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FreeAire and Free Lunches
Alex Steffen, 8 Apr 08

Clark, in his post today about heat pumps and hot water, wondered aloud about other energy-saving techniques:

Why doesn't my fridge connect to the outside world? In wintertime, there's plenty of cold air for free, just outside my window. In summertime, the hot air from the fridge's air pump gets recirculated into my already-overheated house. Seems like a problem looking for a solution. Any takers?

This, in turn, reminded me of the Freeaire Refrigeration System, which as Blaine wrote, is

"...designed to provide such free cooling for walk-in coolers, freezers and cold storage warehouses. The system utilizes an electronic controller to finely tune the operation of standard refrigeration equipment, and this controller simply monitors the outdoor temperature and desired temperature settings and stops refrigerator evaporator fans when not needed, which also reduces the compressor's refrigeration load. Proper airflow is maintained when the evaporator fans switch off by operating one or more energy-efficient circulating fans.

Roughly half the electricity consumed by a typical convenience store is used for refrigeration. The Freeaire System is designed to save energy year-round by allowing refrigeration equipment for a walk-in cooler or freezer to run only as much as it has to. Once the system is installed, evaporator fans typically operate 50 to 75% less often, and reach-in door heaters operate 90% less frequently. Condensing units also usually experience a 10 to 20% reduction in operations. Moreover, a Freeaire System saving 20,000 kilowatt-hours annually can prevent 40,000 pounds of CO2 from being emitted to the atmosphere.

This, in turn. made me think of smart homes that operate to maximize the utility of natural light and breezes, and of moonlight-sensitive streetlights.

And now, I'll wonder aloud in turn: What other free lunches are out there, waiting to be eaten?

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Airlines are starting to look at using more energy efficient routes, as opposed to the most direct.
(Mind you, they've been looking at this since at least 2002)

Posted by: Tony Fisk on 8 Apr 08

Many commercial coolers have separate controls for the compressor and fans. In colder locales, at least, it is not uncommon for people to turn off the expensive compressor during the winter months.

If we want this sort of thing for home use someone ought to design and patent a standardized hookup so that existing units can be retrofitted into houses where the coils and compressor is moved at least partially outside to take advantage of cooler temperature, and dump excess heat outside.

Posted by: clvrmnky on 9 Apr 08

How much of a free lunch is this? Using the cool outside air for refrigeration seems like a fine idea, but the non-fridge part of the space - home or convenience store - is probably being heated for personal comfort. I'd expect the extracted heat and waste heat from the refrigeration system to contribute to that, so removing that is going to shift some load to the heating system. The energy savings will then be the difference in efficiency between the deliberate heating system and the unintentional heating effect from the refrigeration system.

(I'm pretty sure this is true in a residential setting, where the entire fridge is inside the unit; I haven't worked around retail or commercial fridges enough to know where the waste heat usually ends up)

Posted by: Nathan Williams on 9 Apr 08

Why not the same thing for clothes dryers? In winter, it seems such a waste to vent all that heat to the outside - all you really want to do is vent the moisture from the dryer.

Posted by: Robert on 9 Apr 08

Although decidedly low-tech, many cabins and cottages in Canada use a system such as this. In the colder months, the 'fridge' is simply an uninsulated box that pokes out through the wall of the cabin (the door is insulated). In the summer, a conventional fridge is used.

Posted by: Geoff Glave on 9 Apr 08

Nathan Williams: "removing that (waste heat from the fridge) is going to shift some load to the heating system."

Using heat extracted from food in your fridge (and from the area surrounding the fridge due to poor insulation, opening the door, etc.) is a very inefficient way to heat your house, considering the electrical energy the appliance uses.

Losing the fridge's waste heat to the outdoors is no real loss at all. It's still a net positive energy savings.

This is a fabulous idea that is utterly simple and should've been employed long ago.

Posted by: greensolutions on 9 Apr 08

Reminds me of the "ice ponds" that Theodore Taylor and his students at Princeton investigated.

Essentially, office buildings would use a big pile of snow -- plowed off their parking lots during the winter months and covered with a silvery tarp -- as a heat sink for the building's A/C. The covered snow would last a good part of the summer

Posted by: Stefan Jones on 9 Apr 08

Another free lunch, now being commercialized:

Motion sensors for vending machines. That way, the machine isn't constantly "On," even at 3AM, in case somebody wants to buy a bottle of juice.

Of course, one could question the whole vending machine thing, but this is another example.

Posted by: David Foley on 10 Apr 08

@ Nathan Williams

I don't believe the excess heat has to be pushed outside. Why not just insulate the motor with a set of vents for the colder months that open and let the heat into the house and an extract fan connected to outside for the warmer months?

Vent open, fan off. Heat Stays inside.
Vents closed, fan on. Heat blown outside.

Posted by: Itsumishi on 10 Apr 08

let's talk real money... how about the hundreds of millions wasted on dysfunctional municipal systems every year. These are *your* tax dollars. Surely that's a form of efficiency?

low hanging fruit = park spaces that double as stormwater systems; municipal composting facilities for greenwaste (Seattle has one); porous pavement; LEDs in all public lighting... and so on, ad naseum

Posted by: justus on 10 Apr 08

Robert -
Part of your idea for dryers exists. For a little over $5, you can buy a Heat Economizer Heat Vent . "... Exhausts air out-of-doors in summer. Converts clothes dryer into an extra source of heat [in winter]. Saves energy and humidifies during dry months." I had one when we lived in Chicago, where the heat and humidity was a blessing in the winter. Have to think about whether we should get one for our PNW house.

Posted by: PatF on 11 Apr 08



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