of greater importance. The present paper investigates the role of different construction materials and quantifies them in terms of the embodied energy and the equivalent emissions of CO 2 and SO 2 in contemporary office buildings. It also assesses the importance of the embodied energy of the building's structure as compared to the operational energy of the building. It was shown that the embodied energy of the structure's building materials (concrete and reinforcement steel) represents the largest component in the building's total embodied energy of the examined buildings, varing from 66.73% to 59.57%, while the embodied energy of the building envelope's materials represents a lower but significant proportion of the building's total embodied energy. When the construction elements are examined, the slabs have the higher contribution at the embodied energy of the studied buildings and from the envelope elements, the external wall is contributing the maximum in the overall embodied energy of the building. The embodied energy correspondence varies between 12.55 and 18.50% of the energy needed for the operation of an office building over a 50 years life.

An Empirical Analysis of Energy Intensity and Its Determinants at the State Level

Abstract: Aggregate energy intensity in the United States has been declining steadily since the mid-1970s and the first oil shock. Energy intensity can be reduced by improving efficiency in the use of energy or by moving away from energy-intensive activities. At the national level, I show that roughly three-quarters of the improvements in U.S. energy intensity since 1970 results from efficiency improvements. This should reduce concerns that the United States is off-shoring its carbon emissions. A state-level analysis shows that rising per capita income and higher energy prices have played an important part in lowering energy intensity. Price and income predominantly influence intensity through changes in energy efficiency rather than through changes in economic activity. In addition, the empirical analysis suggests that little policy intervention will be needed to achieve the Bush Administration goal of an 18 percent reduction in carbon intensity by the end of this decade.

Energy Efficient Design in Wireless OFDMA

Abstract: Energy-efficient transmission is an important aspect of wireless system design due to limited battery power in mobile devices. We consider uplink energy-efficient transmission in OFDMA systems since mobile stations are battery powered. We account for both circuit and transmit power when designing energy-efficient communication mechanisms and emphasize energy efficiency over peak rates or throughput. Both link adaptation and resource allocation schemes are developed to optimize the overall bits transmitted per Joule of energy, which allows for maximum energy savings in a network. Our simulation results show that the proposed schemes significantly improve energy efficiency.

A Simple Algorithm for Data Compression in Wireless Sensor Networks

Abstract: Power saving is a critical issue in wireless sensor networks (WSNs) since sensor nodes are powered by batteries which cannot be generally changed or recharged. As radio communication is often the main cause of energy consumption, extension of sensor node lifetime is generally achieved by reducing transmissions/receptions of data, for instance through data compression. Exploiting the natural correlation that exists in data typically collected by WSNs and the principles of entropy compression, in this Letter we propose a simple and efficient data compression algorithm particularly suited to be used on available commercial nodes of a WSN, where energy, memory and computational resources are very limited. Some experimental results and comparisons with, to the best of our knowledge, the only lossless compression algorithm previously proposed in the literature to be embedded in sensor nodes and with two well- known compression algorithms are shown and discussed.

Renewable building energy systems and passive human comfort solutions

Abstract: With environmental protection posing as the number one global problem, man has no choice but to reduce his energy consumption. One way to accomplish this is to resort to passive and low-energy systems to maintain thermal comfort in buildings. The conventional and modern designs of wind towers can successfully be used in hot arid regions to maintain thermal comfort (with or without the use of ceiling fans) during all hours of the cooling season, or a fraction of it. Climatic design is one of the best approaches to reduce the energy cost in buildings. Proper design is the first step of defence against the stress of the climate. Buildings should be designed according to the climate of the site, reducing the need for mechanical heating or cooling. Hence maximum natural energy can be used for creating a pleasant environment inside the built envelope. Technology and industry progress in the last decade diffused electronic and informatics’ devices in many human activities, and also in building construction. The utilisation and operating opportunities components, increase the reduction of heat losses by varying the thermal insulation, optimise the lighting distribution with louver screens and operate mechanical ventilation for coolness in indoor spaces. In addition to these parameters the intelligent envelope can act for security control and became an important part of the building domotic revolution. Application of simple passive cooling measure is effective in reducing the cooling load of buildings in hot and humid climates. Fourty-three percent reductions can be achieved using a combination of well-established technologies such as glazing, shading, insulation, and natural ventilation. More advanced passive cooling techniques such as roof pond, dynamic insulation, and evaporative water jacket need to be considered more closely. The building sector is a major consumer of both energy and materials worldwide, and that consumption is increasing. Most industrialised countries are in addition becoming more and more dependent on external supplies of conventional energy carriers, i.e., fossil fuels. Energy for heating and cooling can be replaced by new renewable energy sources. New renewable energy sources, however, are usually not economically feasible compared with the traditional carriers. In order to achieve the major changes needed to alleviate the environmental impacts of the building sector, it is necessary to change and develop both the processes in the industry itself, and to build a favourable framework to overcome the present economic, regulatory and institutional barriers. This article describes various designs of low-energy buildings. It also, outlines the effect of dense urban building nature on energy consumption, and its contribution to climate change. Measure, which would help to save energy in buildings, is also presented.

On the Efficiency of Voltage Source and Current Source Inverters for High-Power Drives

Abstract: The energy performance of various types of voltage-source and current-source converters is examined. For fairness and completeness, efficiency is calculated for three major battleground scenarios. The first is a low dynamic nonregenerative group of applications such as pumps, fans, and compressors. This group represents 85% of high power (2 MW) industrial applications where energy savings are usually a primary consideration justifying investment. The second scenario considers applications requiring good dynamic response and regenerative braking. Finally, the third group considers very high power applications (over 20 MW). The evaluation presented takes into account semiconductor switching and conduction losses, losses in the medium voltage feeding transformer (determined per IEEE Standard C57.18.10-1998), and the losses in ac and dc filters. For purposes of analysis, computer simulations validated against measurements taken on a 1-MW voltage source inverter (VSI) and a 1.4-MW current source inverter (CSI) were used. The results of the first scenario show competitive efficiencies for VSI and CSI drives, whereas voltage source-based solutions are more energy efficient in the second scenario considered. For the last group, the current source load-commutated inverter exhibits the best performance.

Improving the energy performance of UK households: Results from surveys of consumer adoption and use of low- and zero-carbon technologies

Abstract: This paper presents results from a UK Open University project which surveyed consumers’ reasons for adoption, and non-adoption, of energy efficiency measures and renewable energy systems—collectively called low- and zero-carbon technologies—and their experiences of using these technologies. Data were gathered during 2006 via an online questionnaire with nearly 400 responses, plus 111 in-depth telephone interviews. The respondents were mainly environmentally concerned, ‘green’ consumers and therefore these are purposive rather than representative surveys. The paper outlines results for four energy efficiency measures (loft insulation, condensing boilers, heating controls and energy-efficient lighting) and four household renewables (solar thermal water heating, solar photovoltaics, micro-wind turbines and wood-burning stoves). These green consumers typically adopted these technologies to save energy, money and/or the environment, which many considered they achieved despite rebound effects. The reasons for considering but rejecting these technologies include the familiar price barriers, but there were also other obstacles that varied according to the technology concerned. Nearly a third of the surveyed consumers had adopted household renewables, over half of which were wood stoves and 10% solar thermal water heating systems. Most adopters of renewables had previously installed several energy efficiency measures, but only a fifth of those who seriously considered renewables actually installed a system. This suggests sell energy efficiency first, then renewables. There seems to be considerable interest in household renewables in the UK, especially among older, middle-class green consumers, but so far only relatively few pioneers have managed to overcome the barriers to adoption.

Efficient broadcasting using network coding

Abstract: We consider the problem of broadcasting in an ad hoc wireless network, where all nodes of the network are sources that want to transmit information to all other nodes. Our figure of merit is energy efficiency, a critical design parameter for wireless networks since it directly affects battery life and thus network lifetime. We prove that applying ideas from network coding allows to realize significant benefits in terms of energy efficiency for the problem of broadcasting, and propose very simple algorithms that allow to realize these benefits in practice. In particular, our theoretical analysis shows that network coding improves performance by a constant factor in fixed networks. We calculate this factor exactly for some canonical configurations. We then show that in networks where the topology dynamically changes, for example due to mobility, and where operations are restricted to simple distributed algorithms, network coding can offer improvements of a factor of log n, where n is the number of nodes in the network. We use the insights gained from the theoretical analysis to propose low-complexity distributed algorithms for realistic wireless ad hoc scenarios, discuss a number of practical considerations, and evaluate our algorithms through packet level simulation.

Energy-Efficient Cooperative Communication in a Clustered Wireless Sensor Network

Abstract: In this paper, we consider a clustered wireless sensor network where sensors within each cluster relay data packets to nearby clusters using cooperative communications. We propose a cooperative transmission scheme based on distributed space-time block coding and conduct a systematic analysis on the resulting energy consumption. Compared with existing work, our distinctions are twofold: (1) Only sensors that can correctly decode received packets participate in the cooperative transmission, where the number of cooperating nodes depends on both channel and noise realizations; and (2) we use packet-error-rate-based analysis rather than symbol-error-rate-based analysis. This is more realistic since error detection is usually done at the packet level via, e.g., cyclic-redundancy-check codes. Based on the analysis, we further minimize the overall energy consumption by power allocation between the intracluster and intercluster transmissions. With numerical methods, we investigate how energy consumption is affected by the transmit power allocation, the total number of sensors in a cluster, the end-to-end packet error rate requirement, and the relative magnitudes between the intracluster and intercluster distances. Comparisons with direct (noncooperative) transmission schemes demonstrate the significant energy-saving advantage of the proposed cooperative scheme.

Transcending the replacement paradigm of solid-state lighting.

Abstract: The field of photonics starts with the efficient generation of light. The generation of efficient yet highly controllable light can indeed be accomplished with light-emitting diodes (LEDs), which are, in principle, capable of generating white light with a 20 times greater efficiency than conventional light bulbs. Deployed on a global scale to replace conventional sources, such solid-state light sources will result in enormous benefits that, over a period of 10 years, include (1) gigantic energy savings of 1.9 x 1020 joule, (2) a very substantial reduction in global-warming CO2 emissions, (3) a strong reduction in the emission of pollutants such as acid-rain-causing SO2, mercury (Hg), and uranium (U), and (4) financial savings exceeding a trillion (10(12)) US$. These benefits can be accomplished by the "replacement paradigm" in which conventional light sources are replaced by more energy efficient, more durable, and non-toxic light sources. However, it will be shown that solid-state light sources can go beyond the replacement paradigm, by providing new capabilities including the control of spectrum, color temperature, polarization, temporal modulation, and spatial emission pattern. We will show that such future, "smart" light sources, can harness the huge potential of LEDs by offering multi-dimensional controllability that will enhance the functionality and performance of light sources in a wide range of applications. These applications include optical microscopy, imaging, display technologies, communications, networking, and transportation systems.