I read an article in the Guardian about the engineer Amory Lovins. He is a passionate advocate for efficiency gains, rather than developing new technology. in this article, he highlighted that a lot of energy is wasted in pipe and duct systems. He argued that if the world used much shorter thicker pipes with more gentle bends, there are large savings to be gained due to the reduction in friction. I imagine he mostly means industrial contexts, but could this argument also apply to domestic contexts? Has this already happened with the use of flexible piping like pEX used instead of copper?

https://www.sustainabilist.com/global-minima/amory-lovins
Video- https://www.cleaningup.live/ep68-amory-lovins-the-einstein-of-energy-efficiency/
Article- https://www.theguardian.com/environment/2022/mar/26/amory-lovins-energy-efficiency-interview-cheapest-safest-cleanest-crisis

Another consideration is that the internal diameter of PEX pipe is 20% smaller (more restrictive) than the equivalent copper pipe, because the copper pipe walls are stronger and thinner. Pumping power is proportional to the fifth power of internal diameter so this makes a big difference:

15mm PEX pipe has internal diameter 11.5mm
15mm copper pipe has internal diameter 13.6mm

Pressure loss comparison = (13.6/11.5)^5 = 2.3
(Edited for turbulence)

So the PEX pipe takes more than twice as much pumping power as the equivalent copper pipe.


Other considerations are that choosing the next size up of pipe will dramatically reduce pumping losses (eg don't use microbore for central heating, use 28mm instead of 22mm, etc)

PEX systems have little inserts you slide into the pipe at the compression fittings, these restrict the bore even more. Copper doesn't need these.

Better insulated homes need less heating so less flow of CH water so less pumping.

Also the power used by a CH pump (10s of W) is pretty negligible compared to the heating load (kW) and it contributes to heating the home.

As electricity becomes renewable, the energy to run the pump has less impact than the emissions/impacts embodied in making the materials. IDK which has the greatest embodied environmental damage PEX or copper.

Edit: if there is no pump, say for hot or cold tap water, then use the smallest pipe you can that gives the flow you want.

Further edit: plumbing systems get modified over the life of the building and you end up with long pipe runs. Eg our place used to have the boiler in the kitchen and a water tank in the loft, both have been replaced in other locations, but the pipes were buried in the walls so somebody just extended them, so pipes now run from kitchen sink to utility room boiler, back to kitchen, up to loft and back down to other side of kitchen, through utility again and into shower room. Takes ages to run hot and pressure is rubbish. Could be avoided if pipes are surface-run for easy modification, rather than threaded though walls and floors.

Thanks for the comments. Any other thoughts on Amory Lovins's work? I like his thought on efficiency, although I think he overeggs its potential to solve climate a bit. It fits in with his anti-nuclear stance. In the video I linked, he states that is a possibility that global net electricity use won't increase as the world electrifies fossil fuel industries. Great mind, but highly wishful thinking.