As you dig into the the earth’s surface the temperature tends to stabilize. This temperature is very dependant on the depth and location but it is relatively stable. It is this stability that allows us to design passive geothermal heating and cooling systems that augment classical hvac systems.
Passive geothermal airflow systems are about 10 times more efficient the the average air conditioning unit. The design, installation and even maintenance of the system are very straight forward as you will see from this 4 part video series.
The series highlights a passive geothermal air flow system built recently near the city for Leon in France. The 4 videos cover everything you need to know, from conception of design through to operation and maintenance .
In this second video you will see the actual construction of the system. Two fairly large diameter pipes are laid in the trench at a maximum depth of 4 meters, spaced at least one meter apart. The gradient of the trench is greater than 3% to allow for condensation to run towards the removal ports.
These flexible pipes are very smooth on the inside and must not produce any types of plastics off gas that can get into the ventilation system for the home. The pipes must also be able to easily support the weight of 4 meters of soil on top of them.
The Cost and Payback For Passive Geothermal in an Off Grid Home Design.
Cost saving and performance. The examples cost savings are based on the cost of energy in France, so the kwatt savings may be more interesting to you for comparison.
One year later. The maintenance of this passive system is very simple. All you really need to do is make sure the drain ports are working and that the filters are clean.
I hope that you have learned all about passive geothermal air systems. The payback for such an installation seems to be many years but if you are building a home to have zero energy bills and designed to be offgrid this technology compliments the other construction technigues you will need to use. Adding solar pv panels and solar hotwater with ultra insulation may mean that you do not need any other HVAC system at all!
Leave us some comments or send us your ideas for sustainable and off grid home designs. We love to answer readers comments!
About Gordon Smith Gordon's expertise in the area of industrial energy efficiency and alternative energy. He is an experienced electrical engineer with a Masters degree in Alternative Energy technology. He is the co-founder of several renewable energy media sites including Solar Thermal Magazine.