3 ms·

With regard to regenerating the desiccant: Presumably the same heat pump used for the normal A/C cycle would be used to handle this. Add some valves and contro

With regard to regenerating the desiccant: Presumably the same heat pump used for the normal A/C cycle would be used to handle this. Add some valves and controllable dampers which are potential failure points but not expensive. Instead of dampers you could have a separate exhaust fan but either way you need to extract the hot and very humid air from the regen cycle to avoid dumping it into the building. There's a tricky optimization problem for a system like this. In heat pump mode your ideal time of day is around solar noon when temps are hottest... with an inverter (fully variable) compressor and fan you can run both at lower power to generate just enough heat needed for regen. That can clash with your cooling load and electric rates though so it may make more sense to run at night when you need to run longer or higher power to generate enough heat. Most consumer A/C systems sold in the US don't even have inverter compressors yet so that is some added cost/complexity. Many have variable speed indoor and outdoor fans but not all. There may be some decent gains to be had just by adopting the latest "conventional" refrigeration tech.

adrianmonk 3y ago
I wonder if you could just pump the liquid desiccant outside, do the drying outdoors, and then pump it back inside. Then you wouldn't need to worry about air handling for the moist air. When retrofitting a house to replace traditional AC with this, it may not be easy to get air from where the AC is located (usually the middle of the house) to the outside. If you pump desiccant outside, maybe you can squeeze desiccant hoses in right next to your refrigerant lines. Also, there's all that waste heat outside at the condenser anyway. It seems like you could use that heat to help dry the desiccant. I guess that creates a different tricky optimization problem: if you wait too long to start drying your desiccant at night, when you finally do, you risk making the house too cold because you are stealing its heat. Maybe you just pause desiccant drying until whenever AC is needed again.

adrianmonk 3y ago

I wonder if you could just pump the liquid desiccant outside, do the drying outdoors, and then pump it back inside. Then you wouldn't need to worry about air handling for the moist air. When retrofitting a house to replace traditional AC with this, it may not be easy to get air from where the AC is located (usually the middle of the house) to the outside. If you pump desiccant outside, maybe you can squeeze desiccant hoses in right next to your refrigerant lines. Also, there's all that waste heat outside at the condenser anyway. It seems like you could use that heat to help dry the desiccant. I guess that creates a different tricky optimization problem: if you wait too long to start drying your desiccant at night, when you finally do, you risk making the house too cold because you are stealing its heat. Maybe you just pause desiccant drying until whenever AC is needed again.