Basic Information
Solar Fuel is a hypothetical burnable liquid or gas created by some sort of chemical or biological process which stores the energy of sunlight. It is a current area of technological research.
Remarkable amounts of solar energy reach the earth every day. Currently, more solar energy beams to the earth every single hour than our entire species uses in a year. Most of this energy is wasted or reflected. Some of it is used by plants in the process of photosynthesis. A solar fuel may use a process similar to photosynthesis to store that energy, but would be likely to be many times more efficient and potent because it could be engineered for optimal results, instead of the more hap-hazard random chance employed by evolution and natural selection. If we can figure out how to make a truly effective solar fuel, it is likely to solve the energy crisis and usher us across the Kardashev Cusp (from Type 0 to Type I on the Kardashev Scale). If that fuel also turns out to be clean-burning, it may provide a means to overcome or stall climate change. If it's not clean-burning, then it wouldn't help with global warming, but might at least take some of the sting out of the coming peak oil crisis.
One current limit to solar power is that it's only available at certain times of day. There's no light shining on the dark side of the planet at night. Solar panels can generate a lot of energy during the day, but then "go dark" in the evening.1 Currently, we can use batteries to store any excess day-time energy for access later when it's dark out. Batteries do the job, but they aren't terribly efficient, and they tend to be heavy. They work better for smaller devices, or stationary installations. A solar fuel, on the other hand, would theoretically be great for devices and situations where the ratio of energy to mass is important — such as aircraft and spaceship design. Accelerating mass to escape velocity is expensive and energy-demanding. The more fuel you choose to carry aboard a spacecraft, the bigger the fuel tank you need, and thus the more fuel you have to burn to get off-world. Being able to create or energize solar fuel after breaking orbit could be very beneficial. Presumably, with the right infrastructure, an array of solar fuel generating platforms could be dropped in convenient places to serve as "filling stations in space" … or at least surrogate oil rigs. Enough of these and you are starting to look like the creator of a Dyson swarm.
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Game and Story Use
- Solar fuel might be developed instead of, or in tandem with improvements in battery technology. So you might have a setting where solar-fuel is used extensively, or one where it is only utilized for high-performance machines, high-velocity vehicles, or even just for space exploration.
- Being inspired by photosynthesis, solar fuel technology could have cool biotech flavor/theming.
- You might have a living organic or cyborg space ship or airplane.
- A starliner might have giant (but very thin) "leaves" that work as both a solar sail and solar fuel refinery simultaneously.
- Using solar electricity to split water for hydrogen is probably a starting point - the process itself is not all that efficient with modern technology and hydrogen is not straightforward material to work with, but a more efficient generation process, improved handling and more efficient regeneration could do a lot.
- Hydrogen fuel cell technology is well on its way - for static plant, where safe handling of hydrogen is less tricky, this may be an effective solution at industrial levels.
- The BattleTech universe features CSF (concentrated synthetic fuel) - a flammable liquid used as a stand in for modern gasoline and equivalents. What it is and how it is produced has been handwaved to date, possibly because none of the characters who have appeared know or care about these details, possibly because it is a generic term for a variety of substances. In theory, however, a synthetic hydrocarbon would be a potentially useful source of energy dense fuel.