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|3||30W Mono-Crystalline Solar Panel|
|3||3mm Acrylic Sheet (1015x510mm)|
|1||250W Hub Motor|
|1||24V 10Ah Lithium-ion Battery|
|146||Assorted Bolts and Nuts|
|24||3D Printed Skeleton Adjusting Parts|
Did you know that EVs (Electric Vehicles) such as electric bikes and cars indirectly cause pollution?
Their byproducts through function may not be harmful to the environment, but their energy generation processes are. Renewable energy in some cases accounts for as low as 8% of the National Grid’s generation. This means that when an EV is charged, it has contributed to pollution indirectly since the power it receives is predominantly from non-renewable energy sources.
Renewable energy sources such as solar power must be harnessed to their maximum potential. My research has found that when they are used as the sole energy producer, they fail to provide adequate and reliable power. However, when used in conjunction with another energy source as a hybrid system, they can significantly reduce the number of emissions produced. These hybrid systems are still at an early stage of development and have yet to been implemented on a large scale.
My project has taken the initiative to demonstrate how effective these hybrid systems may be in reducing overall emissions. A bike was used as the starting point. An electrification kit was designed to have an almost universal fit to traditional bikes. The kit would attach to the bike converting it into an electric one by harnessing renewable energy.
Research has been conducted on the various sources of alternative energy suitable for an electric bike to harness power for a motor to assist with pedalling. The research was conducted on the following technologies: solar power, wind power, regenerative braking, and dynamo generators. This was done to investigate how they could be implemented within an electric bike to allow for the capture of energy and to determine whether they would be suitable and worth installing. Moreover, calculations alongside pre-made scenarios were made to allow for an accurate prediction of the power output from each alternative energy source. This determined whether the energy source was worth installing on the electric bike.
After all sources of energy had been investigated, initial conceptual design ideas were made to demonstrate how they captured different energy sources for a bike. These initial design ideas were reduced to a final draft design idea by using a weighting table that scored the designs appropriately based on a criterion. Further concepts were made from the final draft design idea to allow for a true final design idea to be developed in greater detail. This true final design idea was also selected with another weighting table based on a criterion. This was done to ensure that the final design idea was the most efficient in capturing other energy sources.
Computer-Aided Design (CAD) software such as Autodesk Inventor was used to model and test different frames. This was done to demonstrate how the solution would fit onto each frame, it would also allow for the observation of the limitations of each frame and the necessary adjustments. CAD was also used to model the testing frame which would be used for stress and aerodynamic analysis.
Finite Element Analysis (FEA) was used to demonstrate the effect the solution would have on a frame. Effects like the stress due to weight, stress due to crosswinds and placement of the design onto the frame. FEA was also used to model wind flow within an enclosure to observe the aerodynamics of the design. This later resulted in adapting the solution to allow for better aerodynamics to consume less power whilst overcoming drag effects lowering the chance for on-grid charging.
Three 30W mono-crystalline solar panels were chosen for the kit because it was the most balanced option in terms of weight, power production, cost, and size. Other solar panels would be able to produce more power but would be heavier, more expensive, and more intrusive because of their larger size.
This kit would allow for the two vertical solar panels to snap and lock outwards to lay parallel with the horizontal panel. This can
be done when the bicycle is parked or moving in an open environment where obstacles that the solar panels may hit are not a concern. Allowing the vertical solar panels to open outwards will increase the efficiency of the solar panels since they will be exposed to more direct sunlight. Greater efficiency will allow for greater power production for the bicycle, thus increasing the range.
The maximum power production of this kit with 100% efficiency is 90W. This means that even during heavy clouds and rainy conditions where power output is expected to be around 10%, the solar panels will still be able to produce 9W which still increases the range of the bicycle. This is because the overall energy consumption of the bicycle will be lower than traditional electric bicycles since energy is being produced which collectively lowers the consumption.
The conversion kit will be attached to the rear frame of the bicycle and will take advantage of the pannier rack fastening locations. This is kit is intended to easily fit onto almost any traditional bicycle and convert it into an electric one. The kit will constitute a clasp that will connect to the seat tube. This is to ensure all degrees of freedom are constrained and provide an alternative fastening point for bicycles that do not have pannier fastening points.
The solar panels will be reinforced underneath with a 3mm acrylic sheet. This will act as the solar panel’s skeleton to allow for the connection of other solar panels and components such as the solar and motor controller. Acrylic was chosen as the panel’s skeleton because of its strength to mass ratio. Other materials with better strength to mass ratios, such as aluminium and steel were considered, but they were deemed too heavy for this application. Their strength was also unnecessary as the three panels in total would only weigh 3kg. Each acrylic sheet would add an extra 0.8kg to their panel which is significantly lower than other materials. Whereas, materials such as aluminium would add an extra 3kg to each panel. Not only will the extra weight significantly affect the stress distribution of the kit and bicycle, but it will also lead to the consumption of more power.
Acrylic was also chosen because it does not rust like metals. This is important because the bicycle will be exposed to different weather conditions like rain. Also, acrylic has a yield strength of 69MPa so it will be able to withstand stresses. Furthermore, acrylic allows for the customisation of the panels. Different colours of the panels are available to the consumer, producing a more personal aesthetic. Additionally, acrylic can be recycled and re-used which benefits the environment and further promotes the credentials of sustainability and lowers the carbon footprint as a solution.
The skeleton will be bolted to the frame of the solar panels and further secured with epoxy adhesive between the acrylic and frame. Two rails will be connected to the horizontal solar panel’s
skeleton. This is to allow for connecting struts to be adjusted by sliding rail hooks on the rail to allow the kit to fit onto almost any bicycle. These connecting struts can be extended and rotate back and forth to allow for adjustment in all degrees of freedom. These connecting struts can be manufactured out of plastic to save weight and cost. The rail hooks will feature a fastener to allow the cyclist to tighten the rail hook into the desired position.
Four folding brackets will also be connected to the skeletons to allow for the opening of the solar panels. Brackets of 350mm length were used to ensure that most of the solar panel's length was fastened. This is to prevent wobbling and excessive stress on the component.
A 24V 10Ah lithium-ion ready-to-use battery was chosen for this design. The capacity of this battery can provide 12 to 24 miles on a full charge which will be significantly increased when it is being charged whilst used. This battery will secure onto the bottle holder fastening locations that almost every bicycle has. This further ensures that the kit will be almost universal for non-electric bicycles. This battery is removable to allow for on-grid charging if the kit was not able to sufficiently charge the bicycle. This ensures that the bicycle will never be un-useable because of a lack of charge. Furthermore, this battery can also be locked to prevent theft.
The battery’s fastening method can also be adapted for frames that do not accommodate bottle holder fastening points like folding bikes. Straps can easily be used for frames like these.
Although lithium-ion batteries are more expensive than other conventional batteries, they were chosen because they can be recharged hundreds of times because of their high energy density. This means that more energy can be stored within its volume than other batteries, making it the best choice for electric bicycles and the environment.
A 250W front hub motor will be used to deliver power from the battery to propel the bicycle. This was chosen because laws and regulations within the UK restrict the power output of an electric bicycle’s motor to 250W. This power rating is also suitable for this application as its not underpowered. A front hub motor was chosen to allow for easier swapping of the wheels. Had the motor been situated at the rear wheel, then the whole transmission system of the bicycle would have to be removed to install the motor. Having the motor at the front also produces better balancing of moments on the bicycle since most of the kit’s weight will be located at the end. This balance of moments should improve stress distribution and rideability.
A pedal assist controller will be attached to the handlebars of the bicycle to allow for easy toggling of levels. The pedal assist sensor will connect to the pedals to detect and measure the use of the pedals which will send feedback to the motor controller. The motor and the solar controller will be fastened to the horizontal acrylic sheet using S-shaped brackets.
A strip of LEDs will be connected to the back of the horizontal solar panel. Two reflectors will be attached to the rear of each vertical solar panel. This is to provide visibility to other road users when the bicycle is being driven at night. The LEDs length has been calculated to not consume too much power whilst still providing a suitable level of visibility. The strip is also aesthetically pleasing and takes influences from modern car designs. This gives the conversion kit a more modern aesthetic especially at night which will further promote the credentials of renewable transport being part of a modern future.
The end results?
This conversion kit was able to produce a greater range whilst also being cheaper than a traditional electric bike. The conversion kit can also be used on most non-electric bikes as it was designed to have an almost universal fit with an adjusting mechanism. Although this conversion kit is superior to traditional electric bicycles in terms of power production and costs. Ultimately, the kit’s dependency on the weather heavily limits the potential of the kit but since pedalling is still the main mode of energy generation, this kit complements the bike very well. The kit was never intended to fully power the bike, it was only meant to supplement power for pedalling assistance when it is needed. Ideally, the kit should be used in geographical locations with many hours of direct sunlight to capture even more energy from the sun reducing the chance of needing to use on-grid electricity to charge the battery.
This project has demonstrated successfully that alternative energy sources can be used to power an electric bike to reduce pollution and benefit the environment. This solution was also developed further by designing a solution that not only harnessed other sources of energy but allowed for old non-electric bikes to be re-used thus further reducing the environmental impact of bikes. The kit incapsulates free energy and enhances the sustainable credentials of cycling. Furthermore, this project serves as a highlight to demonstrate that vehicles can be partially powered by alternative energy sources. Therefore, solutions such as this kit can be developed further for applications such as cars and HGVs as a hybrid to reduce pollution from emissions.
Although alternative energy sources are not always reliable as the sole energy provider, this project has shown that when used to complement another energy source, they can perform very well. With future technological advances, alternative energy may become more reliable and the popularity of solutions like this will only increase.
Much more work must be done to develop this solution. It must be manufactured and tested in real scenarios to give accurate results of power production and performance. This solution has tremendous potential in reducing emissions, not only by making electric bikes greener but acting as a substitute for transport like cars and motorbikes.
Solutions like this may very well be the key to tackling emissions and global warming.