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

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 flexibility and demand management in buildings

Lo sfruttamento della flessibilità energetica negli edifici rappresenta una delle soluzioni più promettenti per consentire il passaggio a sistemi energetici ad alta penetrazione di rinnovabili. Disporre di un edificio flessibile significa poter applicare efficientemente strategie di gestione della domanda (Demand Side Management, DSM) che rappresentano uno degli aspetti principali caratterizzanti il concetto di Smart Grid. Il DMS è definito come l'insieme di tutte quelle strategie volte a influenzare gli usi dell'elettricità degli utenti in modo da produrre cambiamenti nella forma della loro curva di carico. Data la crescente domanda elettrica del settore residenziale, soprattutto per la diffusione di impianti di riscaldamento e raffrescamento alimentati elettricamente (es. split e pompe di calore), gli edifici mostrano una predisposizione a produrre variazioni programmate della loro domanda elettrica, grazie ai diversi livelli di inerzia termica in essi già disponibile (es. massa termica dell’involucro o dispositivi dedicati come serbatoi di acqua calda o fredda). Inoltre, grazie a tecniche di controllo avanzate, possono sfruttare diverse fonti energetiche per soddisfare i propri fabbisogni termici, riducendo al contempo i prelievi dalla rete elettrica. Il lavoro presentato in questa tesi si inserisce in questo contesto. L'obiettivo è quello di fornire un'analisi dei diversi aspetti che caratterizzano la flessibilità ottenibile dalla gestione dei carichi termici ed elettrici negli edifici residenziali dotati di pompe di calore. L'analisi si estende progressivamente dal contesto dello scenario progettuale dei singoli edifici a quello operativo degli aggregati. Nella tesi inoltre sono presentate metodologie innovative di quantificazione in aggiunta alla simulazione di diversi casi di studio. In generale, tutti i risultati consentono di confermare la potenzialità degli edifici nella fornitura di servizi di flessibilità energetica.The exploitation of energy flexibility in buildings represents one of the most promising solutions to allow the transition to energy systems with a high penetration of renewable energy sources. Having a high flexible building means to be able to efficiently apply demand side management strategies (DSMs) which represent one of the main aspects characterizing the concept of Smart Grid. DMS is defined as the set of all those strategies aimed at influencing customer uses of electricity in ways that will produce desired changes in the utility’s load shape. Given the increasing electricity demand in the residential sector, especially for the diffusion of heating and cooling systems electrically powered (e.g., split systems and heat pumps), buildings show a predisposition to produce variations in the electrical demand, due to the different levels of thermal inertia already available in them (e.g., the thermal mass embedded in the envelope or dedicated devices as cold and/or hot water tank). Moreover, thanks to advanced control techniques, buildings could exploit different energy sources to satisfy their thermal requirements, while reducing withdrawals from the power grid. The work presented in this thesis fits into this context. The objective is to provide an overview of the different aspects that characterize the energy flexibility obtainable from the management of thermal and electrical loads in residential buildings equipped with heat pumps. The analysis is gradually extended from the context of the design scenario of single buildings to the operative analysis of clusters of buildings. Novel methodologies of quantification and evaluation are introduced in addition with the examination of different simulation-based case studies. In general, all the analyses allow to confirm the great potential of residential buildings in providing energy flexibility services

Energy flexible buildings: A methodology for rating the flexibility performance of buildings with electric heating and cooling systems

© 2019 In the present energy scenario, buildings are playing more and more as energy prosumers. They can use and produce energy and also actively manage their energy demand. The energy flexibility quantifies their potential to adjust the energy demand on the basis of external requests. The objective of this paper is to propose a method for buildings energy flexibility labelling at design conditions in the same fashion as the energy performance label. The flexibility quantification is based on the calculation of four flexibility parameters, which contribute to the definition of the Flexibility Performance Indicator. In order to assess the Flexibility Performance Indicator, buildings dynamic simulations are necessary and the boundary conditions (i.e. demand response event, representative day, comfort constraints)to be considered during the evaluation are provided as part of the proposed methodology. The method was applied to different Italian buildings, which differ for geographic location and design specifications and, in particular, the effects of building structure, heating/cooling systems and energy storage systems were compared. Results show that the climatic conditions affect the flexibility performance, while the building feature more relevant is the thermal mass of the building envelope, more than that provided by the distribution system. A sensitivity analysis to evaluate how the results are influenced by the proposed boundary conditions was also performed. Their choice confirms to have a relevant impact on flexibility quantification, then their unique definition has a paramount importance within this methodology.status: publishe

Demand response strategies in residential buildings clusters to limit HVAC peak demand

Due to the increasing spread of residential heating systems electrically powered, buildings show a great potential in producing demand side management strategies addressing their thermal loads. Indeed, exploiting the intrinsic characteristics of the heating/cooling systems (i.e. the thermal inertia level), buildings could represent an interesting solution to reduce the electricity peak demand and to optimize the balance between demand and supply. The objective of this paper is to analyse the potential benefits that can be obtained if the electricity demand derived from the heating systems of a building cluster is managed with demand response strategies. A simulation-based analysis is presented in which a cluster of residential archetypal buildings are investigated. The buildings differ from each other for construction features and type of heating system (e.g. underfloor heating or with fan coil units). By supposing to be able to activate the energy flexibility of the single building with thermostatic load control, an optimized logic is implemented to produce programmatically an hourly electricity peak reduction. Results show how the involvement of buildings with different characteristics depends on the compromise that wants to be achieved in terms of minimization of both the rebound effects and the variation of the internal temperature setpoint

Selection maps based on multi-objective optimization of design and control for residential heat pumps systems

Although heat pumps are one of the most promising technologies to support the energy transition in space heating sector more knowledge is needed on how to design their installation for different plant configuration and control strategy. In this work a methodology to obtain selection maps, which consider both the sizing of the system and the influence of the control strategy, is proposed. Both the optimal design parameters and control strategies are evaluated to minimize seasonal energy consumption and investment cost. The methodology is applied to a reference Italian residential building. Results show that, regardless of the objective function, the optimal size of the heat pump increases as the temperature level of the hot source increases. Furthermore, the selection maps show how the optimal sizing varies according to the control strategy (i.e., fixed supply temperature or compensation curve) and the presence of a thermal storage device. In general, however, the proposed methodology aims to extrapolate the link between the design and the operation of a heat pump system. Therefore, the selection maps can represent an important instrument to select the main features of the installation depending on the operating conditions

Energy flexibility in residential buildings clusters

The building sector represents one of the most energy-consuming worldwide and a great part of its consumption is accounted for residential demand for space heating and cooling. Although it is necessary to promote the buildings energy efficiency, energy flexibility is also of paramount importance to optimize the balance between demand and supply. In fact, an energy flexible building is defined as 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. Objective of this work is to exploit the energy demand management ability of different buildings composing a cluster, when their aggregated demand derived from electric heating systems (i.e. heat pumps) is subject to demand response (DR) strategies. Users with different occupancy profile are considered. By supposing to be able to activate the energy flexibility of the single building with thermostatic load control, different scenarios of cluster composition are evaluated in order to provide guidelines to implement optimal strategies for energy flexibility exploitation without drawback effects connected to the event

Potential of District Cooling Systems: A Case Study on Recovering Cold Energy from Liquefied Natural Gas Vaporization

District cooling systems (DCSs) are networks able to distribute thermal energy, usually as chilled water, from a central source to industrial, commercial, and residential consumers, to be used for space cooling/dehumidification. As cooling demand will increase significantly in the next decades, DCSs can be seen as efficient solutions to improve sustainability. Although DCSs are considered so relevant for new city developments, there are still many technical, economic, and social issues to be overcome to let such systems to spread out. Thus, this paper aims to highlight the advantages and issues linked to the adoption of DCSs for building cooling when cold is recovered from a specific application. A case study based on liquified natural gas (LNG) cold energy recovery from the transport sector is presented. Starting from the estimation of the free cooling availability, a DCS design method is proposed and the potential energy saving is investigated. Results show that a DCS using the cold waste derived from LNG can provide a relevant amount of electricity saving (about 60%) for space cooling compared to traditional solutions, in which standard air conditioning systems are installed in every building