Sunday, September 27, 2009

Other “Green” Initiatives – Compact Florescent Light Globes - Part 1

Finally, one of the other most visible changes has been to our sources of light in our households, marketed as a "clean green" technology. But is that marketing just that? Are they all they are hyped up to be? Or is this another piece of clever green spin we have all been led to believe?

Many governments have now legislated that only Compact Florescent style globes may be sold and that the older incandescent are being phased out. Whilst it is true that incandescent bulbs produced large amounts of heat in their production of heat and that that heat is wasted energy there are things about Compact Fluorescent bulbs that the general public is usually unaware. Incandescent bulbs are primarily resistive in nature, which is why they convert electrical energy to light and heat. The larger resistance is also why their power usage is higher than a compact florescent bulb. This type of power is referred to as “Real” power. Compact Fluorescent bulbs by comparison use a combination of resistance and inductance to produce an equivalent amount of light from a lower value of real power. Which is why a 15W Compact Fluorescent bulb is equivalent to a 60W incandescent bulb. This is what the environmental movement concentrate on to demonstrate the improved efficiency.

However, the bit they always fail to mention is the “Reactive” power caused by the inductance of the Compact Fluorescent bulb. The reactive power is still power that is used by the circuit, but instead of being dissipated as heat or light it is stored by the light and returned to the circuit when the circuit is turned off. When combined vectorially with the Real power this is known as Apparent Power. This Apparent power is the largest of the three powers and must be produced by the power station to meet all these needs. So whilst you may be saving wasted heat at your home and therefore money, the CO2 is produced at the power station which is now having to produce the apparent power. In some larger houses, once they are fitted with out with Compact Fluorescent bulb’s they may require an electrician to add some capacitance to their meter-box in order to return what is known as their Power Factor back to the standard of 0.8.

What does all that mean? Well Power factor is a ratio of real power to apparent power. The industry standard says that the ideal power factor is that 80% of the apparent power must be dissipated as real power in the form of light or heat. Too many Compact Fluorescent bulb’s can throw this ratio out by their combined inductive effect and would need some adjusting capacitance fitted to the circuit to balance it out. This is important because if it is not done it can induce harmonic distortion into the system. This is normally only a problem for large factories and warehouses at the moment, but may become more prevalent with the wider introduction of Compact Fluorescent bulb’s. As seen from the linked article above:

The nasty waveform created by CFLs is another thing that is going to come back and bite us on the bum. Any spike waveform means that significant harmonics are added to the mains waveform, and although CFLs are only a small percentage of 'nasty waveform generators' at present, the situation will get a lot worse.

An anecdote on the power factor issue was sent to me ... Apparently a company in the UK installed
a large number of CFLs in a building where the lighting was primarily on one phase. It burnt out the neutral link in the fuse box and caused a small fire! The high peak current of all non-power factor corrected CFLs can cause problems where they are used in large numbers.

This harmonic distortion is but one problem encountered with CFL's.

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