Yesterday I was asked an unusual but intriguing question.
“Could solar power be used to create a lightning bolt like Pokémon’s Pikachu?”
The short answer: Theoretically, Yes – with a big ‘if’ and a ‘but’!
Not an entirely unexpected question in the light of the current popularity of the hit AR mobile game Pokémon Go, in which players use augmented reality (AR) to capture virtual Pokémon in the ‘real’ world.
Science or Fiction?
Being a fictional character, not much can be known for sure about Pikachu and his supernatural ability to hurl lightning, and I’d like to work this out with real science. This won’t be as simple as it first seems.
So let’s first focus on what we do know about Pikachu.
- Pikachu can throw arcs of incapacitating electricity (aka lightning) at will, over several meters through air.
- Pikachu is small and yellow.
Electric eels (Electrophorus Electricus) also have the ability to generate powerful electrical charges as both a defence and attack mechanism. They bio-chemically produce up to 860 Volts at 1 Amp – the strongest organically produced electrical current known, and enough to easily stun or even kill, however certainly not enough energy to hurl lightning.
What is lightning?
Lightning is an electrical spark. Sparks occur when the Voltage is great enough to overcome the electrical resistance of the air between those points, allowing current to flow. In a thunder cloud the voltage occurs as a result of a large difference in electrostatic charge between the cloud and the ground.
Air is immensely, mind bogglingly resistant. A single cubic meter of air has an electrical resistance of around 13 Quadrillion Ohms (13,000,000,000,000,000 Ω), and the more air between our two points, the more resistant the space.
Lightning typically discharges at around 30,000 Amps and 100 Million Volts. This massive build-up of voltage is enough to ionise the air into a super conductive, super-heated plasma many times hotter than the sun. It’s this heating and ionising process that reduces the resistance of the air along the path of the lightning bolt to around 3000 Ohms along which the electrical current flows back and forth until the charge is dissipated and the path cools. This superheating and ionisation is also responsible for the bright streak of light which we call lightning.
The relationship between voltage, current, and resistance is referred to as Ohms Law which states that electrical current is proportional to Voltage and inversely proportional to resistance. Voltage (V) equals Current (I) multiplied by Resistance (R). Ohms law is easiest remembered using the Ohms triangle (see image). The Ohms law triangle demonstrates how to work out any given value from the other two known values by multiplication, or division.
Creating lightning – The Tesla coil
Around 1891 Nikola Tesla invented the tesla coil. An electrical experiment in extremely high voltage pulses at high frequencies. These high frequency pulses can produce electrical sparks similar to that of lightning on a smaller scale – somewhat similar to our little yellow friend Pikachu.
Using two transformer coils, a moderate input voltage with high amps can be stepped up to massive voltage levels at lower amps. The included use of capacitors allows these large voltages to be accumulated over time and discharged when sufficient. The spark gap in the circuit ensures that the circuit is only completed (by a spark, ionising and lowering the resistance of the air across the spark-gap) when the voltage is of a sufficient level to induce the millions of volts in the secondary coil.
The use of the second coil – a tuned double air coil allows output voltages in the order of tens of millions of volts.
It is for this reason that one solar panel could in fact produce a Pikachu level lightning pulse BUT very brief, less than a millisecond , and with a much longer capacitor recharge time.
For the best lightning, these pulses must occur many times per second, ensuring the air stays hot and ionised enough to remain conductive along the lightning’s path, increasing duration, power, and range. This would require the capacitor to be charged at a rapid rate – meaning a larger input power supply.
IF we want to produce the Pikachu style sustained lightning at greater range, many more solar panels could be added, and a larger battery to hold more capacitor refills. The actual number of panels needed? How sunny is it outside?
In any case our 10 million volt machine would be over 6 feet tall, nowhere near as cute as Pikachu, and definitely not as yellow.