The unrestrained combustion of fossil fuels has resulted in vast pollution at the local scale throughout the world, while contributing to global warming at a rate that seriously threatens the stability of many of the world’s ecosystems. There are many applications where heat, not electricity, might be the desired outcome of solar power. For example, in large parts of the world the primary cooking fuel is wood or dung — which produces unhealthy indoor air pollution, and can contribute to deforestation. Solar cooking could alleviate that — and since people often cook while the sun isn’t out, being able to store heat for later use could be a big benefit. Unlike fuels that are burned, this system uses material that can be continually reused. It produces no emissions and nothing gets consumed
Solar photovoltaic (PV) technology is a clean, sustainable and renewable energy conversion technology that can help meet the energy demands of the world’s growing population. Although PV technology is mature with commercial modules obtaining over 20% conversion efficiency there remains considerable opportunities to improve performance. The nearly global access to the solar resource coupled to nanotechnology innovation-driven decreases in the costs of PV, provides a path for a renewable energy source to significantly reduce the adverse anthropogenic impacts of energy use by replacing fossil fuels. Current research explores several approaches to improving PV efficiency with nanotechnology:
- optical enhancement,
- micro-structural optimization for electronic material quality and increasing the spectral response via band-gap engineering.
- nano-antennae being tuned into infrared energy, which is radiated down on us all day by the sun and re-radiated back from the Earth at night. These solar collectors don’t need their beauty sleep like regular solar cells, ach potential efficiencies of up to 80%! They pull overtime, day in and day out if researchers can figure out how to convert the energy into something useful by humans.
- carbon nanotube, which absorb the sun’s heat and store that energy in chemical form, ready to be released again on demand. For applications where heat is the desired output — whether for heating buildings, cooking, or powering heat-based industrial processes — this could provide an opportunity for the expansion of solar power into new realm.
Large-scale utilization of solar-energy resources will require considerable advances in energy-storage technologies to meet ever-increasing global energy demands. Other than liquid fuels, existing energy-storage materials do not provide the requisite combination of high energy density, high stability, easy handling, transportability and low cost. New hybrid solar thermal fuels, composed of photoswitchable molecules on rigid, low-mass nanostructures, transcend the physical limitations of molecular solar thermal fuels by introducing local sterically constrained environments in which interactions between chromophores can be tuned. A hybrid solar thermal fuel can be produced using azobenzene-functionalized carbon nanotubes. On composite bundling, the amount of energy can be stored per azobenzene more than doubles from 58 to 120 kJ mol–1, and the material also maintains robust cyclability and stability. Solar thermal fuels composed of molecule–nanostructure hybrids can exhibit significantly enhanced energy-storage capabilities through the generation of template-enforced steric strain.
The working cycle of a solar thermal fuel is depicted in this illustration, using azobenzene as an example. When such a photoswitchable molecule absorbs a photon of light, it undergoes a structural rearrangement, capturing a portion of the photon’s energy as the energy difference between the two structural states. When the molecule is triggered to switch back to the lower-energy form, it releases that energy difference as heat. The principle is simple: Some molecules, known as photoswitches, can assume either of two different shapes, as if they had a hinge in the middle. Exposing them to sunlight causes them to absorb energy and jump from one configuration to the other, which is then stable for long periods of time.
Nevertheless these photoswitches can be triggered to return to the other configuration by applying a small jolt of heat, light, or electricity — and when they relax, they give off heat. In effect, they behave as rechargeable thermal batteries: taking in energy from the sun, storing it indefinitely, and then releasing it on demand. In order to reach the desired energy density — the amount of energy that can be stored in a given weight or volume of material — it is necessary to pack the molecules very close together, which proved to be more difficult than anticipated.
The interactions between azobenzene molecules on neighboring CNTs make the material work. While previous modeling showed that the packing of azobenzenes on the same CNT would provide only a 30 percent increase in energy storage, the experiments observed a 200 percent increase.
Providing new motivation for researchers to design more and better photochromic compounds and composite materials that optimize the storage of solar energy in chemical bonds, further exploration of materials and manufacturing methods will be needed to create a practical system for production, incorporating Cellular Manufacturing: Mitigating Risk and Uncertainty.
Similarly, while nano-antennae use common ingredients and can be printed on flexible plastics, like bag, covering a sheet of plastic with millions of nano-scale collectors requiring Cellular Manufacturing: to Mitigate Risk and Uncertainty with nano-antennae assembly/installation.
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