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The University of Kansas School of Engineering Design Project A Sustainable Approach to Automobiles and Energy Infrastructure |
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We would like to thank the following sponsors in their gracious support of our smart grid efforts: |
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Solar Energy (Renewable Source #1)
Every day, the sun delivers 12.2 trillion watt-hours per square mile per year [1] of solar energy to the earth. This energy comes in limitless amounts and is completely free. Harnessing this energy is completely emissions-free, and most importantly, can be made portable, making it an obvious choice for the EIT. |
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Figure 2. The EcoHawk II: This year’s DIY Solar Panel |
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Figure 14. Waring Pro WPM25 popcorn maker |
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In this section, a number of tests are presented that provide more information about this appliance and our methodology for improving its performance. These values will help us determine the energy draw and help us begin optimizing the smart grid control architecture.
The first step involving data collection was to measure the actual power draw from the device. To this end, we performed a warm-up test along with a few popping tests. Plus, us poor hungry students had to take the opportunity to test the quality of the popcorn. As the figures below indicate, the average draw during the initial warm-up was 283.5W, to keep the popper warm was 71.2W and takes on average 282.4W and 3 minutes 20 seconds in order to pop a batch of corn. We noticed that removing the light-bulb in the device saves 10W and realized that more energy can be saved through possible insulation of the basket containing the oil and pre-popped corn. |
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Figure 15. Popcorn popper warm-up test and popping tests to measure power draw (popper basket is not insulated and the light-bulb is still installed) |
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Figure 16. Popcorn popper warm-up test and popping tests to measure temperature of the popper basket (popper basket is not insulated and the light-bulb is still installed) |
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Figure 13. Cobra 400-Watt Power Inverter |
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Figure 9. Will Power Deepcycle lead acid battery |
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Figure 10. The 12V A123 LiFePO4 Battery Pack with the BMS circuit chips |
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Figure 3. Eppley Laboratory PSM Pyranometer |
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Figure 4. USA Wind Generators 50 Watt Mini Turbine |
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Figure 11. Venom Pro Charger |
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Figure 5. Maximum Instruments #41 Wind Speed Anemometer |
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Figure 7. Xantrex C-35 PWM Charge/Load Controller |
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To prepare for potential savings due to insulating the basket, we used an infrared thermometer in order to measure the temperature of the basket. This will help us choose the right material and adhesive for insulation. As Figure 4 illustrates, the average temperature that we need to consider will be 180°F. |
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Figure 1. Overall schematic of the small-scale smart grid system |
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Wind Energy (Renewable Source #2)
As of September 30, 2009, 36,698 MW of wind power have been installed in the United States, and this number is quickly rising. [4] Thus, EIT will focus quite a bit of effort on wind energy acquisition and tracking. Kansas is rated14th in the United States for Current Installed Wind Power Capacity at 1026 MW at the end of 2009. Other Mid-west states such as Iowa, Illinois, and Oklahoma rank even higher, and thus wind energy is vital to an accurate infrastructure model [4]. |
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Fossil Fuel Energy (Conventional Source)
Fossil fuels are currently the main source of automotive and grid energy. In 2009, the United States alone consumed over 1 billion short tons of coal, producing over 1.8 billion metric tons of CO2. Although an ideal world would only use renewable sources of energy, coal-fire plants still sustain a vast majority of the base power consumption in the USA. In order to model this available energy, the EIT will be implementing a Generac iX800 800 watt gasoline generator (Figure 6). This will be used only when the renewable sources (solar/wind) cannot keep up with the demand. In the real utilities, coal and petrol-based fuels would cover the base amount of energy used every day, and renewables would be used to boost the electrical efficiency as well as lessen the peak demand on the large coal plants. |
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Overview
As you may know already, the EcoHawks try to incorporate all five E’s of sustainability: Environment, Economics, Ethics, Energy, and Education. In order to maintain this standard, the Energy Infrastructure Team (EIT) has decided to build a small-scale smart grid that will include all of the main focuses of the US Department of Energy:
1) Energy Sources – The EIT will be using a student-built solar panel and a 50W wind turbine to model renewable energy sources, and a gasoline generator to model the current energy infrastructure and its coal/petrol origins. The combination of these sources make for a well-rounded and scalable model of smart grid resources.
2) Control and Storage of Renewables – The EIT is working with a few different charge controllers and battery packs to model various ways of storing the energy produced by our solar, wind, and conventional sources.
3) The Role of Plug-In Hybrid Vehicles (PHEV) and Electric Vehicles (EV) – The EIT will be using an RC battery pack using Lithium-Iron-Phosphate (LiFePO4) batteries to model the new PHEV and EV coming onto the market. The main focus will be the potential effects (both positive and negative) these vehicles will have on our current energy grid versus a new and improved grid.
4) The Customer – The customer is hands down the most important part of any plausible design. We will be using a 300W popcorn maker to grab the attention of any passers-by in an attempt to spur interest in renewable energy. We will also be using it to model the regular energy draw on the grid similar to that of everyday household/office use.
5) System Control, Data Acquisition, and Analysis – No good research/design project is complete without tracking every bit of data possible. We will be using National Instruments’ LabVIEW to track and control our smart grid. This is the heart and soul of our smart grid, as it’s not “smart” until we program it to be so. |
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Figure 6. Generac iX800 800 Watt gasoline generator |
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Control and Storage of Renewables
In order to optimally charge our Lead-Acid battery storage bank with solar energy, the EIT have used a Xantrex C35 Photovoltaic Charge Controller (PVCC) (Figure 7). This PVCC was chosen for its ease of use, low energy draw, and available charge cycles. The main charge cycle has three phases: bulk, absorption, and float. The bulk charge phase allows unlimited current flow (up to 35A for the C35 model) charging the battery to a user-set “full” voltage. |
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Role of PHEV and BEV automobiles
For many years, Plug-In Hybrid and Battery Electric Vehicles have been viewed as a power sink, and a highly variable sink at that. However, new studies show that PHEVs and BEVs can act as a grid stabilizer when used strategically. |
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Figure 12. Elithion Lithiumate Battery Management System |
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The original solar panel created by the EcoHawks boasted a powerful 27VDC and 3.5A on a bright sunny day. This is obviously much higher than the 16VDC desired to charge a 12VDC battery (need a few extra VDC just to ensure a positive ratio). Doing some quick math, each cell was producing about 0.56VDC and 3.5A. This is only a 0.1A decrease with respect to manufacturer’s specifications indicating a correct building methodology. However, due to the fact that very few efficiency drops were suffered, the solar panel has been oversized by nearly 50% of its required voltage. Thus, a second solar panel has been built (The EcoHawk II)
This new solar panel in Figure 2 provides 17.4VDC and 3.3A on a clear day. The main focuses of the new panel were making it smaller (to waste fewer solar cells), lighter (for easier transportation, making it truly portable), and we wanted it to be a bit more aesthetically pleasing. Thus, the EcoHawk II was fabricated using coroplast backing, 18 gauge wiring, only 32 Everbright Polycrystalline Solar Cells (as opposed to 54 in the original panel), and a frame consisting of 1” square aluminum tubing with press-fit joints. This new panel weighs only 11.2 lbs, roughly 40% of the original panel weight. Overall, we have attained an efficiency of 94.6% when compared to the manufacturer-stated power output, reaching just under 60 watts.
Finally, an Eppley Laboratory PSM Pyranometer (Figure 3) will be implemented. This device measures solar irradiance by allowing light to hit a photodiode which creates a small current and converts that to a voltage between 0 and 12mV [2][3]. The voltage output can then be converted using a calibration factor to a measurement of maximum solar energy in watts per square meter. The pyranometer will be used to determine the available solar energy and operating efficiencies of the solar panel. This pyranometer is different from last year’s SDL1 Solar Data Logger because the irradiance measurement taken is independent of direction, meaning that we get a measurement that is accurate for an efficiently designed solar tracking system, a hopeful future addition. |
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The EIT will be using a USA Wind Generators 50W mini turbine (Figure 4) to model this vast amount of renewable energy. This turbine can produce up to a measured 16.0VDC with 1.55A, to give a manufacturer-based efficiency of 49.6%. Although the efficiency is rather low, it is plenty enough energy to keep a 12V lead acid battery topped off for occasional use such as on a boat or RV. At a price of $80, EIT believes this shows a great proof-of-concept for the wind energy potential on not just the large-scale utility use, but also for local, on-site use.
As the first EcoHawks bout with wind energy, the EIT plans to take great care to track every aspect of energy capture, and thus will implement a Maximum Instruments #41 Wind Speed Sensor (Figure 5) Using this basic anemometer, we will be able to create a power output-versus-wind speed plot to show the efficiency of our wind turbine. Using various DoE-supplied statistics, one can get a general estimate on an efficiency based on long-term averages, but with our anemometer, we will be able to get a real-time efficiency rating.
The use of wind energy is already wide-spread, but the EcoHawks want to show how one can get the most out of the energy through using optimum storage and control schemes. For example, the use of PHEVs can either increase demand at peak hours, or with the proper control scheme can actually decrease the demand from conventional power sources through Vehicle-to-Grid (V2G) technology. This methodology and others will be discussed in more detail in later sections. |
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In V2G technology, the smaller generators in some PHEVs can potentially be used while plugged in to generate the necessary power for sudden increases in power demand. The generators in series hybrid vehicles are designed to be extremely efficient small motors that are only used to charge the batteries when necessary. Thus, the use of a small generator in a smart grid isn’t that far-fetched. However, due to the power output difference between the generator and our renewable sources (800W vs 110W) gives a better representation of the large coal plant production versus wind/solar farm production [5]. |
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As it approaches the full voltage setting, it switches into the absorption stage during which the current slows over the course of thirty minutes to an hour. This setting is used to bring the battery gradually to the full voltage to ensure a safe charge. Once the battery reaches the final voltage level, it switches to float stage in which it reduces the current flow to under 1A. This setting is used to ensure that the battery stays at its optimum level
The charge controller scheme for our wind turbine is a bit different from what would conventionally be used. The fact that our wind turbine outputs a generally low current (on the order of 1A) means that there is no need for a bulk charging phase, as it would merely allow the same level of energy as a float or trickle phase. Thus, to optimize economic efficiency, the EIT has decided to merely implement a simple switch board and a polarized diode to control our energy flow. This basically allows us to manually turn on the charge, while the diode protects the battery from a back-flow of energy discharging our battery bank. For a larger wind turbine, a charge controller similar to the Xantrex C35 would be used to ensure the battery does not get overcharged causing a catastrophic failure.
To simulate renewable energy storage in the small-scale model, a deep cycle 75 Ah (C/20) Optima D31M 12-volt lead acid battery (Figure 8) will be used as the primary energy storage medium for the solar panel and wind turbine. The C/20 rate means that this battery has the capacity to supply 3.75 amps (75/20) for 20 hours. [6] This battery has a high capacity and can recover from deep discharges without hindering long term performance. The Optima brand is well known as an industry leader in quality and most importantly, this battery was donated to EcoHawks for this application. The Optima battery will serve as the primary energy supply for a small popcorn maker appliance. A secondary lead acid battery, an Everlast 90 Ah battery (Figure 9), will be used as a power supply for the sensor and control system equipment as well as a reserve power supply for the appliance. This battery was selected due to its similarity to the Optima battery. |
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Figure 8. Optima Blue Top Lead Acid Battery |
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In the current infrastructure, there are two main power sources: bulk power and reserve power. Bulk power is produced by the standard coal-fire and nuclear power plants. These plants work most efficiently when run at a constant rate for long periods of time. Thus, these large-scale plants are used to cover the average power used throughout each day (such as from refrigerators and other large appliances that are always on). However, these massive plants do not do well in covering the 3 to 6 pm air conditioning/cooking peak energy draw. This energy comes from many different sources, typically smaller, more local power plants that are more easily adjusted for load control. This is where PHEVs and BEVs can come into play.
There are two ways one can charge their electric vehicle. The first is they plug the car in as soon as they get home from work and add to the peak power consumption of the daily cycle. The other method is to wait to charge the car until 2am when the energy use on the grid is at a minimum. This wouldn’t necessarily decrease the current peak demand, but it would increase the minimum energy demand, leveling the playing field, so to speak. On a macro scale, this would inevitably lead to a higher electrical energy consumption, yes, but the power created could come from the large, highly efficient nuclear and coal plants and less from the smaller, less efficient reserve sources.
In order to model this effect, EIT has built a “smart battery pack” consisting of 4x 3V LiFePO4 cells. (Figure 10) These are the same batteries used in the Chevy Volt PHEV, and thus are an accurate representation of the potential power sink.
To charge the battery pack, EIT has implemented a Venom Pro Charger capable of charging up to 6 lithium cells in series – perfect for our application (Figure 11). Using this charger, we will be able to charge our cells up to a combined 12V safely, ensuring we do not overcharge the cells. This charger represents what would be the charger installed in the vehicle owner’s home, work car port, or even downtown parking garage. [7] This charger doesn’t necessarily have to be a smart charger.
EIT wants to show how EVs and PHEVs can have control systems safeguarding the energy levels of the individual battery packs in each car. Thus, the batteries will be controlled by our Elithion Lithiumate Battery Management System (Figure 12), ensuring that the lithium cells are protected and maintained correctly. This unit basically checks to make sure the voltage level and power draw from each individual cell are equal, thus preventing a critical discharge of any of the individual cells. This BMS is similar to the control system that would be held within each PHEV or BEV, made custom for each battery pack, and thus is a good representation of a macro PHEV fleet.
Finally, EIT needed a way to provide standard power from the DC battery bank. Thus, the team has implemented a Cobra 400-Watt Power Inverter (Figure 13) that will take in the 12VDC power from the battery pack and convert it to 120VAC, 60Hz power similar to that from any standard US wall socket. This unit basically makes the stored energy usable by the common household appliance. |
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Customer
For a demonstration project, we wanted to catch the attention of people as they walk by or come up and talk to us. Everybody loves popcorn and this appliance is relatively easily to move around. Finally, the manufacturer actually states the power draw on the device (300W). This gives us a great way to start sizing the rest of our items. |
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System Control, Data Acquisition and Analysis
The goal of EIT’s project isn’t merely to show that a smart grid can be built. As engineers, we have an undying urge to know every little detail about every component in our system so we can let our nerd flag fly and tell everyone we can find about the system. To help us with this endeavor, we will be measuring the current flow, voltage levels, and power usage (among other things) at each point in the system so we can fully analyze the efficiency of each component. To perform the measurements, we are implementing National Instruments hardware (Figure 17). However, with all the different components and values we will be measuring, things can get pretty messy. Thus, we will be using a CRio chassis to hold and maintain the NI Hardware (Figure 17). |
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Finally, LabVIEW software will be used to create a control scheme and efficiency calculator. The program has been written by EIT’s own Nick Surface. Using LabVIEW, an easy-to-use graphical user interface will be created, making smart grid technology accessible to the average American consumer.
Similar control systems have already started to be installed across America. For example, Lawrence, Kansas has been lucky enough to be chosen as a test subject for Westar Energy’s SmartStar program. As of January, 2011, 1400 SmartStar meters have been installed in local businesses and residences for testing purposes. These smart meters will give the individual customer a real-time reading of their power consumption, as well as daily, weekly, and monthly averages [8]. This is the beginning segue into what could potentially turn into V2G technology. |
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Figure 17. The NI Hardware and CRIO Chassis |
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Other Potential Future Energy Sources
Ideally, these renewable sources will not be the only options for a local smart grid. For example, geothermal heat pumps can be used to drastically reduce energy use for HVAC, water heating, and other similar applications. These work in the same way as a refrigerator, except the source energy is drawn from the ground through a series of buried heat coils. These systems can cost anywhere up to $40,000 for a complete installation for an existing large-sized home, but this is quickly paid back through lowered utility bills over the course of as few as five to ten years [9]. |
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Another viable source of energy is hydro-electric power. Washington state alone produced over 54,000 thousand Megawatt-hours of energy. This vastly outnumbers any other state an average of 25 times over. A total of nearly 180 million megawatt hours was produced in 2010, so this is very significant amount of power produced. [10] For another example, the Hoover Dam alone produces an astounding 4 billion kilowatt-hours of hydroelectric power each year. This is enough energy to serve 1.3 million people. The best aspect of hydro-electric power is it is consistent. Unlike solar or wind energy, there is a constant amount of power being generated at any given time, making it act like the large coal-fire and nuclear power plants. The one major drawback is it typically incorporates damming a major river, which can have very detrimental effects (Such as the flooding due to the Three Gorges Dam of China’s Yangtze River) [11].
Of course, there are hundreds of ways to generate power that we are not using in our smart grid. Examples like geothermal and hydro power aren’t very easily made portable. The focus of this year is mainly to show how individual homes and customers can benefit from smart grid technology. The EcoHawks would love to eventually explore all of these energy sources, but for right now, we want to take it one step at a time. |
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Figure 18. Three examples of Geothermal Heat Pump Loops (From Left to Right, Pond, horizontal, and vertical layouts) [12] |
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Figure 19. Flooding before and after the installation of the Three Gorges Dam of the Yangtze River, China. [13] |
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References
1. “How Much Solar Energy Hits the Earth?” Ecoworld – Nature & Technology In Harmony. Web. 16 November 2010. <http://www.ecoworld.com/energy-fuels/how-much-solar-energy-hits-earth.html> 2. Lindley, David. "Smart Grids: The Energy Storage Problem." Nature, Jan. 2010. Web. 31 Oct. 2010. <http://www.nature.com/news/2010/100106/full/463018a.html>. 3. Fletcher, Lisa, and Andrea Beaumont. "Boulder, Colo.: America's First 'Smart Grid City'" ABC News, Nov. 2008. Web. 31 Oct. 2010. <http://abcnews.go.com/GMA/SmartHome/story?id=6255279&page=1>. 4. “Wind Powering America: U.S. Installed Wind Capacity and Wind Project Locations.” U.S. Department of Energy. Last Updated: 12/21/2010. <http://www.windpoweringamerica.gov/wind_installed_capacity.asp>. 5. “Electric Power Monthly.” U.S. Energy Information Administration Independent Statistics Analysis. January 14, 2011. <http://www.eia.doe.gov/cneaf/electricity/epm/epm_sum.html>. 6. “A Guide to Understanding Battery Specifications. “ MIT Electric Vehicle Team. MIT. Web. 11 Dec, 2010 <http://web.mit.edu/evt/summary_battery_specifications.pdf>. 7. “Get the charge: Some Chicago garages plug in electric cars.” Matthew O’Connor. Medill Reports Chicago. Northwestern University. 2001-2010. <http://news.medill.northwestern.edu/chicago/news.aspx?id=177382>. 8. Westar Energy SmartStar. 2011 Westar Energy. <http://smartstarlawrence.com/>. 9. “Geothermal Heat Pumps.” California Energy Commission, 2006 – 2011. <http://www.consumerenergycenter.org/home/heating_cooling/geothermal.com>. 10. “EIA Renewable Energy – Hydroelectric Data and Information.” January 14, 2011. U.S. Energy Information Administration, Form EIA-923, “Power Plant Operations Report.” <http://www.eia.doe.gov/cneaf/solar.renewables/page/hydroelec/hydroelec.html>. 11. “Environmental Impacts.” January, 2011. World Politics 116, Mount Holyoke College. December 19, 2005. <http://www.mtholyoke.edu/~lpohara/Pol 116/enviro.html>. 12. “Birds-Eye.Net “Green” House: Exploring Energy Efficiency Using Geothermal Heat Pumps.” Andrew Lake. Birds-Eye.Net. January, 2011. <http://www.birds-eye.net/house/heating_and_ac/exploring_energy_efficiency_using_geothermal_heat_pumps.htm>. 13. “China – Hydropower as the right solution? – Our energy.” Our Energy. January, 2011. <http://www.our-energy.com/china_hydropower_as_the_right_solution.html>. |
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Energy Infrastructure |