Without purchasing expensive air-con units, or solar panels - and the associated moutings and electrical paraphernalia, is it possible to create a temperature difference of 10-20 °C using materials one can purchase for less than $1000?
Say you have a glass-roofed courtyard (or conservatory of some kind) and the average outside air temperature in summer is between 30-40 °C. With direct sunlight on the glass roof the internal air temperature could easily reach 50-60 °C. Not a very comfortable environment - I'm sure you'll agree.
I would like to design and build some relatively inexpensive system to maintain the internal air temperature to around 25 °C. With the desert-like conditions outside, there is certainly plenty of solar energy available. In fact, before I buried it, water in the black hosepipe that supplied the shower used to reach scoldingly-hot temperatures (say about 70 °C for example.)
I envisage the solution might involve some arrangement of black water-filled pipes, two sealed reservoirs at different heights, a heat pump, a generator and...??? To be honest I really don't have a clue how I could set this up so as to create the desired temperature difference.
It may also be helpful to note that near the building there is an escarpment with a steep drop of about 20m. I've heard that storing energy by pumping water to a greater height is particularly efficient. I doubt however that the same could be said about a cheap turbine/generator used to generate electrical power as the water descends.
If the most efficient/inexpensive solution happened to involve generating a surplus of electrical power - then this could be utilised in the house and would certainly be an advantage.
(Perhaps I should explain - my parents are planning to retire to their small holiday-home in Sicily next year. I'm hoping to build a temperature-controlled courtyard for them as a surprise retirement gift. Also, a water feature incorporating laminal valve jets of water and a Tesla fountain!)