The details of the Photovoltaic Thermal  (PVT) hybrid air heating system, UTC air heating system and its effect on the performance of photovoltaic (PV) module and room temperature in KIER are explained in this paper. Two identical test rooms were constructed such that one had unglazed transpired collector on its south facing wall while other had no solar wall. The temperature inside the room with UTC was 10-20oC higher than the temperature inside the room without UTC on a typical winter day. In second set of experiments, 75W PV modules were installed on the south facing walls of each test rooms.  The temperature of the PV module with UTC was 5-9?lower than the PV module without UTC resulting in a 6% recovery of output electrical power under the forced ventilation. PVT hybrid system may alleviate burden on conventional energy consumption in Korea for heating the buildings and electricity generation

Kang, E. C.

Lee, E. J.

Naveed, A.T.

Texas A&amp;M Repository

ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 Operation of Solar Photovoltaic-Thermal (PVT) Hybrid System in KIER A. T. Naveed  Renewable Energy Specialist RETCan,  426 Tremblay Road, Ottawa, ON, K1G 0C5, Canada.   E. J. Lee   Center Leader Unutilized & Geothermal Energy Center Korea Institute of Energy Research, 71-2 Jang-dong, Daejeon, 305-343, KOREA ejlee@kier.re.kr E. C. Kang  Researcher Korea Institute of Energy Research, 71-2 Jang-dong, Daejeon, 305-343, KOREA  Absract:The details of the Photovoltaic Thermal  (PVT) hybrid air heating system, UTC air heating system and its effect on the performance of photovoltaic (PV) module and room temperature in KIER are explained in this paper. Two identical test rooms were constructed such that one had unglazed transpired collector on its south facing wall while other had no solar wall. The temperature inside the room with UTC was 10-20oC higher than the temperature inside the room without UTC on a typical winter day. In second set of experiments, 75W PV modules were installed on the south facing walls of each test rooms.  The temperature of the PV module with UTC was 5-9 ℃lower than the PV module without UTC resulting in a 6% recovery of output electrical power under the forced ventilation. PVT hybrid system may alleviate burden on conventional energy consumption in Korea for heating the buildings and electricity generation.  1. INTRODUCTION  South Korea is a conventional energy resources deficient country and over 95% of energy requirements are met through imported energy. It is estimated that the primary energy use will increase by 23.61% in 2011 (KEEI, 2005). Therefore, it is imperative to utilize renewable energy sources to gain more energy independence, and meet ever increasing conventional energy prices and obligations of climatic change conventions. More than fifty percent of the total energy consumption is in the industrial sector whereas 25% is used in the buildings. Due to extreme cold climatic conditions in winter, half of the energy consumed in buildings is for heating. Thus, using alternative heating source other than the conventional energy sources is expected to reduce the burden on the national exchequer used for importing energy sources. The yearly averaged daily solar radiation on horizontal surfaces in South Korea is 3.56kWh/m2/day (Jo et al, 2002) and it can play an important load in reducing the building heating load as well as generate electricity using PV modules.  Unglazed Transpired solar Collector (UTC) air heating system utilizes solar energy for building ventilating and heating in winter. It uses air instead of water as heat transfer medium therefore it is free from any risk which may arise due to possible water freezing during winter in the water heating systems. UTC system is easy to install and less costly as compared to glazed solar thermal collectors (Hollick, 1994). Photovoltaic Thermal (PVT) hybrid systems can generate electricity using photovoltaic modules and thermal energy using the solar thermal collector at the same time (Hegazy, 2000).  The energy yield per square meter is improved and the system requires less area for installation as compared to its individual components. It is more important in the urban areas where the availability of land or space for the installation of solar collectors (photovoltaic or thermal) is a problem. In this paper the operation of PVT hybrid air heating system in Korea Institute of Energy Research (KIER) is described and characterized under transient conditions. The effect of the photovoltaic module on the thermal performance of UTC and effect of UTC on the electrical performance of PV are studied by using three different configurations. First configuration consists of UTC air heating system. Second configuration uses PV module with UTC air heating system and third configuration utilizes PV without UTC.  The ESL-IC-06-11-288 Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 thermal and electrical performances of UTC and PVT hybrid system are monitored and results are presented.   2. UTC AIR HEATING SYSTEM   Fig. 1.  Identical test rooms for monitoring UTC performance            Fig. 2.  Schematic of UTC air heating system in KIER Two identical rooms have been chosen for the performance monitoring and verification UTC performance.  The twin test rooms used in the experiment are shown in figure 1. Each test room is 2.7m wide, 2.8m high and 2.4m deep. The thermal and physical characteristics of the room are given in Table 1.  Unglazed transpired solar collector made of corrugated steel absorber sheet with perforations covering 1% of its surface area was fixed to the south-facing wall of the room. The area of the UTC was 6.48m2 with a 0.1m plenum connected by a fan inside the room for heated air circulation or ventilation purposes.  The gap between the UTC and wall was covered on all sides. An opening was made in the center near the ceiling to draw the outside air into the room using a fan (Figures 1 and 2). The schematic of operating principle of the UTC air heating system is shown in figure 2.  Selective solar paint is coated on the surface of the UTC to absorb the incident solar radiation. The temperature of air entering the plenum is increased by heat transfer through conduction and convection from the UTC front, back surfaces and through the holes. The UTC has a large number of small holes so that when the fan is operated  the outer air inflows into the air gap through the holes, it absorbs heat by convection before it enters the room. The heat losses to the surrounding by convection are negligible for large area UTC and air flow rate or approach velocity higher than 0.02m/s (Dymond and Kutscher, 1997).  Tab. 1.Characteristics and Dimensions of the two Test rooms SuFan Solar Room TplenTamb UTCPlenumWarm air ( )p plen ambthTmc T TAGρη −= &   (1) The energy conversion efficiency ηth is defined as the heat transferred to the air volume over the solar radiated heat added to the UTC and it can be expressed as (Summers 1995): Where GT is the total global solar radiation incident in the plane of the UTC.  the density (ρ) and specific heat of air (Cp) was given as 1.15 kg/m3 and 1,007 J/kgoC respectively for each temperature. The mass flow rate ( ) can be written as: m&Dimension 2.7m × 2.8m × 2.4m Volume 18.14 m3 Wall area 41.52 m2  Building Floor area 7.56 m2 Conductivity  (W/m-k) 194 Steel module Thickness (m) 0.02 Conductivity  (W/m-k) 0.047  Wall MaterialUrethane foam Thickness (m) 0.075 U 1.65 kJ/hr oC UA 68.51 kJ/hr m2 oC Thermal properties CAP 17039.18 kJ/ oC Dimensions 2.7 x 2.4 m2 Area 6.48m2 Pitch 20mm Hole diameter 1.65mm Plenum depth 0.1m Absorptivity 0.93 Emissivity 0.89  Porosity 1% ESL-IC-06-11-288 Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 m VA=&     (2) Where approach velocity (V) is defined as a specific air flow rates per unit area, which is simply fan air flow rate divided by collector area ‘A’.   The measurement of solar radiation was made by Eplab’s PSP (Precision Spectral Pyranometer) installed at the south wall of the experimental building so that it could measure the total global solar radiation incident on the UTC surface. The outer building temperature and UTC air heating system plenum temperature and the inner building temperature were measured by T-type thermocouple (Omega, USA). The fan was operated at a flow rate of 110CFM to draw the warm air into the room.  3. PVT HYBRID AIR HEATING SYSTEM Two PV modules of 75W output power each manufactured by S-Energy Co. Ltd have been used in two different configurations. The first one is a typical PV without UTC configuration in which PV module is mounted directly on the south facing wall of a room as shown in figure 3. The characteristics of the PV modules are given in Table 2.   Fig. 3.  Twin test rooms for PVT hybrid air heating system performance monitoring.  Tab.2. Electrical Parameters of 75W PV Module Used in the PVT Hybrid Air Heating System at 25oC and 1000W/m2. Maximum Power (Pmax) 75W Voltage at Pmax (Vmp) 17.3V Current at Pmax (Imp) 4.35A Short circuit current (Isc) 4.75A Open circuit voltage (Voc) 21.8V Temperature coefficient of Power 0.5±0.0.5%/oC Total number of solar cells  36 Number of cells in series 36 In the second configuration, PV module without the frame was mounted on the UTC.  The junction box behind the PV modules might have caused some air flow disturbances and make the ventilating airflow at the gap turbulent in nature. The PVT hybrid air heating system setup is shown in figure 3 and figure 4.      Fig. 4.  Schematic of PVT hybrid air heating system in KIER The electrical conversion efficiency (ηelec) of the PV module is given by: mp mpI  VelecPV TA Gη =    (3) where Imp and Vmp are the current and voltages of the PV module at the maximum power point. Apv is the area of the PV module.  The combined effeiciney of the PVT system can be written as: th elecη η η= +    (4) The dimensions and characteristics of both the south facing walls and the rooms are the same as listed in Table 1. The electric output power of the PV was recorded for both systems using a data logging system under the same measurement conditions such as solar radiation and ambient temperatures. For the present experimental work, the airflow rate was fixed at 160 CFM. The temperature conditions were measured with a Type ‘T’ thermocouple (Omega Co USA). Global irradiance was recorded using a calibrated pyranometer model M11 Kipp and Zonen (Holland) connected with a high–precision millivolt meter and  installed on the south facing wall of the PV without UTC .  The fan in the PVT hybrid system was turned on between 12:00noon and 5:00pm to study the effect of the forced air ventilation on the PV module temperature.  Su PV Fan d lWarm air Solar di tiTaRoom Plenum TlUTCESL-IC-06-11-288 Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4   Fig. 5. Temperature variation across the UTC under forced ventilation The effectiveness of heat extraction from the back of the PV module will depend on the position of the PV module on the SW. It is desired to place the PV module at a position where the temperature is the lowest so that maximum heat could be removed from the PV module.  The UTC air heating system without the PV module was simulated using Phoenix simulation software to find out the temperature distribution over the area of the UTC. The simulation results are shown in figure 5.  The temperature is higher on the right and left edges of the UTC but it is lower in the central region. The temperature is lowest at the position of the ventilation fan. These simulations provided the basis for the most suitable position of the PV module on the UTC to achieve the maximum cooling of the PV module.  4. RESULTS  4.1 Thermal Output Of UTC Air Heating System. The time dependent transient of solar radiation, ambient temperature, plenum temperatures without and with UTC air heating system are shown in figure 6.  Room 1 is the room with UTC air heating system and room 2 is without the UTC. The plenum temperature of the UTC air heating system was as high as 50oC when the incident total global solar radiation on the UTC surface was about 750Wm-2. During this period the temperature inside the room with UTC was as high as 35oC. On the other hand the maximum temperature in the room without UTC was only 10oC.  By using a temperature controller, the room temperature can be maintained at a desired temperature level. The backup heater can be used for heating when the sufficient solar radiation is not available and the indoor temperature is lower than the desired comfort level. -1001020304050600:002:004:006:008:0010:0012:0014:0016:0018:0020:0022:0023:59Local time (hours)Temperature (oC)0100200300400500600700800Solar Radiation (Wm-2)T (room-1)T(ambient)T(plenum)T (room-2)Radiation Fig.6.  Variation of room and ambient temperatures and solar radiation with UTC and without UTC.    4.2 Thermal Output Of PVT Hybrid System. The temperature variations inside the two test rooms along with the ambient temperature and solar radiation measured on a typical winter day are shown in figure 7. Room 1 represents the room with PVT and room 2 is with PV only. The ventilation fan was turned on at 12:00noon was turned off at 17:30 hours. The temperature of the PVT hybrid system room is in the range of 15-20oC from 13:00 to 17:00 hours. After turning off the fan and sunset time, the temperature inside the PVT room is reduced. The air duct drawing the plenum air into the room is not closed although the fan was turned off at 17:30 hour which caused the reduction in the room temperature and it was nearly similar to the ambient temperature outside the room. The maximum temperature inside the room without UTC was 10oC around 14:00 hour and then the room gradually cooled down.  The room temperature is lower in case of PVT hybrid system when compared to the UTC air heating system is due to the reasons that the outside ambient temperature on the day of measurement is zero or below zero degrees Celsius. On the other had, the outside temperature was 0-10oC during the measurements in case of the UTC air heating system. ESL-IC-06-11-288 Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 -1001020304050 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00Local time (horus)Temperature (o C)0100200300400500600700800Radiation (Wm-2 )T (Room 1)T (Ambient)T (Room 2)Solar Radiation Fig. 7. Variation of room temperatures, ambient temperatures and solar radiation in PVT hybrid air heating system and without UTC.   4.3 Electrical Output Of PV Module. The measured electrical power output and the simulated power along with the total solar radiation in the plane of the collector are plotted in figure 8. The experiment was carried out on a typical winter day. The sky was clear during the measurements except few clouds in the early part of the day as is evident from the solar radiation data (Figure 7 and 8).  The measured electrical outputs of the PVT hybrid system and PV without UTC are shown in figure 8 along with the total global solar irradiance in the plane of the PV module.  The electrical outputs of both the PV module were similar before turning on the ventilation fan. However, once the fan was turned on at 12:00noon, the electrical output power of the PVT was increased and it is higher than the electrical power of the PV module without UTC before turning off the fan at 17:30 hours. The PVT electrical output power between 12:30 and 14:00 hours was 57W for PVT case which is about 6% higher as compared to the PV without UTC. The continuous flow of warm air in plenum acts like a cooling source of the PV module resulting in increased output power of the module. The advantages of the PVT option are more obvious during the forced ventilation period as electrical as well as thermal output of the system is higher during this period.  5. CONCLUSIONS The details of UTC air heating system, the PVT hybrid air heating system, and its effect on the performance of PV module and room temperature in KIER are explained in this paper. Two sets of experiments were conducted. In first set of experiments, the thermal performance of the UTC air heating system was monitored using two identical test rooms. The room temperature of the test room with UTC air heating system reached as high as 35oC during the typical day of winter in Korea (figure 6). The averaged outside ambient temperature was 10oC during the day. The maximum temperature inside room without UTC air heating system was 9oC during the day.  010203040506070 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00Local Time (hours)Temperature (oC)0100200300400500600700800Solar Radiation (Wm-2)Power (PV with UTC)Power (PV without UTC)Radiation Fig. 8. The electrical power outputs of PVT hybrid system and PV without UTC along with the incident global solar radiation in the plane of the PV modules. In the second set of experiments, PV module was installed on the south facing walls of identical rooms used in the first experiment. One PV module was installed on the UTC air heating system whereas the second PV module was installed without UTC. Under the forced ventilation conditions, the maximum temperature inside the room with PVT hybrid system was 20oC as compared to 10oC inside the room without UTC (Figure 7). However, the averaged ambient temperature was below 0oC during the day. The temperature of the PV module with UTC was 5-10oC lower than the PV module without UTC resulting in a 6% recovery of output electrical power under the forced ventilation (Figure 8). Thus, it is possible to combine PV and UTC to generate electricity and warm air for building heating at the same time. The heating of buildings in Korea by renewable energy technologies such as PVT may help to reduce the conventional energy consumption for heating in winter and generate electricity simultaneously.  ESL-IC-06-11-288 Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4  6. ACKNOWLEDGMENTS One of the authors, A. T. Naveed would like to acknowledge the technical and financial support provided by KIER and KOSEF to undertake the present research work. REFERENCES [1] Dymond C, Kutscher C. 1997. Development of a flow distribution and design model for transpired solar collectors. Solar Energy, 60, 291-300. [2] Hegazy A. 2000. Comparative study of the performances of four photovoltaic/thermal solar air collectors. Energy Conversion and Management; 41, 861-881. [3] Hollick JC. 1994. Unglazed solar wall air heaters. Renewable Energy, 5, 415-421. [4] Jo DK, Auh CM, Jeon MS, Joo HK, Lee SM, Chu IS. 2002. Evaluation and analysis of domestic solar radiation resources and development of its measurement techniques. KIER Tech. Report KIER-A24507. [5] KEEI (Korea Energy Economics Institute). 2005. Energy consumption survey. Ministry of Commence, Industry and Energy: Korea. [6] Summers D N, 1995, Thermal Simulation and Economic Assessment of Unglazed Transpired Collector Systems, University of Wisconsin-Madison.      ESL-IC-06-11-288 Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 

Operation o Solar Photovoltaic-Thermal (PVT) Hybrid System in KIER

Texas A&M University

ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 
Operation of Solar Photovoltaic-Thermal (PVT) Hybrid System in KIER 
A. T. Naveed  
Renewable Energy 
Specialist 
RETCan,  
426 Tremblay Road, 
Ottawa, ON, K1G 0C5, 
Canada.  
 
E. J. Lee   
Center Leader 
Unutilized & Geothermal 
Energy Center 
Korea Institute of Energy 
Research, 71-2 Jang-dong, 
Daejeon, 305-343, KOREA 
ejlee@kier.re.kr 
E. C. Kang  
Researcher 
Korea Institute of Energy 
Research, 71-2 Jang-dong, 
Daejeon, 305-343, KOREA 
 
Absract:The details of the Photovoltaic Thermal  
(PVT) hybrid air heating system, UTC air heating sys
tem and its effect on the performance of photovoltaic 
(PV) module and room temperature in KIER are expl
ained in this paper. Two identical test rooms were co
nstructed such that one had unglazed transpired colle
ctor on its south facing wall while other had no solar 
wall. The temperature inside the room with UTC was 
10-
20oC higher than the temperature inside the room wit
hout UTC on a typical winter day. In second set of ex
periments, 75W PV modules were installed on the so
uth facing walls of each test rooms.  The temperature 
of the PV module with UTC was 5-9 ℃
lower than the PV module without UTC resulting in a
 6% recovery of output electrical power under the for
ced ventilation. PVT hybrid system may alleviate bur
den on conventional energy consumption in Korea fo
r heating the buildings and electricity generation. 
 
1. INTRODUCTION 
 South Korea is a conventional energy resources 
deficient country and over 95% of energy 
requirements are met through imported energy. It is 
estimated that the primary energy use will increase by 
23.61% in 2011 (KEEI, 2005). Therefore, it is 
imperative to utilize renewable energy sources to gain 
more energy independence, and meet ever increasing 
conventional energy prices and obligations of 
climatic change conventions. More than fifty percent 
of the total energy consumption is in the industrial 
sector whereas 25% is used in the buildings. Due to 
extreme cold climatic conditions in winter, half of the 
energy consumed in buildings is for heating. Thus, 
using alternative heating source other than the 
conventional energy sources is expected to reduce the 
burden on the national exchequer used for importing 
energy sources. The yearly averaged daily solar 
radiation on horizontal surfaces in South Korea is 
3.56kWh/m2/day (Jo et al, 2002) and it can play an 
important load in reducing the building heating load 
as well as generate electricity using PV modules. 
 Unglazed Transpired solar Collector (UTC) air 
heating system utilizes solar energy for building 
ventilating and heating in winter. It uses air instead of 
water as heat transfer medium therefore it is free 
from any risk which may arise due to possible water 
freezing during winter in the water heating systems. 
UTC system is easy to install and less costly as 
compared to glazed solar thermal collectors (Hollick, 
1994). Photovoltaic Thermal (PVT) hybrid systems 
can generate electricity using photovoltaic modules 
and thermal energy using the solar thermal collector 
at the same time (Hegazy, 2000).  The energy yield 
per square meter is improved and the system requires 
less area for installation as compared to its individual 
components. It is more important in the urban areas 
where the availability of land or space for the 
installation of solar collectors (photovoltaic or 
thermal) is a problem. In this paper the operation of 
PVT hybrid air heating system in Korea Institute of 
Energy Research (KIER) is described and 
characterized under transient conditions. The effect of 
the photovoltaic module on the thermal performance 
of UTC and effect of UTC on the electrical 
performance of PV are studied by using three 
different configurations. First configuration consists 
of UTC air heating system. Second configuration 
uses PV module with UTC air heating system and 
third configuration utilizes PV without UTC.  The 
ESL-IC-06-11-288 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 
thermal and electrical performances of UTC and PVT 
hybrid system are monitored and results are presented. 
  
2. UTC AIR HEATING SYSTEM 
 
 
Fig. 1.  Identical test rooms for monitoring 
UTC performance 
 
 
 
 
 
 
 
 
 
 
 
Fig. 2.  Schematic of UTC air heating system in 
KIER 
Two identical rooms have been chosen for the 
performance monitoring and verification UTC 
performance.  The twin test rooms used in the 
experiment are shown in figure 1. Each test room is 
2.7m wide, 2.8m high and 2.4m deep. The thermal 
and physical characteristics of the room are given in 
Table 1.  Unglazed transpired solar collector made of 
corrugated steel absorber sheet with perforations 
covering 1% of its surface area was fixed to the 
south-facing wall of the room. The area of the UTC 
was 6.48m2 with a 0.1m plenum connected by a fan 
inside the room for heated air circulation or 
ventilation purposes.  The gap between the UTC and 
wall was covered on all sides. An opening was made 
in the center near the ceiling to draw the outside air 
into the room using a fan (Figures 1 and 2). 
The schematic of operating principle of the UTC 
air heating system is shown in figure 2.  Selective 
solar paint is coated on the surface of the UTC to 
absorb the incident solar radiation. The temperature 
of air entering the plenum is increased by heat 
transfer through conduction and convection from the 
UTC front, back surfaces and through the holes. The 
UTC has a large number of small holes so that when 
the fan is operated  the outer air inflows into the air 
gap through the holes, it absorbs heat by convection 
before it enters the room. The heat losses to the 
surrounding by convection are negligible for large 
area UTC and air flow rate or approach velocity 
higher than 0.02m/s (Dymond and Kutscher, 1997).  
Tab. 1.Characteristics and Dimensions of the two 
Test rooms 
Su
Fan 
Solar 
Room Tplen
Tamb 
UTC
Plenum
Warm air 
( )p plen amb
th
T
mc T T
AG
ρη −= &   (1) 
The energy conversion efficiency ηth is defined 
as the heat transferred to the air volume over the solar 
radiated heat added to the UTC and it can be 
expressed as (Summers 1995): 
Where GT is the total global solar radiation 
incident in the plane of the UTC.  the density (ρ) and 
specific heat of air (Cp) was given as 1.15 kg/m3 and 
1,007 J/kgoC respectively for each temperature. The 
mass flow rate ( ) can be written as: m&
Dimension 2.7m × 2.8m × 2.4m 
Volume 18.14 m3 
Wall area 41.52 m2 
 
Building 
Floor area 7.56 m2 
Conductivity  
(W/m-k) 194 Steel module 
Thickness (m) 0.02 
Conductivity  
(W/m-k) 0.047 
 
Wall Material
Urethane foam 
Thickness (m) 0.075 
U 1.65 kJ/hr oC 
UA 68.51 kJ/hr m2 oC 
Thermal 
properties 
CAP 17039.18 kJ/ oC 
Dimensions 2.7 x 2.4 m2 
Area 6.48m2 
Pitch 20mm 
Hole diameter 1.65mm 
Plenum depth 0.1m 
Absorptivity 0.93 
Emissivity 0.89 
 
Porosity 1% 
ESL-IC-06-11-288 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 
m VA=&     (2) 
Where approach velocity (V) is defined as a specific 
air flow rates per unit area, which is simply fan air 
flow rate divided by collector area ‘A’.   
The measurement of solar radiation was made by 
Eplab’s PSP (Precision Spectral Pyranometer) 
installed at the south wall of the experimental 
building so that it could measure the total global solar 
radiation incident on the UTC surface. The outer 
building temperature and UTC air heating system 
plenum temperature and the inner building 
temperature were measured by T-type thermocouple 
(Omega, USA). The fan was operated at a flow rate 
of 110CFM to draw the warm air into the room. 
 
3. PVT HYBRID AIR HEATING SYSTEM 
Two PV modules of 75W output power each 
manufactured by S-Energy Co. Ltd have been used in 
two different configurations. The first one is a typical 
PV without UTC configuration in which PV module 
is mounted directly on the south facing wall of a 
room as shown in figure 3. The characteristics of the 
PV modules are given in Table 2.  
 
Fig. 3.  Twin test rooms for PVT hybrid air 
heating system performance monitoring. 
 
Tab.2. Electrical Parameters of 75W PV Module 
Used in the PVT Hybrid Air Heating 
System at 25oC and 1000W/m2. 
Maximum Power (Pmax) 75W 
Voltage at Pmax (Vmp) 17.3V 
Current at Pmax (Imp) 4.35A 
Short circuit current (Isc) 4.75A 
Open circuit voltage (Voc) 21.8V 
Temperature coefficient of Power 0.5±0.0.5%/oC 
Total number of solar cells  36 
Number of cells in series 36 
In the second configuration, PV module without 
the frame was mounted on the UTC.  The junction 
box behind the PV modules might have caused some 
air flow disturbances and make the ventilating 
airflow at the gap turbulent in nature. The PVT 
hybrid air heating system setup is shown in figure 3 
and figure 4. 
 
    
Fig. 4.  Schematic of PVT hybrid air heating 
system in KIER 
The electrical conversion efficiency (ηelec) of the 
PV module is given by: 
mp mpI  V
elec
PV TA G
η =    (3) 
where Imp and Vmp are the current and voltages of 
the PV module at the maximum power point. Apv is 
the area of the PV module.  The combined effeiciney 
of the PVT system can be written as: 
th elecη η η= +    (4) 
The dimensions and characteristics of both the 
south facing walls and the rooms are the same as 
listed in Table 1. The electric output power of the PV 
was recorded for both systems using a data logging 
system under the same measurement conditions such 
as solar radiation and ambient temperatures. For the 
present experimental work, the airflow rate was fixed 
at 160 CFM. The temperature conditions were 
measured with a Type ‘T’ thermocouple (Omega Co 
USA). Global irradiance was recorded using a 
calibrated pyranometer model M11 Kipp and Zonen 
(Holland) connected with a high–precision millivolt 
meter and  installed on the south facing wall of the 
PV without UTC .  The fan in the PVT hybrid system 
was turned on between 12:00noon and 5:00pm to 
study the effect of the forced air ventilation on the PV 
module temperature.  
Su PV 
Fan d l
Warm air 
Solar 
di ti
Ta
Room Plenum T
l
UTC
ESL-IC-06-11-288 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 
 
 
Fig. 5. Temperature variation across the 
UTC under forced ventilation 
The effectiveness of heat extraction from the 
back of the PV module will depend on the position of 
the PV module on the SW. It is desired to place the 
PV module at a position where the temperature is the 
lowest so that maximum heat could be removed from 
the PV module.  The UTC air heating system without 
the PV module was simulated using Phoenix 
simulation software to find out the temperature 
distribution over the area of the UTC. The simulation 
results are shown in figure 5.  The temperature is 
higher on the right and left edges of the UTC but it is 
lower in the central region. The temperature is lowest 
at the position of the ventilation fan. These 
simulations provided the basis for the most suitable 
position of the PV module on the UTC to achieve the 
maximum cooling of the PV module. 
 
4. RESULTS 
 
4.1 Thermal Output Of UTC Air Heating System. 
The time dependent transient of solar radiation, 
ambient temperature, plenum temperatures without 
and with UTC air heating system are shown in figure 
6.  Room 1 is the room with UTC air heating system 
and room 2 is without the UTC. The plenum 
temperature of the UTC air heating system was as 
high as 50oC when the incident total global solar 
radiation on the UTC surface was about 750Wm-2. 
During this period the temperature inside the room 
with UTC was as high as 35oC. On the other hand the 
maximum temperature in the room without UTC was 
only 10oC.  By using a temperature controller, the 
room temperature can be maintained at a desired 
temperature level. The backup heater can be used for 
heating when the sufficient solar radiation is not 
available and the indoor temperature is lower than the 
desired comfort level. 
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T(plenum)
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Radiation
 
Fig.6.  Variation of room and ambient 
temperatures and solar radiation with 
UTC and without UTC.   
 
4.2 Thermal Output Of PVT Hybrid System. 
The temperature variations inside the two test 
rooms along with the ambient temperature and solar 
radiation measured on a typical winter day are shown 
in figure 7. Room 1 represents the room with PVT 
and room 2 is with PV only. The ventilation fan was 
turned on at 12:00noon was turned off at 17:30 hours. 
The temperature of the PVT hybrid system room is in 
the range of 15-20oC from 13:00 to 17:00 hours. 
After turning off the fan and sunset time, the 
temperature inside the PVT room is reduced. The air 
duct drawing the plenum air into the room is not 
closed although the fan was turned off at 17:30 hour 
which caused the reduction in the room temperature 
and it was nearly similar to the ambient temperature 
outside the room. The maximum temperature inside 
the room without UTC was 10oC around 14:00 hour 
and then the room gradually cooled down.  The room 
temperature is lower in case of PVT hybrid system 
when compared to the UTC air heating system is due 
to the reasons that the outside ambient temperature on 
the day of measurement is zero or below zero degrees 
Celsius. On the other had, the outside temperature 
was 0-10oC during the measurements in case of the 
UTC air heating system. 
ESL-IC-06-11-288 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 
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Fig. 7. Variation of room temperatures, 
ambient temperatures and solar 
radiation in PVT hybrid air heating 
system and without UTC. 
 
 
4.3 Electrical Output Of PV Module. 
The measured electrical power output and the 
simulated power along with the total solar radiation 
in the plane of the collector are plotted in figure 8. 
The experiment was carried out on a typical winter 
day. The sky was clear during the measurements 
except few clouds in the early part of the day as is 
evident from the solar radiation data (Figure 7 and 8).  
The measured electrical outputs of the PVT hybrid 
system and PV without UTC are shown in figure 8 
along with the total global solar irradiance in the 
plane of the PV module.  The electrical outputs of 
both the PV module were similar before turning on 
the ventilation fan. However, once the fan was turned 
on at 12:00noon, the electrical output power of the 
PVT was increased and it is higher than the electrical 
power of the PV module without UTC before turning 
off the fan at 17:30 hours. The PVT electrical output 
power between 12:30 and 14:00 hours was 57W for 
PVT case which is about 6% higher as compared to 
the PV without UTC. The continuous flow of warm 
air in plenum acts like a cooling source of the PV 
module resulting in increased output power of the 
module. The advantages of the PVT option are more 
obvious during the forced ventilation period as 
electrical as well as thermal output of the system is 
higher during this period. 
 
5. CONCLUSIONS 
The details of UTC air heating system, the PVT 
hybrid air heating system, and its effect on the 
performance of PV module and room temperature in 
KIER are explained in this paper. Two sets of 
experiments were conducted. In first set of 
experiments, the thermal performance of the UTC air 
heating system was monitored using two identical 
test rooms. The room temperature of the test room 
with UTC air heating system reached as high as 35oC 
during the typical day of winter in Korea (figure 6). 
The averaged outside ambient temperature was 10oC 
during the day. The maximum temperature inside 
room without UTC air heating system was 9oC during 
the day.  
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Power (PV without UTC)
Radiation
 
Fig. 8. The electrical power outputs of PVT 
hybrid system and PV without UTC 
along with the incident global solar 
radiation in the plane of the PV modules. 
In the second set of experiments, PV module was 
installed on the south facing walls of identical rooms 
used in the first experiment. One PV module was 
installed on the UTC air heating system whereas the 
second PV module was installed without UTC. Under 
the forced ventilation conditions, the maximum 
temperature inside the room with PVT hybrid system 
was 20oC as compared to 10oC inside the room 
without UTC (Figure 7). However, the averaged 
ambient temperature was below 0oC during the day. 
The temperature of the PV module with UTC was 5-
10oC lower than the PV module without UTC 
resulting in a 6% recovery of output electrical power 
under the forced ventilation (Figure 8). Thus, it is 
possible to combine PV and UTC to generate 
electricity and warm air for building heating at the 
same time. The heating of buildings in Korea by 
renewable energy technologies such as PVT may 
help to reduce the conventional energy consumption 
for heating in winter and generate electricity 
simultaneously.  
ESL-IC-06-11-288 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China                                    Renewable Energy Resources and a Greener Future, Vol.VIII-7-4 
 
6. ACKNOWLEDGMENTS 
One of the authors, A. T. Naveed would like to 
acknowledge the technical and financial support 
provided by KIER and KOSEF to undertake the 
present research work. 
REFERENCES 
[1] Dymond C, Kutscher C. 1997. Development of a 
flow distribution and design model for transpired 
solar collectors. Solar Energy, 60, 291-300. 
[2] Hegazy A. 2000. Comparative study of the 
performances of four photovoltaic/thermal solar 
air collectors. Energy Conversion and 
Management; 41, 861-881. 
[3] Hollick JC. 1994. Unglazed solar wall air heaters. 
Renewable Energy, 5, 415-421. 
[4] Jo DK, Auh CM, Jeon MS, Joo HK, Lee SM, Chu 
IS. 2002. Evaluation and analysis of domestic 
solar radiation resources and development of its 
measurement techniques. KIER Tech. Report 
KIER-A24507. 
[5] KEEI (Korea Energy Economics Institute). 2005. 
Energy consumption survey. Ministry of 
Commence, Industry and Energy: Korea. 
[6] Summers D N, 1995, Thermal Simulation and 
Economic Assessment of Unglazed Transpired 
Collector Systems, University of Wisconsin-
Madison.  
 
 
 
 
ESL-IC-06-11-288 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 


English

http://oaktrust.library.tamu.edu/bitstream/handle/1969.1/5446/ESL-IC-06-11-288.pdf?sequence=4&isAllowed=y

Operation o Solar Photovoltaic-Thermal (PVT) Hybrid System in KIER

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Operation o Solar Photovoltaic-Thermal (PVT) Hybrid System in KIER

Abstract

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