Do have a look - this is aimed at Joe and Suzy consumer - I have some
issues..but basically it is good

H






2 Thursday, 30 August 2007

By Peter Seligman

It makes no sense to turn off a light when you leave a room in which an
electric heater has been left on. The power used by the light is
100 watts (W), while a heater typically draws 2000 W.

How big a yardstick is 100 W? Let's assume that we leave a 100 W light
globe on every night for six hours, which adds up to 2200 hours a year.

To calculate the energy used ñ measured in watthours - over the year,
we simply multiply the hours by watts, which in this case is 220 000
watt-hours (Wh). As we know, 'kilo' means 'thousand', so a more
manageable way of expressing this figure is 220 kilowatt-hours (kWh).

To most people, including me, a number like 220 kWh doesn't mean much,
so let's convert it into something familiar - say litres of petrol -
as an energy equivalent.

The best efficiency that can be achieved by burning brown coal to
generate electricity is 25 per cent. This means four times the energy
that comes through your electricity meter or power point is required
to produce the energy you use in your home

Taking the above example: 4 x 220 kWh, or 880 kWh, is required to
produce that amount of electricity. If we go a step further, a litre
of petrol contains about 10 kWh of energy. Thus, the 880 kWh equates
to 88 litres - enough for the average car to drive 880 km, or from
Melbourne to Sydney. That's just to run one light globe each night for
a year!



*The case for shorter showers*

Ready for another surprise?

You turn on the taps and jump into the shower. Letís not ponder over
how long you stay in there, but rather look at how many light-globe-
equivalents of power are used.

An electric hot water service element typically draws around 4800 W.
Translating this into 100 W units (4800/100), we get 48 light-globe-
equivalents.

Now let's look at how quickly that water can be used.

If you showered until the hot water ran out, letís assume it would
take an hour to drain your hot water service. An electric hot water
service generally heats water at night over about five hours. In other
words, while you have the hot water tap running, you are using hot
water five times faster than you are able to re-heat it.

So the hot water going down the drain is the energy equivalent of -
wait for it - 5 x 48 kWh, or 240 light globes.

I suspect that many people might take much shorter showers if they
could see the 240 light globes while the hot water tap was on!




*A closer look at fluorescent lights*

How many of us have heard that fluorescent lights are efficient? While
it's true that fluorescent lights are more efficient than incandescent
lights, the problem is the sheer numbers of lights installed.

A typical one- or two-person office might have four double-tube
fittings. The tubes may be 36 W, but the complete fitting - which
includes a transformer-like object called the ballast - uses closer to
45 W. That's about 90 W for each double-tube fitting, so the office is
using the equivalent of almost four 100 W incandescent light globes

Have you heard the myth that it takes more energy to switch lights on
and off than leave them on? It isn't true. Its origin can be traced to
a time when fluorescent tubes were new, expensive and their life was
shortened by frequent switching. But in terms of energy used by modern
tubes, an hour switched off is an hourís energy saved.

Itís not that fluorescent light tubes are inefficient. In fact, they
are more efficient than compact fluorescent lights (CFLs). The problem
is in the way they are used and overused.

One new Tri-phosphor tube can adequately light a kitchen or small
office. However, boxed lights with diffusers waste a lot of the light.
Newer fittings with reflectors and no diffusers are much better. A
very cheap and simple solution is to take a quarter of the tubes out.
Three new tubes produce the same light output as four of the older type.



*More power myths around the home*

Now to low-voltage downlights, another energy "blind spot". Many
consumers take low voltage to mean low energy, but this is not so.
These lamps not only light small areas, they use a lot of power.
Because of the transformer, each downlight - rated at 50 W - actually
uses about 60 W.

The main problem with these lights, apart from their inherent
inefficiency, is that too many must be installed to get adequate
lighting. It is not uncommon to find six or more in a kitchen - around
400 W.

Fortunately, new compact fluorescent downlight replacements only use about
11
W.



Desktop computers are another power hog. How many of us have a desktop
computer churning away all day, maybe all night too?

Home computers typically use about 120ñ160 W, although this drops to
about half if the monitor switches to standby. Nevertheless, an
average home computer might use 100 W for six hours per day. Think in
terms of that Melbourne - Sydney drive!

The good news is that laptop computers use only about 20 W, even less
on standby. LCD monitors use much less power than the older CRT types.



*Standby power

*You may have heard that some appliances use power all the time, even
when they are switched off. Until recently, appliance designers didn't
worry about this. Electronic control circuits need a fraction of a
watt instead of the many watts they draw, but some modern appliances
use more energy on standby than doing their job.

For example, when our washing machine is on standby - not even
displaying any panel lights - it uses about 5 W, which is 24 x 5 = 120
Wh per day. However, the machine only uses about 50 Wh (not counting
the energy to heat the water) to do a load of washing. Our solution?
Turn it off at the power point.

The sheer numbers of these appliances causes the problem - microwave
ovens, TVs, VCRs, DVD players, all with individual clocks and
displays. A typical house might have 10 such units. So unless it
actually has timesetting functions that you need to program, switch it
off.

Finally, let's look at solar.

A photovoltaic solar panel costs about $10 to provide 1 W when the sun is
shining directly on it; this is its 'peak' power.

However, you also have to take into account varying sun angles,
night-time and weather. For Melbourne or Sydney, the average power is
about one-seventh the panelís peak power. So an average watt costs
about $70. Frames, installation, wiring, etc cost about double that again.

But changing an incandescent globe to a compact fluorescent saves on
average 20 W (80 W saving for, say, six hours out of 24). Cost to make
the change? About $7 replaced 10 times over 20 years ñ say $70.

Compare that to the cost for a solar system to provide an average of
20 W: 20 x $70 = $1400. Or if the government is paying half, about $700.

I hope I havenít depressed you too much but the good news is that the
potential for saving energy around the house really is huge - if you
just understand where that energy is going.

Dr Peter Seligman, a biomedical engineer, was a key member of the
team that developed the Cochlear multiple-channel cochlear implant. A
focus of his work over the past 24 years has been the development and
improvement of speech processors. He is a qualified electrical
engineer, holds 25 patents and has been involved in the design of
photovoltaic solar energy and solar heating systems.


see Part 2 http://www.sciencealert.com.au/features/20082502-16942.html

see Part 3 http://www.sciencealert.com.au/features/20080403-16988-2.html

(you may have to change it to http://www.sciencealert.com.au/features/
and type in Seligman in the search box).