Energy efficiency

Policy energy efficiency in the transport sector

by marcucci edoardo

Vertical vegetation design decisions and their impact on energy consumption in subtropical cities

by Yael Stav

Vertical vegetation is vegetation growing on, or adjacent to, the unused sunlit exterior surfaces of buildings in... more Vertical vegetation is vegetation growing on, or adjacent to, the unused sunlit exterior surfaces of buildings in cities. Vertical vegetation can improve the energy efficiency of the building on which it is installed mainly by insulating, shading and transpiring moisture from foliage and substrate. Several design parameters may affect the extent of the vertical vegetation's improvement of energy performance. Examples are choice of vegetation, growing medium geometry, north/south aspect and others. The purpose of this study is to quantitatively map out the contribution of several parameters to energy savings in a subtropical setting. The method is thermal simulation based on EnergyPlus configured to reflect the special characteristics of vertical vegetation. Thermal simulation results show that yearly cooling energy savings can reach 25% with realistic design choices in subtropical environments. The most important parameter is the aspect of walls covered by vegetation. Vertical vegetation covering walls facing north (south for the northern hemisphere) will result in the highest energy savings. In making plant selections, the most significant parameter is Leaf Area Index (LAI). Plants with larger LAI, preferably LAI>4, contribute to greater savings whereas LAI<2 can actually consume energy. Change of growing medium thickness from 6cm to 8cm causes dramatic increase in energy savings from 2% to 18%. It is best to use a growing material with high water retention, due to the importance of evapotranspiration for cooling. Similarly, for increased savings in cooling energy, sufficient irrigation is required. To conclude, the choice of design parameters for vertical vegetation is crucial in making sure that it contributes to energy savings rather than energy consumption. Optimal design decisions can create a dramatic sustainability enhancement for the built environment in subtropical climates.

Energy Efficient Protocols for Wireless Sensor Networks: A Survey and Approach

by B. P. S. Sahoo

Co-authored with Satyajit Rath and Deepak Puthal

Wireless Sensor Networks have limited resources with
traditional data gathering techniques. One of the... more Wireless Sensor Networks have limited resources with
traditional data gathering techniques. One of the limitations of
wireless sensor nodes is its inherent limited energy resource.
Therefore, designing an effective wireless sensor network to
maximizing the lifetime of sensor node in order to minimize
maintenance and maximize overall system performance
becomes important. In this article, we have outlined the
design factors and challenges in sensor networks. Then, we
describe several MAC layer and routing layer protocols
proposed for sensor networks. In this paper, we propose an
adaptive approach to find an optimal routing path from source
to sink when the sensor nodes are deployed randomly
deployed in a restricted service area with single sink. Our
analysis says our approach reduces the message
communication to find a optimal routing path. Hence, the
network consumes less energy and increases the lifetime of
the network.

Zero carbon Britain: An alternative energy strategy

by Jamie Bull

The impact of climate change on electricity demand in the Australian National Electricity Market

by William Paul Bell

Working paper

Energy and Throughput Tradeoff in Temporal Spectrum Sharing

by Sibel Tombaz

Co-authored with Ki Won Sung, Jens Zander
Accepted to Crowncom 2012

It is envisaged that diverse types of short-range wireless systems coexist in shared spectrum in a near future. For... more It is envisaged that diverse types of short-range wireless systems coexist in shared spectrum in a near future. For low-power systems, throughput and energy efficiency are two design objectives that often conflict with each other. In this paper, we investigate the tradeoff between the throughput and the energy efficiency for a data-hungry but battery-driven low power network which opportunistically shares radio spectrum in temporal domain. We provide a mathematical framework that determines the optimum frame lengths for the different objectives, and analyze the tradeoff. To this purpose, we propose an energy consumption model that reflects the characteristics of low-power transceivers including power consumption at the receiver side. Numerical results show that for the considered opportunistic system, the optimum frame length for energy efficiency results in significant loss in throughput, and vice versa. It is also observed this tradeoff highly depends on the parameters of primary traffic. This suggests that the transmission duration of the opportunistic network should be chosen depending on the prime system objective, which can be done by the framework.
proposed by this work.

Cache-tuning-aware scratchpad allocation from binaries

by Daniel Pereira Volpato

The literature on scratchpad memories (SPMs) seems to indicate that the use of dynamic overlaying supersedes static,... more The literature on scratchpad memories (SPMs) seems to indicate that the use of dynamic overlaying supersedes static, non-overlay-based (NOB) allocation. Although overlay-based (OVB) techniques operating at source-level code might benefit from multiple hot spots for higher energy savings, they cannot exploit libraries. When operating on binaries, OVB approaches lead to smaller savings, often require dedicated hardware, and sometimes prevent data allocation. Besides, all saving reports published so far ignore that, in cache-based systems, caches are likely to be optimized prior to SPM allocation. We show experimental evidence that, when handling binaries, NOB memory savings (15% to 33% on average) are as good as or better than OVB's. Since our savings (as opposed to related work) were measured after cache tuning -- when there is less room for optimization, our results encourage the use of simpler NOB methods to build library aware allocators that cannot depend on dedicated hardware. We also show that, given the capacity Ct of the equivalent pretuned cache, the optimal SPM size lies in [Ct/2, Ct] for 85% of the evaluated programs. Finally, we show counter-intuitive evidence that, even for cache-based architectures containing small SPMs, procedures should be preferred for allocation instead of basic blocks.

A Post-compiling Approach that Exploits Code Granularity in Scratchpads to Improve Energy Efficiency

by Daniel Pereira Volpato

Mapping Data and Code into Scratchpads from Relocatable Binaries

by Daniel Pereira Volpato

The Mueller Report: Moving Beyond Sustainability Indicators to Sustainability Action

by Joshua Pearce

Joshua Pearce, Christopher Uhl, Austin Mandryk, Dennis Matalavage, Christie Vischer, Loren Byrne, and Sara Eisenfeld, "The Mueller Report: Moving Beyond Sustainability Indicators to Sustainability Action", The Green Destiny Council of The Pennsylvania State University, Fall 2001.

The assignment that we gave ourselves was: Cut the ecological impact of Mueller Building in half while creating... more The assignment that we gave ourselves was: Cut the ecological impact of Mueller Building in half while creating healthier working conditions for all building occupants. The analysis on the following pages reveals that it is, indeed, possible to reduce significantly Mueller's aggregate impacts in many areas. The majority of environmental improvements that Mueller could make would actually save money! For example, by following the suggestions outlined in the energy portions of this study Mueller building could reap more than $45,000 per year in energy savings alone.

Decentralised reinforcement learning for energy-efficient scheduling in wireless sensor networks

by Mihail Mihaylov

Mihaylov, M., Le Borgne, Y-A., Tuyls, K. and Nowé, A. (2012) ‘Decentralised reinforcement learning for energy-efficient scheduling in wireless sensor networks’, International Journal of Communication Networks and Distributed Systems, Vol. 9, Nos. 3/4, pp.207–224.

We present a self-organising reinforcement learning (RL) approach for scheduling the wake-up cycles of nodes in a... more We present a self-organising reinforcement learning (RL) approach for scheduling the wake-up cycles of nodes in a wireless sensor network. The approach is fully decentralised, and allows sensor nodes to schedule their active periods based only on their interactions with neighbouring nodes. Compared to standard scheduling mechanisms such as SMAC, the benefits of the proposed approach are twofold. First, the nodes do not need to synchronise explicitly, since synchronisation is achieved by the successful exchange of data messages in the data collection process. Second, the learning process allows nodes competing for the radio channel to desynchronise in such a way that radio interferences and therefore packet collisions are significantly reduced. This results in shorter communication schedules, allowing to not only reduce energy consumption by reducing the wake-up cycles of sensor nodes, but also to decrease the data retrieval latency. We implement this RL approach in the OMNET++ sensor network simulator, and illustrate how sensor nodes arranged in line, mesh and grid topologies autonomously uncover schedules that favour the successful delivery of messages along a routing tree while avoiding interferences.

Energy conservation from systematic tire pressure regulation

by Joshua Pearce

Joshua M. Pearce and Jason T. Hanlon, "Energy Conservation From Systematic Tire Pressure Regulation", Energy Policy, 35(4), pp. 2673-2677, 2007

The majority of U.S. drivers do not consistently monitor the tire pressures in their vehicles. The 2000 TREAD Act,... more The majority of U.S. drivers do not consistently monitor the tire pressures in their vehicles. The 2000 TREAD Act, which requires automakers to gradually provide tire pressure monitoring systems for vehicles sold in the U.S. will correct this problem for new vehicles. This law does not impact the problem in previously deployed vehicles, which have a turnover time of 20 years. A solution is provided here to address under-inflated tires on the current 220 million vehicles and the concomitant wasted energy due to increased rolling resistance in the U.S. automobile fleet. This communication reports on a preliminary study of tire pressures in randomly chosen vehicles, which were undergoing oil changes at a combined retail/auto-care facility. The study indicates that substantial benefits would accrue if car care facilities systematically offered complimentary tire pressure checks with oil changes including: increased safety by decreasing all crashes and saving more than 100 lives, reduced petroleum consumption by over a billion gallons/year, which would provide over $4 billion in economic savings for U.S. consumers that could in part be recouped in retail/auto-care facilities, reduce greenhouse gas emissions by 13.5 million tons and automobile pollution and enhance national security.

Interdisciplinary Environmental Education: Communicating and Applying Energy Efficiency for Sustainability

by Joshua Pearce

Joshua Pearce and Chris Russill, "Interdisciplinary Environmental Education: Communicating and Applying Energy Efficiency for Sustainability", Applied Environmental Education and Communication, 4(1), 65-72, 2005.

This paper demonstrates that interdisciplinary alliances on environmental education projects can effectively address... more This paper demonstrates that interdisciplinary alliances on environmental education projects can effectively address the gap between complex environmental problems in the real world and disciplinary curricula in a university. We describe an alliance between an advanced communication course and a general science course wherein we addressed interconnections of energy efficiency, economics, and global climate change with respect to their impact on individuals, local businesses, and society. This project established that an interdisciplinary environmental project focused on local solutions to global problems is both a valuable learning tool for students and an effective method of accelerating the application of appropriate technologies.

"A Content-Centric Architecture for Green Networking in IEEE 802.11 MANETs"

by Marica Amadeo

co-authored with Antonella Molinaro and Giuseppe Ruggeri. Published in First ICST International Conference on Green Communication and Networking (GreenNets’11) , Colmar (France) Ottobre 2011

In this paper we aim to demonstrate that the emerging paradigm of content-centric networking conceived for future... more In this paper we aim to demonstrate that the emerging paradigm of content-centric networking conceived for future Internet architectures can be also beneficial from the energy efficiency point of view.
The reference scenario to prove this statement is a Mobile Ad hoc Network (MANET) characterized by dynamic topology and intermittent connectivity. We design CHANET, a content-centric MANET that relies on a connectionless layer built on top of legacy IEEE 802.11 networks to provide energy-efficient content-based transport functionality without relying on the TCP/IP protocol suite.

Code Transformations for TLB Power Reduction (Journal)

by Reiley Jeyapaul

IJPP 2010

The Translation Look-aside Buffer (TLB) is a very important part in the hardware support for virtual memory management... more The Translation Look-aside Buffer (TLB) is a very important part in the hardware support for virtual memory management implementation of high performance embedded systems. The TLB though small is frequently accessed, and therefore not only consumes significant energy, but also is one of the important thermal hot-spots in the processor. Recently, several circuit and microarchitectural implementations of TLBs have been proposed to reduce TLB power. One simple, yet effective TLB design for power reduction is the Use-Last TLB architecture proposed in IEEE J Solid State Circuits, 1190–1199, (2004). The Use-Last TLB architecture reduces the power consumption when the last page is accessed again. In this work, we develop code transformation techniques to reduce the page switchings in data cache accesses and propose an efficient page-aware code placement technique to enhance the energy reduction capabilities achieved by the Use-Last TLB architecture for instruction cache accesses. Our comprehensive page switch reduction algorithm results in an average of 39% reduction in the data-TLB page switching, and our code placement heuristic
results in an average of 76% reduction in the instrucion-TLB page switchings with negligible impact on the performance on benchmarks from MiBench, Multimedia, DSPStone and BDTI suites. The reduced page switch count through our techniques
achieves an equivalent power savings, above and beyond the reduction achieved by the Use-Last TLB architecture implementation.

Smart cache cleaning: Energy efficient vulnerability reduction in embedded processors

by Reiley Jeyapaul

CASES 2011

Incessant and rapid technology scaling has brought us to a point where todays, and future transistors are susceptible... more Incessant and rapid technology scaling has brought us to a point where todays, and future transistors are susceptible to transient errors induced by energy carrying particles, called soft errors. Within a processor, the sheer size and nature of data in the caches render it most vulnerable to electrical interferences on static data in the cache. Data in the cache is vulnerable to corruption by soft errors, for the time it remains in the cache. Write-through and early-write-back [17] cache configurations reduce the time for vulnerable data in the cache, at the cost of increased memory writes and therefore energy. We propose a smart cache cleaning methodology, that enables copying of only specific vulnerable cache blocks into the memory at chosen times, thereby ensuring data cache protection with minimal memory writes. Our experiments over LINPACK and Livermore benchmarks demonstrate 26% reduced energy-vulnerability product compared to that of hardware cache configurations.

The Multiple Pathways to Industrial Energy Efficiency: A Systems and Value Chain Approach

by Lukas Brun

Energy and Distortion Analysis of Video Compression Schemes for Wireless Video Sensor Networks

by Saeed Ullah

Wireless Video Sensor Networks (WVSNs) - a type of WSNs - comprise of sensor nodes that can capture, process and... more Wireless Video Sensor Networks (WVSNs) - a type of WSNs - comprise of sensor nodes that can capture, process and communicate video frames. The battery powered sensor nodes have limited hardware resources while video processing and communication are resource intensive tasks i.e., require high-end processors, large memory and bandwidth. Video encoding is a popular method used to reduce the communication overhead
but being an inherently complex process it results in higher computational energy-drain on video sensor nodes. This establishes an interesting computation-communication tradeoff for energy efficient video communication (encoding and transmission) in WVSNs. In this paper, we study this computation-communication tradeoff under Intel-imote2 based single-hop and multi-hop video sensor networks testbed by empirically evaluating selected implementations of the MPEG-4 (Part 2) and H.264/AVC encoders. The analysis has been carried out to characterize the performance of encoders in terms of energy efficiency, compression efficiency and video distortion. The experimental results show that in single-hop WVSNs, MPEG-4 is energy efficient over H.264 whilst in multihop WVSNs, H.264 is energy efficient over MPEG-4.

Distributed, Energy-Efficient, Fault Tolerant, Weighted Clustering

by Javad Memariani

Energy Efficiency in Building Installations using Thermal Insulating Materials in BRAZIL NORTHEAST

by Miguel Melo

Miguel O. Melo (PhD)
Luiz Bueno da Silva (PhD)
Antonio S. Coutinho (PhD)
Normando Perazzo (PhD)
Vivian Sousa

Federal University of Paraiba
Joao Pessoa – PB, Brazil, 58051-970
mobcmelo@ct.ufpb.br

ENERGY and BUILDING Journal

ABSTRACT
This paper presents a solution for improvement of energy efficiency in buildings by using thermal... more ABSTRACT
This paper presents a solution for improvement of energy efficiency in buildings by using thermal insulation materials. The application was tested in areas of northeast Brazil where the average temperature reaches 34°C. The research considered building materials from the region such as: (a) gypsum, that is abundant in nature and found in several deposits in Brazil and it is absorbent of water; (b) vermiculite, a mineral composed of hydrated silicates of aluminum and magnesium; (c) EVA, an ethylene-vinyl acetate produced in large quantities as residue from expanded sheet cuttings in the shoe industry. The thermal conductivity of each material was measured but the comparison of the thermal behaviour of the two walls is based on calculation only. The application of these materials in plates coated with a layer of air showed, compared to conventional walls, 38% reduction in heat load per square meter when using vermiculite-composed plaster and 41% reduction when using gypsum or EVA composition.

Keywords: Energy efficiency in building; Thermal insulating; Thermal non-conventional materials