Download - On an innovative integration strategy of renewable energy system in historic building with public function

On an innovative integration strategy of renewable energy system in historic building with public function Strategia innovativa di integrazione con fonti rinnovabili del sistema impiantistico di un edificio storico con funzione pubblica

ANNA LAURA PISELLO1 – ALESSANDRO PETROZZI2 – VERONICA LUCIA CASTALDO1 – FRANCO COTANA1 1 CIRIAF- University of Perugia, Italy 2 Libera Università della Sicilia centrale "Kore", Italy

SUMMARY

Energy efficiency of existing buildings is becoming an increasingly important re-search issue, given the slow building renovation and new construction development in Europe. Additionally, most of the buildings in the old city centers in Mediterranean area, and all around Europe in general, often present important architectural and artistic ele-ments to be preserved even in retrofit interventions. This aspect makes the energy effi-ciency optimization even more difficult to implement, and historic buildings are typical-ly considered as low performance buildings by definition. In this panorama, innovative strategies and integrated assessment to be specifically designed in historic buildings rep-resent a fundamental research development, aimed at improving the environmental sus-tainability of Italian and European city centers. This paper concerns the integrated evalu-ation of multiple retrofit scenarios on a historic building case study for public auditorium use. Several active technologies and passive solutions are compared in terms of (i) cost, (ii) energy performance, (iii) technical feasibility, for intrinsic constraints deriving from the characteristics of the ancient structures and the positioning of the case study. This building is a large space built in the historical city walls, where the municipality office would like to install an auditorium and training space for public use. Specific solutions have been elaborated focusing on the building characteristics and the final use of each thermal zone. The overall cost-benefit assessment shows how the reduction of the condi-tioned volume in association with (i) the integrated geothermal plant and (ii) the methane boiler with absorption chiller represents the best overall solution after three years from the construction in terms of primary energy requirement for (i) cooling and (ii) heating, respectively.

1

Edifici di valore storico: progettare la riqualificazioneUna panoramica, dalle prestazioni energetiche alla qualità dell’aria internaHistorical and existing buildings: designing the retrofitAn overview from energy performances to indoor air quality

Roma, 26-27-28 febbraio 2014Rome, 26th-27th-28th February 2014

RIASSUNTO

L’efficienza energetica degli edifici esistenti sta diventando un tema di ricerca sempre più importante, data la lentezza dei processi di ristrutturazione edilizia e in gene-rale dello sviluppo del settore delle costruzioni in Europa. Inoltre, la maggior parte degli edifici situati nei centri storici nella zona del Mediterraneo e in tutta l'Europa spesso pre-senta elementi architettonici di elevato valore artistico- culturale che devono essere pre-servati nell’ambito di interventi di retrofit. Ciò rende il processo di ottimizzazione dell’efficienza energetica degli edifici esistenti ancor più difficoltoso da implementare, ed induce tipicamente a considerare gli edifici storici come edifici caratterizzati da basse prestazioni per definizione. In tale ottica, l’individuazione di apposite ed innovative stra-tegie di valutazione integrata degli edifici storici rappresenta uno sviluppo fondamentale della ricerca, nell’obiettivo di un miglioramento della sostenibilità ambientale di centri storici italiani ed europei.

Questo documento riguarda la valutazione integrata di molteplici scenari di retrofit energetico in relazione ad uno specifico edificio storico adibito ad auditorium, situato a Perugia, selezionato come caso di studio. In particolare, quattro soluzioni con tecnologie attive e passive sono confrontate in termini di (i) costo, (ii) rendimento energetico, e (iii) fattibilità tecnica, per la presenza di vincoli intrinseci derivanti dalle caratteristiche delle antiche strutture e dal posizionamento del caso di studio scelto. Tale edificio consiste in un grande spazio ricavato all’interno delle mura storiche della città, dove il Comune vor-rebbe posizionare un auditorium e uno spazio di formazione ad uso pubblico. Soluzioni specifiche sono state elaborate in base alle caratteristiche costruttive e all'uso finale di ciascuna zona termica. La valutazione complessiva costi-benefici mostra come la ridu-zione del volume condizionato in associazione a una caldaia a metano con assorbitore rappresenti la migliore soluzione in termini di fabbisogni di energia primaria per il ri-scaldamento. D’altro canto, la soluzione che prevede la riduzione del volume condizio-nato in associazione all’integrazione di un impianto geotermico risulta la tecnologia più performante in termini di fabbisogni di energia primaria per il raffrescamento, dopo tre anni dalla costruzione.

Key words: Renewable integrated energy, Historic buildings, Energy efficiency in build-ings

Parole chiave: Fonti di energia rinnovabili integrate, Edifici Storici, Efficienza Energeti-ca degli Edifici

1. INTRODUCTION

The importance of research renewable energies and energy efficiency in buildings has been addressed by many researchers in the last few years (Perez-Lombard et al., 2008; Lang, 2004). Therefore, International policies indicate the building sector as one of the most promising for energy saving as, according to the Intergovernmental Panel on Climate Change (IPCC), it has the greatest and cheapest potential for significant green-house gas emission reduction (Albino et al., 2012). In fact, the reduction of buildings’ energy consumption for heating, cooling, and lighting could dramatically decrease the

On an innovative integration strategy of renewable energy system

in historic building with public function

2

rate of depletion of world energy reserves and pollution of the environment (Omer, 2008).

Sustainable buildings’ solutions in terms of biomimetic design techniques, use of natural resources, and innovative envelope components in an environmental perspective have been widely investigated (John et al., 2005). Dincer (Dincer, 2000), for instance, explored the intimate connection between renewable energy and sustainable develop-ment, by reviewing all the actual environmental problems and the relative possible solu-tions in terms of energy storage technology, cogeneration, monitoring, and evaluation of energy indicators, energy conservation systems and buildings materials. Many other re-newable energy options aimed at making buildings more efficient and more environmen-tally sustainable have also been analyzed by Rezaie (Rezaie et al., 2011). In particular, a ground source heat pump for heating and cooling, a solar water heater for hot water pro-duction, and a photovoltaic panel were designed for different case studies. In this view, particular attention should be paid to the reduction of buildings’ energy consumptions through innovative energy systems (Chwieduk, 2003), in particular with reference to ex-isting historical and public buildings, typical of the Mediterranean urban areas, often characterized by significant historic-artistic heritage and intrinsic low energy efficiency constructions. Conservation effort in built cultural heritage has to be reformulated due to the new energy efficiency requirements to implement (Norrström, 2013). Specific re-search concerned the application of cool coatings able to increase the solar reflectance by more than 20% with acceptable visual appearance (Pisello et al., 2013) for specific applications in historic buildings. Additionally, low impact and low-cost methodology to reduce energy requirements of historic buildings through post-occupancy assessment (Pisello et al., 2012) could represent a suitable method, in large scale applications in par-ticular. A quantitative and qualitative analysis of buildings heritage was carried out by Fabbri (Fabbri, 2013), by evaluating the energy consumption incidence of historical buildings. Furthermore, Ascione (Ascione et al., 2011) suggested a multi-criteria ap-proach for the energy refurbishment of historical buildings, by proposing methodologies for the performance analysis and coupling experimental and numerical studies.

In this scenario, the purpose of the present paper is to assess an innovative integra-tion strategy for the improvement of the energy efficiency of a historic building with public function, by means of thermal monitoring and dynamic thermal-energy calibrated simulation. Energy and economic evaluations are carried out to evaluate the optimal in-tegrated solution by considering both passive and active solutions for energy saving.

2. METHODOLOGY

2.1. RESEARCH LAYOUT

The main steps of the methodology are as follows: i. Continuous indoor thermal monitoring of the case study building;

ii. Elaboration of the energy model; iii. Calibration and validation of the model; iv. Dynamic simulation of the year-round thermal-energy behavior; v. Comparative analysis of four different optimization scenarios;

3

vi. Economic analysis of the considered choices; vii. Choice of the best performing integrated solution.

2.2. Case study modeling The study consisted of the design of an innovative strategy for the integration of a

renewable energy system in the context of a historical building located in the center of Perugia, Italy (Figure 1).

Figure 1a, b – Views of the building in Perugia, Italy

The case study building is situated in the city center and it was built around 1861.

It includes three different areas (Figure 2, Table I).

Figure 2 a, b – Plan and Elevation drawing of the case study building. From (Autocad)

Table I – Building’s global features and location

Building’s global features and location Location: Perugia, Italy 1st room floor Area 119 m2

Latitude: 43°06’28.84’’ NLongitude: 12°23’15.30’’ E 2nd room floor Area 117 m2

Elevation above sea level 464 m 3rd room floor Area 48 m2

After the elaboration of the energy model in Design Builder- Energy Plus envi-ronment (Figure 3) by taking into account real observed features of the building, the cal-ibration process is carried out by iterative comparison between collected experimental data and numerical outputs.



4

Figure 3 – Energy model of the case study building in Design builder. From (Design Builder)

The indoor data are collected by a dedicated temperature probe located inside

Room 2. This probe collects data every 10 minutes and it is connected to a data-logger station and then to a web-based platform where it is possible to download all the data before the post-process. A weather station located at few kilometer distance by the build-ing is also used for this work. Experimentally measured weather data are used to elabo-rate the weather file of the specific location, finally used for running and calibrating the model during the thermal monitoring of the room.

2.3. Elaboration of the optimization scenarios In a context of re-development and sustainable renovation of the historic center of

the city of Perugia, the Municipality Government has identified strategies consistently with the Energy Plan of the City. Among these strategies, there is the recovery of histor-ical spaces and adaptation intervention in the field of energy efficiency, renewable ener-gy production and integration of the energy sources. At present time the building looks like three volumes, with maximum height of 15 m. The air conditioning of a so big sized volume is certainly challenging from the energy efficiency and environmental sustaina-bility point of view. The predicted discontinuous building use, 4 hours per day during the week for training courses of municipal personnel and 2 afternoons in the weekends (from 12:00 pm to 8:00 pm) for seminars and other cultural events, makes the issue even more difficult to address.

In the present work four different scenarios are proposed and discussed, assuming different HVAC systems, for which a technical, economic and environmental analysis is carried out, based on the performance of air conditioners, the operative costs and the greenhouse gases emission level of each technology.

The four evaluated optimization scenarios are listed below: I. refurbishment of the building and application of a traditional natural gas

boiler for heating equipped with an absorption chiller for cooling; II. refurbishment of the building with the application of a geothermal heat

pump integrated to energy micropiles for heating and cooling;

5

III. refurbishment of the building with a clear glass false ceiling in order to re-duce the air-conditioned volume, and application of the same geothermal heat pump of scenario (ii), properly sized on the new reduced volume.

IV. refurbishment of the building through the reduction of the conditioned vol-ume with a transparent false ceiling as in scenario (iii) and application of a natural gas boiler for heating equipped with an absorption chiller for cool-ing, i.e. same technologies of scenario (i), properly dimensioned.

3. CASE STUDY

As previously mentioned, the case study building is a historic building with public function and three main rooms.

More in details, “room 1” and “room 2” have a floor area of about 119 m2 each, 11.5 m and 13 m height, respectively. As regarding “room 3”, the floor area is around 48 m2 and the height is about 15 m. These three rooms are surrounded by another room where a huge water tank is located. The building is meant to be an auditorium, and the occupancy is modeled by considering the occupancy schedule of 4 hours/day and 8 hours/day during the evening for working days and for the week-end, respectively, by taking into account activities such as training courses, conferences, in addition to the equipment rooms and the service area.

3.1. Characteristics of the building The main envelope features have been assumed by qualitatively analyzing the pe-

riod of construction and the other historic buildings located in the surrounding area of the city center.

The main features of each wall typology and materials are reported in Table II. While the external walls are more ancient, with middle age origins, and made of tradi-tional limestone and brickwork, the internal partitions appear to be more recent and are composed by: plaster (20 mm), perforated brickwork (80 mm). As regarding the frontal doors, they are all made of painted wood (2,40× 4,00 m). The windows are characterized by a 4 mm single glass panel with non-insulated wood frame.



6

Table II – Building’s construction properties and layers materials Construction properties Layers Thickness

External wall type 1

Thermal Transmittance: 0.754 W/m2K Internal Heat Capacity: 84.764 kJ/m2K

1.Limestone 750 mm 2.Brickwork [250*120*50] 250 mm 3.Brickwork [250*120*50] 250 mm

4.Limestone 750 mm External wall

type 2


1.Limestone 350 mm 2.Brickwork [280*140*60] 280 mm

3.Limestone 350 mm

Internal wall type 1 (arches)

Thermal Transmittance: 3.4 W/m2K Internal Heat Capacity: 68 kJ/m2K

1.Cement plaster 20 mm 2.Perforated brickwork

[250*80*250] 80 mm

Internal wall type 2 (tank side)


1.Brickwork [250*120*50] 375 mm

Roof

Thermal Transmittance: 0.087W/m2K Internal Heat Capacity: 82.746 kJ/m2K

1.Asphalt 300 mm 2.Polystyrene foam molded shits 50 mm

3.Concrete 500 mm 4.Polyurethane sheets 300 mm

5.Cement mortar 30 mm 6.Brick blocks for slabs

[495*240*250] 300 mm

Ground-floor slab


1.Cement mortar 40 mm 2.Brick blocks for slabs

[495*160*250] 180 mm

3.2. Modeling and calibration procedure After the analysis of the main architectural and technical features of the case study

building, the creation of the energy model within the Design Builder– Energy Plus simu-lation tool is carried out. All the materials and envelope characteristics of the historic building have been taken into account through the modeling procedure, in order to define a reliable model to be used for the dynamic simulation of the energy performance. The main construction materials are limestone and brickwork. All the walls, especially the external ones, have a great thickness, except for the internal partitions which appear to be more recent. After the definition of the layout of the building, different thermal zones are created, with reference to all the various activities which will take place inside the building, e.g. auditorium, back stage, foyer, restrooms and technical rooms. Each ther-mal zone is therefore characterized by different occupancy schedules and systems set up. In particular, building infiltration value is 0.5 vol/h, from 5:00 pm to 9:00 pm from Monday to Friday, and from 12:00 to 20:00 pm during the weekends.

After the elaboration of the energy model, the calibration procedure is carried out. The purpose is to reduce the gap between the simulated values and the experimental data measured by using a dedicated indoor temperature probe located inside the central room (“room 2”) of the building. The iterative process is performed by calculating each time two main parameters, i.e. the MBE (1) and the RMSE (2) (Soebarto, 1997), in order to

7

measure whether or not the model is representative of the real thermal behavior of the case study building.

The parameters driving the calibration of the energy model are mainly the building infiltration values, in addition to the internal gains of each thermal zone. According to ASHRAE Guidelines (Haberl et al.,2002), the procedure is considered over as far as the calibration indexes reach sufficiently low values. More in detail, the calibration process included a set of about 20 dynamic simulations of the case study building, by iteratively modifying time to time the different mentioned parameters and by verifying each time the calibration indexes’ values. The first model of the building, before the calibration, precisely reported all the characteristics of the three main rooms. After the analysis of the first output during the monitored period, many modifications were necessary in order to reach suitable values of the driving parameters, i.e. RME and RMSE (Pernetti et al., 2013, Pisello et al., 2013, Pisello et al., 2013). In fact, the monitored air temperature showed that the indoor environment was just quite a little affected by daily temperature and sun radiation fluctuation. The thermal capacity of the almost 1 m thickness walls, the low solar gain due to the dense urban geometry of the city center and to the presence of trees in the front of the building, guided the iterative calibration procedure. In fact, the first model reported both RME and CV(RMSE) higher than 4, with larger discrepancies during the central hours of the day, when the model predicted an air temperature increase due to solar gains and outdoor overheating, that the real building did not register. There-fore, the second model was elaborated by iteratively enlarging the external wall’s thick-ness of about 0.3-0.4 m, in order to take into account of further thermal capacity of the overall structure of the walls. A third model was then elaborated, starting from model 2, by modifying the natural infiltration of model 3 from 0.5 vol/h to 0.7 vol/h. This was motivated by the important protection of the surrounding buildings and trees facing the only two windows of the monitored room. The final model was elaborated by heavily increasing the indoor thermal gains due to occupancy. This choice was motivated by the fact that the building occupancy during the monitored period was very low in terms of time schedule and activities. In fact, neither the presence of occupants nor the internal contributions due to the presence of some kind of equipment, e.g. television and comput-ers, had been taken into account. This last model presented a RME of -1.2°C, and a CV(RMSE) of 1.5°C, calculated on 10-minute time step.

3.3. Optimization scenarios Four possible scenarios for HVAC have been investigated, by considering two

main technologies: (i) methane boiler coupled with absorption chiller and (ii) geothermal heat pumps. The choice of these technologies is the result of policies’ analysis of the city of Perugia in historical areas. The regulation prohibits the installation of external electric machines/accessories emitting heat and noise in order to preserve the historical and ar-chitectural beauty of the building facades. Therefore, an air heat pump provided with the external machines is not allowed in the site, besides the presence of chimneys or pipes passing along the wall. In this view, and in the perspective of cost and environmental savings allowed by renewable energy, low enthalpy geothermal machines have been chosen as HVAC technology, coupled with a refurbishment of the building in order to increase the energy efficiency.



8

4. ANALYSIS OF RESULTS

4.1. Primary energy for heating The annual analysis of the building energy performance in terms of primary energy

for heating shows higher consumptions in the 2nd scenario compared to all the other sce-narios, as shown in Figure 4:

Figure 4 – Comparison between the primary energy for heating’s annual profiles of the four assessed scenario The geothermal heat pump (2nd scenario) leads to higher values of the heating re-

quirements compared to the application of a traditional methane boiler (1st scenario). Moreover, the heating consumptions of the 3rd scenario, where the volume to be heated is reduced, are always lower during the course of the year if compared to the 2st scenario. Therefore, the installation of a traditional methane boiler coupled with the reduction of the building volume (4th scenario) leads to the lowest primary energy requirements for heating.

The analysis of the daily profiles of the primary energy requirements for heating of each scenario, with refer to some significant days of the year, shows results consistent with the annual assessment (Figure 5).

Figure 5 a,b – Primary energy for heating daily profiles of the four assessed scenarios

9

4.2. Primary energy for cooling The annual analysis of the building’s energy performance in terms of primary en-

ergy for cooling shows higher consumptions in the 1st scenario, followed by the 4th, the 2nd and the 3rd scenarios respectively, as shown by the graph in Figure 6.

Figure 6 – Comparison between the primary energy for cooling’s annual profiles of the four assessed scenario

The daily analysis of the primary energy requirement for cooling in specific days

of the year shows a substantial consistency with the annual findings. More in details, Figure 7 shows that the 3rd scenario has still lower cooling consumptions than the other scenarios.

Figure 7a,b – Comparison between the primary energy for cooling’s daily profiles of the four assessed scenar-io for July 27th and August 25th, respectively

4.3. HVAC plant assessment This section concerns the technical characterization of the selected technologies for

HVAC plants. All these technologies have been sized with regard to the results of the calibrated dynamic simulation, providing the thermal power required in summer and in winter for the case study building.

Scenario 1: methane boiler and absorption chiller. The air conditioning of the entire building requires a boiler of considerable size,

with a power of about 110 kW. This parameter is below the threshold of 116.3 kW, which is equivalent to 100,000 kcal/h which represents, from a local regulation point of view, the threshold for the permissions. Thermal plants with power above this value are



10

subject to the fire safety authorization process (Fire Prevention Certificate) released by the Fire Department, including construction and positioning restraints and operation monitoring of the system. According to the local permissions, the installation of a chim-ney and a piping system to eject combustion fumes from methane is prohibited on the facade. Therefore, it is possible to pierce a bypass only through the roof for the passage of a pipe above the building, and to extend the height of the pipe as prescribed by law. The heating system fueled by methane works not only for heating in winter but also in summer through an absorption refrigeration chiller. This is a machine providing up to 70.88 kW in refrigeration, sufficient for the needs of the building in summer. A specific designed area of the building must be destined to the machinery recovery. It is estimated that a surface of about 10 m2 is required to contain the machines, the manifolds and a 100 liter buffer tank. A dedicated zone is designed in the renovation project.

Scenario 2: geothermal heat pump integrated with energy micropiles. The second scenario is characterized by a geothermal heat pump, different from the

traditional heat pump air/water for the lack of the external machine. The use of geother-mal is also justified by structural considerations: the static analysis of the building and the consolidation project show the need of 50 micropiles 20 m width, along the facade and the bearing walls. This intervention has the purpose to preserve the back side XVI century wall which has a great historic value. In this view, it is reasonable to integrate the micropiles with geothermal pipes, by coupling structural need with energy efficiency targets. The hill where the city is located is characterized by unstable deposits over an aquifer which in the past has been the source of water sampling. The depletion of the aq-uifer, in addition to the excavations in the valley, have produced slope instability and hence the formation of landslides. The installed power corresponds to two reversible machines with a thermal power of 53 kW/each (106 kW in total) and of 45 kW/each for summer conditioning (90 kW in total). The geothermal pipes are calculated by consider-ing a COP of 4.1, and an average thermal exchange with the ground source of 60 W/m. The power to be requested to the ground is evaluated in function of the COP of the ma-chine and of the ground heat exchange yield. The thermal exchange is considered to be 60 W/m and it is evaluated from a geological analysis of ground. Below the floor level there are layers of sand mixed with lenses of clay, fully saturated by water as the plane of aquifer is a few meters below the floor (Figure 8). The total length of the geothermal pipes to be integrated with micropiles is 1.3 km. This distance, even with the distribution of 50 piles, is too long to be applied. For this reason, another more realistic scenario has been provided, i.e. “Scenario 3”.

11

Figure 8 – Regional geologic map: the area of Perugia. From (telematics Umbria’s regional map)

Scenario 3: reduced building volume with geothermal heat pump and energy mi-cropiles. This configuration consists of the use of a geothermal heat pump with a reduced

required power due to the reduction of the volume of the building to be conditioned with a clear glass false ceiling permitting to admire the barrel vault of the old building. The real power is provided by the half of the machines considered in the previous scenario, i.e. 2nd scenario. In fact, the needs are covered by a machine with 53 kW for heating and 45 kW for air conditioning. The geothermal exchangers are therefore reduced, as the thermal piping integrated to the micropiles, which are of about 670 m long. Therefore, 34 micropiles should be integrated, with a mutual distance of 5 m from to avoid any in-terferences.

Scenario 4: reduced building volume with methane boiler and absorption chiller. The last configurations consists of a traditional natural gas boiler for heating

equipped with an absorption chiller for cooling able to serve a reduced building volume realized with a glass false ceiling as in the 3rd scenario. Therefore, the air conditioning of the reduced building volume requires a boiler of a smaller size if compared to the 1st scenario. Thermal power of the methane boiler is about 65 kW and it feeds an absorption chiller 45 kW powered in summertime.

4.4. Economic and environmental analysis The economic analysis has been developed by considering only the costs for the

installation of the machines for energy production. The analysis does not take into ac-count the installation cost of the buffer tanks and the distribution system of hot and cold water to the terminals as in the perspective of a comparative analysis there are not signif-icant technical and economic differences between the four scenarios. It should be speci-fied that in the 3rd and 4th scenarios a false glass ceiling is included, which allows both to admire the brick made dome and the reduction of the volume to be conditioned. There-fore, to better compare the scenarios assessed, the construction of the frame is included into the costs of investment. By referring to the 3rd and 4th scenarios, which result the most interesting from an economic and environmental point of view, the cost of invest-



12

ment for the geothermal heat pump system are approximately equal to four times the cost of the system with methane boiler and absorption chiller.

As regarding the cost of operating the machines, the cost occurring to the owner of the building has been considered equal to 0.85 €/m3 and 0.22 €/kWh for natural gas and for electricity, respectively.

As regarding the environmental analysis, the duration time of operation of the plant has been defined. According to the energy demand, carbon dioxide emissions are pro-duced directly by the methane combustion and by the electricity consumption for the power supply of the heat pumps. The analysis of the carbon dioxide emissions has there-fore been linked only to the emissions generated by the daily use of the machines rather than to their life cycle. In the 1st and 4th cases, the assessment of the emissions is carried out by knowing that for every cubic meter of methane consumed, 2 kg of CO2 are pro-duced. Globally, 20 tons and 12 tons of carbon dioxide are released to the atmosphere during a year, in the 1st and 4th scenarios, respectively. Therefore, considering the re-duced volume of indoor spaces, the carbon emissions generated by the methane boiler in the 4th scenario are double than the emission generated by using geothermal heat-pumps (3rd scenario). In the case of the geothermal heat pumps powered by electricity, it should be noted that an integrated system with photovoltaic, which would allow to use renewa-ble electricity, it is forbidden by the regulations of the city plan. Therefore, the electricity used is produced by conventional thermal power plants which emits about 0.5 kg of CO2/kWh of electricity produced. The heat pump emits about 11 t/year of carbon in the case of full volume.

4.5. Comparative analysis of the solutions The graph in Figure 9 shows the trends of the total investment and operative costs

of the HVAC system. The 3rd scenario gets an extra cost at the beginning, but it results finally convenient if compared to the 2nd and 1st scenarios. In particular, the incidence of the reduction of the number of geothermal boreholes is negligible, but the operating cost is considerably lower and it allows the overcoming of the total costs of the 2nd scenario, already since the third year. The 4th scenario is the most convenient due to the lower in-vestment costs. Moreover, its operating costs are higher with respect to the 3rd scenario, and this is attributable to water and methane consumption.

13

Figure 9 – Comparison between the four assessed scenarios in terms of investments and operative costs

CONCLUSIONS

A cost-benefit analysis of an innovative energy retrofit combined solution in a his-toric building is carried out in this paper. An historic building located in Perugia, Italy, represents the case study of the research. The actual condition is continuously monitored in terms of indoor air temperature to allow the calibration of the dynamic simulation model of the building. Four scenarios are compared, where traditional technologies and innovative renewable ones are assessed, when integrated with passive solutions. As con-cerning the primary energy requirement for heating, the final solution of methane boiler and absorption chiller with a reduced building volume is showed to be the most perform-ing (4th scenario) from an investment and energy efficiency point of view. Moreover, the scenario with the geothermal plant coupled with the reduction of the conditioned volume resulted to be the most efficient and sustainable in terms of primary energy requirement for cooling (3rd scenario). The proposed solutions could represent an interesting prelimi-nary guideline for those historic buildings which presents huge architectural constraints.

REFERENCES

Albino V., Berardi U. 2012. Green buildings and organizational changes in Italian case studies. Business Strategy and the Environment.

Ascione F., De Rossi F., Vanoli G.P. 2011. Energy retrofit of historical buildings: theoretical and experimental investigations for the modeling of reliable performance scenarios. Energy and Buildings, 43, 1925-1936.

Chwieduk D. 2003. Towards sustainable-energy buildings. Applied Energy, 76, 211-217.

Dincer I. 2000. Renewable energy and sustainable development: a crucial review. Renewable and Sustainable Energy Reviews, 4, 157-175.

Fabbri K. 2013. Energy incidence of historic building: Leaving no stone unturned. Journal of Cultural Heritage, 14, 25-27.



14

Haberl J. F., Culp C., Claridge D.E. 2002. Ashrae’s Guidelines 14-2002 for meas-urement of energy and demand savings: how to determine what was really saved by the retrofit.

John G., Clements Croome D., Geronimidis G. 2005. Sustainable building solu-tions: a review of lessons from the natural world. Building and Environment, 40, 319-328.

Lang S. 2004. Progress in energy efficiency standards for residential buildings in China. Energy and Buildings, 36, 1191-1196.

Norrstrom H. 2013.Sustainable and balanced energy efficiency and preservation in our built heritage. Sustainability, 5, 2623-2643.

Omer A.M. 2008. Energy, environment and sustainable development. Renewable and Sustainable Energy Review,12, 2265-2300.

Perez-Lombard L., Ortiz J., Pout C. 2008. A review on buildings energy consump-tion information. Energy and Buildings, 40, 394-398.

Pernetti R., Prada A., Biggio P. 2013.On the influence of several parameters in en-ergy model calibration: the case of a historical building. IBPSA Italy.

Pisello A.L., Bobker M. , Cotana F. 2012. A Building Energy Efficiency Optimiza-tion Method by Evaluating the Effective Thermal Zones Occupancy. Energies, 5, 5257-5278.

Pisello A.L., Cotana F., Nicolini A., Brinchi L. 2013. Development of Clay Tile Coatings for Steep-Sloped Cool Roofs. Energies, 6, 3637-3653.

Pisello A.L., Cotana F., Brinchi L. 2013. On a cool coating for roof clay tiles: de-velopment of the prototype and thermal-energy assessment. Energy procedia, in press.

Pisello A.L., Taylor J.H., Cotana F. 2013. Simulation the effect of urban morphol-ogy on indoor thermal behavior: an Italian case study. Winter Simulation Conference.

Rezaie B., Esmailzadeh E., Dincer I. 2011. Renewable energy options for build-ings: Case studies. Energy and Buildings, 43, 56-65.

Soebarto V.I. 1997. Calibration of hourly energy simulation using hourly moni-tored data and monthly utility record for two case study buildings. Proc. Building Simu-lation 1997,2, 4121-419.

15