Indirect Lighting & Energy Conservation Part 6
5. ENERGY EFFICIENT STREET LIGHTING OF NEXT DECADE:
It is evident that Solar charged LED lighting system is going to dominate the street lighting of green cities in next decade. It will be consisting of following main components.
Panels : High efficiency, poly-crystalline panels will be used in all the Green Street Lighting systems. Sizes can vary depending on the location and the light fitting used. The size and number of the panels are chosen in order that the amount of energy generated in normal applications over the full year is balanced to the energy used in powering the light.. This means that the system generates more power in the summer(when demands on the grid are the highest) and less power is generated in the winter when the surplus energy is “borrowed" back from the grid. This helps balance the energy demands of the power supply and can help reduce peak loads. This can be a significant effect as most energy is generated from the solar panels on bright sunny days which happens to occur when the grid is under it’s highest loading from air-conditioning loads.
In some applications where very high light levels are required, the energy generated may not be sufficient to fully balance energy use. In these cases of
complimentary supply, the benefits of load matching are still achieved and the net energy drain reduced.
Electronics: The electronic system consists of a full sine wave grid interactive 240 VAC inverter for connection in grid interactive solar systems. This inverter is controlled by a monitoring system that both monitors the energy balance of the system, switches on and
off the light system and monitors total system operation.
Light Fitting : A wide range of light fittings can be used to match existing systems or allow standardization with other systems mainly consisting of LED (Light Emitting Diodes).
Photosensitive Switch : It is an electronic device which controls the electrical current. It switches on automatically if luminous intensity is dropped below certain level.
LED’s : LED's are special diodes that emit light when connected in a circuit. They were frequently used as "pilot" lights in electronic appliances to indicate whether the circuit is closed or not. A a clear (or often colored) epoxy case enclosed the heart The two wires extending below the LED epoxy enclosure, or the "bulb" indicate how the LED should be connected into a circuit.
6. CONSTRUCTION DETAILS OF LED’S:
What Causes the LED to Emit Light and What Determines the Color of the Light?
When sufficient voltage is applied to the chip across the leads of the LED, electrons can move easily in only one direction across the junction between the p and n regions. In the p region there are many more positive than negative charges. In the n region the electrons are more numerous than the positive electric charges. When a voltage is applied and the current starts to flow, electrons in the n region have sufficient energy to move across the junction into the p region. Once in the p region the electrons are immediately attracted to the positive charges due to the mutual Coulomb forces of attraction between opposite electric charges. When an electron moves sufficiently close to a positive charge in the p region, the two charges "re-combine".
Each time an electron recombines with a positive charge, electric potential energy is converted into electromagnetic energy. For each recombination of a negative and a positive charge, a quantum of electromagnetic energy is emitted in the form of a photon of light with a frequency characteristic of the semi-conductor material (usually a combination of the chemical elements gallium, arsenic and phosphorus). Only photons in a very narrow frequency range can be emitted by any material. LED's that emit different colors are made of different semi-conductor materials, and require different energies to light them.