Where the Energy Comes From
Material independence needs a power source that does not start with a mine. No route passes that test completely today. This page says what each one gives, and what it still takes out of the ground.
We keep the arithmetic in the open, because energy is the layer where a good story is easiest to tell and hardest to check.
The Test We Apply
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Energy returned
A source has to give back far more energy than it took to build. Published figures for that ratio diverge by method, and the argument between the studies is public, so we read them as a range and name the study rather than quote one number.
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Material per watt
Count the mined tonnes behind every installed watt, and count the storage with it. This is the number that decides whether a route is independence or only a longer supply chain.
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Who can build it
A route that only a state or a single continent can build moves the dependency somewhere else. It does not remove it. We look for what a region can build and repair itself.
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What is left at the end
The panel, the membrane and the fuel all end their working life somewhere. A route that has no honest answer to that question is not finished, whatever it costs per kilowatt hour.
The Routes
Photosynthesis
Biology has captured sunlight for billions of years with no mine, no smelter and no maintenance contract. A leaf builds itself, repairs itself and composts itself. Nothing we manufacture does all three.
The cost is power density. A field of plants collects far less usable energy per square metre than a panel does, so this route carries the chemical layer rather than the electrical one. It feeds the bioreactor, the soil and the material. Photosynthetic coatings in the catalogue already do this on a wall.
Photovoltaic
A solar module is the cheapest electricity human beings have ever built, and it is still a mined and smelted product. Silicon, silver, aluminium and glass all come out of the ground, and the storage behind the panel comes out of the ground twice.
So we treat the panel as a bridge and not as the destination. The open question we track is the cell built only from abundant elements, made at low temperature, and recycled at the end without a furnace. Nobody has finished that cell.
Salt Gradients
Where fresh water meets salt water, there is usable energy. Reverse electrodialysis turns that gradient into current, and the brine left over from desalination is a stronger gradient than the sea itself. Waste becomes the fuel, which is the pattern the whole stack follows.
REDstack has run a pilot on the Afsluitdijk in the Netherlands since 2014. Published figures put the theoretical yield near three quarters of a kilowatt hour per cubic metre, the practical yield near a quarter, and the power density around two watts per square metre of membrane. The membranes are industrial products, so this route moves the mine rather than closing it.
Thorium Fission
Energy density is the strongest argument in physics. A thorium fuel cycle returns much more energy than it consumes, produces waste that stays dangerous for centuries rather than for millennia, and uses a fuel that is common in the crust.
It is more sustainable than most of what it would replace. It is not independence. Mining, fuel chemistry, licensing and a specialist supply chain sit behind every reactor, and today only a state can carry them. We call that an honest improvement, not an answer.
Molecular Manufacture
The long answer is to build the collecting surface atom by atom, out of abundant elements, at ordinary temperature. That is what a leaf already does, and it is what nanomechanics promises to do on purpose and at a chosen scale.
This does not exist yet, and we will not pretend otherwise. We name it because it is the direction that the first four routes are travelling in, and because a plan that stops at better panels has not understood the problem.
A source that starts with a mine is a bridge, not a destination.
We use what works today and we say what it costs. Panels and reactors buy the time. Biology and salt point at the shape of the finished thing.
Sources: REDstack on the Afsluitdijk pilot, and the public disagreement between Weissbach and colleagues in 2013 and the rebuttals that followed, which is why this page gives no single ratio.