Mathematical modelling of operation modes and performance evaluation of an innovative small-scale concentrated solar organic Rankine cycle plant

In this paper an innovative small-scale concentrated solar 2 kWe organic Rankine cycle plant coupled with a phase change material storage tank equipped with reversible heat pipes is investigated using a simulation analysis. The plant, intended for residential applications, is going to be built and tested under the European funded H2020 Innova MicroSolar project executed by the consortium of several Universities and industrial organizations, led by Northumbria University. The authors of this work used the design of the integrated system, developed by the consortium, to preliminary estimate the overall performance of the system in order to provide useful information for its forthcoming real operation. In particular, according to the varying ambient conditions, the influence of different operation modes of the prototype plant are evaluated. The dynamic simulation analysis has shown an interesting performance of the system in terms of annual operating hours, power production and conversion efficiencies. More precisely, the organic Rankine cycle unit is able to operate for more than 3100 h/year, achieving the design performance when solar power is sufficiently high, producing about 5100 kWhe/year. For the considered operating set-point temperatures of the thermal energy storage, the plant is able to reach high conversion efficiency also when the organic Rankine cycle unit is supplied by discharging the energy stored in the storage tank, for about 800 h/year. Hence, the work has provided some useful insights into the best working conditions of such micro combined heat and power system to be integrated in residential buildings. Moreover, the analysis could serve as a general guide for the design and optimization of the mutual interactions of the different subsystems in small-scale concentrated solar organic Rankine cycle plants

green energy assisted frost prevention a conceptual framework

Abstract Solar photovoltaics (PV) is a popular method of green energy-based electricity generation for regions with rich solar radiation. In this paper, we introduce a conceptual framework where PV can be used for multi-purposes: electricity generation and frost prevention, specifically for frost prevention of apricot orchards. After introduction of the conceptual framework, the system modelling, optimization, and control/automation research challenges for such a multi-purpose use are summarized. This paper targets at opening a new application area and the associated research rooms for PV systems

Friends for Free: Self-Organizing Artificial Social Networks for Trust and Cooperation

By harvesting friendship networks from e-mail contacts or instant message "buddy lists" Peer-to-Peer (P2P) applications can improve performance in low trust environments such as the Internet. However, natural social networks are not always suitable, reliable or available. We propose an algorithm (SLACER) that allows peer nodes to create and manage their own friendship networks. We evaluate performance using a canonical test application, requiring cooperation between peers for socially optimal outcomes. The Artificial Social Networks (ASN) produced are connected, cooperative and robust - possessing many of the disable properties of human friendship networks such as trust between friends (directly linked peers) and short paths linking everyone via a chain of friends. In addition to new application possibilities, SLACER could supply ASN to P2P applications that currently depend on human social networks thus transforming them into fully autonomous, self-managing systems

Simulation analysis of an innovative micro-solar 2kWe Organic Rankine Cycle plant coupled with a multi-apartments building for domestic hot water supply

Combined heat and power plants driven by renewable energy sources (RES) are becoming more and more popular, given the energy transition towards the integration of more renewable energy sources in the power generation mix. In this paper an innovative micro-solar 2kWe/18kWth Organic Rankine Cycle system, which is being developed by the consortium of several Universities and industrial organizations, with the funding from EU under the Innova MicroSolar project, is considered. In particular, its application to supply electricity and thermal energy for Domestic Hot Water (DHW) in a residential building is investigated by means of simulation analysis. Different Domestic Hot Water supply plant configurations are evaluated and the design parameters are varied in order to determine the best configuration to recover as much energy as possible from the ORC, while maintaining the final users’ comfort. It was found out that with the considered plant around 67% of the Domestic Hot Water energy demand of 15 apartments can be satisfied with a water storage tank of 10’000 liters. However, in order to always guarantee the supply water temperature, a back-up boiler, which serves directly the final users when needed, is requested

Design energy flexibility for Italian residential buildings

Having energy flexible buildings is a very important aspect to enable the application of smart demand side management strategies (DSM). DSM is getting more and more relevance in energy systems planning and operation due to the overall increasing energy demand. An energy flexible building is intended to be able to change, in a planned manner, the shape of its energy demand curve, electrical and thermal, while the comfort of the end-users is still guaranteed. The objective of this study is to develop a methodology that allows to classify buildings according to their potential to provide energy flexibility on the basis of their design features. Similarly to the energy performance label, this methodology aims to be a means to extend the energetic characterization of a building also to its energy demand management ability. In this paper the thermal energy demand of buildings (supplied by electrically driven devices, e.g. heat pumps) is mainly taken into account. A quantification method is introduced to estimate the thermal energy demand flexibility. Since the potential to manage the energy demand of a building is strongly influenced by dynamic boundary conditions, “test conditions” have been defined in order to make the method repeatable, not dependent on the specific operational conditions, but more on the design specifications. In this manner the evaluation takes into account only the intrinsic aspects of the building, identified by the construction characteristics and the type of distribution system for the heating and cooling apparatus. Different buildings typologies, representing the most common Italian residential buildings, are considered. Their models are simulated in TRNSYS. The results show a great potential as energy flexibility providers for the latest generation buildings (from 2006 onwards) with a good level of insulation and a radiant system served by a heat pump

Energy flexibility curves to characterize the residential space cooling sector: The role of cooling technology and emission system

none3Space cooling of buildings shows an increasing trend in energy use worldwide. The exploitation of the energy flexibility reserve obtainable from buildings cooling-loads management can have an important role to improve the security and the reliability of the electricity power grid. Many studies in literature assess the energy flexibility potential of air conditioning systems; however, the role of the specific cooling technology is always scarcely explored. The objective of this work is to provide an evaluation of the operational energy flexibility that can be obtained involving the most common residential space cooling technologies, paying particular attention to the distribution system (e.g., all-air system, fan-coil units with and without the addition of a thermal energy storage and hydronic massive systems). The analysis is carried out with dynamic simulation models for the various cooling systems involved. Results show a great influence of the adopted distribution system in the implementation of a flexibility request. In particular, all-air systems (i.e. split systems) show the lower flexible behavior (they require up to 10 h of precooling to be off during a peak hour). Whereas the adoption of fan coil units coupled with a thermal energy storage allows to implement different peak shaving strategies without compromising the indoor air temperature with low drawback effects in terms of anticipated electricity overconsumptions (no precooling of the air is required and a maximum of 23 % increase in electricity consumed in the time before the event occurs, with a reduction of 16 % in subsequent hours). In case of ceiling cooling systems, results highlight that as the thermal inertia of the system increases, the indoor conditions are less affected, but the anticipated overconsumption of the heat pump increases (for the same Demand Response event the electricity overconsumption goes from + 67 % to +116 %, passing from ceiling panels to concrete ceiling). The results obtained from this analysis are then used to draw flexibility curves, which aim at providing a characterization of the flexibility of a cooling system. They can be used to predict, for typical installations, the system behavior in presence of a peak power reduction strategy in terms of pre-cooling duration, energy use variation and modification of the temperature comfort bandwidth. Such predictions are important because they can provide insights on the design and operation of space cooling systems in demand side management strategies.openMugnini A.; Polonara F.; Arteconi A.Mugnini, A.; Polonara, F.; Arteconi, A

Quantification of the energy flexibility of residential building clusters: Impact of long-term refurbishment strategies of the italian building stock

A major refurbishment of the building stock is necessary to achieve the objectives of the energy transition. In addition to decreasing the overall energy demand, the energy efficiency of buildings can create a non-negligible reserve of flexibility and resilience for the entire energy system. Long-term refurbishment strategies can have an impact on such potential of the building sector that is still not widely exploited. In this work the objective is to quantify the influence of long-term refurbishment strategies, planned until 2050, on the energy flexibility reserve of the entire building stock. Reference clusters of residential buildings have been modelled to represent the current and future scenarios of the Italian building stock. Lumped parameter models representing archetypes of residential buildings are implemented to represent the Italian building stock. Current statistics on the composition of the building stock have been combined with European refurbishment targets to 2050 to define the current and future scenarios of the Italian building stock. Since the topic of quantifying the energy flexibility of clusters of buildings is still rather open, this study proposes an analysis based on a combination of different indicators derived from the literature and proposed ad hoc by the authors. They include flexibility curves, that correlate the demand of the cluster to the penalty signal (e.g., a price signal), and flexibility indicators for the comparison between the scenarios with and without activation of energy flexibility. The results quantify the impact of Italian building stock refurbishment strategies on flexibility reserve and efficiency targets. It has been estimated that the maximum electrical power shiftable (both upward and downward) by activating the energy flexibility of the whole building stock can reach 17.9 GWe in 2050. While in terms of energy, the following amounts of average daily shiftable energies have been obtained: from −34.4 to + 13.6 GWhe in 2030, from −75.4 to + 16.2 GWhe in 2040 and up to −113.5 to + 45.8 GWhe in 2050, that represent around 2% of the present Italian electricity demand

Energy flexibility as additional energy source in multi-energy systems with district cooling

none4The integration of multi-energy systems to meet the energy demand of buildings represents one of the most promising solutions for improving the energy performance of the sector. The energy flexibility provided by the building is paramount to allowing optimal management of the different available resources. The objective of this work is to highlight the effectiveness of exploiting building energy flexibility provided by thermostatically controlled loads (TCLs) in order to manage multienergy systems (MES) through model predictive control (MPC), such that energy flexibility can be regarded as an additional energy source in MESs. Considering the growing demand for space cooling, a case study in which the MPC is used to satisfy the cooling demand of a reference building is tested. The multi-energy sources include electricity from the power grid and photovoltaic modules (both of which are used to feed a variable-load heat pump), and a district cooling network. To evaluate the varying contributions of energy flexibility in resource management, different objective functions- namely, the minimization of the withdrawal of energy from the grid, of the total energy cost and of the total primary energy consumption-are tested in the MPC. The results highlight that using energy flexibility as an additional energy source makes it possible to achieve improvements in the energy performance of an MES building based on the objective function implemented, i.e., a reduction of 53% for the use of electricity taken from the grid, a 43% cost reduction, and a 17% primary energy reduction. This paper also reflects on the impact that the individual optimization of a building with a multi-energy system could have on other users sharing the same energy sources.openMugnini A.; Coccia G.; Polonara F.; Arteconi A.Mugnini, A.; Coccia, G.; Polonara, F.; Arteconi, A

Energy flexible CHP-DHN systems: Unlocking the flexibility in a real plant

The purpose of this paper is to identify and analyze the impact of flexibility enablers in cogeneration and district heating network (CHP-DHN) plants by means of a real case study located in central Italy. A wider definition of energy flexibility applicable to the entire energy supply chain (i.e. production, transport and usage) is used in this analysis. In particular the flexibility is intended as the capability of each part of the system to produce a variation in its load curve, while ensuring the required performance. In this sense energy efficiency technologies, the use of energy storage and advanced control techniques can be seen as flexibility enablers potentially available in each section of the energy system. The innovative contribution of this work is to propose flexibility strategies in compliance with the constraints imposed by both the managers and users. The study aims to show possible ways to activate flexibility services to be used with known instruments and to quantify their impact with a simulation-based approach. In particular, three different flexibility instruments are identified in different sections of the plant: (i) the use of a thermal energy storage (TES) in the generation side, (ii) the optimal management of the DHN supply temperature (energy distribution side) and (iii) the management of the thermostatically controlled loads (TCLs) of the final users (demand side) connected to the network. Through the implementation of simulation models calibrated with available measurements, the influence of these flexibility instruments on the energy/environmental performance is evaluated in comparison to the current configuration of the plant. Results confirm the great impact of the TES to increase the CHP working hours and, as a consequence, a primary energy saving increase is obtained in mid-season and in summer season. Whereas the optimal management of the water supply temperature in the DHN allows to obtain 1% fuel reduction in a typical winter week and 2% in a typical summer week. As far as the activation of the demand side flexibility is concerned, the effect of the management of TCLs on energy conservation is demonstrated: 1 °C reduction of the setpoint of all the residential users during a typical winter day produces a 7.3% reduction of the DHN thermal demand. However, its impact on the generation side (i.e. to reduce the electricity/thermal production of the CHP at specific times) is limited due to the characteristics of the considered CHP plant (the CHP engine is sized to cover only the thermal baseload and it scarcely affected by thermal demand variations). The analysis proposed helps to obtain valuable hints on unlocking the energy flexibility in CHP-DHN plants useful for a better management of such systems

Modelling Calcium Signal Intensity Difference Between Cells

Cell signaling involves the transmission of a signal from a sending cell to a receiving cell. Calcium ions (Ca2+) are a widely used type of messenger. In this study the evolution over time of calcium signal intensity and how these evolutions depend on the four groups of cells of subjects with different health condition was investigated. A longitudinal data analysis based on 110 subjects was used and to account non-linearity and correlated nature of the data, non-linear mixed model was used. Based on the exploratory data analysis result supported with CurveExpert professional software the model used has sigmoid structure. From the result, the rate of change of average signal intensity was nearly 0.033 and the time at which the rate of change of average calcium signal intensity reaches its maximum (i.e. the inflection point) was nearly 198 seconds. Furthermore, there were statistically significant differences in average calcium signal intensity between the groups. It is also observed that significant differences between mild hyperplasia and benign tumor patient’s cells and also between malignant tumor and healthy subject’s cells. Keywords: Calcium, Cell Signaling, Non Linear Mixed Model, Random Effect, Signal Intensit