Passive Annual Heat Storage Principles in Earth Sheltered Housin

7/31/2019 Passive Annual Heat Storage Principles in Earth Sheltered Housin

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lower heat transfer from the building components to the ground.

Thus indicating the passive heat supply from the ground even at

the extreme cold temperatures of winter, hence is a factor for

energy saving in earth shelter buildings.

Apart from the energy values which the subsurface climate

of the earth provides, the other significant characters beneficial

to earth shelters includes a major goal of recycling surface

space by relocating functions to underground, by this earth

shelters liberates valuable surface space for other functional

uses and improves ground surface visual environment, open

surfaces for landscaping and thus a more greener atmosphere.

In order to achieve themaximumbenefitsfrom earth sheltered

housing, its application could be examined also at an entirely

community scale rather than simply at the scale of individual

housing. While contemporary use of earth sheltering is confined

to individual homes built on single plots of land or a small cluster

of houses which will absolutely be affected by surrounding

conventional structures around, the traditional use encompassed

entire communal design or villages that will stay within the same

conditions the micro-environment provides as a few isolatedearth sheltered houses do not really reach the scale needed for

sustainable development as asserted by Dodd [13], earth

sheltered mass-housing may become the general concept for

design and building with earth as Moreland [2] envisioned in his

book for entire communities enjoying dual land use by locating

all housing underground. If a single case of earth sheltering is

found to have significant advantages, these advantages can only

increase in magnitude if applied to whole communities.

1.2. From the prehistoric to the modern earth shelter

principles

Earth sheltered homes have provided shelter, warmth and

security for mankind since the beginning of recorded history. In

Japan was discovered the oldest human habitation in a layer of

earth about 600,000 years old in Kamitakamori, Miyagi

Prefecture (Japan times, 24 October 2000). Archaeologists

from the Tohoku Paleolithic Institute, Tohoku Fukushi

University and other institutes said they believe that the

finding may be one of the oldest in the world. There are only a

few remains of human dwelling structures from the early

paleolithic period in the world, as early humans such as the

Peking-man lived in caves. Researchers believed the dwellings

were built by primitive man, or homo erectus, who appeared

some 1.6 million years ago and likely reached Japan 600,000

years ago at the latest, according to the archaeologists. The

buildings could have been used as a place to rest, a lookout for

hunting, a place to store hunting tools or to conduct religious

rites.

In China, however, the modern underground habitats (earth

shelters) are commonly called cave dwellings as shown in

Fig. 1, even though they are entirely man-made earth sheltered

environments and its culture were dated back to before 2000

B.C. It is believed that underground housing preceded aboveground housing in this area. From study on the existing Chinese

earth habitats were discovered analytical data on the climatic

and topographical relationships to the unique design elements

utilized to attain living comfort by the cave shelter dwellers.

Such analysis as the rain, wind, sun and seasonal weather

conditions that exist in these areas where these dwellings were

located according to Golany [8], possibly necessitated the

advantage of its existence in these locations.

Analysis on each location also provided results and findings

in terms of climatic effects, design styles and residential

activities of the dwellers. In the North-west of China, variety of

structures existed, ranging from striking examples of hiddenopulence to humble subterranean cubbyholes where its people

immerse themselves in natures simplicity. Golanys [8]

Fig. 1. A typical earth shelter plan in North-western China.

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research also provided analytical data on climatic and

topographical relationships to the structural design styles.

With single unit design solution, multi unit designs and finally

Urban planning initiatives on how to achieve a sunken city thatexists beneath rather than above ground level as seen in Fig. 2

below. Also fascinating in discovery included methods and

techniques of ventilating the building units naturally without

the necessary use of mechanical ventilation options. Such

natural ventilation alternatives provided a cost efficient and

energy efficient value to the whole process.

2. The concept of passive annual heat storage system

PAHS a method of collecting heat in the summertime, by

cooling the home naturally, storing it in the earths soil naturally

and then afterwards returning that heat to the contact structure(earth home) in the winter was originally introduced by Hait [4]

in his book published in 1983. It includes extensive use of

natural heat flow methods, and the arrangement of building

materials to direct this passive energy from the earth to the

building, all without using machinery.

According to this concept, there exists cooling actions when

one climbs down basement structures or caves. This cooling

action experienced in these enclosed environments is a result of

the heat being drawn away from the body to the surrounding air

which then transfers this thermal energy into the surrounding

structures whose heat content is less than that of the adjacent air

mass. The dynamics behind this concept is that heat always

flows from a warmer system to a cooler system (as in the case

mentioned above with the human body as the warm system and

the surrounding air and walls as the cooler system). By this

action if you are warmer than the surrounding air, the heat of the

body will escape to the surrounding air until temperature

equilibrium is attained. Likewise, in the case the air inside the

room is warmer than the surrounding walls, heat will be drawn

out of the air into the walls, thus cooling the air and warming the

walls. On the other hand, if the air temperature inside the roomis cooler that the surrounding walls, heat will be drawn out of

the walls into the air by this warming the air and cooling the

walls. Passive annual heat storage (PAHS) uses this thermo-

dynamic principal in conjunction with bare earth to aid control

the micro-climate within the building, in the case of the earth

sheltered dwelling, it utilizes the surrounding earth to regulate

its temperature throughout the year.

Globally, the earth receives electromagnetic radiation from

the sun which is typically defined as short-wave radiation and

emits it at longer wavelengths known typically as long-wave

radiation. Fig. 3 below shows an analysis of the earths short-

wave and long-wave energy fluxes produced with details fromBonan [1].

Fig. 2. Aerial view of an earth shelter neighborhood in Lian Jiazhuang, Shanxi

Province, North-western China.

Fig. 3. Earths energy budget diagram showing the short-wave (a) and long-wave (b) energy fluxes.

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This absorption and re-emission of radiation at the earths

surface level which forms a part of the heat transfer in the earths

planetarydomainyields theideafor theprinciple of PAHS. When

averaged globally and annually, about 49% of the solar radiationstriking the earth and its atmosphere is absorbed at the surface

(meaning that the atmosphere absorbs 20% of the incoming

radiation and the remaining 31% is reflected back to space).

3. Thermal analysis (concept and application in earth

shelter design)

There exist two major concepts in earth shelter construction;

the Bermed shelter and the Envelope or True underground earth

shelter. In this case, this study considers the two major styles of

Bermed earth shelter construction which are:

(a) Elevational or slope design.(b) Atrium or courtyard design.

Using PHOENICS-VR fluid-flow simulation environment,

the study calculates the thermal flow pattern in the different

earth shelter designs whilst identifying the different effects of

the earths PAHS on the slope and atrium designs as shown in

Figs. 4 and 5 below.

3.1. Analysis

An architectural 3D model was developed imputing the

ordinary concrete wall module for the boundary wall materials,

while observing other necessary EARTH Environment para-

meters. The model was then subjected to two cases of

simulation tests; one with the case of the Earth shelter Slope

design parameter where only about 50% of the structuresexterior facade is in direct contact with the earth mass and

the other case of the Earth shelter Atrium design with 80% of

the exterior facade in contact with the earth mass. The

temperature Attributes assigned to the earth mass was taken

from an assumption of winter and summer variations in the

annual earth temperature values at below 510 m depth and the

surface-air temperature likewise which values was assigned as

same for the two design cases.

3.2. Results and discussion

The simulation experiment expresses the thermal systems of

the fluid-flow around and within the indoor environment of anearth shelter structure in context with the PAHS concept. After

running the Earth Solver, the result from the experiment is

presented in Figs.4 and 5 above. The difference in the two cases

(the slope design and the atrium design), suggested that the

effects of PAHS and the passive cooling effects on the buildings

indoor comfort was influenced much by the orientation of the

structure (in this case the placement depth of the building below

the grade).

The Atrium design which has 80% of its exterior facade in

contact with the earth mass presented better indoor conditions

(i.e. passive cooling and heating needs) for both the summer

and winter temperatures more than the slope design that has just

Fig. 4. Effects of PAHS and passive cooling on earth shelter indoor space in summer: (a) elevational or slope design and (b) atrium or courtyard design.



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about 50% of its facade in contact with the earth. From this

result, it could be deduced or assumed that the greater the

percentage of facade in contact with the earth the better the

passive annual heating and cooling gains.

Although this assumption seems rightly beneficial to theenergy saving concepts in homes, it is also right to consider

other detrimental factors like the normal heat and cooling losses

due to thermal transmittance factors. As Klaus [5] stated, that

earth shelters are subjected to heat and cooling losses partly via

the soil to the external air, via the soil to the groundwater below

or directly to the groundwater. Klaus presented the quantity of

loss as calculable in this case and the equation is as follows:

QT Atotal#i #OT

RAL

#i #GW

RGWW

where WOT = mean outside temperature, %0 to5 8C % (We + 15 K), ROT = Ri + RlA + RlB + Re = equiva-

lent resistance to thermal transmission room-outside air,RlA = equivalent resistance of the soil to thermal conductivity,

RlB = resistance of building component to thermal conductiv-

ity, RGW = Ri + RlB + Rls = equivalent resistance to thermal

transmission room-groundwater. Rls = T/ls = thermal conduc-

tivity resistance of soil to groundwater, D = depth of ground-

water, ls = thermal conductivity coefficient of soil, %1.2 W/mK and WGW = groundwater temperature = 10 8C.

Also to further evaluate the performance in the long-term of

subsurface environment and accurate environmental informa-

tion on the boundary conditions necessary for achieving an

efficient design, one of which is the temperature of the

surrounding soil, accurate data regarding diurnal and annual

variation of soil temperatures at various depths is necessary to

accurately predict the thermal performance of earth sheltered

structures. Although actual data on soil temperatures is not

usually abundant, research has facilitated the evaluation of the

underground climate in order to assess the suitability of earthsheltered structures. Algorithms for this calculation of the soil

temperatures at various depths have already been developed

based on existing field measurements in different regions of the

world and by this, the annual pattern of soil temperatures at any

depth can be accurately considered as a sine wave about the

annual average of the ground surface temperature, Labs [15].

Accordingly, a mathematical method was developed by Labs to

predict the long-term annual pattern of soil temperature

variations as a function of depth and time for different soils and

soil properties that are stable over time and depth. This method

is sufficiently accurate in the case certain thermal and physical

characteristics are accurately estimated.

The equation for estimating subsurface temperatures as afunction of depth and day of the year is as follows (with the unit

of cosine expressed in rad):

Tx;t Tm Asex

ffiffiffiffiffiffiffiffiffiffip

365a

rcos

2p

365

t t0

x

2

ffiffiffiffiffiffiffiffi365

pa

r (1)

where T(x,t) = subsurface temperature at depth x (m) on day tof

the year (8C), Tm = mean annual ground temperature (equal to

steady state) (8C), as the annual temperature amplitude at the

surface (x = 0) (8C), x = subsurface depth (m), t= the time of

Fig. 5. Effects of PAHS and passive cooling on earth shelter indoor space in winter: (a) elevational or slope design and (b) atrium or courtyard design.

A.J. Anselm / Energy and Buildings 40 (2008) 121412191218


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the year (days) where January 1 = 1 (numbers), t0 = constant,

corresponding to the day of minimum surface temperature

(days) and a = the thermal diffusivity of the soil (m2/day).

Following this assessment of subsurface climate, the

calculated soil temperatures can then be used in calculating

the heat flux through the building surfaces. The energy

efficiency of each wall in contact with the earth at varying

depths can thus be investigated for local climatic conditions in

the buildings.

4. Conclusion

With the information available so far on means of assessing

the performance of earth shelters and PAHS effects on these

structures, it is then possible for designers and planners in

different regions to have access to a simple framework for

assessing its efficiency at the initial planning stages. The

resulting outputs can then be used for the heat transfer and

energy consumption simulations within the building units.

Results from these simulations will provides insight into thedegree of passive heating and cooling or reduction in heat flow

that the soil climate can provide as compared to the surface

climate as well as suggesting parameters for depth placement of

earth shelter buildings for more efficient results.

Acknowledgements

This paper was inspired by the authors doctorate research

work which is based on the use of alternative passive heat

storage systems in achieving indoor comfort in hot summer-

cold winter regions. Special recognition and appreciation goes

to the Dean of the School of Architecture and Urban planning

Prof. Baofeng Li, for his support. The author also wished to

acknowledge the support by the National Natural Science

Support Fund (Contract No. 50578067) and the Special

Research Support Fund for Doctorate Degree research

programme (Contract No. 20060487008) for the Changjiang

River Districts (Huazhong and Huadong) of China. The author

wishes to appreciate the efforts and cooperation received from

the Ecology department of the school in providing data and the

assurance of assistance on further work.

References

[1] G. Bonan, Ecological Climatology: Concepts and Applications, Cam-

bridge Press, United Kingdom, 2002.

[2] F.L. Moreland, An alternative to suburbia, in: Proceedings of the Con-

ference on Alternatives in Energy Conservation: The Use of Earth-covered

Buildings, National Science Foundation, Fort Worth, TX, 1975.

[4] J. Hait, Passive Annual Heat Storage: Improving the Design of Earth

Shelters, Rocky Mountain Research Center, 1983.

[5] D. Klaus, Advanced Building Systems: A Technical Guide for Architects

and Engineers (English Translation), Published for Architecture Basel,

Boston, Berlin, 2003, pp. 50.

[6] P. Carpenter, Sod It: An Introduction to Earth Sheltered Development in

England and Wales, Coventry University, Coventry, 1994.

[8] S. Golany, Earth Sheltered Habitat (History, Architecture and Urban

Design), Van Nostrand Reinhold Company Inc., New York, 1983.

[12] J. Carmody, R. Sterling, Design considerations for underground buildings,

Underground Space 8 (1984) 352362.

[13] J. Dodd, Earth sheltered settlements, a sustainable alternative, in: Pro-

ceedings of the EarthShelter Conference, Coventry University, September

3, (1993), pp. 2636.

[15] K. Labs, Underground building climate, Solar Age 4 (10) (1979) 4450.

[17] R. Kumar, S. Sachdevab, S.C. Kaushik, Dynamic earth-contact building: a

sustainable low-energy technology, Building and Environment 42 (2007)

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Passive Annual Heat Storage Principles in Earth Sheltered Housin