I have a nominally dry crawl space that is around 22' square and about 4' tall with a concrete floor. It has no indication of leaks and is dry, but too moist during the hot Maryland summers to keep anything that is not durable in there. It has the air vents from the HVAC for the room above running through it. What is the best way (if possible) to keep the humidity low enough in summer to keep tools/card board boxes/ anything less durable in there during the humid Maryland summers? My initial thought was to add a vent or two down there and keep them closed in the winter and opened slightly in the summer. Any thoughts/insight would be greatly appreciated.
An alternate method avoiding high electricity bills and the necessary water drain for the dehumidifier: Installing a fan of an old PC at the Luv side, connected to a small power supply from an old phone or similar and a timer. If the fan runs only in the night, it pushes in statistically colder and dryer air. In 1 or 2 weeks the space will be much dryer.
You could put a dehumidifier in the space. A dehumidifier is basically a refrigeration unit which is optimized to condense water vapor from a space. It will not cool the space and in fact will be a net heat source.
There would be a problem in getting rid of the condensed water. You would want to pipe it outside and have it drip into the ground. Some dehumidifiers empty into a reservoir which has to be emptied by hand which would not be desirable. Some dehumidifiers might have a pump to allow the water to be piped away and even raised to get it out of a basement.
If you added an outlet or outlets from an a/c duct passing through the crawl space to direct conditioned air into the crawl space, this would be transporting air from the living space into the crawl space. The net loss of air in the living space would create a slight negative pressure in the living space relative to the outside and cause infiltration of outside air into the living space.
So you would need an air return to allow the air from the crawl space to get back to the air handler. This would basically connect the crawl space to the living space. You should carefully consider this before hacking into the ducting in the crawl space.
It may be that since you have a concrete floor in the crawl space you could get just enough air flow into and out of the crawl space to keep it dry enough for storage. The register on the vent could be adjusted so the air flow would be just enough to accomplish what you want, but I think you should obtain professional opinions on whether this actually works in practice.