Earth Air Tunnel

Could you explain what an 'Earth air tunnel' is please, or point me to a link?

Thank you - John.

Interesting concept! Reminiscent of some of the late 1800's homes that were built with deep basements in the earth and a central column that exited through a small windowed room centered on the roof. Caves are reported to be about 60 deg. F year round. Some similarity to the water circulation system that utilizes the relatively constant underground temperature.

An internet search (is google now a verb?) for 'Earth air tunnel' will result in some good information.

The topic is interesting and generates curiousity to know practical applications.

Is it possible to cite few examples whether and where such 'Earth Air Tunnel' systems are functioning in practice?

please Contact The Energy & Resource Institute(TERI) Previously known as TATA Energy Research Institute is a 25 Year Old Non-Profit Research & Development Institue has pioneered In Sucessful Implementation of EARTH-AIR TUNNELS(EAT) In Amy Energy Efficient Buildings in India.They Provide Professional Consultancy For DEsigning and Implementation Of EARTH Air Tunnels. Or Visit:www.Teri.res.in

Gross OverGeneralization warning!

The ability of earth to remain temperature stable at any depth after you penetrate it is deeply dependant on soil moisture!

While I had successfully experimented with both ground sourced heat pumps (an earth air tunnel with a heat pump extractor) as well as ground water heat exchangers (pump the water up, heat it up and drop it back down another well) while living in the deep southern US; when I attempted experiments of the same sort living in Arizona I failed miserably.

Soil moisture is the earth's circulatory system, much like your blood. Like blood which brings heat to your surface to radiate, soil moisture allows the heat you are pumping underground to disperse. Without sufficient soil moisture you will simply heat up the dirt. This is overcome when using something as large as a mineshaft, but a serious issue when using something as small as the commercial coils installed in the yard.

Phoenix Arizona simply doesn't have soil moisture sufficient, at a reasonable depth to make this possible. You would be well advised to find the local hydrological data for a site you are considering. In Arizona, a 100' deep well will achieve local outside air temperature within days; and remain at that temperature for days even after being resealed.

If you happen to have a 100' well available I might suggest using it as an evaporative cooler with misters at the top of a sealed environment. Then as long as you don't exceed about 30% humidity it will cool nicely and you can run heat exchangers or simply pump cool air out of it. Of course you can do the same thing above ground far cheaper.

Emmett

I would like to put forward the concept of Geo Thermal Cooling or Earth Air Tunnel. This works on principle that the earth with its huge mass is a neutral source of thermal energy for cooling or heating purposes. The earth below a depth of few meters remains almost at constant temperature throughout the year. During summers as the temperature of earth is lower than the atmospheric temperature it can be used for cooling purposes where as during winters the earth temperature is higher than the atmospheric temperatures, it can be used for heating purposes.

To utilize this property of earth heating system, we lay passageway for the air underneath the earth surface at about depth of 3 to 4 meters, because at this depth sub soil temperature does not change throughout the year.

I am an Architect practising in India. I am not a member of the site. If you want to know further you can contact me on my id arbharat@gmail.com.

I used to see them all the time in Mining shafts in the mountains where I grew up. Some were so good created a pretty good wind at the entrance on a windy day.

I have seen one and built one at the residential scale of construction. Factors to consider include the soil moisture content as mentioned by others because this significantly affects the thermal conductivity of the soil, heat load, and other similar engineering concerns. The temperature difference between the soil and the surface is a function of the depth, both in the magnitude and the time lag compared to the surface temperature. I suggest you look at some reference materials on earth sheltered construction for more detail on this, but at 30' (9m) depth, the time lag is typically 6-months and the delta-T over the year is close to 1-deg C.

Practical concerns are: Introduction of toxins, unwanted odors, etc. from the soil (so probably a lined earrth tube is better). Control of water condensation during humid warmer weather along with the probability of mold growth if water is standing (continuous slope to appropriate type of drain). Ability to clean if needed. Protection from entry of unwanted animals, insects, etc. And, preservation of the air entrance location from damage or removal by people in the future who may not know its purpose.

My empirical one was with 10" dia (254 cm) PVC pipe with rubber gasket joints so it would remain flexible in the soil (SDR-35 in the USA), encased in compacted clay about 5' (1.6m) below the surface, 80' (26m) long. It started outside with an above-ground vent in the corner of the building, insulated from it, ran out into the yard where it turned and came back under the basement floor, and ended inside by connecting to the return air plenum of the central heating and cooling unit. Thus, whenever the air was being circulated in the building, there was a mild positive pressure equal to the pressure loss due to friction in the return air system. All air leakage points in the building were therefore exfiltration only. All exhaust fans had a generous source of earth tempered fresh air into the building. The low point in the earth tube had a small drain pipe attached, which went to a nearby sump pump pit.

Thre are many methods of passively heating or cooling buildings, but the local climate you have will be the biggest concern in deciding which one(s) to use. Best wishes in your work. Contact me, if you want at jmueller245@yahoo.com.

John Mueller, Kansas City, USA

In residential buildings air conditioners are provided for comfort during summer.Can the " Earth Air Tunnel (EAT)" system be a substitute for air conditioners?

Air handling unit in EAT system consumes lot of power. In terms of energy consumption,is CAT cost effective? Can the EAT be installed in smaller capacity units?

Can you throw some light on these, if possible? It can be very useful. Thanks.

N.V.Mani

Question "Can anybody tell me how to design an earth air tunnel for passive cooling of buildings?" still remains unanswered.

Since this subject is related to design concepts on energy efficiency in architecture,a Civil engineer / Architect may clarify.

Pipe length, Pipe diameter,Air flow rate, soil temperature etc influence exit air temperature and fan power required. Understand that there are computer programs.

please Contact The Energy & Resource Institute(TERI) Previously known as TATA Energy Research Institute is a 25 Year Old Non-Profit Research & Development Institue has pioneered In Sucessful Implementation of EARTH-AIR TUNNELS(EAT) In Amy Energy Efficient Buildings in India.They Provide Professional Consultancy For DEsigning and Implementation Of EARTH Air Tunnels. Or Visit:www.Teri.res.in

Thank you very much for the information. I shall visit the website www.Teri.res