I would love to be able to make a power source for a robot that is as versatile as the digestive system in animals. A biological digestive system takes in raw materials and breaks them down in order to release energy that is stored in the bonds between atoms. If I had unlimited space in my robot I would likely build a combustion chamber that could burn any combustible material in order to generate electricity for the robot. The design would likely be based off of the Hero Steam Engine. The engine is a very simple device that spins as steam is pushed through it.
Obviously the Steam Engine wont work in the robot due to size restrictions so another alternative for power is solar. Solar cells are great but they could be heavy on a humanoid robot once you get enough to charge the battery. This also does not remove the need for a heavy battery all together but it still is another option to consider.The last power source that I have done minor experimentation with is Hydrogen fuel cell technology. Fuel cells can now be build at home thanks to commercially available components. The thing that is important to remember if you are planning on using a fuel cell is that you still need to be able to supply it with a supply of fuel. Hydrogen is the most abundant element in the universe. It also contains more energy per pound than gasoline. Unfortunately Hydrogen usually is already bonded to another element so there needs to be a way to get it in its pure form. This can be done many ways. One way to produce hydrogen gas is through electrolysis. Another way that could be considered is through biological methods.
It would take an algae farm the size of the state of Texas to produce enough hydrogen to supply the energy needs of the whole world. It would take about 25,000 square kilometres to be sufficient to displace gasoline use in the US; this is less than a tenth of the area devoted to growing soya in the US but would equal the size of the state of Vermont, or three times the size of the everglades swamp in Florida, all dedicated to raising this form of algae. - Wikipedia
The big jar of slime you see in the photo above contains algae along with a number of other pond-dwelling organisms. This jar represents a contained ecosystem which survived for two years remaining completely sealed the entire time. The contents would have likely lived longer had I not been negligent and forgot to move it back into the sunlight after cleaning the windows. This shows how robust algae is and how easily it can be cultivated in small containers. I tried growing similar samples in petri dishes with even better success. I can just imagine a robot with a tank of algae on its front standing in the sunlight to help with the production of hydrogen by the algae. This process is perfectly clean and produces no pollutants in the process.
Researchers have found a metabolic switch in algae that allows the primitive plants to produce hydrogen gas - a discovery that could ultimately result in a vast source of cheap, pollution-free fuel. Hydrogen, which can be used as a clean-burning fuel in cars and power plants, is virtually limitless in availability, because it is part of the water molecule. It is a candidate to become the world's primary fuel in coming decades. But until now, it was obtainable in quantity only through relatively expensive extraction procedures involving the electrolysis of water or processing natural gas.Cars already have been developed that run on hydrogen-powered devices known as fuel cells. These vehicles are virtually pollution-free; the only substance emitted from the tailpipe is water vapor. They do not release carbon dioxide or other heat-trapping gases, which are widely considered the primary culprits in global warming. Fuel cells big enough to power electrical generating plants could also be built. “Our long-term goal is to develop strains of algae that we would grow in mass cultures to produce enormous quantities of hydrogen gas,” said Melis. “But at this point, we have to improve the production performance.”
It would take an algae farm the size of the state of Texas to produce enough hydrogen to supply the energy needs of the whole world. It would take about 25,000 square kilometres to be sufficient to displace gasoline use in the US; this is less than a tenth of the area devoted to growing soya in the US but would equal the size of the state of Vermont, or three times the size of the everglades swamp in Florida, all dedicated to raising this form of algae.
"Green algae can produce hydrogen gas, H2, in a process called "biophotolysis" or "photobiological hydrogen production." This process is carried out by photosynthetic enzymes, which split water to obtain electrons, excite these electrons with photons, and eventually use these electrons to reduce 2H+ to H2. The scientific challenge associated with this approach to hydrogen production is that the enzyme that actually releases the hydrogen, called a "reversible hydrogenase", is sensitive to oxygen. The process of photosynthesis, of course, produces oxygen and this normally stops hydrogen production very quickly in green algae. So, to overcome this problem, we are generating O2-tolerant, H2-producing mutants of the green alga Chlamydomonas reinhardtii by various genetic approaches. The ultimate goal of this work is to develop a water-splitting process that will result in a commercial H2-producing system that is cost effective, scalable to large production, non-polluting, and self-sustaining."-Maria Ghirardi