I would like to suggest a somewhat different approach. Photosynthesis is a rather inefficient process. It is my understanding that the energetic efficiency is probably only a few percent - although I will be happy to be corrected in this.
Photo cells for space use probably have an efficiency of ~20 -> 30% and have the issue of radiation degradation. Using LED's to make light for plants is going to reduce the effective efficiency - I will assume that the LED's are ~ 30% efficient, for a net efficency < 10%. The concentrating illumination approach will have probably at least 3 mirrors and 2 windows to deal with as well as occulation by various structural elements. I will simply assume 10% losses per interaction, for a throughput of over 55 %.
But hydrolysis has a reasonable efficiency of over 95%. If you do genetic modification of the plants to consume H2 rather than sunlight, you are likely to get a far higher output efficiency than with photosynthesis. They won't formally be plants, but do you care?
I suspect that LED failure has a significant thermal activation component. If you drive them at lower currents they should live much longer. You don't really care that much about the mass of the LED, it is small, and the photonic efficiency should be a bit higher at the lower drive.
This is an interesting proposal. At least in theory.
In practical terms I suspect there are a number of hurdles. Is it possible to modify plants to consume H2 rather than light? Or, more to the point, has it ever been done? I have never heard about it before. I can understand that it should be theoretically possible since H2 is part of the photosynthesis process. But that is not really the same thing as being practically feasible.
Given the potential payoff, it would be worth a reasonable investment in the molecular genetics research to start seeing how to do it. There are of course engineering issues in terms of implementation - keeping the H2 level below the flammable / explosive threshold in the growing region is an obvious issue.
I do not doubt that there are engineering issues. But flammability need not be one of them. Hydrogen is only explosive when combined with oxygen. And plants do not need oxygen. It should thus be possible to continuously remove all oxygen that the plants produce to create a gas composition almost free from oxygen.
Very intriguing 🤔 design and environment to ponder! It's impressive all the information you present,perspectives and time you have dedicated to you through overview. Thank you for sharing.
I would like to suggest a somewhat different approach. Photosynthesis is a rather inefficient process. It is my understanding that the energetic efficiency is probably only a few percent - although I will be happy to be corrected in this.
Photo cells for space use probably have an efficiency of ~20 -> 30% and have the issue of radiation degradation. Using LED's to make light for plants is going to reduce the effective efficiency - I will assume that the LED's are ~ 30% efficient, for a net efficency < 10%. The concentrating illumination approach will have probably at least 3 mirrors and 2 windows to deal with as well as occulation by various structural elements. I will simply assume 10% losses per interaction, for a throughput of over 55 %.
But hydrolysis has a reasonable efficiency of over 95%. If you do genetic modification of the plants to consume H2 rather than sunlight, you are likely to get a far higher output efficiency than with photosynthesis. They won't formally be plants, but do you care?
I suspect that LED failure has a significant thermal activation component. If you drive them at lower currents they should live much longer. You don't really care that much about the mass of the LED, it is small, and the photonic efficiency should be a bit higher at the lower drive.
This is an interesting proposal. At least in theory.
In practical terms I suspect there are a number of hurdles. Is it possible to modify plants to consume H2 rather than light? Or, more to the point, has it ever been done? I have never heard about it before. I can understand that it should be theoretically possible since H2 is part of the photosynthesis process. But that is not really the same thing as being practically feasible.
At the very least, the idea is intriguing.
Given the potential payoff, it would be worth a reasonable investment in the molecular genetics research to start seeing how to do it. There are of course engineering issues in terms of implementation - keeping the H2 level below the flammable / explosive threshold in the growing region is an obvious issue.
I do not doubt that there are engineering issues. But flammability need not be one of them. Hydrogen is only explosive when combined with oxygen. And plants do not need oxygen. It should thus be possible to continuously remove all oxygen that the plants produce to create a gas composition almost free from oxygen.
Thank you, Anders, I am enjoying this series.
Very intriguing 🤔 design and environment to ponder! It's impressive all the information you present,perspectives and time you have dedicated to you through overview. Thank you for sharing.
Regards,
Ken ✌️