SOLAR ENERGY

Energie solara

Energia regenerabila ca si sursa de producere a energiei se afla inca la inceputurile existentei. In ultimii 30 de ani ca urmare a scaderii resurselor de energie de tip fosil omenirea s-a orientat catre folosirea surselor regenerabile. Energia solara si cea eoliana sunt si vor continua sa fie surse primordiale de producere a energiei regenerabile. In ziua de azi chiar si problema intermitentei produceri energiei de catre soare si vant a fost rezolvata prin folosirea solutiei de stocare a surplusului produs cu ajutorul bateriilor.
Sistemul fotovoltaic cu conexiune la o retea de energie electrica realizeaza productia de energie electrica si se caracterizeaza prin 3 elemente principale:
- Panouri fotovoltaice
- Invertor
- Linia electrica a retelei
Aceste elemente se completeaza cu o serie de echipamente auxiliare precum sunt protectii împotriva supratensiunilor sau contoare de energie. Un sistem fotovoltaic performant trebuie sa fie compus nu numai din componente de calitate dar si compatibile si deci care se integreaza perfect intr-un sistem.

Panouri fotovoltaice

Panourile fotovoltaice formeaza un generator fotovoltaic si au sarcina de a primi radiatia solara si de a o transforma în energie electrica. Desi pare complicat, panourile/celulele fotovoltaice nu au parti angrenate in miscare si de aceea efortul de intretinere este mic spre inexistent. Ele nu fac zgomot si nu produc poluare - doar energie electrica.

Principiu de functionare a unui panou fotovoltaic:

Un panou fotovoltaic produce energie electrica folosind energia emisa de catre soare. Termenul “fotovoltaic” este obtinut din mariajul a doua cuvinte: ‘photo’ care inseamna lumina, si ‘voltaic’ care se traduce prin electricitate. Responsabila pentru producerea energiei este jonctiunea p-n, ‘inima’ unei celule fotovoltaice. Aceasta jonctiune poate fi formata din acelas tip de semiconductor (incarcat pozitiv la un contact si incarcat negative la celalat contact) sau din doi semiconductori diferirti din care unul este incarcat negativ si celalat pozitiv. Cel mai des folosit material este siliciul aceasta datorandu-se abundentei acestui material dar si a maturitatii industriei electronice care sta in spatele acestui material.
Atunci cand unda luminoasa “loveste” suprafata celulei, pozitia unor electroni se schimba. Acestia lasa in urma niste “goluri” si in felul acesta partea cu exces de electroni se incarca negativ iar partea cu exces de goluri se incarca pozitiv. Intensitatea campul electric care se formeaza in acest mod este direct dependent de intensitatea luminoasa, deci de intensitatea soarelui. Asta nu inseamna ca in zilele noroase nu se produce nimic. Din contra, in zilele cu un strat de nori care nu este prea gros datorita difuziei radiatiei solare cantitatea de energie produsa poate fi apreciabila.

Peste 80% din totalul celulelor solare fabricate in prezent au la baza siliconul un semiconductor utilizat intensiv in industria electronica. Siliconul este elementul chimic cel mai raspandit pe pamant dupa oxigen. Pur si simplu nisipul care ne in inconjoara este transformat prin diferite procese fizico-chimice in materialul folosit la fabricarea celulelor solare. In functie de aceste procese siliconul nativ (nisipul) poate fi transformat in silicon monocristalin sau policristalin. Cel monocristalin este obtinut dintr-un singur monocristal si poate avea culoarea neagra sau albatru inchis. Celule care au la baza acest tip de siliciu monocristalin au eficienta de transformare a energiei solare in energie electrica mai ridicata comparativ cu cele care au la baza siliciu policristalin dar au si un pret de vanzare mai ridicat. Celulele policristaline au culoare albastra, sunt mai usor de produs si, in consecinta, sunt mai ieftine.

What is “the solar energy”?

A solar system generates electricity from sunlight. Although they may look complicated, solar panels have no moving parts and require little or no maintenance. They make no noise and no pollution – just clean, reliable electricity directly from the sun. ‘Photo Voltaic’ is a marriage of two words: ‘photo’, meaning light, and ‘voltaic’, meaning electricity. Photo Voltaic technology, the term used to describe the hardware that converts solar energy into usable power, generates electricity from light. At the heart of photo voltaic (PV) technology is a semi-conductor material which can be adapted to release electrons, the negatively charged particles that form the basis of electricity.
The most common semi-conductor material used in photo voltaic cells is silicon, an element most commonly found in sand. There is no limitation to its availability as a raw material; silicon is the second most abundant material in the earth’s mass. All PV cells have two layers of semi-conductors, one positively charged and one negatively charged. When light shines on the semi-conductor, the electric field across the junction between these two layers causes electricity to flow, generating DC (direct current). The greater the intensity of the light, the greater the flow of electricity. A photo-voltaic system therefore does not need bright sunlight in order to operate. It can also generate electricity on cloudy days. Due to the reflection of sunlight, days with slight cloud can even result in higher energy yields than days with a completely cloudless sky. The solar panels (also called solar modules) are covered in anti-reflective glass and sealed to protect the panels from the atmosphere. As there are no moving parts in solar panels, and only the glass and aluminum frames are exposed to the elements, home solar panels last for decades.
A solar system is comprised of solar panels, the racks for putting the panels on your roof, electrical wiring, and an inverter. An inverter has several jobs.
1 - It converts the Direct Current form the solar panels into Alternating Current, which is what a household or factory is using as power source.
2 - It matches the alternating current to the alternating current (AC) that is coming from the utility grid. Inverters must meet exact standards in order to be approved for use.
3 -The Inverter sends the electricity to the main circuit breaker panel in the building. From there, the electricity can go into the building to run appliances or, if there is more electricity being generated than is being used, it will go back into the utility grid. If permitted by local Net-Metering laws, this will spin your electrical meter backwards... effectively selling power back to the utility.
4 - The inverter ‘watches’ the utility grid so that it can shut down, immediately, if the utility grid shuts down. Solar panels are mounted on a roof and wired together. During daylight hours they generate electricity and send it to your inverter where it then flows into the home or facility to be used by appliances used at residential households and production machines in businesses.