There may be passive geothermal heat pump architectures that would be a good fit. Surprised that you can still learn about geothermal heat pumps from the U.S.

There may be passive geothermal heat pump architectures that would be a good fit. Surprised that you can still learn about geothermal heat pumps from the U.S. government: https://www.energy.gov/eere/geothermal/geothermal-heat-pumps https://www.energy.gov/eere/geothermal/geothermal-heat-pumps