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How PV Solar Plants Work? A Beginners Guide

07.08.2017 — 0

From sun conversion to injection electricity to the grid. Everything you want to know about solar plants in one place.

PV Solar Plant (ground-mounted)

Solar DAO is a closed-end investment fund created on the basis of blockchain technology to finance construction of PV solar plants around the world.

Thanks to Solar DAO, investors with modest budgets will be able to enter the industry and participate in construction, management and capacity expansion of PV solar plants. At moment, Solar DAO is in the middle of its Pre-ICO for tokens that closes on August 31st. Tokens will grant access to the project’s 100% profit through dividends distribution.

As different from many other ambitious startups, Solar DAO business model is firmly rooted in the real economy. The project is about building and managing PV solar plants globally, while continuously expanding their capacity. But how exactly do PV solar pants work? This article will explain.

Generating Energy from the Sun: Photovoltaics

George Porter, the winner of the Nobel Prize of 1967 in chemistry, once said:

I have no doubt that we will be successful in harnessing the sun’s energy. If sunbeams were weapons of war, we would have had solar energy centuries ago

Thankfully, we now live in the age when solar energy is used efficiently, sustainably, and peacefully. The key technology that allows us to use the sun’s energy is solar photovoltaics.

Solar photovoltaics is used to convert sunlight into electricity. Solar photovoltaic cells are made of semiconductor materials (for example, silicon). When exposed to sunlight, the semiconducting material causes electrons in the materials’ atoms to be knocked loose. The electrons that are knocked loose then flow through the material to produce an electric current known as a direct current (DC).

In short, the light separates electrons from atoms to create an electric current.The following picture illustrates the process schematically. Red wavy arrows on the picture represent sunlight, and encircled minuses stand for electrons — negatively charged particles. Red arrows symbolize the direct electric current.

Photo-effect

In physics, this effect is known as photo-effect. The direct current (DC) thus generated can be converted into an alternating current (AC) with the help of a special tool called inverter (more on that below).

What is a PV solar plant?

Photovoltaics is widely used from simple calculators and watches to complex industrial objects. Our concern here are PV solar plants — generating objects (power stations) that directly transforms sunlight into electricity which is then fed into the grid.

PV solar plant are distinguished from other similar generating object by two main features:

  • PV solar plants use photo-effect directly, and do not rely any additional processes or devices (such as warming up the heat-carrying agent, like water in the case of solar thermal plants);
  • PV solar plants do not concentrate energy (for example, by heating the water); they transmit it to the grid.

Any PV solar plant has the following basic structural components (see the picture below):

  1. The solar panels that convert sunlight into electricity, generating a direct current (DC) with voltage up to 1500 V;
  2. The inverter system that transforms direct current (DC) into alternating current (AC);
  3. The monitoring system to control and manage the plant;
  4. Finally, there is an external power grid to which the plant is connected.

PV Solar Plant principle diagram

Power systems that generate power of 500 kW or higher are usually supplemented with step-up transformers for further connection to the grid.

Let’s deal with the PV solar plant’s structure step by step.

Solar Panels

Solar panels constitute the most important element of the whole plant as they convert sunlight into electricity. The construction of solar panels makes use of lead-free, optically transparent, anti-reflective glass, which can withstand the tested shot of an ice ball with 35mm diameter at a speed of 30 m/s.

Solar panels consist of modules which are formed by interconnecting of individual cells.

Depending on the production technology, one can distinguish between the two categories of solar panels.

  1. First, there are crystalline solar panels, usually made of crystalline silicon. Depending on the kind of crystal used, they could be monocrystalline and poly- or multicrystalline. Monocrystalline modules typically are slightly more efficient but relatively more expensive than multi-crystalline silicon modules. However, advancements in technology increasingly narrow down such differences. Solar DAO uses crystalline solar panels, because of their higher performance and durability.
  2. Second, there are also thin-film solar panels, based on a series of films that absorb different parts of light spectrum. These panels are mostly made of amorphous silicon (aSi), cadmium telluride (CdTe), cadmium sulphide (CdS), copper indium (gallium) diselenide. Thin-film solar panels can be applied as flexible films laid over existing surfaces or integrated with building components such as roof tiles.

Supporting Structures

The solar panels are mounted on supporting structures and connected to successive chains. Supporting structures are made from aluminum profiles and stainless steel fasteners.

The most commonly used type is a fixed structure with fixed solar panel installation angle. Fixed supporting structures can be anchor block-based and ballast-based. The former is used in construction of PV solar plants on the ground; the latter allows to integrate solar panels into the office or industrial buildings.

Solar panels are also equipped with **trackers **— devices that track the movement of the sun and thus allow to maximize the energy performance of the plant. Thanks to the trackers, the solar panels can spin around to catch the most of daylight and be more efficient.

Trackers can be based on a** single axis (right side of the picture)** or on the **two axes (right side). **The former can track sun only during the day, while the latter can also take into account the changes in the intensity and angle of the sunlight in different times of the year.

Inverter System

Solar panels are mounted on supporting structures and connected to successive chains.

The chains of the solar panels are connected in groups to the on-grid inverters. The inverters are the “brain” of the whole PV plant. Inverters efficiently convert direct current (DC) from the solar panels into alternate current (AC) and, with the help of a transformer, to increase voltage and transmit electricity to the grid.

Generally, there are three types of inverters (inverter types):

  1. Central inverters with power from .ca 100 kW to several MW. Central inverters are supplied as containers or platforms with built-in step-up transformers, together with combiner boxes to connect the successive chains of the solar panels. One central inverter usually monitors the maximum power of the solar panels. Central inverter systems currently achieve up to 98.6% in performance efficiency.
  2. String inverters are smaller and possess less power, from 10 to 30 kW with 380 V of output voltage. These inverters do not require any special techniques to be installed at the plant, and this is why the use of the string inverters makes the entire process of PV solar plant construction much easier and drives the future operating costs down. However, in terms of performance efficiency string inverters are completely comparable with the central ones, reaching the score of 98.2% — 98.6%.
  3. Conventional string and central solar inverters are connected to multiple modules to create an array that effectively is a single large panel. By contrast, **micro-inverters **convert generation from individual solar PV modules; the output of several micro-inverters is combined and often fed into the electric grid. A primary advantage of micro-inverters is that they isolate and tune the output of individual panels, reducing the effects that shading or failure of any one (or more) module(s) has on the output of an entire array.

Monitoring System

The inverter system is supplemented by a monitoring system, which stores and sends snapshots, containing information about all nodes of the PV plant, every 15 seconds. PV solar plants with a capacity of 15 MW or more are further supplemented by weather stations that helps predict the system’s energy production and possible emergence of contingencies.

The monitoring system controls the working parameters of the entire PV solar plant and its, helps to identify malfunctions and deviations from established patterns, and allows for a better risk management. The monitoring system supplements the inverter system. It collects and stores all operating data from the solar plant’s main components.

The main features of the system are:

  • Real-time monitoring of equipment’s operation
  • Preparation of graphic-based reports
  • Analysis and comparison of individual power system units’ operation
  • Emergency signaling for deviations from the norm and other extreme conditions
  • Interactive diagram display of PVS, including detailed information about component location and enabling navigation and localization of any technical failures
  • Export of monitoring results, publishing of data on a web-server, and printing
  • Access to the monitoring system is usually granted via web browser or mobile app.

The monitoring system helps to keep records of the produced and consumed energy and analyze the plant’s efficiency; identify malfunctions and predict technical failures; plan the maintenance and inventory replacement.

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