WCROC Dairy Baseline Energy Audit And Energy System Optimization

Transcription

1 And Energy System Optimization January 31, 2017 Eric Buchanan and Kirsten Sharpe Project funding provided by the University of Minnesota Initiative for Renewable Energy and the Environment (IREE)

2 TABLE OF CONTENTS Introduction... 1 Methods... 1 Natural Gas... 2 Water... 2 Electricity... 2 Data Logger... 4 Fuel... 6 Results... 6 Natural Gas... 6 Water... 7 Electricity Vehicle Fuel Discussion Appendix A: WCROC Milking Parlor Natural Gas Utility Bill Data Appendix B: Dairy Barn Electric Utility Meter Data Appendix C: Current Sensor Historical Locations Appendix D: Dairy Vehicle Fuel Usage Data Appendix E: WCROC Dairy Barn Water Flow Sensor Data Summarized by Month Appendix F: WCROC Dairy Barn Electric Current Sensor Data Summarized by Month Tables Table 1. Dairy Parlor sensor details... 5 Table 2. Summer Natural Gas Usage for Water Heater... 7 Table 3. Dairy Vehicle Fuel Usage Table 4. Dairy Pressure Washer Fuel Usage Table 5. WCROC Dairy Production, Table 6. WCROC Dairy Parlor Energy Usage, And Energy System Optimization Page i

3 Figures Figure 1. WCROC Dairy Barn Layout... 1 Figure 2. dairy utility room vacuum pump, vfd, and bulk tank compressors... 4 Figure 3. Dairy utility room n. gas water heater, pressure washer, and data logger box Figure 4. Dairy utility room - water mains, water softener, and milk house heater Figure 5. Dairy utility room data logger... 4 Figure 6. dairy utility room electric circuit breaker panels Figure 7. Total Parlor Natural Gas usage... 6 Figure 8. Dairy Total Daily Water Usage... 7 Figure 9. Individual Dairy Hot Water Daily Loads... 8 Figure 10. Total Water Usage on September 22, Figure 11. Hot Water Usage on September 22, Figure 12. Dairy Water Usage Figure 13. Dairy hot Water Load Distribution Figure 14. Dairy total Water Load Distribution Figure 15. Dairy Average Daily electricity Usage ( ) Figure 16. Electricity Usage & Milk Production Figure 17. Annual Dairy Electricity Usage Figure 18. WCROC Dairy Herd Size Growth Figure 19. Individual Dairy Electric Loads Figure 20. Compressor Efficiency Comparison Figure 21. Result of Adding a VFD to a Vacuum Pump Figure 22. Dairy Electric Load Distribution Figure 23. Dairy Electric Load Distribution (January) Figure 24. Dairy Electric Load Distribution (July) Figure 25. Dairy Total Energy Load Distribution (Ave) Figure 26. Dairy Total Energy Load Distribution (Jan) Figure 27. Dairy Total Energy Load Distribution (July) Figure 28. new dairy utility room with new thermal energy systems installed Figure 29. Dairy Herd Size, Figure 30. Dairy Milk Production, Figure 31. Dairy Parlor Energy Usage, Figure 32. Dairy Inputs per Cow per Day Figure 33. Dairy Inputs per gallon of milk And Energy System Optimization Page ii

4 INTRODUCTION The renewable energy team at the WCROC has undertaken the task of measuring energy usage in the dairy barn (milking parlor) with the goal of providing data to support several grants (the project team has successfully leveraged the initial IREE funding to obtain additional funding support for a much larger research effort within energy systems of dairy, swine, and cropping production systems at WCROC. The data can be used for Life Cycle Analyses (LCA), energy efficiency comparative studies, economic feasibility studies, renewable energy assessments including Net Zero calculations, and energy/agriculture policy development. A major goal of this project is to assess the energy used in a parlor that represents a typical Midwest dairy; and to also assess the energy used after adding energy efficiency measures and redesigning the parlor s thermal energy systems in a novel way to harvest and store energy. The WCROC dairy milks between 200 and 280 cows twice daily and is representative of a mid-size Minnesota dairy farm. The cows are split almost evenly between conventional and certified organic grazing herds and all cows spend the winter outside in confinement lots near the milking parlor. The WCROC dairy provides an ideal testing opportunity to evaluate and demonstrate the effect of on-site renewable energy generation and energy efficient upgrades on fossil fuel consumption and greenhouse gas emissions. The existing dairy equipment is typical for similarly sized dairy farms and included none of the commonly recommended energy efficiency enhancements such as a plate cooler, refrigeration heat recovery, or variable frequency drives (VFD) for pump motors when this project started. There are four general categories of energy usage in the WCROC dairy operation: thermal energy in the milking parlor provided by natural gas, Electrical energy in the milking parlor, small electric loads in pastures and out buildings, and fuel consumed by farm vehicles and tractors. Moreover, a large amount of water is used every day in the milking parlor primarily for cleaning. Water is also consumed by the cows from pasture water stations. METHODS The WCROC dairy barn was originally put into service in 1972 with a capacity of 60 tie stalls and space for maternity pens, calves, and young stock. When the dairy operation converted to grazing in the 1980 s, part of the barn was reconfigured to include a swing nine milking parlor. The rest of the barn including the 60 tie stalls is currently unused and not directly heated, but is still ventilated with fans in the summer. Figure 1 shows the barn configuration and dimensions of the actively used space. The parlor has gas and electric meters which measure the total consumption of natural gas and electricity FIGURE 1. WCROC DAIRY BARN LAYOUT And Energy System Optimization Page 1

5 within the barn. These meters were installed by the gas and electric utilities, Centerpoint Energy and Runestone Electric Association (REA), respectively. NATURAL GAS The gas meter is used for billing from the gas utility so the utility bills are the source of all gas usage data. No additional sensors were added to measure gas usage by individual loads so all gas data represents total usage per month. The parlor has three loads using natural gas: a 100 gallon commercial hot water heater (American Water Heater Co., model# CG32-100T88-4NOX, 85 KBtu/h, set at 170 F), a 250 KBtu/h forced air furnace (RUUPP Air Systems model# R1D 250-G10), and an LB White hanging garage heater. The raw data from the parlor gas bill is included in Appendix A. WATER Water usage was determined by installing flow and temperature sensors into the plumbing pipes feeding several specific loads as well as the total output from the water heater and the total water supply from the well. The selected sensor is made by Grundfos, model VFS 2-40, and measures both the flow rate up to 40 liters per minute and the temperature up to 100 C. The Grundfos VFS sensor measures the flow rate via vortex shedding behind a bluff body and produces a DC voltage proportional to the flow rate. It measures temperature via direct media contact and produces a DC voltage proportional to the temperature on a separate wire. The sensor requires a 5 VDC supply voltage. Other sensor specifications are included in Appendix C. ELECTRICITY The electric meter is no longer used for billing so the meter is manually read several times per month in the afternoon between milking times when electricity use is minimal. The number of kilowatt hours used since the last reading is divided by the number of days since the last reading to get an average daily energy usage for the period. All of the daily averages occurring during a particular calendar month are averaged together to get an average daily energy use for that month. This number represents the total average daily electric usage in the parlor. The raw data from reading the parlor electric meter is included in Appendix B. Several individual current sensors were installed to measure the electricity used by individual loads in the parlor. All current sensors are split core meaning they can snap around an existing wire without disconnecting that wire. The sensors are made by CR Magnetics, model CR9580, and produce an output from zero to 5 volts DC proportional to the AC current in the measured wire. The specifications for all sensors are included in Appendix C. And Energy System Optimization Page 2

6 The measured current is used to calculate the power consumed by the measured load using the following equation: ( PP = VV II pphaaaaaa PPPP Where: P = Power in Watts V = Voltage, line to ground, in volts I = Current, on one phase, in Amps Phase = Number of phases in the circuit, unitless PF = Power Factor, unitless An instantaneous power measurement requires instantaneous measurement of the current and voltage on all phases of the supply lines to every load measured. This would require 6 sensors on a three phase load and would make the number of sensors and data loggers needed for a typical barn cost prohibitive. Several reasonable assumptions can be made to simplify the measurement set-up without significantly sacrificing measurement accuracy. In the power equation it is important that the voltage is measured between one phase line and neutral. The voltage was measured once when the sensors were installed and is considered to remain constant. This is a reasonable assumption since supply voltage changes very little in a properly wired electrical system. Multiphase loads are assumed to be balanced meaning the same amount of current flows in each phase line. All multiphase loads measured in the dairy barn are AC motors which, theoretically, produce balanced loads. Assuming balanced loads means only one current sensor is required for each load and that the measured current is multiplied by the number of phase lines to calculate the total current. The final element in the power equation is the power factor (PF) which varies between zero and one. A purely resistive load like a heating element or incandescent light bulb has a power factor equal to one. An AC motor has a power factor that varies with the load on the motor; higher loading produces a higher power factor. The power factor accounts for the fact that some of the supplied power to a motor is not consumed by the motor, but instead creates the magnetic field that allows the motor to operate. Adding the power factor to the power equation allows the calculation of the power actually consumed by the motor. It is undesirable to operate motors at a low power factor so motors are typically sized so they are at least 70% loaded under normal conditions. A study by the U.S. Department of Energy ( shows that a typical motor loaded between 70% and 100% of its rated load will operate with a power factor generally between 80% and 90%. For this study the power factor of all motor loads was set at 85%. These assumptions allow a reasonable estimate of power consumption with a manageable amount of sensor and data logging equipment. Not every load in the dairy barn is measured. Loads that are not measured are small, occur in unused parts of the barn, or are not directly related to the milking operation. These loads fall into the category And Energy System Optimization Page 3

7 of miscellaneous loads and are estimated by subtracting all the measured energy use from the total energy use measured by the utility electric meter. Any errors in measured energy use, due to the assumptions made in the power equation, will also fall into the miscellaneous category since the utility electric meter accounts for variations in voltage, current, and power factor and measures each line phase. DATA LOGGER A Campbell Scientific data logger, model CR3000, and multiplexer, model AM32X, were used to monitor all of the sensors in the dairy barn. All sensors and the load they measure are listed in Table 1. Some sensors were moved over time because the load they were measuring proved to be insignificant or additional circuits were combined in one sensor for similar loads like lights and fans. No sensor changes were made after May of The history of each sensor is detailed in Appendix C. FIGURE 2. DAIRY UTILITY ROOM VACUUM PUMP, VFD, AND BULK TANK COMPRESSORS FIGURE 3. DAIRY UTILITY ROOM N. GAS WATER HEATER, PRESSURE WASHER, AND DATA LOGGER BOX. FIGURE 4. DAIRY UTILITY ROOM - WATER MAINS, WATER SOFTENER, AND MILK HOUSE HEATER. FIGURE 5. DAIRY UTILITY ROOM DATA LOGGER FIGURE 6. DAIRY UTILITY ROOM ELECTRIC CIRCUIT BREAKER PANELS. And Energy System Optimization Page 4

8 TABLE 1. DAIRY PARLOR SENSOR DETAILS Sensor Code Description Type Max Range Model T1F1 Mains inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T2F2 Water heater inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T3F3 Water heater outlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T4F4 Pressure washer inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T5F5 Milk sink hot water inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T6F6 Milk sink cold water inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T7F7 Tankwash hot water inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T8F8 Wash. machine hot inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T9F9 Wash. machine cold inlet temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T10F10 Bathroom cold temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T11F11 Bathroom hot temp & flow temp/flow 100C/10 gpm Grundfos VFS 2-40 T13 Milk sink water temp temp 200F CS 109-L40 T14 Parlor air temp temp 200F CS 110PV-L T15 Outdoor temp temp F CS 109-L40 T16 Utility room air temp temp F CS 109-L40 P1 Pressure washer outlet pressure Pressure 3000 psi Digikey ND C1 Furnace current 20A CR Magnetics CR C2 Conventional tank chiller current 50A CR Magnetics CR C3 Organic tank chiller current 50A CR Magnetics CR C4 Vacuum pump current 50A CR Magnetics CR C5 Pressure washer current 50A CR Magnetics CR C6 Pressure washer exhaust fan current 20A CR Magnetics CR C7 Milking parlor fans current 20A CR Magnetics CR C8 Milk line cleaning machine current 20A CR Magnetics CR C9 East side lights current 20A CR Magnetics CR C10 Cow stall receptacles current 20A CR Magnetics CR C11 Org. wash controller & agitator current 20A CR Magnetics CR C12 Tank room lights current 20A CR Magnetics CR C13 Parlor, UR, bathrm, office lights current 20A CR Magnetics CR C14 Washing machine current 20A CR Magnetics CR C15 Dryer current 50A CR Magnetics CR C16 Portable heaters current 50A CR Magnetics CR C17 Utility room fan current 20A CR Magnetics CR C18 Parlor fans NW current 20A CR Magnetics CR C19 East fans current 20A CR Magnetics CR C20 Office receptacles current 20A CR Magnetics CR And Energy System Optimization Page 5

9 The data logger was configured to monitor every sensor every 10 seconds then calculate an average value every 10 minutes from the 10 second readings and record the average in a table. The 10 minute average values were then downloaded to a laptop periodically and imported into an Excel spreadsheet for processing. Each 10 minute average value of electric current was converted into power using the power equation described above and multiplied by 1/6 of an hour to determine energy usage in kilowatt hours. The resulting 10 minute average energy usage values were then summed for each load each day to get a total energy usage per day. These values were then tabulated and averaged to get an average daily energy usage for each load during each month of the year. FUEL Several vehicles, tractors, and utility vehicles are used in the dairy operation at WCROC and all of them are refueled at centrally located fuel pumps (gas and diesel) on the farm site. A data sheet was developed and kept in a weather-proof box next to the fuel pumps. Vehicle operators were trained to enter the date, mileage/hours at fill up (from vehicle s gauge), and the number of gallons pumped each time a vehicle was refueled. Some vehicles are shared between the dairy and swine programs so farm managers provided an estimate of the percentage those vehicles are used for each program. The data sheets were collected periodically and summarized in a spreadsheet to determine the number of gallons per month each vehicle used that can be attributed to the dairy program. All the vehicles used for the WCROC dairy along with vehicle purpose, percentage of time vehicle is used for the dairy program, and the fuel type are shown in Appendix D. RESULTS NATURAL GAS Natural gas usage in the dairy parlor was obtained from historical utility records. The average monthly gas usage is shown in Figure 7 for years 2011 through Gas usage is fairly consistent year to year and exhibits the expected increase in usage during the winter months. The variation in usage from one year to the next is mostly during the winter months due to variations in weather. During FIGURE 7. TOTAL PARLOR NATURAL GAS USAGE summer months natural gas is only used by the water heater which provides a very consistent load. The average daily natural gas usage from the And Energy System Optimization Page 6

10 months of June, July, and August are shown in Table 2 and provide a good estimate of the natural gas usage attributable to water heating with any remaining usage attributable to parlor heating. The amount of natural gas used to heat water is estimated to be 6.3 therms per day based on this data. TABLE 2. SUMMER NATURAL GAS USAGE FOR WATER HEATER therms/day Average Jun Jul Aug Average WATER The total amount of water consumed in the milking parlor is measured by the total mains flow meter (T1F1 in Table 1), and the total amount of hot water used is measured by the water heater outlet flow meter (T3F3). The water heater inlet flow meter (T2F2) measures flow leaving the water softener of which the largest component enters the water heater, but also supplies cold soft water to a few hoses and utility sinks. This configuration allows the flow to small miscellaneous loads to be determined without additional flow meters. A similar situation exists for hot water going to a parlor wash down hose. The hot water flow to the hose is determined by subtracting all the measured hot water flows from the water heater outlet flow. Tabular data from all flow sensors is listed in Appendix E. The total amount of water used in the parlor, and the proportion that is heated, for the entire monitoring period is shown below in Figure 8. The average total water usage for the reporting period (August, 2013 through December 2016) was 1327 gallons per day. The proportion that was heated was 378 gallons per day. The water used in the pressure washer is heated by an onboard diesel burner not the water heater so the total hot water amounts shown do not include the pressure washer. The pressure washer used an average of 182 gallons of water per day over the entire FIGURE 8. DAIRY TOTAL DAILY WATER USAGE And Energy System Optimization Page 7

11 reporting period bringing the total hot water used in the parlor from all sources to 560 gallons per day. The energy-optimized upgrade to the dairy thermal energy systems provides heated water to a pressure washer so the diesel burner can be eliminated. Figure 9 shows water consumption for the primary individual loads in the parlor over the same period. FIGURE 9. INDIVIDUAL DAIRY HOT WATER DAILY LOADS Sensors measuring the hot and cold water usage by the washing machine failed in March of The average amount of water used by the washer from 6 months of data collection prior to the sensor failure was 71.3 and gallons per day for hot and cold water, respectively. The washing machine itself and the number of loads laundered daily have not changed during the reporting period so these average values are used in all charts showing how water usage is apportioned. In Figures 10 and 11, water usage during a typical day (September 22, 2013) is shown to visualize when different milking and cleaning activities are performed and how their individual demands for hot water interact. This interaction is important to determine the capacity of the on-demand (tankless) water heaters that eventually replaced the traditional storage tank water heater. The hot water usage schedule can also be used to better manage dairy tasks requiring hot water alleviating undue stress on a hot water heating system. The actual water use pattern could vary day to day, but is remarkably consistent since the same number of towel loads are run through the washing machine every day and the bulk tank and milking equipment wash cycles use the same amount of water regardless of how many cows are milked (assuming the number of milkings per day does not change). Variance in water usage is primarily due to changes in the human operated cleaning tasks like pressure washing and tank room wash down. And Energy System Optimization Page 8

12 FIGURE 10. TOTAL WATER USAGE ON SEPTEMBER 22, 2013 FIGURE 11. HOT WATER USAGE ON SEPTEMBER 22, 2013 Total water usage for the dairy barn, along with the total hot water usage, is shown for the data collection period in Figure 12. Figures 13 and 14 show how the hot water and total water usage is apportioned among the various cleaning tasks in the milking parlor, respectively. And Energy System Optimization Page 9

13 FIGURE 14. DAIRY WATER USAGE Figure 14 includes a miscellaneous category for cold water that includes all of the additional faucets in the dairy that are not individually measured. There is an old wash sink in the bulk tank room that is still used for cleaning chores. There are also a few taps in the old unused part of the barn that still get used periodically for clean-up chores. In other words, most of the water labeled miscellaneous is used for parlor clean-up, but cannot be explicitly tied to specific, measureable chores so it has been left in the miscellaneous category. FIGURE 12. DAIRY HOT WATER LOAD DISTRIBUTION ELECTRICITY Recordings of the dairy barn utility electric meter are included in Appendix B and plotted in Figure 15. Also shown in Figure 15 are several individual electric loads and a dashed line showing the total electricity usage recorded by a data logger. At the beginning of the monitoring period in 2013, the logger is only recording about 50% of the electricity used in the barn, but by November of 2014, logging efficiency FIGURE 13. DAIRY TOTAL WATER LOAD DISTRIBUTION reaches over 80% and remained there giving an average logging efficiency of 82% from that point to the end of the monitoring period. Monitoring every load would have been prohibitively expensive given the cost of data loggers and current sensors. The difference between the amount of electricity recorded at the utility meter and the total logged is identified as miscellaneous. And Energy System Optimization Page 10

14 Several initially monitored loads were found to be relatively small so sensors were moved to more promising loads when possible. Appendix C documents changes to sensor locations and collection parameters like phase and power factor. The last sensor location changes were made in May of 2015 and it is those final locations that are listed in Table 1. Tabular data from all current sensors is listed in Appendix F. The table is color coded showing which sensors are combined to get the totals for the categories shown in Figure 15. Milk cooling includes the compressor/condenser units for the two bulk tank chillers one for conventional milk and one for organic milk. The milk collection category includes the vacuum pump and milk controller which also controls the milk pump bringing milk from a collection jar in the parlor to the bulk tanks. The cleaning category consists of a clothes washer and dryer, pressure washer, and tank wash agitator. The other categories are self-explanatory, but specific sensor information indicating which sensors are combined is located in Appendix F. FIGURE 15. DAIRY AVERAGE DAILY ELECTRICITY USAGE ( ) A data logger malfunction resulted in lost data for the month of May and August through December of These areas are shown as blank in all tables and graphs. However, the total electricity used in the dairy barn is unaffected by the data logger or any sensor issues and always represents the true total electrical load in the barn. As part of the energy upgrades in the dairy barn, a new electrical service was installed resulting in removal of the utility meter. The meter had not been used for billing from the utility for many years so it was not replaced. Consequently, there is no total barn electricity data for June and July of 2016 while an egauge, model EG3000, revenue grade meter was procured and put into service. Total barn electricity monitoring resumed in August of 2016 using the egauge meter. And Energy System Optimization Page 11

15 In general, the patterns shown in Figure 15 are expected. Electricity used to collect and cool milk follows the ups and downs of milk production at the WCROC dairy which exhibits a peak in the winter and summer with more cows dried off in the spring and fall (Figure 16). Ventilation loads are highest in the summer and much smaller in the winter when the furnace fan is the primary load. One surprise was the milk house heater load which is very large in the winter. This load arises from two 1500 Watt electric heaters used to make sure water lines don t freeze in the poorly insulated utility room. Milk house heaters are a common solution to water freezing issues on Minnesota dairies, but it was not expected to be such a large load. This is an obvious place to start in efforts to reduce energy usage and costs. FIGURE 166. ELECTRICITY USAGE & MILK PRODUCTION Figure 17 shows the total annual electricity used at the WCROC dairy parlor over the monitoring period. Partial year logger data for years 2013 and 2016 were extrapolated to get an annual value. The total electricity used year to year is very consistent even though the herd size increased over the same time period (Figure 18). Most of the drop in electricity usage from 2013 to later years can be attributed to a variable frequency drive installed on the vacuum pump motor (Figure 21). FIGURE 177. ANNUAL DAIRY ELECTRICITY USAGE The most complete data is the period from May 2015 to April No sensor changes or data logger issues occurred during this FIGURE 18. WCROC DAIRY HERD SIZE GROWTH And Energy System Optimization Page 12

16 time frame so this is the best data to investigate seasonal patterns. Figure 19 shows the largest individual electric loads during this period. One observation that is evident from the graph is the relatively large load electric heaters can create. Another is the large difference between the two chiller compressors. The conventional tank uses an older reciprocating compressor while the organic tank has a newer scroll compressor. The conventional dairy herd at the WCROC accounts for about twice as much milk production as the organic herd so to get an accurate assessment of the different compressors the electrical loads need to be normalized to milk production (heat load on the compressor). FIGURE 19. INDIVIDUAL DAIRY ELECTRIC LOADS Dividing the average daily compressor load by the average daily milk production gives an estimate of compressor efficiency in energy units (kwh) per hundredweight (cwt) of milk. Averaging these values for each month yields a reciprocating compressor efficiency of 1.07 kwh/cwt, and a scroll compressor efficiency of 0.68 kwh/cwt a 36% improvement! The monthly variation in compressor efficiency is shown in Figure 20. Upgrading a reciprocating compressor to a scroll model also appears to be a good investment. A common recommendation for dairy producers to reduce energy costs is to employ a Variable Frequency Drive (VFD) with electric motors. VFD s save energy by varying a motor s speed to match the required load instead of just running at FIGURE 20. COMPRESSOR EFFICIENCY COMPARISON FIGURE 21. RESULT OF ADDING A VFD TO A VACUUM PUMP And Energy System Optimization Page 13

17 full speed all the time. A VFD was installed on the vacuum pump in the dairy parlor in September of A graph of the vacuum pump s electricity consumption during the month vividly shows the reduction in energy (Figure 21). The energy required by the pump to do the same work dropped over 75%, saving around $4 a day in electricity. This would lead to a simple payback in around 2.5 years a clear win for the producer. It should be noted that the VFD did fail and a replacement was necessary. So a producer may desire a warranty that extends up to the 2.5 year payback as a minimum. The largest single electric load in the dairy parlor is for milk cooling followed by ventilation. The WCROC dairy uses natural gas to heat water otherwise this would probably be a significant category. Electric heaters become a significant load in the winter enough so that they are still relevant when looking at annual averages. The average annual electric load distribution in the WCROC dairy parlor is shown in Figure 22. The distributions in January and July are shown in Figures 23 and 24, respectively, for a seasonal comparison. The pie charts for January and July show the FIGURE 22. DAIRY ELECTRIC LOAD DISTRIBUTION expected changes with electric heat becoming a factor in winter and ventilation almost eclipsing milk cooling in the summer. The WCROC dairy herd is outside all year round so ventilation might play an even more prominent role on farms housing cows indoors. Electricity used for lighting falls to almost half the winter value in summertime due to the much longer day in the northern latitudes of Minnesota. Pie charts provide a good way to look at electric loads in the dairy parlor and can help a producer decide where to start with energy efficiency improvements, but an even better way to determine which energy FIGURE 23. DAIRY ELECTRIC LOAD DISTRIBUTION (JANUARY) FIGURE 24. DAIRY ELECTRIC LOAD DISTRIBUTION (JULY) And Energy System Optimization Page 14

18 loads might yield the largest reductions is to combine all energy loads into one chart. By converting all energy loads to a common energy unit, like megajoules (MJ), loads using different fuels can be combined in one graph. Figures 25, 26, and 27 follow the same format as the electric load pie charts, but include water and parlor heating loads from natural gas and pressure washer heating from diesel fuel. FIGURE 265. DAIRY TOTAL ENERGY LOAD DISTRIBUTION (AVE) FIGURE 256. DAIRY TOTAL ENERGY LOAD DISTRIBUTION (JAN) With all energy sources graphed it is easy to see that parlor heating is the dominate load and that water heating is the next largest becoming the largest in summertime. It is also interesting that the diesel fuel used in the pressure washer only 5 gallons at a time is a pretty significant load, on par with milk collection or the electric heaters. Almost twice as much total energy is used on a daily basis in January as is used in July due to parlor heating, including electric heaters. The current parlor at the WCROC is an old tie stall barn built in the 1970 s with little insulation and the assumption that the housed cows would provide significant heat. Moreover, the furnace is configured so that FIGURE 277. DAIRY TOTAL ENERGY LOAD DISTRIBUTION (JULY) all air brought into the barn is fresh air from outside. This means cold outside air is continually being heated in the winter and exhausted through the ventilation fans and porous building envelope one of the least efficient ways to heat a building. If designing a new milking parlor, more in-depth consideration of the heating and ventilation systems will be time well spent. And Energy System Optimization Page 15

19 VEHICLE FUEL The final category of energy spent in the WCROC dairy parlor is fuel used in vehicles to support the milking operation. Farm workers logged the miles or hours from each vehicle s dashboard gauge as well as the number of gallons of gasoline or diesel fuel pumped each time they filled one of the WCROC livestock vehicles. This data was periodically collected and entered into a spreadsheet to tabulate how many gallons of fuel each vehicle used. Many vehicles are shared between the swine and dairy programs at the WCROC. Farm managers made an estimate of what proportion each vehicle was used for each program. Additionally, the farm managers estimated what percentage of time each vehicle was used purely for research purposes. Such purposes were defined as those that support research project goals, but wouldn t be necessary on a farm run only for profit. In this way, energy consumed on the farm, but not really needed to operate the farm was excluded so results of this study might be more readily applied to other commercial dairies. It was estimated that most vehicles at the WCROC are used from 60 to 80% of the time for research purposes. All of these usage estimates along with the annual fuel used in each vehicle is included in Appendix D. The amount of fuel each vehicle used in a year was multiplied by the percentage that vehicle was used for dairy tasks and then multiplied by one minus the percentage of time that vehicle was estimated to have been used for research tasks. This procedure resulted in the number of gallons attributable to normal dairy operations for each tractor, truck, or utility vehicle. Table 3 shows the annual fuel used for farm vehicles and Table 4 shows the annual fuel used in the dairy parlor pressure washer. Gallons of fuel are converted to megajoules by multiplying the number of gallons of a fuel by that fuel s Lower Heating Value (LHV). The LHV for gasoline is MJ/gal, and the LHV for diesel is MJ/gal as determined in an extension bulletin from Iowa State University ( TABLE 3. DAIRY VEHICLE FUEL USAGE TABLE 4. DAIRY PRESSURE WASHER FUEL USAGE And Energy System Optimization Page 16

20 Fuel usage for the year 2013 appears a little lower than later years because data recording did not start until May of Vehicle fuel use data was not combined into the pie charts for total energy use in the parlor because most vehicle use does not strictly apply to the milking parlor, but it is interesting to note that the size of the vehicle energy load is about 25% of the total dairy average daily energy load. This means the amount of energy used to fuel farm vehicles is similar to the amount used to provide hot water in the parlor (Figure 25.). DISCUSSION The overarching goal of this project in the WCROC dairy milking parlor was to understand how much energy is used to harvest milk, and where that energy is used, in the hope that a more energy efficient and, hopefully, more cost efficient way could be developed and implemented. It was further hoped that any new systems or improvements to existing ones would be a model for other dairy producers to consider changes in their operations. New thermal energy systems were designed around the idea of harvesting as much heat as possible from the milk before it reaches a bulk tank using a heat pump and heat exchanger (plate cooler). Thermal energy obtained from milk is stored in a large, super-insulated, thermal storage tank along with additional thermal energy from glazed, flat-plate solar thermal collectors. Plain water mixed with corrosion and scaling inhibitors is used as the storage medium. Stored thermal energy is dispatched as needed to preheat the parlor s well water with another heat exchanger after which it is heated to the desired temperature (>160 F for sanitizing and 120 F for other uses) by one of two electric, instant (tankless) water heaters. All of these components including a custom programmed control system were installed by Daikin Applied Americas, Inc., and are in the commissioning process. FIGURE 28. NEW DAIRY UTILITY ROOM WITH NEW THERMAL ENERGY SYSTEMS INSTALLED Figure 28 depicts the new energy equipment installed in a new utility room created in the dairy barn adjacent to the milking parlor. The far left side of the picture shows the insulated thermal storage tank (2200 gal) with a floor mounted expansion tank. The expansion tank uses a pressurized bladder to allow space for system fluid to expand as it is heated. Water is incompressible and expands as it is heated so if no space for expansion is provided, system pressure will increase until a pressure relief valve opens or something bursts. Moving to the right along the back wall in Figure 28 is the wall mounted electric pressure water, followed by the wall mounted electric instant water heaters. On the floor between the And Energy System Optimization Page 17

21 pressure washer and water heaters is a yellow plate and frame heat exchanger for preheating well water before it enters the water heaters. The cylindrical tank on a stand in the middle of the picture is a drain back tank for the solar thermal system. When the solar pump is not running, fluid in the separate solar loop (water and propylene glycol) drains back into this tank so it is not exposed to freezing outdoor temperatures. Just to the right of the drain back tank is another floor mounted heat exchanger for transferring heat from the solar loop to the thermal storage tank. The large white box to the right of the solar equipment is the 20 ton water to water heat pump which provides chilled water to the plate cooler for milk cooling and moves the collected heat from the milk to the storage tank. The control system and user interface are in the wall mounted gray box at the far right end of the room. Also on the far wall are VFD s for the pumps which are arrayed along the floor. There have been several problems during start-up including control system sensor issues and an improperly pressurized expansion tank that caused a leak in the thermal storage tank which required a repair weld. Control issues with the heat pump occurred due to short cycling of the heat pump compressor. Resolving this issue required the addition of a sensor to measure milk flow and modulate the heat pump accordingly. Correcting these problems has delayed the full implementation of the new energy systems meaning energy usage data from the new systems is not yet available. However, a huge amount of data has been collected from the milking parlor consisting of about two and a half million data points for each year of operation. This is a veritable treasure trove of information that will continue to provide insight for years to come. There are innumerable ways to analyze and present this data and innumerable specific details that can be examined. This report only provides a broad overview of energy use in the milking parlor with a few glimpses of specific loads and time frames. Energy usage data from different fuel sources was presented in the previous section. Here energy usage will be compared to milk production from the parlor. Table 5 lists the production figures for the WCROC dairy parlor for the years spanning the monitoring period, namely, 2013 through 2016, and Figures 29 and 30 show the same data in graphical form. It should be noted that all values concerning quantity of cows in this report refer to cows milked in the TABLE 5. WCROC DAIRY PRODUCTION, WCROC Dairy Production Year Cows Total Milk (lbs) Total Milk (gal) Ave. Milk (lbs/day) Ave. Milk (gal/day) Conventional 111 1,858, , Organic ,569 98, Total 189 2,706, , Conventional 104 1,751, , Organic , , Total 193 2,617, , Conventional 115 2,008, , Organic 104 1,113, , Total 219 3,121, , Conventional 129 2,281, , Organic , , Total 225 3,272, , And Energy System Optimization Page 18

22 parlor and do not include dry or sick cows. A comparison of Figures 29 and 30 shows that organic cows in the WCROC dairy do not produce as much milk per cow as the conventional cows. This difference is the result of cow management decisions which FIGURE 29. DAIRY HERD SIZE, FIGURE 30. DAIRY MILK PRODUCTION, are based on the high price of certified organic feed. Certified organic cows are fed or graze a ration higher in forage and fiber so less digestible nutrients are available to achieve maximum milk production. Table 6 lists the total energy usage from all sources in the parlor including water along with calculations of energy per unit of production (cows and gallons of milk). Total energy in this table and the following charts includes energy from diesel fuel used in the pressure washer as listed in Table 4. The average fuel use from years 2013 through 2015 was used to estimate the use in TABLE 6. WCROC DAIRY PARLOR ENERGY USAGE, Energy Usage Total Ave./cow/ Ave./gal Ave./cow/ Ave./gal Ave./cow/ day milk Total day milk Total day Total energy data from Table 6 is shown graphically in Figure 31 with electricity converted into megajoules so it can be directly compared to the other sources. In general, total energy use decreased almost 10% from 2013 to Almost 40% of that decrease is due to a decrease in electricity usage mostly attributable to a VFD installed on the vacuum pump. The remainder of the overall energy decrease is due WCROC Milking Parlor Energy Usage Ave./gal milk FIGURE 31. DAIRY PARLOR ENERGY USAGE, And Energy System Optimization Page 19 Total 2016 Ave./cow/ day Natural Gas (MJ) 504, , , , Electricity (kwh) 121, , , , Total Energy (MJ) 978, , , , Total Water (gal) 425, , , , Ave./gal milk

23 to reduced natural gas usage. Figure 32 displays energy use per cow per day for the monitoring period. Electricity use per cow steadily declined over the monitoring period probably due to the fact that the size of the milking herd increased, but no new equipment was needed and cows are still milked twice per day. This situation increases the time it takes for each milking, but the amount of energy and water needed for cleaning chores stays relatively constant. FIGURE 332. DAIRY INPUTS PER COW PER DAY FIGURE 323. DAIRY INPUTS PER GALLON OF MILK Looking at the same data, but on a per-gallon-of-milk basis, displays the same trends (Figure 33). The amount of natural gas used per gallon of milk in 2016 is a little more than half as much as was used in There are undoubtedly some weather effects in these numbers, but also the previously discussed economies-of-scale due to the fact that the dairy parlor is unchanged and requires the same amount of energy to heat, for a given outdoor temperature, regardless of how many cows are milked. The amount of electricity and water used per-gallon-of-milk stayed remarkably similar over the four year period. Analysis of this data will continue as work on more efficient energy systems in the dairy continues. Monitoring of energy use data will also continue as new systems are put into service and existing systems are improved. Other grants have been obtained to fund renewable electric energy systems to power the dairy that will leverage the work done for this grant to understand existing energy use patterns and install new thermal systems to use less energy. Acknowledgements The funding to support the work described in this report was provided by the Institute on Renewable Energy and the Environment (IREE) from the University of Minnesota. And Energy System Optimization Page 20

24 APPENDIX A: WCROC MILKING PARLOR NATURAL GAS UTILITY BILL DATA Month # of Days Therms Cost $/therm therm/day Month # of Days Therms Cost $/therm therm/day Jan $ Jan $ Feb $ Feb $ Mar $ Mar $ Apr $ Apr $ May $ May $ Jun $ Jun $ Jul $ Jul $ Aug $ Aug $ Sep $ Sep $ Oct $ Oct $ Nov $ Nov $ Dec $ Dec $ TOTAL 4,353 $ 3, TOTAL 5,194 $ 4, Jan $ Jan $ Feb $ Feb $ Mar $ Mar $ Apr $ Apr $ May $ May $ Jun $ Jun $ Jul $ Jul $ Aug $ Aug $ Sep $ Sep $ Oct $ Oct $ Nov $ Nov $ Dec $ Dec $ TOTAL 3,869 $ 2, TOTAL 4988 $ 3, Jan $ Jan $ Feb $ Feb $ Mar $ Mar $ Apr $ Apr $ May $ May $ Jun $ Jun $ Jul $ Jul $ Aug $ Aug $ Sep $ Sep $ Oct $ Oct $ Nov $ Nov $ Dec $ Dec $ TOTAL 4,787 $ 3, TOTAL And Energy System Optimization Page 21

25 APPENDIX B: DAIRY BARN ELECTRIC UTILITY METER DATA Meter was read manually until it was removed in May, 2016 for a new dairy electric service. An egauge revenue grade meter was installed in August of 2016 to record total parlor electricity usage. Date Reading Daily Ave. (kwh) Date Reading Daily Ave. (kwh) Summary 12-Sep Nov Jan Sep Nov Feb Sep Nov Mar Sep Nov Apr Sep Dec May Nov Dec Jun Mar Dec Jul May Dec Aug Jul Jan Sep Jul Jan Oct Aug Jan Nov Aug Feb Dec Aug Feb Nov Aug Feb Dec Aug Feb Jan Aug Mar Feb Aug Mar Mar Aug Mar Apr Aug Mar May Aug Apr Jun Sep Apr Jul Oct Apr Aug Nov Apr Sep Nov May Oct Nov May Nov Nov May Dec Nov Jun Jan Dec Jun Feb Dec Jun Mar Dec Jul Apr Dec Jul May Jan Jul Jun Jan Jul Jul Feb Aug Aug Feb Aug Sep Feb Aug Oct Feb Aug Nov Feb Sep Dec Mar Sep Jan Mar Oct Feb Mar Oct Mar Mar Oct Apr Apr Nov May Apr Dec Jun Apr Dec Jul Apr Dec Aug May Jan Sep May Jan Oct May Jan Nov May Feb Dec Jun Feb Data from egauge 9-Jun Mar Jun Mar Jun Mar Jun Apr Jul Apr Jul Apr Jul Apr Aug May Aug May Sep Sep Oct Oct Oct And Energy System Optimization Page 22

26 APPENDIX C: CURRENT SENSOR HISTORICAL LOCATIONS Current sensors were relocated twice; once in May of 2014 and once in May of The highlighted cells below indicate which sensors were affected by any change. Initial positions in SEP 2013 Positions as of MAY 2014 Positions as of MAY 2015 Sensor Code Location Description Description Description C1 UR Furnace Furnace Furnace C2 UR Conv. comp. & condenser Conv. comp. & condenser Conv. comp. & condenser C3 UR Organic comp. & condenser Organic comp. & condenser Organic comp. & condenser C4 UR Vacuum pump Vacuum pump Vacuum pump C5 UR Pressure washer Pressure washer Pressure washer C6 UR PW exhaust & tank rm fans PW exhaust & tank rm fans PW exhaust & tank rm fans C7 UR Fly sucker Scraper Milking parlor fans C8 TR Milk controller Milk controller Milk controller C9 P cow gate East side lights East side lights C10 TR Tank wash Org. Barn elec. outlets (fans) Barn elec. outlets (fans) C11 TR Tank wash Conv. Organic tank wash & agitator Organic tank wash & agitator C12 TR Tank truck Org. Lights (UR, bathroom, office) Lights (tank room) C13 P Lift pump Lift pump Lights (parlor, UR, bath, off.) C14 TR Washing machine Washing machine Washing machine C15 TR Dryer Dryer Dryer C16 UR Milk house heaters Milk house heaters Milk house heaters C17 P Utility room fan Utility room fan Utility room fan C18 P Parlor fans NW Parlor fans NW Parlor fans NW C19 P fans W Fans (east side) Fans (east side) C20 P Milk pump Office outlets Office outlets UR=Utility room, TR=Tank room, P=Parlor The following table shows the labels used for each of the three indicated sensor set-ups along with the line to neutral voltage, how many phases the measured circuit included, and the power factor assumed for that load. These values were used to calculate the power and energy usage for each load along with the measured AC current. And Energy System Optimization Page 23

27 Original Sensor Locations SEP 2013 Sensor Code Location Description Voltage Phase Sensor Locations as of May, 2014 Sensor Locations as of May, 2015 Power Factor Description Voltage Phase Power Factor Description Voltage Phase C1 UR Furnace Furnace Furnace C2 UR Conv. comp. & condenser Conv. comp. & condenser Conv. comp. & condenser C3 UR Organic comp. & condenser Organic comp. & condenser Organic comp. & condenser C4 UR Vacuum pump Vacuum pump Vacuum pump C5 UR Pressure washer Pressure washer Pressure washer C6 UR PW exhaust & tank rm fans PW exhaust & tank rm fans PW exhaust & tank rm fans C7 UR Fly sucker Scraper Milking parlor fans C8 TR Milk controller Milk controller Milk controller C9 P cow gate East side lights East side lights C10 TR Tank wash Org Barn elec. outlets (fans) Barn elec. outlets (fans) C11 TR Tank wash Conv Organic tank wash & agitator Organic tank wash & agitator C12 TR Tank truck Org Lights (UR, bathroom, office) Lights (tank room) C13 P Lift pump Lift pump Lights (parlor, UR, bath, off.) C14 TR Washing machine Washing machine Washing machine C15 TR Dryer Dryer Dryer C16 UR Milk house heaters Milk house heaters Milk house heaters C17 P Utility room fan Utility room fan Utility room fan C18 P Parlor fans NW Parlor fans NW Parlor fans NW C19 P fans W Fans (east side) Fans (east side) C20 P Milk pump Office outlets Office outlets Power Factor And Energy System Optimization Page 24

28 CR Magnetics AC Current Sensor Specifications And Energy System Optimization Page 25

29 Grundfos VFS 2-40 QT temperature and Flow Sensor Specifications And Energy System Optimization Page 26

30 And Energy System Optimization Page 27