INVESTIGATOR: Mish, S.

PERFORMING INSTITUTION:
EWINDSOLUTIONS LLC
30678 SW ORCHARD DR
WILSONVILLE, OREGON 97070

CONTINUED DEVELOPMENT OF AIRBORNE WIND ENERGY SYSTEM GROUND STATION

NON-TECHNICAL SUMMARY: Airborne Wind Energy (AWE) is still a relatively new field but is growing quickly. There are approximately 13 other AWE companies worldwide that appear to have the technical competence and realistic understanding of business such that we view them as realistic competitors. As we have detailed above, eWind differentiates itself from them by focusing on following current FAA (or European) flight rules, staying small and competing against the traditional small wind market with a better value proposition and being able to go straight to selling systems to farmers without bureaucratic waivers.There is increasing business focus on the field, there is increasing university funding to study basic problems common to most AWE systems. TU Delft, a university in the Netherlands, is a leader in this field and has even started a fledgling academic department focused on it. This has produced numerous papers and theses dedicated to various problems of AWE (e.g. Ahrens et al. (2014); Fagiano (2009); Haug (2012)). In addition, there have been publications about simplified control systems and prototyping lessons and guidelines (e.g. Fagiano (2012); Fagiano et al. (2013); Fagiano and Marks (2014); Fagiano et al. (2014); Zgraggen et al. (2014)). Unfortunately, much of this work has centered on soft kites with multiple tethers that allow control systems for the airborne device to be placed on the ground.While we agree that this greatly simplifies the control system problem, the cost in drag (and, thus, electricity production) of additional tethers makes the business and financial case for these systems tenuous at best. AWE represents a significant increase in mechanical and control complexity and, thus, must also come with an even greater increase in energy production and value to make financial sense to farmers. Additionally, soft kites (imagine a kite-boarder or para-sail) are very likely to be harder and costlier to maintain in the field for years at a time. In short, rigid frame crafts (such as ours) are more efficient, rugged and easier to launch and land. Conversely, they are less studied, harder to control on a single tether, and less stable, requiring a more robust control system to manage them.The other major category of AWE is called "sky-gen". In this case, the generator is placed on the flying craft itself (as opposed to on the ground) and the electricity is transferred down the tether. There are numerous benefits and disadvantages of both sky-gen and ground-gen. There is a legitimate business case to be made for each one within certain operational regimes. However, while sky-gen is likely better at higher altitudes (i.e. greater than 1000m), ground-gen is better at the altitudes currently allowed by regulations (i.e. below 150m). Companies such as Makani are pursuing sky-gen systems, but because of this height/efficiency tradeoff, they are building utility scale systems that require individual waivers from the FAA to even test. This is not an appropriate model for farmers.As previously detailed in Section 3, we have based our design around the needs of small farmers. We maximize the financial return to farmers while following all current regulations and permitting, allowing the customer to reap the benefit as easily as possible. This focus leads us to the rigid frame flying craft, a ground-gen system and automating the system to minimize farmer involvement. This approach places a greater burden on the research and development side by increasing the design complexity of TED, its controls and the flight software.Previous work on our system has focused on TED, its aerodynamic design and physical control surfaces. This work has already led to a utility patent 9,643,721 titled "Wind Energy Conversion System, Device and Methods" that was issue 05/2017 it covers a flying system with multiple lifting surfaces and side rudders to maximize lift in a given wingspan and improve maneuverability, as well as it's flight path. As noted earlier, we will submit another disclosure for stability control features that enable a rigid frame kite to have soft kite like stability which minimizes the need for onboard power consumption to otherwise achieve that stability.Previous work (published) on ground stations is relatively minimal. Fagiano et al. (2014) is one of the few who details the decisions and trade-offs in tether control systems. However, as previously mentioned, they operate a soft kite, a very different scenario from our system. We will still consider the sensor systems they detail (modified to our needs) as viable solutions for part of the ground station.

OBJECTIVES: Group I:Determine the optimal power generation configuration (generator, gearbox, inverter, reel in motor, battery, etc.) of mainly off the shelf components placed directly after the tether drum to:Supply 5 kilowatts of electrical output power (common size generator)120 or 230 VAC (using the appropriate transformer outlet) at 60 Hz single phaseProvide 2 hours of battery backup capabilityOutput power should meet utility power quality requirementsThis is approximately the power required to run a 5 HP Deep Well Submersible Pump or similar sized Irrigation Pump that might be used on a farm.Note: without a utility grid tie, providing the system nameplate capacity (11.6kW or 100% of the electricity used on average) would greatly exceed the farm's instantaneous electricity demand on a regular basis, forcing the need for a larger dump load or battery backup system (more likely at night when the electricity demand is lower, but winds are higher).Group II:Design, build and test a functional 5kW airborne wind energy ground station system, complete with the following key sub-system components (this is building upon and a substantial expansion and scaling up of the phase I ground station activity):Wind tracking system such that the ground station can pivot as requiredGround station frame assemblyTether drum and tether cross spooling controlMeasurement sensors for wind speed, tether reel speed, environmental, tether angleA separate reel in motor if required.Ground station soil anchoring systemA weatherized ground station enclosure with service accessEnclosures and access panels for the main electrical power generation equipmentExterior electrical connection, customer interface, status lights and emergency shut offSpace for a small battery backup systemGroup III:Design, build and test a system performance monitoring system for ongoing tracking of key system performance metrics (phase I focused on measurements of tether tension and tracking, while Phase II will focus on the entire ground station system) such as:Wind speed/direction and tether release speedMechanical and electrical power generatedOccurrence of soft and hard faultsTo increase test hours on non-windy days, design and build a 5hp tether tension simulatorGroup IV:Compliance with current Federal Aviation Administration regulations regarding the need for flag and lighting requirements and potential changes being considered as they apply to AWES (This is an expansion of PI activity and more direct engagement with the FAA).Specially the following regulations:FAA title 14 (Aeronautics and Space) → Chapter I → Subchapter E → Part 77 (safe, efficient use, and preservation of the navigable airspace)FAA title 14 (Aeronautics and Space) → Chapter I → Subchapter F → Part 101 (moored balloons, kites, amateur rockets, unmanned free balloons, and certain model aircraft)FAA Advisory Circular 70/7460-1 Obstruction Marking and Lighting Finally, we must address the time duration of TED flight which also impacts test time on the ground station energy generation system while also collecting reliability data. This is challenging given our dependency on local weather conditions. Thus, we have decided to place flight time duration as a "stretch goal" for this grant to get at least 20 hours of cumulative outdoor test time utilizing TED and the ground station. Concurrently, we would track the total power generation time at a system level and any failures that occurred in order to begin building a runtime and reliability growth curve as well as a corrective action plan where needed.

APPROACH: Further develop and implement the aerodynamic analysis of the tether. Expand on the success of the Phase I project in the areas of tether management system. This includes, sensors, tether guides, and temporary tension control mechanisms. Utilize the testing apparatus that was developed and built in the Phase I project for further testing and development of the ground system. Further development and implementation of the software control system and tether management system.

PROGRESS: 2018/09 TO 2019/08
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Stay the course as described above. Continue developing the back end of the system thru a partnership with Burnshire Electric (also a USDA Phase II funded company). We are directly working with the FAA in forming policies for AWE development and will continue our dialogue regarding outcomes in field testing. We will continue working with our LARTA advisor, Peter Hong and will submit our final CSR in November 2019.

IMPACT: 2018/09 TO 2019/08
What was accomplished under these goals? 1. The first objective was selecting a generator technology given the three primary architecture choices of: DC, induction, or synchronous generators. We will control the rotation (in both directions) electronically by varying the back-EMF within the motor. 2. We chose to output power as 230VAC. The end product will output smoothed 230VAC power to be used directly by farm equipment or passed through a net-meter to the grid. 3. We made a slight pivot regarding the 2-hour battery backup capability outlined above. In depth analysis determined that in the event of a "system power disconnect error", the quickest and safest response is to immediately dock/secure the TED and halt energy production. Summary: 100% complete - finalized decision to use AC induction motor/generator 100% complete - finalized decision to use 230VAC output to grid and/or equipment 100% complete - revised battery backup requirement to 20min 100% complete - selected equipment will meet power quality requirements Progress and deviations to original plan of group II Frame Design - 70% complete - the frame is constructed from 80/20 T-slotted Aluminum Extrusions, Figure 3. This material system is highly modular, easily modifiable, and includes a variety of components to enable weatherization, cable management, and linear motion. Tether drum and cross spooling - 80% complete - The tether storage drum is currently of wooden construction, is mounted to the drive shaft by use of flanged clamps, and mounted to the frame with pillow block bearings. With the second half of the funding we plan to replace the drum with a more robust custom built all-aluminum one. System Sensors for: wind speed, drum rotation, environmental, tether angle - 50% complete Secondary motor - 100% complete - Because of the architecture of the generator selected, a secondary reel-in motor is not required. The generator will control all functions for tether deployment, rotational braking, and retracting tether during power cycle reset or docking. Ground anchoring - 70% complete - One of the main selling points for our system is that it is highly portable. Therefore, we needed to find a method of temporarily securing the station to the ground that is effective, reliable, and removable without disrupting the ground. Earth screws are our solution. They are simple to install (via handheld impact wrench or T-handle), effective at anchoring the station for as long as needed (will not creep loose), and easily removed with minimal equipment and damage to the site. Weatherized enclosure - 50% complete - Because the system will be outdoors throughout its operational lifespan, appropriate weatherization must be implemented to protect the equipment, customers, and technicians. We are striving to achieve protection rating of NEMA 3 which is defined as: Enclosures for power generation and smoothing equipment - 20% complete - the equipment is contained within a NEMA-3R enclosure mounted on the station frame, shown in Figure 4. This enclosure will house the inverters, metering equipment, motor controllers, and display interfaces provided to us by Burnshire Hydroelectric. Electrical connection, customer interface, status lights, and emergency shut-off - 10% complete - will be developed during the second half of the grant once control systems are developed and we have determined the appropriate configuration of these features. Space for Battery Backup System - 50% complete - A small battery backup system is necessary to retract and store the aerial device in the event of a power loss error. Summmary Wind Tracking - 70% complete - need to order and install components Frame Design - 70% complete - will make adjustments as needed Tether Drum and Cross Spooling - 80% complete - order and install components System Sensors - 20% complete - install and program sensors Secondary Motor - 100% complete - deemed unnecessary Ground Anchoring - 70% complete - selected, need to order Weatherized Enclosure - 50% complete - design complete, need to order and install Power Generation and Smoothing Equipment Enclosures - 20% complete - contracted design and construction, awaiting delivery of equipment GUI and Safety Lighting - 10% complete - system control software development required to determine and incorporate GUI features Battery Backup - 50% complete - battery backup design complete, need ordering and installatio 65% Total Completion Progress and deviations to original work plan of group III 1. Wind speed/direction and tether release speed - currently only tracking wind speed and tether release speed; update/incorporate wind direction and real-time tracking of TED positioning relative to the ground station. 2. Mechanical and electrical power generated - currently calculating power generation potential using mechanical torque sensor; update/incorpoirate generator's actual power generation and power smoothing equipment efficiency/optimization 3. Occurence of soft and hard faults - currently not tracking error/faults in software; update/incorpoaret tracking while testing in the field and in the lab. 4. Tether tension simulator - currently have hardware and software sized to function with the Phase I ground station; need to upgrade the hardware function with the 5kW station and upgrade software to be more robust and incorporate larger variety of wind conditions (eventually using data collected during field tests for more realistic "practice") Summary: 30% complete - update existing software and incorporate more functions 30% complete - update existing and add all power generation tracking functions 0% complete - develop/implement error/fault tracking software 20% complete - update hardware (more robust); update software (more robust) to record and practice with real-world wind profiles. 20% Total Completion 6. Progress and Deviations to Original Work Plan of Group IV eWindSolutions had a discussion with FAA representatives on March 8, 2018, just a week after the submission of this Phase II project proposal. The FAA is considering and examining regulation changes regarding the operation of airborne wind energy devices in navigable airspace. In summary, the proposed regulation changes (to remove flags and lighting requirements on the tether) removes a key system performance restriction and, as a result, has a positive impact on the commercialization of airborne wind energy technology. 7. Update on Phase II Commercialization Objectives Larta principal advisor Peter Hong and USDA ACT leader David Schaefer have been working together on eWind's commercialization strategy and have completed several tasks outlined in the Larta Commercialization Objectives/Prioritization Schedule. Additional funding has been a main goal for eWind and we have recently been awarded a $100k grant from the State Of Oregon to assist in completing the following objectives outlined in our CP: additional IP patent submissions for the ground station, strategic business planning & partnerships (we are collaborating with Balsa Group and Elevator), market entry strategy development, and improving our business model to attract high-level investors both in the US and abroad. We are in the final stage of hopefully closing a round of Revenue Based Financing with the Canadian Investment Group, David Haig & Associates, CA. This funding will allow us to hire personnel for key positions which will accelerate our timeline for BETA testing and finally commercializing the technology. As discussed above and per our CP objectives, we are continuing our involvement with the FAA as they develop rules and regulations for the AWES industry. 8. Midterm Summary: During this first half of the project, we have made the driving architecture decisions, completed the design work, and have made headway on construction of the physical components of the ground station.

PUBLICATIONS (not previously reported): 2018/09 TO 2019/08
No publications reported this period

INVESTIGATOR: Mish, S.

PERFORMING INSTITUTION:
EWINDSOLUTIONS LLC
30678 SW ORCHARD DR
WILSONVILLE, OREGON 97070

DEVELOPING A GROUND STATION FOR AIRBORNE WIND ENERGY SYSTEM

NON-TECHNICAL SUMMARY: The tether and power generating ground station,are the focus of this proposal. Both these systems have challenges that are unique to the airborne wind energy field. First is the selection and design of the tether itself. This includes the material (e.g. nylon, steel,or composite) and whether to weave in electricity-transmitting wires between the ground station and the flying craft (which would increase its cost and diameter). These wires would be used to power the electronics on the flying craft and facilitate communications with the ground station. All these choices have trade-offs,however. Specifically, the tether will be the main source of aerodynamic drag in the entire system and, thus, one of the key limiting factors in the quantity of electricity produced. The other key system is the ground station itself. This includes several components: the drum and tether management system, electrical generator,and electrical systems that convert noisy renewable energy into smooth, reliable 120V AC for equipment or home use. Conveniently, these converting electrical systems are relatively abundant and a set that fits our exact needs is either commercially available or created with minor modifications. The tether management and electrical generator, however, are much more complex and not commercially available. The tether management system, a combination of custom hardware and custom software, must reliably:-Maintain a desired tension on the tether -Monitor tether tension, reel-out speed, tether-to-ground angle, length deployed, etc. -Maintain reel-out speed to a specific value determined by the wind speed -Monitor and maintain airspeed of the flying craft during launch/landing -Reliably guide the tether onto the drum without crossing layers In aggregate, this creates a complex system of mechanical controls, sensors and software that must work together to maintain consistent flight, maximize power generated, and minimize wear on each component. To maintain consistent tension on the tether requires constantly monitoring and adjusting for differing pull strengths from the flying craft because of changes in wind speed (gusts, lulls) and different aerodynamic lift at each point of the figure-8 flight pattern. To maximize power generated, we do not want any spring or physical braking system to smooth out the tether tension because these forces create drag and friction, wasting energy. Instead, we will use the electrical generator itself as the resistance and rewind motor. A generator and motor are the same physical system, differentiated only by whether electricity is flowing into or out of the device. Therefore, by monitoring the tether tension and reel-out speed, the tether management system can adjust the electrical load (resistance) of the generator to control both variables. The system can also use the generator as a motor to rewind the tether each cycle. In short, by constantly monitoring and maintaining several variables of the system, the tether management system can maximize power generated by clever manipulation of the electrical generator. It must also perform all these tasks flawlessly over the ten-year lifespan of the device while exposed to degrading UV radiation and seasonal weather. Ensuring this level of accuracy and reliability over a decade is a complex engineering challenge. Finally, the electrical generator is novel because it represents one of the biggest advantages our airborne wind energy system has over traditional wind turbines and other airborne competitors. Generators on top of large towers or that are airborne have a premium placed on size and weight for obvious reasons. As a result, they are built from exotic, magnetic materials (e.g. metal-doped ceramics) that are extremely delicate and expensive. They are also physically small. This feeds directly into the fundamental trade-off in generator design: a physically small generator equals higher revolution speeds (e.g. 1,500-2,000 revolutions per minute (r.p.m.)) while a physically large generator equals lower revolution speeds (e.g. 50-80 r.p.m.). For traditional wind towers, this is a double blow because the input speed of their massive bladesisonly a few r.p.m. Thus, they must insert a gearbox to increase that blade revolution speed to match the speeds required by their physically small generator. These gearboxes not only decrease the efficiency of the system (a 3-10% loss is considered typical for commercial gearboxes) but are also the most likely component to fail, typically lasting seven years in a twenty-year turbine lifetime (Townsend, 1991; Windpower Monthly, 2005). To add insult to injury, they are also approximately 13% of the cost of the entire wind turbine (EWEA, 2009). This combination of small, expensive generator and expensive, inefficient gearbox is required by the need to make the system physically small and lightweight to fit atop a tall tower. Our airborne wind energy system has none of these constraints, however. Because we place the generator on the ground, its size and weight are relatively meaningless (within reason). In fact,becausethe ground station will likely have to be weighted or secured to the ground to ensure the flying craft does not pull it downwind, a moderate amount of extra weight is actually a minor benefit. This ability to physically scale the generator to meet our input and output needs gives us a large efficiency and cost advantage over traditional wind turbines. Becausewe also have a low r.p.m. input, instead of needing a gearbox, we will simply make the generator larger to accommodate the lower r.p.m. source, immediately saving money, complexity, and maintenance. In our system, the generator will be roughly 4-5 feet across and weigh approximately 250-300 pounds. This larger size has several beneficial knock-off effects as well. Electrical components are larger, more robust,and actually cheaper than their miniaturized versions. Also, we do not need the fragile, esoteric magnetic materials, relying instead on either traditional high-strength rare-earth magnets or electronically controlled electro-magnets. The drawback of our generator is that fact that it currently does not exist. Commercially available electric generators are almost universally skewed towards being physically small with higher r.p.m. Fortunately, the physics governing generators is straightforward and we have already built several functioning prototypes. In summation, designing and building our own generator will decrease the economic risk of rare-earth magnets and greatly decrease its cost in exchange for the increased burden of more complex research and design task. In addition to the flying craft, tether,and power generation system, there are secondary technical components that must be developed and incorporated into the final system before it will successfully meet the needs of small farmers. These include: automated launch/recovery with the ground station, ground station/flying craft communication, rectifying and smoothing variable renewable power, flying craft onboard power and electronic controls. While none of these are trivial development tasks, we believe they are all addressable based on the experience and expertise of other emerging fields and industries. Most applicable are the burgeoning field of unmanned aerial vehicles research and the accompanying plethora of private drone companies. For example, a number of drone companies have already developed methods for drone launches and recoveries (Insitu, 2014; Honeycomb, 2014).

OBJECTIVES: This Phase I project is focused on the design and development of the power generating ground station. This comprises the tether and its aerodynamic effects on the system (including the FAA mandated safety flags), as well as the mechanism and software that will manage the tether and control the tension, reel-out speed, and rewind, to maximize the return on investment for our farming customers. Our system is designed around the needs of small farmers in rural communities. Therefore, the goal and emphasis of this project is to produce a smaller system (11.6kW nameplate capacity) that will, with our predicted capacity factor, produce close to the electric energy used by the average small farm. We have chosen to place the generator on the ground, flying a rigid or semi-rigid winged craft in a crosswind pattern, utilizing a single tether, flying below the current FAA limit of 499 feet (150m) above the ground.There are three main components to our airborne wind energy system. First is the novel flying craft itself. Our design choices (crosswind flight, ground generation, ridig to semi-rigid wing) have created the need for a novel, complex flying craft. Its development is progressing quickly under the support of a previously awarded Phase II grant.The tether and power generating ground station are the focus of this project. Both have challenges that are unique to the airborne wind energy field. The ground station, which includes the drum and tether management system, the generator and electrical systems that convert noisy energy into smooth, reliable 120V AC. Conveniently, these converting electrical systems are realtively abundant and a set that fits our exact needs is either commercially available or created with minor modifications. The tether management, a combination of custom hardware and custom software, must reliably: a) maintain a desired tension; b) monitor tether tension, reel-out speed, tether-to-ground angle, and length deployed; c) maintain reel-out speed to a specific value determined by the wind speed; d) monitor and maintain airspeed of the flying craft during launch/landing; and e) reliably guide the tether onto the drum without crossing layers.The goal/desired outcome of this project is: create a complex system of mechanical controls, sensors, and software that must work together to maintain consistent flight, maximize power generation, and minimize wear on each component.

APPROACH: Evaluation:We will use a previously completed aerodynamic analysis of the tether to select a tether material and diameter, and design the safety flags and lighting. We'll design and build the physical components of the tether management system. This includes sensors, tether guides, and temporary tension control mechanisms. Build a testing apparatus that will simulate the flying crafts force by pulling on the tether. Design and program the software control components of the tether management system. Combine with the physical components to create a prototype tether management system.

PROGRESS: 2017/09 TO 2018/04
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

IMPACT: 2017/09 TO 2018/04
What was accomplished under these goals? We consider this Phase I work to be very successful as all our deliverables were achieved. A functional prototype ground station and test apparatus were designed, constructed, tested, and modified as needed to meet the requirements. A significant amount of software was developed to control the electro-mechanical drive and measurement systems. A software bug and archive system was initiated to aid in the development and documentation control. Motion profiles were constructed to simulate real-world TED to ground station interactions. We will continue to utilize this equipment to initiate further design and controls development as well as further system fatigue and reliability testing at operating levels of power and line speed approaching our proposed commercial system (12kW and 8 meters/sec respectively). While there remains a significant amount of work before the system will be commercially ready, the results from this Phase I effort reaffirms our confidence that we will be successful. We look forward to bringing a low cost, highly efficient renewable energy sysytem to farmers of the world.

PUBLICATIONS (not previously reported): 2017/09 TO 2018/04
No publications reported this period.

Item No. 2 of 2

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INVESTIGATOR: Schaefer, D. B.

PERFORMING INSTITUTION:
EWINDSOLUTIONS LLC
30678 SW ORCHARD DR
WILSONVILLE, OREGON 97070

CONTINUED DEVELOPMENT OF A NOVEL NEXT GENERATION AIRBORNE WIND ENERGY SYSTEM FOR SMALL AND MID SIZE FARMS

NON-TECHNICAL SUMMARY: As Oregon farmer and Organically Grown Company (OGC) executive director Andy Westlund confesses, being one of the 800,000 small commercial farmers in America is challenging (Hoppe, MacDonald, & Korb 2010). Small farms are highly exposed to market risks, tend to focus on commodities, and have profit margins of just 3-4% (Hoppe, MacDonald, & Korb 2010). As such, small price changes of a single crop can have a substantial impact on a farm's financial status (Page 2011). Variable input costs, such as energy, can play havoc with financing annual operating loans (Page 2011). Therefore, reasonable methods of reducing the uncertainty of operating costs and diversifying the income of small farms are desirable--not just for the farmers themselves, but also for maintaining this sector of our agricultural industry.In our market research, we conducted sit down interviews with more than 45 small farmers such as Andy Westlund. Not surprisingly, their desire to reduce operating costs is the primary factor that motivates farmers to produce their own electricity, usually through solar or wind. Andy uses recycled solar panels and primitive wind turbines to reduce his energy bills. For small farmers, the use of alternative energy simultaneously lowers the operating cost of the farm by reducing the usage of grid electricity and reduces exposure to risk from fluctuating energy prices (Sands & Westcott 2011; USDA 2011). Finally, farmers recognize that generating renewable energy and using fewer fossil fuels reduces dependence on foreign oil, providing greater local and national energy security while reducing the risk of climate change (Sustainable Agriculture Research & Education 2008).However, there are distinct challenges that have kept many small farms from implementing solar and wind energy. The top three barriers that Oregon farmers identified are (based on our own and external research): 1) up-front project costs, 2) permitting, and 3) troublesome paperwork for the incentive programs (Page 2011). Andy Westlund, for example, had to secure county permits for his twenty-foot wind tower, which is sited just a few steps from his thirty-foot-tall house. Additionally, he admits that the electricity produced will never cover the up-front cost of the system.In addition to the general renewable energy challenges Andy has encountered, traditional wind turbines have difficulties specific to farmers that have limited their adoption. The construction of the wind tower can disrupt farming activities and cause soil compaction issues (Linowes 2013). The tower and its blades can also pose an operating and safety problem for agriculture aerial work and can significantly hamper access to cropland, in turn detrimentally affecting agricultural production (National Agricultural Aviation Association 2014). Finally, while the permit and incentive program paperwork problems are important, the up-front costs of a large wind turbine can remove any chance of adoption by small farmers. For example, wind farms often use the Vestas V82-1.65 turbine (a 1.6 MW unit), which has an installed cost of approximately $3.3 million ($2,000 per kW capacity) (NREL 2014). This is well outside the financial range of any small farm. Although wind turbines are available in smaller sizes and prices, their efficiency drops quickly with the shorter tower while maintaining a similar level of product complexity. As a result, the system install cost doubles to $4,000 per kW capacity. Additionally, they actually produce only 10-15% of their stated generating capacity, about half the efficiency of utility scale systems (NREL 2014). Thus, a wind tower system that may be affordable to the average small farmer (e.g., tens of thousands of dollars) does not produce enough electricity to make it financially sensible.eWind Solutions sees these obstacles as both a problem and an opportunity. Our intention is to remove these barriers and create affordable wind energy generation systems tailored to small farms and rural communities. These systems will produce four times the power annually as comparably priced traditional wind turbines and are compliant with current federal regulations. We propose to do this by using a novel method for generating electricity from wind. Instead of a large, vertical wind tower with equally large blades, eWind Solutions uses airborne wind energy technology.The eWind system consists of three main components: a novel flying craft (1) that is tethered by a rope (2) to a power-generating ground station (3). The flying craft will be approximately 8 feet across and weigh about 15 pounds. It will fly between 200-500 feet above the ground and will be tethered to the ground station by use of a nylon or steel rope. At the ground station, the rope will be wrapped around a steel drum/cylinder with an electrical generator attached to the drum axle. Figure 1 shows the basic flying motion of the system and how it generates electricity. The flying craft does figure-8s as it is blown downwind (step 1), pulling out the tether and spinning the drum and electrical generator. When the tether is fully extended (step 2), the airborne craft glides back to the start of its power cycle (step 3), while the ground station simultaneously winds up the tether and the process is repeated (step 4). Additionally, this entire system will be completely autonomous, requiring no attention or effort from the farmer.Although there are other companies pursuing airborne wind energy, most are focused on utility-scale electricity generation that will not be feasible for small farmers. At eWind, we focus on smaller systems that are specifically tailored in cost and capacity to the needs of small farmers. We are also compliant with current Federal Aviation Administration (FAA) regulations, which require tether flags, lighting, and an altitude limit. Other airborne wind energy companies are attempting to receive complicated waivers or rule modifications.

OBJECTIVES: The goal of eWind Solutions is to create a wind energy system for small farmers that is efficient, affordable and easy to use. We accomplish this by using a novel way to collect the stronger, faster, more reliable winds found at higher altitudes that are inaccessible to wind towers that small farmers can currently afford. Because we intend to directly compete with traditional wind turbines, it is instructive to highlight the technical background of wind energy in general and to then discuss how our approach differs from existing wind-power technologies.It is important to remember that the specifications of the flying craft are actually secondary to the overall goal of the entire system. Thus, our overriding goal is to provide 40,000 kWh to the small farmer over the course of a year because that is what actually creates value for our customer. As the research into the tether diameter showed, when a particular attribute is (nominally) beneficially improved, it can actually reduce the power of the overall system. Therefore, we will be listing specific tensions and specifications we currently believe will be sufficient to achieve our overall goal. However, we will modify those specifications if necessary, while maintaining a focus on our power production goals. This Phase II proposal has technical objectives that should take the flying craft development to a state that is commercially viable. This will require the final physical design of the flying craft and near completion of the autonomous flight control system and software. We propose technical objectives for Phase II:Group I:Generate enough tension while the tether is reeled out to generate 40,000 kWh annually (at a good wind resource location).1) A peak force of 3.8 kN on a static tether at 9 m/s wind speed2) A peak force of 2.1 kN on a static tether at 7 m/s wind speed3) Maintain existing maneuverability accomplishments (<20 m turn radius)4) Continue to improve our software analysis capability to include more advanced CFD (computational fluid dynamics) packagesGroup II:Transition the control of the flying craft from mechanical means to fully electronic ground-based signals (fly-by-wire), to computer controlled and then autonomous crosswind flight.1) Stepwise progression from human fly-by-wire control to computer control (using a static tether length) a) Fully human controlled via electronics only (fly-by-wire) b) Computer controlled stable stationary hover c) Computer controlled side-to-side drift motion (slow and with small angle deviations from the vertical) d) Computer controlled side-to-side motion (directed and with turns) e) Automated guidance for figure-8 crosswind turns2) Fully automated crosswind flight: follow power production path put out by computer3) Repeat objectives II:1 and II:2 while actively reeling out tether (at increasing speeds)4) Stretch goals: Time of flight under autonomous control a) 5, 10, 30, 60 minutesGroup III:Determine reliability requirements and incorporate safety aerodynamic characteristics.1) Use reliability growth curve analysis to track progress and use research progress and financial considerations to determine reliability thresholds/goals.2) Introduce aerodynamic, weight and structure characteristics into the flying craft design that when control is lost, the craft enters a safer flat spin and settles to the ground at a reduced speed.The first group of objectives remain similar to Phase I, and as noted before, the work on them is on-going. Now that they have been validated with our mathematical model, they remain acceptable tension goals. Again, if we do modify them, they will continue to support our power production goals, the cornerstone of our commercial viability. We will also continue to upgrade our aerodynamics design software pipeline. Notably, this will include replacing our current XFLR5 package with a more advanced CFD suite. The second group of objectives is based around the transition from human controlled flight to autonomous flight. Based on our research, current progress and discussions with experts, we believe these are good markers for a continuous progression to this goal. It is worth noting that these goals represent a progression of increasingly complex control objectives. Essentially, we need fully autonomous flight and the progression to that goal will be a spectrum of improvement. Initially, these objectives will be met with a static tether length (neither reeling out nor pulling in). Once completed, we will increase the difficulty by allowing the tether to reel out in a manner similar to the power generating cycle. It is expected that the faster the tether reels out, the harder the autonomous control will become due to the increased likelihood and severity of perturbations of the flight path from wind gusts and tether tension oscillations. These tests will gradually increase the tether reel out speed until it exceeds the expected speed necessary to maximize the power generation of the system (approximately 1/3 the wind speed). Finally, we must address the time duration of flight. In many respects, we actually expect this to be both easy and difficult simultaneously. To clarify, to achieve the objectives in Group II we must maintain flight for at least several minutes to demonstrate the success of each milestone repeatedly. If wind and weather conditions are stable during that time, longer flight times are relatively easy. However, the longer the flight lasts, the more likely it is that something will change with the wind and/or weather. It is those transitions or perturbations that will cause the greatest difficulty in extending our autonomous flight time. It is also the hardest to test and plan for because you have to find a stable wind condition, start flying and then have the wind be courteous enough to get mildly unpredictable so that you can test the responses of the flying craft. (It should also be noted that a parallel SBIR Phase I submission would develop the tension control system that would help mitigate these effects during the testing process.) That difficultly will likely lead to an extended time that we will have to work on 'fringe' flight conditions. Thus, we have decided to place flight time duration as a "stretch goal" for this grant. As part of Group III, we must determine how reliable the flying craft must be. To that end, we will employ reliability growth curve analytics. Our prototype testing will provide the necessary reliability/failure data. Additionally, we must determine the failure rate goal. While we obviously do not want the commercial flying craft to ever fail, it is inevitable that it will at some point. Assuming that these failures damage the craft and require a repair visit, we need to balance the economics of that with the time and money in research and development necessary to increase the reliability, at least in the short-to-medium term. This reliability growth curve analytics study will help us manage both the cost of the craft and its field reliability in preparations for commercial use. Thus, one of the more important goals of the Phase II proposal is determining the necessary reliability of the flying craft. Additionally, we will incorporate design elements into the flying craft that will minimize the impact of these failures. For example, we are currently shaping the system to enter a "flat spin" when tether tension/control is lost. This state puts the flying craft horizontal to the ground and allows air drag the maximum amount of time to bleed velocity and kinetic energy before it lands. Currently, this helps us preserve prototypes, but when commercialized it will increase safety and reduce damage during flying craft control failures.

APPROACH: Task #1: Design, analyze, optimize, build and test a flying craft that can match the tension and maneuverability requirements of 40,000 kWh (Group I objectives) (Months 1-24). As previously described, the focus of the entire research and development effort within this SBIR proposal is to create a flying craft capable of creating enough tension in a tether that can be converted into 40,000 kWh of electricity. This task will be carried out by founders P.I. David Schaefer and Dr. Brennan Gantner, with the help of the expected two new employee hires. The research and development process will be similar to the work of Phase I. We are continuing to refine the university collaboration mathematical model (using an Oregon BEST grant, see Commercialization Plan). The lessons and refinements of that knowledge are then folded into new designs built in our aerodynamic software package (currently XFLR5). These designs are imported into our CAD (computer aided drafting, Autodesk) software, split into parts and individual pieces are created via 3D printers, machined by a CNC router and foam hot wire molds. The prototype is then built/assembled. Tests consist of flying the prototype in a relatively steady wind for as long as possible/needed. During that time, our custom equipment is continuously measuring the tension generated on the tether and the Pixhawk/Labview software/electronics is tracking velocity, orientation and location (as well as temperature, air pressure, wind speed/direction, etc.). Currently, we typically conduct these tests on the Oregon coast. Not only does this area have reliable winds, but the loose sand provides reasonable cushioning during control failures and minimizes damage to the prototype. We are investigating the possibility of also using the FAA designated drone testing area at the nearby Warm Spring reservation. While we do not legally need FAA exceptions/permission this area provides, it does allow us to forgo some of the visibility requirements for higher/longer tests on a temporary basis.Task #2: Transition the control of the flying craft from mechanical means to fully electronic ground signals (fly-by-wire), to computer controlled and then autonomous crosswind flight (Group II objectives) (Months 1-24) Founder Sean Mish will lead the effort to automate the flight of the flying craft. After optimizing the CFD software system, Dr. Gantner will transition to contributing to the automation task. As discussed, this will be a spectrum of improvement that will slowly transition control away from direct hand/mechanical links to a flying craft controlled completely by a software/electronic servo system. While this is technically a separate task from the aerodynamic design, Mr. Mish and Dr. Gantner will continually contribute and add requirements to the flying craft design. Because the computer control aspect of the flying craft is mandatory, we have determined that it is most efficient to not only advance the automation concurrently with the aerodynamic design, but to immediately incorporate its needs and lessons into the current prototype. For example, if the computer response time is slow to correct for an unanticipated turn than a human, it may need larger or more aggressive turning control surfaces to compensate. This requirement needs to be known to the aerodynamic design team so that these enhanced control surfaces can be incorporated into the latest design. This task will begin with the attempt to have the computer hold the flying craft stationary on a static length tether. Our initial work suggests that the Pixhawk controller and its corresponding open-source control software is capable of completing these tasks. At its core, it is designed to take a radio-controlled hobby plane and turn it into a computer controlled drone. We essentially want to do something similar, but with a different default orientation (perpendicular to the tether instead of gravity) and different physical responses to the standard commands (it likely won't have airplane standard ailerons, rudder, etc.).Therefore, a large portion of this task will be the modification of this open-source software to our specific needs. To this end, we are initiating a collaboration with Dr. Christopher Lum, who runs the Autonomous Flight Systems Laboratory at the University of Washington. His lab specializes in drone control systems and several of his students have worked on very similar control system modifications of Pixhawk software. Once we had modified the Pixhawk software to our flying craft, we will begin to transfer control to it. As stated, the first task will be to have it hold the flying craft stationary in the sky. Once it can reliably do that, we will have it create side-to-side motion, likely by having it make small orientation changes that creates a slow drift to one side, followed by the opposite motion in the other direction. The key to this progression will be the ability of the system to return to a stationary or 'resting' position as quickly as possible. To succeed at these steps, the Pixhawk will have to demonstrate that it can move the flying craft in the desired direction and stop that motion as needed. These tests will increase in difficulty by increasing the orientation angle from vertical (see Figure 13) that the Pixhawk is allowed to turn the flying craft, thus, increasing the speed of the side-to-side motion. Essentially, true side-to-side or figure-8 flight will be achieved when this angle is increased to (or above) 90 degrees; when it is pointing horizontally.Task #3: Determine reliability requirements and incorporate safety aerodynamic characteristics (Group III) (Months 1-24). Task #3 will be run by P.I. Schaefer, who has decades of experience in these types of product development cycles. Reliability growth curves track the improvement of reliability of the system. One of the key ingredients of properly using them is having a meaningful reliability goal to achieve. In this case, that goal will be a balance of costs based on the value of the flying craft and the cost of replacement (time, travel, materials, etc.) versus the rate of flight time improvement per dollar spent in research and development. This task is a combination of financial considerations balanced with hard data of reliability gathered from prototype testing. To accomplish this, each failure mode will be tracked and rated on severity, likelihood, detectability and consequences. These measures will then be combined (Risk Priority Number (RPN)) to determine the most severe failures so that efforts can be directed to mitigate those cases. This process is a standard approach to product development. While this work will cover the full grant duration, its efforts will ramp up significantly during the second half.

PROGRESS: 2016/09 TO 2018/08
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Continued development of the entire airborne wind energy system through investor funding. Currently in a seed round. Future Software goal - Self-learning flight mode: as we look beyond our current control scheme toward a final product, we anticipate using a mode similar to the 'joystick playback' in order to teach the computer how to fly efficiently in various wind conditions. Teaching the computer will require more data collection during field tests, but at some point, we will be able to develop a model of the TED's flight characteristics which could be used in a Reinforcement Learning Algorithm. This algorithm will allow us to develop a system that is able to improve itself by recording and learning from past power cycles as well as cycles performed by other TED units.

IMPACT: 2016/09 TO 2018/08
What was accomplished under these goals? The highest winds we were able to test in was 6.2m's where we achieved a peak tether tension of 1.65kN. While there are numerous complexities in aerodynamic development, one of the easier extrapolations is the squared increase in lift with increased wind speed. Using the measured data for 6.2 m/s, we can reasonably estimate that the same prototype would generate 2.11kN at 7 m/s and 3.40kN at 9 m/s. Figure 1 contains the force data collected during the highest tension flight and Table 1 shows the extrapolated force values The power we produced = 733N * 2.1 m/sec or 1,540 watts in 6.2 m/sec winds. Using our estimated power generation curved (Figure 2) used in previous USDA proposals, our target power generation in 6.2 m/sec winds is 2,800 watts, while Bergey actual is 1,680 watts and Xzeres actual is 2,180 watts. While the peak power we produced is less than our production ready target, we're reasonably confident with a slight increase in lift area (linear relationship with power produced), operating at higher altitudes (cubic relation with power produced) and a more efficient wing profile to increase the lift/drag ratio (cubic relationship with power produced), will get us there. To date, during all of our testing, we have found that our prototype is regularly exceeding our maneuverability goal of keeping the turn radius <20m. Using the program PhysMo we have analyzed the video of our test flights and calculated the speed and flight path of the TED. Figure 3 depicts TED turning in its path at about 3m radius (slightly larger than the wingspan). By minimizing the turn radius, slightly more power can be produced due to reduced tether movement and resulting tether drag which is the largest component of overall system drag. We are able to create software models of TED and determine rough ratios of lift to drag for differing orientations. Achieved an estimated 3.4kN against a 3.8kN goal or 12% below the target. We believe the difference can be achieved with slight TED aerodynamic improvements over time. Achieved goal Significantly better results than targeted Achieving stable tethered flight was significantly more challenging and took up more analysis and testing time and resources than expected. We roughly estimate 80% of our total project time was spent on this. However, in the end, we are extremely pleased with the results and met this ambitious goal. Each of the following flight modes use these system coordinate definitions as well as others which will be defined in their relevant sections: Joystick: this mode expands upon our previous (Phase I portion of this project) control layout which used a traditional hobby RC controller to fly TED; we are now able to conduct this manual control using the aforementioned software and hardware. We use this mode during launch and as an initial control mode when we are testing a new iteration of the TED. This mode is also useful as an emergency manual control override in the event the TED becomes unstable. Hover: this mode is used to maintain the TED position in the center of the wind window after launch and before transitioning to figure-8 flight path. The hover mode is also utilized during the rewind/retraction cycle of the power generation path as the tether tension is minimal while TED is virtually stationary at the azimuth (highest allowable point of flight path). 3. Side-to-side: because the TED will produce a significant amount of momentum as it flies in the figure-8 power path, it cannot transition directly into or out of the low-tension hover mode; therefore, this mode acts as a controlled transition between the hover mode and the figure-8 path mode. By gradually increasing/decreasing the 'kite heading angle β' (Figure 10) we can control the acceleration of TED between the two modes. Figure-8: this is the path during which all power generation will occur. This mode currently works by the operator inputting the parameters seen in Figure 12 (target positions, horizontal distance, center of curvature, and angle of elevation) into the ground-based GUI software. Then the onboard flight controller autonomously calculates the servo adjustments required to fly toward the corresponding target. The onboard system will fly this pattern until the designated altitude limit is reached, at which point it will transition to 'hover mode' and enter the 'retraction' phase of the power cycle. For the time being, the four target positions remain at the same local coordinate 'yz' position for all power strokes. Further development is required to modify this mode to take advantage of the availability of longer power strokes as the TED extends further from the ground station. Joystick playback: this mode is used to test the flight stability of new iterations of the TED before we use the fully autonomous figure-8 flight control mode. We can manually fly the craft in the desired path and record the servo actuations required to achieve that path. We can then replay the path continuously and make observations of flight stability and reliability. We developed a robust/revised command architecture to make commands sent over RF more compact thus saving on bandwidth which should hopefully also help with response times when many commands are sent to the onboard computer (such as in joystick control). The current command architecture also simplifies the addition of new commands in the future. In summary, compared to our Group II goals: Goals 1a) - 1d) were completed as planned. Automated guidance, 1e) was completed via an open loop control system. We did not complete a closed loop system that actively utilizes GPS data to make flight path corrections. We are however actively collecting GPS data along with TED telemetry data and weather conditions. We are also controlling TED's flight path from the ground. Fully automated crosswind flight was not achieved although as noted above, the critical parameters required to make automated control decisions are being collected. What impacted not achieving these goals were adequate software resources and the level of funding required to keep these resources was much higher than expected. As a startup, we tried to offer stock options in lieu of 100% salary, but failed to entice the software engineers who were able to achieve higher salaries elsewhere. Similar software engineer retention issues, however we are able to actively reel out tether at controlled speeds and measure power generated. Stretch goal - under open loop control (not autonomous closed loop) we were able to achieve over 30-minute flight times. 5. Results and Deviations to Original Work Plan of Group III We did not mature the design far enough to complete the objectives in this group. The tasks in Groups I and II were more challenging and extensive than originally estimated and it is necessary to ensure the work in Groups I and II is complete before any meaningful reliability data can be collected. In summary, compared to our Group III goals: Unfortunately, we are still actively in the "find and fix" mode and not at a stable enough design maturity level to begin reliability growth curve analysis. We are however over stressing the system in various ways, for example: high and low operating temperatures, blowing dust in rural farm environments, salt and blowing sand conditions at our coastline and gusting winds, which is the most challenging to overcome. To date, we have focused solely on aerodynamic control surface optimization due to loss of tether tension to regain control utilizing the smallest diameter tether. Tether drag is by far the largest component of system drag which limits the maximum power our system can produce; so, minimizing tether diameter, maximizes power produced. We have implemented several control surfaces and software changes in this area to minimize the opportunity for loss of control in the first place.

PUBLICATIONS (not previously reported): 2016/09 TO 2018/08
No publications reported this period.

INVESTIGATOR: Schaefer, D. B.

PERFORMING INSTITUTION:
EWINDSOLUTIONS LLC
30678 SW ORCHARD DR
WILSONVILLE, OREGON 97070

NEXT GENERATION WIND ENERGY SYSTEMS FOR CASH-STRAPPED FARMERS AND COMMUNITIES

NON-TECHNICAL SUMMARY: eWind is proposing a highly efficient and low-cost wind-energy system for small and mid-sized farms that will produce approximately four times the electricity per year as comparably priced "conventional" wind turbines. This project addresses the USDA priorities of Energy Efficiency and Alternative and Renewable Energy and Agriculturally-related Manufacturing Technology. We directly support Energy Efficiency and Alternative and Renewable Energy since we will enable farms and rural communities to produce electricity from a clean wind source. Our project will also positively impact the fledgling unmanned aerial vehicle (UAV) industry, a manufacturing field that is increasingly used by farmers and agriculture. We also expect that most of the components of the airborne wind-energy system will be made and assembled in the U.S.--a combination that supports Agriculturally-related Manufacturing Technology. Finally, the project addresses the NIFA Societal Challenge Area 2: Climate Change. Adoption of our technology will reduce the overall carbon footprint of farms in fossil fuel-intensive electricity markets by producing clean wind energy.As Oregon farmer and Organically Grown Company (OGC) executive director Andy Westlund confesses, being one of the 800,000 small commercial farmers in America is challenging. Small farms are highly exposed to market risks, tend to focus on commodities, and have profit margins of just 3-4% (Hoppe, MacDonald, & Korb, 2010, p. 6). As such, small price changes of a single crop can have a substantial impact on their financial status(Page, 2011, p. 11). Thus, variable input costs, such as energy, can play havoc with financing annual operating loans(Page, 2011, p. 11). Therefore, reasonable methods of reducing the uncertainty of operating costs and diversifying the income of small farms are desirable--not just to the farmers themselves, but also for maintaining this sector of our agricultural industry.As Andy Westlund and many other small farmers have discovered, the desire to reduce operating costs is the primary factor that motivates farmers to produce their own electricity, usually through solar or wind (Page, 2011). Andy uses recycled solar panels and "primitive" wind turbines to reduce his energy bills. For small farmers, the use of alternative energy simultaneously lowers the operating cost of the farm by reducing the usage of grid electricity and reduces exposure to risk from fluctuating energy prices (Sands & Westcott, 2011; United States Department of Agriculture, 2011). Finally, farmers recognize that generating renewable energy and using fewer fossil fuels reduces dependence on foreign oil, providing greater local and national energy security while reducing the risk of climate change (Sustainable Agriculture Research & Education, 2008, p. 1).However, there are distinct challenges that have kept many small farms from implementing solar and wind renewable energy. The top three barriers that Oregon farmers identified are: 1) up-front project costs, 2) permitting, and 3) troublesome paperwork for the incentive programs(Page, 2011, p. 31). Andy Westlund, for example, had to secure county permits for his twenty-foot wind tower, which is sited just a few steps from his thirty-foot-tall house. Additionally, he admits that the electricity produced doesn't cover the up-front cost of the system.In addition to the general renewable energy challenges Andy has encountered, traditional wind turbines have difficulties specific to farmers that has limited their adoption. The construction of the wind tower can disrupt farming activities and cause soil compaction issues (Linowes, 2013). The tower and its blades can also pose an operating and safety problem for agriculture aerial work and can significantly hamper their access to cropland, in turn detrimentally affecting agricultural production(National Agricultural Aviation Association, 2014). Finally, while the permit and incentive program paperwork problems are important, the up-front costs of a large wind turbine can remove any chance of adoption by small farmers. For example, wind farms often used the Vestas V82-1.65 turbine (a 1.6 MW unit) which had an installed cost of approximately $3.3 million ($2,000 per kW capacity) (National Renewable Energy Laboratory, 2014). This is well outside the financial range of any small farm. While wind turbines are available in smaller sizes and prices, their efficiency drops quickly with the shorter tower while maintaining a similar level of product complexity. As a result, the system install cost doubles to $4,000 per kW capacity. Additionally, they actually produce only 10-15% of their stated generating capacity, about half the efficiency of utility scale systems (National Renewable Energy Laboratory, 2014). Thus, a wind tower system that may be affordable to the average small farmer--e.g., tens of thousands of dollars--does not produce enough electricity to make it financially sensible.eWind Solutions sees these obstacles as both a problem and an opportunity. Our intention is to remove these barriers and create affordable wind-energy generation systems tailored to small farms and rural communities. These systems will produce four times the power per year as comparably priced traditional wind turbines and are compliant with current federal regulations. We propose to do this by using a novel method for generating electricity from wind. Instead of a large, vertical wind tower with equally large blades, eWind Solutions uses airborne wind-energy technology. The system consists of a novel flying craft that is tethered to a power-generating ground station. Figure 1 shows the basic layout of the system. As the wind blows the flying craft downwind (step 1), the tether spins an electrical generator on the ground. When the tether is fully extended (step 2), the airborne craft glides back to the start of its power cycle (step 3), while the ground station simultaneously winds up the tether and the process is repeated (step 4).

OBJECTIVES: Technical ObjectivesThe primary technical objective to enable implementation of the eWind airborne wind energy system is the design and construction of the flying wing craft. As such, we have broken its research and development into a set of requirements and four Tasks. Task #1: Determine Design Variables Task #2: Design Flying Craft Task #3: Build Flying Craft Prototype Task #4: Test Prototype, Validate Models and Satisfy RequirementsThe requirements, listed in Table 4, come from a mixture of addressing the small farmers' needs, complying with FAA regulations, and our initial research. 1: Determine Design VariablesWhile the requirements form the general backbone of the research effort, they inform numerous aerodynamic design variables with various trade-offs. Thus, the first task of the proposal's technical objective is to determine the aerodynamic design variables that satisfy the requirements. First, the required tether tensions and wind speeds represent two points on the eWind power curve shown in Figure 3 and were chosen such that the nameplate capacity, when combined with the calculated capacity factor, will produce approximately the amount of electricity used each year by a small farm (see Table 3). To achieve these forces, the flying craft must have the appropriate balance of aerodynamic parameters. Most importantly, but not exclusively, in this case is the lift-to-drag ratio, number and arrangement of wings, control surfaces, and wing aspect ratio of the craft and a lightweight design.Second, we have determined that we must utilize at least 75% of the available tether length within the power generation stage of the flight pattern. Since the ground and FAA sets hard limits on our vertical operating range, we must use the tether length that can fit in that space efficiently. This directly affects the maneuverability of the craft. If the craft takes too long to turn, the top and bottom of the figure-8 flight patterns will start to impede into the vertical limits. Figure 5 demonstrates how a larger turn radius of the flying craft would reduce the length of the power-generating portion of our cycle. If the craft turns in a small radius, such as Example #1, it can fit more turns and pull out more tether in the available space. If, however, it has a larger turning radius such as Example #2, it quickly hits both the lower and upper vertical altitude limits before it has time to pull out as much tether. In this case, the flying craft would spend too much time resetting its position and not enough time generating power to meet our necessary capacity factor.While the 75% tether utilization requirement is necessary for the finished eWind system to achieve, we will, however, not be able to measure that value using the Phase I flying craft prototype. Thus, we have determined that a turn radius of 20 m or less will demonstrate that the flying craft will be able meet that requirement when it can be directly measured during a Phase II prototype of the full power-generating system. The advantage of this modified requirement is that we can measure it directly during Phase I testing. Working with Dr. Roberto Albertani of Oregon State University, the result of Task #1 will be a computer model that allows us to determine the combination of aerodynamic variables (e.g. number of wings, wing area, wing length, chord, etc.) that will best meet our requirements.Once we have determined the aerodynamic properties of the flying craft, we will move on to the task of physically designing it. This will include the incorporation of the aerodynamic properties with material selection, structural design, and mechanical control mechanisms. Using a 3-D structural model, we will evaluate the dynamic forces on the craft, as well as a finite element stress analysis. In combination, these will allows us to work out any significant design problems before we progress to the construction of the craft prototype.Once the flying craft is fully designed, our research will transition to the construction of a full-sized prototype. Initial estimations indicate that the prototype will be approximately eight feet across. Using existing tools developed by eWind, we have the space and expertise to create custom wing molds of this size. These, in turn, will create the actual wings while retaining the ability to be easily modified. Since it is reasonable to assume that the design will be tweaked upon actually constructing a prototype, the mold's potential to be easily adjusted is crucial. Once the prototype is fully constructed, we must ensure that it actually conforms to our expectations and requirements. Thus, we will design and implement a series of experiments to test the values detailed by the requirements (i.e. the tether forces and the turning radius detailed in Table 4). Outdoor tests at various wind speeds will measure the force the craft exerts on a tether using a strain gauge. The turning radius of the flying craft will be measured by the placement of GPS sensors in the body and wing tips. These will capture the spatial position of each point on the craft and will allow evaluation of the maneuverability. The final objective of the research effort is to prove the feasibility of designing, developing, and flying the envisioned craft that will enable highly efficient and low-cost power generation within the defined settings. We will produce a final report summarizing our work: the design choices of the craft, the construction and testing of the prototype, and the success of meeting our tension and turning radius requirements.

APPROACH: Usage of general engineering tools and principles, such as design-of-experiments, failure modes and effects analysis, statistical principles, finite element analysis, and computational fluid dynamics.

PROGRESS: 2015/06 TO 2016/02
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

IMPACT: 2015/06 TO 2016/02
What was accomplished under these goals? Impact: The goal of eWind Solutions and this research is to create an airborne wind energy system that will provide cost effective renewable energy to small and mid-sized farms. Not only will the cost of the electricity produced be comparable to the price of the local utility grid (depending on wind quality, local utility prices, etc.), but the system will have several advantages over existing solutions (traditional wind towers, solar, other airborne wind energy companies). eWind is scaling the system to produce approximately the amount of electricity used each year by a small farm. When combined with a local utility net-metering arrangement, this can alleviate most of the farm's annual electric bill. The system is four times more efficient than existing traditional wind turbines of comparable cost. In addition, our system requires no heavy construction equipment or large concrete pad, negating the soil compaction issues that have soured some farmers to wind energy. Land space use is minimal land space, allowing more room for cultivation, a clear advantage over wind towers and solar panels. Finally, we are following existing FAA regulations. Therefore, we do not need special permission or waivers that other airborne wind energy companies are seeking in order to fly in the United States. When completed, the eWind airborne wind energy system will provide most of the electricity for a small farm for a fraction of the cost of a modern tractor (about $50,000). This will replace carbon intensive power generation and increase the financial resilience of our farming sector. This will also bring jobs to rural communities through installation and maintenance work. The goal of this grant was the development of the flying kite that will power the electrical generator. The entire system is complex, but the flying kite is one of the most technically challenging aspects of the development. It must be rugged, fast and highly maneuverable while producing enough tension on the attaching tether to turn the electrical generator. This grant focused on beginning that development by meeting the initial physical requirements of the kite, namely turning radius and pull strength. Results: eWind accomplished each goal laid out in the proposal objectives and goals. The primary means of measurement on our progress was the three physically measurable properties of the latest version of the kite. Specifically we wished to have a turning radius of less than 20m, a pull strength of 2.1kN at 7 m/s of wind and a pull strength of 3.8kN at 9 m/s of wind. These measured objectives required the completion of numerous other tasks that were harder to quantify, but no less important to the success of the project. Specifically, in collaboration with Oregon State University, we developed a computer model that predicts the performance of a given kite design (with numerous other variables: flight path, tether properties, generator efficiency, etc.). We combined this with other Computer Aided Drafting (CAD) and aerodynamic modeling software to create a pipeline from initial idea to design to build to test. In addition, we streamlined the manufacturing of prototypes using the CAD software and 3D printers, allowing us to go from improvement idea to built prototype in just a few days. While there were minor changes to our work plan which could be expected of any technology development effort, we followed the proposed steps closely. They showed we had a realistic and appropriateplan before beginning this project. While the building ofthis software and construction pipeline took a large portion of the grant period, we were still able to meet our quantifiable goals. There were three criteria we measured (as mentioned above): 1) Turning radius of less than 20m: This was accomplished during one of our earlier prototypes and has been the expectation and standard for all following kites. It was successfully achieved and measured during our latest test, where we had a consistent turning radius of approximately 10 m. 2 and 3) A pull strength of 2.1kN at 7 m/s of wind and a pull strength of 3.8kN at 9 m/s of wind: These two goals were not technically measured, but we are considering them accomplished. The final tests were performed in approximately 6.2 m/s winds. Since we are currently unable to force nature to provide the exact winds we desire on command, our best option is to use basic aerodynamic scaling equations to determine what our forces would be at faster wind speeds. In this case we measured 1.65 kN at 6.2 m/s wind. Because the force scales at the square of the wind speed, this equates to an expected force of 2.11 kN at 7 m/s and 3.40 kN at 9 m/s. While these estimations are based on rough, simple calculations, they have proven to be accurate to approximately 10%. Therefore, even though the higher wind speed estimate is slightly below the grant goal, it is close enough that it is likely we will meet it with the current prototype or, failing that, with the next iteration that will continue our tension improvements. We anticipate being able to directly measure the force at these faster wind speeds the next time the weather provides them to us. It should also be noted that all these measurements are collected by a custom built electronics system. Elements of this system on the kite are: location, speed and orientation. Ground elements record the tension on the tether and wind speed. A nearby laptop computer collects both the ground and kite signals and stores everything at a 5 Hz rate on a nearby laptop. The electronics also have the capability to send signals from the laptop back up to the kite. While the kite is currently human controlled, this capability is the first step in transferring control to the computer and beginning the work of creating an autonomous flying system. Finally, because most of our demonstrative progress is best shown in pictures and plots, we have created a final report outside of this web form. This report will combine pictures of our prototypes and data collected from their testing. In addition, we will include the software results created for us by Oregon State University that describes their efforts and conclusions.

PUBLICATIONS (not previously reported): 2015/06 TO 2016/02
No publications reported this period.