I. Introduction

Bergey Windpower Company (BWC) of Norman, Oklahoma has been developing small to middle sized wind turbines since the mid 1980’s, and recently wind power has begun to break new ground in Japan moving the focus of the business to this area of the world. After the Fukushima Daiichi nuclear disaster caused by the tsunami triggered by the Tohku earthquake on March 11, 2011, Japan has been looking for alternative energy sources. This has opened a huge market for the wind power industry. This transition in the energy market has brought new international companies to Bergey Windpower in the interest of buying large numbers of small to middle sized wind turbines used on farms, homes, and for commercial businesses. Japan’s energy companies are using these turbines to offer a 1 to 1 return per kilowatt hour for alternative energy. This means that energy will be sold by the company at $0.50 per kilowatt hour to their customers, and Japan is willing to pay that in full to put energy back into the grid. To put this in perspective, Oklahoma Gas and Electric charges an average rate of $0.14 per kilowatt hour to the average customer, but only pays the alternative energy customer $0.02 per kilowatt hour to but energy back on the grid. That is a 7 to 1 return. Japan currently has 15 Excel 10kw wind turbines for testing.

Figure 1: Structure and Components of the Excel 10kw Turbine

1

Figure 2: Excel 10kw Terminal Fire DamagThe Excel 10kw unit is a reliable, middle-sized wind turbine that comes with a 10 year warranty for $36,000. One of the concerns with this unit that have been brought to the service manager Keith Marcom’s attention is that there have been reports of sudden electrical fires in the terminal area (Figure 2). The terminal box is mounted underneath the wind turbine and is where the turbine is electrically connected or disconnected by the user (Figure 1). The customer report focused on in the meeting with Mr. Marcom was the fire in Mr. Doerr’s Excel 10kw unit. Mr. Doerr lives on an Island off the coast of North West Scotland. The terminal enclosure protects against debris, but not against moisture penetration. This fault leads to electrical failures and possibly fires. The current and failing design is shown in Figure 3.

Figure 3: Current design of the terminal box on the Excel 10kw

The Japanese coast line presents the same extreme marine environment that the coast of Scotland does which is an environment not normally experienced by the Excel 10kw. Because of this, failures due to moisture have started to occur within three months of installation. It has also been reported that repeat fires on 10+ units in marine climates have needed further repairs three months after initial repairs on the terminal housing box were completed. The effect of a coastal environment on the turbines is clearly expressed with Figure 4 where the locations of the failures are indicated. The high air humidity in these areas have caused water to penetrate the housing boxes and cause the electronics inside to short out and sometime catch fire.

2

Figure 4: Map of failure locations illustrating the effect of coastal environments on turbine lifeMore terminal fires and other similar failures are being reported by Japan and other coastal owners of the Excel 10kw. The maintenance and prevention of failures such as these are crucial for the success of these projects, therefore a field of research has been developed focusing on how to predict failures as well as how to estimate the cost of the downtime that follows after a catastrophic failure and how the lack of power generation during these times effects the efficiency of the unit. In order for turbines to be a feasible form of alternative energy, maintenance costs and downtime must be minimal in order to maximize the amount of energy generated from the wind [1] [2] [3]. Table 1 shows the cost and downtime for the damages occurring in the Excel 10kw.

Table 1: Downtime costs due to moisture damageType of Fire Cost Downtime (U.S) Downtime (Europe)

Terminal (Contained) $5000 1 Week 1 MonthMainframe Damage (Uncontained) $12000-$15000 3 Weeks 3 Months

The solution is to design and test a sealed terminal box that can be retrofitted onto existing Excel 10kw units. The design we have chosen doesn’t allow moisture to penetrate the terminal box and has the added bonus of being easily retrofitted onto already purchased turbines with no additional modifications. This makes the new design is a quick, simple fix to a potentially hazardous problem. This project will increase Bergey Windpower’s reputation of quality and since the terminals will no longer short out and cause fires, potentially dangerous situations are prevented. By designing a part that fits onto units already in the field, instead of designing a solution that can only be applied to units manufactured after this modification, the problem can be resolved quicker and cheaper.

The sealed terminal housing box will be designed and modeled in Solidworks and tested in ANSYS for moisture penetration. Insuring that the terminal box prevents large amounts of moisture is the key to preventing failure. If the sealed terminal box can prevent these fires in

3

extreme marine climates, Bergey Windpower may be able to confidently move into the larger, more profitable coastal markets in Scotland, Japan, and Australia. On the other hand, if failures continue to occur it could mean losing millions of dollars in potential revenue and warranty coverage.

In order to develop this crucial solution, funding needs to be acquired in order to enable research, design, testing, and manufacturing of this product. The major costs of this project come from the designers, machinists, and materials, therefore this project cannot proceed without funding. Based on field evidence (Figure 2) and research done on the turbine market, this project is determined to have great value to Bergey Windpower and its profits and future customer relations.

II. Proposed Program

i. Research

A primary source of information about the problem came from an interview with BWC’s service manager Keith Marcom. He discussed customer complaints and reported failures due to moisture penetration of terminal boxes. There have been more than 20 reported cases of this same type of failure from places such as Scotland and Japan. All cases were located in coastal Island areas with heavy winds and large amounts of salt water. The interview also covered cost of the units, energy production cost, downtime cost, and BWC’s warranty responsibilities.

The cost of an Excel 10kw turbine alone is approximately $36,000, but most clients buy a tower, inverter, and a 10-year warranty for close to $70,000. This terminal fire malfunction is covered under BWC’s warranty, which means the company is responsible to the client to provide a solution to this problem. If the terminal area is the only area damaged by fire, the cost to BWC, including parts, shipping, and labor, is approximately $5000. The cost to the client is the loss of energy production during the downtime. These figures are listed in Table 1 in the previous section, however the cost of downtime varies with location and dependence on the system. The downtime of a turbine greatly effects the owners, especially if the owner is off grid, meaning that their primary source of power is from the turbine. Also, due to the time it takes to ship, the downtime costs for Europe and Japan are expected to be greater than those in the United States.

An initial design, further discussed in following sections, was quoted to cost approximately $62.50 per unit. Compared to the $36,000 cost of a completely new turbine, a replacement terminal box that can be retrofitted into the old design is the best solution. It reduces the cost to

4

BWC because entire turbines do not have to be replaced and it also reduces the downtime for the customer because the boxes are easier to ship and install. It is also determined that the replacement terminal boxes should be designed to be easily manufactured so that downtimes, as well as the cost to Bergey, can be reduced further.

ii. Parameters

The main parameter that the replacement terminal box must adhere to is that is must be water tight, but another vital parameter for the terminal box is the size. It must be able to be retrofitted into the existing terminal box space on the turbines which is 5.65 by 4.531 inches. An additional consideration is that the boxes need to be designed in such a way that there is innate vibration control. An initial design developed to meet all of these parameters is shown in Figure 5.

Figure 5: Solidworks Model of the Terminal Box Assembly Initial Design

This initial concept for the box is that it will be sealed with a metal to metal seal around the outer edges as well as a foam gasket that will surround the metal. Rubber grommets will also go around the hole where the electrical cords enter the box in order to prevent moisture penetration. As shown in Figure 5, the initial design also dimensionally fits in the terminal box space on the turbine. This design will cut costs, as well as ensure the ease of replacement in the field. The initial design at this size has been quoted at $1500 dollars per 24 boxes, or $62.50 per box, by an out-of-house manufacturer, Multi-Metal. This solution has been over-designed with respect to vibration so that prevention can be assured without rigorous testing. The location of the terminal boxes should also ensure that the vibrations of the system stay within a nominal range.

Secondary parameters define for this project are the criteria for success during testing. For moisture penetration, the criteria for success is 5% moisture penetration after 5 years of exposure. This means that the terminal box is 95% water tight. This percentage is selected because water penetration at this level is determined to be unlikely to cause damage to the equipment inside the box. The criteria for success in the case of vibration is measured with time.

5

Using software to test the design, if the vibration does not cause failure after 5 years with a factor of safety of 2, then the design is considered successful.

iii. Procedure

The procedure for this design is rather straightforward. First, the design must meet the parameters set by the previous section, and an initial design meeting these criteria has already been developed. Creating the initial design required researching causes of failure through interviews and pictures as discussed in previous sections. After the interview, a moisture resistant enclosure was a clear solution to these failures. Research for the enclosure design began with considering standard designs created by companies who manufacture these types of enclosures. From this the team was able to gather how to shape the access point of the box creating a metal to metal seal with the cover. Multi-Metal, the company contracted to manufacture the finished design, also offered a foam seal on the cover that creates a double layer of moisture protection.

To insure a retrofitted design, the current design’s attachment points, wire routing, and support gusset placements had to be considered. The first objective of the design was to create a box that fit within the tower adapters gussets, still fitting the terminal inside, and allowing for required wire routing. There was enough space to create a proper box that fit these parameters. The design was then modified so that the terminal box could attaching at the same point the welded connection tabs were connected to the box. There is a notch between the connection points that allows the wire to pass freely over the top of the box and into the grommet and wire port. The two tabs used for connection at the bottom of the box are slotted to allow for manufacturing imperfections. Knowing that in the future the team would have to account for vibration damping, a ¼ inch space was left between the terminal box surfaces and the tower adapter surfaces in case changes need to be made in order to meet the vibrational criteria for success.

Using pressed-in M4 PEM nuts on the back and inside of the access opening will allow for easy attachment/un-attachment of components. The box is attached to the tower adapter with M4 bolts as well. This means the terminal box only requires an Allen wrench and a screw driver for maintenance/inspections. These specifications can be seen in Figures 6 and 7. These figures include technical drawings that were sent out for quotation as a way to validate the economic feasibility of the solution as well as to provide an accurate quote for the replacement parts in the budget description.

6

Figure 6: Technical drawings of the initial replacement terminal box quote

Figure 7: Technical drawings of the initial replacement terminal box accessories

The second step of the procedure is the analysis and testing of the design with respect to the predetermined criteria for success. The testing will be done virtually using the Finite Element Analysis (FEA) software ANSYS. ANSYS is a powerful engineering tool that uses the Finite Element Method (FEM) to compute solutions of complex systems. FEM is a numerical technique

7

that applies a mesh to a part in order to break down the complex geometry into simplified elements that are easy to individually analyze. The software then puts all these elements back together to give an approximated solution for the larger part based on the defined boundary conditions. The software uses a numerical technique to solve for changes from node to node and can therefore determine solutions for the larger system. There are multiple ways to check the accuracy of a solution developed in ANSYS. One way is to run multiple simulations where the number of nodes is incrementally increased. If the solution to each of these events converge to the same answer, generally within an error margin of 0.001, then the solution is considered verified. Another way is to compare aspects of the solution to tabulated values. This technique does not apply to this project because of the lack of tabulated data, therefore the first option, using multiple runs and a converging answer, is chosen to be the technique used to verify the ANSYS solution.

After testing, the design will be reworked until a satisfactory level of moisture penetration has been achieved. This means that information gathered by testing will be used to make alteration to the design and then the design will be re-tested in the same manner as before. This procedure will be repeated until both the moisture penetration and vibration success criterion have been reached.

iv. Deliverables

Once funded, the team will provide a 3-D design done in SolidWorks and since the new design will be able to be retrofitted to existing turbine the 3-D model will also be integrated into the BWC’s Excel 10kw SolidWorks assembly. Parts and assembly will include the terminal box itself, the terminal box cover, grommets/plugs, and hardware an example of this is shown in the following figure. A technical write up and the results of the ANSYS analysis will also be presented to BWC. The terminal box will then be drafted for manufacturing and a quote will be determined from the technical drawings created, similar to Figures 6 and 7. The quote will be from Multi-Metal in Rockwall, TX who already produces enclosures for BWC. Once a quote is received from Multi-Metal a cost analysis will be conducted to see if the design can be improved based on the company’s manufacturing process. The 3-D model, moisture penetration and vibration test results, technical drawings for replicated manufacturing, and cost analysis will be delivered upon completion of this project.

III. Qualifications

The solution to this problem is a mechanical design that is sealed against moisture penetration, therefore experience with three-dimensional computer aided design (CAD) is crucial for the completion of this project. In this group there is extensive experience with SolidWorks, which is the software used to develop the model. Robert Smith and Emily Smith have used SolidWorks

8

extensively in design work for companies such as Bergey Windpower, Schlumberger Limited, and TATA Automotive (examples of past work can be found in Appendix II). Moisture and vibration analysis are also required skills for this project, and Emily and Mark have these skills, respectively.

Mark Smith is currently a student at the University of Oklahoma pursuing a degree in Mechanical Engineering. He is currently working with Dr. Peter Attar on vibration analysis mechanics for moving and rigid bodies. He is also currently working with Solidworks and ANSYS in his classroom projects.

Robert Smith has been employed by BWC as a design engineer for the past year, and his experience with the company includes the tower design and structural analysis of BWC’s “Mobile Energy Container” which was bought and placed in remote parts of Northern Canada by the Canadian government for weather research. His most recent project includes the preliminary design and structural analysis of BWC’’s new prototype the “NREL Stall Blade Turbine”. He will be in charge of the design/redesign and structural analysis of the terminal box solution. Having a team member working with BWC will allow the team to streamline communications as we work toward a final product.

Emily Smith is currently a student at the University of Oklahoma pursuing a Bachelor’s in Mechanical Engineering and working toward her Master’s in the same field. She is currently working with the director the Aerospace and Mechanical Engineering Department, Dr. Cengiz Altan on the mechanical design (developed in Solidworks) of a Vacuum Assisted Resin Transfer Molding (VARTM) setup where localized pressure can be applied in order to improve the properties of the composite material being formed. She has also completed research for the Systems Realization Laboratory where she developed a FEA model of TATA Automotive’s hot forging process so that inputs can be changed based on the location of a factory. This allows companies to streamline their resources based on labor energy, and material costs in the area. ANSYS has also been used by Emily on previous projects to study the effect of heat on the materials used in hot forging, analyze the failure of the Kansas Hyatt Regency Walkway, and to determine the life of a gear tooth under cyclic loading (Appendix II). Because of all of her experience with Solidworks, ANSYS, and mechanical design and analysis, Emily is confident in her ability to develop the best possible solution for Bergey Windpower.

The solution to the terminal failure problem also requires knowledge of moisture penetration and sealing. Seals are complex components that require a lot of research and experience in order to incorporate successfully. Emily has recently completed a project for Schlumberger Limited where she was tasked with designing a seal evaluation system in Solidworks. In this project she had to develop the 3D CAD model as well as the technical drawings. By working with Schlumberger she also learned the limitations of manufacturing and machining and how to develop designs that will reduce cost for the company. She also gained the necessary experience

9

to incorporate seals into a design because of the wide variety of seals that were incorporated into the seal evaluation system. The team has extensive knowledge and experience in mechanical design and analysis, therefore there is a significant amount of confidence in the team’s ability to find a solution quickly and proficiently.

IV. Budget

Engineering drawings of the terminal box initial concept were sent to Multi-Metal in Rockwall, Texas, because of BWC’s existing account and Multi-Metal’s history of good work. This quote was requested in order to economically validate the project. This initial quote shows that the design will be economically feasible because the quote was $1,500 for 24 units, which is a cost of $62.50 per unit. This quote is well within reason, and indicates that testing, analysis, and re-design should be proceeded with.

Table 2: Schedule and budget for the R&D of the replacement terminal box

The cost of manufacturing, per part, is determined to approximately $62.50, and the cost of research and development is outlined in Table 2. The greatest cost in this project is labor, therefore the time spent on each step of the project is crucial for defining the budget. Each engineer will be working at a rate of $30 per hour rate. Initial conceptual design and research for the terminal box solution took 2 weeks, and testing and re-design is projected to take to 3 weeks. Since BWC contributes to overhead and reduces the cost of lab and office space, the indirect costs are minimized. The only other cost associated with this project is the cost of software. Since both Solidworks and ANSYS are heavily used in developing this solution, licenses for this software must be acquired. Based on current costs for professional licenses, the cost of this software during the 5 weeks of work is predicted to be $2,200. BWC initial needs to manufacture 24 units in order to immediately solve this problem, so the total manufacturing cost is expected to be $1,500. This means that the total cost of this project will equal $13,800.

10

The results of this research and development has the potential to make BWC a leader in the multi-million-dollar small to middle sized wind energy market on the rise in Japan. The new terminal box will also guarantee hundreds of thousands of dollars saved in warranty repairs. BWC’s existing warranty cost for a terminal box failure on a Excel 10 may  range anywhere from $5000 to $15000. Our team is proposing a solution that will cost less than $70 per repair, and will prevent any future failures. In return growing an outstanding reputation with existing customers at a fraction of the cost.

V. References[1] Z. Hameed, Y. S. Hong, Y. M. Cho, S. H. Ahn, and C. K. Song, “Condition Monitoring And Fault

Detection Of Wind Turbines And Related Algorithms: A Review,” Renew. Sustain. Energy Rev., no. 13, pp. 1–39, 2009.

[2] J. Ribrant, “Reliability performance and maintenance -A survey of failures in wind power systems,” Electrical Engineering, 2005.

[3] P. Caselitz and J. Giebhardt, “Advanced maintenance and repair for offshore wind farms using fault prediction techniques,” Security, vol. 49, no. 0, pp. 1–4, 2002.

Appendix

Image 1: BWC’s Mobile Energy Container

11

Image 2:`BWC’s NREL Stall Regulated Turbine

12