Photovoltaics directly convert solar energy into electricity. They work on the principle of photovoltaic effects. When some materials are exposed to light, they absorb the photons and release free electrons. This phenomenon is called the photoelectric effect. The photovoltaic effect is a method of producing direct current electricity based on the principle of the photoelectric effect.
Based on the principle of photovoltaic effect, solar cells or photovoltaic cells are made. They convert sunlight into direct current (DC) power. However, a single photovoltaic cell does not produce enough electricity. Therefore, many photovoltaic cells are mounted on a supporting frame and are connected electrically to each other to make photovoltaic modules or solar panels. Usually, the available solar panels range from several hundred watts (say 100 watts) to some kilowatts (sometimes heard about 5kW solar panels?). They are available in various sizes and different price categories. The solar panels or modules are designed to supply electricity at a certain voltage (say 12V), but those that produce current depends directly on the incident light. So far it is clear that photovoltaic modules produce DC power. But, for most of the time, we require AC power and hence, there is also an inverter in the solar energy system.
As the name suggests, in this type of solar energy system, the rays of the sun are centred (focusing) on a small area by putting a mirror or lens on a large area. Due to this, a large amount of heat is generated in the concentrated area. This heat can be used to heat the working fluid which can then run a steam turbine. There are various types of technologies that are based on solar energy focused on the production of electricity. Some of them are a parabolic pit, sterling dish, solar power tower etc. The following schematic shows how solar power tower works.
The main part of solar power system is the solar panel. Different types of solar panels are available in the market. Solar panels are also known as photovoltaic solar panels. Solar panel or solar module is basically an array of series and parallel connected solar cells. The potential difference developed in the solar cell is approximately 0.5 volts and therefore the desired number of such cells in the series should be added to get 14 to 18 volts to charge a standard 12 volt. Solar panels are connected together to create a solar array. Many panels are connected simultaneously in both parallel and series to obtain parallel and high voltage, respectively.
In the grid-tie solar generation system, the solar modules are directly connected to the inverter, not with the load. The power collected from the solar panel varies, not with a constant rate, but with the intensity of the sun’s light. This is the reason that solar modules or panels do not feed any electrical equipment directly, instead, they feed an inverter whose output is synchronized with the external grid supply. An inverter takes care of the voltage level and the frequency of output power from the solar system always keeps it with the grid power level. As soon as we get strength from both the solar panels and the external grid power supply system, voltage levels and power quality are constant. Since the stand-alone or grid fallback system is not connected to the grid, the difference in any electrical level in the system can directly affect the performance of the electrical equipment it receives.
There should be some means to maintain the system’s voltage level and power supply rate. A battery bank in parallel with this system takes care of this. Here the battery is charged with solar energy and the battery feeds the load directly through it or through an inverter. In this way, due to the variety of sunlight, the solar energy system can be avoided due to change in the quality of electricity, rather than a seamless uniform power supply is maintained. Generally, Deep Cycle Lead Acid Battery is used for this purpose. These batteries are usually designed to enable many charging and discharges during service. Battery sets available in the market are generally 6 volts or 12 volts. Therefore, a range of such series can be added in both series to obtain the current rating of the higher chain and battery system.
It is not desirable to overcharge and discharge the lead-acid battery. Overcharging and discharging can both badly damage the battery system. To avoid these two conditions, a controller is required to attach the system to maintain the flow and flow of the battery.
It is clear that the electricity produced in the solar panel is DC. Electricity from grid supply is AC. Therefore, in order to run common equipment from the solar system along with the grid, it is necessary to install an inverter to convert the DC of the solar system to AC level of the grid supply.