Background
At Envo we are committee to evolving electric mobility for everyone. Our passion lies in sustainably engineered e-mobility solutions and when we talk about e-mobility solutions, we are not just talking about traditional products but also highly specialized niche products. Hydrofoil WaterBike is one such venture where we are working on an ultra- portable e-mobility for water lovers. This waterbike is your partner in exploring local shoreline, low impact fitness training or getting around to hard-to-reach fishing spots.
Problem/Opportunity Statement
Watercrafts require large amount of power to move, especially at the higher speeds due to exponential relation between speed and required power to reach that speed. Watercrafts operate on three different principles, the most tradition is displacement type where buoyance force is responsible for keeping craft floating, second type is planning where hydrodynamic force supports the watercraft and is suited for high-speed purposes. The third type is hydrofoiling, in this a hydrofoil supports the weight of craft and lifts it out of the water, decreasing water resistance, this method is by far the most efficient method.
Electric batteries do not offer same level of energy density as a hydrocarbon-based sources of energy, consequently for the same level of performance an electric system must be more efficient than traditional hydrocarbon fueled systems. We here at ENVO believe hydrofoils are the answers to a more efficient electric water mobility system.
In the past, we developed modular conversion-kit based hydrofoils for kayaks and surfboards but due to instability of these watercrafts when lifted out of water the increase in efficiency did not translate into a performance improvement. This led us to believe that a complete platform needs to be designed with integrated hydrofoils.
ENVO is developing pedal assist electric powered catamaran styled pontoon-based hydrofoil supported watercraft (water bike). The hydrofoils in this water bike would carry part of the weight and partially lift it out of the water.
Previous Efforts
Copyrights: Justin Ayinbila Amoah
Goal
The goal here at ENVO is to design and manufacture an electric assist human powered water bike with the following features.
- Efficient and light enough to be powered by human power only, the electric power
- to be introduced to supplement human power.
- Compact and disassemble-able so that it is easy to store and easy to transport.
- Stable design so user of any age can ride it.
- Waterbike can be used by user without getting wet.
- Fast and maneuverable to provide fun riding experience.
- Operation must have zero environmental footprint.
ENVO waterbike uses catamaran design with inflatable material constituting the pontoons. The body will be made of aluminum tubes due to aluminum’s low weight and resistance to corrosion. The hydrofoil (lifting surface) is made of carbon fiber and will be attached to the body of the waterbike.
Waterbike must use as many parts from electric bicycles as possible, this includes hub motors, drivetrain, handlebars, pedal assist sensors etc. so that the product is not only low cost but also easy to service/repair for it to be sustainable.
Key Requirements
- Pedal Assist design, with electric system supplementing yet not replacing human power.
- Total weight less than 50kg.
- Transportable using a SUV/minivan.
- Maximum Power limited to 1500W
- 1 hour of range on each charge.
- Maximum Load capacity 120kg.
- Up to 20km/h speed.
- Upright or recumbent riding position.
Key Features
Low maintenance: We know traditional gasoline engines consume a lot of power and require regular maintenance. Even small watercraft have huge issues with the engine where they get damage in the middle of the ocean. hybrid: human power + electric powered system will be more reliable than a gasoline engine. so if you are stuck in the ocean with low battery, you can always use human power and get back to the shore without any hassle.
Environment friendly: Envo adapts to hydrofoil based electric propulsion system which not only omit water pollution but give a noise free and smooth ride experience. This maintains the peace in the surroundings and dont generate bow wave.
Batteries: Envo will be conducting dedicated research on the batteries. We want batteries to be transportable and safe, which means a compact battery which provides a good range and a safe battery which doesn't explode when immersed in the salty water. A compact battery will be easy to carry for charging purposes. For us, safety is upmost priority.
Risk: When we talk about hydrofoils those are well aligned aerofoils which are attached under the hull of the watercraft, the only risk involved is accidentally damaging the hydrofoils when the big stone comes in the way or low water level. This completely depends on the riding characteristics.
Known Constraints/Risks/Assumptions/Uncertainties
ENVO Waterbike is designed to be stable so that user of any age can use it. This requirement seems contradictory to the hydrofoil technology. While a traditional watercraft is stable, a hydrofoil-based watercraft is famously unstable. It is for this reason we are developing a system that is partially lifting, the uncertainty here lies in assumption that that we can reduce water resistance without compromising on the stability with this new technology.
Another constraint is limiting the power to 1500W, this is done for multiple reasons including: i) The mid-drive motors available for pedal assist systems are not very powerful; ii) A 800Wh battery can provide up to one hour of usage; iii) Controlling the cost.
The biggest challenge, by far, in designing the waterbike is to control the cost of manufacturing, ENVO is only considering the manufacturing methods and processes which does not necessarily need economy of scale to be successful. We are well aware of the niche aspect of this product and that the first designs may not be able to sell in a mass scale, hence the design is developed with keeping this in mind.
Work in 2019 centered around the conducting of experiments aimed at better understanding the technological uncertainties that we were facing. Despite gaining a stronger knowledge base of power and technology requirements through a number of tests, we were unable to design a device that successfully lifted its own weight. In FY2020, we focused on kayaks rather than surfboards, upgrading our mechanical designs and electronics to better test our prototypes in the summer. We used this test feedback to perform iterations of hull and hydrofoil design, accommodating better stability and a more comfortable and drier ride for the user. We developed electronics and sensors to enable better system performance checks and data collection for our motors and controllers. Additional modifications were made towards waterproofing the electronics and increasing battery capacity for more current discharge. These modifications allowed us to continue testing in the summer of 2020. We tested this system on a real kayak in ocean and were able to get lifting force from the hydrofoil system but this idea was abandoned due to stability concerns.
Where we are:
Prototype 1 (2020):
Work in 2019 centered around the conducting of experiments aimed at better understanding the technological uncertainties that we were facing. Despite gaining a stronger knowledge base of power and technology requirements through a number of tests, we were unable to design a device that successfully lifted its own weight. In FY2020, we focused on kayaks rather than surfboards, upgrading our mechanical designs and electronics to better test our prototypes in the summer. We used this test feedback to perform iterations of hull and hydrofoil design, accommodating better stability and a more comfortable and drier ride for the user. We developed electronics and sensors to enable better system performance checks and data collection for our motors and controllers. Additional modifications were made towards waterproofing the electronics and increasing battery capacity for more current discharge. These modifications allowed us to continue testing in the summer of 2020. We tested this system on a real kayak in ocean and were able to get lifting force from the hydrofoil system but this idea was abandoned due to stability concerns.
Prototype 2 (2021):
In 2021 ENVO pivoted from a conversion-kit based hydrofoil system to a fully integrated watercraft featuring a hydrofoil due to the inherent stability of this system. Different configurations including monohull, multihull (catamaran, and trimaran) were considered. Numerical experimentation was conducted on these different configurations and catamaran style was selected due to its high stability and low resistance.
In the second half of the design, the pontoons of catamaran were designed through an iterative process. Computational Fluid Dynamics (CFD) experiments were conducted to optimize the shape of the pontoon and the most efficient shape for the design load was selected.
ENVO next designed a detailed CAD design and a prototype based on this design was manufactured. Waterproofing the electrical components was a major concern, hence a chain driven pedal drive was used which ensured that none of the electrical parts came in direct contact with the water. An ebike mid drive motor powered this pedal drive, and a pedal sensor integration meant the whole system was pedal assisted. This innovation allowed us to not only solve water proofing issues but added an extra feature to the product. Furthermore, the hydrofoil was attached to the mast of the same pedal drive.
The pontoons were made from drop-stitched inflatable material because the traditional inflatable material could not manufacture the required shape.
A special clamp-based frame was designed which allowed us to change the geometry of the frame and a DOE based experiment matrix was devised to identify critical parameters that may have impact on performance of the watercraft. Over a series of experiments, we were able to identify optimized parameters that allowed the water bike to move at the speed of 19km/h. In comparison the same water bike without the hydrofoil only went up to 12km/h speed. This would make the prototype a success.
For 2022 we can focus on making the prototype into a mature product and change the single pivot feedback mechanism provide a more smooth transition and control, furthermore the current system is optimised for weight of a single rider but it needs to cater to a range of weights before going into production.
Prototype 3 (2023):
The first crucial phase involved mesh generation to enhance the resolution of fluid flow. This process incorporated automated methods and mesh refinements, focusing on critical areas such as the hydrofoil, bow, and free surface. The goal was to ensure that the simulation accurately captured the complex dynamics of the waterbike's interaction with water.
Subsequently, the team concentrated on the physical setup, employing multiple models, including Implicit Unsteady, Multiphase, Volume of Fluid (VOF), Turbulent, and K-Epsilon Turbulence models. These models provided valuable insights into the behavior of the two-phase system, consisting of water and air, a pivotal aspect of our hydrofoil's operation.
The simulation treated the flow as a two-phase system, utilizing the VOF method to capture the free surface and cavitation characteristics accurately. Realistic flow conditions were integrated, including specified inlet velocity and damping measures to prevent boundary reflections, ensuring that our simulation mirrored real-world scenarios. Additionally, we considered the waterbike's motion by accounting for its relative movement in the simulation. The Dynamic Fluid Body Interaction (DFBI) model was employed to capture heave and pitch, enhancing the simulation's realism. Our analysis extended to detailed visualizations and data analysis tools, which aided in the assessment of the simulation results. We meticulously considered solver parameters, including time-step and inner iterations per time-step, to maintain the transient nature of the simulation. The post-processing phase involved extracting crucial data, such as drag and lift forces, watercraft resistance effects, wake characteristics, and watercraft motion, providing essential information for further analysis and design refinement.
Our progress in 2023 represents a significant milestone in the development of the Water Bike. We remain committed to pushing the boundaries of innovation in hydrofoil technology and are dedicated to brining this groundbreaking waterbike closer to redefining water-based recreational activities. As we continue our journey, we look forward to sharing further updates on our ongoing efforts to transform waterbike technology.
