Score76

I have a calcada driveway currently, it's on a bit of a hill, anytime it rains heavy I spend a few hours in the days that follow resetting the stones as the rain washes away the sand from in between the stones. Visitors who turn round at the bottom of the drive will insist on dry steering too which also loosens them. My thinking, do something different...

Tarmac/asphalt drive, water will run over the top, more tolerant to dry steering, it'll look nicer, the calçada been down 20 years and is looking tired. It's approximately 400sqm.

I then had the idea, could it be used as solar pool heating? I've seen plenty of driveways in the US having electric elements buried under them as they're made so they can be easily de-iced in the winter. Essentially I'm talking about doing the same thing in reverse, burying pipe under the asphalt and diverting the pool water through it when it's sunny on it's way from the output of the filter back to the jets. Sun heats the tarmac, nice n black, tarmac turns sun to heat, water flows through the pipe getting warm as it goes, warm water returns to pool. Running costs would be nothing, my pool pump already runs on solar PV, way cheaper than the 30€ per day (ish) to run the heat pump. Struggling to find a non-insulated pipe that will stand the high temperature of having hot asphalt layed onto it but aside from that, anyone any thoughts as to whether it'll work?

I've attached a few photos to illustrate what I mean. These are all under drive heating, I can't find anyone using it as a solar collector.

BillBullock

Why bother with tarmac? Experiment with black irrigation pipework lying in the sun and see if that satisfies your needs.

Score76

How does that solve the first issue of replacing my calcada drive?

Moses2013

Personally I don't see that working and there have been people who tried it many years ago in the US, but the overall costs were too high. As soon as you put something under your driveway means you have to dig it all up when something goes wrong and the heat generated wouldn't be better than a economic heat pump. There are these heating mats but don't know if they are any good.
https://www.poolpro.co.uk/intex-pool...ating-mat.html

BillBullock

It doesn't of course but it gives you warm water. Around here, most of my friends are happy with their calcadas even on slopping ground.

coleio

I think it is a good idea BUT the construction of a "tarmac" driveway needs first digging out then filling with whatever the base you'll be using to support the weight of any traffic with the tarmac sealing layer on top or it'll crack and break producing notorious potholes.

https://www.pavingexpert.com/tarmac02

This means the water heating pipes need to be in the base or on a hot day with traffic they probably get squashed as hot "tarmac" will gradually move. Maybe, if you can get some pipework cheaply you could try putting in a couple of dozen loops then if one leaks just blank it off and use the ones which don't. Could also put a couple of small virtual pipes to check the temperature at different depths in the driveway on a hot day - all useful information.

liveaboard

It will work in summer, but I think in winter the black tarmac will radiate heat away as quickly as it soaks it up.
Unless anyone has done it and can report otherwise, I'd leave out the heat tubes.