Access to affordable energy is the greatest historical differentiator in development between societies.
Thomas Edison strongly argued that DC was a better solution inside the home which was absolutely correct. AC is better for distribution to the home. Many modern devices and appliances already run on AC converted to DC internally from LED bulbs to induction cooktops, inverter refrigerators and dryers. Focus is not energy savings but FREEDOM from the electrical umbilical shore power to enjoy the best places comfortably for Marine Vessels, Recreational Vehicles (RVs), a remote Cabin, or village in the developing world

All Heat Exchangers Fall into 3 Reversible Groups

Air-to-Air -commonly referred to as an "Air conditioner "

Water-to-Water -commonly referred to as a "Chiller "

Water-to-Air -commonly referred to as an "Air handler" or "Geothermal"

Open-loop Geothermal is to 2 wells or a pond or a canal. Closed-loop Geothermal is to pipes buried underground. Marine chiller or geothermal systems are the same thing simply one is buried, the other not. Many marine chiller and geothermal systems are two-stage combining one or more water-to-water with one or more water-to-air.