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Energy and Buildings 48 (2012) 1–7

Contents lists available at SciVerse ScienceDirect

Energy and Buildings

j ourna l ho me p age: www.elsev ier .com/ locate /enbui ld

eview

hermal characterization of gypsum boards with PCM included: Thermal energytorage in buildings through latent heat

licia Oliver ∗

epartment of Construction and Technology in Architecture, Polytechnic University of Madrid, Madrid, Spain

r t i c l e i n f o

rticle history:eceived 6 November 2011eceived in revised form 16 January 2012ccepted 20 January 2012

eywords:hermal energy storageCM

a b s t r a c t

This work studies the thermal behavior of a new construction material: gypsum board containing 45%by weight of phase change materials (PCMs) reinforced with additives.

A facility has been designed and built to simulate the hygrothermal conditions of any room or building.The influence of different parameters and variables regarding heat storage in buildings (air temperature,air velocity, material position, and so on) has been studied.

The thermal storage capacity of different construction materials with similar use and position inbuildings than boards with PCMs – laminated gypsum boards, bricks, etc. – has been evaluated and

ypsumoardnergy savinghermal comfort

compared.It has been proved that a 1.5 cm-thick board of gypsum with PCMs stores 5 times the thermal energy of a

laminated gypsum board, and the same energy as a 12 cm-thick brick wall within the comfort temperaturerange (20–30 ◦C).

This work demonstrates the suitability of incorporating PCMs into gypsum boards to increase heatstorage capacity and to reduce energy consumption.

© 2012 Elsevier B.V. All rights reserved.

ontents

1. Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3.1. Incoming temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.2. Air velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.3. PCM percentage in the board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.4. Board thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.5. Comparison between different materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

. Background

Thermal energy storage has been linked to architecture since oldays. In recent years, thermal energy storage systems are arousing

Abbreviations: BW, brick wall (t = 12.0 cm); CP, cladding position; FP, freeoblique) position; LY, laminated gypsum board; PCM, phase change material;B*, slim board (t = 1.5 cm) with PCMs; SP, sandwich panel (2 layers aluminum1.5 mm) + 100 mm insulation material); TB*, thick board (t = 2.5 cm) with PCMs;in, incoming temperature; Tins, inside temperature; Tint, interior temperature; Tout,utgoing temperature; Tsurf, surface temperature.∗ Tel.: +34 656374856.

E-mail address: oliver alice@yahoo.es

378-7788/$ – see front matter © 2012 Elsevier B.V. All rights reserved.oi:10.1016/j.enbuild.2012.01.026

the interest of scientists actively pursuing the reduction of fuel useand seeking solutions to energy crisis. The systems make possi-ble the correspondence between both energy supply and demandperiods, and have great potential for improving energy efficiency.

Latent heat storage through PCMs is the most efficient way tostore thermal energy in the construction field.

PCMs may be applied in several fields, such as medicine, botanyand sports [1,2]. Different research projects have been developedin the building field, from the early 1980s of the last century. Mostof them are focused to combine PCMs with different construction

materials, such as concrete, ceramic, glass, or to incorporate theminto constructive elements, like sandwich panels so that thermalinertia is improved [3–9]. Other lines of research have studied their

2 A. Oliver / Energy and Buildings 48 (2012) 1–7

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3. Results and discussion

The test results about the influence of variables in thermal stor-

Fig. 1. Thermal inertia accumulated according to t

pplication to improve the effectiveness of specific devices in build-ngs, such as water and photovoltaic systems [10–13].

The reasons for choosing gypsum in this work are availability,rofusion in construction, and mainly its position in constructionystems. Gypsum is usually found in partition walls and it is alwaysocated in the interior side of a wall as a cladding element. Thisuarantees the use of most of the thermal inertia; actually this getsncreased when PCMs are added since the insulation material isutside, as showed in Fig. 1.

Since the 1990s several experiences have studied the additionf PCMs to gypsum. Some of them were focused on physical char-cterization [14–17], while others were centered on the numericalalculation of heat capacity [18–21].

There is a product available in the market – Smart Board, BASF22] – that includes 26% by weight of PCMs.

A new construction element has been studied in this research: aypsum board including 45% by weigh of PCMs, which is the highestate ever incorporated. The work is particularly intended to studyts thermal behavior, and to demonstrate its suitability to guaranteehermal inertia in any room.

. Materials and methods

A new method has been proposed to evaluate the thermalehavior of different construction materials – i.e. thermal stor-ge capacity, thermal delay, and so on – depending on boundaryonditions, such as air velocity or indoor temperature.

Micronal DS 5001X has been chosen among all PCMs availablen the market. This microencapsulated paraffin avoids leakage dur-ng the liquid phase and makes heat transfer easier by increasinghe contact area. Its phase-change temperature is 26 ◦C, close toomfort conditions, and its enthalpy is 110 J/g.

Paraffin has been mixed with gypsum and reinforcing addi-ives, such as fiber and plasticizer. Several combinations covering aide range of doses of aggregates have been mixed to get different

ompound materials which have been tested both physically andechanically. The product containing the highest rate of PCMs – in

ompliance with the regulations regarding physical and mechani-al properties of gypsum (UNE 13 279) [23] – has been chosen.

An experimental facility was previously designed and manufac-ured to simulate energy exchange between materials and indoornvironment of a building. The facility consists of an insulatedlosed circuit where air is put in motion by a controlled fan. Airemperature can be risen up through a heater and controlled by

P.I.D., to reach the selected conditions. Heat exchange betweenhe air flow and the test materials takes place in an adiabatic box.

wo thermocouples measure the temperature at both the adiabaticox inlet and outlet. The energy accumulated in each time intervalould be estimated, and hence the stored energy [23]. Data systemnd data logger software complete the facility.

sition of the insulation material within the wall 2.

Several parameters have been analyzed to compare the influ-ence of the boundary conditions on the energy exchange:

. Incoming temperature: 25 ◦C, 30 ◦C, 35 ◦C, 40 ◦C.

. Air velocity: 1.5 m/s and 2.0 m/s.C. Weight percentage of PCMs in the board: 37.5% and 44.5%.

. Board thickness: 1.5 cm and 2.5 cm.E. Board location: cladding and free (oblique) position.

Several construction materials have been tested:

1. Gypsum boards with 44.5% PCMs (1.5 cm thick).2. Gypsum boards with 44.5% PCMs (2.5 cm thick).3. Gypsum boards (1.5 cm thick).4. Brick wall (12.0 cm thick).5. Thermal brick wall (14.0 cm thick).6. A sandwich panel made of aluminum sheets with insulation core

(10.0 cm thick).

Thermal tests were carried out using 1 m2 of each construc-tion material. The thickness of each element was different: 1.5 cmand 2.5 cm for the gypsum boards, 10.0 cm for the sandwich panel,12.0 cm for the brick wall, and 14.0 cm for the thermal-brick wall.

Losses have been primarily quantified trying out the adiabaticbox without materials. The same boundary conditions have beenused for testing materials.

The calibration of the equipment required the repetition of trialsto eliminate measurement errors. As a whole, 170 tests have beencarried out.

The following parameters were tested: incoming tempera-ture (Tin), outgoing temperature (Tout), inside temperature (Tins),and surface temperature (Tsurf). Temperature measurements wererecorded every 2 min.

As an example, the values obtained for these parameters in onethermal test are shown below.

Fig. 2 shows test conditions: gypsum boards with 44.5% PCMs,2.5 cm thick, free (oblique) position.

The evolution of the difference between input and output tem-perature may be obtained from these values, and therefore thestored energy in time, as shown in Fig. 3.

age capacity have been summarized in the following tables andgraphs. It was found that no energy is stored beyond 4 h testingand even before. The values represented in the following tablesand graphs correspond to this period of time.

A. Oliver / Energy and Buildings 48 (2012) 1–7 3

40

30

35

Tin AND Tout VAR IATI ON IN TIME GYPSUM BOARD WITH PCM, T= 2.5 cm FREE POSI TION

20

25

T (

ºC)

10

15

0.30.20.10.0

Time (h )Tout Tin Tinside Tsurf

Fig. 2. Variation in time of Tin, Tout, Tins, and Tsurf 4.

1600

STORED ENERGY GYPSUM BOARD WITH PCM T 2 5

1000

1200

1400STORED ENERGY: GYPSUM BOARD WITH PCM, T= 2.5 cm. FREE POSI TION

400

600

800

E (

kJ

)

0

200

0.40.30.2

Time( h)

d with PCMs (Tin = 35 ◦C), free (oblique) position 4.

3

P

ees

t6t

3

t0(

TG(

Table 2Gypsum board with PCM 37.5%, Tin = 35 ◦C. Free position. Stored energy (kJ/m2).

Vair (m/s) Time (h)

2 4

0.10.0

Fig. 3. Energy stored by 1 m2 of gypsum boar

.1. Incoming temperature

Table 1 shows energy stored by 1 m2 of gypsum board (37.5%CMs. T = 1.5 cm. Vair = 2.0 m/s. Free (oblique) position.

The selected range of temperature – from 25 ◦C to 40 ◦C – cov-rs a wide palette of hygrothermal conditions within a buildingxposed to different boundary conditions, such as large heat gains,olar radiation, equipment, occupancy, lighting and so on.

As the incoming temperature is higher the energy provided byhe system increases. If necessary, the new boards can store over00 kJ/m2, that is to say, they can store almost three times morehan in low thermal load spaces.

.2. Air velocity

Table 2 shows energy stored according to air velocity.

Selected values for fan drive were 1.5 m/s and 2.0 m/s. According

o measurements taken in the adiabatic box, the air velocities were.38 m/s and 0.58 m/s respectively which fit in the comfort range0–2.0 m/s), see [1].

able 1ypsum board with 37.5% PCM. T = 1.5 cm. Vair = 2.0 m/s. Free position stored energy

kJ/m2).

Tin (◦C) Time (h)

2 4

25 183.42 236.4930 413.27 501.4735 403.26 575.9540 496.05 612.03

1.5 420.20 455.662.0 540.95 588.16

When the air velocity is 2.0 m/s, the stored energy is 25% morethan at 1.5 m/s. If air velocity gets increased to the limit for comfortconditions, the thermal storage capacity of the system would besignificantly improved.

3.3. PCM percentage in the board

Table 3 shows energy stored according to %PCM in the boardand T .

in

The incorporation of PCMs into a gypsum board entails adecrease of its physical and mechanical properties [23], which caneven ultimately provoke the lack of suitability for its intended use

Table 3Gypsum board with PCM, Vair = 2.0 m/s. Free position. Stored energy (kJ/m2).

PCM Tin (◦C) Time (h)

% 2 4

37.5 30 406.14 578.8335 499.61 613.00

44.5 30 489.04 705.0635 592.34 740.73

4 A. Oliver / Energy and Build

Table 4Gypsum board with 44.5% PCM. 10 kg. Vair = 2.0 m/s. Cladding position. Stored energy(kJ/kg).

Thickness (cm) Tin (◦C) Time (h)

2 4

1.5 30 39.00 56.2335 47.11 61.22

2.5 30 34.19 46.8035 40.89 59.04

Table 5Gypsum board with 44.5% PCM. Vair = 2.0 m/s. Free position. Stored energy (kJ/kg).

Thickness (cm) Tin (◦C) Time (h)

2 4

1.5 30 52.48 65.0335 56.68 70.88

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At 30 ◦C in free (oblique) position, when energy is exchanged

2.5 30 52.09 71.6435 57.30 78.81

wall and ceiling cladding, and room separation). The percentagesandled in these experiments far exceed the amounts in previousesearch (25% by weight, [22]). This has been possible through theddition of other reinforcing materials that guarantee the mainte-ance of physical and mechanical properties of the gypsum board.

The percentages of PCMs expressed by weight are the two high-st doses used in the manufacture of boards: 60% and 80% of theeight of the gypsum. Table 3 shows the stored energy by a gypsum

oard with PCMs depending on the percentage of this material.An increase of 7% in PCMs improves around 20% the board ther-

al storage capacity, since energy is stored as latent heat.

.4. Board thickness

The boards produced for these tests have the same thicknesshan conventional gypsum boards: 1.5 cm and 2.5 cm. Tests haveeen carried out taking into account the same mass of constructionaterial (10 kg), instead of the area (1 m2) – considered in other

rials.Table 4 shows energy stored according to board thickness.

ladding position. Table 5 Energy stored according to position andhickness. Free (oblique) position.

Boards in cladding position – A and B cases in Fig. 4 are washed

y the air flow on one side (indoor side), and the energy exchangeccurs through one side. Thermal exchange affects the exteriorayer of the material (1 cm of cross-section approximately). That

Fig. 4. Scheme of thermal effects on boards w

ings 48 (2012) 1–7

means that in 1.5 cm-thick boards the thermal exchange affects the66.66% of the material, and in 2.5 cm-thick boards the 40.00%.

Boards in free (oblique) position – C and D cases in Fig. 4 arewashed by the air flow on both sides, and the energy exchangeoccurs through both sides. In this case, for a 1.5 cm-thick board,the thermal exchange affects the 100.00% of the material, and in2.5 cm-thick boards the 80.00%.

So, the relationship of the percentage of material affected bythermal exchange between case A and B is 1.66, and between caseC and D, is 1.25. This explains why with the same mass (10 kg), a1.5 cm-thick board stores 15% more thermal energy than a 2.5 cm-thick board (cladding position), as is shown in Table 4, and thispercentage decreases up to 5.8% more in free (oblique) position,Table 5.

The influence of different variables in the stored energy by aboard is shown in Figs. 5 and 6. The following variables have beenestablished:

Vair = 2 m/s.

Percentage by weight of PCMs in boards = 44.5%.The results obtained for a 2.5 cm-thick board for both positions

(cladding and free) at two different temperatures (30 ◦C and 35 ◦C)are shown in Fig. 5. The results obtained for a 1.5 cm-thick boardare shown in Fig. 6.

3.5. Comparison between different materials

Other building elements and materials have been tested to com-pare their thermal behavior with the one of the gypsum boards withPCMs. The results can be summarized in Table 7 and (Figs. 7 and 8).

The slim boards store 17.3% less energy than the thick boardsin these conditions. In the case of thermal brick walls, storage sur-passes 16%.

Under these conditions, thick boards store 13.8% more energythan brick walls. Also, thick boards store 22% more energy than slimboards (1.5 cm thick) and 71.9% more than gypsum boards.

Actually, the heat storage capacity of brick walls and gypsumboards is based on the temperature variation of the material itself.As this tends to 0 – when the system gets stable, effectiveness getsworse.

The energy stored per unit area of each building material isshown in Table 6.

Table 6 shows comparison of the energy stored per m2 of build-ing material, (Tin, 30–35 ◦C).

through both sides, the thermal storage capacity of a 2.5 cm-thickgypsum board with PCMs is 15.9% lower than that of a thermalbrick wall, and it is 12.1% higher than that of a 1.5 cm-thick board,

ith different thickness and position 5.

A. Oliver / Energy and Buildings 48 (2012) 1–7 5

2000STORED ENERGY GYPSUM BOARDS WITH PCM T= 2 5 cm

1200

1400

1600

1800STORED ENERGY GYPSUM BOARDS WITH PC M T= 2.5 cm.

Tin= 30ºC Cladding Posi�on

Tin= 30ºC Free Posi�on

Tin= 35ºC Cladding Posi�on

400

600

800

1000

E (k

J) Tin= 35ºC Free Posi�on

0

200

0.0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5 4.0

Time (h)

Fig. 5. Energy stored by 1 m2 of gypsum board with PCMs (2.5 cm thick) for several boundary conditions 6.

2000STORED ENERGY GYPSUM BOARDS WITH PCM T= 1 5 cm

1200

1400

1600

1800STORED ENERGY GYPSUM BOARDS WITH PCM T= 1.5 cm .

Tin= 30ºC Cladding Posi�on

Tin= 30ºC Free Posi�on

Tin= 35ºC Cladding Posi�on

400

600

800

1000

E (k

J) Tin= 35ºC Free Posi�on

0

200

400

0.0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5 4.0Time (h )

Fig. 6. Energy stored by 1 m2 of gypsum board with PCMs (1.5 cm thick) for several boundary conditions 6.2500

STORED ENERGY IN SEVERAL MATERIALS (Tin= 35ºC) FREE POSITION Figure 7

1500

2000

STORED ENERGY IN SEVERA L MATERIAL S (Tin= 35ºC) FR EE POSITION

SB*TB*TBWSP

Figu re 7

1000

1500

(kJ)

LGBBW

0

500

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

E (

Tii me (h )

Fig. 7. Comparison of the stored energy per m2 of building material. Free (oblique) position, Tin, 35 ◦C 6.

2000STORED ENERGY IN SEVERAL MATERIALS (Tin= 35ºC) CLADDING POSITION

1200

1400

1600

1800STORED ENERGY IN SEVERAL MATERIALS (Tin = 35ºC) CLADDING POSITION

SB*

TB*

BW

LGB

600

800

1000

1200

E (k

J)

LGB

tbw

SP

0

200

400

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0Time (h )

Fig. 8. Comparison of the stored energy per m2 of building material. Cladding position, Tin, 35 ◦C 6.

6 A. Oliver / Energy and Build

Table 6Different materials. Vair, 2.0 m/s; several positions. Stored energy (kJ/m2).

Material Tin (◦C)

Position 30 35

Slim boards with PCM Cladding 587.55 705.06Free 705.06 740.73

Thick boards with PCM Cladding 617.05 1050.9Free 740.46 1402.8

Gypsum board Cladding 160.2 229.05Free 175.80 256.54

Brick wall Cladding 641.69 878.69Free 718.69 931.41

Thermal brick wall Cladding 808.22 1452.94Free 929.46 1627.3

Sandwich panel Cladding 161.28 219.50Free 175.8 252.42

Table 7Different materials. Vair, 2.0 m/s; several positions. Stored energy (kJ/kg).

MATERIAL Tin (◦C)

Position 30 35

Slim boards with PCM Cladding 56.22 67.47Free 67.47 70.88

Thick boards with PCM Cladding 34.67 59.04Free 41.60 78.81

Gypsum board Cladding 13.35 19.09Free 14.62 21.38

Brick wall Cladding 6.20 8.49Free 6.94 9.00

Thermal brick wall Cladding 5.57 10.02Free 6.41 11.22

Sandwich panel Cladding 15.43 21.00

awast

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297–306.[4] M.M. Farid, et al., A review on phase change energy storage materials and appli-

Free 16.82 24.16

s described in Table 6. Let us remember that 1 m2 of thermal brickall weights 140 kg, well above the 17.8 kg required to configure

2.5 cm-thick gypsum board with PCMs. Much of this energy wastored at the initial stage, when the difference between tempera-ures was higher.

At 35 ◦C, the thermal storage capacity of thick boards is 13.8%igher than that of a brick wall, 22% higher than the thermal storagef thin boards, and 71.9% higher than the thermal storage of com-on gypsum boards. In fact, the thermal capacity of brick walls and

ommon gypsum boards depend on temperature variation of theaterial itself. As this tends to 0 – when the system gets stable, all

ts effectiveness gets lost.Free (oblique) position: in these conditions, slim boards store

7.3% less energy than thick boards, while the thermal brick wallxceeds 16%.

The energy stored per unit mass of each building material (kJ/kg)s shown in Table 7.

Table 7 shows comparison of the energy stored per unit mass ofuilding material.

In the light of the results shown in Tables 6 and 7, the idealystem chosen for thermal energy storage has been a 2.5 cm-thickypsum board with PCMs (44.5%) used in free (oblique) position.

Since the air flow in the adiabatic box (0.58 m/s) is lower thanhe maximum flow allowed within the comfort range, the energyrovided by the experimental model is well below than in a real sit-

ation (1–2 m/s). The working temperature has been fixed at 35 ◦C,hich represents a building with high internal and external gains.

ings 48 (2012) 1–7

In consequence, a 15 m2 partition wall (dimensions: 5 mlong × 3 m high) built with the new construction material couldstore 21,000 kJ. This equals to the amount of energy passing througha 25 m2 simple clear glass in a summer day at 15 h, or to the inter-nal loads of 170 people in an office; and the thermal losses throughnight ventilation in a 60 m2 room with one air change per hour,when the difference between indoor and outdoor temperature is10 ◦C. That means that by using this material, combined with pas-sive strategies – air cooling, sunlighting – contributes to reduce theenergy consumption in a building (heating and cooling) keeping onthermal comfort.

Thus, the new construction material is thermally characterized.Its viability and opportunity for manufacturing and commercial-ization have been demonstrated.

4. Conclusions

Comparison between different materials

- The melting rate of PCM depends on the amount of energy pro-duced, i.e. on the air velocity and temperature of the room,especially in the areas close to the material (walls and ceiling).

- Taking into account the boundary conditions, such as indoor airvelocity, temperature and so on, the amount of material necessaryfor microencapsulation can be estimated, so as latent heat storagemay be combined with passive heating and cooling strategies tominimize energy consumption in buildings.

- A thermal lag is caused by the low conductivity of the material.The lag is related to the rate of phase change and it compensatesfor the differences between day- and night-time temperaturesoccurring in continental climates (Madrid).

- Air velocity increases the energy flow and the exchange with thematerial gets improved. A rise of 0.5 m/s in air velocity means anincrease of 14% in stored energy.

- When the percentage of PCMs in the board is increased from37.5% to 44.5%, the thermal capacity of the compound materialgets improved up to 20% (30 ◦C and 35 ◦C).

- Boards and any other construction material should be in contactwith the energy flow to get a proper energy exchange. The thermalstorage capacity of boards in free (oblique) position is improvedup to 33% compared to the results obtained when they are usedas cladding elements.

- At 30 ◦C, a 1.5 cm-thick gypsum board with 44.5% PCMs stores asmuch energy as a 12 cm-thick brick wall, and 5 times the energystored by a common gypsum board.

- At 35 ◦C, a 2.5 cm-thick gypsum board with 44.5% PCMs stores asmuch energy as a 14 cm-thick thermal brick wall.

- It is concluded that for the same test conditions, the new gypsumboard with 45% PCMs stores 5 times more energy per unit massthan a thermal brick wall, 9.5 times more energy than a brick wall,and almost 3 times more energy per unit mass than a commongypsum board.

References

[1] B. Jones, K. Hsieh, M. Hashinaga, The effect of air velocity on thermal comfortat moderate activity levels, ASHRAE Transactions 92 (1986) 761–769, Part 2B(CONF-8606125).

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