The traditional answer is battery power, but if you have a car or clock radio, you might not remember the last time you put batteries in it. Those types of radios don’t use kenwood radio battery power, but instead, use other sources of power. Surprisingly, these can even include getting power from radio waves!
Crystal radios were some of the first battery-less radios ever produced, and are powered by their own radio waves that come to them by the antenna. They use crystals or diodes to capture and amplify signals and convert those signals into sound waves that earphones can pick up. They aren’t very powerful, but can be macgyvered up in a pinch and are useful if you need a self-powered radio in a hurry.
Heat was also used to power radios, either through thermoelectricity or kerosene. For thermoelectricity to work, one side of an object needs to be hot while the other needs to be cold. That temperature change creates voltage, and that electricity was used to power radios. Of course, there was another way to fuse heat and power together, by using muscle.
Hand crank, pedal, and clockwork radios are all different types of radios that use humans as a power source. The moving part is connected to a generator which is powered up when the part is moved around. These radios are often used when there is no electricity to connect too, and they are useful in rural areas, on camping trips, or good to have during blackouts and emergencies.
So, while several radios are powered by batteries, others can be powered by heat, muscle, and radio signals. They might not be as effective as their electric powered counterparts, but they are good to have in a pinch and an important look into where electricity can come from.