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Public domain image.</sub></center></div>

If you hook a bicycle up to an electric generator you could power the appliances in your house for free.

Is such an idea feasible and how long would you need to pedal your bicycle to run the electric devices in your life?

These devices are for sale on the internet, they seem to have been more popular in the 1970's than they are now, for good reason. This post explains why.

### Daily Energy Generation

I go to the gym on a regular basis and on occasional I have used equipment that measures power output. Power peaks of 300 to 400 W are indeed possible but they are not sustainable unless you are in very good shape.

If you are just in regular, non-couch potato shape then a sustained power output of between 100 to 200 W is more realistic. Let's be generous and say you can output 200 W for two hours before conking out.

A power output of 200 W is 200 joules per second and if your legs spun the generator for 2 hours you would have generated 200 J/s x 3600 s/hr x 2 hrs =  1,440,000 joules of energy.  

<div class="pull-right"><img src="https://cdn.steemitimages.com/DQmVh1gJGNcozGnwtUEZPejDqu2ZoubUJv7WJPh6ULeobfZ/image.png"><br><center><sub>Schekinov Alexey Victorovich <a href="https://commons.wikimedia.org/wiki/File:Electric_kettle_-_%D0%AD%D0%BB%D0%B5%D0%BA%D1%82%D1%80%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B8%D0%B9_%D1%87%D0%B0%D0%B9%D0%BD%D0%B8%D0%BA.JPG">link</a>
CC BY-SA 3.0 license</sub></center></div>

### Electric Appliance Energy Usage

Let's say that this energy is stored in a battery bank and ready to run any appliance in the house. What then could we do with this 'free' energy?
 
##### An Electric Kettle
An electric kettle consumes 1500 W of power. A cup of water is about 0.28 litres, let's round this up to 0.3 litres to account for evaporation due to steam. and to make the math a bit easier. 

The heat capacity of water is 4186 joules per kilogram per degree Celsius. A litre is a kilogram so this means we need to use 4186 x 0.3 = 1256 joules to heat our cup of water up 1 degree Celsius. If the water started at 10°C and ended up at boiling (100°C) then it would have heated up by 90°C.

This means that we would need to use 90 x 1256 = 113,000 joules to bring that cup of water to a boil to make our tea. A watt is 1 joule per second so a 1500 W kettle outputs 1500 joules per second. This means the kettle would need to run for 113,000 / 1500 = 75 seconds to boil that cup of water.

Our battery bank has 1,440,000 joules of energy stored in it and boiling a cup of water would consume 
about 8% of the total. Using a system like this you could boil make 12 cups of tea a day for 2 hours of hard bicycle work.

Ugh. This is clearly not feasible. You cannot run a bicycle generator until you are exhausted just to make about 12 cups of tea. It would be far easier to cut down a tree, split the wood and make a fire than to use a bicycle generator system.

<div class="pull-left"><img src="https://cdn.steemitimages.com/DQmarw1KcLAqPos9XL9YPtuRQkHgx2iU9R7JDQGf1yGXzF1/image.png"><br><center><sub>Jiří Sedláček <a href="https://commons.wikimedia.org/wiki/File:Verbatim_LED_light_bulb.jpg">link</a>
CC BY-SA 4.0 license</sub></center></div>

###### LED Lights

Okay, let's move on to low power LED lights.

A 10 W LED light can output the same amount of energy as a conventional 60 W filament light bulb. Running a 10 W bulb for a hour would consume 10 W x 3600 seconds = 36,000 joules of energy.

This is about 2.5% of the energy stored from the bicycle generating system. This is a bit better, a bicycle generating system could light up your house and possibly also play a stereo for a few hours each evening. If you were in a very isolated location with no solar panels this might be feasible on an occasional basis.

### System Energy Losses

The real situation is worse though due to the many energy losses in the system.

The electric generator might have losses of between 10 to 20 percent, the voltage convertor might have a 5 percent loss and the voltage regulator could have a 20 to 25 percent loss (which is why they get so warm). The battery could have losses of 10 to 20 percent and if the battery was left to sit it would slowly lose its energy.

<div class="pull-right"><img src="https://cdn.steemitimages.com/DQmRRy6Ku9BM9F4kCwH1bjcdRCD2X5sPRykLu3NrKrRnenD/image.png"><br><center><sub>Maxpixel.net <a href="https://www.maxpixel.net/Electric-Generator-Equipment-1690437">link</a>
CC0 license</sub></center></div>

It all adds up and the total usable energy from a human-powered generator system might only be 50 percent of what you put into it.

### Closing Words

It seems that bicycle generators were briefly a saleable item a long time ago to a niche group of people (back-to-the-land homesteader types). However people quickly found out that they were not the source of free energy that they expected as the simple math in this post clearly demonstrates.

It would be far easier to burn wood for cooking, heating and boiling water. It would also be far better to set up solar panels or wind turbines to charge up your battery bank.

Instead of using your human muscle power for generating electricity, just chop some wood and make a fire.

*Thank you for reading my post.*

#### Post Sources
http://www.econvergence.net/category-s/1817.htm
http://www.instructables.com/id/How-To-Build-A-Bicycle-Generator/
http://www.lowtechmagazine.com/2011/05/bike-powered-electricity-generators.html
https://en.wikipedia.org/wiki/Heat_capacity