CAL POLY SUPER PROJECT ELECTRICAL POWER ANALYSIS OF CAL POLY ORGANIC FARM

Transcription

1 CAL POLY SUPER PROJECT ELECTRICAL POWER ANALYSIS OF CAL POLY ORGANIC FARM by Alexander Liang Senior Project ELECTRICAL ENGINEERING DEPARTMENT California Polytechnic State University San Luis Obispo 2008

2 ii TABLE OF CONTENTS Section Page Acknowledgements... v Abstract...vi I. Introduction... 1 II. Background... 3 III. Requirements and Design... 8 Loads at the Farm... 9 Electrical Distribution System IV. Simulation and Electric Power Measurement ETAP PowerSight PS V. Using SuPER Systems at the Farm Keeping the Farm AC Converting the Farm to DC SuPER Field Testing VI. Conclusion VII. Bibliography Appendices Page A: Parts List and Costs B: Details of Electrical Components C: ETAP Load Flow Diagrams D: Photographs of PS3000 Installation E: Facilities Service Request Description F: Additional PowerSight PS3000 Data G: Analysis of Senior Project Design... 78

3 iii LIST OF TABLE AND FIGURES Tables Page Table I: Organic Farm Loads Table II: Packing Shed Load Schedule Table III: Straw Bale House Load Schedule Table IV: Storage Shed Load Schedule Table V: Greenhouse Load Schedule Table VI: Summary of Energy Usage Table VII: Various Power Demand Scenarios Table VIII: Summary of Power Usage Table IX: Actual Power Demand Scenarios Table X: Professional Solar Installation Cost Estimates Table XI: Packing Shed DC Replacement Loads Table XII: Straw Bale House DC Replacement Loads Table XIII: Storage Shed DC Replacement Loads Table XIV: Greenhouse DC Replacement Loads Table XV: Other DC Replacement Loads Table XVI: Packing Shed DC Load Schedule Table XVII: Straw Bale House DC Load Schedule Table XVIII: Storage Shed DC Load Schedule Table XIX: Greenhouse DC Load Schedule Table XX: Summary of DC Energy Usage Table XXI: Recommended DC Replacement Loads Parts List and Costs Table XXII: Circuit Breaker Details Table XXIII: Transformer Details Table XXIV: Disconnect Switch Details Figures Page Figure 1: Cal Poly Campus Map... 3 Figure 2: Organic Farm Aerial Photograph... 4 Figure 3: Monthly Electrical Usage... 8 Figure 4: Organic Farm Single Line Diagram Figure 5: Main Circuit Breaker Panel Layout Figure 6: Inside Panel Circuit Breaker Layout Figure 7: Load Flow Analysis Figure 8: PowerSight PS3000 Datalog Settings Figure 9: PowerSight PS3000 Connection Figure 10: Power Consumption for Thursday 02/28/ Figure 11: Power Consumption for Friday 02/29/

4 Figure 12: Power Consumption for Saturday 03/01/ Figure 13: Power Consumption for Sunday 03/02/ Figure 14: Power Consumption for Monday 03/03/ Figure 15: Power Consumption for Tuesday 03/04/ Figure 16: Power Consumption for Wednesday 03/05/ Figure 17: Power Consumption for Thursday 03/06/ Figure 18: Power Consumption for Friday 3/7/ Figure 19: Proposed Location of Packing Shed SuPER Unit Figure 20: Proposed Location #1 of Straw Bale House SuPER Unit Figure 21: Proposed Location #2 of Straw Bale House SuPER Unit Figure 22: Proposed Location of Storage Shed SuPER Unit Figure 23: ETAP Load Flow - Min. Power Figure 24: ETAP Load Flow - "Daytime Working 1" Figure 25: ETAP Load Flow - "Daytime Working 2" Figure 26: ETAP Load Flow - "Lunchtime 1" Figure 27: ETAP Load Flow - "Lunchtime 2" Figure 28: ETAP Load Flow - "Evening" Figure 29: PowerSight PS3000 Installation Figure 30: Current Probe Connections Figure 31: Voltage Probe Connections Figure 32: PS3000 Operating Figure 33: Reactive Power Consumption for Thursday 02/28/ Figure 34: Reactive Power Consumption for Friday 02/29/ Figure 35: Reactive Power Consumption for Saturday 03/01/ Figure 36: Reactive Power Consumption for Sunday 03/02/ Figure 37: Reactive Power Consumption for Monday 03/03/ Figure 38: Reactive Power Consumption for Tuesday 03/04/ Figure 39: Reactive Power Consumption for Wednesday 03/05/ Figure 40: Reactive Power Consumption for Thursday 03/06/ Figure 41: Reactive Power Consumption for Friday 03/07/ Figure 42: Current Flow Data for Thursday 02/28/ Figure 43: Current Flow Data for Friday 02/29/ Figure 44: Current Flow Data for Saturday 03/01/ Figure 45: Current Flow Data for Sunday 03/02/ Figure 46: Current Flow Data for Monday 03/03/ Figure 47: Current Flow Data for Tuesday 03/04/ Figure 48: Current Flow Data for Wednesday 03/05/ Figure 49: Current Flow Data for Thursday 03/06/ Figure 50: Current Flow Data for Friday 03/07/ iv

5 v ACKNOWLEDGEMENTS I would like to thank Dr. James Harris for giving me the opportunity to work on this interesting and useful project. In addition, I would also like to thank Dr. Ali Shaban for all his help and assistance, along with the rest of the SuPER team and everyone at the Organic Farm who helped me out. Lastly, I would like to thank my friends and family for their support during my entire college career.

6 vi ABSTRACT This senior project focuses on the Cal Poly Organic Farm s electrical system; characterizing its layout and all of its loads. In doing so, recommendations can be made to convert the farm to run off a DC power source, specifically solar energy from the SuPER system. This project began when the SuPER system prototype desired a local field testing location to operate in a real world situation. Around the same time, the organic farm made the decision to invest in solar power in order to become more sustainable. In this report, the electrical characterization of the organic farm is discussed, which then is followed by an assessment of what is needed to convert from an AC to a DC power system. Additionally, recommendations on how to implement the SuPER system prototype are discussed.

7 1 I. INTRODUCTION The Sustainable Power for Electrical Resources, or SuPER, project is a collaborative effort between Cal Poly students and faculty to create a standalone solar power system. This system is designed to power a single family house, provide power to those who previously did not have access, and to be low cost with a life cycle of about 20 years [1]. Currently in the Phase 0 prototype, it consists of a solar panel, DC-DC converter, 12V battery, computer controls, and loads that simulate a household, including a motor, cooler, lighting, and a television. The Cal Poly Organic Farm is a small area where students can learn about growing organic crops. Currently powered by PG&E power, the farm would like to switch to an alternative energy source, in an effort to increase sustainability. Being a small farm with few electrical devices being used for long periods of time, the use of small solar generating units could perhaps fulfill all the energy needs. This is the main focus of my senior project given the current electrical requirements of the farm, what is the feasibility of using solar photovoltaic panels to supply power for the farm without using grid power? In this case, the solar power source will be from multiple SuPER systems. In addition, the number of units needed and where and how to implement them will also be part of the project. This project was born when Dr. Jim Harris and I discussed possible senior project topics dealing with the SuPER system. The Organic Farm was looking to go

8 2 towards a more sustainable energy source, and the SuPER system needed on-site field testing, and so this project was developed to bring the two together, benefiting both as a result. Section II of this report presents the background for this senior project. In Section III, the electrical system at the farm is discussed as well as the layout of all of its loads. Section IV discusses methods of simulating and testing of the farm s electrical system, which includes actual power measurements. In Section V, an assessment on how to convert the farm from an AC power system to a DC system is discussed, which provides the most efficient way of utilizing the inherently DC solar power. Additionally, given the current capabilities of the SuPER system, a recommendation on where to install units is given.

9 3 II. BACKGROUND The Cal Poly Organic Farm, tucked away behind the rodeo area, is an excellent place for students to learn about organic crops, and allows them to oversee the entire planting cycle from seeding to harvesting. Officially called the Student Experimental Farm, it was born from a graduate student project back in Since then, students and community members have used it as a place to learn about alternative and eco-friendly farming methods [2]. Today, the farm focuses on providing students with the knowledge needed to grow organic crops, and to do so in a sustainable manner. Figure 1 highlights the location of the farm. Figure 1: Cal Poly Campus Map

10 4 The farm consists of four buildings that are officially identified by the university: Packing Shed, Straw Bale House, Storage Shed, and Greenhouse. These have been outlined in Figure 2. The Packing Shed sees the most (human) activity at the farm it is the place where all the organic vegetables are washed and spun dried, packaged into boxes and distributed to the local residents who participate in the program. Across the path is an oddly shaped brown building named the Straw Bale House, which gets its name because it is constructed using straw bale. This building serves as both an office and file storage area. The Storage Shed is just that, a place where items are stored. It also is the location of the service entrance from PG&E. Finally, the Greenhouse is the first thing one notices when arriving at the farm. Figure 2: Organic Farm Aerial Photograph (Photograph courtesy of Google Maps)

11 5 With sustainability being one of the farm s important aspects, it makes sense that alternative forms of energy should be looked into for the farm, as well as modifying the way energy is used to be more efficient. With rising costs of energy and the increasing impact on the globe s climate, many are turning to alternative forms of energy including solar generated power, wind generated power, and bio fuels. These technologies produce clean electricity with little to no pollution as a byproduct, but with high initial costs. This could be a reason why more people have not switched over the technology is still very expensive and the economic payback period is too long. Currently, the Organic Farm is using power from the local utility, Pacific Gas and Electric Company. This electricity is generated at a power plant many miles away and is brought over to the farm via transmission lines. This centralized system of obtaining power works, since the farm is located in an urban area that is served by the utility company. But consider a farm that is located hundreds of miles from the nearest transmission line. How can that farm use electricity without having to build expensive transmission lines to bring in power generated from a power plant? The answer to that is a decentralized solar generation system, like the SuPER system. Designed to provide electricity for those without prior access, such as those in sub-saharan Africa, the SuPER system works as a self contained power plant and solves the problem of relying on a centralized power distribution system. The SuPER system provides at least 700 watt hours of power per day, with a DC distribution system since solar power is inherently DC. By avoiding the use of an inverter,

12 6 greater efficiencies can be achieved. However, this requires the use of only DC loads, which in today s world, is not the standard. Although most appliances are powered by DC, such as computers and battery chargers, they have all been designed with AC to DC power supplies since AC power is widely available. The SuPER system is not brand new technology; many solar generation systems already exist. However, the way SuPER delivers the power is quite different than the typical residential solar installation. Those wanting to install a solar system for their residence can choose from many contractors specializing in solar installations. These systems typically consist of an array of solar photovoltaic panels mounted on the roof of the home. From there, the power is then fed into an inverter which provides the residence with AC power, as a supplement to grid power. A battery bank can also be installed to store excess power generated during the day and supply the house with power in the evening. Due to the high cost of equipment, many residences opt for a system that does not provide 100% of the power used, but rather acts as a supplement to reduce the amount of grid power used. So why not use this type of system at the Organic Farm? It would be relatively easy to install such a system at the minimum, install an array of solar panels and an inverter, and tie it into the PG&E service entry. This would provide the farm with a sustainable energy source without having to change anything downstream of the farm, since AC power would still be fed into the electrical system. Looking into the future, however, a localized DC source is the way to go in order to obtain maximum efficiency. With the traditional solar generation systems,

13 7 the power is still generated in a single location and must be carried to the point of use via cables. The farm has four buildings which need electricity, and they are located several hundred feet away from the PG&E service entrance. Losses in these relatively long cables present reduced efficiency for the system. This is where the SuPER system has an advantage it is designed to be installed at the point of use, and so each building can have its own small solar generation unit and avoid losses in transmission. A solar generation system used to generate utility supplementing AC power requires the use of an inverter since the power coming from the solar panels is DC. Today s inverters have efficiencies from 85% to 95%, which present losses of up to 15% [3]. In addition, when no electricity is being used, the inverter is still operating in order to maintain AC power to be available. Power quality also becomes an issue when using inverters. Low cost inverters merely output a square wave in order to simulate a sinusoidal waveform. If there are loads that depend on purely sinusoidal waveforms, more expensive inverters must be used. By having a DC distribution system paired with localized solar power, the highest efficiency can be obtained, since no inverter is needed.

14 8 III. REQUIREMENTS AND DESIGN To be able to assess what was needed to convert the farm to use solar power, a load analysis of the farm was required. The first step to accomplishing this involved getting the utility information of the farm. Dennis Elliot, the manager of Engineering and Utilities on campus, provided me with monthly energy usage data for July 2006 to June The following graph presents the data. Cal Poly Organic Farm Electricity Usage, July 2006 to June $ $ $ Power Used (kwh) $ $ $ $ $ $86.90 $ $ $ $ $ $95.56 $ $ $ Cost ($) kwh Used Cost 0 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Month $0.00 Figure 3: Monthly Electrical Usage

15 9 According to Figure 3, the amount of electricity used last year was pretty consistent from July to December, averaging 630 kwh per month. In the month of January, however, the usage shot up about 200% of the average of the past half year. The exact reasoning for this is unknown, but could be attributed to an increase in activity at the farm. This increased amount of usage was also seen in April to June. Taking into account the entire year, the average monthly usage was 844 kwh, with an average cost of $ In the whole year, the farm used 8,900 kwh at a cost of $ In terms of daily usage, the farm used an average of kwh per day. Loads at the Farm Now that I knew the amount of electricity used by the farm as a whole, the next step was to look into who was using the power. This involved determining the load characteristics by identifying every single electrical device on the farm, whether it was currently being used or lying in storage to be used occasionally, and figuring out how much power each item consumed instantaneously in watts. This was done primarily by looking at the load s nameplate data, which would give either watts, or amps at a given voltage (120V rms ). If the device had no nameplate data, the label was unreadable, or more information was desired, I looked into the manufacturer s website for any electrical ratings. Finally, for devices that were not hard wired, I utilized a commercially available wattmeter (P3 International P4400 Kill-A-Watt ) to measure the amount of actual power the device used in watts. This number was often lower than the nameplate rating, but provided a more realistic number. Table I presents the loads found at the farm, separated by building.

16 10 Table I: Organic Farm Loads Table Ia: Packing Shed Loads # Load Name Nameplate Data Nameplate Watts 1.1 Vegetable Spinner: The Greens Machine VP-1 Attached motor: Franklin Electric 1.2 Stereo: Sony CFD Toaster Oven: Krups Type 553 Microwave: Sharp Carousel II (2) Digital Scales: Torrey MFQ-40L Water Heater: Rheem 81VP6S, 6 gal Mini fridge: Unknown brand Outdoor Lamps (4): high pressure sodium, Philips C50S68/D/M Fluorescent Lamps: (6) 4 2 lamp fixture Fluorescent Lamp: circular with (3) bulbs 120V, 2.7A, 1Φ, 60 Hz 115V, 2.5 FLA, 1Φ, 60 Hz, 1/6 HP, 23 lb-in AC: 120V, 60 Hz DC: 15V (10 1.5V D-Cell) DC: 4.5V (3 1.5V AA-Cell) (radio only) Not given 180 W 25 W Measured Watts * 100 W 5 W (cassette mode) 120V, 60 Hz 1500 W 1360 W 120V, 8A, 60 Hz 960 W 925 W Charger: 115V; Vout = 9V, Iout = 0.5A 6.43 W each 5 W each 120V, 1Φ 2000 W n/a (no information) n/a 115 W 4000 Lumens, 2100k temperature, 24,000 hrs life Unknown, assume T12 type lamp Unknown, assume 100W replacement CFL 50W each 200 W Total Assume 40 W each Assume 480 W total Assume 23 W each Assume 69 W total 285 W Total 330 W Total Total 5, W (Max) 3,125 W Table Ib: Straw Bale House Loads # Load Name Nameplate Data Nameplate Watts Laser Printer: Brother HL Computer: Dell Optiplex GX110 Montor: Dell Ultrascan P V, 7.8A, 60 Hz Printing: 340 W Standby: 80 W Sleep: 5 W Measured Watts * Standby: 6 W 115V, 6A, 60 Hz 145 W (Max) 80 W V, 1.7A, 60 Hz On: Max 120W, Typ. 95W Standby/suspend: < 15 W On: 40 W Active off: < 3 W Total 605 W (Max) 126 W

17 11 Table Ic: Storage Shed Loads Measured # Load Name Nameplate Data Nameplate Watts Watts * Fluorescent Lamps: (1) 4 Assume 40 W each 3.1 Unknown, assume T12 type lamp 65 W total 2 lamp fixture Assume 80 W total Total 80 W 65 W Table Id: Greenhouse Loads # Load Name Nameplate Data Nameplate Watts 4.1 Blower Fan: AO Smith (2) Exhaust Fans: ACME Windmaster DC30H-B Circulation Fan: ACME Fan-Jet RC18E6 Motorized Window Shutter: ACME Flo- Master WAAC2626MT Handheld Vacuum: Unknown brand 115V, 0.8A, 60 Hz, 3200 RPM, 60 CFM, 1/100 HP Measured Watts * 70 W 67 W 115V, 10.6A, 1725 RPM, ¾ HP 740 W each 793 W total 115V, 60 Hz, 1Φ, 260 W 248 W 115V, 60 Hz 17 W n/a (no information) n/a 700 W Total 2527 W 1,808 W Table Ie: Other Loads # Load Name Nameplate Data Nameplate Watts 5.1 Water Pump in pond: Unknown brand Measured Watts * (no information) n/a 800 W * Measured using P4400 Kill-A-Watt wattmeter Acquired from ETAP Load Flow Analysis Measured from PS3000 Measurement Within each table are all the loads present in the building. They are not likely to be used all at once, but there is a possibility that all items could be used at one time; for example, see Table Ia for the loads in the packing shed. There are quite a few

18 12 loads which consume a lot of power (water heater, toaster oven, and microwave). These appliances are not used very often; they are used for a few minutes at a time, and only a few times in a whole day. These numbers just represent power consumption not taking into account how long and often they are used. To find out about how the loads are used at the farm, I spoke with farm manager Cindy Douglas, who has helped me out immensely during my field visits. According to her, there is always somebody present at the farm Monday through Saturday, 8am to 5pm. While there, they could be planting, harvesting, cleaning, or packing vegetables. They also use the computer in the Straw Bale house, and listen to music and heat up lunches in the packing shed. In the winter months, it gets dark at around 5 PM, and so lights are used for an hour or so. The lights are likely used during overcast days as well. According to the tables above, it seems as if the packing shed uses the most electricity. The numbers are misleading, however, since the high wattage appliances are not constantly being used. In addition, the lights use a hefty amount of energy, but are not used very frequently since most personnel leave by 5pm. During harvesting, the vegetable spinner is used frequently to remove water from washed vegetables. So besides the water heater and mini fridge (which are always cycling on and off) and the stereo, not much else is used for long periods of time. Based on these observations, analyzing measurement data, along with input from Brad Booker (one of the farm personnel who helped me), Table II gives an estimate on how much energy is used in a given week, and also per day.

19 13 # Load Name Table II: Packing Shed Load Schedule Power (Watts) Hours Per Week Total Power Per Week (Watt-hours) Average Power Per Day (Watt-hours) 1.1 Vegetable Spinner Stereo Toaster Oven Microwave (2) Digital Scales Water Heater ,000 1, Mini fridge , (4) Outdoor Lamps , Fluorescent Lamps: (6) 4 2 lamp fixture Fluorescent Lamp: circular with (3) bulbs ,400 2, , Total 39,112.5 Wh 5,587.5 Wh Mondays and Thursdays are the harvesting days this is when the farm sees the most activity. Throughout the day, farm personnel are washing and spin-drying the vegetables, packing them into boxes, listening to the stereo, and heating up lunches. On these days, the lights are left on from 5pm to 8am the next morning. The reasoning for this is because it allows local residents to come pick up their vegetables after dark, illuminating the packing shed area. Doing this, however, consumes a lot of electricity, especially by leaving the lights on overnight. A better solution for this is to install a simple hand-crank rotary timer to replace the on/off switch, allowing the lights to stay on for only a few hours at a time. Compared to the total use per day, the Packing Shed accounts for roughly 20% of the power consumed.

20 14 The Straw Bale House contains only the computer, monitor, and printer. Based on the hours of operation, one would assume the computer would be on only during those times. However, when I was performing measurements one day, I noticed that the computer was left on for 5 days, 5 hours, and 9 minutes. This means that the personnel likely forgot to shut down the computer when they left at the end of the day. The good thing was that the monitor and printer were off. Regardless, for the sake of estimation, I will use the normal 9 hour day for calculation purposes. Table III presents an estimated energy usage for the Straw Bale House. Table III: Straw Bale House Load Schedule # Load Name Power (Watts) Hours Per Day 2.1 Laser Printer Sleep: 6 W Printing: 340 W Sleep: 0.5 Printing: 0.01 Total Power Per Day (Watt-hours) Sleep: 3 Printing: Computer 80 W Montor 40 W 2 80 Total Wh The Storage Shed contains only a set of fluorescent lamps and an outlet. Occasionally, work is done around this building that requires the use of power tools. In these rare cases, the tools are plugged into the outlets at the shed. The lights in this building are probably used very infrequently, so for estimation purposes, I assume they are used for 70 minutes in a week, equating to 10 minutes per day. # Load Name Table IV: Storage Shed Load Schedule Power (Watts) Hours Per Day Total Power Per Day (Watt-hours) 3.1 Fluorescent Lamps Total Wh

21 15 The Quonset-style greenhouse on the farm contains two exhaust fans driven by ¾ HP motors each, an air circulator driven by a ¼ HP motor, a motorized window shutter for the air circulator, a small blower fan that keeps a layer of air between the two plastic roof covers, and a small vacuum that is used with seed equipment. The fans are controlled by temperature via thermostats. The two exhaust fans are activated when the temperature inside the greenhouse exceeds the temperature set on the thermostats. During colder temperatures, the top fan operates to blow air down a perforated tube that runs the length of the greenhouse, circulating the inside air. When temperatures get too high, the automatic window shutter will open, allowing fresh air to enter. Even higher temperatures turn off the top fan completely and cycle the two exhaust fans on. The amount of time the large fans are on depends on the temperature set, outside temperature, and duration of sunlight. The small blower fan that keeps the skin inflated is left on all the time in order to prevent the cover from being blown away, as well as to provide insulation for the greenhouse. The handheld vacuum is used with a large perforated plate to hold seeds in place. This allows the seeds to be planted in an orderly grid quickly, and according to Brad, sees about 5 hours of use per month. Because there are many variables that determine how long the greenhouse fans operate, the best way to get data is to measure the power, which is what I did. Since the greenhouse fans are hard wired, I couldn t measure them using my plug-in wattmeter. Therefore, it was required to utilize a more robust power meter that could analyze the load demand over several days. The details of this are further discussed

22 16 in the Simulation and Electric Power Measurement section. Based on the measured data, Table V presents the load schedule for the greenhouse fans. This data only applies for operating conditions similar to that during the time of measurement; an average outside temperature (during the day) of 65ºF, average humidity of 72%, sunny to partly cloudy skies, and greenhouse thermostat set to 80ºF. There exists a discrepancy between the nameplate and measured power for the two exhaust fans, as see in Table Id, item 4.2. The 740W value is the estimated power consumption of one ¾ HP motor as calculated by computer simulation. Based on the power measurement data, it was seen that these exhaust fans consumed around 793 watts combined, which is about half of what was provided by simulations. The motors that operate the fans are rated at ¾ HP, but can also be operated at ¼ HP, which leads me to believe that the fans speeds are adjustable. Most likely, this is done by the thermostat. In warmer temperatures, the fans may operate at a higher speed and thus require more power. This could be verified by performing the same power measurement in the warmer summer months. The final load is a small water pump at the bottom of the pond adjacent to the greenhouse. This pump plugs into the outlet right in front of the pond, and draws a measured 800W. The sole purpose of this pump is to create a more aesthetically pleasing look to the pond it creates a lush waterfall over rocks and brings relaxation to the viewers of the pond. According to farm personnel, this waterfall generating pump is not very often. For estimation purposes, I will suppose that the pump is used

23 17 twice a month, 9 hours each time. This results in an average of about 0.6 hours per day, or 480 Wh per day. Table V: Greenhouse Load Schedule # Load Name Power (Watts) Hours Per Day Total Power Per Day (Watt-hours) 4.1 Small Blower Fan 70 W 24 1, (2) Exhaust Fans 740 W 5 3, Circulation Fan 260 W 19 4, Motorized Window Shutter 17 W Seconds negligble 4.5 Handheld Vacuum 700 W Total 10, From Table VI, it can be seen that in one month (30 days), the entire farm uses about kilowatt-hours. This estimate is about one hundred kilowatt hours below the actual power usage from March of last year, as presented in Figure 3, but Table VI: Summary of Energy Usage # Building / Area Total Power Per Day (Watt-hours) 1 Packing Shed 5, Straw Bale House Storage Shed Greenhouse 10, Other Loads 480 Total 17, Average Daily Power Last Year 28,100.00

24 18 this estimate does not include any other loads which may get plugged into the various outlets at the farm. Additionally, the climate plays a big role in the amount of power used by the farm, as is shown in the data from the load demand measurements. Electrical Distribution System In addition to figuring out all the electrical loads at the farm, an understanding of the layout of the electrical system had to be known. This is because the SuPER systems would be implemented at existing circuits. Not only would this take advantage of existing wiring and hardware, it would also provide an easy way to go back into the grid in case of generating equipment failure or the need for more power than can be supplied. By looking at the main incoming power and load center, a map was developed for the farm s electrical system. Since the wiring was all underground, it was difficult to physically trace the wires, so testing of the circuit breakers had to be done. Using a multi meter at outlets and monitoring switched-on lights, unknown breakers were tripped to verify the circuits. My housemate Michael Lee assisted me with this, and communications via FRS radio simplified the verification process. Of course, we made sure that critical loads were turned off during the testing, such as the computer.

25 19 Figure 4 is the single line diagram of the electrical system at the farm. It begins with single phase 480V PG&E power feeding through a 30A disconnect switch into a 25 KVA 240x480/ V single phase transformer. From there, the power goes into a load center with a 100A 2-pole main breaker, 50A 2-pole breaker for another load center, and five breakers labeled for the greenhouse. The first 20A breaker protects the outlets in the greenhouse. The second 20A breaker, labeled greenhouse, provides protection of a spare circuit at the greenhouse. According to the campus electricians, the spare circuit was added because when they were initially pulling the wires, they decided to pull an extra circuit for future expansion. Next is a 2-pole 20A breaker that protects the three fans, small blower fan, and automatic window shutter in the greenhouse. The last two 20A breakers, both labeled Greenhouse SP, provide protection for two outlets; one is by the pond adjacent to the greenhouse and the other is in the Festival Circle next to the stage. The 50A 2-pole breaker, labeled inside panel, provides protection for a small load center inside the storage shed. This load center, with a 30A 2-pole main breaker, provides power for the rest of the buildings. A 20A and 15A breaker protects the storage shed s outlets and lighting, respectively. The next 20A breaker protects the lighting at the packing shed. The last 20A breaker protects the outlets in both the strawbale house and packing shed. The power at the farm is split between two phases; a black conductor (mentioned from now on as phase A) and a red conductor (phase B), with a shared neutral. This setup allows 240V loads to be connected to the system, but the farm

26 Figure 4: Organic Farm Single Line Diagram 20

27 21 currently does not have any of these that I know of. After going through the 2 pole main breaker, the two phases are split amongst the various loads. Figure 5 and Figure 6 detail the layout of the two circuit breaker panels at the farm. In addition to what loads the breakers protect and their rating, the phase they are connected to is also listed. Figure 5: Main Circuit Breaker Panel Layout

28 22 Figure 6: Inside Panel Circuit Breaker Layout Having both building s outlets on the same circuit is not too desirable in terms of implementing the SuPER systems; it would be ideal if they were on their own circuits. The packing shed uses a lot more power than the strawbale house, and if they were separate, a single SuPER System could easily be installed to satisfy the power needs of the computer and printer. Modifications to the wiring would need to occur in order to use a single SuPER System for the strawbale house. Otherwise, multiple units would be needed to power both buildings outlets. See Appendix B for detailed information regarding the electrical components used at the farm.

29 23 IV. SIMULATION AND ELECTRIC POWER MEASUREMENT ETAP Once all the loads at the farm were identified, along with completion of the single line diagram, the next step was to perform a computer simulation of the farm. Not only did this provide missing information about power drawn from loads, but it also allowed switching things on and off to see the overall effect on the power usage. Using the program ETAP (Electrical Transient Analyzer Program) [4], I first built the single line diagram according to Figure 4, with a few modifications. As previously mentioned, the Straw Bale and Packing Shed outlets are all on the same circuit. To be able to analyze the power flow of the loads at these buildings, I created a bus to represent that circuit and separated the loads into four distinct loads. The first was the vegetable spinner; as it contained an induction motor rated at 1/6 HP, I wanted ETAP to analyze the motor to provide both real and reactive power. The second load was named Pkg Heating which represents the loads in the Packing Shed that are used for heating the water heater, microwave, and toaster oven. These loads are also high power users, but are not on frequently. Next is Pkg Other which represent the rest of the loads in the Packing Shed, which are used more often. The final load Strawbale Loads represents the computer, monitor, and printer located in the Straw Bale House.

30 24 After inputting ratings for the transformer and circuit breakers, I proceeded to run a load flow analysis. The load flow analysis basically turns on the entire system and reports the voltage at each bus. More useful, however, is the amount of real and reactive power flowing at each branch, which also includes the total simulated power consumed by the farm. Figure 7 contains the single line diagram along with bus voltages and power flow information. Since I had no way of measuring the power drawn by the hard wired fans in the greenhouse, I relied on the load flow analysis to obtain the value for power used. When inserting a motor into the single line diagram, I used the ETAP typical settings that were automatically input once I inserted a horsepower rating. This simplified the simulation process greatly, as I did not know the details of the motor, such as power factor and efficiency. Initially I had used the equation P motor = 746 HP to come up with a crude estimate of power drawn by the motors. This calculation, however, is based on the ideal motor with 100% efficiency (no losses anywhere in the motor). By using the ETAP values, a more realistic value is used to model all the motors. The ¾ horsepower exhaust fan, for example, was initially calculated to draw only watts. ETAP, taking into account efficiency and other losses, reported that the ¾ HP exhaust would draw 740 watts and 550 vars.

31 Figure 7: Load Flow Analysis 25

32 26 Since it is not possible for every single device to be powered on at the same time, I wanted to create scenarios that would present a more realistic number for total power consumed by the farm. To do this, I thought of different times of the day and which loads would likely be on. I then opened the switches for those that would not likely be on, and re-ran the load flow analysis. Table VII summarizes the results. (See Appendix C for the load flow diagrams of these different scenarios) Scenario Table VII: Various Power Demand Scenarios Comments Power Consumption (kw + jvar) Max. Power Every load is turned on 9 + j2 Min. Power Daytime Working 1 Daytime Working 2 Lunchtime 1 Lunchtime 2 Evening Strawbale and pkg other loads, and blower fan on Min. Power + greenhouse vacuum, veg spinner, and intake fan Same as above except exhaust fans are on instead of intake fan Min. Power + pkg heating, blower and intake fan on Same as above except exhaust fans are on instead of intake fan Blower, all lights, all packing shed and strawbale loads are on j j j1 5 + j j1 5 + j0.1 Since the preceding table represents a computer simulated model of power consumption, it may not be entirely accurate. This can, however, provide insight as to when the farm s power system experiences peak demand. Although the Max. Power scenario draws the most power (9 kw and 2 kvar), this scenario is impossible due to the way the fans are controlled either the intake fan or the exhaust fans can be on at any given time. Additionally, the lights are seldom on during the

33 27 day, which is when the fans are likely to be running. Therefore, the peak demand can be estimated to occur during the Lunchtime 2 scenario. This most likely occurs between 12pm to 2pm when farm personnel take their lunch break, which is a reason for the heating equipment (toaster oven and microwave) to be on. At the same time, the sun is at its highest in the sky, resulting in warm ambient temperatures. The greenhouse temperature is most likely very high, which means the exhaust fans are operating. This combination of high power devices results in peak load occurring. PowerSight PS3000 To be able to get a better measurement of the amount of power the farm uses, I had to go beyond measuring each load directly and relying on computer simulation results. I first went to the Cal Poly Electric Shop in order to see what kinds of power monitoring equipment they had used in the past. Unfortunately their equipment was dated, bulky, and only measured voltage and current. Looking into what equipment the Electrical Engineering department had, I was granted access to a PowerSight PS3000 [5]. This piece of power monitoring equipment measures voltage, current, real power, reactive power, apparent power, power factor, and harmonics, all within one small digital unit. In addition to capturing real time information, it also has the capability to log data into its internal memory. Because I wanted to capture the amount of power used throughout an entire day, I took advantage of the unit s data logging function. Using the software PowerSight Manager, I was able to access the unit s data logging options, which include what variables to record, along with how often. By setting these values, the

34 28 total recording time (how long the unit could store data before the memory filled up) was known. Figure 8 outlines the variables I chose to record, which resulted in a record time of 29.4 hours (records every 1 minute). Figure 8: PowerSight PS3000 Datalog Settings The PS3000 takes measurements of the checked values (as seen above) every second, and at the end of the minute, all 60 measurements are converted into one set of measurements which include minimum, maximum, and average voltage, current, and power. In this case, I was interested primarily in true power (watts) and VA power (volt-amps), but also wanted to look at voltage, current, and power factor. Of course, time was also recorded to understand when the power is used. The power coming out of the transformer contains two hot wires (line) and a neutral wire. Line-to-neutral voltage is 120V, and line-to-line is 240V. This setup is similar to the typical household; 240V is used for higher power devices such as ovens and electric clothes driers. Because of this, the PS3000 needed to be configured to

35 29 record phase-phase voltage instead of phase-neutral. It also required the use of two voltage and two current probes for the lines, in addition to the single neutral voltage probe. Figure 9 provides a schematic to how the unit was installed. Due to risks of electric shock (in addition to campus policy), I enlisted the services of a campus electrician, Jeff Duft, to help me open the breaker panels and make the connections. Appendix D contains photographs of how the PS3000 was installed at the farm. Figure 9: PowerSight PS3000 Connection The PS3000 was installed on Thursday February 28, 2008, at approximately 10:45 AM, and removed on Friday, March 7, 2008, at approximately 3:18 PM. I wanted to compare the power used with the temperature, so I found data containing many meteorological variables online [6]. There happens to be a weather station located very close to the Organic Farm at the corner of Highland Drive and Mt. Bishop Road, so I pulled the data from this station for the days the PS3000 was logging data. The following figures document power usage and temperature over a week.

36 Organic Farm Power Consumption Thursday 02/28/ Power Temperature Power (Watts) Temperature (ºF) :00:00 11:30:00 12:00:00 12:30:00 13:00:00 13:30:00 14:00:00 14:30:00 15:00:00 15:30:00 16:00:00 16:30:00 17:00:00 17:30:00 18:00:00 18:30:00 19:00:00 19:30: :30:00 21:00:00 21:30:00 22:00:00 22:30:00 23:00:00 23:30:00 Time Figure 10: Power Consumption for Thursday 02/28/ Organic Farm Power Consumption Friday 02/29/ Power Temperature Power (Watts) Power was unplugged or unit's memory prematurely filled up :00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00: :00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00: :00:00 22:00:00 23:00:00 20 Temperature (ºF) 10 0 Time Figure 11: Power Consumption for Friday 02/29/08

37 Organic Farm Power Consumption Saturday 03/01/ Power Temperature Power (Watts) Temperature (ºF) :00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00: :00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00: :00:00 22:00:00 23:00:00 Time Figure 12: Power Consumption for Saturday 03/01/ Organic Farm Power Consumption Sunday 03/02/ Power Temperature Power (Watts) :00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00: :00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00: :00:00 22:00:00 23:00:00 Temperature (ºF) Time Figure 13: Power Consumption for Sunday 03/02/08

38 Organic Farm Power Consumption Monday 03/03/ Power Temperature Power (Watts) Power was unplugged or unit's memory prematurely filled up Temperature (ºF) :00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00: :00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00: :00:00 22:00:00 23:00:00 Time Figure 14: Power Consumption for Monday 03/03/ Organic Farm Power Consumption Tuesday 03/04/ Power Temperature Power (Watts) :00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00: :00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00: :00:00 22:00:00 23:00:00 Temperature (ºF) Time Figure 15: Power Consumption for Tuesday 03/04/08

39 Organic Farm Power Consumption Wednesday 03/05/ Power Temperature Power (Watts) Temperature (ºF) :00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00: :00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00: :00:00 22:00:00 23:00:00 Time Figure 16: Power Consumption for Wednesday 03/05/ Organic Farm Power Consumption Thursday 03/06/ Power (Watts) Temperature (ºF) Power 0 1:00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00: :00:00 12:00:00 13:00:00 14:00:00 15:00:00 16:00:00 17:00:00 18:00:00 19:00: :00:00 22:00:00 23:00:00 Temperature 10 0 Time Figure 17: Power Consumption for Thursday 03/06/08

40 Organic Farm Power Consumption Friday 03/07/ Power (Watts) :30:00 1:00:00 1:30:00 2:00:00 2:30:00 3:00:00 3:30:00 4:00:00 4:30:00 5:00:00 5:30:00 6:00:00 6:30:00 7:00:00 7:30:00 8:00:00 8:30:00 9:00:00 9:30: :30:00 11:00:00 11:30:00 12:00:00 12:30:00 13:00:00 13:30:00 14:00:00 14:30:00 15:00:00 Temperature (ºF) 20 Power Temperature 10 0 Time Figure 18: Power Consumption for Friday 3/7/08 On Friday 2/29/08 and Monday 3/03/08, there was an interruption in the recording of data. These were due to either the recorder prematurely filling up its memory, or the PS3000 s power supply was unplugged, thus ending recording. During instances where somebody unplugged the unit and replaced the plug, the PS3000 did not automatically resume recording data, unfortunately. After notifying farm personnel that the unit was in operation and having written requests not to unplug the unit, the data became more stable. Appendix F contains additional figures detailing daily current flow and reactive power consumption.

41 35 Table VIII summarizes the minimum, average, and maximum power (not including spikes), the largest spike seen, when it occurred and the ambient temperature at that time. As seen from the power consumption figures above, there are two sets of recurring spikes in power (which are caused by current spikes). The first set of spikes occurs on phase A, appears roughly every 110 minutes, lasts for around 4 minutes, and has a magnitude of about 2000 watts. The most likely culprit for this is the water heater, which is rated at 2000 watts, cycling on and off for a few minutes every few hours to keep the water hot. The second set of spikes occurs on phase B, appears roughly every 60 minutes, lasts for 10 minutes, and has a magnitude of around 100 watts. This set of spikes is most likely caused from the miniature refrigerator, which was measured to draw around 115 watts. It also makes sense since the fridge needs to cycle on and off in order to keep the contents cool. Since the unit was limited to 29.4 hours recording time, I had to download the data at the end of each day and start recording again. While downloading the data, I would note the instantaneous power used by the farm, and then take a quick walk through of the farm to identify which loads were operating. These could be comparable to the scenarios I created using ETAP, although a lot more accurate. Table IX represents my daily findings. In addition to providing total power used by the farm and the different power demand scenarios, the PS3000 also allowed me to figure out how much power the hard wired loads consume. These include the greenhouse fans and lighting throughout the farm. Additionally, I was able to obtain a better estimate of how many

42 36 Table VIII: Summary of Power Usage Date Attribute Power (Watts) Time Temperature (ºF) Minimum :57 PM 64.2 Thursday February 28, Average 1, Maximum 1, :26 PM 73.0 Largest Spike 3, :36 PM 70.6 Minimum :49 PM 56.0 Friday, February 29, Average Maximum Cannot specify; too much data missing Largest Spike Minimum :57 PM 60.9 Saturday, March 1, Average Maximum 1, :44 AM 56.3 Largest Spike 3, :37 PM 61.8 Minimum :28 AM 50.5 Sunday, March 2, Average Maximum 1,116 1:04 PM 63.1 Largest Spike 3,068 3:03 PM 64.5 Minimum :19 AM 53.3 Monday, March 3, Average Maximum 1, :18 PM 68.1 Largest Spike 3,080 10:48 AM 65.5 Minimum :31 AM 66.3 Tuesday, March 4, Average 1, Maximum 1, :11 PM 61.8 Largest Spike 3, :29 PM 71.8 Minimum 1, :33 AM 61.0 Wednesday, March 5, Average 1, Maximum 1, :43 PM 76.6 Largest Spike 3, :41 PM 76.6 Minimum 1, :41 PM 68.2 Thursday, March 6, Average 1, Maximum 3, :00 PM 66.2 Largest Spike 3,820 12:19 PM 70.5 Minimum 1, :55 AM 57.2 Friday, March Average 1, , 2008 Maximum 2, :40 AM 73.7 Largest Spike 3,836 11:20 AM 73.7

43 37 hours per day the greenhouse fans were operating. These values are reflected in Table V. Table IX: Actual Power Demand Scenarios Date Thursday February 28, 2008 Friday, February 29, 2008 Saturday, March 1, 2008 Sunday, March 2, 2008 Monday, March 3, 2008 Tuesday, March 4, 2008 Wednesday, March 5, 2008 Thursday, March 6, 2008 Time Average Power Reading 12:30 PM 1,720 Watts Loads Operating Both exhaust fans, blower fan, pond pump, stereo 3:30 PM 420 Watts Top fan, blower fan, computer, monitor 6:30 PM 490 Watts 4:00 PM 1,000 Watts 6:15 PM 1,050 Watts 6:20 PM 1,290 Watts 6:05 PM 1,295 Watts 4:45 PM 1,835 Watts Top fan, blower fan, computer, monitor, storage shed lights Both exhaust fans, blower fan, computer, monitor Top fan, blower fan, packing shed lights (inside and outside), computer, monitor Top fan, blower fan, pond pump, computer, monitor, and small air pump for brewing compost tea Top fan, blower fan, pond pump, computer, monitor, and small air pump for brewing compost tea Top fan, blower fan, pond pump, computer, monitor, small air pump for brewing compost tea, stereo, and all packing shed lights Friday, March 7, :18 PM 1,885 Watts Both exhaust fans, blower fan, pond pump, computer, monitor, small air pump for brewing compost tea

44 38 V. USING SUPER SYSTEMS AT THE FARM The main reason for performing this electrical analysis of the Organic Farm was because the farm is an ideal candidate for field testing of the SuPER project. The SuPER system is currently tested by wheeling it outside of the laboratory and operating the test loads. This merely simulates a regular household, but does not provide real life operating conditions. By using SuPER systems at the farm, good testing data can be achieved since the farm is similar to a household (in terms of the types of loads and amount of power used). Additionally, since the farm is located right on campus, it would not be too far from where development work takes place. Faculty and students working on the project can easily access the farm, as well as quickly be available in case something goes wrong. The SuPER prototype can currently generate at least 700 watt hours per day, and roughly 220 watts instantaneously. Looking at the power consumption data for the farm, it is impossible to satisfy the energy needs of the entire farm by using one SuPER system. This was understood before I began the project; my goal was to figure out how many SuPER units would be needed to satisfy the farm s needs, and where the best place to install them would be.

45 39 Keeping the Farm AC Before I can do this, however, there needs to be a study on what type of power system the farm should operate on. It is currently running on 120/240V AC power supplied by PG&E, and all of its loads utilize AC power, much like typical households in the United States. If SuPER systems are installed at the farm without modifying any part of the electrical system, then the SuPER will need to be modified to provide an output of 120V AC. This can be done by using either commercially available DC to AC inverters, or have students design and build inverters specifically for this application. The next item of discussion would be where to install the units, since one obviously is not enough. To minimize performing costly modifications to the protection and wiring system, the best option would be to place several units adjacent to the Storage Shed and feed power into the existing circuit breaker panel. To make the transition between SuPER and grid power, a transfer switch would have to be installed between both sources of power and the farm s circuit breaker panel. In order to connect SuPER in parallel with the grid power, PG&E requires one to enter an interconnection agreement with them to ensure that the system meets their requirements. Regardless of how SuPER will be installed, permits and inspections will most likely be required by the state and county. With these facts squared away, the final assessment is how many units will be needed. From the PowerSight PS3000 data, the farm uses the most power between the hours of 10:00 AM and 6:00 PM. At this time, both greenhouse exhaust fans are

46 40 operating, and will operate for 4-6 hours depending on the ambient temperature. With the computer and monitor on, various water pumps operating, and other loads used by farm personnel, the instantaneous power usage can be stated to be roughly 2000 watts. This value will most likely be the same during summer months, but the amount of time for this much power will likely increase, affecting the amount of watthours used in a day. Because the farm uses 2000 watts continuously for a few hours at a time, the SuPER systems will need to provide this amount of power in order to fully power the farm without any assistance from the grid. Since one SuPER unit can generate at least 220 watts instantaneously during peak sunlight, at least 10 units will be needed to power the farm s 2000 watt needs during the afternoon. All the power generated will be used to power the farm s loads, leaving little to no power to charge the batteries. Because of this, once the sun goes down, the SuPER units will no longer be able to supply any power. This is not acceptable because the farm still uses a lot of power during the other hours of the day, depending on what loads are on. At a minimum, the farm will use 315 watts (greenhouse top fan and blower fan) continuously. If farm personnel leave the computer and monitor on, this value jumps to 435 watts. With the packing shed lights left on during harvest days, the farm then uses 1050 watts of power. As can be seen, powering the entire farm with only SuPER units will require very many units. From the utility meter readings of last year, the highest amount of power used was 1350 kilowatt hours, which equates to 45 kilowatt hours per day.

47 41 Since each SuPER can generate at least 700 watt hours in one day, the farm would require 65 units. When the SuPER system cost drops to $500, this results in a total cost of $32,500. This approach to powering the farm not only is unfeasible, it is also highly inefficient and would require many materials and hours of labor. Each SuPER unit consists of a single solar photovoltaic panel, one battery, a DC-DC converter, and since AC is required, an inverter. A much better approach would be to only use multiple solar panels and batteries, while utilizing a single DC-DC converter and inverter. This method is used by the many solar power companies who specialize in solar installations. If the farm wants to be powered solely by solar power, and wants to keep its existing electrical system and loads, then my recommendation is for them to go through a contractor to perform an installation similar to one I have just described. Using an online solar power installation cost calculator [7], the costs for hiring a contractor to install a solar system for this farm are summarized in Table X. Table X: Professional Solar Installation Cost Estimates Cost Cost after Rebates 25% $15,000 $10, % $27,000 $19, % $40,500 $30, % $54,000 $41, Percentage of Power Supplied by Solar Greenhouse Gasses Saved Over 25 Years (Tons)

48 42 Converting the Farm to DC One option for using solar power is to convert the entire farm to run off DC power. The reasons for using DC power were discussed in the Background section of this report. To convert the farm to DC, all existing AC loads will need to be replaced with DC equivalents. For loads that cannot use DC power, an inverter will be needed. Since the existing fluorescent lighting consumes a large amount of energy, they will be replaced with efficient LED lighting. As its technology improves with time, the light output of LEDs will increase while costs will be reduced. Currently, LED lighting is still relatively expensive and produces less light compared to traditional fluorescent lightings, but it draws a fraction of the power. The DC voltage of the farm will be either 12 or 24 volts, depending on the building and loads used. The following tables list DC replacement loads and their power characteristics.

49 43 # 1.1 Table XI: Packing Shed DC Replacement Loads Existing AC Loads Nameplate Load Name Watts Vegetable Spinner: The Not given Greens Machine VP-1 Attached motor: Franklin Electric 180 W 1.2 Stereo: Sony CFD W Toaster Oven: Krups Type 553 Microwave: Sharp Carousel II (2) Digital Scales: Torrey MFQ-40L Water Heater: Rheem 81VP6S, 6 gal Mini fridge: Unknown brand Outdoor Lamps (4): high pressure sodium, Philips C50S68/D/M Fluorescent Lamps: (6) 4 2 lamp fixture Fluorescent Lamp: circular with (3) bulbs Total Measured Watts 100 W 5 W (cassette mode) 1500 W 1360 W 960 W 925 W 6.43 W each 5 W each DC Replacement Loads Name Data Watts None found; use inverter DC-DC converter All Ride 8 Liter Oven Whispaire FM DC-DC Converter Use at least 200 W inverter 15/4.5V 24V 100 W 5 W 300 W 24V, 34A 816 W 2000 W n/a Use solar water heater n/a 50W each 200 W Total 40 W each 480 W total 23 W each 69 W total 5, W (Max) 115 W 285 W Total 330 W Total Dometic RC1600E MR-PL-DC-DL E27 Base LED bulb LEDTronics TBL324-XPW- 012V 24 LED tube MR-PL-DC-DL E27 Base LED bulb 9V 24V 12V, 140 Lumens, 5000K 12V, 240mA 12V, 140 Lumens, 5000K 3,125 W Total Table XII: Straw Bale House DC Replacement Loads 6.43 W 75 W 2.5 W ea 10 W total 2.88 W ea W total 2.5 W ea 6.5 W total 1,359.9 W # Load Name Laser Printer: Brother HL Computer: Dell Optiplex GX110 Montor: Dell Ultrascan P780 Existing AC Loads Nameplate Watts Printing: 340 W Standby: 80 W Sleep: 5 W Measured Watts Standby: 6 W 145 W (Max) 80 W On: Max 120W, Typ. 95W Standby/suspend: < 15 W Active off: < 3 W On: 40 W DC Replacement Loads Name Data Watts HP Deskjet 460C & HP C8257A Converter Replace with Laptop (Dell B120) & DC- DC Converter for this model 12V To 18.5V 12-32V to 20V Printing: 25 W Standby: 5 W 60 W max 35 W typical Total 605 W (Max) 126 W Total 40 W

50 44 Table XIII: Storage Shed DC Replacement Loads # 3.1 Existing AC Loads DC Replacement Loads Measured Load Name Nameplate Watts Name Data Watts Watts Fluorescent LEDTronics 2.88 W ea Assume 40 W each 12V, Lamps: (1) W total TBL324-XPW-012V 5.76 W Assume 80 W total 240mA lamp fixture 24 LED tube total Total 80 W 65 W Total 5.76 W # Table XIV: Greenhouse DC Replacement Loads Existing AC Loads Nameplate Load Name Watts Blower Fan: AO Smith (2) Exhaust Fans: ACME Windmaster DC30H-B Circulation Fan: ACME Fan-Jet RC18E6 Motorized Window Shutter: ACME Flo- Master WAAC2626MT Handheld Vacuum: Unknown brand Measured Watts 70 W 67 W 740 W each 793 W total * DC Replacement Loads Name Data Watts EBM-Papst G1G085- AB05-01 (2) Dayton 6ML W 248 W Dayton 6MK98 17 W n/a Shutter: ACME Flo- Master WAAC2626MT n/a 700 W Use inverter 24V, 55.9 CFM 24V, 29 FLA, 1800 RPM, ¾ HP 12V, 21 FLA, 1800 RPM, ¼ HP 24V (DC version) At least 800 W inverter 14 W 696 W each 1,392 W total 252 W 17 W 700 W (inverted) Total 2,527 W 1,808 W Total 2,375 W * Exhaust fans may have been running at a lower speed during measurement Table XV: Other DC Replacement Loads # 5.1 Existing AC Loads Load Name Nameplate Watts Water Pump in pond: Unknown brand n/a Measured Watts 800 W DC Replacement Loads Name Data Watts Use inverter At least 1 kw 800 W (inverted) Most of the loads to be replaced in the Packing Shed can be found on recreational vehicle supply websites. The water heater, however, is a tough item to convert to DC there just isn t a market for this. RV water heaters all use some sort of fuel (like propane) and burn it to heat the water. An environmentally friendlier

51 45 method of water heating would be to use solar water heating. This could be a potential project for another student. The loads in the Straw Bale House are a computer, monitor, and laser printer. The computer uses DC power (12V, 5V, and 3.3V) but is powered from an AC power supply. To convert this to use a DC input, a DC-DC ATX power supply can be used, but available DC ATX power supplies are very expensive. The monitor and laser printer cannot be converted to DC and must use an inverter. I recommend replacing the computer and monitor with a laptop; a laptop can easily run off of a DC input, and it combines both the computer and monitor into one low power device. The Dell Inspiron B120 laptop as used in the SuPER system is a good candidate, drawing around 35 watts of power [6], however Dell also offers a variety of other low cost laptops. I would also recommend replacing the laser printer with an inkjet printer that can accept a DC input. One such printer is the HP Deskjet 460C paired with the HP C8257A 12V adapter. The following tables are estimated load schedules like the ones before, but these are based on the DC loads and the amount of power they consume. The number of hours used per day is the same as before. This is necessary to calculate the number of SuPER units necessary.

52 46 # Load Name Table XVI: Packing Shed DC Load Schedule Power (Watts) Hours Per Week Total Power Per Week (Watt-hours) Total Power Per Day (Watt-hours) 1.1 Vegetable Spinner Stereo Toaster Oven Microwave (2) Digital Scales Solar Water Heater Mini fridge (4) Outdoor LED Lamps LED Lamps: (6) 24 LED tube LED Lamps: E27 Base LED bulb Total 4,434.1 Wh Wh Table XVII: Straw Bale House DC Load Schedule # Load Name Power (Watts) Hours Per Day 2.1 Color Printer Standby5 W Printing: 25 W Standby: 0.5 Printing: 0.01 Total Power Per Day (Watt-hours) Standby: 2.5 Printing: Laptop 35 W Total Wh Table XVIII: Storage Shed DC Load Schedule # Load Name Power (Watts) Hours Per Day Total Power Per Day (Watt-hours) 3.1 LED Lamps Total 0.96 Wh

53 47 Table XIX: Greenhouse DC Load Schedule # Load Name Power (Watts) Hours Per Day Total Power Per Day (Watt-hours) 4.1 Small Blower Fan 14 W (2) Exhaust Fans 696 W 5 3, Circulation Fan 252 W 19 4, Motorized Window Shutter 17 W Seconds negligble 4.5 Handheld Vacuum 700 W Total 8, Wh Table XX: Summary of DC Energy Usage # Building / Area Total Power Per Day (Watt-hours) 1 Packing Shed Straw Bale House Storage Shed Greenhouse 8, Other Loads 480 Total 10, After converting the loads to DC, the SuPER systems can easily integrate into the power system where power is needed. By having a solar water heater in the Packing Shed, the large 2000 watt spikes will no longer be present. This greatly reduces the amount of power used in that building. Another big energy user in this building is the lighting. By replacing the fluorescents with LEDs, it is estimated that 2,991.1 watt hours can be saved. Supplying 10, watt hours per day can be accomplished with a minimum of 15 SuPER units.

54 48 With the replacement loads, the Packing Shed is estimated to consume watt hours per day. Given that the SuPER can adequately supply the toaster and microwave ovens during their few minutes of use, then the Packing Shed can be powered by using a single SuPER unit. Since SuPER can generate at least 700 watt hours per day, it would be wise to either have a second SuPER unit, or modify one in order to double the power generation to 1,400 watt hours per day. This will give the Packing Shed overhead on the amount of energy available in case of times of high demand. Because the DC replacement loads run off different voltages, several DC- DC converters will be required. Figure 19 shows where a viable location to where the SuPER unit(s) would be installed. This location works because it faces the sun almost all day, with no trees directly overhead. Additionally, the conduit going into the building is along the wall. Another method would be to install the PV panels onto the roof, and locate the batteries and circuitry inside a cabinet against the wall. Since the Straw Bale House only contains computing equipment, it will be very easy to utilize a SuPER unit here. By replacing the computer and monitor with a laptop and the laser printer with a color inkjet, the total power usage can be estimated to be watt hours per day. This is easily supplied by a single SuPER unit paired with the required DC-DC converters to power the laptop and printer. Since the laptop and printer are estimated to use roughly half the power generated by the SuPER, it ensures that the battery will stay charged. Currently, this building does not have any sort of lighting in it. Installing LED lighting will provide farm personnel with the ability to use this building in the evening. Since the battery will be charged once the

55 49 sun sets, LEDs can use this power to illuminate the building. Mounting the PV panel on the roof will be difficult because there are trees all around the Straw Bale House; the SuPER unit will need to be placed on the grass several yards away in order to operate efficiently. A few proposed locations could be seen in Figure 20 and Figure 21. Figure 19: Proposed Location of Packing Shed SuPER Unit The Storage Shed does not contain many loads; just lighting and a few outlets. It would not be economically wise to spend the money for a single SuPER unit to power just the lights inside this building. I suggest not supplying this building with SuPER power unless it is critical to have lighting and use the outlets in this building. If this is the case, then a single SuPER unit will suffice. Figure 22 shows a possible location for this single unit.

56 50 Figure 20: Proposed Location #1 of Straw Bale House SuPER Unit Figure 21: Proposed Location #2 of Straw Bale House SuPER Unit

57 51 Figure 22: Proposed Location of Storage Shed SuPER Unit The Greenhouse, once retrofitted with the DC motors, will draw an estimated 8, watt hours per day. Actual watt hours will vary greatly with temperature, and therefore season. This estimation is based on the climate at the end of February; sunny to partly cloudy with an average daytime temperature of 65ºF. For this amount of power usage, the Greenhouse will require 12.45, or 13 units to satisfy the watt hour requirements. This is a very large number of SuPER units, and would be very wasteful in terms of the number of DC-DC charge controllers, sensors, wiring, etc. A better way would be to utilize one set of circuitry with multiple PV arrays and a large battery bank. There isn t much space around the Greenhouse to house such a large install, so this is one area of future study that needs to be accomplished.

58 52 SuPER Field Testing With all the analysis completed and discussed in previous sections, the answer to whether or not it is possible to use the Cal Poly Organic Farm as a field test site can finally be given. The Organic Farm would be a great place to test the SuPER unit, but only to power part of the farm. As discussed in the previous section, powering the entire farm solely with SuPER units would require 65 units if the farm s electrical system and loads were to be unmodified. Converting the loads to DC and using the units at their point of use would require a minimum of 15 units. Clearly, this is not what field testing is about. Another issue is the conversion to DC loads. Since the use of DC is currently limited to the RV and other mobile markets, there are not very many options when it comes to appliances. There also is no standard for DC loads as there is for AC; DC loads come in a variety of voltages and no standardized method of connecting them to some sort of outlet. Converting the entire farm to DC would require immense coordination with the farm personnel; they would all need to be trained to use a new power system that they are not currently familiar with. Additionally, AC loads brought in by others would not be able to be used unless there were inverted AC outlets available. One final problem is the issue of going back to grid power in an emergency. To do this would require rectifiers to convert the utility s AC power into the DC power used by the farm s loads. Although it would be unfeasible to convert the Cal Poly Organic Farm entirely to DC, it would not be a far fetched idea for a farm that does not have access to any

59 53 sort of utility power. Since SuPER is designed to provide power to those who previously had no access to electricity, it would do very well in a farm environment with household-like loads. With DC equipment more efficient than AC (lighting, small horsepower motors, electronics), its use when paired with solar power would result in the best way to provide the farm with electricity. With this in mind, the SuPER project should focus on testing the unit at a place that simulates a household. At the Organic Farm, this would be the Packing Shed and Straw Bale House. The Packing Shed and Straw Bale House contain loads very similar to those found in a typical household kitchen appliances, a computer, and lighting. Since the goal of SuPER is to provide DC power for DC loads, the Packing Shed and Straw Bale House would need to be converted to DC, as suggested in the previous section. By converting only these two buildings, AC grid power would still be available at the Storage Shed and Greenhouse. Since a backup source of power for the converted buildings would be required, rectifiers would be installed along with transfer switches at the buildings electrical service input. Although all the DC replacement items can be purchased, it would be worthwhile for students to take on developing solutions to convert the farm to DC as projects. Examples include the various DC to DC converters required, replacement of lighting with LEDs, and developing a rectifier and automatic transfer switch system to provide power if the SuPER units were to be taken offline. In addition to electrical engineering projects, students with other backgrounds could also participate. Such projects include developing a solar water heater, developing more efficient

60 54 methods of heating and cooling foods, and projects that have to do with the structure of the SuPER system. Another area of future study could involve investigating the needs of the greenhouse and developing a more energy efficient method of providing adequate airflow and temperature control. Testing of the SuPER units in this manner would provide the Organic Farm with solar power for half of the farm s buildings. However, this would only provide about 10% of the farm s total electrical needs. Depending on what the Organic Farm is looking for in terms of sustainable power, this may or may not satisfy their goals. Although utilizing SuPER units at the farm would benefit both the SuPER project and the Organic Farm, the ultimate decision on how to proceed with becoming more electrically sustainable is up to the supporters of the farm.

61 55 VI. CONCLUSION The scope of this project involved performing a thorough electrical analysis of the Cal Poly Organic Farm. By first obtaining monthly utility meter readings over the past year, a numerical amount for the power the Organic Farm consumes and the cost to the school was realized. The next step was inspecting the farm building by building to characterize all of the electrical loads present at the farm. From this, a rough estimate on which buildings and which loads used the most power was developed. Further analysis then required the understanding of the farm s electrical layout, which led to development of a single line diagram. Once the farm s electrical system was characterized, the next step was to perform actual load analyses in order to capture when the loads were being used. This was first done by utilizing ETAP to simulate the farm s electrical system. Not only did this give a better understanding of how the power flowed once it arrived from PG&E, it also filled in some blanks in information. Consulting farm personnel provided how long the various loads were used each day, which allowed me to come up with estimates for kilowatt hour usage per month. I then compared these estimates with the utility meter readings from last year, and concluded that the reason I was short was because I didn t factor in inconsistencies in power usage or one-time power use during special occasions, such as tools brought in for small construction jobs.

62 56 The most important part of the load analysis involved taking actual power measurements at the farm. This was accomplished using a PowerSight PS3000 electrical data logger installed at the incoming power panel. By recording the data over a week s time, I was able to better understand how power is consumed at the farm. I also obtained daily temperature data for that same week and compared this with the power usage. This provided data on when the greenhouse fans would switch from exhaust to circulating. The graphs of power usage are crucial data especially when one is designing a solar power system for the farm. As seen in Figure 3, the amount of power consumption fluctuates between seasons. One of the biggest factors governing power consumption is ambient temperature the greenhouse uses more power during warmer days due to the exhaust fans operating for longer periods of time. Additional factors include the amount of human activity the farm sees, which varies throughout the year. Performing power measurements using the PowerSight PS3000 or similar equipment should be made once every season in order to capture a broader range of data. This will give the best results when determining how much power the farm uses throughout the entire year. After the study at the farm was completed, the final step was to recommend a method of utilizing SuPER at the Organic Farm. The first method discussed was to replace the grid power and supply the farm entirely by SuPER systems, leaving the farm s electrical system intact. This would require the least amount of modification to the farm s electrical system because the SuPER systems would be outputting

63 57 inverted AC power to the existing loads. Doing it this way would require a minimum of 65 units, which is unreasonable for both the farm and SuPER project. The second method would convert the farm s electrical system to DC replacing all the loads with their DC equivalent, using an inverter if no suitable DC equivalent load exists, and converting all lighting to LED lighting. This method would reduce the farm s overall energy consumption, and also reduce the required number of SuPER units down to 15. Given the fact that the Greenhouse accounts for almost 90% of the total power used at the farm, I have recommended that for the SuPER project, field testing should concentrate on powering only the Packing Shed and Straw Bale House. These buildings would simulate a household because of the types of loads present, and would give the SuPER project excellent test data. To provide better adaptability, these two buildings should be converted to DC, not only to reduce their power consumption, but because SuPER was designed to supply power to DC loads. Additionally, rectifiers and transfer switches should be installed to provide backup power in the event the SuPER units fail to provide adequate power. Depending on what the supporters of the Organic Farm are looking for, providing only 10% of the power from an alternative energy source may or may not be satisfactory. Additionally, the farm may not opt to convert the Packing Shed and Straw Bale House to DC, which would present difficulty in using SuPER systems. If the farm desires to have all of its power supplied by an alternative source, along with keeping the existing AC electrical system, then it will be unfeasible to utilize SuPER

64 58 systems at the farm. In this case, I recommend that the farm seek the services of a commercial alternative energy supplier, such as a solar power contractor. Although this company will have its own method of investigating the farm s load demand to size the new system, this report will still provide much useful information about the farm s electrical system and loads.

65 59 VII. BIBLIOGRAPHY [1] Harris, James G. White Paper for Sustainable Power for Electrical Resources- SuPER. July 15, < er.pdf> [2] California Polytechnic State University. Student Experimental Farm. < [3] Northern Arizona Wind & Sun, Inc. DC Inverter FAQ. April 19, < m> [4] Operation Technology, Inc. ETAP Products Overview. < [5] Summit Technology. PowerSight PS3000 Manual. < [6] Weather Underground. Weather Station History. Last accessed March 6, < ASANLU4&month=2&day=28&year=2008> [7] Find Solar. My Solar Estimator. < [8] Sheffield, Tyler. Cal Poly SuPER System Simulink Model and Status and Control System. Master Thesis. San Luis Obispo: California Polytechnic State University, April 2007.

66 60 APPENDIX A: PARTS LIST AND COSTS Table XXI: Recommended DC Replacement Loads Parts List and Costs Item Type Brand & Model Qty Unit Cost Total Cost Inverter (for Black & Decker 400 Watt Power Inverter veg. spinner) #PI400AB 1 $34.00 $34.00 DC-DC Converter (for Radio Shack High Power Universal DC stereo & digital Adapter # $34.99 $ scales) Toaster Oven All Ride Silver 8 Liter Oven 1 $48.83 $48.83 Microwave Whispaire FM $ $ Mini Fridge Dometic RC1600E 1 $ $ LED Tube Lamp LEDTronics TBL324-XPW-012V 14 $64.35 $ E27 Base LED Bulb TheLEDLight MR-PL-DC-DL 7 $26.00 $ Inkjet Printer HP Deskjet 460C 1 $ $ DC Converter for Printer HP C8257A 1 $69.59 $69.59 Laptop Dell Vostro 1000* 1 $ $ DC Converter for Laptop Lind Electronics DE $ $ Blower Fan EBM-Papst G1G085-AB $ $ ¾ HP Exhaust Fan Dayton 6ML05 2 $ $ ¼ HP Top Fan Dayton 6MK98 1 $ $ Motorized ACME Flo-Master WAAC2626MT (24V Shutter DC Version) 1 $ $ Inverter (for vacuum and pond pump) Xantrex XPower 1000 Watt Power Inverter 2 $ $ Total 39 $3, $4, * Since the Dell Inspiron B120 has been discontinued, the Dell Vostro 1000 is a low cost alternative, starting at $399.

67 61 APPENDIX B: DETAILS OF ELECTRICAL COMPONENTS Breaker Name Table XXII: Circuit Breaker Details Trip Rating Pole Current Interrupt Rating Manufacturer Model Main Breaker 100 Double 10 ka General Electric THQAL21100 Breaker for inside panel 50 Double 10 ka General Electric THQL2150 Outlets in Greenhouse 20 Single 10 ka Westinghouse BR120 Spare circuit in Greenhouse 20 Single 10 ka Westinghouse BR120 Greenhouse fans 20 Double 10 ka Cutler-Hammer BR220 Outlets near pond 20 Single 10 ka Cutler-Hammer BR120 Outlets near Festival Circle 20 Single 10 ka Cutler-Hammer BR120 Main Circuit Breaker 30 Double 10 ka Square D QO230 (Inside Panel) Outlets in Storage Shed 20 Single 10 ka Square D QO120 Lights in Storage Shed 15 Single 10 ka Square D QO115 Lights in Packing Shed 20 Single 10 ka Square D QO120 Outlets in Packing Shed & Straw Bale House 20 Single 10 ka Square D QO120 Table XXIII: Transformer Details Manufacturer ACME Transformer Catalog Number T S Style SR Primary Volts 240x480 V Secondary Volts 120/240 V Volt-Amp Rating 25 kva Phase Single Impedance 1.80% at 135ºC Enclosure Type 3R Outdoor Weight 250 lbs Table XXIV: Disconnect Switch Details Manufacturer Name Ampere Rating Poles Max Voltage General Electric Heavy Duty Safety Switch 30A 2P 600V AC

68 62 APPENDIX C: ETAP LOAD FLOW DIAGRAMS Figure 23: ETAP Load Flow - Min. Power Figure 24: ETAP Load Flow - "Daytime Working 1"

69 63 Figure 25: ETAP Load Flow - "Daytime Working 2" Figure 26: ETAP Load Flow - "Lunchtime 1"

70 64 Figure 27: ETAP Load Flow - "Lunchtime 2" Figure 28: ETAP Load Flow - "Evening"

71 65 APPENDIX D: PHOTOGRAPHS OF PS3000 INSTALLATION Figure 29: PowerSight PS3000 Installation Figure 30: Current Probe Connections

72 66 Figure 31: Voltage Probe Connections Figure 32: PS3000 Operating