Solar power plant is based on the conversion of sunlight into electricity, either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaics converts light into electric current using the photoelectric effect.
Photovoltaic Electricity – This method uses photovoltaic cells that absorb the direct sunlight just like the solar cells you see on some calculators.
The array of a photovoltaic power system, or PV system, produces direct current (DC) power which fluctuates with the sunlight’s intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC), through the use of inverters. Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC, the desired frequency/phase.
Many residential PV systems are connected to the grid wherever available, especially in developed countries with large markets. In these grid-connected PV systems, use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight.
On-Grid System :- On-Grid Systems are solar PV systems that only generate power when the utility power grid is available. They must connect to the grid to function. They can send excess power generated back to the grid when you are overproducing so you credit it for later use.
Off Grid System: – These systems allows you to store your solar power in batteries for use when the power grid goes down or if you are not on the grid. Hybrid systems provide power to offset the grid power whenever the sun is shining . It can not be expected to provide power for all your loads since the cost & volume of batteries would be prohibitive.
Solar water heating system (SWHS) is the conversion of sunlight into renewable energy for water heating using a solar thermal collector. Solar water heating systems comprise various technologies that are used worldwide increasingly.
In a “close-coupled” SWH system the storage tank is horizontally mounted immediately above the solar collectors on the roof. No pumping is required as the hot water naturally rises into the tank through thermosyphon flow. In a “pump-circulated” system the storage tank is ground- or floor-mounted and is below the level of the collectors; a circulating pump moves water or heat transfer fluid between the tank and the collectors.
Solar water heaters have two types.
Evacuated Tube Collector: – ETC system works on a simple principal ‘Black body heat absorption principal’. Solar water heaters using vaccum tubes made of borosilicate glass with special coating to absorb the solar energy .Air between the gaps of wo glass tubes is evacuated .it results in high level of vaccum which acts as the best insulation to minimize the heat loss from inner tube .the black coating on the inner tube absorbs the solar energy and transfers it to the water. The water on the upper side of vacuum tube becomes hot and thus lighter ,so it starts moving upwards in the tank. At the same cold water, which is heavy, comes downward from the tank and is stored at the bottom.
Flat Plat Collectors: – FPC Collectors are Covered on the top with 3.2 mm thick textured –toughened glass sheet. Inside flat plate collector systems are specially designed to meet every site and every industry condition. The solar radiation is absorbed by flat plate collectors which consist of an insulated outer aluminium box, there are blackened metallic absorber (selectively coated) sheets with built in channels or riser tubes made from copper to carry water. The absorber absorbs the solar radiation and transfers the heat to the flowing water. In Thermosiphon System Pump is not required for circulation;however a circulation pump is required in a forced flow system.
Solar street lights: Solar street lights are raised light sources which are powered by photovoltaic panels generally mounted on the lighting structure or integrated in the pole itself. The photovoltaic panels charge a rechargeable battery, which powers a fluorescent or LED lamp during the night.
Features of Solar light: Lighting Fixture
LED is usually used as lighting source of modern solar street light, as the LED will provide much higher Lumens with lower energy consumption. The energy consumption of LED fixture is at least 50% lower than HPS fixture which is widely used as lighting source in Traditional street lights. LEDs lack of warm up time also allows for use of motion detectors for additional efficiency gains.
Battery will store the electricity from solar panel during the day and provide energy to the fixture during night. The life cycle of the battery is very important to the lifetime of the light and the capacity of the battery will affect the backup days of the lights. There are usually 2 types of batteries: Gel Cell Deep Cycle Battery and Lead Acid Battery and many more.
Controller is also very important for solar street light. A controller will usually decide to switch on /off charging and lighting. Some modern controllers are programmable so that user can decide the appropriate change of charging, lighting and dimming.
Strong Poles are necessary to all street lights, especially to solar street lights as there are often components mounted on the top of the pole: fixtures, panels and sometimes batteries. However, in some newer designs, the PV panels and all electronics are integrated in the pole itself. Wind resistance is also a factor.
Benefits of Solar Street Light:-
• Solar street lights are independent of the utility grid. Hence, the operation costs are minimized.
• Solar street lights require much less maintenance compared to conventional street lights.
Solar Powered Pump: A solar-powered pump is a pump running on electricity generated by photovoltaic panels or the radiated thermal energy available from collected sunlight as opposed to grid electricity or diesel run water pumps. The operation of solar powered pumps is more economical mainly due to the lower operation and maintenance costs and has less environmental impact than pumps powered by an internal combustion engine (ICE). Solar pumps are useful where grid electricity is unavailable and alternative sources (in particular wind) do not provide sufficient energy.
The solar panels make up most (up to 80%) of the systems cost.The size of the PV-system is directly dependent on the size of the pump, the amount of water that is required (m³/d) and the solar irradiance available.
The purpose of the controller is twofold. Firstly, it matches the output power that the pump receives with the input power available from the solar panels. Secondly, a controller usually provides a low voltage protection, whereby the system is switched off, if the voltage is too low or too high for the operating voltage range of the pump. This increases the lifetime of the pump thus reducing the need for maintenance.
Voltage of the solar pump motors can be AC (alternating current) or DC (direct current). Direct current motors are used for small to medium applications up to about 3 kW rating, and are suitable for applications such as garden fountains, landscaping, drinking water for livestock, or small irrigation projects. Since DC systems tend to have overall higher efficiency levels than AC pumps of a similar size, the costs are reduced as smaller solar panels can be used.
Finally, if an alternating current solar pump is used, an inverter is necessary that changes the direct current from the solar panels into alternating current for the pump. The supported power range of inverters extends from 0.15 to 55 kW and can be used for larger irrigation systems. However, the panel and inverters must be sized accordingly to accommodate the inrush characteristic of an AC motor.