[Greenbuilding] Laundry day on the GB List

[nick pine]

Benjamin Pratt  writes:

> I still have the question of whether an electric condensing dryer would 
> save money over a gas conventional dryer.

Yes, dramatically so :-) An electric condensing dryer might remove 12 pounds 
of water from clothes in 1 hour
with a 100 watt tumbler motor at a cost of 1 cent. Can we condense water out 
in real time with a multi-effect
air-air heat exchanger with no heat storage?

At 80% efficiency, a conventional gas dryer could use 15K Btu (0.15 therms) 
of gas at a cost of 0.15x$2 = 30 cents.
A conventional electric dryer might use 3.5 kWh at a cost of 35 cents.

jfstraube writes:

> If you have an airtight house... then dumping the moisture into the 
> indoors has a high risk of causing moisture damage.

But RT's machine condenses out most of the water. Keep up!.

> Heat Pump condensing drier does use less than 1/3 as much electric energy 
> than does a good gas drier

A COP of 3 would be very poor compared to mere tumbling energy. This is like 
heat pumps for houses,
with very low COPs, compared to thermosyphoning air heaters with heat 
storage and motorized dampers.

Gas-passing is an inefficient substitute for good engineering design.

Nick