Waste, Just Another Resource: A Case for Waste Water

Transcription

1 Energy Engineering ISSN: (Print) (Online) Journal homepage: Waste, Just Another Resource: A Case for Waste Water David Goodman, Arash Edalatnoor & Michael Cooprider To cite this article: David Goodman, Arash Edalatnoor & Michael Cooprider (2016) Waste, Just Another Resource: A Case for Waste Water, Energy Engineering, 113:3, To link to this article: Published online: 11 Mar Submit your article to this journal Article views: 174 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 28 June 2016, At: 19:04

2 71 Waste, Just Another Resource: A Case for Waste Water David Goodman, PhD, CEA Arash Edalatnoor Michael Cooprider ABSTRACT Companies around the world are looking for ways to save money. Industries implement more efficient lighting, HVAC, and automation systems into their processes to save energy, but industries are also looking for methods to produce energy as a byproduct in their processes. One way industries can produce energy is by installing waste water recovery systems to their treatment process. This article focuses on implementing micro hydro systems at two facilities. The first facility has two possible equipment locations and is located at a pharmaceutical facility in northern Indiana (Site 1). Considering cost and energy savings calculations, Site 1, will have a five or eight year equipment payback time depending on location without incentives. The other location is a paper mill facility also in northern, Indiana (Site 2). Under favorable conditions, Site 2 will have a seven year equipment payback without incentives. The remainder of this article will introduce waste water and how it can be applied to each of the three locations mentioned. Analysis of data from each site will be provided through calculations. The calculations and analysis lead to the recommendation for each site and its corresponding payback period and provide a framework for future hydroelectric feasibility studies. Keywords: Waste, Energy, Hydro, Hydroelectric, Energy Efficiency, Water, Resource. INTRODUCTION We are all well-aware of urban cities and industries contaminating water with their waste products. It is important to not only look for ways to reduce this waste, but also to use the waste water for other beneficial

3 72 Energy Engineering Vol. 113, No purposes. To that end, it is desirable for corporations to treat waste water in order to turn it back into a usable resource. The concept of treating waste water is a fairly recent one, developed in the late 19th century to reduce water pollution in large cities [4]. In addition to municipal waste water treatment, many industrial facilities produce waste water that must be treated before being released back into the surrounding environment or re-used within the facilities. Waste water can provide a potential energy source for industries. Waste water energy recovery equipment can be installed to produce electricity. This electricity can then be used to power various facility devices which can save corporations money over a period of time. BACKGROUND Research was conducted at two sites. Site 1 is a pharmaceutical facility in northern, Indiana; it has two locations suitable for a hydroelectric installation, a pump location and a river location. The Site 2 facility is a paper mill located in northern, Indiana. Both facilities were looking for ways to convert waste streams into green energy. An on-site industrial energy audit found, among other things, that water was a major waste stream. This investigation examined the mechanical and electrical designs, installation, control and operation strategies, utility interconnection, and financial/regulatory issues at an initial feasibility level. The results and energy savings have been shown for both cases. METHODS A common way to create energy from waste water is through hydroelectricity. For this study researchers determined that the micro hydra system would be the most suitable hydroelectric generation method. This is due to micro hydro systems being a smaller scale method of generating hydroelectric power from the gravitational force of water. Such systems are capable of producing up to 100 kw of electricity [2]. Typically these systems are utilized in remote residential applications. The system s intake device is mounted at the top of a waterfall or the highest point of a river. The highest point is chosen in order to get the maximum gravitational force as it flows down to a turbine and generator. However the principles are valid for any system in which the outtake of the waste water

4 73 system is at least ten feet above the intake of the natural setting or municipal facility. The initial site visits were used to become familiar with the sites and to evaluate system installation, layout, operation, and equipment locations. Drawings for the piping routes and associated structures were also collected to determine elevations for head calculations. The drawings were also used to evaluate potential sites and issues for the micro hydro system components. The evaluations and calculations were based on recommended practices from several books and papers listed in the reference section, as well as communication with equipment suppliers [1, 2, 5, 7, 8, and 10]. DATA AND RESULTS An initial walkthrough of Site 1 revealed two potential locations for the micro hydro application. Once the selected location of each micro hydro system was determined, the address was entered into an online tool to determine elevation changes along the piping routes [9]. The tool was developed to create biking routes and uses satellite maps and terrain maps to provide an excellent visual of the proposed piping runs. The final location was determined primarily on available head. But the determination also included the following criteria: space for new equipment, ease of installation, impact on current production, and future expansion plans. The power potential of any hydro project is directly proportional to the head and flow of the water. For each location the head was calculated based on elevation changes from satellite images and elevation website data [9]. The elevation at the pump location was ft. (183 m) and ft. (162) at the river location. The piping distance is 0.1 mile (161 m). The difference of the two gross heads, or elevation difference, was 68.8 feet (21 m). The same process was used to select the location of the micro hydro system at Site 2. The head was again calculated based on elevation changes from the satellite image and elevation website data [9]. The elevation at the pump location was ft. (208 m) and ft. (203) on the river. The distance for piping was 0.1 mile (161 m). The difference of the two gross heads, or elevation difference, was 16.4 feet (5 m). Based on the flow data provided by each plant and the head calculations, the power and energy capacity at the two sites was determined. Table 1 show the power and energy data that were calculated. The calcu-

5 74 Energy Engineering Vol. 113, No lations show that a micro hydro system at the river location of site 1 can provide 3 to 6 times the power and energy of the pump location of site 1 when commercially available equipment is considered. Table 1. Power & Energy Calculations At site 2, since the flow is essentially constant, there is no Min and Max defined in table 1. Vendors were contacted and supplied with information from Table 1, based on discussions of several factors which will be discussed in the equation and assumptions section. Equipment was specified for each location. Table 2 shows the estimated cost of equipment at each location. The US Environmental Protection Agency is considering a carbon cap and trade system similar to the system used in the European Union. Currently carbon credits are voluntary in the US and trade for five to forty dollars each, while the mandated credits in the EU sell for thirty dollars each. Based on energy savings alone, the payback for the 1.5 kw system at the pump locations is 8 to 14 years, with a payback of 5 to 10 years for the 9 kw system at the river location. If we consider future carbon credit regulations or the market value of purchasing carbon credits, the payback for the 1.5 kw and 9 kw systems based on both energy savings and the EU price for carbon credits is shortened to 7 to 12 years and 4 to 8 years, respectively [11].

6 75 Table 2. Equipment Costs Table 3. Energy & Environmental Value EQUATIONS AND ASSUMPTIONS Formula 1 was used to calculate the theoretical amount of power available to a hydroelectric system at each location using averaged measurement data. These calculations are suitable for determining feasibility, but more detailed equations such as those detailed by Awasthi are needed for design [1]. Flow measurements were taken 1-2 times per day in Gallons per Day and converted to cubic meters per second. The averaged converted flow reading at the Site 1 Pump location has been used in the following example calculation. The calculations were repeated for all measurements in a spreadsheet and tabulated. In this example, the volumet-

7 76 Energy Engineering Vol. 113, No ric flow rate for the facility would be m3/s. The total power then equals the specific weight multiplied by the discharge and head change: Pw =ρ g Q H Pw= m3s 6.5 m Pw=5.53 kw (1) where Q is the flow capacity measured in m3/s, H is the head differential with units of m, and the specific weight (ρ g) is measured in kn/m3. This gives final units for power in kw. The data for converted flow are given in Table 1. After solving for the total power produced by the turbine, the annual energy for the water system can be calculated using Formula 2: Annual Energy=Pw 8760 CF Annual Energy=5.53 kw 8760 h 0.96 Annual Energy=46,505 kwh (2) where the total power in kw is multiplied by 8,760, or the number of operating hours in a year, and CF, the capacity factor. The capacity factor is the ratio of actual output to potential output of the system over a period of time. The capacity factor, in an industrial setting can be highly dependent on production time and production capacity in the system. Because the plant is operating 50 of 52 weeks per year, the capacity factor has been calculated to be Based on data provided by the vendor, the efficiency of the turbine has been assumed to be 60% [5, 10]. The annual energy value can be calculated using Formula 3, which also illustrates a sample calculation for the converted flow reading and includes turbine losses: Annual Energy Value=Usage Charge Annual Energy Efficiency Annual Energy Value =$0.05/kWh 46,505 kwh 0.6 Annual Energy Value =$1,395 (3) In this example, the usage charge for this system is $0.05/kWh. The utility cost is based on data from the past 25 energy audits performed by the Industrial Energy Assessment (IAC) center at IUPUI. Therefore, if the flow rate were constant at the measured value, the total annual energy

8 77 value of a properly sized hydroelectric turbine system is $1,395. Once the equipment cost and annual energy value has been calculated, the equipment s simple payback period can be determined by using Formula 4: Payback =Total Equipment CostAnnual Energy Value Payback =$ 10,100$1,395 Payback yrs=7.24 years (4) In this example, payback has been calculated using the equipment costs from Table 2 and the calculated annual energy value for one converted flow reading. Payback for this equipment at Site 1 is 7.24 years, which is relatively high. This procedure has been repeated for all locations and devices, and the payback data are given in Table 3. SYSTEM DESIGN A grid-tied hydroelectric system will require some or all of the following components: turbine, generator, charge controller, load resistor, inverter, cable, and protective devices. The Site 1 and Site 2 locations both have low head ratings and high volume ratings which characterize either crossflow or reaction turbines. To maximize power from commercially available equipment, Kaplan axial flow reaction turbines were selected for each location. If DC voltage is desired, a permanent magnet generator will reduce maintenance. If an AC voltage is desired, an induction generator will automatically synchronize to the grid. The choice of DC versus AC depends on the tradeoff of the price of an inverter versus the price of protective relays and fuses as well as distance to the grid. A DC system was selected for the pump location at Site 1 & 2 and an AC system for the river location at Site 1 due to distance from the grid. Since this was a feasibility study, we did not complete a detailed design and select the specific inverter or protective device. The costs for these devices were estimated for payback calculations. A charge controller and load resistor are necessary to protect the generator when the grid is offline, similarly the device/component level design was outside the scope of this project and since the cost was considered negligible it was not included in the payback calculation. The IEEE-1547 suggests several protective device functions to protect the equipment and personnel and for proper connection to the grid; the most

9 78 Energy Engineering Vol. 113, No important of these include over/under voltage, over/under frequency, over current, and synchronization check. Although specific protective device design was outside the scope, the cost is significant and an estimate was included in the payback calculations. The pump location at Site 1 & 2 had an extremely low head of two meters, so based on handbook turbine curves crossflow and Kaplan-type turbines were selected [7, 8]. It was determined that the turbine cost for 400 W from two crossflow turbines is approximately $4,000, while the cost for 1.5 kw from three Kaplan turbines is approximately $9,000. Three LH Micro-Hydro Generators from Energy Systems and Design or similar generators were proposed and quoted [5]. These generators would provide around 550 W each at DC voltages from 12 to 120 V. They could be installed separately, but if all three were to be installed, a mounting plate that evenly divides the flow should be installed first. The river location at Site 1 had a moderately low head, so we initially considered Francis and Kaplan-type turbines [7, 8]. Subsequent research and discussions with vendors eliminated the Francis turbine [5, 10]. Unlike the pump locations, the river location was designed for dual turbines to take advantage of the average and maximum flow rates; the system cost per unit of energy declines as the size increases, and more space is available to make dual turbines feasible. The river location design utilized a primary turbine/generator that produces 5.5 kw and a secondary turbine/generator that produces 3.5 kw. The generators are AC inductiontype and can provide 120 to 480 V AC in single or three phase configurations. GOVERNMENT REGULATIONS AND INCENTIVES Hydroelectric systems are classified as renewable, so government (state and federal) incentives may be available to reduce project costs and improve payback periods. Additionally, as a source of power they may be regulated. Both possibilities should be investigated before moving from feasibility design to detailed design. The Federal Energy Regulatory Commission requires hydroelectric projects to be licensed; the process is detailed at the referenced website and must be initiated before construction [6]. The federal government has several options to reduce costs by 10-50%, such as: grant programs, corporate depreciation, corporate tax credits, corporate tax deductions, and

10 79 loan programs [3]. Indiana provides few incentives for hydroelectric systems. However, the system will be 100% property tax exempt, qualifies for net metering (but we do not recommend it for these applications because the electricity generated is far less than the facilities use), and may be eligible for a 10% tax credit on the micro turbine [3]. CONCLUSION This investigation examined the feasibility of using waste process water for three micro hydro systems after waste water treatment. Systems were selected for two sites and simple payback due to energy savings has been calculated. In both cases, under the most favorable conditions the payback of the equipment (not including installation costs) are greater than eight years for the pump locations and greater than five years for the river location (without incentives). Although the payback period is generally to long for non-government entities, the concept of everything is a resource is always worthy and will keep perception open to nonstandard energy savings opportunities. References [1] Awasthi, S. R., Prasad, V., and Rangnekar, S. Demand Based Optimal Performance Of A Hydroelectric Power Plant. International Journal of Advanced Research in Engineering and Technology, Vol. 4(7), 2013, [2] BC Hydro Handbook for Developing Micro Hydro in British Columbia. Retrieved from [3] DSIRE Indiana Incentives for Renewable Energy. Retrieved from [4] San Diego History and background of wastewater, the city of San Diego. Retrieved from [5] Energy Systems and Design (ESD) Manufacturer of LH-1000 and other Turbines. Canada. Retrieved from [6] Federal Energy Regulatory Commission Licensing Information. Retrieved from [7] Fritz, Jack Small and Mini Hydropower Systems. McGraw-Hill. [8] Monition, L. et. al Micro Hydroelectric Power Stations. Wiley & Sons. [9] Route Planning and Geo-Analysis Tool Retrieved from org/elevation/ [10] St. Onge Environmental Engineering (SEE) Microhydro Turbine Supplier and Information. Retrieved from [11] US Environmental Protection Agency Retrieved from gov/

11 80 Energy Engineering Vol. 113, No ABOUT THE AUTHORS Dr. David Goodman, CEA, is an Assistant Professor of Engineering Technology at Indiana University-Purdue University at Indianapolis (IUPUI). He earned his B.S. Electrical Engineering degree from Purdue University, MS (Mechanical Engineering Technology, 2005) from Purdue University, and Ph.D. (Engineering Technology, 2009) from Purdue University. He is currently teaching at IUPUI. His interests are in energy efficiency, sustainability, and renewable energy systems. Dr. David Goodman has over a decade in industry as an electrical power and controls engineer and a medium voltage electrical engineer and he currently is assistant director of the Indiana Industrial Assessment Center (IAC). Dr. David Goodman may be reached at dwgoodma@iupui.edu. Arash Edalatnoor is an MS graduate of the Mechanical Engineering Department, IUPUI. He has two years experience at the IAC and earned a USDOE certificate in energy assessment. Arash Edalatnoor may be reached at aedalatn@iupui.edu. Michael Cooprider is an MS graduate student in the Engineering Technology Department, IUPUI. He may be reached at mcooprid@iupui. edu.