I challenge anyone to build a more efficient way of converting human power into electrical power! In this project we use an NXT stationary bike to drive a 149kv outrunner via a flat belt. The outrunner works as a generator and by using the VESC6 motor controller we apply regenerative braking. The power generated is fed into a 480Wh battery and a grid tie inverter feeds this power into the grid.
If you are looking for more details, kindly visit our website.
During the English winter it often rains for weeks. Having an indoor trainer is convenient to keep one's fitness ticking over. Ever since I was young I have always been interested in the idea of generating electricity through pedal power. In my workshop it gets very cold and having an exercise machine to do 1-2 minute high intensity sessions gives me another way of staying warm. So there’s 3 reasons I did this project. I hope you find this write up interesting.
This diagram shows all the parts to the project. I think they are all quite self explanatory so I’ll move on to discussing the individual aspects
The motor mount hinges on a shaft and springs maintain proper tension on the flat belt to prevent slippage.
BLDC motors are normally designed to spin propellers which creates an axial load. Consideration has to be paid to how the rotor is loaded when a radial force is exerted such as in this scenario. Luckily this motor has internal bearings on either side of its drum so the shaft doesn’t experience any moment loads. Moment loads on shaft interfaces or bearings cause much faster wear.
Arguably this is a small point, but should mean the motor lasts a fair bit longer. The belt applies several kilograms of radial loading to the rotor.
Flat belts are incredibly efficient but to track centrally on the outrunner it needed to have a crown. I achieved this by wrapping sellotape around the rotor to build up thickness in the centre relative to the sides. This worked well and the belt stays central and runs smoothly.
The NXT Bike’s flywheel has a huge amount of inertia and stays spinning freely for ages without any connected load. I put the flat belt around the flywheel so it drives the motor with a 7.4:1 gearing. There is a 3.25:1 gearing between the pedal crank and the flywheel. Overall there is a 24:1 gear ratio. Therefore a cadence of 90 rpm spins the 149kv motor at rpm which would generate 14.5 volts.
The VESC6 is Benjamin Vedder's ESC. The hardware and software is open source. I actually bought the components and reflowed my own board but you can buy the fully assembled product online (for a price). I didn’t populate the CAN or Bluetooth chips.
It’s a beautiful bit of hardware and the software is remarkable. You can drive motors using super smooth FOC and control all sorts of parameters such as torque, current limits, motor speed etc. You can customise the software but instead I use a simple Arduino Pro-Mini to interface with the VESC6 via UART.
I mounted the VESC6 in a plastic enclosure with some additional bulk capacitance and an Arduino Pro-Mini. The Arduino interfaces with the VESC6 via a UART connection and runs some code. It reads the selected power from a 6-position rotary switch (50, 100, 150, 200, 250, 300 watts) and implements a PI control algorithm. The power is read from the VESC6 and the PI controller adjusts the regenerative torque on the motor so as to realise the demanded power. This means that regardless of the speed you pedal at, the mechanical power you are putting out is constant. Slow cadence will demand high torque and vice versa.
Whenever there is lots of bulk capacitance there’s always the problem of sparks on connecting the battery. I bought a 3 position switch. To turn the device on you have to go through the middle switch position which connects the VESC6 to power through a 5 ohm resistor. This quickly pre-charges the capacitors. The switch is then turned to the fully on position which shorts out the resistor and connects the battery directly to the VESC6.
Rather than run a dozen wires to the arduino from the 6-position switch I use a resistor divider method to generate 6-different analogue voltages. A single ADC channel on the Arduino can then read the voltage and determine the switch position.
The software is available here on github. The code is simple and self explanatory.
The VESC needs somewhere to dump the electrical power. It takes the AC electrical power from the generator and converts it into DC which is fed into a 24v 20Ah LiFePO4 battery. The VESC6 provides a huge performance benefit over a full bridge rectifier. For 2 reasons:
On Facebook marketplace I found a W grid tie inverter. It’s designed as a solar MPPT with an input voltage range of between 22-50V. I wasn’t quite sure how such an inverter would perform when connected to a 26V battery. Thankfully it works beautifully. Since the battery voltage is at the lower end of the acceptable input voltage, the MPPT appears to throttle down its output power to 300-400 Watts. This suits us quite nicely because I don’t want W being drawn from my poor batteries. I discharge the batteries using the GTI if they are becoming a bit full and if I pedal at the same time then the batteries are only being discharged at about 0.5C which is fine.
When pedalling I wanted the rotary switch to select the mechanical power at the pedals rather than electrical output power. I therefore did my best to try to calculate the drive chain and electrical losses and account for these.
After pedalling at about 200W for 10 minutes I felt the motor and the VESC6. I was really pleased to note that neither were hot. In fact they were barely even warm. I took some thermal imaging pictures and you can see the motor warmed to about 20 degrees above ambient and the VESC only about 5 degrees. Interestingly the capacitors were what got warmest and I suppose this is due to the current ripple they experience. After seeing this I added a uF capacitor near the input to the VESC. This subjective assessment made me think the losses couldn't be more than about 25W.
In an attempt to get a more objective calibration I figured that I could run the generator as a motor to spin the pedals at a nominal cadence and measure the electrical power required to maintain this freewheel. I deduced that the electrical losses should be entirely symmetrical regardless of whether the motor is applying positive or negative torque. Hence when cycling at this nominal cadence the same losses will be present.
It’s a 12 pole motor, the flywheel to motor gear ratio is 1:7.4 and the pedal to flywheel gear ratio is 1:3.25. Therefore 1 rotation of the pedal crank equates to 24 motor rotations. An ERPM of corresponds to a cadence of 90 rpm.
At 90 rpm the drive chain and electrical losses appear to be about 22W. I think this estimates losses well and I don’t think the losses will drastically increase with increasing motor currents. So to keep things simple I have assumed a fixed 25W drive chain loss regardless of cadence or torque. It doesn’t take into account:
Next I got on the bike and took measurements of electrical power into the battery for different selected powers. When the VESC said it was measuring an input Voltage x Current of 290W, I only measured 242 W using my multimeters. I was slightly disappointed by the discrepancy and blamed VESC inaccuracy.
These measurements allow me to correct for the offsets measured by the VESC. For example when I asked the VESC to apply 40W regen I actually measured an electrical output power of 25W. We know that there are 25W of drive chain losses so the overall mechanical power must be 50W.
Likewise with 190W requested I measured an electrical power of 158W. I assumed 28W of losses so this correlates to a mechanical power draw of 158+28 = 186W. I plotted these values on a graph and got the equation of best fit.
These measurements allow us to estimate efficiency. A 272W mechanical power produces 242W of electricity which is 89% efficient. At 186W mechanical we get 85% efficiency. Not bad!
Mechanical Power = 0.882*Requested Power + 16.4
Equivalently:
With competitive price and timely delivery, Powrloo sincerely hope to be your supplier and partner.
Requested Power = 1.13*Mechanical Power - 18.6
This allows us to know what regen power to ask the VESC to apply for a desired mechanical power output.
I’m pleased with this build. I’ve accumulated a few hours whirring away on this turbo and there have been no problems so far. The power selections feel about right although it’s very difficult to judge from pedalling!
If anyone can suggest any improvements I’d be keen to hear from you!
Are you tired of spending money on a gym membership or constantly charging your electronic devices? What if we told you there was a way to get a great workout and generate electricity at the same time? You might even be able to avoid paying any gym membership or reduce your household energy bills! Yes, you read that right. Read on.
Introducing the electricity generating stationary exercise bike from British company Gym Professor Ltd. in collaboration with tech company eActive. The model will be available in the form of a retrofit eActive system and an all-new purpose-made stationary cycle called the @theGym eBike Gen1, which will soon be exclusively available through their retail store The Gym Revolution. The purpose-made eBike reported to offer almost twice the output of the eActive retrofit system.
Video of the eActive system in action
It is claimed that performing three 1-hour intense indoor cycle sessions a week on a @theGym eBike will burn in excess of calories and generate enough electricity to charge 19 smart phones or make 72 cups of coffee. While the benefits at home appear obvious, it is further claimed that commercial clubs offering the new @theGym eBikes could offer a membership reward in return of clocking up hours of use, such as a partial membership rebate for helping to power the gym. The Bristol-based @theGym training facility will be the first to roll this out to it's membership base.
The @theGym eBike is the perfect addition to your home gym or a gym club. In this article, we'll explore the benefits of this innovative fitness equipment and how it can help you achieve your fitness goals and save you money, while also being environmentally friendly.
An electricity generating stationary exercise bike is a type of exercise bike that uses the energy generated from pedaling to power electronic devices or even your home. It works by converting the mechanical energy from pedaling into electrical energy, which can then be used to power various devices.
These bikes typically have a built-in generator and battery system, allowing you to store the energy generated for later use. Some models even have the ability to connect to your home's electrical system, allowing you to power your home with your workout.
The electricity generating stationary exercise bike works similarly to a traditional exercise bike, with the added feature of a generator. As you pedal, the generator converts the mechanical energy into electrical energy, which is then stored in a battery or used to power devices.
The amount of energy generated depends on the resistance level and speed at which you pedal. The more resistance and faster you pedal, the more energy is produced.
One of the main benefits of an electricity generating stationary exercise bike is its eco-friendliness. By using your own energy to power devices, you are reducing your carbon footprint and decreasing your reliance on traditional energy sources.
In fact, a study by the University of Oregon found that using a pedal-powered generator for just one hour can generate enough electricity to power a laptop for 24 hours, which ties in with @theGym's claims of the possible power output. Imagine the impact if everyone used an electricity generating stationary exercise bike in their home gym or club.
Another benefit of an electricity generating stationary exercise bike is its cost-effectiveness. With a one-time purchase, you can have a piece of equipment that not only helps you stay fit but also saves you money on your electricity bill.
Additionally, by eliminating the need for a gym membership, you can save even more money in the long run. This makes it a great investment for those looking to create a home gym on a budget.
Electricity generating stationary exercise bikes offer a versatile workout experience. Not only can you adjust the resistance level to suit your fitness level, but you can also choose to focus on generating electricity or simply getting a good workout.
Some models even come with additional features such as built-in screens for entertainment or tracking your workout progress. This allows you to customize your workout experience and stay motivated.
Before purchasing an electricity generating stationary exercise bike, it's important to determine your energy needs. Consider what devices you want to power and how much energy they require. This will help you choose the right bike for your needs.
To fully incorporate an electricity generating stationary exercise bike into your home gym, it's important to set up a dedicated space for it. This can be a corner of a room or a separate room altogether. Make sure the space is well-ventilated and has enough room for you to comfortably use the bike. A garage gym being a good choice, also.
Like any piece of fitness equipment, an electricity generating stationary exercise bike is only effective if you use it regularly. Make it a part of your daily routine and set achievable goals for yourself. This will not only help you stay fit but also ensure that you are generating enough electricity to make a difference.
Sorry, not sorry. If you read this far, well done, as it is in fact an April Fool, but the concept is not entirely foolish. While this article was created as an April Fool joke to trick our members and customers into thinking they may get free gym membership, it should also highlight what is truly possible and pose questions, such as "why aren't we using electric generating stationary bikes in our home or commercial gyms?", as well as similar questions in other industries. In most cases, it's the cost to produce the product, compared to what already exists...and how much energy it even produces/ saves; however, with technology improving and moving forward at a fast pace, the trend toward eco-friendly products, and the tech coming down in price, perhaps in 10-years time this article could be a reality and not as foolish at it first appears. We hope so.
The Pedal-A-Watt is an electricity generating stationary exercise bike that has been featured on various news outlets in the US and even used in schools to teach students about renewable energy. It can generate up to 400 watts of electricity and has a built-in battery system for storing energy.
Lithuania’s Tukas EV company has tentatively entered the fitness market with their HR Bank. Looking like basic stationary bike, they've carried over the technology from their existing EV company to the stationary bike in the hope of releasing it on the market in Europe.
The Green Revolution is another US company that specialises in creating electricity generating stationary exercise bikes for commercial and residential use. Their bikes can generate up to 300 watts of electricity and have the option to connect to your home's electrical system.
An electricity generating stationary exercise bike seems a simple and straightforward idea and is far from being a new concept. With the increased cost of energy prices and battery tech coming down in price, as well as market forces driving us to "eco-friendly" products, maybe what was once solely a nice idea (a gimmick!) may have genuine commercial merit and be a viable future product for the fitness industry and beyond.
Are you interested in learning more about energy generating exercise bike? Contact us today to secure an expert consultation!