back

Thoughts regarding our "Stromvelo"

The "Stromvelo" (current bicycle) as we also call our Muscle Power Generator, is a machine, with which electric current can be produced for charging the solar batteries by pedalling on the spot, as this is done with a hometrainer.
Our current bike
Our current bicycle


Too often it has been observed that young people light up the whole house, even if they are only in one room. While this is in houses with mains connection only a waste of energy, it leads in a mountain building with a solar electric supply to the early exhaustion of the batteries. Then with genuine need of battery power, there is possibly no reserve available. If the sun shines daily, this is probably no great problem; however, during rainy days or scarce radiation due to overcast skies, there will be no supply of electrical energy and the batteries will stay empty.
Construction
the construction

Surely we could have made another energy source available (e.g. a gasoline engine with generator operating a battery charger). We prefer however an educational source, which our Muscle Power Generator truly is. - So, if the batteries are empty (or already if the control unit of the solar electic plant indicates low reserve), the youngsters should (preferably in groups) descend to the basement and push the pedals strongly. They are to feel in their muscles, what effort it takes, in order to produce only e.g. 100 Watts, which normal bulbs or the PC use in the minimum.

We do hope that this instructive experience leads to more conscious and responsible handling of electrical energy.
Generator
generator and V-belt
 The idea for this construction I have received from my engineering colleague Rudolf Bertschi in Zürich, who has built a similar machine for himself and his children. - For our application we have designed a rather complicated electronic control network, which provides a number of features that are described further down in this description.

Basically the machine consists of an old bicycle, an old alternator of a scrap car and a long V-belt, which runs in the rear wheel rim. A sturdy, welded construction holds the whole device together (see pictures). Everything (machine and electronics) was assembled in the cooperation of my older son Matthias (technician), who also serves as webmaster for this homepage, and me (electrical engineer) during the winter 2002/03.

For the purpose of illustration the operating instructions for the Muscle Power Generator are copied here, as they are fastened to the wall next to the machine.

Control Panel
Control Panel



Operating instructions for the muscle power generator

The BSOP Muscle Power Generator is an emergency power generator, which enables us to charge the solar batteries by means of muscle power, should there charge level have dropped too low due to lack of sunshine or high consumption. The pedals' torque that corresponds with the slope of the road and the choosen gear on the regular bicycle, can be adjusted step-free with a control knob, so that the favorite torque can be chosen exactly at the best r.p.m. for each individual (the chain gears are fixed).
The following is to be considered: The max. permitted current (equivalent to the max. pedal torque) is limited by the electronic control circuitry to 15Amps (to protect the mechanical construction against excessive wear and abuse).
If the battery voltage reaches 15Volt (battery fully charged), the electronic controls reduce the current likewise (reducing also the pedal torque), so that the voltage cannot rise more (for the protection of the battery).
The electronic control circuitry also permits an energy measurement, in other words different pedallors can involve in a competition, e.g. who can work the most (or put most energy into the batteries) within e.g. 15 minutes. The built in bicycle tachometer indicates in the position KMH the charging current in Amps, in the position TRIP the executed work (or gained energy) in ah (amp-hours) and in position DIST the total of all to this date executed work in ah. If a competition is to be started, the TRIP indication should be reset to 0.0 before each start of a fresh person. DIST cannot be reset by the user.
A person, who would like to carry out maximum work, should not pedal real hard from the beginning (no short sprint), which leads to rapid fatigue. In contrary we must give time to our body, so that it can make its stored energy available. This is different depending upon age and physical condition and requires at first low pedal torque at the most pleasant pedal r.p.m. in the beginning. During the following approx. 5 minutes then the pedal torque can be continously increased, until the power level is reached, which can be held for a longer duration. - 7Amps correspond to approx. 100Watt electrically; due to the efficiency of the entire set-up of approx. 50 percent this corresponds to an effort of about 200Watt, which is really good exercise!



And this is what you have to do:
Hanspeter Wirth




back