Estimates of the energy impact of ventilation and associated financial expenditures

Ventilation is essential for the maintenance of good indoor air quality, although there is evidence to suggest that energy loss through uncontrolled or unnecessary air infiltration is excessive. In this study, estimates are presented for air change (ventilation and infiltration) energy use in non-industrial buildings for 13 countries. Various methods are used for the estimates, but they are mainly based on calculating the total annual enthalpy change needed for the conditioning of air. The potential for reduced energy use by improved ventilation control is also briefly reviewed. Considering the non-industrial building stock of the 13 countries collectively, the total annual loss of heating energy due to air change is estimated to amount to 48% of delivered space conditioning energy (including heating equipment losses). The results emphasise that air change related energy losses are as important as conduction and equipment losses (including ‘flue’ losses) in dissipating delivered space conditioning energy from buildings.In addition, estimated financial expenditures, as well as carbon dioxide emissions associated with this energy use are indicated. The financial expenditures are derived from the air change energy estimates using published International Energy Agency (IEA) energy pricing information. The magnitudes of the carbon dioxide emissions have been based on published IEA estimates of total emissions from energy-related sources for each country.     

A comprehensive and well tested energy balance for water supply systems

This paper presents a novel energy balance scheme and performance indicators for assessing energy efficiency in water supply systems. This assessment consists of a three-step procedure: system characterisation and data collection, energy balance calculation and energy performance indicators assessment. The main innovation is the integrated approach between energy and water balances allowing the quantification of energy inefficiencies directly associated with water losses. Comprehensive energy performance indicators can be calculated by utilities with different maturity levels allowing a fair comparison of energy efficiency between systems with different layouts and operational schemes. This energy balance scheme has been applied by 17 water utilities in Portugal. Results have shown that systems provide more than twice the minimum energy necessary to supply their consumers and, consequently, there is a significant energy saving potential: 40% through water loss reduction, 30% for changes in network operation and layout and 30% for pump inefficiency reduction.     

Exergetic analysis of closed Brayton thermal power cycle with reheater,regenerator and intercooler

Energy and exergy analysis of a Brayton cycle gas turbine power plant with regenerator, reheater and intercooler is carried out in this work. It has been found that the effects of the regenerator, intercooler and reheater are significant. Although, the energy analysis shows that the first law efficiency is more effective than the second law efficiency and there are significant losses in these components which cannot be neglected, and hence proper care should be taken for the size and operating conditions of these components. Efficiency of some components is 100% especially when energy balance is applied, while it is not 100% in the case of energy consuming/conversion systems like compressor, turbine, etc. The energy loss in reheater is zero while there is a small amount of exergy loss. The intrercooler has both energy and exery losses, so proper care should be taken in intercooler.     

An approach to optimising compressed air systems in production operations

A low-cost, non-intrusive method of quantifying the energy consumed by compressed air systems (CASs) and lost through system leaks is described, with various means of minimising energy consumption presented. Case studies across different industrial facility types are examined where the approach used in quantifying energy losses due to system leaks has been implemented. Monitoring across 5 sites identified circa 500,000?kWh of waste energy due to leaks of which 30–60% can be saved. The approach has reduced waste electrical consumption by 60% on one site. Non-energy-related benefits arising from awareness of CAS losses are described. The proposed approach effectively illustrates the benefits of CAS energy analysis in a manner which can be quickly and easily implemented using off-the-shelf energy monitoring and data-logging equipment. The methodology can be regularly applied to provide continual monitoring and management of the optimal state of an industrial facilities CAS.     

Effect of reference state on the performance of energy and exergy evaluation of geothermal district heating systems: Balcova example

In this paper, we undertake a parametric study to investigate how varying reference temperature from 0 to 25 °C will affect the energy and exergy efficiencies of the Balcova geothermal district heating system (BGDHS) and develop two significant correlations (with a correlation coefficient of 0.99) that can be used for predicting the efficiencies. The exergy losses in the overall BGDHS are quantified and illustrated using exergy flow diagram particularly for a reference temperature of 11.4 °C for comparison purposes. This reference temperature is taken as an average value of the ambient temperatures measured during the past 5 years for the day of 2nd January to reflect the actual situation. The results show that the exergy losses within the system occur mainly due to the losses in pumps, heat exchangers, reinjection sections of the geothermal water back into reservoir and pipeline, and account for 1.75%, 8.84%, 14.20%, and 28.69%, respectively. In addition, we study energy and exergy efficiencies to determine the possibilities to improve the system, and energy and exergy efficiencies of the system are found to be 42.36% and 46.55%, respectively, for 2nd January 2004.     

Recovery from the effects of fire in industry

Case studies have been made of four industrial fires that have occurred in the South of Scotland area, with the particular objective of identifying the losses that occurred due to interruption of production and other consequences that followed the fire. The businesses in which the firms were engaged were engineering sub-contracting, plastics moulding, joinery and electrical engineering. The problems in the individual firms in returning to a pre-fire status were identified. In none of the firms had there been any contingency planning for fire. A number of factors which caused diffifulties in recovery emerged, for example, the effect on morale of working in smoke damaged and dismal post-fire surroundings, the inconvenience to customers followed by loss of business, the replacement of essential services and raw material stocks, the excessive maintenance of machinery damage by rust, etc. However, no uniform picture of the extent or importance of consequential losses became apparent. There was evidence that firms organised on an efficient production engineering basis might suffer more fire than firms with more slack in space or production line availability. This implies that contingency planning against business or interruption losses following a fire should become a necessary part of production engineering since efficient schedules under normal conditions might be much upset by fire.     

Solar reflectivity of common building materials and its influence on the roof heat gain of typical southwestern U.S.A. residences

The fraction of incident solar energy reflected by the exterior elements of a structure significantly effects the overall heat gain or loss of the structure. This is particularly true for regions that receive an abundance of solar insolation as occurs in the southwestern part of the United States. However, the available data on the solar reflectivity of common building materials are apparently rather sparse. In order to augment these data, the authors developed a probe for measuring hemispheric solar flux and employed it to measure the solar reflectance of a wide variety of building materials. Results of these measurements are presented and reviewed. The measured reflectivity values have also been used in heat gain/loss computations for typical southwestern residences. Results of some of these computations are presented to demonstrate the change in structure heat gain/loss that can realistically be achieved by altering roof reflectivity.     

污泥干化焚烧系统的节能降耗研究

以某污泥干化焚烧处理工程为研究对象,分别建立污泥干化系统、焚烧及余热利用系统和烟气处理系统的能量平衡模型。基于实际运行数据和现场测定数据,确定了运行期间污泥干化焚烧系统中主要的能量损失点,包括干化载气洗涤水热损失、干化机散热损失、焚烧炉及余热利用系统散热损失、烟气洗涤水热损失等。针对系统主要的能量损失点,提出了针对全过程的节能降耗方案。即,首先通过运行参数调节来提高干化机和焚烧及余热利用系统效率从而减少散热损失,再通过余热利用干化载气以及洗涤塔前烟气,从而减少载气洗涤排污热损失和烟气洗涤水热损失。     

Thermodynamic investigation of an integrated DI diesel engine with waste heat operated rankine cycle

ABSTRACT

A DI Diesel Engine has been integrated with a Rankine Cycle for making a proposed ‘integrated power generation cycle’. The heat of engine’s exhaust gases and jacket’s water is as a single heat source to produce additional output power through the Rankine Cycle. In exergy analysis, destruction of input exergy is nearly 64.13% due to irreversibilities. The useful exergy output is about 30.3%. The exhaust exergy lost to atmosphere is 5.39%, which is smaller than 20.83% of exhaust energy loss of its input, whereas the useful energy output is almost 38.02%. Moreover, there is the reduction in the BSFC due to the recovery of the exergy from the waste heat. The average reduction in the BSFC is about 18.42%. The results of this proposed cycle also show that the integration of the Diesel Engine with the Rankine Cycle has drastic effect on the efficiencies based on exergy and energy.     

750kV输电线路架空地线损耗的影响因素及降低方法研究

输电线路电压等级越高,地线上的电能损耗就越大,如何降低地线损耗意义重大。分析了电能在地线中产生损耗的原因,通过EMTP仿真计算了在各种情况下电能损耗,比较了采用地线分段后的效果,得出:对750 kV输电线路采用分段绝缘的绝缘方式,有效地减小地线上的感应电流,使地线的损耗降抵为地线两端直接接地时的99%以上;三相负载平衡程度越小,地线产生损耗会越大,应尽量保证系统三相负载平衡;适当调整接地电阻的大小可以优化地线电能损耗;输电线路长度增加,地线损耗和地线上的感应电压也增大,应选取合适的分段距离,使地线损耗降低到最小。     

深层搅拌桩设计中几个问题的探讨

在深层搅拌桩设计中,布桩间距、负摩阻力等问题不应该被忽略;当复合地基中存在相对软弱夹层时,应对其进行强度验算;当桩端未加固土层以下有软弱下卧层时,应对其进行软弱下卧层验算：应采用多种方法进行复合地基沉降计算。     

Embodied energy analysis of the indirect solar drying unit

The increase in cost of fossil fuel and unavailability of electricity are the barrier for farmers to run their farm machineries and their development. Solar drying is a technique that not only helps in reducing fossil fuels and greenhouse gas emission by avoiding the use of machines in this sector, but also reduces the post-harvest food losses too. In present study, embodied energy analysis has been done for indirect solar dryer unit. Fenugreek leaves of 02?kg were put in each tray inside indirect solar dryer unit for drying purposes. Various environmental and economic parameters have been evaluated, which includes the payback period by cost, the energy payback time (EPBT), embodied energy, CO₂ emission and the earned carbon credit. The total embodied energy of the system is 1081.83?kWh. The EPBT and CO₂ emission are found to be 4.36 years and 391.52?kg per year, respectively.     

旧有建筑外墙保温改造的经济效益分析

在采暖区旧有建筑外墙基本未采取有效的保温措施、耗能量大,室内热环境较差。为节约能量,同时提高人们居住的舒适性,提出了给旧楼“穿棉衣”的保温改造计划。本文就具体工程实例介绍保温改造的施工方法,并对“保温改造”进行了经济分析。     

预应力混凝土箱梁桥竖向预应力损失的实测与分析

基于某大跨预应力混凝土连续箱梁桥腹板竖向预应力的现场长期测试结果,对箱梁竖向预应力的各种损失进行了分析。结果表明:就所研究的情形而言,实测竖向预应力总损失可达其初始张拉应力的45%,锚具变形、钢筋回缩及接缝压缩等引起的损失占其总损失的53%。按现行公路桥规(JTGD62-2004)中确定纵向预应力损失的方法计算竖向预应力筋相应的各种损失,所得结果与相应各项损失的实测值基本吻合。对于竖向预应力传力锚固后损失的计算,收缩徐变模型的选取对其结果影响较大。此外还探讨了温度和后续荷载等因素对竖向预应力损失的影响,结果表明:后续荷载作用对竖向预应力损失的影响较小可予以忽略,而混凝土及孔道砂浆中水泥水化热造成的损失可达总损失的18.9%,因此必须予以考虑。     

Double skin façade's effects on heat losses of office buildings in Istanbul

As is known double skin façade applications have an important role on passive solar strategies. In this paper, heat losses of a single skin and a double skin façade office buildings were compared to show the effect of double skin on building energy demand for winter period in Istanbul. Calculations have been carried out for the January, which is assumed as the representative month of winter period in Istanbul considering Istanbul's climatic conditions. However there is no any double skin façade application in Istanbul, the thermal effect of the double skin has been theoretically analysed to show the effect of double skin façade on heat losses if this technology would be applied by the construction industry in Turkey. In this study a new method is used in double skin façade's heat losses calculations. The realization of the proposed method is composed of two main steps. The first step is formed from the modification of a previous method, which is proposed by Todorovic, to calculate inter-space temperature. For the second step inter-space temperatures calculated in the first step have been accepted as outdoor air temperature and time dependent heat transfer through the inner skin of the envelope has been calculated by using finite difference numerical approach. It has been assumed that the space between two skins is closed since the calculations have been made for the winter period. It has been concluded that heating energy consumption is significantly reduced in double skin façade building for winter conditions in Istanbul.     

Impact of grey energy on optimal wall insulation thickness

For decades efforts have been made to reduce the greenhouse gases emissions of buildings by reducing their energy demand with governmental regulations in Europe, pushing towards very low thermal transmittances (U-values) with ever thicker insulation layers for new buildings. However, there is no linear relationship between the insulation thickness and the heat losses. Therefore, above a certain thickness the consumption of buildings does not decrease significantly. Hereafter a life cycle analysis, including emissions before the building becomes operational is applied to evaluate the impact of the increasing thickness of components on the overall emissions. Publicly available product data sheets are used to compare four insulation materials under three scenarios. These analyses yield interesting results showing that energy-intensive insulation materials lead to a negative impact in the overall energy balance after a certain thickness. Even though there is not always a pronounced optimum insulation thickness, it is logical that further reductions in U-value for new buildings should hence be carefully evaluated. The results show that the optimal thickness is around 20 cm for most materials, while the important major savings come from the first 10 cm.     

Stream cation concentrations and losses from drainage basins with contrasting land uses in Southern Ontario

The concentration and loss of major cations from 22 watersheds near Toronto, Ontario, was measured over a 27-month period. Calcium and potassium concentrations exhibited a positive relationship with crop area and a negative correlation with abandoned farm land + forest and areas of sand + sandy loam soil. The influence of soil properties and farming activities on streám cation levels could not be separated because of multicollinearity between land use and soils. An absence of correlation between crop area and annual losses of calcium and potassium can be attributed to lower annual stream discharges in agricultural watersheds in comparison to watersheds containing extensive areas of forest and abandoned farm land. Stream concentrations and losses of potassium and sodium were positively correlated with urban land use. Detailed water sampling in the vicinity of urban centres confirmed that these areas are important contributors of sodium, and to a lesser extent, of potassium to streams. Magnesium concentration was influenced mainly by differences in watershed hydrology and no correlation was evident with urban or agricultural land use.     

Impact of the River Maine Drainage Scheme on Hydro-Power Generation

A comparison is made between pre- and post-drainage scheme river flows recorded on the River Maine, Co. Antrim. A method of using five-year reference periods has been applied to the mean daily flows to smooth and eliminate, as far as possible, variations due to climatic changes.
Any loss of energy production which might have been due to changes in river flow was examined for turbine installations at a factory at Cullybackey. The quantities of usable water, and hence potential energy production, were calculated for each of the post-scheme five-year periods and compared with a pre-scheme five-year reference period. Any potential loss was then represented by a depreciation factor. It was found that no measurable loss of potential energy production has occurred on the River Maine in the post-scheme period.     

Coal,oil, or clean energy: Which contributes most to the low energy efficiency in China?

The lack of energy efficiency in China is always of interest. This paper builds a total-factor energy efficiency framework which contains coal energy, oil energy, and clean energy, which emits fewer pollutants into the atmosphere when used. We study the “China Statistical Yearbook” and the “China Energy Statistical Yearbook” to identify which type of energy contributes most to low energy efficiency in China. Our conclusion is that the total-factor energy efficiency (TFEE) in China has been at a relatively low level without any significant improvement from 1998 to 2010. The efficiencies of coal and oil energy have improved moderately, while there is no obvious improvement in the efficiency of clean energy. Despite the moderately improved efficiency of coal energy, its relatively low level contributes most to the overall energy inefficiency because it is the main fuel used in China. Further, the lack of improvements in the efficiency of clean energy makes it another area of policy interest.     

Measuring residential duct efficiency with the short-term coheat test methodology

Assessing the thermal efficiency of a forced-air distribution system is difficult, in large part because of interactions between energy loss mechanisms and other building characteristics. This paper describes short-term coheating, a method of measuring the thermal efficiency of residential heating and cooling distribution systems in situ, and presents the results of a series of studies that utilized the short-term coheat methodology. Short-term coheat tests were conducted in 53 residential buildings including both site-built and manufactured housing. The magnitude of the distribution efficiency, defined as the ratio of the energy required to heat the building if there were no duct losses to the actual heating energy required, ranged from less than 50% for homes with disconnected ducts to more than 90% for well sealed and insulated systems. Duct retrofits were also performed at 20 of the test sites and, following the retrofits, on average, the homes required 16–17% less heating energy. These results show that residential distribution system losses can be responsible for substantial energy loss and that duct retrofits are a viable energy conservation strategy for homes with distribution systems located outside of the conditioned space.