Why do modern phones and laptops still depend on batteries and charging? Could we design them to generate or collect enough energy to keep running indefinitely, instead of eventually needing a recharge or replacement power source?
3 Answers
The simplest solution is to use a device that stays plugged into the wall. Desktop computers and some other electronics avoid battery limitations that way, but portable devices need stored energy because they can’t remain connected to an outlet.
Perpetual machines aren’t possible because every real system wastes some energy as heat and friction. You can make equipment that runs for decades with minimal refueling, but it still needs an energy source. Nuclear or radioactive power sources can last a very long time, yet they bring serious safety, health, security, and cost problems, so they aren’t suitable for ordinary consumer electronics.
A device can’t run forever without receiving energy from somewhere. The second law of thermodynamics means there will always be losses, so a system has to draw power from a source such as a wall outlet, sunlight, fuel, or stored energy. The real challenge is finding a source with enough power density for demanding electronics while keeping it safe and practical.
Some low-power devices already operate without conventional batteries, such as solar calculators, RFID cards, and crystal radios. They work because they need very little energy. Phones and laptops perform much more demanding tasks, so they need a much stronger and more reliable energy source.