Part 2 of Julio’s Series on Clean Energy at Sol Homestead

Have you ever felt the metal fins on the back of your refrigerator? They can be very warm. That’s because your refrigerator transfers heat from the air to a refrigerant that absorbs the heat, making the air inside your fridge cold enough for milk, fruit, vegetables, etc. The refrigerant then evaporates, is compressed, and passes through a condenser where a fan releases the heat out of the back of the appliance. This is also how air conditioners work. Air is sucked into the unit, heat is transferred to a refrigerant, cool air blows through your home, and hot air blows outside. Heat pumps are just air conditioners that work in both directions (blowing hot or cold air into your home and cold or hot air outside).

It turns out that heat transfer via air circulation as I’ve described can be much more efficient than combustion-based temperature regulation at sustaining a home at room temperature. Internationally, this has been understood for decades. Air source heat pumps are all over Japan and Europe; ground source heat pumps (same idea, but pulling the air into the unit from a hole in the ground rather than the ambient air near the outdoor unit) have become popular in higher latitude areas (Canada, Norway, Greenland, etc). Consider that other heating methods still need a blower fan to circulate the heated air through your home; heat pumps are systems where the air circulation is most of the work done to maintain a set temperature.

Continue reading →