Units of Energy

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Permalink Reply by Alun James on June 9, 2008 at 10:34

Lets start. A kilowatt is a "rate" of energy use - in the same way that a kilometre per hour (kph) is a rate of movement. Neither of them are "quantities".

If you burn a kilowatt for 1 hour then you will have used 1 kW-h (kilowatt hour)

If you travel at 10 kilometres per hour (kph) for 1 hour then you will have travelled 10 kilometres (km).

Also it would be useful to understand the multipliers - micro (1 millionth or 0.000001), milli (1 thousandth or 0.001), centi (1 hundredth or 0.01), kilo (1 thousand times or 1000), mega (1 million times or 1000000), giga (1 billion times or 1000000000) and the biggest a "normal person" might see is tera (1 trillion times or 1000000000000)

Appliances have energy ratings; a light bulb - 40W, a microwave 1000W (1kW), a tumble drier 2500W (2.5kW) an HSV Holden Commodore 300,000W or 300 kW a small Hydro Power Station 2,000,000W or 2MW.

Questions anyone?

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Permalink Reply by Tim Jones on June 10, 2008 at 23:50

Thanks for this offer, Alun. I have a related question: As of Dec 2007, oil production from the Tui field represented about 2/3 of our oil imports. However, we export almost all of the oil produced in NZ (according to figures in the New Zealand Energy Quarterly, Dec 2007). Two questions:

1) Is this purely because, being high-quality light sweet crude, NZ oil can be sold at a premium offshore, or are there also technical factors which make it hard to refine in NZ?

2) If there are technical reasons why NZ-produced oil is not refined at Marsden Point, how long would it take, if circumstances dictated this be done, to make Marsden Point able to refine oil from the Tui field and other NZ fields?

Finally, just to tie this back to units, Ministry of Energy publications commonly express energy in petajoules (PJ), so you might want to add a definition of this to your list.

Regards
Tim Jones

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Permalink Reply by Alun James on June 11, 2008 at 10:20

Thanks Tim, I sense a bigger issue in your comments.

It is my understanding that the light sweet crude from NZ fields commands a premium in the international market. Technically there would be nothing (I guess) stopping NZRC from processing it other than a willingness on the part of the NZ public to pay for the diesel / petrol that came from such a high quality feedstock.

With the transition towns movement it is important that we focus on our need to reduce consumption - the cost of petrol / diesel does not matter if you do not need it.

For those people focussed on macro energy use / trading a PJ (Petajoule) is 1000 Terajoules or 1 x 10e15 or 1,000,000,000,000,000.

Be aware, these are big numbers for normal people, but just like the newly minted Zimbabwean $50,000,000 note there is 26.5 Megajoules (26,500,000 joules) in a litre of LPG and about 18 litres in a gas bottle. So 477 MJ or almost 0.5 GJ in a gas bottle that you will use over a few summer BBQ's.

Also 1 kW-h is 3.6 MJ. So very simply - 1 litre of LPG will run a 1 kW (nominally 1 bar) heater for 7.4 hours.

If these numbers need more relevance with petrol there are about 33 MJ per litre, lets say a normal fill is 50 litres so we have 1650 MJ per fill, this is 1.650 GJ or 0.00165 TJ or 0.00000165 PJ.

Strangely, this looks like a small number. I'll finish with a couple of cliches.

Death by a thousand cuts - Mind the pennies and the pounds will look after themselves.

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Permalink Reply by Tim Jones on June 12, 2008 at 0:35

Dear Alun,

I completely agree that we need to reduce consumption - but my question related to the possible of a sudden cessation of/severe reduction in supplies (e.g. in the event of a new Middle East war), and whether, in this case, it was technically possible to use NZ crude to substitute for missing imported crude.

Tui, like every other field, is finite, so I certainly do not regard this as a long-term "solution" to anything!

Regards
Tim

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Permalink Reply by Alun James on June 12, 2008 at 13:36

All good then.

The rate we are finding energy (Tui, Maari, Pohokura, Southern Basin) at the moment (in NZ) makes this all seem a bit silly. Ultimately though the world WILL run out of fossil hydrocarbon sources.

Have a look at www.crownminerals.govt.nz to see what I mean.

I have for the last month though been using a Centameter loaned out from work, it is really scary to see how much energy we take for granted. The Centameter is very easy to use and very "revealing" - especially when the boys have left the heat lamps on in the bathroom.

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Permalink Reply by Jenese on June 12, 2008 at 22:34

Hi Alun

first off, those kilo watts and hour just does my head in - I confess I am one of those who simply cannot get my mind to work round things like this - however I do have a question - don't know if anyone could ever answer it though *smile*

how much power does the CBD use at night to light up empty office buildings - I guess I could pick the biggest city Akld - and then the thought occurs to me how much electricity does the sky tower alone burn with all those flashing games ? and then It occurs to me - is it known how much electricity usage NZ uses as a whole - we know roughly how many barrels of oil we use, so in the same way can our electricity usage be known - even per region

this might be right out of your league, but .....well.....I've been wondering about it

I mention this because of the call for domestic users to cut power as well as the threat to domestic power now that we are really heading into seriously cold weather - I live in the south Island - Nelson

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Permalink Reply by Alun James on June 13, 2008 at 9:30

Jenese, it will never be possible to do a snapshot of Aucklands (for example) power use. So build it up from first principles (and some statistics).

I work in a modestly sized office building that holds some 300 staff. It has 9 floors, my floor has 70 fluorescent tube units on it, each of which holds 2 elements. Each element is approximately 35 Watts.

So, we have 4900 Watts or 4.9 kW per floor (for lighting). Multiply that by 9 and you get 44.1 kW for the building for overhead lighting.

Those 300 people all have PC's and those PC's all use about 400W so that comes to 120 kW for desktop computing.

Our office has 25 servers all using about 500W so there is another 12.5 kW.

Each floor has 7 airconditioning units (older building) and I don't know what their power use is so this is drawing to a close...

But you see where I am heading...just build it up one bulb at a time.

So for lighting and computing, during work hours we are using 176.6 kW, if you very roughly halved that for 16 hours a day (when people are not working), we end up with 176.6 kW x 8 hours equals 1412.8 kW-h PLUS for the night 176.6 kW / 2 *16 hours also equals 1412.8 kW-h

So for a full working day the building (roughly) for lighting and computing uses 2825.6 kW-h.

The biggest issue with power use is apathy. One person says I can't make a difference (which is automatically rubbish) but if 300 people say they are willing to commit to giving it a shot then just like the light bulbs which are death by a thousand cuts. Groups of individuals getting on board is life by a thousand plasters.

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Permalink Reply by Thomas Everth on June 17, 2008 at 20:13

Hi Alun!

The PC usage data you mention seem a bit high. The nominal capacity of the power supplies is as you state it here but when you actually measure them with a power meter I got less than half this as the actual consumption when running, but still about 10Watt when turned off but plugged in. Nevertheless the power used in our IT hungry world is staggering.
This site: http://uclue.com/index.php?xq=724 estimates that the Internet and all its uses take abut 6% of global electricity generation to run.

Thomas

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Permalink Reply by Thomas Everth on June 17, 2008 at 20:16

However, on second thought, the Internet has also the potential to save a lot of energy by allowing to work from home. Overall the Internet is probably saving energy and also enabling change to propagate much faster. The TT network is a good example.

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Permalink Reply by Alun James on June 23, 2008 at 14:31

Thomas, have you seen www.blackle.com ?

Not sure that the science is all good behind it but the mindset is right.

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