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

Carbon Dioxide + Fluoromethane and Nitrous Oxide + Fluoromethane: Solid−Liquid Equilibria Measurements

A recently built experimental setup was employed for the estimation of the solid-liquid equilibria (SLE) of alternative refrigerant systems. The behavior of two binaries, that is, carbon dioxide + fluoromethane (CO2 + R41) and nitrous oxide + fluoromethane (N2O + R41), was measured down to temperatures of 126.5 K. To confirm the reliability of the apparatus, the triple points of the pure fluids constituent of the binary systems were measured. All triple-point data measured revealed a generally good consistency with the literature. The results obtained for the mixtures were corrected by the Rossini method and interpreted by means of the Schröder equation. © 2010 American Chemical Society

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

P-V-T Behavior of 2,3,3,3-Tetrafluoroprop-1-ene (HFO-1234yf) in the Vapor Phase from (243 to 373) K

The P-V-T properties of 2,3,3,3-tetrafluoroprop-1-ene (CF 3 CFdCH 2 , HFO-1234yf), an environmentally friendly refrigerant, were measured using a constant volume apparatus. Measurements were carried out at temperatures from (243 to 373) K and at pressures from (84 to 3716) kPa. A total of 136 experimental points, taken along 12 isochores, were obtained. Our experimental results were compared with a preliminary equation of state. The measurements were also regressed to the Martin-Hou equation of state. No other data on this fluid were found in the literature for the superheated region

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

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

Demand side management analysis of a supermarket integrated HVAC, refrigeration and water loop heat pump system

Supermarkets are intensive energy consumers because of a high electricity demand, mainly due to refrigeration utilities. Thus, in this work a supermarket integrated HVAC, refrigeration and water loop heat pump (WLHP) system was analyzed according to a demand side management approach, adopting a demand response strategy coupled with real-time pricing predictive rule based controls. The system was modeled with TRNSYS and several DR strategies were applied to both the space heating/cooling and the WLHP to determine the plant configuration with the most effective electricity cost saving. It was found that two setups guarantee the highest economic savings. The first consists of a predictive rule based control applied to the space heating/cooling only, which is basically inexpensive and allows an annual cost saving of 4.06% respect to the baseline configuration. The second, instead, combines predictive rule based controls applied to both the space heating/cooling and the WLHP auxiliary heater, and shows the best performance with the adoption of a 200\u202fm3 water-based thermal energy storage. Respect to the baseline, this configuration provides an annual cost saving of 4.67%

Sand transport in multiphase flow mixtures in a horizontal pipeline: An experimental investigation

An inherent problem with both oil and natural gas production is the deposition of sand particles in pipeline, which could lead to problems such as excessive pressure drops, equipment failure, pipeline erosion, and production decline. The characterization of sand particles transport and sedimentation in different flow systems such as sand–multiphase mixtures is vital to predict the sand transport velocity and entrainment processes in oil and gas transportation pipelines. However, it seems that no model exists able to accurately characterize the sand transport and deposition in multiphase pipeline. In fact, in the last decade several researchers tried to extend the modeling of liquid-solid flow to gas-liquid-solid flow, but no significant results have been obtained, especially in slug flow condition due to the complexity of the phenomenon. In order to develop and validate a mathematical model properly formulated for the calculation of the sand critical deposition velocity in gas-liquid flow, more and more experimental data are necessary. This paper presents a preliminary experimental study of three phase flows (air-water-sand) inside a horizontal pipe and the application of the sand-liquid models present in literature. Significant observations were made during the experimental study from which several conclusions were drawn. Different sand flow regimes were established by physical observation and data analysis: fully dispersed solid flow, moving dunes and stationary bed. The critical deposition velocities were determined at different sand concentrations. It was concluded that sand transport characteristics and the critical deposition velocity are strongly dependent on the gas-liquid flow regime and on sand concentration. Keywords: Sand transport, Multiphase flow, Minimum transport condition, Deposition, Experimental investigation, Oil and ga