The effect of demand, tank parameters, and pumping stations on energy use in municipal drinking water distribution systems

Two of the indicators of the UN Millennium Development Goals ensuring environmental sustainability are energy use and per capita carbon dioxide emissions. The increasing urbanization and increasing world population may require increased energy use in order to transport enough safe drinking water to communities. In addition, the increase in water use would result in increased energy consumption, thereby resulting in increased green-house gas emissions that promote global climate change. The study of multiple Municipal Drinking Water Distribution Systems (MDWDSs) that relates various MDWDS aspects--system components and properties--to energy use is strongly desirable. The understanding of the relationship between system aspects and energy use aids in energy-efficient design. In this study, components of a MDWDS, and/or the characteristics associated with the component are termed as MDWDS aspects (hereafter--system aspects). There are many aspects of MDWDSs that affect the energy usage. Three system aspects (1) system-wide water demand, (2) storage tank parameters, and (3) pumping stations were analyzed in this study. The study involved seven MDWDSs to understand the relationship between the above-mentioned system aspects in relation with energy use. A MDWDSs model, EPANET 2.0, was utilized to analyze the seven systems. Six of the systems were real and one was a hypothetical system. The study presented here is unique in its statistical approach using seven municipal water distribution systems. The first system aspect studied was system-wide water demand. The analysis involved analyzing seven systems for the variation of water demand and its impact on energy use. To quantify the effects of water use reduction on energy use in a municipal water distribution system, the seven systems were modeled and the energy usage quantified for various amounts of water conservation. It was found that the effect of water conservation on energy use was linear for all seven systems and that all the average values of all the systems' energy use plotted on the same line with a high R 2 value. From this relationship, it can be ascertained that a 20% reduction in water demand results in approximately a 13% savings in energy use for all seven systems analyzed. This figure might hold true for many similar systems that are dominated by pumping and not gravity driven. The second system aspect analyzed was storage tank(s) parameters. Various tank parameters: (1) tank maximum water levels, (2) tank elevation, and (3) tank diameter were considered in this part of the study. MDWDSs use a significant amount of electrical energy for the pumping of water from low elevations (usually a source) to higher ones (usually storage tanks). The use of electrical energy has an effect on pollution emissions and, therefore, potential global climate change as well. Various values of these tank parameters were modeled on seven MDWDSs of various sizes using a network solver and the energy usage recorded. It was found that when averaged over all seven analyzed systems (1) the reduction of maximum tank water level by 50% results in a 2% energy reduction, (2) energy use for a change in tank elevation is system specific, and (2) a reduction of tank diameter of 50% results in approximately a 7% energy savings. The third system aspect analyzed in this study was pumping station parameters. A pumping station consists of one or more pumps. The seven systems were analyzed to understand the effect of the variation of pump horsepower and the number of booster stations on energy use. It was found that adding booster stations could save energy depending upon the system characteristics. For systems with flat topography, a single main pumping station was found to use less energy. In systems with a higher-elevation neighborhood, however, one or more booster pumps with a reduced main pumping station capacity used less energy. The energy savings for the seven systems was dependent on the number of boosters and ranged from 5% to 66% for the analyzed five systems with higher elevation neighborhoods (S3, S4, S5, S6, and S7). No energy savings was realized for the remaining two flat topography systems, S1, and S2. The present study analyzed and established the relationship between various system aspects and energy use in seven MDWDSs. This aids in estimating the amount of energy savings in MDWDSs. This energy savings would ultimately help reduce Greenhouse gases (GHGs) emissions including per capita CO 2 emissions thereby potentially lowering the global climate change effect. This will in turn contribute to meeting the MDG of ensuring environmental sustainability.

Gender on the Range: Feminine Strategies in the 1913 Michigan Copper Strike

In the autumn of 1913, a small, remote Michigan mining community attracted national attention as miners and management found themselves embroiled in a conflict that would prove no easy victory for either side. The strike came as a shock to management, who, with the help of a nearly perfected paternal system, had come to expect a generally docile and compliant workforce. But what was even more shocking was the involvement of the miners’ wives in the strike effort, and the lengths they went to in order to keep men from crossing the picket line. This paper focuses on that effort, arguing that the women of the Michigan copper country developed strike strategies that were derived from their domestic experience, and justified their involvement through maternal arguments. However, these public actions allowed the management to disregard the respect and courtesy generally given to the domestic sphere as police and private agents perpetrated a number of home invasions in an attempt to break the strike. The involvement of women in male dominated labor disputes (mining, steel productions) has been largely ignored in the literature due to their indirect connection to the company as wives and not workers. This paper seeks to remedy this gap, and gain a better understanding of that indirect relationship. Sources include newspaper articles, private correspondence, public investigation records, and oral histories, found largely in the Michigan Tech Archives and Copper Country Historical Collections, Michigan Technological University, Michigan.

INVESTIGATING THE ROLE OF THE CONTACT LINE IN HETEROGENEOUS NUCLEATION WITH HIGH SPEED IMAGING

While nucleation of solids in supercooled liquids is ubiquitous [15, 65, 66], surface crystallization, the tendency for freezing to begin preferentially at the liquid-gas interface, has remained puzzling [74, 18, 68, 69, 51, 64, 72, 16]. Here we employ high-speed imaging of supercooled water drops to study the phenomenon of heterogeneous surface crystallization. Our geometry avoids the "point-like contact" of prior experiments by providing a simple, symmetric contact line (triple line defined by the substrate-liquid-air interface) for a drop resting on a homogeneous silicon substrate. We examine three possible mechanisms that might explain these laboratory observations: (i) Line Tension at the triple line, (ii) Thermal Gradients within the droplets and (iii) Surface Texture. In our first study we record nearly perfect spatial uniformity in the immersed (liquid-substrate) region and, thereby, no preference for nucleation at the triple line. In our second study, no influence of thermal gradients on the preference for freezing at the triple line was observed. Motivated by the conjectured importance of line tension (τ) [1, 66] for heterogeneous nucleation, we also searched for evidence of a transition to surface crystallization at length scales on the order of δ ∼ τ/σ, where σ is the surface tension [14]; poorly constrained τ [49] leads to δ ranging from microns to nanometers. We demonstrate that nano-scale texture causes a shift in the nucleation to the three-phase contact line, while micro-scale texture does not. The possibility of a critical length scale has implications for the effectiveness of nucleation catalysts, including formation of ice in atmospheric clouds [7].