Minimize Energy Use Research Articles

Estimating the impacts of climate change and urbanization on building performance

Over the past 15 years, much scientific work has been published on the potential human impacts on climates. For their Third Assessment Report in 2001, the United Nations International Programme on Climate Change developed a set of economic development scenarios, which were then run with the four major general circulation models (GCM) to estimate the anthropogenesis-forced climate change. These GCMs produce worldwide grids of predicted monthly temperature, cloud, and precipitation deviations from the period 1961–1990. As this period is the same used for several major typical meteorological year data sets, these typical data sets can be used as a starting point for modifying weather files to represent predicted climate change. Over the past 50 years, studies of urban heat islands (UHI) or urbanization have provided detailed measurements of the diurnal and seasonal patterns and differences between urban and rural climatic conditions. While heat islands have been shown to be a function of both population and microclimatic and site conditions, they can be generalized into a predictable diurnal and seasonal pattern. Although the scientific literature is full of studies looking at the impact of climate change driven by human activity, there is very little research on the impact of climate change or urban heat islands on building operation and performance across the world. This article presents the methodology used to create weather files which represent climate change scenarios in 2100 and heat island impacts today. For this study, typical and extreme meteorological weather data were created for 25 locations (20 climate regions) to represent a range of predicted climate change and heat island scenarios for building simulation. Then prototypical small office buildings were created to represent typical, good, and low-energy practices around the world. The simulation results for these prototype buildings provide a snapshot view of the potential impacts of the set of climate scenarios on building performance. This includes location-specific building response, such as fuel swapping as heating and cooling ratios change, impacts on environmental emissions, impacts on equipment use and longevity comfort issues, and how low-energy building design incorporating renewables can significantly mitigate any potential climate variation. In this article, examples of how heat island and climate change scenarios affect diurnal patterns are presented as well as the annual energy performance impacts for three of the 25 locations. In cold climates, the net change to annual energy use due to climate change will be positive – reducing energy use on the order of 10% or more. For tropical climates, buildings will see an increase in overall energy use due to climate change, with some months increasing by more than 20% from current conditions. Temperate, mid-latitude climates will see the largest change but it will be a swapping from heating to cooling, including a significant reduction of 25% or more in heating energy and up to 15% increase in cooling energy. Buildings which are built to current standards such as ASHRAE/IESNA Standard 90.1-2004 will still see significant increases in energy demand over the twenty-first century. Low-energy buildings designed to minimize energy use will be the least affected, with impacts in the range of 5–10%. Unless the way buildings are designed, built, and operated changes significantly over the next decades, buildings will see substantial operating cost increases and possible disruptions in an already strained energy supply system.

Optimal Swimming Speed in Head Currents and Effects on Distance Movement of Winter-Migrating Fish

Migration is a commonly described phenomenon in nature that is often caused by spatial and temporal differences in habitat quality. However, as migration requires energy, the timing of migration may depend not only on differences in habitat quality, but also on temporal variation in migration costs. Such variation can, for instance, arise from changes in wind or current velocity for migrating birds and fish, respectively. Whereas behavioural responses of birds to such changing environmental conditions have been relatively well described, this is not the case for fish, although fish migrations are both ecologically and economically important. We here use passive and active telemetry to study how winter migrating roach regulate swimming speed and distance travelled per day in response to variations in head current velocity. Furthermore, we provide theoretical predictions on optimal swimming speeds in head currents and relate these to our empirical results. We show that fish migrate farther on days with low current velocity, but travel at a greater ground speed on days with high current velocity. The latter result agrees with our predictions on optimal swimming speed in head currents, but disagrees with previously reported predictions suggesting that fish ground speed should not change with head current velocity. We suggest that this difference is due to different assumptions on fish swimming energetics. We conclude that fish are able to adjust both swimming speed and timing of swimming activity during migration to changes in head current velocity in order to minimize energy use.

Energy storage device as a part of electric energy production system based on renewable energy sources

This work deals whit an energy storage device as a part of electric energy production system based on renewable energy sources. The system supplies given load with known load diagram. Operational diagrams of individual units in the system are determined in an optimization procedure. The optimization goal is to supply given load with minimal use of conventional energy delivered from electric grid. Optimization is performed by a stochastic search algorithm called Differential Evolution [1] for the system consisting of a solar power plant, wind turbine unit, flow battery (VRB unit), load and the electric grid. Individual elements are described in [2]-[7]. The optimization input data are given weather forecasting and forecasted load diagram.

Key-drivers in hotel and environmental management: a comparative analysis in Malaysia

In tourism, the environment is a core business product. Since hotels occupy a central place in the tourism industry and its development does impact upon the environment considerably, it is believed that hotels should be more proactive in their managerial response concerning environmental performance. Using interview data, this study compares the environmental management practices among hotels operating in Penang and Langkawi, Malaysia. The results have shown that although hotel companies in both destinations are concerned with environmental management issues, many are not proactive enough in their responses and prefer to only take management initiatives that have considerable financial benefits for their business. Focus has been mainly on cost-cutting management measures such as minimising energy use and water conservation as this contributes directly toward a hotel|s profitability. In both cases, business refuses to take sole ownership on environmental management. Instead, the government and society are expected to play a leading role before business can be expected to emulate.

무선 센서 네트워크에서 신뢰성 있는 데이터 전송과 혼잡 제어를 위한 프로토콜

Generally, huge amounts of data traffic are generated by using broadcasting method to deliver sensing data to a sink node reliably so that it makes a severe network saturation problem resulting in unreliable data transfer. In order to handle this problem, a new congestion control protocol is required for supporting reliable data transfer, minimal use of energy and network resources at the same time in wireless sensor networks. In this paper, it proposes a Protocol to guarantee both a reliable transfer in data accuracy and minimum consumption of energy waste by using Hop-by-Hop sequence number and DSbACK(Delayed and Selective ACK Buffer Condition) scheme. In addition, it proves that reliability and energy efficiency are enhanced by the proposed method with the simulation results performed on TinyOS platform which is a component based built-in OS announced by UC Berkely with the performance comparison of other existing methods.

Effect of Pre-Cooling on Natural Ventilation of Buildings with Multiple Stacks

Chenvidyakarn et al (2004a) investigated the natural ventilation of an occupied open-plan space, which was connected to an exterior through two stacks and a low-level vent. Occupants located at an intermediate level between the stacks and the low-level vent acted as a uniform source of heat, providing buoyancy to drive the ventilation. Their work showed that these conditions could produce up to three steady state ventilation regimes. In the first regime, the bottom opening and the shorter stack acted as inflow vents, while the taller stack acted as an outflow vent. In the second regime, the bottom opening acted as an inflow vent, while both stacks acted as outflow vents. In the third regime, the bottom opening and the taller stack acted as inflow vents, while the shorter stack acted as an outflow vent. The present work considers the situation in which a passive cooling system, such as thermal mass, is connected to the low-level vent to pre-cool supply air, as may be required in low-energy buildings operating in summer or warm climates. Using a combination of laboratory experiments and a theoretical model, the paper explores how the pre-cooling affects the ventilation and steady state temperature in the space under the three ventilation regimes. The study shows that sufficiently large pre-cooling can stall the inflow through the bottom vent in the first and third regimes, or the outflow through the shorter stack in the second regime. Depending on the ventilation regime and resultant flow rate, an increase in the pre-cooling can lead to either a decrease or an increase in the temperature in the occupied zone. To achieve desired ranges of temperatures and ventilation rates while minimising energy use, an appropriate range of pre-cooling is required. The paper shows how to determine such an appropriate range of pre-cooling for a given ventilation regime.

Treatment of Dilute Wastewaters Using a Novel Submerged Anaerobic Membrane Bioreactor

Three 3L laboratory scale submerged anaerobic membrane bioreactors (SAMBRs) with in situ membrane cleaning due to the bubbling of recycled biogas underneath them were studied for their ability to treat dilute wastewaters. Both Mitsubishi Rayon hollow-fiber and Kubota flat sheet membranes made of polyethylene with a pore size of 0.4μm were used in this study, and the effect of different substrates (460mg∕L of glucose or synthetic) on chemical oxygen demand (COD) performance in the SAMBR was investigated. It was found that both membranes resulted in similar COD removals (>90% soluble COD at a hydraulic retention time of 3h), but that the transmembrane pressure across the hollow fiber membranes was higher under similar conditions. Molecular weight analysis of the feed, reactor contents, effluent, and extracellular polymers using high pressure liquid chromatography showed that the membrane filtered out most of the high MW soluble organics, resulting in high COD removals. The experimental results from the SAMBR show the potential benefits of using this novel reactor design in a biological wastewater treatment process to minimize energy use and sludge production.

Native or Raw Starch Digestion: A Key Step in Energy Efficient Biorefining of Grain

Improved molecular disassembly and depolymerization of grain starch to glucose are key to reducing energy use in the bioconversion of glucose to chemicals, ingredients, and fuels. In fuel ethanol production, these biorefining steps use 10-20% of the energy content of the fuel ethanol. The need to minimize energy use and to raise the net yield of energy can be met by replacing high-temperature, liquid-phase, enzymatic digestion with low temperature, solid-phase, enzymatic digestion. Also called cold hydrolysis, the approach is a step toward a "green" method for the production of fuel ethanol. There has been substantial prior and increased recent interest in this approach that is presented in this first review of the subject. We include incentives, developmental research, fundamental factors of raw starch digestion, and novel approaches in enzymology and processing. The discussion draws on resources found in enzymology, engineering, plant physiology, cereal chemistry, and kinetics.

Shortest-path algorithms for real-time scheduling of FIFO tasks with minimal energy use

We present an algorithm for scheduling a set of nonrecurrent tasks (or jobs) with FIFO real-time constraints so as to minimize the total energy consumed when the tasks are performed on a dynamically variable voltage processor. Our algorithm runs in linear time and thus, in this case, is an improvement over the classical algorithm of Yao et al. It was inspired by considering the problem as a shortest-path problem. We also propose an algorithm to deal with the case where the processor has only a limited number of clock frequencies. This algorithm gives the optimum schedule with the minimum number of speed changes, which is important when the speed switching overhead cannot be neglected. All our algorithms are linear in the number of tasks if the arrivals and deadlines are sorted and otherwise need O ( N log N ) time. These complexities are shown to be the best possible. Finally, we extend our results to fluid tasks and to nonconvex cost functions.

Fiber-type Composition of the Human Jaw Muscles—(Part 1) Origin and Functional Significance of Fiber-type Diversity

This is the first of two articles on the fiber-type composition of the human jaw muscles. The present article discusses the origin of fiber-type composition and its consequences. This discussion is presented in the context of the requirements for functional performance and adaptation that are imposed upon the jaw muscles. The human masticatory system must perform a much larger variety of motor tasks than the average limb or trunk motor system. An important advantage of fiber-type diversity, as observed in the jaw muscles, is that it optimizes the required function while minimizing energy use. The capacity for adaptation is reflected by the large variability in fiber-type composition among muscle groups, individual muscles, and muscle regions. Adaptive changes are related, for example, to the amount of daily activation and/or stretch of fibers. Generally, the number of slow, fatigue-resistant fibers is relatively large in muscles and muscle regions that are subjected to considerable activity and/or stretch.

PACE: a new approach to dynamic voltage scaling

By dynamically varying CPU speed and voltage, it is possible to save significant amounts of energy while still meeting prespecified soft or hard deadlines for tasks; numerous algorithms have been published with this goal. We show that it is possible to modify any voltage scaling algorithm to minimize energy use without affecting perceived performance and present a formula to do so optimally. Because this formula specifies increased speed as the task progresses, we call this approach PACE (Processor Acceleration to Conserve Energy). This optimal formula depends on the probability distribution of the task's work requirement and requires that the speed be varied continuously. We therefore present methods for estimating the task work distribution and evaluate how effective they are on a variety of real workloads. We also show how to approximate the optimal continuous schedule with one that changes speed a limited number of times. Using these methods, we find we can apply PACE practically and efficiently. Furthermore, PACE is extremely effective. Simulations using real workloads and the standard model for energy consumption as a function of voltage show that PACE can reduce the CPU energy consumption of existing algorithms by up to 49.5 percent, with an average of 20.6 percent, without any effect on perceived performance. The consequent PACE-modified algorithms reduce CPU energy consumption by an average of 65.4 percent relative to no dynamic voltage scaling, as opposed to only 54.3 percent without PACE.

PERFORMANCE STUDY OF AN ENERGY-EFFICIENT DISPLAY CASE REFRIGERATOR

Growing concerns over global warming due to the greenhouse effect from industrial emissions have pushed the appliance industry in Taiwan to further improve the energy efficiency of its products. The display case refrigerator is a major supermarket appliance and its life expectancy could be as long as 10 years. In response to ever-more stringent regulations on energy efficiency, a prototype has been designed for minimizing energy use. Options such as insulation improvements using vacuum insulation panels (VIPs) and vacuum glazing (VG) were examined in a display case refrigerator by measuring heat loss. Results show that energy efficiency can be improved up to 30% by simultaneously mounting the VG and VIPs on the display case refrigerator. Additionally, the frost or sweat was eliminated for the energy-efficient display case refrigerator.

Representative building design and internal load patterns for modelling energy use in residential buildings in Hong Kong

Based on the data collected in recent surveys, models have been established to represent the energy characteristics of living and dining rooms and bedrooms in typical residential buildings in Hong Kong, in respect of the layout and construction; the density and pattern of occupation; the power intensities and operating patterns of lighting and appliances; and air-conditioner operation patterns. With the help of computer simulation, the impacts of varying these characteristics on the annual space cooling load have been evaluated, which allowed representative internal load patterns for residential units to be defined. These are essential data for predicting energy use in residential buildings, which, in turn, is an indispensable part of studies on ways to assess and minimise energy use in such buildings. This paper presents the building model and the internal load and air-conditioner operation patterns established in the study.

My sixty years in applied algology

I am greatly honored to present this Keynote address. My focus, even after sixty years, continues to be on the future of phycology, even though I now present mainly from the past. I am delighted to see biological and physical scientists and engineers coming together in the field of Applied Phycology. Our working together will result in many benefits for mankind. There is no doubt that Applied Phycology has a great future because it has the potential for more efficient use of solar energy than conventional agriculture, and because it is poised to reach still unimagined goals through both genetic and ecological engineering. As an engineer I have focused mainly on large algal mass culture systems and the efficient use of solar energy in wastewater treatment (Oswald, 1962, 1963). But now I can envision such future triumphs as the introduction of genes for sulfur amino acids into the presently deficient Spirulina genome. I am fascinated by Dr Bailey Green’s crusade to minimize energy use and greenhouse gas emissions using algae-based sewage treatment (Green, 1998), by Dr Joseph Weissman’s commercial production of shellfish fed mass cultured algae, and by Dr John Benemann’s vision of achieving very high productivities through physiological and genetic manipulations of the photosynthetic apparatus (Benemann, 1990), to mention just three examples currently underway by former students and colleagues. All of these and many more advances have resulted from combining biological and engineering knowledge. As a young civil engineer I was greatly surprised when I learned that the growth of one unit dry weight of algae is accompanied by release of over one and one half times as much dissolved molecular oxygen, a process powered by virtually free solar energy. How to use this low cost dissolved O2 in wastewater treatment and life support systems has consumed much of my, and many of my students’, ingenuity during the past half century. Over these years my main area of research has been the design and operation of largescale cultures of microalgae that grow commensally with bacteria in rich organic media such as domestic sewage or some industrial wastes. Not only is solar energy and the resulting ‘photosynthetic oxygenation’ nearly free, but also the nutrients in the wastewaters are free and often ideally suited for algal mass cultures. In these waste treatment ponds we only exert minimal control over the algal species that grow, but we can impose some limits through pond operations such as residence time, depth and mixing. For reasons best known to the algae themselves, we often find species of Chlorella, Scenedesmus, and Micractinium, although species of Euglena, Chlamydomonas and Oscillatoria may occur in ponds with excessive loadings or long residence times. In these wastewater-fertilized systems the role of algae is primarily for production of O2 to support bacterial growth, although nutrient uptake, adsorption of heavy metals and, indirectly, disinfection are also important functions of the algae in these systems. In the following I highlight some of the benefits of growing microalgae in wastewaters (Oswald 1978).

Energy-saving mechanisms in muscle: the minimization strategy.

Many mechanisms reduce the cost of muscle activity. Here, we describe a set of specializations that reduce the cost of contraction in the high-frequency twitches that are used by a wide variety of animals for either sound production or flight. Minimizing the cost of these contractions means that cellular ATP production can meet ATP demand and sustain the high contractile rate. Two classes of specialization are found that minimize the contractile cost. The first class reduces the muscle work required per contraction. Light appendages such as rattles, insect limbs and membranous wings that require little work for movement are used in high-frequency contractions. The second set of specializations involves processes that minimize energy use. High-frequency muscles tend to have a lower cross-bridge content, fewer attached cross-bridges and shorter length changes per contraction. The result is low muscle-specific forces (stress), small length changes (strain) and rapid contraction times that suggest that these muscles push the lower limit of contractile function. The consequence of function at this lower extreme of contraction is to minimize the contractile cost of high-frequency muscles. Thus, specializations that permit rapid contractions at a low rate of ATP use per twitch are the basis of a minimization strategy for energy saving in muscles contracting at high frequency.

Daylighting as a passive solar design strategy in tropical buildings: a case study of Malaysia

The use of daylighting in buildings and architecture is not new. Natural lighting became out of vogue due to the availability of cheap electricity, the predictability and the ability to control illumination levels due to artificial lighting. However, the alarm over rapid depletion of energy resources and the environmental effects of their applications have led designers to reuse daylighting strategies in buildings in order to minimise energy use for lighting and air conditioning as a result of heat gains from the daylight sources and the electrical fixtures. This paper describes a study on the savings achieved by using daylight in passive solar design of buildings and, in this case, the size of windows. Simulated exterior illuminance levels based on long term measured solar irradiation and cloud cover data were used to estimate interior illumination on normal working planes using simple building configurations. Illumination on these planes decreases the need for artificial lighting, thus energy can be saved. A simple algorithm was then used to calculate the overall cooling load to ascertain that the daylighting strategies used do not invoke an increase in thermal gains through walls and glazings. The findings from this study show that at least 10% savings can be produced from simple daylighting strategies.

Energy efficiency and building construction in India

The energy conservation has become an important issue in building design, it is logical to apply the principle of energy costing to building projects, and to look for ways to minimize the total energy consumed during their lifetime. Even though the total quantity of energy consumed in a building during its lifetime may be many times than that consumed in its construction, there are number of reasons why the energy use in the construction process, and in particular in the building materials used, should be treated as a matter of importance in looking for ways to minimize energy use in the built environment as a whole. In this paper the energy costs of alternative construction techniques using an optimization framework are assessed and compared. The techniques of construction evaluated in this paper are commonly used pucca techniques as well as low-cost construction techniques. Energy consumption and resource requirements due to the use of alternative techniques of construction for a representative room of size 3.5 m×3.5 m×3.14 m are evaluated. An assessment of the magnitude of energy consumption, if housing shortages have to be met, shows that a huge amount of energy would be consumed in housing sector alone. The associated levels of carbon dioxide emissions associated with this construction would also be prohibitively high. Finally the paper concludes with recommendations for structural changes in the energy and construction policy in India to minimize energy consumption in building construction.

DISTRIBUTED INSTRUMENTATION FOR OPTIMUM CONTROL OF VARIABLE SPEED ELECTRIC PUMPING PLANTS WITH CENTER PIVOTS

Pressure measurements at critical locations in the irrigation system (distributed pressure measurements) wereused to optimize operation of an electric pumping plant equipped for variable speed operation. Operation of the pumpingplant was optimized in terms of providing adequate irrigation coverage with minimum energy use. The pumping plantsupplied water to a single center pivot on undulating topography. The center pivot was equipped with a supervisorycontrol and data acquisition system for variable rate water application. Electrical demand of the irrigation system wasevaluated under four variable speed pumping control schemes. Disregarding inefficiencies of the variable frequencymotor controller, distributed pressure measurement resulted in 15.8 and 20.2% energy savings compared to constantspeed pumping for uniform and variable rate irrigation, respectively. When the efficiency of the variable frequency motorcontroller is accounted for, distributed pressure measurement resulted in 7.5 and 12.4% energy savings compared toconventional constant speed pumping for uniform and variable rate irrigation, respectively. Use of distributed pressuremeasurements to control the variable speed pumping plant was highly effective in minimizing energy use whilemaintaining the pressure required throughout the irrigation system.

From equipment to infrastructure: community energy management and greenhouse gas emission reduction

Community energy management (CEM) (also called community energy planning) combines planning concepts - neo-traditional design, complete communities, green cities - with energy management concepts - energy cascading, demand-side management, integrated resource planning. It can be applied at the level of neighborhoods, cities and even small regions in order to exploit the synergies between urban design objectives for livable cities and energy management objectives of minimizing energy use and its associated environmental effects for a given standard of living. CEM encompasses (i) land use planning, (ii) transportation management, (iii) site design, and (iv) local energy supply and delivery planning. While traditional energy management focuses on energy using equipment and buildings, CEM also considers the urban land use and infrastructure level. This study applies CEM to four representative communities in British Columbia, Canada, over the period 1995 to 2010, and compares the results to a business-as-usual (BAU) scenario. The aggregate effect is a decrease in energy service costs and energy consumption of 15–30%, and in air emissions (CO 2 and NOx) of 30–45%. The methodology and results, with respect to one aspect of CEM - land use planning - are extrapolated to the provincial level in order to estimate total CO 2 emission reduction portential. CO 2 emissions are reduced by 17% from BAU. Additional approximate calculations (restricted to land use planning) suggest that on a global scale CEM can be an important element in the greenhouse gas emission reduction strategy, especially given the dramatic urban growth anticipated in developing countries in the coming decades. Implementation of CEM requires an array of policy initiatives from governments at all levels, as the following examples illustrate. National and provincial (state) governments can (i) change the legislation governing regional and muncipal land use planning, (ii) tie infrastructure grants to CEM type municipal investments, and (iii) provide information support and fiscal incentives for developers. Regional and municipal governments can (i) change zoning objectives, (ii) encourage specific types of developments through development charges and tax incentives to developers, and (iii) work with energy and other utilities to encourage particular energy forms and delivery systems.

Physical quality of pelleted animal feed. 2. contribution of processes and its conditions

The effects of changes in process parameters and their effect on pellet quality in terms of hardness and durability are discussed. The pelleting process in this respect is the combination of conditioning, pelleting and cooling. The parameters discussed with respect to the conditioning process are process variables such as steam and water and system parameters such as residence time and pressure. Parameters during the pelleting process that can be adjusted or influence pelleting properties of a feed mash include layout (e.g. flat-bed vs. ring-die pellet press) and dimensions, roller and die assembly and die velocity of the pellet press. The effect of the changes in one or more parameters and its effect on pellet quality (durability and hardness) is however often a matter of the judgement and experience of the operator. For instance, a certain increase in the amount of steam added to a feed mash generally improves pellet hardness and durability. Increasing the amount of dissipated power in the feed mash, generally has a similar favourable effect on pellet quality. The extent to which pellet hardness and durability rise is however dependent on feed formulation and other parameters as temperature of the feed mash and cooling air characteristics. The latter parameters can be measured but their relation to the pelleting process is often not clear. Pellet quality, as affected by cooling, is mainly determined by the bed-height of the pellets in the cooler, pellet-size, air-flow and air-characteristics during the cooling period. The use of modern conditioning systems to operate at a wide range of processing and system variables means that pellet quality is dictated more by equipment than by diet formulation. However, use of such conditioning systems must always be justifiable in terms of cost and pellet quality, rather than the dictates of fashion. It is concluded that the amount of steam is a more decisive factor than steam pressure. In addition, it seems that the individual steam supply of a factory has a larger influence on the measured pellet hardness and durability than would be expected from theoretical relationships concerning steam in an ideal situation. Although water has binding properties as well, it is concluded that steam is far superior to water in producing good quality pellets. The additional heat included in the meal permits changes in physico-chemical properties which lead to more durable and hard pellets. Equipment which incorporates some form of hold-time enhances the possibility to incorporate more liquids, without detrimental effects on pellet quality. The use of pressure to alter physico-chemical properties of the feed in combination with water and heat, and the use of pressure to pre-densify the feed mash prior to pelleting seems to be important in obtaining a good quality pellet. Pelleting is not the sum of conditioning, pelleting and cooling steps, but should be considered as an integral system which performance is dependent on interrelations between the three unit operations: conditioning, pelleting and cooling. However, these interrelations with respect to the different formulations used, are still poorly understood. The use of decision support systems and process optimization procedures may nowadays greatly enhance the opportunity to obtain the best possible quality of pelleted feeds with minimal use of labour and energy for a given feed formulation.