Introduction: Potential Energy to Electrical Energy Converter (PE3C)

About: A brief description of my experience in Automation, Control and Robotics I have spent the last 20 years working in the areas of DCS (Distributed Control Systems), ESD (Emergency Shutdown Systems), and PLC (Pr…


In these times, where the use of renewable energies is of utmost importance, the proposals that arise regarding this, must be considered very seriously since our future could depend on it, and that of our spacecraft: "Planet Earth" .

One of the most popular proposals is that of solar panels, however systems based on these panels have several drawbacks:

1) Although the price has decreased, the cost of solar panels is still high

2) The efficiency is very low

3) Energy storage is through battery systems or recently super capacitors, which makes systems based on solar panels much more expensive.

4) On rainy and cloudy days and at night the solar panels are totally inefficient.

But what if we can design a system that is capable of storing solar energy for indefinite periods of time?

Well, that is my proposal, a mechanical system based on a simple machine: The Belt and Pulley System.


1 Motor DC with gear box (1)

2 Wheel (1)

3 CD's (5)

4 Wood pieces (12cmx4.5cmx2cm) (2)

5 Wood piece (7cmx4.5cmx2cm) (1)

6 Wood piece / Base (40cmx7cmx2cm) (1)

7 Cork piece (1)

8 Plastic cap (3)

9 Can (diameter: 14 cms) (1)

10 Hardware (screws, bolts...) (LOT)

11 Elastic (2)

12 Led (Light Emitting Diode) (1)

13 Resistor (220 ohm) (1)

14 Soda can (1)

15 Nylon cord ( 1 mt) (1)

Step 1: Principle of Operation

Principle of operation

It is well known to many that energy is neither created nor destroyed, but transformed.

Considering this principle we can then take part of that energy produced by solar panels, or some other source of electrical energy and transform it, let's say, into Potential Energy.

The concept is very simple, if we take a mass m (Kg) and raise it to a height h (mts), then we will have a value of Potential Energy Ep = m * g * h, where m is the mass in Kg, g is the acceleration of gravity, and h is the height in meters at which the mass is.

The way we are going to raise and lower that mass is through a system of pulleys and belts.

Now, a pulley is a wheel on an axle or shaft designed to support movement and change direction of a belt or taut cable. In a belt and pulley system, a belt runs along a pulley’s groove so that the power can be transfer either from one pulley to another or from the pulley directly to the application that requires power. A pulley design to attain different diameter functions as it’s used to increase or decrease the speed of the application of its powers.

A belt drive is a loop of a flexible material that transfers movement from one rotating pulley to another. Each are held on a shaft. The primary function of a belt is to transfer power (rotary energy) from one source to another. Whereas pulley that has a groove around its circumference allows a belt to smoothly through it when transmitting rotational motion.

Figure No. 1 shows the general operation of the system:

During the day, on sunny days, the energy produced by the solar panels or another form of energy, causes the motor M to start and begin to raise the mass m to the height h, in the absence of sunlight or at night, the mass m, due to the action of gravity, begins to fall and the motor now behaves like a generator (G), providing the required electricity.

Step 2: Some Math Considerations

To be able to lift the mass m without problem, we resort to a system of pulleys and belts like the one shown in figure 2.

One of the interesting characteristics of pulley and belt systems is that we can lift large loads with little effort.

In the figure shown, we can see that the relationship between the radius of the pulley that is on the motor shaft and the radius of the following pulley (P2) is:

K1 = R / r1, where K1 is the ratio factor between pulleys P1 and P3, R is the radius of pulley P3 and r1 is the radius of pulley P1.

Similarly, the ratio factor (K2) between pulleys P2 and P4 is: K2 = R / r2, where R is the radius of pulley P4 and r2 is the radius of pulley P2

For the proposed system:

r1 = 2.5 cm, r2 = 1.5 cm, and R = 5 cm

so, K1 = R / r1 = 5/2.5 = 2; K1 = 2

This means that, for the pulley P3 of a complete turn, the pulley P1 of two turns is required.

Now, we also have: K2 = R / r2 = 5/1.5 = 3.33, which means that for the pulley P4 to make a complete turn, it is required that the pulley P2 must make 3 1/3 turns

The total ratio factor of the entire pulley system is: K = K1 * K2 = 2 * 3.33 = 6.66, that is to say that for the pulley P4 of a complete turn, 6.66 turns of the pulley P1 are required

While it is true that the speed of the pulley P4 decreases, it is also true that the force on the last pulley increases by a factor of 6.66 and the higher the K factor, the lower the force required from the motor.

Conversely, the ratio factor is 1 / K = 1 / 6.66 = 3/20, that is, 3 turns of the pulley P4 are transformed into 20 turns of the pulley P1, and therefore 20 turns of the motor shaft

There is a lot of math and formulas in this design that I do not include in this presentation, but I just want to highlight these important aspects:

1) The use of the pulley and belt system allows us to lift heavy weights with low power consumption

2) Lifting a mass to a certain height allows us to store a certain amount of Potential Energy, which, by reversing the process, can be used and transferred to the motor, which now acts as a generator, and thus obtain Electric Energy.

3) Low maintenance cost

4) Easy to install and dismantle

5) Simple in construction

6) Lubrication is not required

7) Can be easily replaced, due to its low cost.

8) Power can be transfer vertically, horizontal, or incline.

Step 3: Assembly

Figures 3a, 3b, 3c, 3d, 3e and 3f show the mounting of the motor on the piece of wood.

I removed the rubber that covers the wheel and used the yellow plastic piece as the first pulley (P1)

Figures 4a, 4b and 4c show the detail of the pulleys P2 y P3

I made the P2 pulley with a cork from a wine bottle and two pieces of cardboard cut in circles.

The P3 pulley is made up of two CDs and in the middle I placed a plastic lid of a coffee container lined with foam rubber.

Both pulleys, P2 and P3, are mounted on a piece of wood, as seen in the photos

Figures 5a, 5b, 5c, 5d, 5e and 5f show the pulley P4, made up of 3 CDs spaced by two plastic covers, one of the spaces has been reserved to place the nylon rope that supports the mass m

Figures 6a, 6b and 6c show pulleys P1, P2, P3 and P4 fully assembled

Finally we put everything together and as a result we have the system shown in figures 7a to 7i

Step 4: Electrical Conection

To test the system I used the circuit shown in figure 8.

It is a very simple circuit,

When switch S1 is in position "1":

the power source supplies voltage "V" to the motor, which activates the belt pulley system causing the mass m to rise to a height h.

When the switch is in position "2", and the mass due to the action of gravity begins to fall:

Again, the pulley belt system is activated, but in the opposite direction, which causes the motor shaft to start spin and make the motor now behave like a generator.

The electricity generated by the motor (generator) turns on the Led until the mass m touches the ground (h = 0)

Step 5: Conclusion

Belt and pulley systems are great components that can be seen in almost all applications today.

They are very important as they help to transmit rotational motion and pulley alone is used to carry heavier loads with ease.

As most of the existing systems there are advantages and disadvantages of belt and pulley systems, but despite the disadvantages and limitations that we can found, this system is a viable alternative to be considered to storage energy.

Step 6: Test

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