Hi Hugh,

This is handy information for those with some technical understanding
but sadly I suspect the average person finds maths almost
incomprehensible.

This post of yours compares with a new innovation by Woolworths down
here in Tasmania wherein some products have a price tag on the shelf
showing the product's price per 100 grams or per kilogram. It's called
Unit Pricing and it's a good idea.

Being a pensioner with a mathematical background in electronic
engineering design, I've been mentally converting all items of interest
to a cost per kilogram for over a decade. It's a great help in buying
economically and frugally.

I'd like to see something similar applied to electrical products.

Peter


--- In ClimateChangeAction@..., hugh spencer <Hugh@...>
wrote:
>
> 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).
>



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