Solar Technologies

SOLAR TECHNOLOGIES

There are two major commercially applied electricity generation methods from solar energy. They are 1. Solar photovoltaic (PV) and 2. Solar Thermal. In solar PV method sunlight is directly converted to electricity through photo-voltaic cells. On the other hand, in a solar thermal system a high temperature heat transfer medium will be heated by concentrating sunlight which in turn will be used to generate steam that runs a turbine generating electricity.

PV panel: In this project solar PV based power plant is proposed. There are various kinds of solar PV technologies available in the market; however crystalline silicon PV cell/panel is proved to be reliable and commercially viable. Crystalline silicon PV technology has been used for decades and is proved to be long lasting without significant decrease in performance.

The crystalline silicon PV cells were used in powering the space ships as yearly as 1960s. In this application the cells will be exposed to very high solar radiation and other cosmic radiations (no atmospheric protection) and extreme sub zero temperatures. Failure of space ships has never been reported so far due to crystalline silicon PV failure though they have been used for decades. This application proves their reliability in generating power from sunlight.

There are two types of PV panels. They are mono-crystalline and poly-crystalline panels. The efficiency of Mono-crystalline PV panels is a couple of points higher as compared to poly-crystalline PV panels. However, due to manufacturing limitations mono-crystalline PV panels are 30 to 40 lakhs higher in cost compared poly-crystalline PV panels. Hence, in the current market conditions, poly-crystalline PV panels are preferred over mono-crystalline.

Poly-crystalline PV panels manufactured by ‘CanadianSolar’ will be used for this project. The panels are tested and certified according to international quality standards by industry leading 3rd party test institutions like VDE, TUV, Intertec, JET and others for product reliability, performance and safety. Approximately 6000MW CanadianSolar modules were installed worldwide. The company earned top ranking amongst module manufacturers by industry analysts. CanadianSolar has a very good technical team and after-sale support. The company provides 25 years power performance warranty backed by the world leading insurance companies. The policy is non-cancellable and allows third party bankruptcy rights, protecting investors and banks.

Inverter: Utility scale PV plants are connected to the grid through inverters and other power conditioning units such as transformers. Inverters convert DC power into AC power. In addition, inverters assure that the PV arrays output the maximum power using a technique known as maximum power point (MPP) tracking. PV plant configurations and inverter technologies are illustrated in the following line diagram.

Central Inverters: In this topology one central inverter serves several hundred—and even thousands— PV panels as shown in Figure a. Most of the current utility scale PV plants are usually configured in this method. This topology consisted of PV modules connected in series, forming a string, and subsequently, strings are connected in parallel effectively boosting the voltage and current fed into the MPP central inverter.

String Inverters: As shown in Figure b, each PV string in this topology has its own inverter. Although increasing overall costs, string inverters can increase performance by minimizing mismatch output of individual strings associated with central inverters. In this configuration, MPP tracking occurs at string level.

Module Inverters: This configuration utilizes individual inverters for each module and is shown in Figure c. As such, each individual module is optimized by its own MPP tracking. This topology significantly increases plant costs, and is only economical for small, building roof top systems that are often shaded.

Multi-string Inverters: Similar to the string inverter topology, in this system MPP tracking is done at the string level, but instead of DC/AC-inverters a DC/DC-converter is implemented. The system configuration is shown in Figure 1d. Each string in this topology is optimized by its own MPP tracking via the DC/DC-converters. An adequate number of strings are then connected to an AC/DC-inverter.

Inverters play a key role in PV plants. As such, many different technological concepts exist, each with a unique application. Considering a large utility plant, central inverter topologies are the preferred method. This is attributed to the costs of distributed systems, which can be 60% higher than the cost of centralized inverters. Hence, the proposed solar plant adopts a centralized inverter topology. Central inverters manufactured by ‘ABB or SCHNEIDER’ will be used for this project.

Single-axis Solar Tracking:

The sun’s position in the sky changes with the seasons and the time of day. A solar tracker is a device that optimizes the orientation of a solar collector with respect to the sun. Solar tracking is not a new concept, and the benefits of tracking have been proven theoretically and in situ. Solar trackers are used to align the collection system to maximize energy production. There are two basic types of solar tracking systems, single-axis and dual-axis solar trackers which are generally operated by electric motors.

In single-axis tracking, generally panels will be mounted on structure having their longitudinal axis oriented north-south and rotates east-west. Due to the better orientation of panels towards the sun, the overall solar radiation received by the panels and hence the energy produced by them increases significantly. Studies have shown that there could be as high as 30% gain in the energy generated by single-axis solar tracker mounted panels compared fixed tilt panels. This has been verified by several mega watt scale solar installations across the world. In tropical regions, horizontal single-axis trackers are estimated to generate 25% more energy compared to the fixed systems.

There are many different kinds of solar power plants which can be installed. It is possible to make use of solar power plants in an active and passive manner. A solar power plant is used in an active manner when the energy from the sun is converted directly into a useable form which can be used for powering all kinds of appliances that are present in the house on a normal basis. Passive use of solar energy takes place when houses and buildings have been created in such a manner that they get the maximum exposure to the rays of the sun.

There are many different kinds of solar power plants which are constructed all over the world. They include:

PHOTOVOLTAIC SOLAR ENERGY PLANTS – This is the appropriate substitute for the usual electrical energy which is used in houses for powering electrical appliances. Photovoltaic cells will capture the energy which is generated from the sun and get it converted into electricity. The process of energy conversion is clean and simple and it does not involve injecting any kind of smoke or harmful chemicals into the atmosphere. A lot of companies have decided to have grids containing photovoltaic cells installed on their premises so that they can derive the maximum amount of energy from them and also reduce their dependence on the traditional forms of electrical energy.

SOLAR THERMAL ENERGY PLANTS – A solar thermal energy plant will be used for creating solar generated heaters which can be used for heating water and also as an indoor heating system. Thermal cells will be used to capture the energy which has been generated by the sun and then convert it into heat energy. It is also possible to make use of this energy for cooking purposes and also for drying clothes. Low temperatures can be used for heating water as well as swimming pools. Medium heat is used for heating up the inside of homes as well as office buildings. High temperatures will help in generating the electricity which is needed for everyday uses in homes and offices.