Optimizing Efficiency of Biomass—Fired Organic Rankine Cycle with Concentrated Solar Power in Denmark

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Zourellis, Andreas; Perers, Bengt; Donneborg, Jes; Matoricz, Jelica Published in: Energy Procedia

Link to article, DOI: 10.1016/j.egypro.2018.08.206

Publication date: 2018

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Citation (APA): Zourellis, A., Perers, B., Donneborg, J., & Matoricz, J. (2018). Optimizing Efficiency of Biomass—Fired Organic Rankine Cycle with Concentrated Solar Power in Denmark. Energy Procedia, 149, 420-426. DOI: 10.1016/j.egypro.2018.08.206

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Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect ScienceDirect AvailableEnergy online Procedia at www.sciencedirect.com00 (2018) 000–000 Available online at www.sciencedirect.com 2 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 Energy Procedia 00 (2018) 000–000 www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia ScienceDirectScienceDirect 1. Introduction EnergyEnergy Procedia Procedia 14900 (20(2018)17) 000420–426–000 Solar energy is abundant and increasingly utilized in domestic systems to supply space heating and cooling. www.elsevier.com/locate/procedia However, over the last couple of decades the world energy demand has increased dramatically due to both industrial 16th International Symposium on District Heating and Cooling, DHC2018, growth and population increase. 16th International9– 12Symposium September on 2018, District Hamburg, Heating Germany and Cooling, DHC2018, 9–12 September 2018, Hamburg, Germany 1.1 Concentrated Solar Power in Denmark

Optimizing Efficiency of Biomass—Fired Organic Rankine Cycle Concentrated solar power (CSP) plants have so far mainly been built to produce electricity for export to the grid, OptimizingThe Efficiency 15th International of Biomass Symposium— onFired District Organic Heating and Rankine Cooling Cycle with Concentrated Solar Power in Denmark however, numerous advantages have been identified in industrial setting as well. Due to the technology’s flexibility with Concentrated Solar Power in Denmark to produce high and mid temperature heat, it provides an ideal solar-thermal solution for industrial purposes. Parabolic Assessing the feasibilitya ofb using the heatc demand-outdoord trough CSP plants are typically found in countries around the solar belt, but economic viability has also been proven Andreas Zourellis *, Bengt Perers , Jes Donneborg and Jelica Matoricz in a place with limited solar resources, in Denmark, where efficiency of the system was monitored and compared with Andreas Zourellisa*, Bengt Perersb, Jes Donneborgc and Jelica Matoriczd temperature functiona,c,d Aalborg for CSP a A/S, long Hjulmagervej-term 55, 9000 district Aalborg, Denmark heat demand forecast flat solar-thermal panels. The report concluded that CSP produces more energy per square meter above 50 °C, provides b Department of Civil Engineering,a,c,d Aalborg CSPTechnical A/S, Hjulmagervej University of 55,Nordvej 9000 Building Aalborg, 119 Denmark, 2800 Kgs. Lyngby, Denmark a better economy over the system’s 25-years lifetime and ensures a year-round energy production even in Nordic a,b,c a a b c c I. Andrib Departmentć of* ,Civil A. Engineering, Pina , P. Technical Ferrão University, J. Fournier of Nordvej Building., B. 119Lacarrière, 2800 Kgs. Lyngby, O., Denmark Le Corre climate conditions compared to flat panel systems [1]. It has also be seen that even when operating in higher temperature the parabolic trough collectors maintain a high heat yield per square meter or aperture area [2], [3]. That a AbstractIN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal is because the heat is concentrated in a central receiver tube enclosed in a vacuum glass envelope. Abstract bVeolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France A first of its kindcDépartement concentrated Systèmes solar Énergétiques power (CSP) et Environnement installation has- IMT been Atlantique integrated, 4 r uetogether Alfred Kastler,with a biomass44300 Nantes, heat andFrance power (CHP) plantA first using of its an kind organic concentrated rankine solarcycle power(ORC) (CSP) unit. Theinstallation plant has has been been deployed integrated in togetherthe north withern parta biomassof Jutland heat inand Denmark, power (C rightHP) plantnext tousing the cityan organic of Brønderslev. rankine cycle The (ORC)plant has unit been. The supplying plant has heatbeen to deployed the local in district the north heatingern part networkof Jutlandsince in the Denmark, end of 2016 right. nextAalborg to the CSP city has of developed Brønderslev. and Thebuilt p thelantCSP has plantbeen supplyingconsisting heatof parabolic to the local trough district collectors heating with network an aperturesince reflectingthe end of area 2016 of. Abstract 26,920Aalborg m CSP2. The has CSP developed plant is and able built to deliverthe CSP 16.6 plant MWth consisting at its of peak parabolic while troughit can supplycollectors the withdistrict an apertureheating orreflecting the ORC area with of approximately26,920 m2. The 16,000 CSP plantMWh isof ableheat toannually. deliver This16.6 paper MWth serves at its as peak a description while it ofcan the supply technical the aspectsdistrict ofheating the system or the with ORC specific with District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the focusapproximately on the CSP 16,000 field MWh as well of as heat present annually. the firstThismeasured paper serves performance as a description from the of Stheummer technical of 2017. aspects of the system with specific greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat focus on the CSP field as well as present the first measured performance from the Summer of 2017. ©sales 2018. DueThe Authors.to the changed Published climate by Elsevier conditions Ltd. and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. This© 2018 is an The open Authors. access Published article under by Elsevierthe CC BY Ltd.Ltd-.NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) ThisThe ismain an open scope access of this article paper under is to assessthe CC the BY-NC-ND feasibility license of using (https://creativecommons.org/licenses/by-nc-nd/4.0/ the heat demand – outdoor temperature function for) heat demand SelectionThis is an andopen peer access-review article under under responsibility the CC BY of-NC the-ND scientific license committee (https://creativecommons.org/licenses/by of the 16th International Symposium-nc-nd/4.0/ on District) Heating Selectionforecast. andThe peer-review district of underAlvalade, responsibility located inof Lisbonthe scientific (Portugal), committee was usedof the as16th a caseInternational study. The Symposium district ison consistedDistrict Heatingof 665 Selectionand Cooling, and DHC2018peer-review. under responsibility of the scientific committee of the 16th International Symposium on District Heating andbuildings Cooling, that DHC2018. vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district and Cooling, DHC2018. Keywords:renovationSolar scenarios Energy, Concentratedwere developed Solar (shallow,Power, CSP, intermediate, Concentrated deep).Solar Heat, To CSH,estimate Solar the-Thermal, error, obtainedIntegrated heatEnergy demand System, values Organic were RankineKeywords:compared Cycle,Solar with ORC, Energy, results Biomass Concentrated from a dynamic Solar heatPower, demand CSP, Concentrated model, previously Solar Heat, developed CSH, Solar and-Thermal, validated Integrated by the authors. Energy System, Organic RankineThe results Cycle, showed ORC, Biomass that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). Figure 1: Parabolic trough collector performance vs. flat plate collectors The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the in low heating temperatures decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and Figure 2: Parabolic trough collector performance in different Danish renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the regions and high temperatures [3] coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

© 2017 The Authors. Published by Elsevier Ltd. 2. Technology description * Corresponding author. Tel.: +45 50 30 00 25 Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and * ECorresponding-mail address: [email protected] Tel.: +45 50 30 00 25 Cooling. 2.1. Parabolic Trough Collectors (PTC) E-mail address: [email protected] 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. Keywords: Heat demand; Forecast; Climate change This1876 -is61 an02 open© 2018 access The article Authors. under Published the CC BYby Elsevier-NC-ND Ltd. license (https://creativecommons.org/licenses/by-nc-nd/4.0/) The parabolic troughs reflect the rays of the sun onto a receiver pipe filled with heat transfer fluid. The receiver SelectionThis is an andopen peer access-review article under under responsibility the CC BY -ofNC the-ND scientific license committee(https://creativecommons.org/licenses/by of the 16th International Symposium-nc-nd/4.0/ on District) Heating and Cooling, pipe is located in the central focal point of the troughs. In the receiver pipe, the fluid is heated up and pumped into the DHC2018Selection and. peer-review under responsibility of the scientific committee of the 16th International Symposium on District Heating and Cooling, heat consumer. DHC2018. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. ThisPeer -isreview an open under access responsibility article under of the the Scientific CC BY-NC-ND Committee license of The 15th(https://creativecommons.org/licenses/by-nc-nd/4.0/ International Symposium on District Heating and Cooling) . Selection and peer-review under responsibility of the scientific committee of the 16th International Symposium on District Heating and Cooling, DHC2018. 10.1016/j.egypro.2018.08.206

10.1016/j.egypro.2018.08.206 1876-6102 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect ScienceDirect Energy Procedia 00 (2018) 000–000 Andreas Zourellis et al. / Energy Procedia 149 (2018) 420–426 421 2 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 Energy Procedia 00 (2018) 000–000 www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia 1. Introduction

Solar energy is abundant and increasingly utilized in domestic systems to supply space heating and cooling. However, over the last couple of decades the world energy demand has increased dramatically due to both industrial 16th International Symposium on District Heating and Cooling, DHC2018, growth and population increase. 16th International9– 12Symposium September on 2018, District Hamburg, Heating Germany and Cooling, DHC2018, 9–12 September 2018, Hamburg, Germany 1.1 Concentrated Solar Power in Denmark Optimizing Efficiency of Biomass—Fired Organic Rankine Cycle Optimizing Efficiency of Biomass—Fired Organic Rankine Cycle Concentrated solar power (CSP) plants have so far mainly been built to produce electricity for export to the grid, with Concentrated Solar Power in Denmark however, numerous advantages have been identified in industrial setting as well. Due to the technology’s flexibility with Concentrated Solar Power in Denmark to produce high and mid temperature heat, it provides an ideal solar-thermal solution for industrial purposes. Parabolic a b c d trough CSP plants are typically found in countries around the solar belt, but economic viability has also been proven Andreas Zourellis *, Bengt Perers , Jes Donneborg and Jelica Matoricz in a place with limited solar resources, in Denmark, where efficiency of the system was monitored and compared with Andreas Zourellisa*, Bengt Perersb, Jes Donneborgc and Jelica Matoriczd a,c,d Aalborg CSP A/S, Hjulmagervej 55, 9000 Aalborg, Denmark flat solar-thermal panels. The report concluded that CSP produces more energy per square meter above 50 °C, provides b Department of Civil Engineering,a,c,d Aalborg CSPTechnical A/S, Hjulmagervej University of 55,Nordvej 9000 Building Aalborg, 119 Denmark, 2800 Kgs. Lyngby, Denmark a better economy over the system’s 25-years lifetime and ensures a year-round energy production even in Nordic b Department of Civil Engineering, Technical University of Nordvej Building 119, 2800 Kgs. Lyngby, Denmark climate conditions compared to flat panel systems [1]. It has also be seen that even when operating in higher temperature the parabolic trough collectors maintain a high heat yield per square meter or aperture area [2], [3]. That Abstract is because the heat is concentrated in a central receiver tube enclosed in a vacuum glass envelope. Abstract A first of its kind concentrated solar power (CSP) installation has been integrated together with a biomass heat and power (CHP) Aplant first using of its an kind organic concentrated rankine solarcycle power(ORC) (CSP) unit. Theinstallation plant has has been been deployed integrated in togetherthe north withern parta biomassof Jutland heat inand Denmark, power (C rightHP) plantnext tousing the cityan organic of Brønderslev. rankine cycle The (ORC)plant has unit been. The supplying plant has heatbeen to deployed the local in district the north heatingern part networkof Jutlandsince in the Denmark, end of 2016 right. nextAalborg to the CSP city has of developed Brønderslev. and Thebuilt p thelantCSP has plantbeen supplyingconsisting heatof parabolic to the local trough district collectors heating with network an aperturesince reflectingthe end of area 2016 of. 26,920Aalborg m CSP2. The has CSP developed plant is and able built to deliverthe CSP 16.6 plant MWth consisting at its of peak parabolic while troughit can supplycollectors the withdistrict an apertureheating orreflecting the ORC area with of approximately26,920 m2. The 16,000 CSP plantMWh isof ableheat toannually. deliver This16.6 paper MWth serves at its as peak a description while it ofcan the supply technical the aspectsdistrict ofheating the system or the with ORC specific with approximatelyfocus on the CSP 16,000 field MWh as well of as heat present annually. the firstThismeasured paper serves performance as a description from the of Stheummer technical of 2017. aspects of the system with specific focus on the CSP field as well as present the first measured performance from the Summer of 2017. © 2018 The Authors. Published by Elsevier Ltd. ©This 2018 is an The open Authors. access Published article under by Elsevierthe CC BY Ltd-.NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) ThisSelection is an andopen peer access-review article under under responsibility the CC BY of-NC the-ND scientific license committee (https://creativecommons.org/licenses/by of the 16th International Symposium-nc-nd/4.0/ on District) Heating Selectionand Cooling, and DHC2018peer-review. under responsibility of the scientific committee of the 16th International Symposium on District Heating and Cooling, DHC2018. Keywords: Solar Energy, Concentrated Solar Power, CSP, Concentrated Solar Heat, CSH, Solar-Thermal, Integrated Energy System, Organic RankineKeywords: Cycle,Solar ORC, Energy, Biomass Concentrated Solar Power, CSP, Concentrated Solar Heat, CSH, Solar-Thermal, Integrated Energy System, Organic Rankine Cycle, ORC, Biomass

Figure 1: Parabolic trough collector performance vs. flat plate collectors in low heating temperatures Figure 2: Parabolic trough collector performance in different Danish regions and high temperatures [3]

2. Technology description * Corresponding author. Tel.: +45 50 30 00 25 * ECorresponding-mail address: [email protected] Tel.: +45 50 30 00 25 2.1. Parabolic Trough Collectors (PTC) E-mail address: [email protected] 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. 187This6 -is61 an02 open© 2018 access The article Authors. under Published the CC BYby Elsevier-NC-ND Ltd. license (https://creativecommons.org/licenses/by-nc-nd/4.0/) The parabolic troughs reflect the rays of the sun onto a receiver pipe filled with heat transfer fluid. The receiver SelectionThis is an andopen peer access-review article under under responsibility the CC BY -ofNC the-ND scientific license committee(https://creativecommons.org/licenses/by of the 16th International Symposium-nc-nd/4.0/ on District) Heating and Cooling, pipe is located in the central focal point of the troughs. In the receiver pipe, the fluid is heated up and pumped into the DHC2018Selection and. peer-review under responsibility of the scientific committee of the 16th International Symposium on District Heating and Cooling, heat consumer. DHC2018. 422 Andreas Zourellis et al. / Energy Procedia 149 (2018) 420–426 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 3 4 Andreas Zourellis / Energy Procedia 00 (2018) 000–000

The CSP technology is the most effective solar heating method for high temperature ranges. The parabolic troughs has a special glass vacuum tube guaranteeing some of the markets lowest heat losses thus providing stable energy production even at middle temperatures as the receiver pipe has very low heat losses to the ambient. The parabolic trough uses a custom–made sun-tracking technology, where a computer calculates and calibrates the troughs into the required position to receive optimal radiation throughout the day. The sun-tracking TM Figure 3: Sun tracking technology enabling the parabolic troughs to follow the sun’s Figure 6: Photo of the AAL-Trough 3.0 model - third generation of position throughout the day technology achieves a very high efficiency per Figure 5: Top view of the solar field layout Aalborg CSP’s parabolic trough technology m2 of aperture mirror area, thereby optimizing the use of land intended for technology The solar energy plant was delivered by Danish renewable energy specialist Aalborg CSP, and it is based on the placement. The PTCs track and follow the sun in a tracking window of ± 0.15° from the present solar position. The company’s own CSP parabolic trough technology, also called the AAL-TroughTM. The plant consists of 40 rows of rotation is ensured by a gear and a hydraulic system. 125m U-shaped mirrors with an aperture area of 26,929 m2. These 40 rows are divided in 10 loops. Each loop has an inlet and outlet connection to the main pipe, meaning that the cold thermal oil will flow through 4 rows (i.e. 500m) 2.2. The system until it gets the right temperature and finally leaves the loop. In order to fit within the land boundaries the loops where bended into half, saving cost for extra piping at the same time. As seen in Figure 5 the solar field is tilted 29o from the In December 2016, a world first CSP plant went into operation in the northern part of Denmark (town of North-South axis due to specific land availability. Brønderslev). The plant’s uniqueness lies in the fact that it was designed to be integrated with a biomass-fired Organic The curved mirrors collect the sunrays throughout the day and reflect them onto a receiver pipe, which sums up to Rankine Cycle (ORC) which is currently still under the last stages of commissioning. This combined solution is the 5 kilometer receiver tubes. This receiver pipe is surrounded by a special glass vacuum tube and inside this runs - only first large-scale system in the world to demonstrate how CSP, with an integrated energy system design can optimize heated by the sun - thermal oil with temperatures up to 312 °C. This high temperature is able to drive an electric efficiency of ORC even in areas with less sunshine, in this case Denmark. turbine to produce electricity, but the flexibility of the system also allows production of lower temperatures for district heating purposes. The solar heating system can thus alternate between providing heat and power or deliver heat exclusively. To maximize yield of energy, the waste heat is utilized and sent to the district heating circuit whereas electrical power is generated at peak price periods. In Figure 7, it can be seen that the CSP field is delivering hot thermal oil to both the ORC unit and the oil-to-water heat exchanger which delivers the heat to the district heating network to the city of Brønderslev. The CSP Figure 4: Image of the concentrated solar power plant in Brønderslev, Denmark solar field has a thermal peak effect of 16.6 MWth and is expected to deliver approximately 16,000 MWh of heat in an average weather year. Apart from the solar field, there are two biomass boilers each of a maximum capacity of 10 MWth Figure 7: Flow chart of the energy distribution at the hybrid plant of Brønderslev running with wood chips as fuel. Andreas Zourellis et al. / Energy Procedia 149 (2018) 420–426 423 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 3 4 Andreas Zourellis / Energy Procedia 00 (2018) 000–000

The CSP technology is the most effective solar heating method for high temperature ranges. The parabolic troughs has a special glass vacuum tube guaranteeing some of the markets lowest heat losses thus providing stable energy production even at middle temperatures as the receiver pipe has very low heat losses to the ambient. The parabolic trough uses a custom–made sun-tracking technology, where a computer calculates and calibrates the troughs into the required position to receive optimal radiation throughout the day. The sun-tracking TM Figure 3: Sun tracking technology enabling the parabolic troughs to follow the sun’s Figure 6: Photo of the AAL-Trough 3.0 model - third generation of position throughout the day technology achieves a very high efficiency per Figure 5: Top view of the solar field layout Aalborg CSP’s parabolic trough technology m2 of aperture mirror area, thereby optimizing the use of land intended for technology The solar energy plant was delivered by Danish renewable energy specialist Aalborg CSP, and it is based on the placement. The PTCs track and follow the sun in a tracking window of ± 0.15° from the present solar position. The company’s own CSP parabolic trough technology, also called the AAL-TroughTM. The plant consists of 40 rows of rotation is ensured by a gear and a hydraulic system. 125m U-shaped mirrors with an aperture area of 26,929 m2. These 40 rows are divided in 10 loops. Each loop has an inlet and outlet connection to the main pipe, meaning that the cold thermal oil will flow through 4 rows (i.e. 500m) 2.2. The system until it gets the right temperature and finally leaves the loop. In order to fit within the land boundaries the loops where bended into half, saving cost for extra piping at the same time. As seen in Figure 5 the solar field is tilted 29o from the In December 2016, a world first CSP plant went into operation in the northern part of Denmark (town of North-South axis due to specific land availability. Brønderslev). The plant’s uniqueness lies in the fact that it was designed to be integrated with a biomass-fired Organic The curved mirrors collect the sunrays throughout the day and reflect them onto a receiver pipe, which sums up to Rankine Cycle (ORC) which is currently still under the last stages of commissioning. This combined solution is the 5 kilometer receiver tubes. This receiver pipe is surrounded by a special glass vacuum tube and inside this runs - only first large-scale system in the world to demonstrate how CSP, with an integrated energy system design can optimize heated by the sun - thermal oil with temperatures up to 312 °C. This high temperature is able to drive an electric efficiency of ORC even in areas with less sunshine, in this case Denmark. turbine to produce electricity, but the flexibility of the system also allows production of lower temperatures for district heating purposes. The solar heating system can thus alternate between providing heat and power or deliver heat exclusively. To maximize yield of energy, the waste heat is utilized and sent to the district heating circuit whereas electrical power is generated at peak price periods. In Figure 7, it can be seen that the CSP field is delivering hot thermal oil to both the ORC unit and the oil-to-water heat exchanger which delivers the heat to the district heating network to the city of Brønderslev. The CSP Figure 4: Image of the concentrated solar power plant in Brønderslev, Denmark solar field has a thermal peak effect of 16.6 MWth and is expected to deliver approximately 16,000 MWh of heat in an average weather year. Apart from the solar field, there are two biomass boilers each of a maximum capacity of 10 MWth Figure 7: Flow chart of the energy distribution at the hybrid plant of Brønderslev running with wood chips as fuel. 424 Andreas Zourellis et al. / Energy Procedia 149 (2018) 420–426 6 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 5

Both the CSP field and the biomass boilers are working in conjunction to supply with sufficient heat the ORC unit, which in full load is supposed to deliver 4MWe. The dissipated heat from the ORC condenser is used to provide additional heat to the district heating network. Therefore, one might notice that the hybrid system is designed in a sustainable and efficient way, avoiding to unnecessarily waste heat to the ambient. The biomass boiler house embeds a 2 MWth heat pump as well, to make use of waste heat from the biomass chimney and supply the district heating as supplementary source. In order to guarantee that the total energy demand is covered at any time, a CHP gas engine is placed as final backup The achievement of the world’s first CSP system combined with a biomass-ORC plant is supported by the Danish Government’s Energy Technology Development and Demonstration Programme (EUDP).

3. Monitoring and validating performance during the first solar season

As aforementioned, the peak performance of the plant is set to reach 16.6 MWth and the annual yield is expected to be 16,000 MWh of thermal energy. Since the CSP-plant went into operation in the end of 2016, it has been meeting the expected operational goals. Figure 5: Daily production data from each season of 2017 In figure 8, the CSP performance in different seasons is illustrated. It is interesting to see that the time moves from Summer to Autumn, Spring and Winter the thermal power output curve shifts down. This is happening due to the lower solar altitude from month to month. As an example Figure 8 shows the expected thermal output for a day in January, April, July and October, based on an average weather year issued by the Danish Meteorological Institute [4]. Usually, when a PTC field tracking axis is not declining from the North-South axis then the profile of the thermal Figure 9: Incidence angle effect on thermal power output curve [2] output curve has two symmetrical peaks (i.e. one in the morning and one in the afternoon). In the present case it should also be mentioned that the thermal peak in the morning hours is always higher than the one in the afternoon. This is Figure 9 shows the effect of turning the tracking axis from exactly North South direction. The daily profile is explained from the tilted tracking axis in Brønderslev which deviates 29o from the North-South. Therefore, the optical then changed and may be adapted to the highest electricity price that at present often is in the mornings at around 8- losses are lower before solar noon, because of the lower incidence angle. The incidence angle is the angle in which 10 [3]. the solar beams hit the surface of the reflecting mirrors in relation to the normal incidence. The lower the incidence angle is, the lower the optical losses are and thus the higher the thermal output is. The incidence angle of a day in May The solar plant performance was monitored and cross checked during its first summer period from May 2017 to can be seen in Figure 9. September 2017. Figure 10 illustrates the modeled versus the measured performance in kWh of heat produced per day and as it can be clearly seen the two series of data come in very good agreement when they get the same daily beam radiation as input.

Figure 8: Seasonal variation on CSP thermal power output curve

Figure 10: Validation of measured vs. computed performance for summer 2017, Perers et.al [3] 6 AndreasAndreas Zourellis Zourellis / Energy et al. Procedia/ Energy Procedia00 (2018 )149 000 (2018)–000 420–426 425 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 5

3. Monitoring and validating performance during the first solar season

Figure 8: Seasonal variation on CSP thermal power output curve

Figure 10: Validation of measured vs. computed performance for summer 2017, Perers et.al [3] 426 Andreas Zourellis et al. / Energy Procedia 149 (2018) 420–426 Andreas Zourellis / Energy Procedia 00 (2018) 000–000 7

The same procedure has been followed and is presented here for a whole day of solar heat production in May. In Figure 11 the measured and calculated thermal performance of the field are presented with a yellow and a black line respectively and it becomes apparent that they are almost identical. All the heat produced by the field at that moment was delivered to the district heating network. The monitored forward water temperature to the district heating grid was also in very good agreement with the calculated one and averaging at around 80oC. With blue and red, the measured and calculated outlet temperature of the thermal oil is shown to be peaking at around 180oC. At that moment the ORC unit was still under construction and there was not need to operate at a higher temperature than that.

DH Power

Oil Outlet Temperature

DH water Outlet Temperature

Figure 11: Measured and calculated performance of solar field [3].

Acknowledgements

The first author really appreciates the assistance from the Technical University of Denmark and especially Senior researcher Bengt Perers whose effort and continuous technical support was essential. Special thanks are expressed to Simon Furbo, Zhiyong Tian Alejandro de la Vega Fernandez for contributing in the performance analysis.

References

[1] B. Perers, S. Furbo and D. Janne , “Thermal performance of concentrating tracking solar collectors,” Technical Univeristy of Denmark (DTU) Civil Engineering Report R-292 (UK) Department of Civil Engineering, Denmark, 2013. [2] Fernandez A. Analyses of Brønderslev solar energy plant by use of TRNSYS. DTU master thesis; 2017. [3] B.Perers, S. Furbo, Z. Tian, J.H. Rothmann, J. Juul, T. Neergaard, P.V. Jensen, J.R. Jensen, P.A. Sørensen, N. From, “Performance of the 27000 m2 parabolic trough collector field, combined with Biomass ORC Cogeneration of Electricity, Brønderslev Denmark”, Solar District Heating Conference 2018, Graz, Austria, 2018 [4] Danmarks Meteorologiske Institut, www.dmi.dk