2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007
DESIGN AND SIMULATION OF A BUILDING INTEGRATED PHOTOVOLTAICTHERMAL SYSTEM AND THERMAL STORAGE FOR A SOLAR HOUSE YuXiang Chen1*, A. K. Athienitis1, B. Berneche2, Y. Poissant3, K. E. Galal1 1 Department of Building, Civil and Environmental Engineering, Concordia University 1515 St. Catherine W., EV-6.139, Montréal, Québec, Canada, H3G 2W1 * Tel: (514)848-2424 Ext. 7080 email:
[email protected] 2 Alouette Homes, 200 rue Des Alouettes, St-Alphonse-de-Granby, QC J0E 2A0 3 CETC Varennes – PV & Hybrid Systems Program, Natural Resources Canada ABSTRACT This paper describes the design and simulation of a building integrated photovoltaic-thermal system with heat recovery and storage for a solar house. This solar house is to be built by Alouette Homes (AH), a prefabricated-home manufacturer, as its project for Canada’s EQuilibrium Housing demonstration initiative. The design of the building integrated photovoltaicthermal (BIPV/T) system and ventilated concrete slab thermal storage system, which use air heated by BIPV/T as heat source, will be discussed as one of many possible and feasible ways for maximizing solar energy utilization. The BIPV/T system can harvest a considerable amount of useful heat; however, some of this energy typically needs to be stored for later use (e.g. at night) with an appropriate thermal storage design. A hollow core concrete thermal storage system is utilized in addition to hot water and direct gain thermal mass. Simulation results are presented from a transient finite difference model for the house, including the BIPV/T system and ventilated concrete slab.
In Canada, the total energy consumption in the residential sector was 1,296.1 petajoules (1015 joules) in 2005, which was about 17% of that year’s total national energy consumption (Statistics Canada, 2007). Residential passive solar technologies can greatly reduce the space heating fuel consumption (Athienitis and Santamouris 2002) and consequently the size of the mechanical equipment required. Passive Solar Design Incident solar radiation on the south-oriented facing façade and roof of a house generates a great amount of heat (Eicker, 2001). BIPV/T system using Photovoltaic (PV) arrays as solar thermal collector can harvest a considerable amount of this heat. This harvested heat together with the solar radiation transmitted through windows can decrease space heating load. In order to maximize the useful amount of collected heat and, at the same time avoid overheating, the excessive portion of this heat can be stored in thermal mass, such as concrete slabs for later use (e.g. at night) (Athienitis, 1997). Sun
Building integrated PV arrays
INTRODUCTION In fall, 2006, Canadian Mortgage and House Corporation (CMHC) launched a demonstration initiative firstly named Net Zero Energy Healthy House, and later officially branded EQuilibrium Housing. CMHC describes this housing as follows (CMHC, 2006): “EQuilibrium housing integrates highperformance, energy-efficient passive solar design and commercially available on-site renewable energy systems. They are designed to produce as much energy annually as they consume. Connected to the electricity grid, these homes draw power only as needed - and can feed excess power back into the system.” Alouette Homes (AH) was selected as one of the twelve pilot demonstration teams.
Air cavity
Warm/hot air flow from BIPV/T
Air intakes in soffit
Figure 1. Configuration of house’s BIPV/T system Building Integrated Photovoltaics (BIPV) integrates of photovoltaics (PV) into the building envelope. The PV modules serve as the building outer skin. This integration can replace conventional building envelope materials. Overall cost is lowered. In BIPV/T system, the recovered heat can be collected and used for other
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007 heating purposes (Charron et al., 2005). Figure 1 shows the conceptual design of AH’s BIPV/T System. Concrete is a common material used as thermal mass. For normal density concrete, its thermal conductivity (k) ranges from 1.2 to 2.0 W/(m·k) depending on density and moisture content, and its specific heat is about 920 J/(kg·K) (ACI, 2005). The solar absorbtivity and hemispherical emissivity of rough concrete are 0.6 and 0.91, respectively (ASHRAE, 2005). Concrete’s thermal characteristics provide the possibility for structural concrete to be used a thermal mass (Braham, 2000). However, to enable storage of heat in structural concrete, an integrated thermal–structural design must be followed. The concrete thermal mass thickness, exposed area, storage-restitution period and other parameters will affect its thermal energy storage density and thermal performance (Bilgen et al., 2002). Too much concrete mass will result in a heavy loading on structure; less than required concrete mass won’t be able to accomplish thermal functions. In general, distributed thermal mass is preferable and a concrete thickness of about 20 cm has optimal thermal admittance (Athienitis and Santamouris, 2002).
MAJOR DESIGN CHARACTERISTICS The total floor area of AH’s house is about 140 m2 excluding the basement floor area, which makes up another 90 m2. The house is designed to accommodate a four-person family. The house was designed to be energy efficient, and yet affordable and easy to construct. The house’s energy performance reaches an EGH* rating of 98.3 (100 EGH* rating implies netzero energy consumption, and 92 is the minimum required by CMHC). Fig. 14 is the schematic drawing of the house’s service system The overall energy analysis approach followed was a combination of HOT2000 (NRCan, 2005), RETScreen (NRCan 2007) and Mathcad (MEEI, 2001) custom software simulation. HOT2000 was used to optimize the envelope, Retscreen the PV electricity generation, and Mathcad software to optimize heat recovery from the PV and to avoid overheating due to solar gains – i.e. optimize thermal mass in the house in relation to window area and determine the optimum window area. First, insulation was increased gradually while tripleglazed low-e-argon windows were quickly adopted as the most cost-effective measure to utilize passive solar gains incident on the south façade. Following rules of thumb (e.g. from “Tap the Sun” by CMHC) about aspect ratio of the house, a value of about 1.3 was chosen for this important variable. The design team then examined where effective thermal mass could be placed and significant mass was added in the direct gain zone (family room - floor and half wall). The
basement also contains a lot of exposed concrete mass that is utilized for storage of heat from the PV-thermal system. Based on Mathcad transient thermal simulations to determine the effectiveness of mass in storing passive solar gains while limiting temperature swings, a mass-glass combination was adopted resulting in a south-facing window area to floor area ratio of 9.1%. Increasing the insulation beyond the level adopted did not produce as much benefits as renewable energy measures. This was clearly shown at the design charrette through a combination of HOT2000 and Mathcad simulations. The high temperature swing of 5.5 C was selected in HOT2000 to increase the effectiveness of mass. Envelope The envelope of the house is well insulated. Windows are triple glazed with two low-e (0.35) hard coatings and 13 mm Argon filled gaps. The window’s effective heat transfer resistance is 0.7 RSI. The total south facing window area of the ground floor is about 13 m2, which is approximately 15% of the ground floor area. The average effective RSI values for the walls above grade and roof are 6 and 8 RSI, respectively. The basement wall’s insulating value is 4 RSI; while the basement floor is 1.5 RSI. The wall thermal resistance values were selected following a sensitivity analysis with HOT2000. Building-integrated photovoltaic-thermal (BIPV/T) System The system was designed to cover one continuous south-facing roof surface. A 3 kW BIPV/T system is to be installed in the house. It consists of 22 Unisolar PVL-136 laminates attached to the metal roofing (each panel is rated at 136 Ws for a total of 22x136 = 2992 Ws). The electricity generated by the BIPV system as determined by RETScreen is 3420 kWh/yr for a 30o slope. A gap is created between the arrays and the sublayer behind it. Outdoor air is used as the heat transfer fluid for simplicity and practical construction purposes. It is an open loop system so as to keep the temperature of the PV panels as low as possible, thus increasing their electricity production. This system is expected to produce up to 12 kW of heat at 500 cfm of air flow. Hot outlet air is to be used for domestic hot water heating, clothes drying, or thermal mass heating in order of priorities. HVAC System The primary heating and cooling equipment is to be a 2.2 ton two-stage water-to-air geothermal heat pump with an ECM (electronically commutated) motor. This heat pump uses well water, at 8.3 gpm (from 160’ deep
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007 well) which has been found at the site. The heat pump, through its desuperheater is also estimated to provide about 700 kWh/year of heating for domestic hot water . The ventilation rate is to be controlled by an occupancy sensor. When an occupant enters the house, the sensor will switch the heat recovery ventilator (HRV) to regular mode, which sets the ventilation rate at 0.3 ACH (air changes per hour). When the house is not occupied, the last person leaving the house can switch the ventilation rate to 0.15 ACH. This control strategy will reduce the heat loss due to ventilation, which is around 5070 kWh, as estimated by software HOT2000 (NRcan 2003) simulation. Domestic hot water (DHW) heating
For the basement slab, concrete is poured on steel decks which form air channels as shown in Fig. 3. Heat is stored in the concrete as hot/warm air from the BIPV/T passes through. Room air temperature is allowed to rise 5.5 oC from 21 oC (heating setpoint) to maximize passive solar heating. In order to have a higher relative friction factor (f) to generate larger convective heat transfer coefficient hc inside the channels, a layer of crushed gravel or metal mesh will be placed under the steel deck. Normal Density Plain Concrete Steel Deck (Canam P-2436, galvanized steel) Ventilation Channel (cavity) Metal Mesh (e > 5mm) Rigid Insulation Water/vapor Barrier Gravel (earth)
Th_cnc
The system consists of two 60 gallon tanks in series. The entering cold well water is first heated by a drain water heat recovery system, which then enters the first storage tank. In the first storage tank, the water will be heated using the desuperheater of the geothermal heat pump and the hot air from BIPV/T system (except in winter time) through an air-water heat exchanger. The DHW will be heated up to the final supply temperature in the second storage tank using a backup electrical heater.
89 76
64
Unit in mm
38
115
Thermal Mass Figure 3. Cross section of basement concrete slab
SIMULATION AND ANALYSIS Warm/hot air flow from BIPV/T
A transient explicit finite difference thermal network model was developed to simulate the thermal performance for the entire house, including the BIPV/T and the ventilated concrete slab in the basement.
Sun
Passive Charge Thermal Mass (4" Concrete Slab) Exhaust outside
Active Charge Thermal Mass (4" concrete slab, stores heat for hot air)
Warm/hot air can be also used for hot water heating, cloth drying
BIPV/T System Simulation T.sky
Ground
Figure 2. BIPV/T plus thermal mass system.
h.r_ps
S.pv v T.p
a T.m _gp h. r
Air Flow
_gp h. c _gp h.c
q.ma
f T.s
ap h .g
Concrete slabs are to be used as the thermal mass. Figure 2 shows the placement of the concrete mass. One 100 mm thick concrete slab on the ground floor is used as direct gain thermal storage to store solar energy transmitted through the south-facing windows of the ground floor. Meanwhile, the concrete slab in the basement is used to actively store the heat from the hot/warm air heated by BIPV/T system while the release of the heat is passive.
.o
T Exterior PV Module _rf Air Gap h.c Roofing Memberane Sheathing Insulation Attic Space
n U.i
s t T.a U.a
t T.o
Figure 4. Thermal network for BIPV/T system (one section)
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007 A quasi-two-dimensional finite difference model is used in the simulation part of BIPV/T system. Fig. 4 shows the thermal network of one section of the BIPV/T system. The BIPV/T system is divided into 30 cm sections along the direction of rise of the roof, one section after another, total 5.4 m long. The outlet air temperature of each section is calculated by solving (eq. 1) (Charron et al., 2005). The outlet air temperature of one section is used as the inlet air temperature for the section following the preceded section. The attic space temperature Tat is assumed to be 10 oC higher than outdoor temperature. A coupled attic model will be developed in the near future. Tpv + Tsf
Tair L+x
⎛
+ ⎜ Tair − L
Tsf + Tpv ⎞
⎝
2
⎟ ⋅e ⎠
2
− x ⋅2 a
Lentrance
(1)
The exterior convective heat transfer coefficient for heat transfer between PV surface and outdoor air is calculated as a function of wind speed (eq. 2) (Kreoth and Bohn, 2001).
0.664 ⋅Re ⋅Pr
otherwise
57.43
(2)
52.86 48.29 43.71 39.14 34.57
5
5
10
15
20
m/s
W/(m^2*K)
30
5
(6)
BIPV/T Air Oultet (v=0.8m/s,To=30C,I=900W/m^2)
10
0
−1
62
10
0
(5)
Regulating the air velocity controls the the outlet air temperature. This is necessary for the purpose of having air at different temperature for different usages, and for maximizing the useful amount of heat collected. The flow velocity of the air under the PV will vary from a minimum of 0.4 m/s to a maximum of about 0.8 m/s.
4 5
1 3
Dh Hgap
−2⎞ ⎛ ⎜ 3 ⎟ 3.657 + 0.0668 ⋅Gz ⋅⎝ 0.04 + Gz ⎠
Temperature (C)
1 2
(4)
1 3
⎞ ⎟ 5 0.036 ⋅Prair ⎝ Re − 23200 ⎠ if Re > 5 ⋅10
Nu
0.034 ⋅Re⋅Prair⋅Dh
Re⋅Prair⋅
Gz
Nu
where a = M air ⋅ C air W ⋅ hc
1⎛ 3⎜
The entire flow path, 5.4 m long, is within the entrance region. The convective heat transfer coefficient for the heat transfer between passing air and the two surfaces (PV bottom and roof surface) is calculated using equations 4 to 6. A correlation (Kreith, 2001) for the average Nu number is employed. For air velocity at 0.5 m/s, the hc is 8.4 W/m2·K.
0
0.6
1.2
1.8
2.4
3
3.6
4.2
4.8
5.4
Distance from Inlet (m)
Figure 6. Air temperature rise (extreme condition in summer).
0 25
Hour of the Day
BIPV/T Air Oultet (v=0.5m/s,To=-13C,I=900W/m^2) 29
Convective Heat Transfer Coefficent Wind Speed (mid-height of roof)
Figure 5.BIPV/T exterior convective heat transfer coefficient as a function of wind speed
Temperature (C)
23 17 11 5 1 7
The sky temperature for radiative heat transfer calculation is a function of outdoor dry bulb and dew point temperature (eq. 3) (Duffie and Beckman, 1980).
Tsky time
Tdp − 273 ⎞ ⎛⎜ ⎟ time To ⋅⎜ 0.8 + ⎟ time ⎝ 250 ⎠
13
0
0.6
1.2
1.8
2.4
3
3.6
4.2
4.8
5.4
Distance from Inlet (m)
Figure 7. Air temperature rise (clear day, end of February)
0.25
(3)
Inside the BIPV/T cavity, when the air velocity ranges from 0.4 to 0.8 m/s, the air flow is in transitional range.
When the air velocity is at 0.8 m/s, the outdoor temperature is 30 oC, and the solar radiation is 900 W/m2, the heat recovered (relative to outdoor
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007 temperature) is about 12 kW, i.e. four times the electricity generated which is about 3 kW at solar noon. This is very typical of the BIPV/T system, but results are sensitive to the exterior film coefficient hc. In this extreme case (Figure 6), the air exits the top of the cavity is at 62 oC, i.e. 32 oC over the ambient temperature. Fig. 7 shows the result with exterior hc of 5 W/(m2·K). A temperature rise of over 40 oC is achievable even when outdoor temperature is -13 oC. On a clear cold day, approximately 15-20 kWh would be the useful thermal energy collected. Basement Concrete Slab Simulation A three-dimensional finite control volume numerical analysis is performed for the basement ventilated concrete slab. Ground temperature is assumed to be 12 o C constant. The insulation between the and steel deck is RSI 2. The physical properties of concrete are assumed to be as follows: specific heat is 920 J/(kg·K), density is 2300 kg/m3, conductivity is 1.9 W/(m·K).
89
90
60 75
76
64
38
Unit in mm
115
Figure 8. Conversion of the actual section to Modeling Section
Ax
St
For the calculations of the convection heat transfer coefficients inside the channel cavity, Colburn’s analogy equation is employed. 1
Nu =
f Re⋅ Pr 3 8
(7)
k Dh
(8)
hc = Nu ⋅
The calculation of the Darcy friction factor (f) for turbulent flows uses an interpolation formula Eq. (9) (Colebrook, 1939), which matches the data in the Moody chart. ⎛ε ⎜ Dh 2.51 1 = −2 ⋅ log⎜ + 3 . 7 f ⋅ f Re ⎜ ⎝
⎞ ⎟ ⎟ ⎟ ⎠
(9)
At conditions of air velocity of 0.5 m/s passing 3 meter long channels, one channel unit of the 10-cm thick concrete slab stores 0.217 kWh thermal energy from BIPV/T air; while, 6-cm concrete slab stores 0.212 kWh. For 15-cm and 20-cm concrete slabs, simulation shows that increasing mass thickness from 10cm to 20cm has very little increase in the total amount of heat stored (additional 0.001 kWh per 5 cm).
ep
Step
Sc
length of the slab is expected. For this individual simulation, assumptions of boundary conditions are as follow: basement temperature is 19 oC constant. The combined heat transfer coefficient between slab surface and room air is 9 W/m2·K, constant. Slab modeling is performed for half channel. The discretization of the half channel is shown in Fig. 9. The distance between nodes is 15 mm in X and Y directions, and 60 mm in Z direction. It is assumed that 40 oC entering air is passing through the channels for 4 hours. This situation represents the available heat from BIPV/T system on a mild winter clear day. Different combinations of concrete slab thicknesses, air velocities, and entering air temperatures are studied.
S te p
Z X C h a n n e l C a v ity Y
Figure 9. Discretization for half channel In order to study the thermal behavior of the concrete slab under different conditions, a simulation for the ventilated slab is performed with separating the ventilated slab away from the house’s thermal network. The simulation of the floor is fully three dimensional since a significant temperature variation along the
Higher air velocity is desirable in recovering heat from hot air. That is because faster air velocity generates higher hc. The value of hc is approximately linear to air velocity (0.5 m/s air velocity has an hc of 7.1 W/(m2·K); 1m/s has an hc of 13 W/(m2·K); and 20 W/(m2·K) is for 1.5 m/s. When the air channels are placed along the longitudinal direction of the slab, the number of channels is reduced, the cross section area is reduced, and hence, the velocity of air is increased. The length of channels changes from 3 meters to 9 meters. 6-cm concrete slab seems sufficient for optimal utilization of heat from hot air. At the run for 6-cm concrete slab with a channel length of 9m, the
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007 maximum surface temperature is 30.3 oC, which exceeds ASHRAE’s limit of 29 oC for thermal comfort purposes for floor heating which is similar to the present case. For a 10-cm concrete slab, the maximum temperature is 28.6 oC. Fig. 15 shows the temperature distribution of air and slab for the latter case. The heat stored is 0.885 kWh per channel. When concrete has a lower conductivity (e.g. 1.2 W/(m·K)), the upper surface temperature is lower. The amount of energy recovered from hot air is slightly less than for concrete with conductivity 1.9 W/(m·K). Whole House Simulation Outdoor Air Temp.
nodes of the house thermal network.; the calculation is then repeated for all time steps in a similar manner. As can be seen from the temperature profiles in Fig. 17, on sunny days, there is little need for heating during the daytime. Day 39 is preceded by overcast cold days. Day 39 and 40 are very sunny days on which 35.0 and 20.5 kWh thermal energy respectively can be stored into the ventilated slab, respectively. No heating is required for the night between these two days even though the nighttime temperature drops down to -15 o C. Two overcast days with mild cold temperatures follow day 40. No heating is required for these two days.
9 10 R.1o
Solar Heat Gain 1
Solarair Temp.
Q_internal 1
Solar Radiation
6
3 4
Passive Charge Concrete Slab (1)
Ground
8 Q_heating Ventilated Concrete Slab (2)
1
2
BIPV/T
5
7
11 Normal Concrete Slab (3)
12 Ground
Figure 10. 1D Thermal network schematic for the solar house A transient thermal network was developed for the entire house (Fig. 10). 1-D heat transfer are assumed. The simulation data for a 7-day winter period, from day 38 to 44 (Feb. 7th to 13th), are presented here. The weather data are taken from meteorological data of year 1989. The profiles of the outdoor dry bulb temperature and the exterior radiations are shown in Fig. 16. Thermal capacitance of the node 1 (house air) is 20 times its actual value to account for the other interior thermal capacitances (e.g. furniture, brick wall). Exterior combined heat transfer coefficient is assumed to be a constant of 15 W/m2·K. The fresh air ventilation rate is 0.3 ACH, also a constant. A low night heating setpoint of 18 oC is used. The thicknesses of slab 1, 2, 3 are 15 cm, 10 cm, and 10 cm, respectively. The flow chart of the simulation process is shown in Fig. 11. At each time step, the solution begins with BIPV/T system, then ventilated slab, and finally the
Figure 11Algorithm for the whole house simulation Fig. 12 shows the temperatures of room air the concrete slabs’ surfaces for day 40. Room air temperature is within thermally comfortable range. The basement floor slab’s surface temperature almost reaches the thermal comfort limit of 29 oC (ASHRAE, 2005). Energy input from BIPV/T increases the ventilated slab’s surface temperature to 5 oC higher than the basement non-ventilated slab surface. Fig. 13 demonstrates the control of the air velocity in BIPV/T system to achieve the desired air outlet temperature. Outlet air at desirable temperature is achieved by regulating the air velocity. Table 1 Thermal Performance of Ventilated Slab & House Day of the Year
38
39
40
41
42
43
44
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007 Heat Stored in Slab 2 (kWh) House Heating Load (kWh)
35.3
30.6
18.9
0
0
0
6.7
25
0
0
0
0
52.7
43
For cold sunny days, heat recovered from the BIPV/T system contributes a considerable amount of heat for reducing the spacing heating load. Thicker activecharge thermal mass is able to store more thermal energy from BIPV/T system, and to stabilize floor surfaces and room air temperature. We can also notice that the simultaneous thermal energy inputs from the transmitted solar radiation and the BIPV/T system result in high peak floor and room temperature (e.g. day 39). If the thermal mass is not properly sized, overheating may be experienced. 1000
29
800
27
600
25
400
23
200
21
0
2
4
6
8
10
12
14
16
18
20
22
Solar Radiation (W/m^2)
Tempearture (C)
y
31
0 24
Time (hr)
This paper presented some of the distinctive characteristics of the design of a BIPV/T system of a solar house and utilization of the recovered heat. Residential passive and hybrid solar heating technologies can greatly reduce space heating loads. The BIPV/T system is able to harvest a large amount of heat. This heat, if used for spacing heating, should be stored in thermal mass and released slowly into living space in order to avoid instantaneous overheating. The active-charge thermal mass has to be carefully sized and designed. The passive-charge thermal mass can store the heat transmitted through windows. This amount of heat is considerable and depends on the window area. Excessive window area and underdesigned thermal mass will result in overheating. In passive solar building design, each and every component is interrelated. Detailed simulations and integrated designs are important and critical.
Financial support of this work was provided by NSERC through the Solar Buildings Research Network.
Figure 12. Temperature profiles of room air and concrete slabs surfaces on Day 40
NOMENCLATURE Cair
specific heat of air (J/kg·K)
Dh
hydraulic diameter
EGH
energy guide for houses rating
Gz
Graetz number
hc
convection Heat Transfer Coefficient
k
conductivity (W/m·K)
M air
mass flow rate of air (kg/s)
Nu
Nusselt number
Re
Reynolds number
S pv
incident solar radiation on PV
Tsf
roof surface temperature (inside BIPV/T)
Tdp
outdoor dew point temperature
1 0.8 0.6 0.4 0.2 7
8
9
10
11
12
13
14
15
16
17
18
Air Velocity (m/s)
Temperature (C)
CONCLUSION
ACKNOWLEDGEMENTS
Room Air Slab 1 (Ground Floor Slab) Surface Slab 2 (Basement Ventilated Slab) Surface Slab 3 (Basement Normal Slab) Surface Direct Normal Radiation Diffuse Horizontal Radiation
46 39 32 25 18 11 4 3 10 17 24
quantity of solar radiation transmitted through windows may cause overheating inside living space. Concrete slab surface temperature may also exceed allowable limit due to over-charge by the solar radiation. Window sunlight shading automatic control is recommended for future work.
0 19
Time (hr) BIPV/T Outlet Air Outdoor Air Slab 2 (Basement Ventilated Slab) Surface BIPV/T Air Velocity
Figure 13. BIPV/T control and outlet air temperature on Day 40 Simulation also reveals that the incoming solar radiation through windows should be controlled. Even on winter days with mild cold temperatures, a large
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007
T pv
PV surface temperature
Tsky
effective sky temperature
W
width of cavity
X
distance from inlet
ε
roughness (m)
REFERENCES Athienitis, A. K., 1997. Theoretical Investigation of Thermal Performance of Passive Solar Building with Floor Radiant Heating, Journal Solar Energy 1997, Issue 61, No. 5, 337-345. Athienitis, A. K. and Santamouris, M., 2002. Thermal Analysis and Design of Passive Solar Buildings, James & James Ltd, London, UK American Concrete Institute (ACI), 2005. ACI 122R02 Guide to Thermal Properties of Concrete and Masonry Systems, Manual of Concrete Practice, Part 1. American Society of Heating, Refrigerating, and Air Conditioning Engineers, Inc. (ASHRAE), 2005. ASHREA Handbooks, Fundamentals. Bilgen, E. and Richard, M.-A., 2002. Horizontal Concrete Slabs as Passive Solar Collectors, Solar Energy, 2002, Vol. 72, No. 5, pp. 405–413. Braham, G.D., 2000. Mechanical Ventilation and Fabric Thermal Storage, Indoor Built Environ, 2000, Issue 9, pp. 102-110. CANMET Energy Technology Centre - Varennes (CETC-Varennes), Natural Resources Canada
Charron, R., and Athienitis, A. K., 2005. Optimization of the Performance of Double-façades with Integrated Photovoltaic Panels and Motorized Blinds, Solar Energy, Volume 80, Issue 5, May 2006, Pages 482-491. Colebrook, C. F., 1939. Turbulent Flow in Pipes, with Particular Reference to the Transition between the Smooth and Rough Pipe Laws, J. Inst. Civ. Eng. Long., vol. 11, 1938-1939, pp. 133-156. Duffie and Beckman, 1980, cited by Davies, M. G., 2004. Building Heat Transfer, John Wiley & Sons Ltd, Chichester, West Sussex, UK. Eicker, Ursula, 2003. Solar Technologies for Buildings, John Wiley & sons Ltd, Chichester, West Sussex, UK. Kreith, F. and Bohn, M. B., 2001. Principles of Heat Transfer – 6th ed., Brooks/Cole, Pacific Grove, CA, USA. NRCan, 2003, HOT2000: A Comprehensive Tool for the Design of Energy Efficient Homes and Buildings, Version 9.1, Natural Resources Canada. www.buildingsgroup.nrcan.gc.ca/software/hot200 0_e.html. NRCan, 2005b. “R-2000 Standard,” 2005 Edition (April 1, 2005). NRCan, 2006, (www.retscreen.net).
RETScreen
Software
Mathsoft Engineering & Education, Inc. (MEEI), MathCad, Boston, USA, 2001 Statistics Canada, CANSIM, tables 128-0002 and 1280009 and Catalogue no. 57-003-X.
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007 BIPV/T System
Ourdoor Air Inlet
Potable Water Variable Speed Fan
Desuperheater from Heatpump
Supply Air HRV Return Air
Fresh Air
Geothermal Heatpump (source is well water)
Non-potable Water
Dryer
Passive Charge Slab (direct solar gain)
Exhausted Air
A/W Heat Exchanger
Ventilated Slab Circulator Air Flow Direction Water Flow Direction Damper
Exhausted
Drain Water
DHW
DHW Tank
Electrical Heater
Drain Water Heat Recovery
Preheat Tank
Well Water
Figure 14. Schematic for house’s service system
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2nd Canadian Solar Buildings Conference Calgary, June 10 – 14, 2007
Temperature (C)
Temperature Distribution along Ventilation Direction (1.5m/s,9m10cm1.9kCnc.) 42 39.5 37 34.5 32 29.5 27 24.5 22 19.5 17
0
0.6
1.2
1.8
2.4
3
3.6
4.2
4.8
5.4
6
6.6
7.2
7.8
8.4
9
Distance from Inlet (m) Slab Surface Temp. Cavity Top Concrete Temp. Air Temp. along Channel
10
1000
3
800
4
600
11
400
18
200
25 38
39
40
41
42
43
Solar Radiation (W/m^2)
Temperature (C)
Figure 15. Spatial temperature distribution along slab
0 45
44
Day of the Year Outdoor Dry Bulb Temperature Direct Normal Radiation Diffuse Horizontal Radiation
Figure 16. Weather profile during the simulation period 33
Temperature (C)
31 29 27 25 23 21 19 17 38
39
40
41
42
43
44
45
Day of the Year Room Air Slab 1 (Ground Floor Slab) Surface Slab 2 (Basement Ventilated Slab) Surface Slab 3 (Basement Normal Slab) Surface Figure 17. Temperature profiles in slab during the simulation period
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