The correct terms are "load shifting" or "peak shaving."<p>But, in a way, they are storing energy (thermally) in a similar way to batteries. One could imagine freezing water or condensing ammonia over night using surplus cheap wind energy, and then releasing that stored coldness during the day to cool the building.<p>I think the big objection to calling this a 'battery' is that nobody is suggesting using that stored thermal energy to generate electricity. It's just a way of shifting the electrical demands of the building to a time where there is surplus electricity.