Could We Harness Lightning as an Energy Source?
April showers have given way to... May showers and thunderstorms. With all the electricity in the air, it is natural to ask, "Can I use this stuff to power my hairdryer?" Famous madman genius Nikola Tesla certainly pondered this idea.
Each year about one and-a-half billion lightning flashes occur in our atmosphere. Approximately one in four of these bolts blasts the ground. Some land in Kansas, some strike Buenos Aires and more rain down on the Congo than anywhere else in the world.
Frequency of lightning across the planet (NASA Earth Observatory)
An average bolt of lightning, striking from cloud to ground, contains roughly one billion (1,000,000,000) joules of energy. This is no small amount, enough to power a 60-watt lightbulb for six months plus a forgotten open door refrigerator for a day. In the forms of electricity, light, heat and thunder, this energy is all released by the flash in a matter of milli- or even microseconds. From here let's consider the practical potential of lightning is as a power source.
The average American household (with its 2.59 inhabitants) consumes 41 billion (4.14*10^10) joules each year. If your house ran on lightning alone, it would have to be struck more than 40 times per year! There are 114 million (1.14*10^8) households in America. Multiply these two numbers, and you have 4.72*10^18 joules of energy per year. Every lightning bolt on Earth in one year, captured perfectly with no loss of energy, would contain about 4*10^17 joules of energy. Thus, all the lightning in the entire world could only power 8% of US households. At best.
Could this few percent be realistically used? To answer this, we need to look at the practicalities of capturing and using the energy. First, we can imagine that the United States would probably have to restrict itself to domestic lightning sources. This limits us to about 30 million bolts per year. Now we can only power about 0.6% of our households.
How about the electrical engineering required to transform a lightning flash into a spark in a wall outlet? The greatest challenge here is that all of the lightning's energy is transferred in tiny fractions of a second. This means we must have an incredibly large battery (or capacitor) that can charge up instantly when the lightning strikes, then slowly and steadily let out the bottled up power when asked. Devices with these capabilities are both difficult to produce and very inefficient. Physics tells us that we cannot store and retrieve this energy with 100% efficiency. In fact, we lose the majority of the energy we are converting in nearly every process. Compounding the limited total energy and the difficulty and loss in accessing it, we can barely create a tiny fraction of a percent of the power that we use every day from atmospheric lightning.
Sadly, it is completely, utterly unfeasible to use lightning for electricity. But cheer up, it is still beautiful to watch.