I obtained the Laurea degree in physics (cum laude) at the University of Rome "La Sapienza" in 1991, and the Ph.D. at the University of Rome Tor Vergata in 1996. In 2001 I became research assistant at the now Department of Enterprise Engineering of the University of Rome "Tor Vergata". Since 2007 I manage the ESTER facility which consists of a solar and weather unit and of a PV modules monitoring unit. Recently my interests are focused on weather and solar radiation measurements at ground for performance evaluation of photovoltaic systems and monitoring and test of solar conversion devices of various technologies. Since 2012 I am working on developing data driven algorithms for PV power forecast for smart grid management. I am also interested in energy efficiency in buildings and innovative materials for building construction. I use dynamic simulation and microclimatic monitoring for retrofit and control of building to achieve energy efficiency. I apply the same tools also for the conservation of cultural heritage. I hold the chair of Environmental Applied Physics at the Engineering Faculty of the University of Rome Tor Vergata.
This paper presents results from a high speed photovoltaic sweeper system measuring the IVcharact... more This paper presents results from a high speed photovoltaic sweeper system measuring the IVcharacteristics once per second of a solar panel under test at the ESTER PV test laboratory at the Tor Vergata University in Rome and in Denmark. The high temporal resolution of the scans shows the detailed temperature characteristics of the primary panel parameters compared to the reference irradiation/spectral data obtained via the ESTER instrumentation. An analysis of the irradiance levels shows that the STC and NOCT conditions in real life are extremely rare events. Analysis show that the temperature coefficient is depending on the irradiance level.
The growing photovoltaic generation results in a stochastic variability of the electric demand th... more The growing photovoltaic generation results in a stochastic variability of the electric demand that could compromise the stability of the grid and increase the amount of energy reserve and the energy imbalance cost. On regional scale, solar power estimation and forecast is becoming essential for Distribution System Operators, Transmission System Operator, energy traders, and aggregators of generation. Indeed the estimation of regional PV power can be used for PV power supervision and real time control of residual load. Mid-term PV power forecast can be employed for transmission scheduling to reduce energy imbalance and related cost of penalties, residual load tracking, trading optimization, secondary energy reserve assessment.
The aim of this work is to improve knowledge about the observed seasonal behavior of CdTe modules... more The aim of this work is to improve knowledge about the observed seasonal behavior of CdTe modules under real operating conditions. The study consists of a characterization of the CdTe photovoltaic (PV) technology based on the application of the Sandia Array Performance Model (SAPM) to two PV fields in Italy (Viterbo and Bolzano) and two PV test modules in Spain (Madrid and Jaén). SAPM is a semi-empirical power estimation model that takes into account the four main phenomena that affect the Performance Ratio (PR) of PV plants or modules: temperature, angle of incidence, irradiance and spectral effects. New outdoor experimental procedures were set up at the ESTER station of University of Rome Tor Vergata to validate the temperature coefficients, the angle of incidence coefficients and the spectral mismatch coefficients of CdTe modules to be used in the SAPM model implementation. A detailed analysis of the deviation between the experimental PR data and the modeled PR estimated by SAPM reveals that it is possible to characterize the residuals and attribute them to phenomena not considered by the model.
The paper presents the most interesting results recently obtained at FTA Laboratories of the Univ... more The paper presents the most interesting results recently obtained at FTA Laboratories of the University of Tor Vergata in the field of solar energy applications, in the framework of an integrated approach using both simulation, experimental and theoretical tools. The paper aims to stress the relevance of a system approach as a methodology. Figure 1. The ESTeR Stand for the Outdoor Testing of Solar PV Panels. Figure 2. View of the reference PV panel used for experimental validation of the simulation model. Our second item of interest is to forecast the potential for PV by side of materials of the ultimate generation, namely the third, especially the organic ones. To do this, a wide cooperation with the CHOSE (Center for Hybrid and Organic Solar Energy) center of the University of Tor Vergata has been established since year 2006. As the behaviour of dye solar cells is concerned, typical tracks [6] of an outdoor characterization of cells (Fig.6) built by CHOSE are reported in Figure 7.
IOP Conference Series: Materials Science and Engineering, 2020
Dynamic simulation is increasingly adopted in the preventive conservation of cultural heritage as... more Dynamic simulation is increasingly adopted in the preventive conservation of cultural heritage as an advanced method to investigate strategies for mitigating the climate-induced degradation. The conservation of paper collections is strongly interrelated with the relative humidity of the air, as organic-hygroscopic materials act as buffers on relative humidity fluctuations while being vulnerable to moisture-induced damage. In the dynamic simulation of the microclimate within library and archival storage facilities, it is thus fundamental to include the hygrothermal interaction between the building and its hygroscopic content. The hygroscopic behaviour of paper collections can be modelled by hygrothermal tools such as those of the HAM-family (Heat, Air and Moisture), used to simulate simultaneous heat and mass transfers through porous envelope materials. This research aims at investigating the use of the HMWall model coupled with the software IDA ICE (Indoor Climate and Energy) to sim...
Built heritage energy and environmental improvement is increasingly being recognised as a key dri... more Built heritage energy and environmental improvement is increasingly being recognised as a key driver in the fight against climate change. This effort necessitates a thorough understanding of the building to guide the selection of technologies and design solutions. To have a picture of the buildings’ characteristics and behaviour that is as complete as possible, in situ studies are essential, although the complexities and heterogeneities of historical buildings make these analyses still challenging, especially in professional practice. To address these issues, the paper describes an integrated approach including the field application of Non-Destructive Techniques (namely, Heat Flow Meter measurements, Infrared thermographies and indoor environmental monitoring) within a Heritage Building Information Modelling process. This interdisciplinary/integrated approach fostered the use of each type of analysis’s results to guide the subsequent analyses and incrementally deepen the knowledge o...
Calibration of the existing building simulation model is key to correctly evaluating the energy s... more Calibration of the existing building simulation model is key to correctly evaluating the energy savings that are achievable through retrofit. However, calibration is a non-standard phase where different approaches can possibly lead to different models. In this study, an existing residential building is simulated in parallel by four research groups with different dynamic simulation tools. Manual/automatic methodologies and basic/detailed measurement data sets are used. The calibration is followed by a validation on two evaluation periods. Monitoring data concerning the windows opening by the occupants are used to analyze the calibration outcomes. It is found that for a good calibration of a model of a well-insulated building, the absence of data regarding the users’ behavior is more critical than uncertainty on the envelope properties. The automatic approach is more effective in managing the model complexity and reaching a better performing calibration, as the RMSE relative to indoor...
The high share of PV energy requires greater system flexibility to address the increased demand/s... more The high share of PV energy requires greater system flexibility to address the increased demand/supply imbalance induced by the inherent intermittency and variability of the solar resource. In this work, we have developed a methodology to evaluate the margins for imbalance reduction and flexibility that can be achieved by advanced solar/wind forecasting and by strengthening the national transmission grid connecting the Italian market areas. To this end, for the forecasting of the day-ahead supply that should be provided by dispatchable generators, we developed three advanced load/PV/wind forecasting methodologies based on a chain or on the optimal mix of different forecasting techniques. We showed that, compared to the baseline forecast, there is a large margin for the imbalance/flexibility reduction: 60.3% for the imbalance and 47.5% for the flexibility requirement. In contrast, the TSO forecast leaves only a small margin to reduce the imbalance of the system through more accurate ...
: Information concerning the performance of photovoltaic (PV) plants in a region is of fundamenta... more : Information concerning the performance of photovoltaic (PV) plants in a region is of fundamental importance for many stakeholders of the sector. Nevertheless, often the lack of meteorological measurements – irradiance over all – prevent from correctly assessing the current health status of PV plants, i.e. the presence of ongoing mechanisms that gradually cause a performance degradation higher than expected and warranted. This study presents a methodology to infer probabilistic information on the performance loss rate (PLR) of a PV fleet in a region, when only few characteristics of PV plants (e.g. final yield, location, nominal power) are known. It makes use of satellite-retrieved values of global horizontal and diffuse horizontal irradiance, downloaded freely and only for an optimized number of representative locations. A fleet of 1899 PV plants located in South Tyrol (North-East of Italy) is used as a case study to validate the methodology, and results and possible applications are presented. In general, the presented methodology looks promising in extracting statistical information from a fleet of PV plants distributed in a region, and in inferring the probabilistic performance of future plants installed in the same area. Issues concerning the quality of the input data, related especially to the irradiance and the local skyline, are identified and discussed for a further improvement of the methodology.
The paper reports about a new temperature sensor which is going to be used in the forthcoming spa... more The paper reports about a new temperature sensor which is going to be used in the forthcoming space mission of ESA-NASA, called Cassini-Huygens. A prototype of the sensor has been designed and manufactured in the Heat Transfer Laboratory. Thermal calibration has been performed in the same laboratory while fluid dynamics tests have been carried out in wind tunnels of other laboratories. The flight version of the sensor, to be used in the space mission, has been manufactured by a company specialised in flight measurement sensors. Thermal and fluid dynamics calibrations have been conducted in order to allow accurate temperature measurements and to know the time constant of the sensor. A small time constant is required for the sensor to respond quickly to changes in the atmospheric gas temperature during the descent of the space probe into Titan, the satellite of Saturn. Heat transfer tests have been done in order to correlate the time constant of the sensor to the basic convective heat...
This paper presents results from a high speed photovoltaic sweeper system measuring the IVcharact... more This paper presents results from a high speed photovoltaic sweeper system measuring the IVcharacteristics once per second of a solar panel under test at the ESTER PV test laboratory at the Tor Vergata University in Rome and in Denmark. The high temporal resolution of the scans shows the detailed temperature characteristics of the primary panel parameters compared to the reference irradiation/spectral data obtained via the ESTER instrumentation. An analysis of the irradiance levels shows that the STC and NOCT conditions in real life are extremely rare events. Analysis show that the temperature coefficient is depending on the irradiance level.
The growing photovoltaic generation results in a stochastic variability of the electric demand th... more The growing photovoltaic generation results in a stochastic variability of the electric demand that could compromise the stability of the grid and increase the amount of energy reserve and the energy imbalance cost. On regional scale, solar power estimation and forecast is becoming essential for Distribution System Operators, Transmission System Operator, energy traders, and aggregators of generation. Indeed the estimation of regional PV power can be used for PV power supervision and real time control of residual load. Mid-term PV power forecast can be employed for transmission scheduling to reduce energy imbalance and related cost of penalties, residual load tracking, trading optimization, secondary energy reserve assessment.
The aim of this work is to improve knowledge about the observed seasonal behavior of CdTe modules... more The aim of this work is to improve knowledge about the observed seasonal behavior of CdTe modules under real operating conditions. The study consists of a characterization of the CdTe photovoltaic (PV) technology based on the application of the Sandia Array Performance Model (SAPM) to two PV fields in Italy (Viterbo and Bolzano) and two PV test modules in Spain (Madrid and Jaén). SAPM is a semi-empirical power estimation model that takes into account the four main phenomena that affect the Performance Ratio (PR) of PV plants or modules: temperature, angle of incidence, irradiance and spectral effects. New outdoor experimental procedures were set up at the ESTER station of University of Rome Tor Vergata to validate the temperature coefficients, the angle of incidence coefficients and the spectral mismatch coefficients of CdTe modules to be used in the SAPM model implementation. A detailed analysis of the deviation between the experimental PR data and the modeled PR estimated by SAPM reveals that it is possible to characterize the residuals and attribute them to phenomena not considered by the model.
The paper presents the most interesting results recently obtained at FTA Laboratories of the Univ... more The paper presents the most interesting results recently obtained at FTA Laboratories of the University of Tor Vergata in the field of solar energy applications, in the framework of an integrated approach using both simulation, experimental and theoretical tools. The paper aims to stress the relevance of a system approach as a methodology. Figure 1. The ESTeR Stand for the Outdoor Testing of Solar PV Panels. Figure 2. View of the reference PV panel used for experimental validation of the simulation model. Our second item of interest is to forecast the potential for PV by side of materials of the ultimate generation, namely the third, especially the organic ones. To do this, a wide cooperation with the CHOSE (Center for Hybrid and Organic Solar Energy) center of the University of Tor Vergata has been established since year 2006. As the behaviour of dye solar cells is concerned, typical tracks [6] of an outdoor characterization of cells (Fig.6) built by CHOSE are reported in Figure 7.
IOP Conference Series: Materials Science and Engineering, 2020
Dynamic simulation is increasingly adopted in the preventive conservation of cultural heritage as... more Dynamic simulation is increasingly adopted in the preventive conservation of cultural heritage as an advanced method to investigate strategies for mitigating the climate-induced degradation. The conservation of paper collections is strongly interrelated with the relative humidity of the air, as organic-hygroscopic materials act as buffers on relative humidity fluctuations while being vulnerable to moisture-induced damage. In the dynamic simulation of the microclimate within library and archival storage facilities, it is thus fundamental to include the hygrothermal interaction between the building and its hygroscopic content. The hygroscopic behaviour of paper collections can be modelled by hygrothermal tools such as those of the HAM-family (Heat, Air and Moisture), used to simulate simultaneous heat and mass transfers through porous envelope materials. This research aims at investigating the use of the HMWall model coupled with the software IDA ICE (Indoor Climate and Energy) to sim...
Built heritage energy and environmental improvement is increasingly being recognised as a key dri... more Built heritage energy and environmental improvement is increasingly being recognised as a key driver in the fight against climate change. This effort necessitates a thorough understanding of the building to guide the selection of technologies and design solutions. To have a picture of the buildings’ characteristics and behaviour that is as complete as possible, in situ studies are essential, although the complexities and heterogeneities of historical buildings make these analyses still challenging, especially in professional practice. To address these issues, the paper describes an integrated approach including the field application of Non-Destructive Techniques (namely, Heat Flow Meter measurements, Infrared thermographies and indoor environmental monitoring) within a Heritage Building Information Modelling process. This interdisciplinary/integrated approach fostered the use of each type of analysis’s results to guide the subsequent analyses and incrementally deepen the knowledge o...
Calibration of the existing building simulation model is key to correctly evaluating the energy s... more Calibration of the existing building simulation model is key to correctly evaluating the energy savings that are achievable through retrofit. However, calibration is a non-standard phase where different approaches can possibly lead to different models. In this study, an existing residential building is simulated in parallel by four research groups with different dynamic simulation tools. Manual/automatic methodologies and basic/detailed measurement data sets are used. The calibration is followed by a validation on two evaluation periods. Monitoring data concerning the windows opening by the occupants are used to analyze the calibration outcomes. It is found that for a good calibration of a model of a well-insulated building, the absence of data regarding the users’ behavior is more critical than uncertainty on the envelope properties. The automatic approach is more effective in managing the model complexity and reaching a better performing calibration, as the RMSE relative to indoor...
The high share of PV energy requires greater system flexibility to address the increased demand/s... more The high share of PV energy requires greater system flexibility to address the increased demand/supply imbalance induced by the inherent intermittency and variability of the solar resource. In this work, we have developed a methodology to evaluate the margins for imbalance reduction and flexibility that can be achieved by advanced solar/wind forecasting and by strengthening the national transmission grid connecting the Italian market areas. To this end, for the forecasting of the day-ahead supply that should be provided by dispatchable generators, we developed three advanced load/PV/wind forecasting methodologies based on a chain or on the optimal mix of different forecasting techniques. We showed that, compared to the baseline forecast, there is a large margin for the imbalance/flexibility reduction: 60.3% for the imbalance and 47.5% for the flexibility requirement. In contrast, the TSO forecast leaves only a small margin to reduce the imbalance of the system through more accurate ...
: Information concerning the performance of photovoltaic (PV) plants in a region is of fundamenta... more : Information concerning the performance of photovoltaic (PV) plants in a region is of fundamental importance for many stakeholders of the sector. Nevertheless, often the lack of meteorological measurements – irradiance over all – prevent from correctly assessing the current health status of PV plants, i.e. the presence of ongoing mechanisms that gradually cause a performance degradation higher than expected and warranted. This study presents a methodology to infer probabilistic information on the performance loss rate (PLR) of a PV fleet in a region, when only few characteristics of PV plants (e.g. final yield, location, nominal power) are known. It makes use of satellite-retrieved values of global horizontal and diffuse horizontal irradiance, downloaded freely and only for an optimized number of representative locations. A fleet of 1899 PV plants located in South Tyrol (North-East of Italy) is used as a case study to validate the methodology, and results and possible applications are presented. In general, the presented methodology looks promising in extracting statistical information from a fleet of PV plants distributed in a region, and in inferring the probabilistic performance of future plants installed in the same area. Issues concerning the quality of the input data, related especially to the irradiance and the local skyline, are identified and discussed for a further improvement of the methodology.
The paper reports about a new temperature sensor which is going to be used in the forthcoming spa... more The paper reports about a new temperature sensor which is going to be used in the forthcoming space mission of ESA-NASA, called Cassini-Huygens. A prototype of the sensor has been designed and manufactured in the Heat Transfer Laboratory. Thermal calibration has been performed in the same laboratory while fluid dynamics tests have been carried out in wind tunnels of other laboratories. The flight version of the sensor, to be used in the space mission, has been manufactured by a company specialised in flight measurement sensors. Thermal and fluid dynamics calibrations have been conducted in order to allow accurate temperature measurements and to know the time constant of the sensor. A small time constant is required for the sensor to respond quickly to changes in the atmospheric gas temperature during the descent of the space probe into Titan, the satellite of Saturn. Heat transfer tests have been done in order to correlate the time constant of the sensor to the basic convective heat...
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Papers by Cristina Cornaro