Nearly Zero Energy multi-functional Buildings - Energy and Economic evaluations

Building energy renovation is one of the pillars upon which the 2050 European low-carbon goals are based. Simultaneously, building energy renovation is widely recognized as the trump card for the new start of European economy. However, at present the renovation rate of the existing building is very low throughout Europe (approximately 1%) and investments in high performing buildings are generally mistrusted by stakeholders, due to their high capital costs. In this context, this PhD thesis dedicated its efforts to investigate from the energy and financial perspective the consequences of buildings renovation in the European scene. Particularly, the research boundaries were delineated by focusing on non-residential, multi-functional buildings, that are nowadays poorly studied due to their heterogeneous nature. In this view, the thesis’ contributions were addressed at three levels: a) multi-functional buildings as archetypes to input in energy models for long-term energy analysis; b) multi-functional buildings used to test the financial viability of energy efficiency projects, in view of reaching the nearly Zero Energy performance level. As these analyses necessarily require case studies, the attention was directed towards a specific type of multi-functional buildings, hotels; c) multi-functional buildings as test-bed to assess the impact of co-benefits on the financial performances of energy efficiency projects. Once again, hotel buildings were selected for the development of the detailed analyses. To include archetypes of multi-functional buildings in bottom-up building energy models, a new modelling method was proposed. The method provides a rationale for the classification of energy end-uses into typical and extra, so that the modeling problem is simplified and a coherent use of well-established Reference Buildings modelling methods is allowed. Then, the focus of the research was narrowed to the hotel sector, which was found to lack of reliable energy performance benchmarks and effective performance-based greens labels. Case study buildings were object of energy and financial evaluations. On one side, real hotels were analyzed to test the application of the EU imposed cost-optimal methodology as a support tool to guide private investors’ investment decisions. On the other side, an Italian Reference Hotel was modelled and the cost-optimal methodology was applied to investigate the existing energy and financial gaps between cost-optimal and Nearly Zero Energy performance level in Italy. From both perspectives, findings converged to similar conclusions: high performing retrofit are not financially viable, if avoided energy costs are the only operational benefits accounted for. Starting from these outcomes, the thesis investigated how valuation procedures could be exploited to make NZEB retrofit solutions appealing for private investors. Based on a literature review of the co-benefits of energy efficiency projects, 2 different strategies were pursued and tested on the Italian Reference Hotel. The first approach proposed to monetize co-benefits of energy efficiency interventions based on literature and to include them in the well-established cost-optimal methodology. Results highlighted that co-benefits related to the market appreciation of a retrofitted hotel can drastically change the perception of the financial convenience of an ambitious retrofit project. In the latter strategy, the issue of monetizing non-energy benefits was faced directly: a technique to value non-market goods was applied to monetize comfort. Findings proved that hotels guests’ willingness to pay for comfortable indoor conditions is higher than the hoteliers’ extra costs for providing them. Due to the context-dependent nature of co-benefits, the findings of the 2 applications do not represent generally applicable quantitative benchmarks. Nonetheless, they confirm the leading role that literature attribute to co-benefits in the success of energy efficiency projects

Evolution of magnetic fields and energetics of flares in active region 8210

To better understand eruptive events in the solar corona, we combine sequences of multi-wavelength observations and modelling of the coronal magnetic field of NOAA AR 8210, a highly flare-productive active region. From the photosphere to the corona, the observations give us information about the motion of magnetic elements (photospheric magnetograms), the location of flares (e.g., H$\alpha$, EUV or soft X-ray brightenings), and the type of events (H$\alpha$ blueshift events). Assuming that the evolution of the coronal magnetic field above an active region can be described by successive equilibria, we follow in time the magnetic changes of the 3D nonlinear force-free (nlff) fields reconstructed from a time series of photospheric vector magnetograms. We apply this method to AR 8210 observed on May 1, 1998 between 17:00 UT and 21:40 UT. We identify two types of horizontal photospheric motions that can drive an eruption: a clockwise rotation of the sunspot, and a fast motion of an emerging polarity. The reconstructed nlff coronal fields give us a scenario of the confined flares observed in AR 8210: the slow sunspot rotation enables the occurence of flare by a reconnection process close to a separatrix surface whereas the fast motion is associated with small-scale reconnections but no detectable flaring activity. We also study the injection rates of magnetic energy, Poynting flux and relative magnetic helicity through the photosphere and into the corona. The injection of magnetic energy by transverse photospheric motions is found to be correlated with the storage of energy in the corona and then the release by flaring activity. The magnetic helicity derived from the magnetic field and the vector potential of the nlff configuration is computed in the coronal volume. The magnetic helicity evolution shows that AR 8210 is dominated by the mutual helicity between the closed and potential fields and not by the self helicity of the closed field which characterizes the twist of confined flux bundles. We conclude that for AR 8210 the complex topology is a more important factor than the twist in the eruption process

Defining the Reference Hotel – toward nearly Zero Energy Hotels design

The ever mentioned “cost optimality” and “nearly Zero Energy Buildings” concepts, introduced by the EPBD recast, are still a blurry target at EU Member States’ level for non-residential buildings. Among the uncertainties hampering a quantitative description of cost optimal and nearly Zero Energy (nZE) level of energy performance in these building categories, the definition of the “typical energy use of a building” [1], is a key issue. Indeed, in non-residential buildings the energy use for maintaining occupants’ comfort (identified as the “typical”) is complementary to the energy use for maintaining the offered services’ quality. Given the general issue, the paper focuses on hotels. As an initial step toward nZE hotels, this study presents the definition of an existing Reference Hotel. First, typical and extra functions of a small-medium hotel were defined. Then, the general procedure for defining a Reference Hotel (RH) was drafted and an Italian RH was modelled: internal layout, envelope, systems features and operation profiles were identified. A dynamic energy simulation of the model was run to evaluate its energy performances. Results were then compared to benchmarks from literature. Next steps will exploit the Reference Hotel to investigate potential relations with the energy uses for extra services and to propose cost-optimal and energy efficient retrofit measures

NZEB, cost- and comfort-optimal retrofit solutions for an Italian Reference Hotel

Building upon the implementation of EBPD recast in the large majority of EU Member States, this paper studied how far cost-optimality is from the Nearly Zero Energy Building (NZEB) performance level for an Italian Reference Hotel (RH) undergoing major renovations. The energy performances of retrofit options for the RH were compared with the Italian NZEB requirements. Simulations results confirmed that the Italian NZEB target is reachable. However, the financial analysis of these retrofit options denounced a worrying gap between financially interesting solutions and NZEB ones. Then, through a novel comfort-optimal approach, the comfort-related consequences of the proposed retrofit options were investigated

hybridGEOTABS project : MPC for controlling the power of the ground by integration

GEOTABS is an acronym for a GEOthermal heat pump combined with a Thermally Activated Building System (TABS). GEOTABS combines the use of geothermal energy, which is an almost limitless and ubiquitous energy source, with radiant heating and cooling systems, which can provide very comfortable conditioning of the indoor space. GEOTABShybrid refers to the integration of GEOTABS with secondary heating and cooling systems and other renewable and residual energy sources (R2ES), offering a huge potential to meet heating and cooling needs in office buildings, elderly care homes, schools and multi-family buildings throughout Europe in a sustainable way. Through the use of Model Predictive Control (MPC), a new control-integrated building design procedure and a readily applicable commercial system solution in GEOTABShybrid, the overall efficiency of heating and cooling will be significantly improved in comparison to current best practice GEOTABS systems and its competitiveness will be strengthened. The present paper is the first of a series that first introduces the hybridGEOTABS project and then specifically focuses on the control-related aspects of the hybridGEOTABS solution, the MPC, providing some interesting insights of its potential development

A customized modelling approach for multi-functional buildings - Application to an Italian Reference Hotel

In the forthcoming European low-carbon energy system, the building stock plays a major role in the demand sector. Therefore, in order to develop robust scenario analysis towards the success of the lowcarbon goals, a trustful characterization of the building stock is required. Reference Buildings are often the base of these building stock models, but, at present, an uneven level of development between residential and non-residential Reference Buildings is detected. The present paper contributes to fill this knowledge gap by proposing a method to model Reference multi-functional Buildings. Multi-functional buildings represent an important share of the non-residential buildings stock, by embracing all buildings hosting different activities under the same roof. In order to trustfully depict their energy performances, the EU definition of Reference Buildings have to be updated. To this purpose, this study proposes a rationale to describe and model these buildings, based on the distinction between their typical and extra energy uses. In order to test the proposed methodology, it was applied to the definition a Reference Hotel in Italy, with the additional aim to provide support material to the national energy and tourism policies

Progettare edifici resilienti al comportamento degli utenti

Allo stato attuale, la previsione dei consumi reali di un edificio risente di una poco accurata descrizione delle variabili influenzanti l’uso dell’energia, per lo più legate all’utilizzo dell’edificio, tra cui spicca il comportamento degli utenti. Lo scopo di questa ricerca è valutare la capacità dell’ involucro di limitare l’influenza degli utenti sui consumi energetici di un edificio, ovvero di determinare il suo grado di resilienza per differenti ipotesi di involucro. L’analisi è stata svolta su un edificio per uffici di riferimento servendosi di un software di simulazione energetica dinamica che supporta modelli comportamentali stocastici, focalizzandosi sulle azioni su finestre e schermature mobili. Sono state simulate cinque zone termiche con caratteristiche ed esposizioni differenti, nei climi di Stoccolma (nordico), Francoforte (continentale) ed Atene (mediterraneo). Dai risultati è emerso che la presenza combinata di involucro massivo, ridotta superficie vetrata e schermature fisse comporta sia i minori consumi per riscaldamento e raffrescamento, sia la maggior resilienza dell’edificio rispetto al comportamento dell’utente. Accanto agli indirizzi progettuali, lo studio dimostra le potenzialità dei software di simulazione quali strumenti per una progettazione consapevole: nel caso specifico la descrizione realistica del comportamento degli utenti ha consentito di valutare la capacità di un edificio di mantenere prestazioni costanti nonostante cambi di utenza

Smart meters and energy savings in Italy: Determining the effectiveness of persuasive communication in dwellings

To secure a sustainable energy development in the residential sector, attitudes and human behavior need to be modified toward more efficient and conscious energy usage. The goal of this research is to assess evaluations and to test the effectiveness in reducing domestic electricity consumption. The aim of the smart monitoring system we evaluate is to provide households with a user-friendly tool that improves awareness of energy behavior in homes, enabling better management via the visualization of consumption and persuasive tailored information on domestic electricity use. In our study, the system was tested on 31 Italian families selected among volunteers all over Italy, participating to the first trial phase from October 2012 to November 2013. A combination of persuasive communication strategies such as graphical real-time and historical feedback based on real data and comparison tools to encourage competitiveness against “similar” households were provided to users through a domestic user-friendly interface. In addition, personalized energy saving prompts were sent via web-newsletters to trial users. The study concludes that energy related persuasive communication is effective in reducing electricity consumption in dwellings on average −18% and up to −57%

The role of hotels in shaping a sustainable built environment

Because of its function and nature, tourism sector has the potential to shape cities and citizens. The impact of tourism activities on global CO2 is around 5% and its reduction is both a technically achievable and a socially beneficial tar¬get. For instance, in the hotel sector on one side the use of energy efficiency measures and renewable energy is far below its real potential; on the other side, due to the number of guests they host, hotels have the potential to act as an example of energy responsibility for other industries, as well as for individ¬uals. At the European level, the issue of reducing hotels’ energy consumption goes along with the aggressive goals set for the next decades for energy use reduction. In this framework, this paper presents the application of the Europe-wide known cost-optimal methodology to an existing hotel. Indeed, taking into account financial aspects is crucial for the market uptake of sustainable good practices in real, business-driven world. A small-medium mountain hotel lo¬cated nearby Torino was selected as baseline model for the analysis and a number of energy efficiency measures were defined and implemented in a building energy simulation software. The obtained cost-optimal level of energy performance proved that proper combinations of existing technolo¬gies could lead to significant reduction of energy use. However, a critical dis¬cussion of the implemented methodology led to the proposal of different eval-uation parameters for cost-optimal levels of energy performance for hotels, as a possible solution to catch stakeholders’ interest toward green investments