On the subject of “capturing dark energy” (I don’t think this technically captures any energy previously existing), my favorite proposal is to connect distant galaxies together with strings, and use the resulting tension to turn a turbine. In principle your limit would then only be the strength and length of your intergalactic rope.
Another way of acquiring useful energy from dark energy is to place two objects extremely far away from each other and give them a velocity towards each other that is somewhat less than their recessional “velocity”. The two objects will initially be transported away from each other because dark energy is creating new spacetime between them even though relative to spacetime they are moving towards each other. Then, mutual gravitational acceleration gradually increases the velocity of these two objects. The velocity of the two objects towards each other eventually overwhelms the creation of new space by dark energy. Thus, the objects return with a kinetic energy greater than what would be generated by the conversion of gravitational potential energy to kinetic energy alone.
Anders writes about this! p. 783-785 (809-811 in the raw PDF). Unfortunately, even with a carbyne chain (“presumably close to the ultimate limits of molecular matter”) checks “the lost mass-energy from extending the cable will be a factor 1.39×10⁹ larger than the work done by the cable”
On the subject of “capturing dark energy” (I don’t think this technically captures any energy previously existing), my favorite proposal is to connect distant galaxies together with strings, and use the resulting tension to turn a turbine. In principle your limit would then only be the strength and length of your intergalactic rope.
See Mining Energy in an Expanding Universe for what I think is the earliest proposal for this idea.
Another way of acquiring useful energy from dark energy is to place two objects extremely far away from each other and give them a velocity towards each other that is somewhat less than their recessional “velocity”. The two objects will initially be transported away from each other because dark energy is creating new spacetime between them even though relative to spacetime they are moving towards each other. Then, mutual gravitational acceleration gradually increases the velocity of these two objects. The velocity of the two objects towards each other eventually overwhelms the creation of new space by dark energy. Thus, the objects return with a kinetic energy greater than what would be generated by the conversion of gravitational potential energy to kinetic energy alone.
Edit: Typos.
How do you connect a galaxy with a string? I don’t understand.
Anders writes about this! p. 783-785 (809-811 in the raw PDF). Unfortunately, even with a carbyne chain (“presumably close to the ultimate limits of molecular matter”) checks “the lost mass-energy from extending the cable will be a factor 1.39×10⁹ larger than the work done by the cable”
But a galaxy isn’t solid. How do you anchor the galaxy to the chain and vice versa?
¯\(ツ)/¯, but if you could...