That was a most interesting article . Probably even more relevent and interesting is the article about "Jelly Batteries " see link at the end of the first story . We are promised yet another new generation of lithium batteries with a longer life and costing10 to 20 percent of current prices . Interesting , but just one of many new Lithium batteries that are allegedly working in the laboratory . The question is , shall we live long enough to buy them .
So back to the original article . I have a background in radio , I used to teach radio theory to budding Radio Amateurs , and am a qualified radio Amateur myself . Problem number one . Think of the sun , and the amount of energy given off by it . Direct sunlight has an energy density around 1.4 Killowatts per square meter .So a 100% efficient solar panel one meter square , could run 7 electric bikes with 200 watt motors . Sadly , the best solar panels have an efficiency of around 20 % , and 12 % is probably more realistic . Now let us think about energy available from medium radio waves . This is inversely proportional to the square of the distance from the transmitter . Double your distance from the transmitter , and the power falls to one eighth . In Berlin during world war two , there were often power cuts . But the powerful Nazi propaganda transmitters never shut down , they had stand by generators . Some people discovered that if you built a crystal radio , a simple receiver that does not use batteries , you could use it to power a small torch bulb , if you lived closer than 1 Kilometer to the transmitter . I hate to tell you what happened if you were caught . Transmitter power was measured in Kilowatts . As from 2015 , all radio broadcasting in the UK will be on Digital Radio . The powers that be have new plans for the AM and FM bands , so these guys better be quick . I forgot to mention that to light a torch bulb you would probably need an aerial 100 meters long and 10 meters high .Notice that in the article , they have yet to build a working prototype . Dont scrap those batteries just yet . The other problem , is that to light your torch bulb your receiver has to be exactly tuned to one transmitter . To extract power from all the transmitters available at your location , you would need a separate receiver for each transmitter . In the original article , they talk about powering clocks and remote controls . A clock uses so little energy that if you were to spit on a penny and place it next to a five pence piece you have made a cell that would power your clock for months . A remote uses a bit more energy , especially if like me you spend hours chanell surfing .
