During the first two weeks of February I attended an EU sponsored retraining course, which dealt with interesting topics that come under the Hi Tech banner. Three subjects were covered, 3D printing, CCTV installing and the course I took, Energy Harvesting. For me this subject is very interesting one as I am a member of the Green Party and I am interested in saving the planet and also reducing carbon waste. The course wasn’t too far from home and luckily I managed to change the original dates to fit in with plans we have in March.
This started with introductions a little paperwork and then it was down to work. We began with a talk about photovoltaics and how solar panels work.
In 1839, French scientist Edmund Becquerel discovered that certain materials would give off a spark of electricity when struck with sunlight. This photoelectric effect was used in primitive solar cells made of selenium in the late 1800s. In the 1950s, scientists at Bell Labs revisited the technology and, using silicon, produced solar cells that could convert four percent of the energy in sunlight directly to electricity. Within a few years, these photovoltaic (PV) cells were powering spaceships and satellites.
The most important components of a PV cell are two layers of semiconductor material generally composed of silicon crystals. On its own, crystallized silicon is not a very good conductor of electricity, but when impurities are intentionally added—a process called doping—the stage is set for creating an electric current. The bottom layer of the PV cell is usually doped with boron, which bonds with the silicon to facilitate a positive charge (P). The top layer is doped with phosphorus, which bonds with the silicon to facilitate a negative charge (N).The surface between the resulting “p-type” and “n-type” semiconductors is called the P-N junction (see the diagram below). Electron movement at this surface produces an electric field that only allows electrons to flow from the p-type layer to the n-type layer.
When sunlight enters the cell, its energy knocks electrons loose in both layers. Because of the opposite charges of the layers, the electrons want to flow from the n-type layer to the p-type layer, but the electric field at the P-N junction prevents this from happening. The presence of an external circuit, however, provides the necessary path for electrons in the n-type layer to travel to the p-type layer. Extremely thin wires running along the top of the n-type layer provide this external circuit, and the electrons flowing through this circuit provide the cell’s owner with a supply of electricity.
During the rest of the first day I learnt the difference between different Solar Panels and how cells join together to form the main power source. Once that was done I was told how panels combine together to make an even bigger power source, as in a house system or on a solar farm.There are basically two types of solar panel circuits one is for a caravan/mobile home and another for a house or business. We used and drew diagrams to show how they connect together.
Battery Circuit (Caravan/Mobile Home)
Grid Tied Circuit (House/Business)
The reason you have a grid tied system for a house or business is that it is a system which links to the mains to feed excess capacity back to the local mains electrical grid. When insufficient electricity is generated, or the batteries are not fully charged, electricity drawn from the mains grid can make up the shortfall.