Mining for Photons
Tons of Energy, Hard to Get
The earth is basically a giant ball of heat energy with a thin layer of insulation on its outside. There is enough energy there to power any conceivable scale of human civilization, but extracting and converting it is not easy.
Piping Heat with Fluids
The most common way to use geothermal energy is to pipe it out in the form of super heated water or isobutane. Heat energy is converted into useful energy with a turbine engine, and the liquid is recirculated. It takes quite a lot of plumbing. It requires wells that are deep but not too deep. It often requires hydraulic fracturing to improve the surface area of a well series at a given temperature.
Solar Cells are MUCH Nicer (than any thing else!)
The cleanest most hassle free form of energy harvesting known to humankind is achieved with solar panels. Put the photovoltaic in the sun, connect its wires, leave it alone. Photons from the sun encounter the panel and are converted into electrical energy, which we use.
Light from Underground
That deep underground heat energy within the earth can also be thought of as a powerful source of light, of photonic energy. Hot rock emits infrared light. Very hot rock emits very VERY bright infrared light.
There are, in fact, thermal photovoltaics that can convert this color of light directly into electricity. There are problems, though, with trying to use them deep beneath the earth; their efficiency drops to nearly zero as their temperature approaches that of the ambient rock. It is also very difficult to direct that infrared light upward to the surface. Most materials, even very reflective materials, will absorb infrared light. Combined with the problem of needing to concentrate it at depth then send it up a ten cm diameter tube measuring many kilometers in height, and it is too lossy to be practical.
Microwave energy, on the other hand, can travel through pipes with near lossless efficiency. Microwave conduits have been used for decades to transmit data and in some cases power over long distances for specialty applications.
Here's how a Photon Mine Would Work:
A practical approach to mining photons from deep hot rock would consist of a deep hole. Deeper and hotter, I might add, than any current mechanical drilling equipment can facilitate. The most likely approach to reaching glowing hot rock (in the temperature range of 1100˚F to 2500˚F) is to cut the stone with a down-bore laser system.
Into the glowing hot rock, one would install a thermal-pumped maser. (Masers are like lasers, except they shine microwave energy.) The maser would consist of multiple layers of some form of metamaterial staggered with empty space. The outer wall of the maser would be heated by the walls of the bore. The inner space would be a nearly empty column into which small antennae protrude. This keen little device would convert the intense heat radiation into a coherent beam of microwave energy, which travels to the surface through a conduit.
At the surface, the microwave energy is efficiently received with a specially cut antenna and radio system, which converts it to alternating current that can be fed into the power grid.
Each one of these steps presents a significant challenge to today's state of the art works of engineering. Here's a bullet pointed list of the things needed to invent before photon mining could be practical:
- ultra-deep laser stone drilling
- high powered Infrared-Pumped Maser in a pipe
- microwave power receivers for grid tied power
Here are the advantages of using a system like this, as compared to the fluid-circulation approach that is standard for current geothermal power applications:
- Solid state performance, no moving parts
- Nearly direct electrical output, no turbine engine
- No fluid flow or pressure hazards
- No need for hydraulic fracturing because of ultra high temperatures in vertical shaft
- Small surface footprint, no steam cooling towers, suitable for in-town use
- Easy to control power output without risks to system
- Low cost to maintain
You have my permission to start working on making one of these! ;-)