[USMA:48345] RE: Air-conditioning

[Martin Vlietstra]

We are drifting into the "Green" argument here which is outside the remit of
this board.  However noting that the best way to quantify "Green" arguments
by using a single, consistent unit of energy is well within the remit of
this board.

 

  _____  

From: owner-u...@colostate.edu [mailto:owner-u...@colostate.edu] On Behalf
Of Carleton MacDonald
Sent: 09 August 2010 23:10
To: U.S. Metric Association
Subject: [USMA:48344] RE: Air-conditioning

 

True.  But nonetheless if all of that stuff in the house raises the internal
temperature one degree Celsius, that's one fewer degree the furnace has to
work to get the house up to the setting on the thermostat (which in our
house in the winter is 20 degrees Celsius).

 

Carleton

 

From: John M. Steele [mailto:jmsteele9...@sbcglobal.net] 
Sent: Monday, August 09, 2010 07:07
To: carlet...@comcast.net; U.S. Metric Association
Subject: Re: [USMA:48340] RE: Air-conditioning

 

I agree with Martin's response, but the more immediate effect to you is that
you are heating at electricity rates, which are normally much higher than
natural gas or other heating fuel rates.

 

Use the electricity you need to, but the waste heat is a cost-ineffective
offset to heating fuel use in winter and pure waste in the summer.

 

  _____  

From: Carleton MacDonald <carlet...@comcast.net>
To: U.S. Metric Association <usma@colostate.edu>
Sent: Sun, August 8, 2010 9:23:19 PM
Subject: [USMA:48340] RE: Air-conditioning

On the other hand, in winter, wouldn't all that heat mean the furnace has to
run less often?

 

Carleton

 

From: owner-u...@colostate.edu [mailto:owner-u...@colostate.edu] On Behalf
Of Stanislav Jakuba
Sent: Sunday, August 08, 2010 15:34
To: U.S. Metric Association
Subject: [USMA:48339] Air-conditioning

 

Undoubtedly, the USA members on this forum noticed the flood of
air-conditioning energy-consumption news. I responded to one of these. That
Letter to Editor is below, and I am adding a paragraph beneath it for USMA
that addresses SI units.

 

Letter to Editor:

The "How Air Conditioning Is Sapping Our Society" omitted one reason for the
skyrocketing air-conditioning electricity consumption. It is not just the
growing number of air-conditioned homes that contributes to the steep rise,
it is also the higher electricity consumption in homes. And in commercial
buildings for that matter. 

 

As everyone was taught in school, all electricity at home changes into heat.
Thus the electricity consumed by each lightbulb, TV, stove, computer,
freezer, down to the cell-phone charger, heats the building interior thereby
raising the temperature if the walls are not "cooling" such as in hot
weather. More then in the past, these electricity consuming devices are left
on longer such as lights burning during daylight for decorative purposes,
computers and TVs always on (and when off they still consume electricity
unless unplugged), icemakers running at full tilt, dishwashers providing
electrical drying, etc. In commercial buildings, there are more lights, more
computers and devices on 24/7. In supermarkets there are heat blasting
bakeries, cooled food counters, drinking water and soda-fountains, freezers,
etc. whose coolers are not vented outside. The heat the compressors in these
devices generate must also be removed by the main air-conditioners in
addition to their basic load of cooling people, walls and ceiling. It all
adds.

 

Air-conditioners use close to the same amount of electricity for the removal
of heat as is consumed by the individual appliances. To illustrate, it takes
between 50 W to 100 W by the air-conditioning compressor motor, fan and
controls to remove the heat flow a 100 W lightbulb produces. Total power: up
to 200 W. Conversely, a simple turning off (better yet, unplugging)
appliances in the hot, humid weather saves up to twice the amount of
electricity they would consume. 

 

And it is not just air-conditioners that gobble electricity for cooling. Ice
makers are another culprit. About 1 kg of ice is melted/made for every
person in the US daily. If melted inside the home, some of the energy helps
cooling the interior but most of the ice goes "down the drain" cooling the
underground and picnic grounds. I calculated that 2.5 GW is utilized for ice
making in the US. That is more than the capacity of the nuclear power plants
in Connecticut combined. Or, to involve renewables, the power of some 12 500
typical wind mills.

 

Lastly, the misuse of fans. Leaving a 500 W fan on in a closed room when
nobody is there, as is often done in homes, schools, and businesses, is not
cooling it. To the contrary, it is adding 500 W to the room thereby heating
it. It is the evaporation from skin and convection that cools us; the wind
only intensifies it. When there is an air-conditioner on concurrently with
the fan and nothing to evaporate, another 500 W load is added to the
compressor, a total of up to 1 kW more is spinning the meter.

 

USMA members will appreciate this addition:

Many writers of the air-conditioning, energy-consumption analyses illustrate
the numbers on the example of the 100 W lightbulb as above. Then they take
the Btu rating of an air-conditioner and thru convoluted conversions among
various energy and power units provide a number in yet another unit. In the
analyses, they often refer to Btus and omit specifying whether it is Btu per
something such as per hour or minute. Contrasting, the "tons of
refrigeration" is treated as an energy unit. And sometimes units are
invented as if these I-P-units numbers were not hard enough to compare even
if the terminology were unified. 

 

Why, oh why, don't writers recognize that since all (or most) electricity
coming to a house changes to heat, and that both electricity and heat can
and should be measured in the same unit? If they did, one would learn that
to remove 100 W heat flow coming from that lightbulb requires up to 100 W
electricity flow into the air-conditioning unit to power its fans,
compressors, and controls. That would reduce the usual gibberish to the
simple "a 100 W lighbulb, if lit, requires up to 100 W of electrical power
to remove its heat in hot weather." To be a bit more informative, a writer
could add that if the electricity comes from thermal power plants, it takes
300 W of fuel energy flow to power the 100 W lightbulb and consequently 300
W to power the air-conditioner, or 600 W altogether. And perhaps also hint
that a person contributes about 100 W sitting idle. Not much can be done
about the latter load short of going outside, which, come to think of it,
may be healthy as well as frugal. The impact of metabolism is obscured by
the usage of the DV measured in Calories (or calories) in the U.S. so that
nobody can correlate that heat production to cooling without converting. 

Stan Jakuba