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The European Commission has banned the sale of powerful vacuum cleaners. Now it might do the same for other domestic appliances, but would this actually cut energy consumption?
It started with vacuum cleaners. Then there were howls of outrage when it emerged the European Commission has set up a working group ( http://www.bbc.co.uk/news/business-29004060 ) to look at whether other common household appliances - kettles, toasters, bread makers and hairdryers among them - should also be regulated.
The working group ( http://www.ecodesign-wp3.eu/sites/default/files/Ecodesign%20WP3_Draft_Task_3_report_11072014.pdf [PDF]) is at an early stage and may rule out many of the products. But is the premise correct - does the power of an appliance determine energy consumption? Or by halving the wattage do you simply mean that someone uses it for twice as long ?
(Score: 2) by hankwang on Wednesday September 03 2014, @10:10PM
My dehumidifier is 200 W in current draw. I think the heat-pump capacity is closer to 800 W (coefficient of performance = 4, typical for a compressor-based heat pump).
I have a Peltier-powered icebox and professionally I have designed a temperature controller based on Peltier cooling. From experience with both of them I can tell you that the efficiency of thermoelectric heat transport is ridiculously bad if it has to be over a substantial temperature differential, say 20 C or more. At that temperature difference, your 150 W Peltier module will suck about 50 W of heat out of the cold side (CoP=0.33) and dump 200 W on the hot side. With 50 W of cooling power, it will not be able to dehumidify a substantial volume of air. You are not going to replace a 1500 W hair dryer by that thing.
And then you still need to move the heat into and out of the Peltier module, which will typically involve big expensive metal heat exchangers and which will lower the efficiency even more, a power supply that can deliver 15 A at 10 V or so, a fan, and so on.
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(Score: 2) by evilviper on Thursday September 04 2014, @02:15AM
It will do far, far better than a resistive heating element, which has no cooling capacity at all.
...I can get 10 of them, no problem. But matching your humidifier would only take about 3-4, which is reasonable. And that's without discussing how much those higher-speed fans are going to improve drying with less heating.
A chunk of aluminum is NOT expensive. You can get ridiculously inexpensive heatsinks quite easily.
Thanks largely to computers, those are widely available, in very high efficiencies, at pretty low prices.
But my point was really more to illustrate the ridiculousness of your previous comment... Obviously, a hair dryer doesn't need to be a super-efficient, 50,000 hour duty-cycle dehumidifier built like a tank. There are plenty of ways to shrink the cycle down to a reasonable size.
Hydrogen cyanide is a delicious and necessary part of the human diet.
(Score: 2) by hankwang on Thursday September 04 2014, @07:05AM
On the one hand, you state that a single Peltier module with power supply is cheap, then you state that you need four of them. With $40 for the Peltier modules, and another $50 for a chunky 600 W power supply, more for heat sinks and fans, you still end up with a monstruously big and expensive hair dryer that will need a condensation catch tray and that will merely replace a 750 W resistive hair dryer.
Thermoelectric heat pumps are only useful in certain niche applications: heat transport against small (10 C) temperature differentials in tight spaces and applications where lack of moving parts or accuracy are more important than efficiency. A hair dryer is neither of them.
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(Score: 2) by evilviper on Thursday September 04 2014, @07:32AM
"But my point was really more to illustrate the ridiculousness of your previous comment... Obviously, a hair dryer doesn't need to be a super-efficient, 50,000 hour duty-cycle dehumidifier built like a tank. There are plenty of ways to shrink the cycle down to a reasonable size."
Hydrogen cyanide is a delicious and necessary part of the human diet.