[cgdcraig]

Cold energy storage has always had the problem of utilization and capital cost. You need to buy the storage system and then that storage system may only be useful for 3-6 months of the year during 6 hours of the day. From a thermal efficiency perspective they're great but in general they get offed by the economics. For the price you'd end up gettinf better value off a battery storage system to do load shifting.

[dragontamer]

Ice storage seems uneconomical. But chilled water (40F / 5C) is reasonable.

If you see it from a total-cost-of-ownership, the chilled-water + air conditioning unit is overall cheaper than you'd expect. The air conditioner doesn't need to be rated for the peak-loads anymore, but can run more continuously at lower temperatures (ie: at night to store chilled energy into the water).

So you downsize your air conditioner, as you aim for average-loads... compared to everyone else who has to buy an air-conditioner sized for peak loads.

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You seem correct about utilization. Now I wonder if a dual-use heat-pump / cooling system would be best. Heat up your house in the winter, cool down your house in the summer to double-duty the water-tank thermal energy storage.

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The "Earthships" discussed elsewhere in this topic effectively use thermal energy storage in dirt itself to heat and/or cool the entire house. It seems to use a lot of land, but single-family home owners generally have a large-ish yard where the earth can serve as the energy storage mechanism.

[cgdcraig]

Dealing with cold energy(coolth) storage whether it's in ice or chilled water is tricky mostly because of the capital cost involved with adding a storage system that can only do one thing, namely store cold. They're great for specific regions where you'll be using them on a daily basis. Chilling water outside of the peak times for use during peak cooling has been studied a lot in litterature there's a recent article here about storing excess solar energy in cooling energy:https://www.sciencedirect.com/science/article/pii/S221067071... , the main problem with the system is one of practicality. In order to effectively use the cold storage you need to use liquid cooling like the ones used in commercial buildings, that or switch to a water source chiller with a cooling tower. You can build it, but whether the total cost of that system is less than buying a bigger AC unit and paying more for power depends entirely on local conditions(seasonality,diurnal temperature changes, whether you pay for demand as well as power and whether you're on time of day metering).

------------ Using it for winter and summer does increase the utilization and would be best practice but places with winter/summer seasonality have a golden zone where you don't need active heating or cooling. If you're below 24c and above 18c you don't need much energy to maintain thermal comfort, provided you're not in a high humidity environment. During the winter it's better to use solar collectors with a thermal syphon for heat collection instead of stocking up heat since peak thermal demand occurs at night.

------------ They're known as earthpipes or earth hear exchangers and they come with their own problems, namely proximity to surface and thermal load imbalance over seasons. The earth is a really shitty thermal reservoir because it bleeds heat out the side and the top, the really big thing that it has going for it is that it's free. When you use the system in an environment thats either mostly hot or mostly cold you change the ground temperature in the long run, either increasing it or decreasing it over time. This in turn affects the ability of the system to condition air, there's also the problem that it can only bring the air temperature up to that of the ground during winter so you still need a heating system to supplement it; works great for cooling though. Basically the system gives you thermal energy at no operational cost(other than the fan) but you have to either accept whatever temperature it gives you or have a way to further condition it. Earthships generally use the sun in the winter to bring the temperature up during the day and have a thermal mass inside the house that maintains the temperature at night.