Devices that store energy to use later!

We often make devices that used stored energy. Rather than having to plug the device into a mains socket we can store energy in the device to use at a later time.

Electrical battery devices

These store energy in the form of chemical energy. This is converted to electrical energy in when the battery cells are inserted into a circuit and the circuit switch is closed.

Rechargable batteries

These store energy as chemical energy (like all batteries do!).

They can be charged when they run out of chemical energy. To do this the process of 'using them' is reversed. When you 'use' a battery, you transfer its chemical energy into electrical energy to drive some device or other. When you charge a battery you put electrical energy into the battery that is then stored as chemical energy.

To do this you usually have to insert them into a specially designed charging device. This converts the mains voltage into the voltage required by the batteries and then the electrical energy is stored as chemical energy.

Some devices can be 'charged' in another way. They can use electrical energy produced by solar cells to charge their batteries. One example of this use is garden lights.

During the day the Sun's energy is converted to electrical energy by the solar cells. Then at night that stored chemical energy is changed into electrical energy to power lamps. These change the electrical energy into light energy.

By storing the sun's energy solar garden features can be made to 'work' even on cloudy days. By incorporating a 'backup' rechargable battery the Sun's energy can be used in conjunction with stored energy to give a steady flow of water.

A typical water feature will incorporate a solar panel (to collect the Sun's energy and convert it to electrical energy), rechargable batteries and an electric pump (to convert the electrical energy into gravitational potential energy of the water). The GPE is then transferred into kinetic energy as the water cascades.

Storing energy in a spring

When you wind up a mechanism that has a spring inside it, you tighten the coil of the spring. That stores the energy you put in (by doing the winding work) in the form of stored eleastic potential energy. If that spring is then allowed to unwind, that energy is released; and can be transferred as kinetic energy to turn an electric generator. The energy form is then electrical and this can be used power a wind-up radio or torch.

This vid clip shows a radio that has no batteries at all - it is just powered by the spring inside - that you wind up!