The PV Cell Cell, Module & Array

Introduction to PV Cells The photovoltaic (PV) effect is the phenomenon where an electrical potential is developed between two dissimilar materials with their common junction is illuminated with radiations of photons. The PV Cells is therefore, in essence, a device that converts sunlight (photons) into electricity. The PV effect was discovered by Becquerel in 1839. In 1954, Bell Laboratories produced the first silicon cell.

Introduction to PV Cells Sunlight is composed of photons, or particles of solar energy that contains various amounts of energy corresponding to the different wavelengths of solar spectrum. The electrons present in the valance band absorb energy and, being excited, jump to the conduction band and become free. These highly excited electrons are accelerated into a different material by a built-in potential. This generates an electromotive force, and thus some of the light energy is converted to electric energy.

Difference between Photovoltaic effect and Photoelectric effect In the photoelectric effect, the electrons which are generated entered into the free space whereas in photovoltaic effect, the electrons directly enter another material upon emission. Photovoltaic effect is noted in between a couple of metals which are together with one another inside a solution however photoelectric effect happens inside a cathode ray tube using the involvement of a cathode as well as an anode linked by using an exterior circuit. Photoelectric effect is difficult to produce whereas photovoltaic effect is easy to occur The kinetic energy with the released electrons performs an enormous function in the current that is generated by photoelectric effect as opposed to ,it is not so important in the case of the photovoltaic effect.

Difference between Photovoltaic effect and Photoelectric effect Emission of electrons when a surface is exposed to photons of sufficient energy Creation of potential difference at the junction between two dissimilar metals and production of e.m.f

The PV Cell

PV Modules, Panels & Arrays PV Cells are the most fundamental block of an SPV system. It is usually only a few square inches in size, and produces low power (in the range of mW to 1W). Therefore, a single PV cell cannot be used to produce high power. To obtain high power for supplying large loads, we connect numerous solar cells in series and parallel to obtain a structure called solar module. A group of several such modules are further connected to each other in series or parallel to form solar panel. Several interconnected solar panels form a solar array.

How to mount the modules ? The solar modules can be ground mount (e.g. rooftop) mount on track racks (to track sunlight throughout the day) mount on side of a pole (in traffic signals) mount on top of a pole (in street lights)

How to mount the modules ?

How to mount the modules ?

How To Select The Mounting Structure ? There are four basic types of mount structures: roof/ground, top-of-pole, side-of- pole and tracking mounts, each having their own pros and cons. For example roof mount structures typically keep the wire run distances between the solar array and battery bank or grid-tie inverter to a minimum, which is good. But they may also require roof penetrations in multiple locations, and they require an expensive ground fault protection device On the other hand, ground mounted solar arrays require fairly precise foundation setup, are more susceptible to theft/vandalism and excessive snow accumulation at the bottom of the array.

How To Select The Mounting Structure ? Next are top-of-pole mounts which are relatively easy to install (you sink a 2-6 inch diameter SCH40 steel pole up to 4-6 feet in the ground with concrete). Make sure that the pole is plumb and mount the solar modules and rack on top of the pole. Top-of- pole mounts reduce the risk of theft/vandalism (as compared to a ground mount). They are also a better choice for cold climates because snow slides off easily. Side of pole mounts are easy to install, but are typically used for small numbers of solar modules (1-4) for remote lighting systems where there already is an existing pole to attach them to.

How To Select The Mounting Structure ? Last but not least are the trackers, which increase the daily number of full sun hours and are usually used for solar water pumping applications. Trackers are extremely effective in the summer time when water is needed the most.

Example On Selection Of Mounting Structure In the northern U.S., typical home energy usage peaks in the winter when a tracker mount makes very little difference as compared to any type of fixed mount (roof, ground or top-of-pole). In this situation, having more modules on a less expensive fixed mount will serve you better in the winter than fewer modules on a tracker. However, if you are in the southern U.S. and your energy usage peaks in the summer, then a tracker may be beneficial to match the time of your highest energy consumption with a tracking solar array’s maximum energy output.