1. Introduction

Global warming, climate change, melting ice caps— these are all events happening in the world that many of us consider small and not important but most of our energy used comes from fossil fuels like petroleum and coal that provide electricity and gas to power our increasing energy needs. These resources are non-renewable which means that we will eventually run out. Most of us take electricity for granted, and we do not realise we are consuming disproportionate amounts of energy.
According to electricity consumption charts, we consume a lot more electricity compared to other countries, which are similar to us. Per capita Singapore used 8404.23 kilowatt hours of electricity and that is the amount of energy produced by burning 723 kilograms of oil.(9) Also, Singapore must import all its crude oil and natural gas. In 2011, Singapore’s total primary energy consumption included approximately 89% from crude oil and petroleum products, 11% from natural gas, and less than 1% from other fuel sources. Final end-users’1 consumption of natural gas rose 15% from 1,256 ktoe in 2012 to 1,442 kilo-tonnes of oil (ktoe) in 2013. The industrial-related sector accounted for 88% (1,272 ktoe) of total final natural gas consumption, while another 6.3% (91 ktoe) was attributed to the commerce & services-related sector. Households consumed 4% (58 ktoe) of natural gas (in the form of town gas) mostly for cooking and water-heating.(10)
There has been enormous hype about new technologies to conserve electricity lately. One of them is the LED bulb. They contain a diode that emits light when sufficient voltage is applied as the electrons recombine with the electron holes to release energy in the form of photons. Several companies that sell these bulbs often state their energy-efficient properties. (there is even an entire magazine dedicated to sharing LED news) Our group was naturally drawn to this and became sceptical about LED properties.(7)(8)
So as to be able to find out the best way to conserve energy, we have decided to carry out this experiment. The type of light bulb we use, greatly affects the amount of electricity consumption for each household, schools and offices. We want to find out which bulb produces the least heat for the most light. Results from such an experiment would teach households which bulbs to really buy if they wanted to save electricity consumption.

1.1 - Research Questions

  1. What is the structure of incandescent lights and how to they function?
Light bulbs have 2 metal contacts at its base, which connect to the ends of an electrical circuit. The metal contacts are attached to two stiff wires, which are attached to a thin metal filament. (usually made of tungsten for its high heat resistance) The filament sits in the middle of the bulb, held up by a glass mount. The wires and the filament are housed in a glass bulb, which is filled with a stable noble gas, such as argon.
When the bulb is hooked up to a power supply, electricity flows from one contact to the other, then through the wires and finally the filament itself. As the electrons pass through the filament, then are constantly colliding into the tungsten atoms that make up the filament. The impact energy excites the tungsten atom, heating it up and gaining energy.
Bound electrons in the vibrating atoms may be boosted temporarily to a higher energy level. When they fall back to their normal levels, the electrons release the extra energy in the form of light photons. However, the light photons released are mostly of the infra-red spectrum, so the tungsten filament needs to be heated to a higher temperature (2200 degrees celsius) to emit light photons of the visible spectrum.(5)

  1. What is the structure of fluorescent lights and how to they function?

The central element in a fluorescent lamp is a sealed glass tube that prevents outside particles from coming in and vice versa. The tube contains a small bit of mercury and a noble gas, typically argon, kept under a very low pressure. The inside of the glass tube is also coated with phosphor powder. The tube has two electrodes, one at each end, which are wired to an electrical circuit.
When the lamp is turned on, an electrical current flows to the electrodes. There is considerable voltage across the electrodes, causing electrons to migrate from one side of the tube to the other. This creates energy, heating some of the mercury in the lamp into a gaseous state. Some moving electrons collide with the gaseous mercury atoms, gaining further energy and become excited, becoming electrons of a higher energy level. When the electrons return to their original energy level, they release light photons.
However, these light photons are of the ultraviolet spectrum, undetectable by human eyes. This is where the phosphor coating comes in. When a photon hits a phosphor atom, one of its electrons jumps to a higher energy level as it heats up. When the phosphor electron returns to its original energy level, it releases light photons, now of the visible spectrum.(4)

3. What is the structure of LED lights and how do they function?

An LED is short for a Light-Emitting Diode. A diode is a simple semiconductor, a material with a varying ability to conduct an electrical current. For LEDs, the conductor material is often aluminium-gallium-arsenide. (AlGaAs) All atoms in  pure AlGaAs bond perfectly to their neighbours, leaving no free electrons to conduct electricity. AlGaAs is modified (doped) by adding certain numbers of atoms into it, changing the perfect balance. A semiconductor with extra electrons is called an N-type material. A semiconductor with extra holes is called a P-type material. Free electrons from the N-type material can move to the holes in the P-type material and vice versa.
A diode consists of a section of N-type material bonded to a section of P-type material, with electrodes on each end. When no voltage is applied, electrons in the N-type portion move to the holes in the P-type portion, creating a neutral space where there is a perfectly balanced charge in the middle. (called a depletion zone) When the zone is wide enough, it prohibits further electron and hole travel between the two opposing zones.
To get rid of the depletion zone, connect the N-type side of the diode to the  negative end of a circuit and the P-type side to the positive end. The free electrons in the N-type material are repelled by the negative electrode and drawn to the positive electrode. When the voltage difference between the electrodes is high enough, the electrons in the depletion zone are boosted out of their holes and begin moving freely again. The depletion zone disappears, and charge moves across the diode. The holes exist at a lower energy level than the electrons. When the holes and free electrons meet after the depletion zone disappears, the electron loses some energy to ‘fall’ into the hole. The remaining energy is released as a light photon, thus producing visible light for us to see.(6)

  1. How much electricity does Singapore use per capita?
The average Singaporean used 8404.23 kilowatt hours of electricity. As such, Singapore as a whole used 4597113810 kilowatt hours of electricity, or 45.9711381 terawatt hours.

2.2 - Hypothesis

LED lights give the highest light-heat ratio. (lux/degrees celsius)(3)

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