WORLD OF FIGURES: Investing in modern technology will help save energy cost
A candle is better used as a source of heat than of light. PHOTO | FOTOSEARCH
What you need to know:
- Within our lifetime, the cost of lighting has gone down significantly even though the price of energy has been increasing.
- As energy prices increase, researchers are developing more efficient ways of utilising it.
- And this is not just in lighting: modern cars, for example, are also far more efficient than those that existed in the 1970s.
Ever since humans learnt how to control fire (that is, light it and put it off at will), they have used it for heating and lighting. Unfortunately, while fire is a very good source of heat, it performs dismally in the generation of light. Indeed, even our greatest source of light (the sun) is not a burning object!
Many years ago (2006), I explained in this column that a candle is better used as a source of heat than of light. There are some restaurants (especially those offering Indian cuisine) that use candles to keep the food warm at the client’s table. On many occasions, I have observed a single candle keeping a large bowl of stew boiling for a couple of hours!
A candle generates energy at the rate of about 40W but most of this is in the form of heat. Out of this, it makes only about 12 lumens of light.
Now, even without knowing what a lumen is, it would be good to compare this performance with that of a normal 40W filament light bulb. If you read the specification on the package, you will find that it produces about 450lm. This is about 40 times the brightness of the candle!
The lumen is the unit of measuring the brightness of a light source. It measures the amount of light energy (watts) generated within the visible range of wavelengths of electromagnetic radiation.
The problem with most light sources is that the majority of the energy they emit is not visible by the human eye. Thus, they waste too much.
For example, out of the 40W generated by a candle, only 0.25W comes out as visible light. This is just 0.6 per cent of the total energy!
Compared to candles, filament bulbs are much better — 40 times better! A 40W bulb produces about 9W of light. They are also much cheaper to operate.
There was an interesting study carried out by an economist in the 1990s. He found that the amount of work a person needed to do in order to buy the equivalent of one candle burning for one hour has been dropping.
It turned out that in the prehistoric era, a person needed to work for about 60 hours to make the equivalent one hour of candle light. According to this study, the same amount of work today would buy about 50 years of continuous lighting!
Whether you agree with these results or not, the fact remains that, within our lifetime, the cost of lighting has gone down significantly even though the price of energy has been increasing.
As energy prices increase, researchers are developing more efficient ways of utilising it. And this is not just in lighting: modern cars, for example, are also far more efficient than those that existed in the 1970s.
The lesson here is this: instead of complaining about rising electricity prices and lobbying the government to step in (Serikali Saidia!), it is better to invest in more efficient appliances — starting with light bulbs.
www.figures.co.ke twitter: @mungaikihanya
