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Long-therm operation experiences with large-scale solar systems in Slovenia
PERGAMON
Renewable Energy 16 (1999) 6699672
LONG-THERM OPERATION EXPERIENCES WITH LARGE-SCALE SOLAR SYSTEMS IN SLOVENIA C. ARKAR. S. MEDVED and P. NOVAK University of Ljubljana, Faculty of Mechanical Engineering Askerfeva 6, 1000 Ljubljana, Slovenia
ABSTRACT In the early eighties more than 20 large-scale solar systems were installed in Slovenia. The majority of them are used for hot water and swimming pool heating. A lot of systems are in operation for more than 15 years, The overview of the large-scale solar systems in Slovenia is presented. For several systems the conftguration, energy gains, difficulties in the operation and maintenance in years of operation are discussed. 0 1998 Elsevier Science Ltd. All rights reserved.
KEYWORDS Large-scale solar system; solar collector; durability; maintenance; operation experiences
INTRODUCTION Production of solar collectors in Slovenia starts in early eighties. At the beginning there was only one solar collector manufacturer. After 1985 another producer started production of solar collectors. He installed 4 large-scale solar systems. Two of them are presented in this article. In a few years 20 large-scale solar systems have been built, majority of them on Slovenian coastal region. The largest Slovenian solar system, built in 1982, has 372 m’ of solar collectors. In majority of cases the size of the large-scale solar system was selected in a simple way: the efficiency (usually 50%) and average yearly solar radiation (in coastal region 1200 to 1300 kWh/m2year) has been supposed. There was a lack of experiences in solar system design. The difficulty in designing was also the uncertainty of hot water consumption (especially in campgrounds) which was hard to estimate. In a few systems additional auxiliary heaters had to be installed after the first year of operation. Only few design engineers have projected all the big solar systems so a lot of them are similar. Large-scale solar systems have been used exclusively for sanitary water heating’ and heating of hotel swimming pool water. The period between 1980 and 1988 could be named as a “golden period of Slovenian (Yugoslav) tourism”, because the number of tourist was increasing, new hotels were built and nautic tourism was in huge develop. Investments with favorable credits (also for solar systems) were assured and equipment has been free of taxes. After 1990 a great reduction of tourist was noticed which consequently reduced the investments. Solar collectors’ production also drops significantly. At the same time starts a great fluctuation of employees in hotels and also the maintenance staff which care for solar systems operation. Reduced number of guests lowered the money available for maintenance. 0960-1481/99/$-see front matter Q 1998 Elsevier Science Ltd. All rights reserved. PII: SO960-1481(98)00249-3
WREC 1998
670
I4000 12004 I0000 8000
-__-__
__~_
6000 1000 2000 0 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96,'e'Br
Fig. 1. Production of solar collectors and locations of large-scale solar systems in Slovenia.
LARGE-SCALE SOLAR SYSTEMS From the large-scale solar systems presented on Fig. 1 we chose some specific systems which are presented here. Some basic characteristics and significant specificity of each solar system are shown on Table I. Special emphasize have been made on maintenance and troubles in operation. Figures 2 and 3 show six among presented large-scale solar systems.
Fig. 2. Large-scale solar systems at the Adriatic coast; Port Koper container terminal, Hotel Palace, Camp Lucija and Hotel Delfin
WREC 1998
671
Table 1. Basic solar system data and the most important difficulties in solar system operation and durability changes on solar collectors (SC) Solar system location
Year Operation mode
SC No.!Area
(_ &)
HS
(_ m;)
Port Koper wardrobe
1982 summer months
104 145
Port Koper wood warehouse Port Koper container terminal Camp LuclJa Portoroi
1982 summer months 1994 1985 summer months
@ 82 56178 107 150
4 12
1982 seasonallywhen camp open
@ 112
z 5
Hotel Delfin 1982 permanent Izola
266 372
1 50
1997 Hotel Palace 1983 permanent Portoroi until 1993
207 290
3 IO
hlarine Portoroi
ss 120
2 5
1982 permanent
Home Tisje 1985 summer 144 Smartnomonths 255 Litija 1993 permanent 801160 Medical 1985 permanent 32 center 56 Litija
Specific remarks
No.!Vol
4 IO
2 6
4 12
z 3
High absorber paint degradation. 2 SC replaced. 4 repaired. System configuration does not allcw parallel operation of solar system and oil boilers for auxiliary heating. Reduction of employees - hot water consumption dropped slgniticantly last few years (from 1940 m’ in 1983 to 969 m’ in 1994. Solar heat gam: 49 MWh (337 kWh/m’SC) in 1983, 24 MWh (165 kWh/m’SC) in 1995. Often absorber leakage because of irregular SC connection. Hot water consumption dropped last years. New SC field was installed. Very remarkable absorber paint degradation. Small tilt angle (lo’), rain penetration problems. Almost no hot water consumption after 1992. Two identical systems- on the beach and inside the camp. Hot water consumption 3 times larger on the beach. Inside the camp 7 glasses were broken due to vandalism in the first two years. Steel net for SC protection was installed. Significant absorber paint degradation and some untight collectors. Freezing problems m the first years because of uncomplete discharge of water from SC at the end of the season. SC area is integrated into the roof; access to the collectors is almost Impossible. Some SC were not tight; two broken glasses were stlcked and not replaced. Solar heat gam around 200 MWh/year 3 500 kWh/m%C. All absorbers were replaced with selective ones. Untight SC have been simply disconnected. Not in operation since 1993 because of neglected maintenance and unqualified maintaining staff. Higher hot water consumption than expected. Additional electric heaters have been installed into HS. Some broken glasses have been replaced until now. Well maintained system. Not optimal SE orientation, especially because of common morning fog. Few sunny hours in winter due to near forest. New SC were installed and oriented to the SW direction. Very well maintained system. The only system with calorimeter data for all years of operation and the only solar system tested according to IS0 9459-5. Yearly solar heat gain is between 15 and 2 1 MWh (between 260 kWhlm*SC and 370 kWh/m2SC).
WREC
672
1998
Fig. 3. Large-scale solar systems near Ljubljana; Medical center in Litija and Home Tisje in Smattno - Litija
GENERAL REMARKS From the presentation in Table 1 it is obvious that the solar collectors are the most critical elements of the solar system. Solar collectors made before 1987 are generally in bad conditions. Many of them are untight, absorber paint is degradated especially if collectors are exposed to the salty air. Based on these experiences many improvements in construction and paint have been done on today’s solar collectors. No important changes on piping have been observed. They are generally propriatelly thermally insulated. Pumps operate well. only some bearings have been replaced. Heat exchangers which are in contact with sea water (swimming pools) were replaced after few years with new ones. Regulation units work well. Some temperature sensors inside collectors have been replaced. Expansion tanks have been replaced in all systems due to untight membrane. Also gate valves have been replaced with ball valves, especially in wellmaintained systems. Measurement devices failed in operation in most of the systems after one or two years of operanon; nobody replaced them after failure (except in Port Koper). Those systems which are controlled, monitored and maintained by the same staff from the beginning or by the staff which is well educated about the system operation operate well and they are in much better condition than the other large-scale solar systems.
CONCLUSIONS Presentation clearly shows the importance of regular and professional maintenance for reliable operation of large-scale solar systems. Solar collectors’ examination also shows the great influence of exposure to the salty air on casing, absorber paint and sealing deterioration. Parliament of Republic Slovenia accepted the resolution about energy efficiency in 1994 which stresses bigger role of renewable energy. 100.000 m2 of new solar collectors are planned until 2010. These are expected to be mostly installed by private house owners. Concerning large-scale solar systems we estimate that at this moment there are unfortunately no greater possibilities for new large-scale systems especially because of low price of fossil fuels. This could only be changed if in the future energy prices will include social costs and ecological criteria partly replace economics calculations. This will be of a crucial importance for a high quality tourist country what Slovenia wants to become.
REFERENCES Medved, S., Arkar, C., Lavrif, I. and Novak, P. (1995). Large-scale solar heating systems in Slovenia. 1995 Workshop on Large-Scale Solar Heating, Vienna, 1995, pp. Dl-D9
Renewable Energy 16 (1999) 6699672
LONG-THERM OPERATION EXPERIENCES WITH LARGE-SCALE SOLAR SYSTEMS IN SLOVENIA C. ARKAR. S. MEDVED and P. NOVAK University of Ljubljana, Faculty of Mechanical Engineering Askerfeva 6, 1000 Ljubljana, Slovenia
ABSTRACT In the early eighties more than 20 large-scale solar systems were installed in Slovenia. The majority of them are used for hot water and swimming pool heating. A lot of systems are in operation for more than 15 years, The overview of the large-scale solar systems in Slovenia is presented. For several systems the conftguration, energy gains, difficulties in the operation and maintenance in years of operation are discussed. 0 1998 Elsevier Science Ltd. All rights reserved.
KEYWORDS Large-scale solar system; solar collector; durability; maintenance; operation experiences
INTRODUCTION Production of solar collectors in Slovenia starts in early eighties. At the beginning there was only one solar collector manufacturer. After 1985 another producer started production of solar collectors. He installed 4 large-scale solar systems. Two of them are presented in this article. In a few years 20 large-scale solar systems have been built, majority of them on Slovenian coastal region. The largest Slovenian solar system, built in 1982, has 372 m’ of solar collectors. In majority of cases the size of the large-scale solar system was selected in a simple way: the efficiency (usually 50%) and average yearly solar radiation (in coastal region 1200 to 1300 kWh/m2year) has been supposed. There was a lack of experiences in solar system design. The difficulty in designing was also the uncertainty of hot water consumption (especially in campgrounds) which was hard to estimate. In a few systems additional auxiliary heaters had to be installed after the first year of operation. Only few design engineers have projected all the big solar systems so a lot of them are similar. Large-scale solar systems have been used exclusively for sanitary water heating’ and heating of hotel swimming pool water. The period between 1980 and 1988 could be named as a “golden period of Slovenian (Yugoslav) tourism”, because the number of tourist was increasing, new hotels were built and nautic tourism was in huge develop. Investments with favorable credits (also for solar systems) were assured and equipment has been free of taxes. After 1990 a great reduction of tourist was noticed which consequently reduced the investments. Solar collectors’ production also drops significantly. At the same time starts a great fluctuation of employees in hotels and also the maintenance staff which care for solar systems operation. Reduced number of guests lowered the money available for maintenance. 0960-1481/99/$-see front matter Q 1998 Elsevier Science Ltd. All rights reserved. PII: SO960-1481(98)00249-3
WREC 1998
670
I4000 12004 I0000 8000
-__-__
__~_
6000 1000 2000 0 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96,'e'Br
Fig. 1. Production of solar collectors and locations of large-scale solar systems in Slovenia.
LARGE-SCALE SOLAR SYSTEMS From the large-scale solar systems presented on Fig. 1 we chose some specific systems which are presented here. Some basic characteristics and significant specificity of each solar system are shown on Table I. Special emphasize have been made on maintenance and troubles in operation. Figures 2 and 3 show six among presented large-scale solar systems.
Fig. 2. Large-scale solar systems at the Adriatic coast; Port Koper container terminal, Hotel Palace, Camp Lucija and Hotel Delfin
WREC 1998
671
Table 1. Basic solar system data and the most important difficulties in solar system operation and durability changes on solar collectors (SC) Solar system location
Year Operation mode
SC No.!Area
(_ &)
HS
(_ m;)
Port Koper wardrobe
1982 summer months
104 145
Port Koper wood warehouse Port Koper container terminal Camp LuclJa Portoroi
1982 summer months 1994 1985 summer months
@ 82 56178 107 150
4 12
1982 seasonallywhen camp open
@ 112
z 5
Hotel Delfin 1982 permanent Izola
266 372
1 50
1997 Hotel Palace 1983 permanent Portoroi until 1993
207 290
3 IO
hlarine Portoroi
ss 120
2 5
1982 permanent
Home Tisje 1985 summer 144 Smartnomonths 255 Litija 1993 permanent 801160 Medical 1985 permanent 32 center 56 Litija
Specific remarks
No.!Vol
4 IO
2 6
4 12
z 3
High absorber paint degradation. 2 SC replaced. 4 repaired. System configuration does not allcw parallel operation of solar system and oil boilers for auxiliary heating. Reduction of employees - hot water consumption dropped slgniticantly last few years (from 1940 m’ in 1983 to 969 m’ in 1994. Solar heat gam: 49 MWh (337 kWh/m’SC) in 1983, 24 MWh (165 kWh/m’SC) in 1995. Often absorber leakage because of irregular SC connection. Hot water consumption dropped last years. New SC field was installed. Very remarkable absorber paint degradation. Small tilt angle (lo’), rain penetration problems. Almost no hot water consumption after 1992. Two identical systems- on the beach and inside the camp. Hot water consumption 3 times larger on the beach. Inside the camp 7 glasses were broken due to vandalism in the first two years. Steel net for SC protection was installed. Significant absorber paint degradation and some untight collectors. Freezing problems m the first years because of uncomplete discharge of water from SC at the end of the season. SC area is integrated into the roof; access to the collectors is almost Impossible. Some SC were not tight; two broken glasses were stlcked and not replaced. Solar heat gam around 200 MWh/year 3 500 kWh/m%C. All absorbers were replaced with selective ones. Untight SC have been simply disconnected. Not in operation since 1993 because of neglected maintenance and unqualified maintaining staff. Higher hot water consumption than expected. Additional electric heaters have been installed into HS. Some broken glasses have been replaced until now. Well maintained system. Not optimal SE orientation, especially because of common morning fog. Few sunny hours in winter due to near forest. New SC were installed and oriented to the SW direction. Very well maintained system. The only system with calorimeter data for all years of operation and the only solar system tested according to IS0 9459-5. Yearly solar heat gain is between 15 and 2 1 MWh (between 260 kWhlm*SC and 370 kWh/m2SC).
WREC
672
1998
Fig. 3. Large-scale solar systems near Ljubljana; Medical center in Litija and Home Tisje in Smattno - Litija
GENERAL REMARKS From the presentation in Table 1 it is obvious that the solar collectors are the most critical elements of the solar system. Solar collectors made before 1987 are generally in bad conditions. Many of them are untight, absorber paint is degradated especially if collectors are exposed to the salty air. Based on these experiences many improvements in construction and paint have been done on today’s solar collectors. No important changes on piping have been observed. They are generally propriatelly thermally insulated. Pumps operate well. only some bearings have been replaced. Heat exchangers which are in contact with sea water (swimming pools) were replaced after few years with new ones. Regulation units work well. Some temperature sensors inside collectors have been replaced. Expansion tanks have been replaced in all systems due to untight membrane. Also gate valves have been replaced with ball valves, especially in wellmaintained systems. Measurement devices failed in operation in most of the systems after one or two years of operanon; nobody replaced them after failure (except in Port Koper). Those systems which are controlled, monitored and maintained by the same staff from the beginning or by the staff which is well educated about the system operation operate well and they are in much better condition than the other large-scale solar systems.
CONCLUSIONS Presentation clearly shows the importance of regular and professional maintenance for reliable operation of large-scale solar systems. Solar collectors’ examination also shows the great influence of exposure to the salty air on casing, absorber paint and sealing deterioration. Parliament of Republic Slovenia accepted the resolution about energy efficiency in 1994 which stresses bigger role of renewable energy. 100.000 m2 of new solar collectors are planned until 2010. These are expected to be mostly installed by private house owners. Concerning large-scale solar systems we estimate that at this moment there are unfortunately no greater possibilities for new large-scale systems especially because of low price of fossil fuels. This could only be changed if in the future energy prices will include social costs and ecological criteria partly replace economics calculations. This will be of a crucial importance for a high quality tourist country what Slovenia wants to become.
REFERENCES Medved, S., Arkar, C., Lavrif, I. and Novak, P. (1995). Large-scale solar heating systems in Slovenia. 1995 Workshop on Large-Scale Solar Heating, Vienna, 1995, pp. Dl-D9