Optimization of trigeneration systems by Mathematical Programming: Influence of plant scheme and boundary conditions

2015

Abstract The large potential for energy saving by cogeneration and trigeneration in the building sector is scarcely exploited due to a number of obstacles in making the investments attractive. The analyst often encounters difficulties in identifying optimal design and operation strategies, since a number of factors, either endogenous (i.e. related with the energy load profiles) and exogenous (i.e. related with external conditions like energy prices and support mechanisms), influence the economic viability. In this paper a decision tool is adopted, which represents an upgrade of a software analyzed in previous papers; the tool simultaneously optimizes the plant lay-out, the sizes of the main…

Performance maps for an air-cooled air conditioning system as a preliminary instrument for the diagnosis of evaporator fouling

2019

Abstract During the past few decades, there has been increased interest in the development of automated approaches for detecting and diagnosing faults in air conditioning systems. Among them, thermoeconomic diagnosis is a technique which involves the use of exergy analysis. As a first step towards improving its performance, this work is focused on the thermodynamic and exergy analysis of a direct expansion air conditioning system used in small commercial building applications. The analysis was carried out by means of experimental activities on a 17.5 kW rooftop unit installed at the Herrick Laboratories, Purdue University, Indiana (USA). The system under investigation was equipped with a va…

Getting insights into the behavior of variable speed direct expansion air conditioning systems under faulty operating conditions

2019

Direct expansion air conditioning systems, such as rooftop units, are widely adopted in small and medium scale commercial buildings. In order to increase the energy performance of these systems during part-load operation, variable-speed compressors and fans have been adopted in the last two decades. However, profitable energy saving could be achieved not only by optimizing the design and the control of these systems, but also by scheduling a proper maintenance strategy. In fact, if not properly maintained, no benefits would be achieved even when more sophisticated systems are adopted. In order to support plant owners in scheduling cost-effective maintenance program, Fault Detection and Diag…

Assessing the Robustness of Thermoeconomic Diagnosis of Fouled Evaporators: Sensitivity Analysis of the Exergetic Performance of Direct Expansion Coi…

2016

Thermoeconomic diagnosis of refrigeration systems is a pioneering approach to the diagnosis of malfunctions, which has been recently proven to achieve good performances for the detection of specific faults. Being an exergy-based diagnostic technique, its performance is influenced by the trends of exergy functions in the “design” and “abnormal” conditions. In this paper the sensitivity of performance of thermoeconomic diagnosis in detecting a fouled direct expansion coil and quantifying the additional consumption it induces is investigated; this fault is critical due to the simultaneous air cooling and dehumidification occurring in the coil, that induce variations in both the chemical and th…

Exergy analysis of reverse electrodialysis

2018

Abstract Reverse electrodialysis in closed loop configurations is a promising membrane technology in the energy conversion and storage fields. One of the main advantages of closed-loop reverse electrodialysis is the possibility of using a wide range of operating concentrations, flow rates and different salts for generating the salinity gradient. In this work, an original exergy analysis of the reverse electrodialysis process was carried out in order to investigate reverse electrodialysis performance in terms of energetic and exergetic efficiency parameters in a wide range of operating conditions. A mono-dimensional model of the reverse electrodialysis process was developed, in which all sou…

Exergy analysis and thermoeconomic cost accounting of a Combined Heat and Power steam cycle integrated with a Multi Effect Distillation-Thermal Vapou…

2017

Abstract In this paper an exergy analysis and thermoeconomic cost accounting of a Combined Heat and Power steam cycle integrated with Multi Effect Distillation-Thermal Vapour Compression plant is performed; the goal of the study is to show how these methodologies provide a rational criterion to allocate production costs on electricity and freshwater in such a dual purpose system. After a brief overview on the methodology and a description of reference plant, exergy analysis is carried out to calculate exergy flows and exergy efficiencies at component level. A detailed description of the adopted thermoeconomic model is given. In a first scenario, cost accounting is performed assuming that th…

A novel thermoeconomic analysis under dynamic operating conditions for space heating and cooling systems

2019

Abstract Thermoeconomic analysis allows for a deep understanding of the cost formation process within an energy system, providing insights into the possible routes for improvement. Several thermoeconomic approaches are well-established for application in systems with steady operating conditions, such as power plants, while a limited number of applications to air-conditioning systems in buildings have been proposed, due to the difficulties in dealing with very irregular load profiles and unsteady plant operating conditions. This study investigates the potential of Thermoeconomics as a support for decision making in building energy systems, proving its capability to identify trade-offs betwee…

Characterization of cooling loads in the wine industry and novel seasonal indicator for reliable assessment of energy saving through retrofit of chil…

2020

Abstract The food sector is a major consumer of energy and growing efforts are being made in the search for solutions that will guarantee the efficient and sustainable use of energy resources. Among the different sectors, wineries are attracting particular interest due to the continuous growth of the global market and production. Surveys conducted in the winemaking sector have highlighted the importance of performing accurate energy audits and have identified the installation of efficient refrigeration systems as a promising solution in a variety of cases. Unfortunately, the savings achievable by efficient cooling technologies are often estimated using simplified approaches which do not tak…

Assessing the Energy-Saving Potential of a Dish-Stirling Concentrator Integrated into Energy Plants in the Tertiary Sector

2021

Energy consumed for air conditioning in residential and tertiary sectors accounts for a large share of global use. To reduce the environmental impacts burdening the covering of such demands, the adoption of renewable energy technologies is increasing. In this regard, this paper evaluates the energy and environmental benefits achievable by integrating a dish-Stirling concentrator into energy systems used for meeting the air conditioning demand of an office building. Two typical reference energy plants are assumed: (i) a natural gas boiler for heating purposes and air-cooled chillers for the cooling periods, and (ii) a reversible heat pump for both heating and cooling. For both systems, a dis…

Development of “Design of Experiments” for modelling direct expansion air-conditioning systems under variable cooling loads and faulty operating cond…

2019

Air conditioning systems are widely adopted in the building sector and are generally responsible for high energy consumption. Part of this consumption is related to the poor maintenance adopted by plant owner over time, which causes energy performance degradation. Typical faults, such as fouling or improper refrigerant charge have been shown to heavily impact on energy consumption of these systems. In order to support cost-effective maintenance schedule, Fault Detection and Diagnosis Technique are under investigation in the world. However, in order to devise a diagnostic method a preliminary modelling of air conditioning system is due. To this aim, a test procedure which requires the least …

Wave Energy Assessment along Sicilian Coastline, Based on DEIM Point Absorber

2017

The use of renewable energy sources is one of the most relevant goals to be achieved in order to match the climate protection targets. As a case study, the paper shows the current electrical energy production by sources in the Sicilian context. Among the renewable energy sources, the paper investigates the wave energy potential along the Sicilian coasts, because of the favorable climate around the island. A point absorber is present in order to exploit this source. Two scenarios are presented, with two different levels of energy production.

Editorial: Sustainable development of energy, Water and Environment Systems

2020

In 2018 the Conference on Sustainable Development of Energy, Water and Environment Systems (SDEWES) was held in three different locations and periods, so as to offer to the scientific community working in the field several opportunities to share and discuss new ideas and disseminate results of research activities. The 1st Latin American SDEWES Conference was held in Rio de Janeiro (Brasil) in January 28–31 and attracted 180 scientists from 35 countries, with a high number of contributions mainly from Southern American and European academics and professionals, who reciprocally enriched about emerging issues in the field of sustainable development in these continents. Also, the participants a…

Reverse electrodialysis heat engine with multi-effect distillation: Exergy analysis and perspectives

2019

Abstract The increasing worldwide energy demand is rising the interest on alternative power production technologies based on renewable and emission-free energy sources. In this regard, the closed-loop reverse electrodialysis heat engine is a promising technology with the potential to convert low-grade heat into electric power. The reverse electrodialysis technology has been under investigation in the last years to explore the real potentials for energy generation from natural and artificial solutions, and recent works have been addressing also the potential of its coupling with regeneration strategies, looking at medium and large energy supply purposes. In this work, for the first time, a c…

Dynamic simulation of a 4th Generation District Heating network with the presence of prosumers

2022

District Heating Network is identified as a promising technology for the decarbonization of urban areas. Thanks to the surplus of heat available from distributed renewable energy plants, a typical heat consumer of the network could become an energy producer during the day (typically referred to as “prosumer”). Models for thermal grids developed during the years usually assumed a centralized heat production. The increasing presence of prosumers will require accurate dynamic modeling to monitor the changes induced in the thermohydraulic variables of the network. To fill this knowledge gap, this paper aims at developing a model of a thermal grid with prosumers in TRNSYS environment. The model …

On the Reliability of Optimization Results for Trigeneration Systems in Buildings, in the Presence of Price Uncertainties and Erroneous Load Estimati…

2016

Cogeneration and trigeneration plants are widely recognized as promising technologies for increasing energy efficiency in buildings. However, their overall potential is scarcely exploited, due to the difficulties in achieving economic viability and the risk of investment related to uncertainties in future energy loads and prices. Several stochastic optimization models have been proposed in the literature to account for uncertainties, but these instruments share in a common reliance on user-defined probability functions for each stochastic parameter. Being such functions hard to predict, in this paper an analysis of the influence of erroneous estimation of the uncertain energy loads and pric…

Coupling salinity gradient heat engines with power generation systems and industrial processes

2022

Abstract This chapter presents some potential applications of salinity gradient power-heat engines (SGP-HEs) in power generation systems and industrial processes, where low-temperature waste heat flows could be available. In order to show this concept, five case studies are proposed. In the first case study, a thermoelectric power plant is considered. The analysis evaluates the possibility to convert the low-grade heat content of flue gases into additional electricity via SGP-HEs. In the second case study, an SGP-HE is coupled with an organic Rankine cycle (ORC) plant to enhance the amount of electricity produced from a medium-temperature waste heat flow released by an industrial process. I…

On Thermoeconomic Diagnosis of a Fouled Direct Expansion Coil: Effects of Induced Malfunctions on Quantitative Performance of the Diagnostic Technique

2017

Thermoeconomic diagnosis represents a promising technique for the detection of common faults in refrigeration systems, which are responsible of degradation in their energetic performance. Recently, the authors have carried out a sensitivity analysis of the performance of this method to the thermodynamic conditions of inlet air and to the geometry of the direct expansion coil, in case of degradation induced by evaporator fouling. The analysis showed that the method is able to detect this fault, but sometimes its quantitative assessments are not satisfactory. In order to understand more in-depth the origin of such results and identify margins for refinement of the technique, this paper is aim…

Thermodynamic-based cost allocation in low-temperature thermal grids in presence of distributed energy producers

2022

Thermal grids are well-established technologies that can cover the thermal demands of buildings in a more sustainable way. The lower operating temperature will allow not only for the integration of heat produced by thermal renewable energy sources but also for the storage of surplus electricity from the grid using power to heat technologies. To ensure a wider diffusion of this technology, it is important to propose a method for the cost allocation among producers connected to the grid. In this regard, this paper proposes Exergoeconomics as a possible solution. To show the capabilities of the method, some operating scenarios are compared for a cluster of five buildings in the tertiary sector…

Potential applications of Salinity Gradient Power-Heat Engines for recovering low-temperature waste heat in cogeneration plants

2021

Abstract Salinity Gradient Power-Heat Engine is an innovative technology able to convert very low-temperature heat into electricity. Energy and economic benefits could be achieved by integrating this technology into cogeneration plants, where the exploitation of waste heat available during the operation could increase the revenues arising from “High-Efficiency” labels. For the first time, this paper proposes two potential applications in this field, and three illustrative case studies are purposely investigated. In the first case study, a salinity gradient-heat engine converts the waste heat available from a cogeneration plant serving an industrial process. In the second case study, a salin…

An integrated approach based on Life Cycle Assessment and Thermoeconomics: Application to a water-cooled chiller for an air conditioning plant

2018

Abstract A large number of methods for energy systems analysis were developed in the last decades, aimed at acquiring an in-depth understanding of plant performances and enabling analysts to identify optimal design and operating conditions. In this work an integrated approach based on Life Cycle Assessment and Thermoeconomics is proposed as a method for assessing the exergo-environmental profile of energy systems. The procedure combines the capabilities of these two techniques, to account simultaneously for aspects related to thermodynamics of energy conversion processes and to the overall impacts along the plant life cycle related to other phases, i.e. from raw material extraction to the d…

Exergoeconomic analysis as a tool for supporting the design and operation of multiple chiller systems in air conditioning applications.

2019

Multiple-Chillers systems represent viable solutions for medium/large-scale air conditioning applications. In these systems, however, design and energy savings are highly affected by the configuration and operation strategies adopted. For instance, when considering multiple chillers of same size, “symmetric” or “sequential” load sharing strategies are two viable options. Conversely, when considering chillers of different sizes, a wide combination of chillers cooling capacities may be adopted. It is apparent that an integrated analysis of the design and operation of these systems should be carried out in order to achieve profitable energy saving. With this respect, Exergoeconomics, which res…

Thermodynamic, Exergy, and Thermoeconomic analysis of Multiple Effect Distillation Processes

2018

Abstract Multiple effect distillation (MED) is nowadays the preferred technology for the construction of new plants based on thermal processes in the growing desalination market. MED technology, in fact, presents a number of advantages with respect to the more traditional multistage flash technology, among all the lower energy consumption achievable in MED plants. However, a large potential for improvement in terms of lowering production costs still exists, which stimulates further efforts on process optimization from companies and researchers involved in the field. Thermodynamic and exergy analysis provides useful insights regarding the identification of main inefficiencies and the margins…

Exergoeconomics as a Cost-Accounting Method in Thermal Grids with the Presence of Renewable Energy Producers

2022

Thermal grids are efficient, reliable, and sustainable technologies for satisfying the thermal demands of buildings. The capability to operate at a low temperature allows not only for the integration of heat produced by renewable energy sources but also for the storage of surplus electricity from the grid via “power to heat” technologies. Besides, in the future, heat consumers are expected to behave increasingly as “prosumers”, supplying in some periods heat produced by renewable energy plants on site. In this scenario, it is important to propose a method for the cost allocation among producers connected to the grid. In this regard, this paper proposes Exergoeconomic…

Promoting the Flexibility of Thermal Prosumers Equipped with Heat Pumps to Support Power Grid Management

2023

The increasing share of renewable energy sources in energy systems will lead to unpredictable moments of surplus/deficit in energy production. To address this issue, users with heat pumps can provide support to power grid operators through flexible unit operation achieved via Demand Response programs. For buildings connected to low-temperature heating networks with ensured third-party access, further room for flexibility can be explored by investigating the production of surplus heat that can be sold to the network. A key aspect lies in the identification of the energy pricing options that could encourage such flexible operation of a heat pump by “thermal prosumers”. To this aim…

Integrated thermodynamic and electrical modelling of a variable-speed reversible heat pump: analysis of the cooling mode operation

2022

Variable-speed reversible heat pumps are increasingly adopted for space heating and cooling in residential and tertiary sectors. It is recognized that these systems will play a key role in medium- and small-scale 4th generation district heating and cooling networks. Indeed, with the high penetration of intermittent renewable energy sources, such technology could help reduce issues related to the surplus of electricity from renewable energy sources by converting it into heat or cold. To reliably assess the benefits achievable in these emerging applications, it is necessary to develop models which can simulate not only the steady-state operation but also the dynamic response of the system wit…

Exergoeconomic analysis as support in decision-making for the design and operation of multiple chiller systems in air conditioning applications

2020

Abstract Multiple-chillers systems represent viable solutions for medium/large-scale air conditioning applications characterized by variable cooling demand. The energy efficiency of such systems is influenced by the number of chillers, the combination of cooling capacities, and the load-sharing among the units. Large efforts have been devoted to developing efficient operation strategies for these systems, but rules of thumb are usually adopted for selecting cooling capacities thus leaving room for energy and economic savings. In this paper, exergoeconomic analysis is proposed as a promising method to identify near-optimal design and operation strategies, due to the capability of exergoecono…

Modelling of a prosumer’s substation in a district heating network: validation and dynamic analysis

Thermal grids will play a key role in the development of local energy communities and the achievement of 100% renewable societies. However, challenges are related to the capability of dealing with the increasing number of producers which could supply heat to thermal grids. Indeed, as in the case of the electricity grid, heat could be available for some hours in a day from RES plants installed at user level and distributed in the network (also referred to as “prosumers”). To achieve more reliable results when performing energy analyses of these innovative applications, there is a need to rely on accurate models of each component. For instance, substations are of paramount importance in the i…

Improving energy efficiency of commercial buildings by Combined Heat Cooling and Power plants

2020

Abstract Commercial buildings play a key-role in the energy consumption of the building sectors. Recent statistics have shown that as the number of commercial buildings is continuously increasing, their effects on energy consumption are expected to grow. These buildings are characterized by high energy demand mainly due to lighting and HVAC requirements. Rooms of energy saving exist by considering that: (i) electricity demands and HVAC requirements occur simultaneously during the day and (ii) both demands are currently satisfied by using separate energy systems. It is apparent that the adoption of polygeneration systems could represent a valid solution to achieve energy savings. To this aim…

INNOVATIVE APPLICATIONS OF EXERGY ANALYSIS AND THERMOECONOMICS IN CHEMICAL, THERMAL AND COOLING ENERGY CONVERSION SYSTEMS

Since 70s, the world has been becoming more and more concerned about energy and environmental issues. The need of meeting the current energy demand by guaranteeing the ability of future generation to satisfy theirs have been pushing research not only to exploit alternative energy sources such as renewable energies, but also to improve the efficiency of energy conversion systems. To this regard, developing systems that use efficiently energy is of paramount importance especially in those countries which rely on non-renewable energy sources such as oil, natural gas, and coal. In fact, the reduction of energy consumption will lead not only to the saving of unrestorable and limited energy resou…

Exergy analysis and thermoeconomic cost accounting of a CHP steam cycle integrated with MED-TVC desalination

2016

In this paper exergy analysis and thermoeconomic cost accounting of a CHP steam cycle integrated with MED-TVC plant is performed; the purpose is to show how this methodology provides a rational criterion to allocate production costs on electricity and freshwater. After a brief overview on methodology and a description of reference plant, exergy analysis is carried out in order to calculate exergy flows and plant exergetic performance. A detailed description of the adopted thermoeconomic model is given. Cost accounting is performed considering two scenarios: in the first, the concentrated brine is disposed back to sea, thus being its exergy content definitively wasted; in the second, convers…