Reply To: turn heat into electricity

[jamesr]

Here’s a few notes to start with…

asymmetric_implosion wrote:
What is pulse power?

Any power source based on releasing the energy as series of short pulses. So for example the internal combustion engine is a pulsed power device, whereas the jet engine is a continuous power device.

Why use it?

Whether we are talking about chemical or nuclear reactions, often the easiest way to get an energy releasing reaction to proceed is to provide a limited amount of fuel, then an initial amount of energy to ignite it and let it burn in a (semi-)uncontrolled manner.

In order to design a system to burn continuously, you need to be able to get the balance of the reaction exactly right, and be able to remove the exhaust products.
Although potentially more efficient overall, it adds a lot of complexity.

In the case of Focus Fusion, the requirements needed to ignite the fuel (temperature & density) are substantially easier to achieve in a pulsed power device.

What are the components of a plasma focus?

– Energy storage – Capacitor bank
– Fuel supply – Decaborane compound of Hydrogen and Boron (enriched to be mostly Boron-11)
– Vacuum chamber – the main reaction vessel, containing:
– central cylindrical anode, with a hollowed out end
– array of surrounding rods at the cathodes.
– diagnostic sensors (pressure, temperature etc.)
– Rogowski coil for extracting energy from the ion beam
– “Onion” – layered shells of foil to extract energy from X-rays
– Vacuum pumps
– Switch gear & trigger mechanisms
– Cooling systems (to keep the anode & other parts within design limits)
– Coil to provide the small magnetic field, seeding the angular momentum of the filaments, improving performance
– Electromagnetic shielding (Faraday cage)
– Radiation shielding (neutron & gamma)
– Power conversion circuits & capacitors – to transform the pulsed output to AC feed suitable for the grid
etc..

What are typical specifications and limitations of these components?

Most of the components are standard off-the-shelf parts, apart from the electrodes themselves and the energy extraction coils & onion – for these its too soon to say.

Is there more than one way to build a plasma focus pulse power system?

The use of the hydrogen boron reaction and the requirement to get to Gigagauss field strengths, constrain the scaling of the device (such as defining the optimum anode length), effectively dictating most of the rest of the design. However there are many details that can vary, such as the number of cathodes, capacitor design etc. that can vary.

Can current technology support a working Fo-Fu power plant?

If & when the scientific feasibility is proven, then there will be a number of engineering challenges to overcome, for the anode cooling, onion design among others. However these, for example, are minor in comparison to the engineering challenges facing the mainstream magnetic and inertial confinement fusion programs at ITER & NIF.

In the bigger picture, considering a Fo-Fu power plant as a collection of 5MW black box generators, then it needs continued investment in the grid infrastructure to move away from the centralised big Gigawatt plants to a more decentralised model.