[, Despite the widespread use of SEC as an indicator for energy efficiency, critical scientific papers on SEC seem—in the authors’ opinion—to be almost lacking. For example, how the PEFs were calculated and what data was used. Phylipsen, G.J.M. Concepts, indicators and methodological issues. Following the principles of Equations (1)–(3), in order to evaluate the usage of individual energy carriers for individual products or a sum of products the individual energy carriers can be used instead. It is also the fundamental relationship used in the standard step method to calculate how the depth of a flow changes over a reach from the energy gained or lost due to the slope of the channel. Open Channel Flow, Prentice-Hall. It can be seen that the dimensionless momentum function (M') has the identical functional relationship as the dimensionless specific energy function (E") when both are properly transformed. . Further quantitative analyses are recommended on SEC from various studies for studying the underlying tendencies and relationships among the factors affecting SEC, e.g., the time trends, extent of studies, levels of benchmarking, etc. Wilby, M.R. Another way to prevent getting this page in the future is to use Privacy Pass. It is likely that SEC is an optimal e-KPI within the same study, when all deployed SECs are calculated in the same way, and with the same underlying assumptions. [, Regarding the total amount of energy, uncertainty comes from using energy from non-primary energy carriers, such as electricity. Chan, D.Y.L. With the aim of critically analysing SEC in relation to industrial energy efficiency, some conclusions could be drawn from this study: SEC is of greater use if longitudinal benchmarking, i.e., the same company, sector or country, over time, is undertaken. Rogers, J.G. There are usually a couple of reasons why measuring the energy present per mass unit is important. Swing Gustafsson, M.; Gustafsson, M.; Myhren, J.A. In Proceedings of the 2004 TAPPI Technical Conference, Indianapolis, IN, USA, 29 August–2 September 2004; p. 10. From this duality concept we can determine the analog to the conjugate depth equation for the specific energy equation to provide an analytical relationship between alternate depths y1 and y2. In US customary units, Q is in ft3/sec. With the pressure term neglected, energy exists in two forms, potential and kinetic. Performance & security by Cloudflare, Please complete the security check to access. Wikibuy Review: A Free Tool That Saves You Time and Money, 15 Creative Ways to Save Money That Actually Work. %âãÏÓ For example, describe whether energy use by auxiliary systems, wastewater treatment facilities, support systems, in situ transport, etc. and the total specific energy at any point in the system is. Farla, J.; Blok, K.; Schipper, L. Energy efficiency developments in the pulp and paper industry. When carrying out a top-down savings calculation, energy indicators will be selected and used. The kinetic energy, in feet, is represented as the velocity head. [...] The problem arises when the energy input (ΔH) has to be allocated to the different outputs (tonnes) in order to generate the desired indicators.”. ; Brinker, L. A preliminary investigation of energy return on energy investment for global oil and gas production. The authors declare no conflict of interest. Hall, C.A.S. The critical energy expression is demonstrated graphically by the line ; Blok, K.; Worrell, E. International comparisons of energy efficiency-Methodologies for the manufacturing industry. (Henderson 1966). This relationship does not hold true at critical energy where only the critical depth, yc, is possible and for energy values less than critical depth’s energy where there are no positive depths. Using the conjugate depth equation and the duality concept between the dimensionless forms of the momentum (M') and specific energy (E") functions an analytical relationship between alternate depths can be obtained. In specific terms, the energy would typically be measured as calories/gram (cal/g), kilocalories/kg (kcal/kg), or kilocalories per gram (kcal/g). What is energy efficiency? Specific energy and energy density are useful measures of the energy that will be released from a given weight or volume of fuel when it is burned. ; Hall, C.A.S. ; Norman, J.B. Use of industrial energy benchmarking with reference to the pup and paper industries. <> When the same data is used to calculate SEC for the total energy, the results show that the fixed PEF of 2.5 gives ~11% higher SEC for total energy for pulp mills and ~15% higher SEC for total energy for paper mills (. Specifically, this article was inspired by experiences while studying SEC to research industrial energy efficiency and factors tending to affect the energy efficiency as well as by research addressing energy management and energy efficiency, where SEC is commonly used as an e-KPI. 10. Sluice gates are used to control the flow of water in open channels and under ideal conditions, where friction is ignored, they conserve energy for a given discharge. Authors to whom correspondence should be addressed. The concept of alternate depths can be demonstrated with a sluice gate example. = Assumptions for SEC calculations are rarely given. For a fluid of weight (ρg) at a height y above the established datum, the potential energy is wy. Examples of how many and what type of companies that have been studied in the PPI are 48 pulp and paper mills in Sweden 2006–2015 [, The results are based on a literature search using Linköping University Library’s literature search system—UniSearch—that was described in detail in Lawrence et al. Another important concept that can be applied towards the derivation the alternate depth equation arises from the comparison of the dimensionless momentum function to the dimensionless specific energy function. For instance De Beer et al. You seem to have javascript disabled. King, C.W. This relationship can be used to calculate changes in depth upstream or downstream of changes in the channel such as steps, constrictions, or control structures. This means subcritical flow has high potential energy and low kinetic energy. Three different q values are plotted on the specific energy diagram above. Specific energy is the energy per unit mass of a fuel. What is the flow depth downstream of the sluice gate, y2? Headloss due to friction is also neglected when determining specific energy; therefore this term disappears as well. 2016-02-16T07:42:12+01:00 2 Specifically, it is recommended to consider: Origin, availability and quality of information and data that was used for calculating SEC. ; Santonja, G.G. Or. To a scientist or engineer, the term energy is the potential of a system to perform work or to produce heat. It is derived from the formula for kinetic energy: Ek = ½ mv2, where m is the mass of the object in motion and v is its velocity. Introduction to Energy Density (By Weight and Volume) The Energy density of a battery is generally expressed in two ways, in the form of gravimetric energy density and as volumetric energy density . {\displaystyle E_{1}=E_{2}} The mathematical derivation of the conjugate depth equation can be a useful tool in understanding the derivation of the alternate depth equation, please refer to the above link for a more in-depth discussion of its derivation. Therefore, the formula of energy density is the sum of the energy density of the electric and magnetic field. By using SEC in the pulp and paper industry as an example, the results of this exploratory study show that although SEC is often used as an e-KPI in industry, the comparison is not always straightforward. Authors thank the anonymous reviewers for the comments. Generally, the more detailed benchmarking is, the more data is required [, This article was inspired by the authors’ own experiences of using SEC to research industrial energy efficiency and can, therefore, be said to be explorative in nature. The critical depth has a Froude number equal to one and corresponds to the minimum energy a flow can possess for a given discharge. The upstream depth of flow, y1 is 5.0 ft, the sluice gate opening is 1.0 ft, and the unit discharge is, [, SEC in the PPI has been used as an example to illustrate the differences in SEC. As mentioned previously, the pressure at locations 1 and 2 both equal atmospheric pressure in open-channel flow, therefore the pressure terms cancel out.