Wouldn’t it be wonderful if you could have a gallon jar containing the same stuff that is at the center of the sun? What a source of heat that would be! It is mostly hydrogen, but the atoms have all broken apart into electrons and protons, into a different state called plasma.
It is so highly compressed by the weight of the sun above it that its mass is 0.6 tons. Its temperature is about 27 million degrees (15 million degrees Centigrade). Nuclear reactions keep it that hot by combining two protons to make helium, releasing energy. If scientists could make that “hot plasma bottle” in the laboratory, how much fusion energy would it generate? The answer may surprise you … one watt. What? But a cubic meter is 264 gallons, so a cubic kilometer generates 264 billion watts (264 Gigawatts). And the sun is big! Even the hot dense central core is a thousand trillion cubic kilometers.
That gallon jar of sun-stuff would immediately explode like a bomb! Hydrogen bombs release fusion energy catastrophically, but not by fusing two protons but more efficient fuels: deuterium and tritium, heavy isotopes of hydrogen containing one and two neutrons respectively. Those are the fuels used in our attempts to make controlled fusion reactions on Earth. This is the dream – clean unlimited power with no carbon footprint, not contributing to global climate change and with no radioactive waste problems. It is a dream worth chasing and we have been chasing it for 70 years. Unfortunately, it always seems to be about 30 years away from providing electricity to industry and our homes.
Last month (February) there was hot news – a fusion reaction was kept going for five seconds in a tokamak reactor in Culham, England. One small step closer, but it took months to prepare for those five seconds and generate enough fusion energy to boil about 60 kettles of water. The plasma is not dense, must be ten times hotter than in the sun and kept from touching the vessel with very strong magnetic fields. Dozens of teams are now chasing the fusion dream.
Meanwhile we already have a continuously working fusion reactor a safe 93 million miles away, giving about 1.4 kW/square meter at midday on the equator. It will be part of the answer. One thing is certain – we cannot keep burning fossil fuels for decades for our energy needs.
