Analysis of electrical motors load factors and energy savings in an Indian cement industry

Electric motors consume in between 30% and 80% of the total industrial energy use for few selected countries around the world. It was identified that many motors are operated under loaded conditions. In some cases, motors are operated even at 3-16% of their full loads. These low loads can be optimized with the application of variable speed drives (VSD) to match the load requirements. Based on the estimation, it has been found that annually about 1,865,925 MWh of energy can be saved for 60% speed reduction when VSDs are used. It was also found that about 2,122,675 tons CO₂emission could be avoided annually by using VSDs for Low Tension (LT) motors for 60% speed reduction. It was also estimated that annually about 4,600,386 MWh of energy can be saved for High Tension (HT) motors for 60% speed reduction using VSDs. The average payback period (PBP) for implementing VSDs for LT and HT motors found to be very low (i.e. about 2 days). In this particular study it is observed that installing both LT and HT capacitors to improve power factor found to be not economically viable owing to low level of energy savings.     

Qualitative response models and the estimation of energy savings from utility conservation programs

Reducing uncertainty in the measurement of energy-saving effects of conservation retrofit programs is the focus of this paper. Measuring the actual quantity of energy savings is an elusive goal. The goal of an evaluation of energy savings is to measure the difference between energy consumption of participant households and that of the same households in the absence of the program. Because the program exists, this difference can only be estimated. We present methodologies which can be used to approximate participant usage in the absence of a program. The first two models are currently applied in evaluating these conservation programs. The last are innovative models using qualitative choice techniques designed to correct for self-selection bias.     

A glazing unit for solar control, daylighting and energy conservation

The glazing unit for solar control, daylighting and energy conservation is a system consisting of two prismatic panes. The prismatic ribs of the panes are inclined by a certain angle to the horizontal within the window plane, exhibit identical cross-sections in the shape of a rightangle-triangle with a certain basic prism angle, are facing each other and are positioned such that just a small gap remains between the two panes. The lower rib faces of the outer prismatic pane are coated with a specularly reflecting layer and the upper rib faces of the inner prismatic pane are coated with a diffusely reflecting layer. The prismatic glazing unit can be used for common window tilt angles and for window directions with significant solar irradiation at sites with a temperate climate. It does not reduce the view to the outside appreciably and achieves — in comparison to other window panes — relatively uniform illumination of a room with daylight. During the summer and the transitional seasons it provides improved protection against solar irradiation and distinctly reduced irradiated heat fluxes. The reflecting surfaces of the prismatic ribs do not create glare.     

Rewarding energy savings rather than energy efficiency: Exploring the concept of a feed-in tariff for energy savings

Financial incentives are important for overcoming certain market barriers to improved energy efficiency and for the adoption of energy efficient technologies. Financial incentives are mainly focused on the introduction of specific technologies, rather than behavioural change. While the declared goal of financial support schemes very often is to save energy or reduce harmful emissions rather than to foster new technologies per se, it is often encountered that such financial support for energy efficient technologies may not ensure real energy savings due to the rebound effect and various market barriers.In the area of renewable energies it is common for financial support to be given to power producers for the verified production of renewable electricity, in the form of a guaranteed financial incentive (feed-in tariff). In the energy efficiency policy research little attention has been paid to the possible use of a “feed-in tariff” in the form of a financial incentive based on the kWh saved by the end-user. This paper discusses the possible setup of a feed-in tariff designed to reward energy savings.     

Energy efficiency and energy savings

Technical energy conservation, in which energy is saved by producing the same goods and services at higher efficiency, is contrasted with energy savings produced by shifting end uses from more to less energy intensive activities. It is shown that the former is considerably more effective in saving energy. The general theory is confirmed by the use of concrete examples.     

Tradable certificates for renewable electricity and energy savings

Tradable green certificates (TGCs) schemes have been developed and tested in several European countries to foster market-driven penetration of renewables. These certificates guarantee that a specific volume of electricity is generated from renewable-energy source (RES). More recently certificates (tradable white certificates (TWCs)) for the electricity saved by demand-side energy-efficiency measures (EEMs) have been introduced in some European countries. Recent advances in information and communication technology have opened up new possibilities for improving energy efficiency and increasing utilization of RESs. Use of technological resources such as the Internet and smart metering can permit real-time issuing and trading of TGCs. These technologies could also permit issuing of TWC. This paper reviews current renewable TGC and TWCs schemes in Europe and describes the possibilities for combining them in an Internet-based system. In the proposed combined tradable certificate scheme, both RESs and demand-side EEMs could bid in real time through the Internet to meet a specific obligation. The energy savings from the demand-side measures would be equivalent to the same amount of green electricity production. The paper describes the needed common targets and obligations, the certificate trading rules and the possible monitoring protocol. In particular, the paper focuses on the TWCs verification issues, including the assessment of the baseline, as these poses additional problems for TWCs compared to TGCs.     

Measuring industrial energy savings

Accurate measurement of energy savings from industrial energy efficiency projects can reduce uncertainty about the efficacy of the projects, guide the selection of future projects, improve future estimates of expected savings, promote financing of energy efficiency projects through shared-savings agreements, and improve utilization of capital resources. Many efforts to measure industrial energy savings, or simply track progress toward efficiency goals, have had difficulty incorporating changing weather and production, which are frequently major drivers of plant energy use. This paper presents a general method for measuring plant-wide industrial energy savings that takes into account changing weather and production between the pre and post-retrofit periods. In addition, the method can disaggregate savings into components, which provides additional resolution for understanding the effectiveness of individual projects when several projects are implemented together. The method uses multivariable piece-wise regression models to characterize baseline energy use, and disaggregates savings by taking the total derivative of the energy use equation. Although the method incorporates search techniques, multi-variable least-squares regression and calculus, it is easily implemented using data analysis software, and can use readily available temperature, production and utility billing data. This is important, since more complicated methods may be too complex for widespread use. The method is demonstrated using case studies of actual energy assessments. The case studies demonstrate the importance of adjusting for weather and production between the pre- and post-retrofit periods, how plant-wide savings can be disaggregated to evaluate the effectiveness of individual retrofits, how the method can identify the time-dependence of savings, and limitations of engineering models when used to estimate future savings.     

Artificial neural networks for energy analysis of office buildings with daylighting

An artificial neural network (ANN) model was developed for office buildings with daylighting for subtropical climates. A total of nine variables were used as the input parameters – four variables were related to the external weather conditions (daily average dry-bulb temperature, daily average wet-bulb temperature, daily global solar radiation and daily average clearness index), four for the building envelope designs (solar aperture, daylight aperture, overhang and side-fins projections), and the last variable was day type (i.e. weekdays, Saturdays and Sundays). There were four nodes at the output layer with the estimated daily electricity use for cooling, heating, electric lighting and total building as the output. Building energy simulation using EnergyPlus was conducted to generate daily building energy use database for the training and testing of ANNs. The Nash–Sutcliffe efficiency coefficient for the ANN modelled cooling, heating, electric lighting and total building electricity use was 0.994, 0.940, 0.993, and 0.996, respectively, indicating excellent predictive power. Error analysis showed that lighting electricity use had the smallest errors, from 0.2% under-estimation to 3.6% over-estimation, with the coefficient of variation of the root mean square error ranging from 3% to 5.6%.     

A review on compressed-air energy use and energy savings

Compressed-air systems account for about 10% of total industrial-energy use for few selected countries as found in literatures. Compressed air is typically one of the most expensive utilities in an industrial facility. This paper describes a comprehensive literature review about compressed air energy use, savings, and payback period of energy efficient strategies. This paper compiles latest literatures in terms of thesis (MS and PhD), journal articles, conference proceedings, web materials, reports, books, handbooks on compressed air energy use, efficiency, energy savings strategies. Computer tools for compressed air analysis have been reviewed and presented in this paper. Various energy-saving measures, such as use of highly efficient motors, VSD, leak prevention, use of outside intake air, reducing pressure drop, recovering waste heat, use of efficient nozzle, and use of variable displacement compressor to save compressed-air energy have been reviewed. Based on review results, it has been found that for an electric motor used in a compressed-air system, a sizeable amount of electric energy and utility bill can be saved using high efficient motors and applying VSDs in matching speed requirements. Also, significant amounts of energy and emission are reducible through various energy-saving strategies. Payback periods for different energy savings measures have been identified and found to be economically viable in most cases.     

Measuring energy savings — problems

The contribution of government energy conservation programmes to reducing national energy is an important but largely unresolved issue. This paper discusses estimating the energy-savings impact of US Department of Energy (DOE) conservation programmes. Programme-by-programme estimates of energy savings have been analysed, the results indicating that DOE conservation programmes have reduced US energy use by more than 0.5 quadrillion British thermal units (quads) annually since 1981. Limitations in the available evaluative information, however, preclude reaching unambiguous conclusions.     

A review on electrical motors energy use and energy savings

The industrial sector is the largest users of energy around the world. Industrial motor uses a major fraction of total industrial energy uses. This paper describes a comprehensive literature review about electric motor energy analysis. This paper compiles latest literatures in terms of thesis (MS and PhD), journal articles, conference proceedings, web materials, reports, books, handbooks on electrical motor energy use, losses, efficiency, energy savings strategies. Different types of losses that occur in a motor have been identified and ways to overcome these losses explained. An energy audit that helps to identify motor energy wastages have been discussed extensively. As motors are the major energy users, different energy savings strategies such as use of high-efficient motor, variable speed drive (VSD), and capacitor bank to improve the power factor to reduce their energy uses have reviewed. Different policy measures (i.e. regulatory, voluntary and incentives based) to save motor energy use have been reviewed and presented in this paper. In this review, computer tools that can be used to analyze electric motors energy used has been discussed. Cost parameters to carry out economic analysis have been shown as well. Moreover, payback period for different energy savings strategies have been identified.     

Designing heat-exchanger networks for energy savings in chemical plants

The pinch-design method is applied to the evaluation of heat-exchanger networks for an existing monomer plant. The problem resulting from partially condensed multicomponent vapor streams possessing variable CP ( ) values is solved by applying a novel technique. The rigorous design obtained is further revised by the consideration of plant constraints.     

Potential energy savings in the production route for plastics

The gross energy requirement (GER) for the major petrochemical products (ethylene, propylene, butadiene and benzene) and the major bulk polymers (low density polyethylene, polypropylene, polystyrene and polyvinylchloride) is determined. The GER-values for LDPE, PP, PS and PVC are 69.8, 61.6, 81.5 and 55.7 GJ/ton, respectively. The potential energy saving in the process chain for each product is assessed on the basis of commercially available technologies. The profitable potential, savings (i.e. with a payback period shorter than 3 yr) is about 8% of the GER-figure. The technical potential for savings varies from 12% for ethylene to 25% for PVC. In addition, the potential savings are investigated for the industrial sectors involved, namely oil refining (15% of total primary energy demand), inorganic chemicals (6%) and petrochemicals (9%).     

On the energy efficiency of a prototype hybrid daylighting system

This paper presents the development of a method to control the light output from a prototype hybrid lighting system. This system transports daylight from a heliostat with a concentrating fresnel lens to a luminaire in a windowless room, via a large core liquid fiber optic. The main artificial lighting system is located outside of the building without the possibility for dimming due to the lamp type chosen. Consequently a control strategy is needed in order to minimize the switching cycles of the lamps (severe reduction in lamp life) while at the same time maintain the lighting levels in the interior.     

PCM-facade-panel for daylighting and room heating

Double glazings combined with phase change materials (PCM) result in daylighting elements with promising properties. Light transmittances in the range of 0.4 can be achieved with such facade panels. Compared to a double glazing without PCM, a facade panel with PCM shows about 30% less heat losses in south oriented facades. Solar heat gains are also reduced by about 50%. This results in calculated U_eff-values of −0.3 to −0.5 W m⁻² K⁻¹, depending on PCM used. For an optimised panel, we calculated an U_eff-value of −0.6 W m⁻² K⁻¹. Although the U_eff-value of a double glazing is −0.8 W m⁻² K⁻¹, the PCM-systems may prove advantageous in lightweight constructed buildings due to their equalised energy balance during the course of day. Facade panels with PCM improve thermal comfort considerably in winter, especially during evenings. In summer, such systems show low heat gains, which reduces peak cooling loads during the day. Additional heat gains in the evening can be drawn off by night-time ventilation. If a PCM with a low melting temperature of up to 30 °C is used, thermal comfort in summer will also improve during the day, compared to a double glazing without or with inner sun protection. A homogeneous appearance of the PCM-systems is achievable by use of a concealment, like a screen-print glazing.     

Reversible low solar heat gain windows for energy savings

Summer cooling loads in buildings can be reduced with windows of low solar heat gain coefficients (SHGC). Such windows are often double glazed with the exterior pane tinted or selectively absorbing. They reject part of the absorbed solar radiation to the environment, reducing the solar heat gain. This effect is undesirable in the cold season. However, the same window installed in reverse, i.e. turned by 180°, has a significantly higher SHGC. Thus, windows that can be reversed according to the season will both reduce summer heat gains and collect much of the beneficial solar radiation in winter. This paper investigates the energy savings achievable by reversing equator-facing windows for the duration of the cold season as opposed to leaving them in the “summer position”. Candidate climates in which these savings may be significant are identified. By means of a computer simulation, seasonal energy savings are predicted for a model room with reversible, low SHGC, windows. The results indicate that for suitable climates, significant savings are achievable.     

Green vertical systems for buildings as passive systems for energy savings

This paper presents a classification of green vertical systems for buildings. The aim of this classification is to facilitate the identification and differentiation between systems. This classification is also essential to compare future research results relating to their operation. In addition, the mechanisms by which green facades can be used as passive energy savings systems are reviewed: shadow produced by the vegetation, insulation provided by vegetation and substrate, evaporative cooling by evapotranspiration, and the barrier effect to the wind. Finally, the paper describes the first results about the behaviour of a double-skin green facade or green curtain in Dry Mediterranean Continental conditions. It is verified that a microclimate between the wall of the building and the green curtain is created, and it is characterized by slightly lower temperatures and higher relative humidity. This means that the green screen acts as a wind barrier and confirms the evapotranspiration effect of the plants.     

Lightpipe applications for daylighting systems

One of the main research activities of the Institute of Lighting at Technical University of Berlin concerns efficient daylight utilisation in buildings. In recent years, several national and international projects have been and are still carried out. One of them, the European research project ARTHELIO, has examined the possibility of guiding daylight into deeper building interiors using hollow light guides. The aim is to provide daylighting in deeper building interiors. Within this project, a goniophotometer was developed and built, to measure the luminous intensity distribution of lightpipes. In two demonstration sites, the daylight utilisation by the hollow light guides combined with heliostats has successfully been demonstrated. Daylight is collected by heliostats and enters the building. It is guided along hollow light guides and coupled out along its way to illuminate the building interior. Measurements show that the prototypes help to decrease the energy consumption for electric lighting of the building.     

Potential energy savings and environmental impact by implementing energy efficiency standard for household refrigerators in China

With the rapid economic growth and improvement in standard of living, Chinese people are employing more and more household appliances to make their living convenient and comfortable, of which refrigerators are indispensable. Because refrigerators operate continuously irrespective of seasons and regions, the total electricity consumption of refrigerators is huge and consequently causes severe energy-related environmental issues. China has been paying more and more attention to this and issued a national energy efficiency standard, GB12021.2-2003, for refrigerators. This paper first describes the standard briefly. Then it develops a mathematic model to evaluate the potential energy savings and environmental impacts of the standard. The estimated results indicate implementing the standard will save large energy, as well as benefit greatly to environment. Thus, it is very necessary to implement energy efficiency standard for refrigerators in China.