In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.
Subject: Re: Fusion Reactions
Date: Aug 05, 8:22 pm
Poster: Dave Cooper
On Aug 05, 8:22 pm, Dave Cooper wrote:
>In school we are taught that fusion reactions release a tremendious amount of energy. If you people are doing real fusion, why can't you even get 1W output? I have a certain feeling that my teachers have once again been full of baloney. :)
The following is pimarily for our un-named reader.
It is important to keep ENERGY and POWER separate in our understanding of reactions, whether nuclear or chemical. POWER is RATE of doing work ( either releasing or absorbing energy). ENERGY is the work itself.
Fusion reactions DO release huge amounts of ENERGY and POWER per individual reaction. Let's see how much.
That fusion reactions release huge amounts of energy can be seen in the information given in the other posts.. 4 to 6 Million electron volts (MEV) per reaction. By comparison, chemical reactions typically liberate less than 10 electron volts (EV) of energy per molecule. So,compared to a chemical reaction, the fusion reaction releases something like 400,000 to 600,000 times as much energy per reaction.
We can get an estimate of the POWER produced by dividing the ENERGY by the TIME it takes for the reaction to be completed. Since POWER is the rate of energy production. Chemical reactions are rather fast. Let's use 1 pico sec. (1 ps = 10 ^-12 sec.). Thus, the POWER produced by a 10 EV chemical reaction is 10 EV (Joules per Coulomb) / (10 ^-12 sec). or about (10 ^13) watts for 6.25 x 10 ^18 particles. Per particle, its about 62.5 micro watts.
For a 4 to 6 MEV reaction, happening in the same time frame, the power produced is 400 to 600 thousand times larger, or about 2.5 to 4.0 watts/particle!
So, if a fusor is producing 100k Neutron/sec, it would be tempting to simply multiply watts per reaction by 100k and find the fusor is making hundreds of kilowatts. But because each reaction happens in so short a time, the few hundred thousand that occur each second, still leave mostly emptiness between events, and the average power is just a small fraction of a watt.
So in summary, Nuclear reactions are very powerful compared to chemical reactions. The fusor doesn't produce enough reactions per second to make a lot of power on the average. Your teacher probably was correct and so was your perception of what was said.
Hope this helps.
- Re: Fusion Reactions - Whoops!! - Dave Cooper Aug 06, 0:19 am