Saturday, August 04, 2007

Aluminum over copper for heat transfer?

I've recently been contemplating the connection between energy use and heat transfer.

"Heating and cooling account for about 56% of the energy use in a typical U.S. home, making it the largest energy expense for most homes" according to the US DOE.

If we use more than half of our energy to heat and cool, then our energy problem is basically a heat transfer problem.

When engineers think of heat transfer (and I'm fairly sure only engineers think about heat transfer) they usually think of copper tubing and aluminum plates/fins.

One example close to my heart is solar thermal panels (for heating water) which primarily use copper plates and tubing. There has been a dramatic rise in copper prices, 5-6 times what they were a decade ago, and as a result aluminum (despite its own price rise over the past decade) now offers a 75% better performance on a W/mK/$ basis. Perhaps panel manufacturers are adjusting but I didn't see any indication of this at a recent solar conference. Does anyone know of a manufacturer switching to aluminum? I'm pretty sure heat sinks for computers made the jump to aluminum a long time ago (or never even considered copper).

Usually people select copper for heat transfer applications because it has a high thermal conductivity of 400 W/mk compared to 237 W/mK for Aluminum. But copper now costs three times as much as aluminum on a per pound basis {$3.5 vs $1.2}. Solar panel manufactures (for thermal applications) should switch to aluminum plates and tubing.

Copper has a higher density, so for space constrained/high performance applications it might still win, but for covering large areas, I wouldn't use copper. Am I missing some third factor?

And just in general, have companies that make heating and cooling equipment (like air conditioners/refridgerators) changed to aluminum?


At 6:58 AM, Anonymous Anonymous said...

look at thermodynamics and Bubbling springs solar. thermodynamics are in Canada and BSS is in Wisconsin.

there are several other major manufacturers switching too.

At 10:58 AM, Blogger Daniel said...

I appreciate the tip Anonymous!

Great to see more cost efficient (I assume they still are...I haven't checked either metal lately but I assume both are dropping like rocks) heat transfer systems being deployed.

At 3:48 PM, Anonymous Energias Renovables said...

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