Energy-saving Options Research Articles

Hygrothermal study of dwelling submitted to passive cooling

A significant portion of energy consumed in buildings is due to energy usage by heating, ventilation, and air conditioning systems. Free cooling is a good option for energy savings in the systems. In recent years, scientists, engineers, and architects designed successful and innovative buildings which use passive cooling techniques, such as natural ventilation. The house studied in the present work, is a pilot project undertaken jointly by the Centre for Development of Renewable Energies (CDER) and the National Centre for Studies and Research of the integrated building (CNERIB) in the framework of the MED-ENEC project (Mediterranean Energy Efficiency in Construction structure). The house under consideration has a surface area of 65 m2 and is located in the region of Algiers which characterized by a Mediterranean climate with relatively mild winters and a hot and humid summer. The aim of this work is to study the thermal comfort inside the house in summer without air conditioning systems, only ventilation is considered. The aim of this work is to study the effect of natural ventilation on both thermal and hygrometric comfort inside the house during the summer period. Numerical simulation is made using the TRNSYS software and the results obtained are in good agreement with measured values. The prototype home is designed in a way that natural ventilation allows thermal comfort which induced energy saving from air conditioning. The mean temperature measured in the interior of the house is 26?C. The relative humidity reaches about 70% in August. Thermal comfort is related to relative humidity that are the essential parameters of the feeling of comfort. Humidity is an important parameter in thermal comfort, it is why we can conclude that we have reached a relatively good hygrothermal comfort.

An Improved System for Utilizing Low-Temperature Waste Heat of Flue Gas from Coal-Fired Power Plants

In this paper, an improved system to efficiently utilize the low-temperature waste heat from the flue gas of coal-fired power plants is proposed based on heat cascade theory. The essence of the proposed system is that the waste heat of exhausted flue gas is not only used to preheat air for assisting coal combustion as usual but also to heat up feedwater and for low-pressure steam extraction. Air preheating is performed by both the exhaust flue gas in the boiler island and the low-pressure steam extraction in the turbine island; thereby part of the flue gas heat originally exchanged in the air preheater can be saved and introduced to heat the feedwater and the high-temperature condensed water. Consequently, part of the high-pressure steam is saved for further expansion in the steam turbine, which results in additional net power output. Based on the design data of a typical 1000 MW ultra-supercritical coal-fired power plant in China, an in-depth analysis of the energy-saving characteristics of the improved waste heat utilization system (WHUS) and the conventional WHUS is conducted. When the improved WHUS is adopted in a typical 1000 MW unit, net power output increases by 19.51 MW, exergy efficiency improves to 45.46%, and net annual revenue reaches USD 4.741 million while for the conventional WHUS, these performance parameters are 5.83 MW, 44.80% and USD 1.244 million, respectively. The research described in this paper provides a feasible energy-saving option for coal-fired power plants.

Chemical engineering systems modeling and efficiency analysis of heat and mass exchange

The object of research is the chemical engineering system and the heat-mass exchange processes taking place in it. In engineering practice, systems are represented by process flow diagrams. The lack of standardization in the graphical representation of engineering systems does not allow creating a general logic for reading the graphic information and then processing it with the software for analyzing the energy efficiency of the chemical engineering system. The rules for creating flowcharts, symbols for devices, and the chemical engineering system representation technique are developed, allowing any engineering system to be transformed into its topological representation. To combine the two branches of different networks and organize the heat and mass exchange processes in the system are elements intended for heat and energy exchange between networks with streams pair interaction. Mathematical models of heat and mass exchange networks for chemical industry have been developed, and energy efficiency and mass transfer efficiency criteria have been introduced. This allows to: construct a software environment that generates a system model based on its topological representation; analyze various options for implementing the process flow diagram for finished products production; synthesize the optimal, energy-saving production option. A numerical experiment was performed using a modeling software developed by the German company NETWORK SOLUTION DEVELOPMENT CO and transferred for testing. The model adequacy to the real engineering system approves the comparison of the model parameters and the parameters of the design regime of the urea production synthesis unit. The error in determining the mass flow rates doesn’t not exceed 2.4 % on branches, and the temperatures values at the nodes are strictly correspond to the technological regulations. Preliminary analysis indicates the possibility of improving the energy efficiency of production due to the integration of heat streams within the production cycle and the structural and parametric optimization of the engineering system.

Modelling and testing a passive night-sky radiation system

The as-built and tested passive night-sky radiation cooling/heating system considered in this investigation consists of a radiation panel, a cold water storage tank, a hot water storage tank, a room and the interconnecting pipework. The stored cold water can be used to cool a room during the day, particularly in summer. A theoretical time-dependent thermal performance model was also developed and compared with the experimental results and it is shown that the theoretical simulation model captures the experimental system performance to within a reasonable degree of accuracy. A natural circulation experimental set-up was constructed and subsequently used to show that under local (Stellenbosch, South Africa) conditions the typical heat-removal rate from the water in the tank is 55 W/m2 of radiating panel during the night; during the day the water in the hot water-storage tank was heated from 24 °C to 62 °C at a rate of 96 W/m2. The system was also able to cool the room at a rate of 120 W/m3. The results thus confirmed that it is entirely plausible to design an entirely passive system, that is, without the use of any moving mechanical equipment such as pumps and active controls, for both room-cooling and water-heating. It is thus concluded that a passive night-sky radiation cooling/heating system is a viable energy-saving option and that the theoretical simulation, as presented, can be used with confidence as an energy-saving system design and evaluation tool. Keywords: passive cooling and heating, buoyancy-driven fluid flow, theoretical simulation, experimental verification Highlights:Passively driven renewable energy heating and cooling systems are considered.Time-dependent mathematical simulation model is presented.Experimental buoyancy-driven heating and cooling system built and tested.Experimental results demonstrate the applicability of the theoretical simulation model.Saving and evaluation design tool.

Thermal performance of a room with a double glazing window using glazing available in Mexican market

A thermal evaluation of a four configurations of double glass window (DGW) coupling to a room is presented. The DGW consists of two vertical semitransparent walls separated by a 12mm air gap. The effect of varying the ambient temperature and the incident solar radiation in the warm climate conditions in México is analyzed. Numerical simulations were conducted for four configurations; Case 1: clear glass+air gap+clear glass (Reference); Case 2: clear glass+air gap+absorbent glass; Case 3: clear glass+air gap+Low-e glass; and Case 4: clear glass+air gap+reflective glass. Optical transmittance and specular reflectance were measured individually and in one sample piece for each case. The results showed that Case 4 reduces the heat flux to the indoors by up to 73%, with respect to Case 1. Moreover, Cases 2 and 3 had a similar behavior, obtaining a reduction of indoor heat flow close to 33.5% with respect to Case 1. Case 4 is the best option for energy savings in a warm climate, where it is possible to save up to $20.29 USD per kWh per year, in comparison to Case 1. In addition, the payback period for Case 4 is 3.7years. Therefore, the use of reflective double pane window is highly recommended in Mexican warm climates.

Emissions inventory and scenario analyses of air pollutants in Guangdong Province, China

Air pollution, causing significantly adverse health impacts and severe environmental problems, has raised great concerns in China in the past few decades. Guangdong Province faces major challenges to address the regional air pollution problem due to the lack of an emissions inventory. To fill this gap, an emissions inventory of primary fine particles (PM2.5) is compiled for the year 2012, and the key precursors (sulfur dioxide, nitrogen oxides) are identified. Furthermore, policy packages are simulated during the period of 2012‒2030 to investigate the potential mitigation effect. The results show that in 2012, SO2, NOx, and PM2.5 emissions in Guangdong Province were as high as (951.7, 1363.6, and 294.9) kt, respectively. Industrial production processes are the largest source of SO2 and PM2.5 emissions, and transport is the top contributor of NOx emissions. Both the baseline scenario and policy scenario are constructed based on projected energy growth and policy designs. Under the baseline scenario, SO2, NOx, and PM2.5 emissions will almost double in 2030 without proper emissions control policies. The suggested policies are categorized into end-of- pipe control in power plants (ECP), end-of-pipe control in industrial processes (ECI), fuel improvement (FI), energy efficiency improvement (EEI), substitution-pattern development (SPD), and energy saving options (ESO). With the implementation of all these policies, SO2, NOx, and PM2.5 emissions are projected to drop to (303.1, 585.4, and 102.4) kt, respectively, in 2030. This inventory and simulated results will provide deeper insights for policy makers to understand the present situation and the evolution of key emissions in Guangdong Province.

Energy efficiency improvement opportunities and associated greenhouse gas abatement costs for the residential sector

Despite improvements, the residential sector is one of most energy-intensive sectors in the world and is the third largest consumer of energy across Canada, and in Alberta in particular. This study investigates opportunities to improve energy efficiency and reduce greenhouse gas emissions (GHG) in the residential sector. A case study for Alberta is conducted. Energy modeling and scenario analyses are used to project future energy savings and greenhouse gas mitigation potential in the residential sector. Seventeen energy-saving options are identified in different residential subsectors, including space heating and cooling, water heating, appliances, and lighting. The long-term impacts (i.e., from 2013 to 2050) of these technologies in terms of energy savings and greenhouse gas mitigation potential are assessed using the Long-range Energy Alternative Planning model. For the evaluated options, more than 80% of GHG mitigation is achievable with negative GHG abatement cost. A GHG abatement cost curve is developed to assess the economic performance of various options. The results of the cost curve indicate that efficient lighting, efficient furnaces, and high efficiency appliances are the three areas in which the most GHG mitigation can be achieved at the lowest cost. The results provide invaluable insights to policy makers.

Households transport-home energy conservation strategies in response to energy price policies: A stated adaptation experiment based on portfolio choices and cross effects designs

abstractThis article explores consumer investment choice in long-term energy conservation technology and assesses trade-offs in energy saving behaviour between the housing and transportation domains. The long-term energy conservation choice problem is conceptualized as a portfolio choice problem. Consequently, to measure trade-offs between investments in housing and transport options, a cross effects choice design is developed in which respondents were shown one or more alternate ways to reduce their current energy consumption: (1) investing in new technology in the house, such as solar panels; (2) exchanging the current car for a more energy efficient car; (3) buying a new energy-efficient car, such as EV or solar car; (4) moving house to reduce current travel distances. To help respondents linking these options to their current energy consumption, a new Web-based survey system (SINA) to implement and administer stated adaptation experiments was developed. The system was used to collect two sets of data. First, data about out-of-home and in-home energy consumption, together with detailed time use data, was collected. Second, using a cross effects design, respondents were asked to select a portfolio of energy-saving strategies in response to different energy pricing policy scenarios. Results reported in this paper are based on 572 respondents who completed the survey and responded to seven adaptation questions based on their current energy expenditures. A random parameters logit model is estimated to predict the probability of choosing a particular portfolio of energy-saving options. Estimation results indicate that individuals from different socio-demographic groups exhibit varied preferences. The saving option characteristics, especially cost related characteristics have significant effects on individuals' preferences. Moreover, the results also showed significant effects of choice set composition on energy saving options. Further, the energy pricing policies had showed mixed effects on individual's preferences.

An integrated process of CO2capture and in situ hydrogenation to formate using a tunable ethoxyl-functionalized amidine and Rh/bisphosphine system

An integrated process of CO2 capture and in situ hydrogenation into formate was achieved in 95–99% yield using a tunable ethoxyl-functionalized amidine and Rh/bisphosphine system, being regarded as an alternative carbon capture and utilization approach to supply fuel-related products, to circumvent the energy penalty in carbon capture and storage. CO2 was captured by non-volatile amidine derivatives with simultaneous activation to form zwitterionic amidinium carbonate, and subsequent hydrogenation was facilitated by Rh/bisphosphine. The adsorption capacity and hydrogenation efficiency can be optimized by tuning the ethoxyl side chain. Particularly, the alkanolamidine bearing an intramolecular hydrogen donor derived from 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) gave both a high CO2 uptake (molar ratio of 0.95 : 1) and excellent hydrogenation yield (99%). Furthermore, the silica-supported alkanolamidine was readily recovered and reused with the retention of good performance. This kind of carbon capture and utilization pathway could be a potential energy-saving option for industrial upgrading of CO2 from waste to fuel-related products in a carbon neutral manner.

Energy Saving Design of a Training Center in Dongguan

A training center design as an example, the impact of building energy-saving design on building energy consumption are showed. Energy-saving design options of air conditioning system and refrigerator are given. Lighting power density of the lighting system energy-saving design and the project of energy-saving design are provided.

Direct and indirect energy use in China and the United States

Greenhouse gas reduction and energy saving are becoming two important issues in both industrialized and developing countries, and policymakers are developing means to reduce total domestic energy use. We evaluate and compare the direct and the indirect energy use both in the People's Republic of China (China) and the United States of America (US) by looking at a series of hybrid energy input–output tables (1997, 2002, and 2007). We also apply SDA (structural decomposition analysis), to identify the factors causing energy intensity (energy use per unit of gross domestic product) to differ between the two countries, which lead to potential energy-saving options. Our results show that, besides the differences in direct energy use, huge differences also exist in indirect energy use between the two countries. Differences in indirect energy use are mainly due to differences in technology. Technological change and industrial-structure change are key factors to explain the inequality of energy intensity, while there is a significant trend towards the convergence of sectoral energy efficiency between the two countries.

Multi-Layer Approach to Future Green Mobile Communications

This article addresses design concepts for mobile radio communications particularly addressing the crucial trade-offs between system performance and energy-consumption. System performance depends on various adaptive procedures and parameters adopted at multiple OSI layers of the communication system. However, these procedures and parameters require spectrum and energy resources and contribute to the overall system and network energy-consumption and to the resulting CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission. This article also therefore presents a vision on green mobile communication technology, and analyses some trade-offs among different methodologies toward energy-efficient system-design. It particularly discusses the degrees of freedom in the design of communications systems and networks using various technologies, and investigates their energy-saving options.

Expanded Bed Adsorption: An Option For Energy Savings In Multiple Proteins Purification

Expanded Bed Adsorption enables the protein recovery directly from cultivations of microorganisms or cells and preparations of disrupted cells, without the need for prior removal of suspended solids. The performance ofan expanded bed is comparable to a packed bed owing to reduced mixing of the adsorbent particles, clogging/plugging of solid particles in the column, while fluidized bed requires more velocity which may hinder the adsorption equilibrium. However,optimal operating conditions are more restricted than in a packed bed/fluidized bed due to the dependence of bed expansion on the sizeand density of the adsorbent particles as well as the viscosity and density of the feedstock. These difficulties can beovercomes in expanded-bed chromatography. In this work the steady state hydrodynamic behaviour of expanded beds studied experimentally.The present study focused on hydrodynamics of multiple particles separation and subsequently can be applied to the multiple proteins separation in a single expanded bed.

Energy Efficient Dryer Operation—An Update on Developments

ABSTRACT Recent European legislation designed to limit carbon emissions and to reward the efficient use of energy will undoubtedly encourage dryer operators to reduce their fuel consumption. This article first describes such legislation, which includes the climate change levy, enhanced capital allowances for energy-efficient plant, emissions trading, and the integrated pollution prevention and control regulations. Techniques for measuring dryer performance, benchmarking the results, and analyzing different energy-saving options are then discussed. It is concluded that more stringent legislation coupled with technical improvements, and social, political and economic pressures will result in a cycle of continuous improvement in operating performance.

Process considerations and economic evaluation of two-step steam pretreatment for production of fuel ethanol from softwood.

To increase the overall ethanol yield from softwood, the steam pretreatment stage can be carried out in two steps. The two-step pretreatment process was evaluated from a techno-economic standpoint and compared with the one-step pretreatment process. The production plants considered were designed to utilize spruce as raw material and have a capacity of 200,000 tons/year. The two-step process resulted in a higher ethanol yield and a lower requirement for enzymes. However, the two-step process is more capital-intensive and has a higher energy requirement. The estimated ethanol production cost was the same, 4.13 SEK/L (55.1 cent /L) for both alternatives. For the two-step process different energy-saving options were considered, such as a higher concentration of water-insoluble solids in the filter cake before the second step, and the possibility of excluding the pressure reduction between the steps. The most optimistic configuration, with 50% water-insoluble solids in the filter cake in the feed to the second pretreatment step, no pressure reduction between the pretreatment steps, and 77% overall ethanol yield (0.25 kg EtOH/kg dry wood), resulted in a production cost of 3.90 SEK/L (52.0 cent /L). This shows the potential for the two-step pretreatment process, which, however, remains to be verified in pilot trials.

International comparisons of domestic energy consumption

Governments of many industrialized countries have committed themselves to substantially reduce their domestic emissions of greenhouse gases. Emission reductions can be achieved through technology- and/or sector-specific policies. To decide which part of the economy environmental policy should be concentrated at, insight must be gained into the relative importance of the various factors determining domestic aggregate fossil fuel consumption. By applying structural decomposition analysis (SDA) across nations, the factors causing per capita energy use to differ between countries can be identified, which sheds light on where potential energy-saving options can be found. To demonstrate the usefulness of between-country SDA, we apply the technique to a set of 8 OECD countries.

Integrated energy planning: Part I. The DEFENDUS methodology

The process of energy planning involves the estimation of future energy demand and the identification of a mix of appropriate sources to meet this demand. This mix must emerge from a rational procedure in which various energy generation and/or saving options are evaluated. A powerf ul, simple and transparent approach to energy planning -- the development-focused end-use-oriented service-directed (DEFENDUS) approach -- is discussed here. Demand for a source of energy is based on the services for which it is required -- the extent to which such services are spread among the population and the efficiency with which they can be delivered. The energy requirement so estimated is then matched with energy-supply and/or energy-saving options, so as to minimize costs. Starting with the reference energy system (RES) -- the energy system as it obtains in the present (or the most recent past for which data is available) -- the DEFENDUS approach constructs scenarios of future energy demand, paying deliberate attention to the equity and energy-efficiency considerations of alternative scenarios. The costs per unit of energy supplied/saved are then estimated, including both investment and operating expenses as well as the costs of delivery to the consumer and the losses in distribution. Environmental impacts -- and the cost of mitigatin g them -- can be taken into consideration in the methodology. The economic impacts of a chosen scenario can also be included. By ranking the energy supply/saving technologies in increasing order of costs, the least-cost mix is obtained. Whereas with most pre-programmed packages, the planner must accept the format already provided, the DEFENDUS approach suggested here enables one to validate every step of the computation procedure and modify assumptions according to the actual case being considered. The first part of the paper deals with the methodology proper. It refers to the reasons for developing such an energy-planni ng method, sketches a conceptual framework and then discusses the actual procedure in detail, including the usage and advantages of spreadsheets for computation. Part II (to be published in the following issue) will elaborate on examples of DEFENDUS scenarios.

Energy-saving distillation designs in ethanol production

A thorough study is made of energy-saving options for the distillation of a dilute, aqueous ethanol solution to produce a distillate close to the azeotrope composition. Although presented in the context of a fermentation ethanol plant, the system may be taken as a generic example of a dilute solution with highly nonideal vapor-liquid equilibrium behavior. Conventional energy-saving techniques, such as multiple heat-integrated columns, vapor recompression, and heat integration with the evaporation section are analyzed and compared. The most economical alternatives and conditions are identified. Sensitivity of the designs and costs to changes in design parameters and utility costs is studied. For a 95 vol % ethanol distillate, the most economical designs included vapor recompression or a two-column design with split feed for distillation and vapor recompression for the evaporation section. For higher purity distillate, vapor recompression and a two-column design with heavy split proved most attractive.

Energy-saving options

When several energy-thrift measures are implemented simultaneously in the same building, it is probable that the overall saving will be less than the sum of those expected if implemented individually, each time starting from the present situation. The relationship between such savings and capital investment has been obtained for 90 energy-saving options in total, implemented on four hospital sites. It is concluded that the financial returns on the capital expenditure are considerably enhanced by spreading the investment over several sites, rather than by investing in the relatively high rate-of-return options on only a single site.

The UK surface passenger transport sector: Energy consumption and policy options for conservation

The paper describes a study of the UK surface passenger transport sector whose main objectives were to investigate the pattern of present and future energy consumption and to provide a preliminary options to reduce energy use. Analysis shows the dominance of travel by private car in energy consumption patterns. Forecasts of energy consumption are then presented for four alternative future as a basis for evaluating long-term energy-saving options. This evaluation suggests that the most attractive policy relates to changes in private vehicle technology. However, there is considerable uncertainty about the outcome of this and other policy options.