Solar Power-Optimized Cart Initial Project and Group Identification Document Due: September 17, 2013 Group #28 Group Members: Jacob Bitterman Cameron Boozarjomehri William Ellett
Potential Sponsors: Duke Energy Omni Leasing, Inc. Design Narrative In deciding the group project for Senior Design, our team wanted to integrate transportation and energy efficient functionality. A design with these components would undoubtedly give us experience that would be vital in our futures as engineers. We were specifically interested in solar cell technology, so we sought to include this aspect in our design. Our motivation came from small lightweight transportation design; bicycles and carts. Lightweight transportation inherently requires less power to drive its locomotion. Since we realize that the issue with modern solar cell tech involves its energy output, we decided to look for a smaller application than the standard American sedan. As college students, we are quite familiar with the versatile simplicity and lower cost of bicycles, but we struggled with attempting to formulate an integration of bicycles with solar panel capabilities. Solar panels need surface area, and the bicycle is specifically convenient because of its limited surface area. So to integrate our interests, we decided to focus on the historically stable electric platform of the golf cart to implement our design. We recognized the benefits of the cart focused project outweighed its issues. Electric carts are relatively simple in design, and they re standard roof design is naturally conducive to our solar array design. Building our design project to work with an electric cart allows us to focus on our electrical and computer design components
without getting bogged down in too much mechanical engineering. We are seeking to retro-fit an electric cart with a solar array on its roof to enable the cart to recharge its batteries throughout the day, via the photovoltaic cells. Our design would provide short-range transportation with limited energy cost to the user. Goals and Objectives 1. Energy Efficiency: - Our design focuses on the power interface to optimize the energy of the photovoltaic cells and the stored power in the cart batteries. We want the batteries to be charging whenever there is solar power to be harnessed. We desire to maximize the energy delivered to the wheels from the energy drawn from the solar array. 2. Increased Range: - Specifically, the range optimization of the cart is the characteristic of our project that is easiest to judge it by. We are looking for a substantial increase in the range of the electric cart. Using the solar cells and power optimization, the electric cart should then be able to travel much further than previously. 3. Speed: - While the range of the cart is our main focus, its speed cannot be ignored. We are seeking to maximize the cart s speed, while improving its efficiency. We are hoping to maintain the industry speed standard of electric cart between 15-25 miles per hour.
4. Maximized Capacity: - The more the cart can handle the better. We looking to maximize the carrying capacity of solar powered cart. Standard carts usually carry between 2 & 4 passengers. We are hoping to meet a similar standard. 5. Compact Size - One of the largest draw of an electric cart is its size, so we d hope to add very little to the dimensions of the standard cart. When it comes to electric transportation, compact is best. 6. Minimal Charge Time - Quicker charging times allow the cart to keep functioning optimally. A minimal charge time will naturally extend the range and function of our cart. 7. Intuitive User Interface - The cart user should be able to control the distribution of power in a simple manner to use the cart optimally for his own specific situation. 8. GPS Capability - The GPS functionality of the cart will allow the interface to accurately calculate range of the cart due to energy consumption. The user will also have the ability to track his vehicle, if he so happens to lose it 9. Safe and Dependable Design - The cart must be able to be operated safely at all times. The power interface systems will be designed to prevent dangerous power use of the batteries. As always, the electrical components must include safeguard to prevent damaging electrical fires. 10. Minimal Cost - We will be working on a tight college budget with limited outside
sponsorship. Our team will attempt to implement our design while minimizing the cost. In a real world scenario, a cheaper product to produce and design is usually a better product to market to your customers. Specifications and Requirements Characteristic Required Minimum Maximum Desired Range 30 miles 100 miles Speed 10 miles per hour 20 miles per hour Capacity 2 people 4 people Charge Time 4 hours 6 hours Cost $2000.00 $3500.00 Vehicle Length 80 120 Vehicle Width 48 60 Vehicle Height 66 78 Vehicle Weight 800 lbs 1000 lbs
Limitations Characteristic Range Speed Capacity Cost Size & Weight Limitations Our range is limited by the energy output of the photovoltaic cells and the energy intake of the electric motors. Weather is a specific limiter of our efficiency. To maximize our range, the cart s speed will be limited by factors determined by the user. Faster speeds will limit battery life. Safety also limits the maximum allowed speed. The solar array will only be able to keep up with a limited draw on the battery reserves. Our maximum carrying capacity will be determined by the power supplied by the batteries and solar cells. With limited sponsorship and personal assets, we will seek to design our project with responsible financial expectations and limitations. We are limited by the standard size and weight dimensions of electric carts. Our additional design modifications will add little additional weight to the design. Budget and Financing As stated in the specifications above, this project is projected to cost between $2,000 to $3,500. The median budget will be broken down as follows: Item Cost Funding Source Golf Cart $1,500 Sponsor Photovoltaic cell $300 Sponsor PV: Network + Wiring $50 Team PV: Framework $50 Team Microcontroller $50 Team Battery pack (Li-Ion) $75 Sponsor UI: Screen $150 Sponsor UI: Physical interface $30 Team
We are hoping to be able to receive funding from Duke Energy to assist with the purchase of the more expensive items. Depending on how much or little funding we receive, we will have to provide a varying degree of our own funding to the project. Additionally, the quality of the specific items marked sponsor in the above table will be determined by our level of outside funding. Higher funding will allow us to invest in higher-quality photovoltaics and better batteries. These increases will help us to achieve our maximum goals of better range and performance. Milestones Semester 1 Within the first semester of Senior Design, we have several design milestones in mind: 1. Acquisition of a golf cart Arguably the most important step, this milestone must be reached as soon as possible to have a physical system on which to base our design. 2. Purchase and testing of photovoltaic cell This milestone will allow us to begin development of the algorithms that will later control the internal electrical operations of the combined solar and battery power system. 3. Baseline testing of charge/discharge rates of battery The underlying programming of the user interface will depend on this phase of testing. We will be able to use this information to develop range estimations and charge time predictions.
Semester 2 During Senior Design II, we have a few specific major production milestones: 1. Production of functional golf cart with range of 30 miles (20 min, 100 max) This range will be heavily dependent on funding, as that will affect the quality of the batteries and other components that we are able to acquire. 2. Integration of functional user interface The user interface that we develop will be the most visible aspect of our work in this project. Because of this, it is very important that we spend time making sure that the relevant information is relayed in an effective and easily understood method. 3. Selection of multiple modes of operation Users will be able to select a specific mode in order to tune the energy distribution of the system to their specific desires. This will allow for a certain degree of customization on a per-user basis by providing both high-efficiency and high-performance options. 4. Photovoltaic charging At the conclusion of the project, it is expected that the photovoltaic charging system will be able to fully charge the batteries of the vehicle in less than 6 hours.
3.4 Possible Architectures and Related Diagrams Key (Team) - All members are responsible for this block Research - Research is being done to determine best approach Design - This block is being designed by group members To be Acquired - The desired product has been determined and is in the process of being purchased or donated Legend for Solar Beamer block diagram Golf cart (Platform) - This is the intended base on which all project components are to be mounted. Solar Array - This is the method in which we intend to collect energy for the vehicle by use of Photovoltaic Cells mounted on top of a Mounting Platform which we intend to make adjustable for optimal energy collection. Electrical Interface - This block represents how we intend to monitor the energy collection, dispersion, and regulation throughout the vehicle. Please reference the Block Diagram below for further details. User Interface - This Block represents the method in which we intend to display system data to the end user as well as how they will manipulate the energy distribution in the system. Please reference the Block Diagram below for further details.
Legend for Electrical Interface block diagram Microcontroller - The Microcontroller is to be the embedded system with which the vehicle will collect data and control energy dissipation. Input/Output - This block represents the manner in which we intend to link the onboard computer to the electrical components of the vehicle via cables and sensors. Power Use Regulation - This pertains to what sensors and components will physically monitor the vehicles performance as well as regulate the energy dispersed by the power systems. Batteries - The electrical components we intend to use to store the electrical energy for our vehicle (We are still researching this block) Lithium-Ion Polymer - Thus far our research has yielded that the best approach is to use Lithium-Ion Polymer batteries because of their quality, reliability, and absorption/dissipation rates. However, we are still conducting more research.
Legend for User Interface block diagram Output/Display Hardware - Here we have determined that we would like to use some sort of screen to display our information such as a tablet. Content Displayed - Referring to the block above we are designing our User Interface for displaying vehicle statistics such as speed, remaining energy, range, current operational mode, and rate of charge including loss of battery efficiency from charging. Input/Display Hardware - Here we are determining what aspects of the vehicle should be manipulable by the user such as autopilot or different mode selections. This block has an arrow going to Content Displayed because if we can use some sort of tablet then we will be able to display values that can also be changed by the user to give a more thorough control for the vehicle interface. Mode Selection - We have decided that for the sake of the user we will include simple user modes that will automatically handle vehicle control including: Performance mode: Allows for top vehicle speeds while deregulating energy distribution. Eco Mode: The vehicle will be tuned for maximum range which may sacrifice speed. Balanced Mode: Tuning vehicle systems to the desired balance between range and performance which will likely limit top speed less than eco but not provide the same quality of range.