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Comment by Gibbon1 | Hacker News Reader

A friend in Arizona mentioned having solar panels and setting the thermostat to 65 degrees between 10am and 5pm. And off after that. Later at night they open the windows and close them in the morning.

They're just using the thermal mass of the house to time shift energy.

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The feasibility of this is completely determined by the insulation and albedo of the house. Working around the thermal inertia of the house is tricky, blasting the AC hard at night is only effective if your house is moderately well insulated or good at not absorbing heat (reflective roof, wall insulation, reflective blinds etc, and by reflective I don't mean tinfoil, I mean like white or bright colored, basically no black or dark). Building elements are remarkably bad at storing heat/coolth since their sensible heat capacity is quite low. There are ways to enhance this effect though by getting building elements that are doped with phase change materials.

Of course the insulation part of the equation is a double-edged sword. You want insulation, but you always want air circulation at a rate conducive to low CO2 levels. Maybe a compromise using something like Sheetrock with extra paraffin, and the whole thing painted Anti-flash white, with air exchange passed through heat exchangers underground.

It would be pretty expensive to maintain though.

In modern homes air tightness and mechanical ventilation are both required by code in many places to deal with the issues you've raised.

Even a crappy insulated house has some thermal lag. Which is what you are playing with.

I think people get confused because a low carbon grid is going to have a different pricing structure than the current one where 'base load' power is cheap at night. The reverse will be true. Power in the evening is going to be spensive. With the cheapest power at noon.

The solution is to time shift demand. A lot of demand can be time shifted. HVAC can be time shifted using thermal lag and storage. You don't really need batteries for that.

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