How do Solar PV Panels work?
Think Nuclear power is a great idea? Well Solar PV panels are really a great way to usefully collect a good portion of the energy already being form an enormous nuclear fusion reactor i.e. the sun. But what are solar PV panels? How does it work, well let's take a look at a solar cell - the centrally important component of solar power, and ask how does that work?
A solar cell, also called a photovoltaic cell - (where the PV comes from) , is defined as any device that can capture some of the energy of a photon of light, and pass that energy on to a device in the form of electricity. Solar cells are combined in numbers and installed on a panel - hence the term solar pv panels.
Solar cells in solar pv panels use the energy of a photon of light to excite electrons in the solar cell’s semi-conducting material from a non-conductive energy level to a conductive one. What makes this complex is that not all photons are created equal. Solar light arrives as a mixture of different wave lengths and energy levels, and no one semi-conducting material is capable of properly absorbing all of them. This means that to increase the efficiency of capture of solar radiation, solar panels are made of hybrid (“multi-junction”) solar cells that use more than one absorbing material.
Each semi-conducting material has a characteristic “band gap” this gap lies between the electron’s excited and unexcited states. An electron sitting at rest in a solar panel cell cannot be excited into usefulness unless it receives enough solar energy from the photons to jump right over this band gap. Silicon has a nice, achievable band gap, one that can be bridged by a single photon’s-worth of extra energy. This allows silicon to be set nicely - on (conducting) or off (not), as defined by the position of its potentially conductive electrons.
Solar PV Panels - Video
Solar Panels - the future
Solar PV panels have remained relatively static in terms of efficiency over recent years. Real advances in efficiency will have to wait for when a suitably affordable super-material is found that can provide a useful band gap while also beating silicon’s mechanical and electronic properties by a fair margin. Until then, solutions have focused on increasing the functional abilities of silicon-based panels but these solar panels have their limits.
Some of the improvements have included anti-reflective coatings which increase the amount of light absorbed overall, while chemical “doping” of the transistors themselves can improve silicon’s optical abilities. Some solar pv panels setups use mirrors to concentrate as much solar radiation as possible on just a few high-capacity cells at the center. Many are now even designed as light-capture devices, so light that enters gets bounced around internally, forever, until it’s all eventually absorbed.
Heat may also be an increasingly important part of solar panels, since any radiation not electronically absorbed will at least be partially absorbed as raw heat. Using this heat to heat water for showers, or even heat homes directly, could help civilian solar power improve overall efficiency even while electrical super-materials continue to play catch-up.
Even more out-there concepts, like space-based solar power, offer some potential by capturing light before it’s filtered through the Earth’s atmosphere; Japan wants to generate a gigawatt of solar power in space, for instance. The problem is getting the power down to the surface, where it could be useful to human beings. The Japanese initiative looks to use lasers for that purpose, but there’s no telling whether bypassing the atmosphere will prove to be a winning strategy, overall.
Solar cells have been hamstrung by several decades of premature headlines announcing such a winning overall strategy and the oncoming dominance of solar power. The reality is that there will almost certainly never be any such eureka moment in engineering. Solar cell technology will be amended and upgraded until it passes some abstract threshold based on affordability, the state of power storage and transmission technology, and the local annual level of sunlight.
All types of solar power and solar panels will be important to any real attempt to roll out green low carbon power on a large scale. Unless nuclear fusion makes huge leaps forward, or classical nuclear power becomes a whole lot more popular, you can bet that solar panels will be a big part of our energy future.
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