A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The... more A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The main system components are a parabolic tube collector and a steam accumulator, which provides heat for industrial processes. The use of exergy analysis leads to the identification of potentials for performance improvements. The rate of exergy destruction is calculated over a daily operation cycle, showing that the largest exergy destruction takes place at collector level. The effect of varying the volumetric flow rate per unit collector surface area is also discussed.This paper is an updated version of a paper published in the ECOS'08 proceedings.
In this paper, a study of increasing a photovoltaic (PV) module efficiency via natural/forced coo... more In this paper, a study of increasing a photovoltaic (PV) module efficiency via natural/forced cooling of the PV cell is presented. The PV module is cooled by the air flowing in a duct placed under a back surface of the PV panel. The cooling air is moved either by fan or naturally by the temperature difference generated from the heat transfer with a panel. The system could be applied on the roof of industrial facilities, with electrical and thermal energy needs. The presented 1-D model examines an already published thermal and electrical PV/T approach supplemented with a radiative heat transfer in the panel duct. In addition, an effect of the roughness of the panel back surface is also added to the model. The model coded in an Engineering Equation Software (EES) is capable of evaluating the PV module efficiency and other thermal parameters as the outlet air temperature and back surface temperature. As a result, the performance of the system in a typical winter and summer day is discu...
Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to ... more Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to prepare it for further transport by pipelines it has to be reduced again to a gaseous state, normally by heating it with sea water. A similar technology is envisaged for long-distance transport of Hydrogen as an energy carrier. The scope of this article is the thermodynamic investigation of two power plants for peak load energy production. These two power plants use as fuel the fluids obtained by the re-gasification of the cryogenic fluids. The first proposal is a Hydrogen-fired steam power plant, while the second considers the use of LNG in an oxy-combustion arrangement with subsequent CO2 separation, which is obtained by a three-stage intercooled compression train. The power cycle performance was verified in both cases by exergy analysis. Since the size of these power plants is relatively small (10 MWe), they can be easily built inside the area of LNG gasifiers, or inside the area of t...
ABSTRACT Geothermal power plants are widely used in the Larderello region, Tuscany, due to its fa... more ABSTRACT Geothermal power plants are widely used in the Larderello region, Tuscany, due to its favourable geological characteristics. The geothermal fluid available at Larderello contains about 95% of steam at relatively high temperature (200°C), and about 5% of non-condensable gases, mainly carbon dioxide. Due to its thermodynamic properties, the geothermal fluid is currently used in a Dry Steam power plant, where it is directly expanded in turbine. In this paper, some modifications to the structure of the plant are proposed and the plant is modelled using the software EES®. In the model, the geo-fluid flow is ideally separated in two flows, respectively water vapour flow and carbon dioxide flow, treating separately the expansion and the compression processes. Energy and exergy analysis are performed, and the results show a good agreement with the results presented in the literature, where the geo-fluid is modelled as a single flow. Since the water flow rate for the condensing process is significant, the possibility of recovering work through a Heller system is considered. The results show that 85% of the power required for the pumping of the condensing water can be provided by this Heller system.
... Abstract: A micro combined heat and power (CHP) plant operating through an Organic Rankine Cy... more ... Abstract: A micro combined heat and power (CHP) plant operating through an Organic Rankine Cycle (ORC) using renewable energy is analyzed. The reference system is designed to produce 50 kWe. ... Page 2. 166 - 2 2. CHP ORC power plant description ...
The guiding idea behind oxy-fuel combustion power cycles is guaranteeing a high level of performa... more The guiding idea behind oxy-fuel combustion power cycles is guaranteeing a high level of performance as can be obtained by today's advanced power plants, together with CO2 separation in conditions ready for transport and final disposal. In order to achieve all these ...
ABSTRACT Offshore applications allow to exploit different renewable energy sources (wave, wind, s... more ABSTRACT Offshore applications allow to exploit different renewable energy sources (wave, wind, solar) that are complementary each other, due to their statistical yearly distributions.In this paper, we discuss an offshore platform for energy production from renewable energy sources coupled with three energy storage systems. The proposed offshore platforms uses a Compressed Air Energy Storage (CAES) to timely shift the electricity production from the demand.The performance of the system related to a north Tyrrhenian Sea location was evaluated by a simulation model developed integrating three different software packages (Matlab, EES, TRNSYS).The system was designed to produce 564 kWh on the 2 h a day where peak electricity demand takes place. The results showed that the system is able to produce 177,000 kWh per year.This offshore power plant is conceived for local users (tourist resorts, villages), especially if placed in small or medium islands, wishing to qualify for extensive use of renewable energy.
Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to ... more Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to prepare it for further transport by pipelines it has to be reduced again to a gaseous state, normally by heating it with sea water. A similar technology is envisaged for long-distance transport of ...
A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The... more A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The main system components are a parabolic tube collector and a steam accumulator, which provides heat for industrial processes. The use of exergy analysis ...
... 3. Power plant layout – single-pressure, dual circuit. Fig. ... View thumbnail images. 4. Pow... more ... 3. Power plant layout – single-pressure, dual circuit. Fig. ... View thumbnail images. 4. Power plant layout – dual pressure, single circuit. The second configuration of the power plant is built around a dual-pressure system, using two different solar collectors (Fig. 4). ...
A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The... more A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The main system components are a parabolic tube collector and a steam accumulator, which provides heat for industrial processes. The use of exergy analysis leads to the identification of potentials for performance improvements. The rate of exergy destruction is calculated over a daily operation cycle, showing that the largest exergy destruction takes place at collector level. The effect of varying the volumetric flow rate per unit collector surface area is also discussed.This paper is an updated version of a paper published in the ECOS'08 proceedings.
In this paper, a study of increasing a photovoltaic (PV) module efficiency via natural/forced coo... more In this paper, a study of increasing a photovoltaic (PV) module efficiency via natural/forced cooling of the PV cell is presented. The PV module is cooled by the air flowing in a duct placed under a back surface of the PV panel. The cooling air is moved either by fan or naturally by the temperature difference generated from the heat transfer with a panel. The system could be applied on the roof of industrial facilities, with electrical and thermal energy needs. The presented 1-D model examines an already published thermal and electrical PV/T approach supplemented with a radiative heat transfer in the panel duct. In addition, an effect of the roughness of the panel back surface is also added to the model. The model coded in an Engineering Equation Software (EES) is capable of evaluating the PV module efficiency and other thermal parameters as the outlet air temperature and back surface temperature. As a result, the performance of the system in a typical winter and summer day is discu...
Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to ... more Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to prepare it for further transport by pipelines it has to be reduced again to a gaseous state, normally by heating it with sea water. A similar technology is envisaged for long-distance transport of Hydrogen as an energy carrier. The scope of this article is the thermodynamic investigation of two power plants for peak load energy production. These two power plants use as fuel the fluids obtained by the re-gasification of the cryogenic fluids. The first proposal is a Hydrogen-fired steam power plant, while the second considers the use of LNG in an oxy-combustion arrangement with subsequent CO2 separation, which is obtained by a three-stage intercooled compression train. The power cycle performance was verified in both cases by exergy analysis. Since the size of these power plants is relatively small (10 MWe), they can be easily built inside the area of LNG gasifiers, or inside the area of t...
ABSTRACT Geothermal power plants are widely used in the Larderello region, Tuscany, due to its fa... more ABSTRACT Geothermal power plants are widely used in the Larderello region, Tuscany, due to its favourable geological characteristics. The geothermal fluid available at Larderello contains about 95% of steam at relatively high temperature (200°C), and about 5% of non-condensable gases, mainly carbon dioxide. Due to its thermodynamic properties, the geothermal fluid is currently used in a Dry Steam power plant, where it is directly expanded in turbine. In this paper, some modifications to the structure of the plant are proposed and the plant is modelled using the software EES®. In the model, the geo-fluid flow is ideally separated in two flows, respectively water vapour flow and carbon dioxide flow, treating separately the expansion and the compression processes. Energy and exergy analysis are performed, and the results show a good agreement with the results presented in the literature, where the geo-fluid is modelled as a single flow. Since the water flow rate for the condensing process is significant, the possibility of recovering work through a Heller system is considered. The results show that 85% of the power required for the pumping of the condensing water can be provided by this Heller system.
... Abstract: A micro combined heat and power (CHP) plant operating through an Organic Rankine Cy... more ... Abstract: A micro combined heat and power (CHP) plant operating through an Organic Rankine Cycle (ORC) using renewable energy is analyzed. The reference system is designed to produce 50 kWe. ... Page 2. 166 - 2 2. CHP ORC power plant description ...
The guiding idea behind oxy-fuel combustion power cycles is guaranteeing a high level of performa... more The guiding idea behind oxy-fuel combustion power cycles is guaranteeing a high level of performance as can be obtained by today's advanced power plants, together with CO2 separation in conditions ready for transport and final disposal. In order to achieve all these ...
ABSTRACT Offshore applications allow to exploit different renewable energy sources (wave, wind, s... more ABSTRACT Offshore applications allow to exploit different renewable energy sources (wave, wind, solar) that are complementary each other, due to their statistical yearly distributions.In this paper, we discuss an offshore platform for energy production from renewable energy sources coupled with three energy storage systems. The proposed offshore platforms uses a Compressed Air Energy Storage (CAES) to timely shift the electricity production from the demand.The performance of the system related to a north Tyrrhenian Sea location was evaluated by a simulation model developed integrating three different software packages (Matlab, EES, TRNSYS).The system was designed to produce 564 kWh on the 2 h a day where peak electricity demand takes place. The results showed that the system is able to produce 177,000 kWh per year.This offshore power plant is conceived for local users (tourist resorts, villages), especially if placed in small or medium islands, wishing to qualify for extensive use of renewable energy.
Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to ... more Natural Gas is often liquefied (LNG) for its transport by ships over long distances. In order to prepare it for further transport by pipelines it has to be reduced again to a gaseous state, normally by heating it with sea water. A similar technology is envisaged for long-distance transport of ...
A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The... more A model for the thermodynamic analysis of a non-stationary solar thermal system is described. The main system components are a parabolic tube collector and a steam accumulator, which provides heat for industrial processes. The use of exergy analysis ...
... 3. Power plant layout – single-pressure, dual circuit. Fig. ... View thumbnail images. 4. Pow... more ... 3. Power plant layout – single-pressure, dual circuit. Fig. ... View thumbnail images. 4. Power plant layout – dual pressure, single circuit. The second configuration of the power plant is built around a dual-pressure system, using two different solar collectors (Fig. 4). ...
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Papers by Duccio Tempesti