energies

Article Towards Zero Energy Stadiums: The Case Study of the Dacia Arena in Udine, Italy

Mattia Manni 1 , Valentina Coccia 1,2, Andrea Nicolini 1,2 , Guido Marseglia 3 and Alessandro Petrozzi 1,*

1 CIRIAF—Interuniversity Research Centre on Pollution and Environment “Mauro Felli”, 06125 Perugia, Italy; [email protected] (M.M.); [email protected] (V.C.); [email protected] (A.N.) 2 Department of Engineering, University of Perugia, 06125 Perugia, Italy 3 Research Department, Link Campus University of Rome, 00165 Rome, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-075-585-3806



Received: 13 July 2018; Accepted: 4 September 2018; Published: 11 September 2018


Abstract: The environmental impacts of sport events have been growing during the last decades, which has led to the organizing associations developing adequate countermeasures to both reduce carbon emissions due to construction and operational stages compensate for the emissions. This work aims at proposing an approach to stadiums energy enhancement that includes strategies largely recognized as effective and applicable to several building typologies (residential, commercial, academic, etc.). The selected case study is the Dacia Arena in northern Italy that has been recently refurbished and renovated. The proposed workflow has as a goal minimizing the increment of the operational emissions, caused by new heated areas in the stadium. Firstly, the energy consumption was estimated in dynamic state for Scenario 0 (current state) and Scenario 1 (refurbished state) to quantify the new plant’s energy demand. Secondly, two hypothetical system layouts were proposed and evaluated. In the first, the power for lighting, cooling and heating is supplied by a system that couples photovoltaic panels with heat pump. In the second, the same photovoltaic plant is integrated with a biomass plant and an absorption chiller. The comparison highlights the suitability of those interventions and the environmental advantages deriving from their exploitation.

Keywords: zero energy buildings; compensation strategies; low carbon architecture; renewable energy systems

1. Introduction The buildings’ environmental impact on global energy demand and carbon emissions released in atmosphere have been constantly monitored during the last decades due to their significant increment. Over 40% of global energy consumption and about 18% of greenhouse gas (GHG) emissions are related to the building sector [1]. The current regulations concerning the reduction of building’s energy consumption focuses mainly on the operational phase [2–4]. The European Directive 28/2009 defines the strategic goals which should be achieved by 2020 [5]: (i) an increment by 20% of the energy derived from renewable energy sources (RES) on operational energy consumption; (ii) a reduction by 20% of the GHG emissions during the operational stage compared to the values in the 1990s; and (iii) an increment by 20% in terms of buildings’ energy efficiency. Furthermore, the declaration of intents stated that GHG emissions’ reduction should reach 30% by 2030 and a 50% by 2050, although the first percentage was revised up by 10% by a Communication of the European Commission on 2014 [6]. The World Green Building Council 2017 Report states that every building has to be carbon neutral by 2050 to maintain the global temperature variation within a range of 2.0 ◦C[7]. The document

Energies 2018, 11, 2396; doi:10.3390/en11092396 www.mdpi.com/journal/energies Energies 2018, 11, 2396 2 of 16 confirmed part of the declaration of intents signed at the end of the 21st Conference of the Parties, in Paris on 2016 [8]. Among all building typologies, stadiums are the ones which have achieved the highest increment of environmental impact: sports arenas have been getting continuously larger and complementary functions have been added to sport practicing (museums, stores, restaurants, and concerts). Furthermore, the most famous sport events, such as Olympic Games, FIFA World Championship or Super Bowl, attract more and more people every time, making necessary larger spaces to permit hosting more spectators. According to the data presented by Smulders and Imtech Building Service about European sports infrastructures, more than 4000 stadiums exploit up to 40 TWh/year, which are mainly generated from conventional fossil fuels [9]. A modern medium-sized stadium (55,000 spectators) reaches an energy use of 10,000 MWh/year which equals 3600 tCO2/year [10,11]. During the principal sports events, the arena’s energy consumption could achieve a level comparable to an African country: the 80,000-seat arena hosting the Super Bowl consumes up to 10 MW per hour of energy during the peak, which equals to 50 MW over the course of the game itself [12]. Liberia, a 43,000 square-mile country with four million people, has the capacity to pump less than a third of such a power into its national grid [13]. The increment of the arenas’ energy demand is also due to extended opening hours of the facilities. Indeed, contemporary stadiums do not open only on match day, but also host museums dedicated to the home-team and its history; sports stores, which promote the home-team’s brand; restaurants; supermarkets; and playgrounds for the youngest supporters. Those activities guarantee an important cash flow that is fundamental for the economic management. As long as the economics are concerned, the Italian government promoted a decree regarding sports infrastructure development and recognized compensation strategies [14]. Hence, it is possible to counterbalance the increased energy requirements due to extra opening hours by installing on-site power plants for energy production from renewable sources. Furthermore, the produced energy that is not directly used can be inputted to the grid and delivered to the neighborhood. This research investigated the state of the arts regarding technologies which can be applicable to sports infrastructures to both reduce GHG emissions and produce renewable energy on-site. How the extra functions, which are nowadays hosted in modern sports infrastructures, affect the building energy demand was evaluated. Finally, a cluster of actions was proposed for the architectural restoration and energy refurbishment of the Dacia Arena in Udine (Italy). The case study was also modeled with specific software for energy dynamic simulations to evaluate the different scenarios.

1.1. Stadiums and Sustainability: From Timber Recyclable Structure to Qatar 2022

Although most available technologies to restrain energy use and CO2 emissions are not specifically developed for stadiums, they can have a much higher impact if implemented in sports arenas. Constructing stadiums energetically autonomous, or even able to generate extra-energy exploited by the surroundings, represents a fundamental step towards zero-emission arenas. The suitability of eco-friendly materials such as partially-recycled concrete or glued laminated timber, has been successfully tested in stadiums recently. A joint proposal [15] couples the advantages due to glulam exploitation with the modular design of small- and medium-sized stadiums (5000–20,000 spectators). This includes up to the 80% of arenas. Thus, their energy refurbishment could have a larger impact. Such a green facility can be integrated with wind plants, photovoltaic systems and high-efficiency LED lighting devices. Furthermore, the modularity of its components allows rapidly upgrading the building and increasing its capacity without demolishing and rebuilding process. The whole stadium can also be easily disassembled and reassembled in a different area, reducing the carbon emissions from waste disposal. Famous sports events, e.g., FIFA World Championship, usually encourage sustainable technological progress by incrementing each time the energy performance levels required to infrastructures. The 2022 FIFA World Championship, which will happen in Qatar, is challenging Energies 2018, 11, 2396 3 of 16 because of the hot climate-related issues faced by designers and planners. The Qatar Football Association (QFA) has to guarantee an adequate thermal comfort to both players and spectators by developing low carbon cooling systems, thereby lowering the ecological footprint. FIFA requires at least an air temperature equal to 25 ◦C in all the hospitality areas of the stadium, compared to the 46 ◦C ambient reached during the local summer season. The research carried out by Sofotasiou [16] presents a preliminary state of the art regarding the potential cooling strategies that can be applied to sports arenas. Furthermore, it estimates the cooling load for semi-outdoor stadiums in Qatar. The results underline how an oculus roof combined with a peripheral continuous opening could increase local ventilation rates. The proposal can even be integrated with an evaporative cooling technique from Middle Eastern countries (badger wind tower) [17]. The wind tower takes advantage of the Venturi effect [18] to create an air route over a wetted surface (in this case, the football pitch) to deliver cool air. Differently, adequate comfort conditions could be guaranteed by applying active systems powered by renewable energy sources (e.g., photovoltaic plant, solar panels, etc.). Solar panels (SP) seem to be more efficient than photovoltaic (PV) plants in hot-humid climates, as demonstrated by the study conducted by Aly [19]. The main advantage of using SP instead of PV is due to their efficiency. Indeed, for every degree Celsius above 25 ◦C of outdoor temperature, PV’s performance turns out to be reduced by 0.25–0.45% [20]. This tendency cannot be omitted in a hot climate country such as Qatar, where temperatures reach an average value equal to 33.4 ◦C. The proposal by Arup Associates considers installing solar thermal collectors, which warm up the heat transfer fluid up to 200 ◦C. Then, its thermal energy is exploited in cooling cycle including absorption chiller and cooling desiccants [21]. It permits delivering air at 23 ◦C even when outdoor temperatures reach 44 ◦C. Nevertheless, there are still few uncertainties regarding this proposal since it needs at least four days to reach the comfort zone, even though it is a 500-seat arena. Furthermore, the cooling process tends to be worsened when strong wind patterns prevail, as demonstrated by computational fluid dynamic (CFD) simulations [22,23]. The FIFA directives about carbon emissions allow hosting countries to offset GHG emissions by promoting practices aiming at prevent them (i.e., compensation strategies). Those strategies were included on a specific master plan, “Green Qatar 2022”. The guidelines state that carbon neutral target of the event could be achieved by: (i) nulling the dependency from hydrocarbon resources; (ii) installing solar panels either integrated or located in buildings’ proximity; (iii) using balancing strategies to compensate the energy demand during the event with surplus electricity exported to the national grid; and (iv) exploiting the recovered heat on water distillation process [24–26].

1.2. FIFA World Championship, Towards Russia 2018 The FWC is the largest single-event sporting competition in the world [27] having significant effects on society, economy and environment of the host country, which leads the association to activate the “Football for the Planet” program that aims at mitigate negative environmental impacts by increasing event sustainability. The first step towards this greener policy was registered during the 2006 Germany FWC: it was the first tournament in which measurable environmental targets were set and monitored [27,28]. The most important strategies that have been applied since 2006 aim at offset the carbon footprint of both FWC (FIFA World Championship) events and FIFA (considered as organization) [29]. The main ones regard the realization of plants to generate electricity from sewage gas in South Africa (2006) to offset 92,000 tCO2; the installation of solar panels in 20 Football for Hope Centers across Africa (2010); and the reforestation project in Columbian Andes that permits to offset 9000 tons of GHG emissions by planting 35,000 trees (2011). Furthermore, from January 2012, FIFA has offset all its flight emissions (75% of its total emissions) through compensation projects in all FIFA zones. A different approach was followed during the 2010 South Africa FWC, when the committee had great difficulties on realizing offsetting projects. Hence, they preferred to organize a low-carbon event [30]. Besides these actions, FIFA promoted the calculation and analysis of its annual carbon Energies 2018, 11, 2396 4 of 16

footprint: the first comprehensive assessment in 2009 estimated it equals 48,500 tCO2-eq per year [31]. A second evaluation limited to a single event (2010 South Africa FWC) states that total carbon emissions are 41,405 tCO2-eq. However, the calculation does not include the emissions due to transport of ticket holders as well as official venues, which significantly impact the result, as demonstrated in the 2014 Brazil FWC report. In that case, the carbon footprint reached 2,723,756 tCO by including these Energies 2018, 11, x FOR PEER REVIEW 2-eq 4 of 17 parameters (ticket holders transportation and official venues). To reduce this environmental impact, FIFAdemonstrated and Local Organizing in the 2014 Committee Brazil FWC (LOC)report. are In that implementing: case, the carbon (i) GHG footprint emissions reached compensation 2,723,756 strategies;tCO2-eq (ii) by greenincluding stadiums these parameters design; and (ticket (iii) wasteholders management transportation in and sports official arenas. venues). To reduce Thethis environmental impact, goals included FIFA and by Local FIFA Organizing and Brazilian Committee LOC in (LOC) the agreements are implementing: were achieved (i) throughGHG the emissions design compensation of sustainable strategies; venues, (ii) alonggreen stadiums with the design; definition and (iii) of waste compensation management strategies in sports arenas. described on the previous paragraph. Concerns from FIFA and complaints from critics were shown The environmental goals included by FIFA and Brazilian LOC in the agreements were achieved regarding the economic sustainability and the unnecessary waste of money to build an excessive through the design of sustainable venues, along with the definition of compensation strategies numberdescribed of arenas. on the Indeed, previous the paragraph. LOC insisted Concerns they wantedfrom FIFA 12 and host complaints cities (12 newfrom venues),critics were whereas shown FIFA usuallyregarding requires the not economic more than sustainability eight [32]. and However, the unnecessary this paragraph waste of ostensible money to focuses build an on excessive systems and plantsnumber installed of arenas. in stadiums Indeed, to the improve LOC insisted their energy they wanted performances. 12 host cities Further (12 informationnew venues), regardingwhereas the use ofFIFA funds usually from requiresFWC’s organization not more than can eight be found [32]. However, in [32,33 ]. this paragraph ostensible focuses on Amongsystems and the plants Brazilian installed stadiums, in stadiums Estádio to improve Castelã theiro was energy the first performances. to be awarded Further the information Leadership in Energyregarding and Environmental the use of funds Design from FWC’s (LEED) organization certification can [be34 found], whereas in [32,33]. Está dio do Maracanã, Estádio MineirãoAmong and Arena the Brazilian Pernambuco stadiums, installed Estádio plants Castelão to exploit was the RES first and to be minimize awarded theirthe Leadership energy demand. in Energy and Environmental Design (LEED) certification [34], whereas Estádio do Maracanã, Estádio The Maracanã (78,000 seats) is equipped with a Building-integrated Photovoltaic (BiPV) system that is Mineirão and Arena Pernambuco installed plants to exploit RES and minimize their energy demand. composed of 1500 PV cells placed on the roof. The plant allows reducing emissions by 2600 tCO The Maracanã (78,000 seats) is equipped with a Building-integrated Photovoltaic (BiPV) system that 2-eq by powering 390 kW , which meets the energy demand of 240 single-family houses (when it is not is composed of 1500p PV cells placed on the roof. The plant allows reducing emissions by 2600 tCO2-eq match-day)by powering [35]. 390 Larger kWp plants, which weremeetsinstalled the energy on demand two other of 240 stadiums single-family in Belo houses Horizonte (when it and is not Recife, whichmatch can- reachday) [35]. peak Larger powers plants of were 1.5 MW instalp andled on 1 MWtwo otherp, respectively stadiums in [36 Belo,37 ].Horizonte Furthermore, and Recife, the LOC decidedwhich to evaluatecan reach alternative peak powers and of less 1.5 commonMWp and solutions.1 MWp, respectively Specially developed[36,37]. Furthermore, tiles were the placed LOC under the turfdecided (56 mm) to evaluate to convert alternative the kinetic and less energy common of players’ solutions. movements Specially developed into electricity. tiles were The technologyplaced had alreadyunder the been turf tested (56 mm) in train to convert stations the in Europekinetic energy [38], shopping of players’ centers movements in Australia into electricity. [39] and Terminal The 3 of London’stechnology Heathrow had already Airport been tested [40]. in Indeed, train stations the average in Europe footstep [38], shopping generates centers five watts in Australia per second. [39] and Terminal 3 of London’s Heathrow Airport [40]. Indeed, the average footstep generates five The system is coupled with PV panels providing the necessary lighting to the pitch [41]. watts per second. The system is coupled with PV panels providing the necessary lighting to the pitch 1.3. European[41]. Football Championship 2016 The1.3. European Union ofFootball European Championship Football 2016 Associations (UEFA) demonstrated to take particular care of environmentThe Union related of issuesEuropean during Football the Associations continental (UEFA) championship. demonstrated During to take the particu last Europeanlar care of Cup in France,environment innovative related and issues sustainable during the arenas continental were championship. constructed inDuring Lyon, the Lille, last European Bordeaux Cup and in Nice (FigureFrance,1)[42 innovative]. The planners and sustainable achieved the arenas reduction were constructed of the stadiums’ in Lyon, impact Lille, by Bordeaux increasing and the Nice events which(Figure could 1) be [42]. hosted The planners in addition achieved to the the footballreduction championship. of the stadiums’ impact The Pierre-Mauroy by increasing the Stadium events and the Allianzwhich could Riviera, be hosted in Lille in addition and in Nice, to the respectively, football championship. can be turned The Pierre into-Mauroy amphitheaters Stadium forand concertsthe and similarAllianz Riviera, events in to Lille improve and in the Nice, economical respectively, sustainability can be turned ofinto the amphitheaters arenas. Furthermore, for concerts and the new similar events to improve the economical sustainability of the arenas. Furthermore, the new constructed stadiums are well integrated on the landscape, and they are provided with systems constructed stadiums are well integrated on the landscape, and they are provided with systems powered by RES such as PV plants or geothermal heating systems coupled with natural ventilation powered by RES such as PV plants or geothermal heating systems coupled with natural ventilation (Table(Table1). 1).

FigureFigure 1. Overview 1. Overview of theof the arenas arenas built built for for Euro Euro 20162016 in France. France. From From the the left left to right: to right: Pierre Pierre-Mauroy-Mauroy Stadium (Lille), Allianz-Riviera (Nice), Noveau Stade de Bordeaux (Bordeaux), and Parc Olympique Stadium (Lille), Allianz-Riviera (Nice), Noveau Stade de Bordeaux (Bordeaux), and Parc Olympique Lyonnais (Lyon) [43–46]. Lyonnais (Lyon) [43–46].

Energies 2018, 11, 2396 5 of 16

Energies 2018, 11, x FOR PEER REVIEW 5 of 17 Table 1. UEFA Euro 2016 new arenas’ configuration [47]. Table 1. UEFA Euro 2016 new arenas’ configuration [47].

FeaturesFeatures Lille Lille Nice Nice Bordeaux Bordeaux Lyon Lyon AccessibilityAccessibility ApproximateApproximate UEFA UEFA capacity capacity 50,000 50,000 36,000 36,000 42,000 42,000 58,000 58,000 WheelchairWheelchair spaces spaces 230 120 120120 120246 246 Easy-access seats close to amenities 115 100 100 123 Easy‐access seats close to amenities 115 100 100 123 TransportTransport PublicPublic transport transport accessibility accessibility     EnergyEnergy Renewable energy generation 1in Renewable energy generation in situ SP,SP, Gt SP SPSP SPSP SP Renewable energysitu 1 purchase  Renewable energy purchase Water Water Rainwater collection system     OptimizationRainwater of watercollection consumption system intelligent sprinklers - motion detectors intelligent motion Optimization of water consumption  Waste ‐ sprinklers detectors Selective sorting in non-public areas Waste Selective sourcing in public areas -- Selective sorting in non‐public areas     Waste minimization 2 a, b, c, d a, b, c, d a, b, c, d a, b, c, d Selective sourcing in public areas   ‐ ‐ 1 the renewable energy generation in these case studies, is conducted by installing solar panels (SP) and geothermal 2 powerWaste (Gt); 2 minimizationthe minimization is achieveda, by b, applying c, d the followinga, b, c, d strategies: (a)a, b, reusable c, d cups; (b)a, b, food c, d donation; (c)1 signage the renewable reuse; and energy (d) composting. generation in these case studies, is conducted by installing solar panels (SP) and geothermal power (Gt); 2 the minimization is achieved by applying the following strategies: (a) 1.4. Italianreusable Stadiums cups; (b) food donation; (c) signage reuse; and (d) composting.

1.4.The Italian process Stadiums of renovation and construction of Italian stadiums started recently. Juventus F.C., A.C. ChievoThe process Verona, of renovation Hellas Verona and construction F.C., and Cagliari of Italian Calcio stadiums are thestarted only recently. teams inJuventus the Serie F.C., A which haveA.C. already Chievo enhancedVerona, Hellas their Verona arenas F.C., in Turin,and Cagliari Verona, Calcio and are Cagliari, the only respectively.teams in the Serie Atalanta A which B.C., F.C. Internationalhave already Milan, enhanced A.C. their Milan, arenas and in Turin, A.S. Rome Verona, have and startedCagliari, the respectively. same procedure Atalanta to B.C., improve F.C. their stadiumsInternational (Table Milan,2). A.C. Milan, and A.S. Rome have started the same procedure to improve their stadiumsThe Bentegodi (Table 2). Arena in Verona is the first Italian stadium to be partially covered. The 42,000-seat arena isThe provided Bentegodi a PV Arena plant in integrated Verona is on the the first roof Italian that powers stadium up to to 1be MW partially with itscovered. 13,300 The panels [48]. 42,000‐seat arena is provided a PV plant integrated on the roof that powers up to 1 MW with its The PV system allows reduces emissions by 550 tons of CO2 and supplies energy equal to the 13,300 panels [48]. The PV system allows reduces emissions by 550 tons of CO2 and supplies energy consumption of 350 families. The Allianz Stadium in Turin was realized after the old Delle Alpi equal to the consumption of 350 families. The Allianz Stadium in Turin was realized after the old Stadium had been partially demolished. The new arena was built in the same area and some of the Delle Alpi Stadium had been partially demolished. The new arena was built in the same area and materialssome of andthe materials structures and from structures the previous from the building previous (i.e.,building concrete, (i.e., concrete, aluminum, aluminum, steel, andsteel, copper) and was employed,copper) was which employed, achieved which a reduction achieved in termsa reduction of environmental in terms of impactenvironmental and economics, impact and saving up toeconomics, 2.3 million saving of euro. up Furthermore, to 2.3 million the of energyeuro. Furthermore, consumption the is energy partially consumption covered by is integratedpartially solar panelscovered coupled by integrated to PV modules. solar panels The coupled first covers to PV the modules. heating The energy first covers requirements the heating by deliveringenergy hot waterrequirements with a district by delivering network; hot the water latter with powers a district up network; to 100 kW thep latter[49]. powers up to 100 kWp [49].

TableTable 2. List2. List of theof mainthe main stadium stadium plans plans which which have alreadyhave already been discussedbeen discussed by the by local the municipalities local municipalities or which are under discussion at the moment [50,51]. or which are under discussion at the moment [50,51]. Stadium Capacity City Tenant Opening StadioStadium della Roma Capacity52,500 Rome City A.S. Rome Tenant 2020 Opening StadioNew Fiorentina della Roma Stadium 52,50040,430 Florence Rome A.C.F. Fiorentina A.S. Rome ‐ 2020 NewNew Fiorentina Cagliari Stadium Stadium 40,43030,000 Cagliari Florence Cagliari A.C.F. Calcio Fiorentina 2021 - NewNew Cagliari Stadio Stadium Castellani 30,00020,266 Empoli Cagliari Empoli Cagliari F.C. ‐ Calcio 2021 NewAtleti Stadio Azzurri Castellani D’Italia Arena 20,26624,000 Bergamo Empoli Atalanta Empoli B.F.C. F.C.2020 - Atleti Azzurri D’Italia Arena 24,000 Bergamo Atalanta B.F.C. 2020

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2. Materials and Methods

2.1. Dacia Arena in Udine, Italy The case case study study investigated investigated in in this this research research is Dacia is Dacia Arena Arena in Udine in Udine (Italy): (Italy): it is the it 23rd is the stadium 23rd instadium terms ofin capacity terms of in capacity Italy (25,144 in Italy seats). (25,144 The venueseats). wasThe inaugurated venue was inaugurated in 1976 and it in is 1976 characterized and it is bycharac an archedterized roof by over an arched the West roof Gallery—the over the onlyWest covered Gallery part—the of onlythe original covered configuration. part of the Its original shape remainedconfiguration. constant Its shape throughout remained all constant restorations throughout and retrofits all restorations until 2013, and when retrofits the infrastructure until 2013, when was completelythe infrastructure renewed. was The completely enhancement renewed. actions aimedThe enhancement at design a secure, actions modern aimed and at sustainable design a secure, arena thatmodern could and reach sustainable the fourth arena UEFA that certification could reach category. the fourth Among UEFA the structuralcertification and category. energy interventions, Among the itstructural is worth and mentioning: energy interventions, (i) the enhancement it is worth of windowmentioning: frames; (i) the (ii) enhancement the design of of the window snow meltingframes; heating(ii) the designsystem belowof the thesnow playing melting pitch heating that is powered system below by a thermal the playing power pitch station that (TPS) is powered and regulated by a bythermal a secondary power station; station (iii) (TPS) the and installation regulated of an by air a sourcesecondary heat station; pump (ASHP) (iii) the for installation heating and ofcooling an air thesource daily heat used pump areas (ASHP) in the Westfor heating Gallery; and and cooling (iv) the the demolition daily used and areas reconstruction in the West ofGallery; the north, and east(iv) andthe demolition south sectors, and which reconstruction are covered of by the a continuous north, east roof. and Figure south2 sectors,reports the which venue’s are layoutcovered before by a andcontinuous after the roof. last Figure restoration. 2 reports the venue’s layout before and after the last restoration.

Figure 2 2.. Dacia Arena, Udine, before ( left) and after (right) the restoration.

The reduction of the energy consumption as well as operational costs was achieved using a Building Automation system to optimize thethe arena’sarena’s management.management. Furthermore, modern lighting appliancesappliances and motion sensors were installed, decreasing decreasing the the energy energy demand demand for for lighting lighting by by 20%. 20%. Similarly, polycarbonate panels have been placed on the last 11 m of the roof to permit daylight reaching galleries and spectators. The TPS and the ASHP were coupledcoupled to fitfit daily use and match-daymatch-day energy requirements for heating and and cooling. cooling. The The TPS TPS reaches reaches a net a net power power of 1380 of 1380 kW and kW it and powers it powers the indoor the indoor heating heating system andsystem the and domestic the domestic hot water hot (DHW) water that (DHW) is warmed that is to warmed 60–65 ◦C. to A 60 secondary–65 °C. A station secondary regulates station the thermalregulates power the the exploitedrmal power for exploited the snow for melting the snow system melting that issystem placed that 27–30 is placed cm below 27–30 the cm football below pitch.the football The exhausted pitch. The gasesexhausted are finally gases expelledare finally from expelled a cluster from of a grills cluster integrated of grills integrated on the roof on edge. the Theroof technicaledge. The specifications technical specifications for the football for the pitch’s football heating pitch’s system heating are system reported are in reported Table3. in Table 3.

TableTable 3.3. Technical specificationsspecifications of the football pitch’spitch’s heatingheating system.system.

FeaturesFeatures UnitsUnits ValuesValues SpecificSpecific peak peak power power per square per square meter meter [W/m2[W/m] 2] 150150 RequiredRequired peak peak power power [kW][kW] 12001200 Anti-freezeAnti-freeze percentage percentage concentration concentration on thermos on thermos vector fluidvector fluid[%] [%] 34.034.0 3 PumpPump flow flow rates rates [m /h][m3/h] 42–9042–90 Inlet temperature [◦C] 42 OutletInlet temperature temperature [◦C][°C] 28–3042 Set-pointOutlet temperature temperature [◦C][°C] 28 20–30 Set-point temperature [°C] 20 The ASHP was installed to cover the heating and cooling energy demand in the daily lived areas. The ASHP was installed to cover the heating and cooling energy demand in the daily lived areas. They are all located in the West Gallery and they require a heating and a cooling power equal to They are all located in the West Gallery and they require a heating and a cooling power equal to 303.5 kW and 174.4 kW, respectively. The zones served by the ASHP are: (a) the locker rooms; (b) the

Energies 2018, 11, 2396 7 of 16

303.5 kW and 174.4 kW, respectively. The zones served by the ASHP are: (a) the locker rooms; (b) the administrative building, which is actually a separated volume but is connected to the same heating system; (c) the medical center; and (d) the fourth level of the West Gallery hosting a cafeteria and a break room.

2.2. Dynamic Simulation Settings Dynamic simulations were conducted through Design Builder (DB) software, a specific tool that exploits Energy Plus engine to estimate building’s energy demand. First, the thermal loads which characterize the model were estimated. They were grouped into two main categories (outdoor and indoor thermal loads), as described in Table4.

Table 4. Thermal loads considered in the Design Builder model.

Outdoor Thermal Loads Indoor Thermal Loads

Thermal flow through opaque walls Qwall (t) Thermal flow related to people presence Qpers (t) Thermal flow through glazed surfaces Qglaz (t) Thermal flow related to appliances Qappl (t) Thermal flow due to global irradiation Qirr (t) Thermal flow related to lighting system Qlight (t) Thermal flow due to thermal bridges Qbridge (t) Thermal flow due to other contributes Qother (t) Thermal flow due to ventilation Qvent (t)

The analyses permitted estimating the energy demand in summer and winter conditions. They were calculated by considering different equations: the transient regime was applied to summer conditions (Equation (1)), whereas the steady regime was preferred for the winter conditions (Equation (2)).

Q (τ) = Q (τ) + Q (τ) + Q (τ) + Q (τ) + Q (τ)+ summer wall glaz irr bridge vent (1) + Qpers(τ) + Qappl(τ) + Qlight(τ) + Qother(τ)

Qwinter = −Qwall − Qglaz − Qbridge − Qvent (2) The negative terms stand for the thermal outflow, whereas the positives stand for the thermal inflow. The Qwinter calculation does not include all the contributions (Qpers,Qappl,Qlight, and Qother) which can positively affect the heating energy demand. It permits estimating the energy consumption by considering the worst conditions in which the plant could operate. Furthermore, the values included in the calculation in winter conditions do not vary depending on time, but they are included as their maximum (steady regime). Hence, the heating system can be designed without risk of being undersized [52]. Then, the outdoor and indoor environmental conditions were defined. The following outdoor conditions were identified: (i) air temperature’s trend; (ii) relative humidity; (iii) wind velocity; and (iv) solar radiation. The data were suggested from specific Italian regulations such as UNI 10349 [53,54] since it was not possible to collect them using weather stations. The indoor conditions were defined based on the functions which are hosted in the facilities. An air temperature ranging from T = 20 ± 1 ◦C (winter conditions) to T = 26 ± 1 ◦C (summer conditions) should be guaranteed, whereas the relative humidity was set to 50 ± 10% through the whole year. The ventilation is characterized by an inlet air velocity that ranges between 0.05 m/s and 0.40 m/s. Thus, an average value equal to 0.15 m/s was considered. The Air Change per Hour (ACH) value was evaluated considering the user concentration rates as well as room volumes. Tables5 and6 summarize the information about localization that was included in the assessment. The values were obtained from Energy Plus database. Energies 2018, 11, 2396 8 of 16

Table 5. Input data regarding the environment surrounding the Dacia Arena.

Climate Parameters Input Data Location Udine, Argentina Square Latitude 46◦0300000 Longitude 13◦1400000 Altitude 113 m above sea-level Climatic Zone E Degree days 2323 Maximum wind velocity 4 m/s Average yearly relative humidity 72% Average amount of annual precipitation 999.9 mm Average annual maximum temperature 17.0 ◦C Average annual minimum temperature 7.0 ◦C

Table 6. Monthly values of temperature and precipitation about Udine.

Parameters January February March April May June July August September October November December ◦ Tmeant [ C] 3.1 4.5 7.9 12 16.6 20.1 22.3 21.8 18.5 13.6 8.2 4.4 ◦ Tmin [ C] −0.2 0.7 3.4 7.1 11.2 14.8 16.7 16.4 13.4 8.9 4.7 1.1 ◦ Tmax [ C] 6.5 8.4 12.5 17 22 25.4 28 27.2 23.7 18.4 11.8 7.8 Rainfall [mm] 75 76 86 117 107 150 98 120 132 124 138 118

The DB model was integrated with information about the users’ pattern to conduct an accurate simulation in transient regime, in which energy demand varies along with outdoor conditions. The heating system installed on the playing pitch is automatically activated by the managing system every time the temperature drops below the set-point. This value depends on the location and corresponds to the frost point: in this case, it equals 0.5 ◦C, and is achieved around 05:00. The temperature sensors, which activate the system, work only in proximity of practice and match days. In particular, during the two football seasons after their installation, it was observed that the heating system operated 32 (2014–2015 season) and 27 (2015–2016 season) times, respectively. The areas in which the arena is divided are not used with the same frequency and must be considered when energy demand is estimated. They can be grouped into two clusters that are served by two different heating systems. The first group includes all those rooms which are exploited during match days: (a) offices for both UEFA and Lega Seria A functionaries; (b) several restoration areas; (c) VIP zones; (d) conference room; (e) media center; and (f) zones hosting other match days’ services. Adequate indoor comfort conditions are guaranteed by a 1380 kW heater powered by methane. In the second category, the daily used spaces are included: (g) locker rooms; (h) administrative offices; (i) the Energies 2018, 11, x FOR PEER REVIEW 5 of 17 medical center; and (j) the fourth level of the West Gallery where a cafeteria and a break room for players are placed. All those areas are served by the ASHP, which is dailyTable exploited. 1. UEFA Euro 2016 new arenas’ configuration [47]. A summary of the zones and their utilization are reported in Table7 to give a complete overview of the use pattern. Features Lille Nice Bordeaux Lyon Accessibility Table 7. Overview of the zones modeled on DesignApproximate Builder to evaluate UEFA the capacity energy requirements.50,000 36,000 42,000 58,000 Wheelchair spaces 230 120 120 246 System Level Zone Hours perEasy Day‐accessDays seats per close Week to amenities 115 100 100 123 TPS * ASHP **Transport Wellness area 2Public transport 6 accessibility -     Locker rooms 4 6 - Energy 1 Training facility 4 3 - Renewable energy generation in Media center 4 2 SP,- Gt SP SP SP 1 Offices (type A) 10situ 7 - 2 Offices (type A) 10Renewable energy 7 purchase -  Bar (VIP, West Gallery) 4 0.5 - Water 3 Medical center 6Rainwater collection 6 system -     intelligent motion Optimization of water consumption  ‐ sprinklers detectors Waste Selective sorting in non‐public areas     Selective sourcing in public areas   ‐ ‐ Waste minimization 2 a, b, c, d a, b, c, d a, b, c, d a, b, c, d 1 the renewable energy generation in these case studies, is conducted by installing solar panels (SP) and geothermal power (Gt); 2 the minimization is achieved by applying the following strategies: (a) reusable cups; (b) food donation; (c) signage reuse; and (d) composting.

1.4. Italian Stadiums The process of renovation and construction of Italian stadiums started recently. Juventus F.C., A.C. Chievo Verona, Hellas Verona F.C., and Cagliari Calcio are the only teams in the Serie A which have already enhanced their arenas in Turin, Verona, and Cagliari, respectively. Atalanta B.C., F.C. International Milan, A.C. Milan, and A.S. Rome have started the same procedure to improve their stadiums (Table 2). The Bentegodi Arena in Verona is the first Italian stadium to be partially covered. The 42,000‐seat arena is provided a PV plant integrated on the roof that powers up to 1 MW with its 13,300 panels [48]. The PV system allows reduces emissions by 550 tons of CO2 and supplies energy equal to the consumption of 350 families. The Allianz Stadium in Turin was realized after the old Delle Alpi Stadium had been partially demolished. The new arena was built in the same area and some of the materials and structures from the previous building (i.e., concrete, aluminum, steel, and copper) was employed, which achieved a reduction in terms of environmental impact and economics, saving up to 2.3 million of euro. Furthermore, the energy consumption is partially covered by integrated solar panels coupled to PV modules. The first covers the heating energy requirements by delivering hot water with a district network; the latter powers up to 100 kWp [49].

Table 2. List of the main stadium plans which have already been discussed by the local municipalities or which are under discussion at the moment [50,51].

Stadium Capacity City Tenant Opening Stadio della Roma 52,500 Rome A.S. Rome 2020 New Fiorentina Stadium 40,430 Florence A.C.F. Fiorentina ‐ New Cagliari Stadium 30,000 Cagliari Cagliari Calcio 2021 New Stadio Castellani 20,266 Empoli Empoli F.C. ‐ Atleti Azzurri D’Italia Arena 24,000 Bergamo Atalanta B.F.C. 2020

Energies 2018, 11, x FOR PEER REVIEW 5 of 17

Table 1. UEFA Euro 2016 new arenas’ configuration [47]. Energies 2018, 11, 2396 9 of 16 Features Lille Nice Bordeaux Lyon Accessibility ApproximateTable 7. Cont. UEFA capacity 50,000 36,000 42,000 58,000 Energies 2018, 11, x FOR PEER REVIEW Wheelchair spaces 230 9 120of 17 120 246 System Easy‐Hoursaccess per seats Day close to amenities 115 100 100 123 Level Bar (VIP, WestZone Gallery) 4 Days per0.5 Week ✓ - 3 TPS *Transport ASHP ** Medical center 6 6 - ✓ Conference room 4 0.5  -    Conference room Public transport4 accessibility0.5 ✓ - 4 Restaurant 6 7 - Energy✓ 4 RestaurantArea relax 6 4 7 6 - - Renewable energy generation in 5 OtherArea relax services 4 2 6 3 SP,- Gt ✓ - SP SP SP 1 65 Other Other services services 2 2 situ 3 ✓ - - 76 Other Other services services Renewable2 2 energy purchase3 ✓ - -  87 Other Other services services 2 2 3 ✓ Water- - 98 Other Offices services (type B) Rainwater2 4 collection system 0,53 ✓ - -    9 * TPSOffices stands for(type Thermal B) Power Station;4 ** ASHP stands for0,5 Air Source Heat✓ Pump. - intelligent motion Optimization of water consumption  ‐ * TPS stands for Thermal Power Station; ** ASHP stands for Air Source Heat Pump. sprinklers detectors Waste 2.3.2.3. Investigated Investigated Scenarios Scenarios Selective sorting in non‐public areas     TwoTwo scenarios scenarios were were simulated simulated ininSelective DB:DB: ScenarioScenario sourcing 0 and in Scenario Scenario public areas1. 1.   ‐ ‐ ScenarioScenario 0 0 corresponds corresponds to to the the present presentWaste arena arena minimization configuration.configuration. 2 It It was was modeled: modeled:a, b, c, d (i) (i) to to verify verifya, b, the c, the d a, b, c, d a, b, c, d systems’systems’ declared declared performance performance levels;levels; (ii)1 theto identify renewable over over- energy- or or under under-sized generation-sized inplants; plants; these and case and (iii) studies, (iii) to define to is define conducted a a by installing solar panels (SP) basisbasis for for comparing comparing Scenario Scenario 1. 1. In In this this paper, paper,and onlygeothermal only (iii) (iii) is discussedpoweris discussed (Gt); since 2 thesince itminimization permitsit permits estimating estimatingis achieved the theby extra applying the following strategies: (a) energyextra demandenergy demand due to due the newto the facilities new facilities addedreusable added to cups; the to arena.(b) the food arena. The donation; discussion The discussion (c) signage of both of reuse; both (i) and and (i) and (ii)(d) composting. can(ii) be foundcan be in [ found52]. Scenario in [52]. 0 Scenario configuration 0 configuration is the one isdescribed the one in described the previous in the section. previous Most section. zones Most located underzones the located West Gallery under the are West served Gallery by1.4. the Italian are methane-TPS, served Stadiums by the whereas methane the- remainingTPS, whereas daily-used the remaining areas are daily-used areas are heated (or cooled) by the ASHP. The modeling stage was conducted after the heated (or cooled) by the ASHP. The modeling stage was conducted after the stadium was inspected stadium was inspected to acquire informatioThe processn regarding of renovation structural and packages construction as well of as Italian systems’ stadiums started recently. Juventus F.C., to acquire information regarding structural packages as well as systems’ layout. layout. A.C. Chievo Verona, Hellas Verona F.C., and Cagliari Calcio are the only teams in the Serie A which Scenario 1 corresponds to the enhanced configuration, where the modern stadium offers services Scenario 1 corresponds to thehave enhanced already configuration, enhanced their where arenas the in modern Turin, Verona, stadium and offers Cagliari, respectively. Atalanta B.C., F.C. not limited to sports events. In this scenario, the arena is open for the whole week, and the areas below services not limited to sports events.International In this scenario, Milan, the A.C.arena Milan, is open and for theA.S. whole Rome week, have and started the the same procedure to improve their theareas galleries—north, below the galleries east— andnorth, south eaststadiums in and addition south (Table toin theaddition2). existent to the west—are existent west exploited—are exploited as restaurants, as 2 beautyrestaurants, centers, beauty training centers, facilities, training sports facilities,The stores, Bentegodi etc. sports In total, stores,Arena there etc.in are Verona In 20,000 total, is mthere theorganized arefirst 20,000Italian into m twostadium2 to be partially covered. The levels,organized as described into two in levels, Figure as3. However,described42,000 in‐ theyseat Figure arearena so 3. faris However, provided from the th a existentey PV are plant so thermal far integrated from stations the on existent that the theroof that powers up to 1 MW with its realizationthermal stations of a new that heating the realization system13,300 was of a hypothesized. new panels heating [48]. systemThe Indeed, PV was system the hypothesized. areas allows hosting reduces Indeed, match-day emissions the servicesareas by 550 tons of CO2 and supplies energy arehosting mainly match open-day spaces, services neither are heatedmainlyequal open nor to cooled. spaces,the consumption neither heated of 350 nor families.cooled. The Allianz Stadium in Turin was realized after the old Delle Alpi Stadium had been partially demolished. The new arena was built in the same area and some of the materials and structures from the previous building (i.e., concrete, aluminum, steel, and copper) was employed, which achieved a reduction in terms of environmental impact and economics, saving up to 2.3 million of euro. Furthermore, the energy consumption is partially covered by integrated solar panels coupled to PV modules. The first covers the heating energy requirements by delivering hot water with a district network; the latter powers up to 100 kWp [49].

Table 2. List of the main stadium plans which have already been discussed by the local municipalities or which are under discussion at the moment [50,51].

(a) Stadium (bCapacity) City Tenant Opening Stadio della Roma 52,500 Rome A.S. Rome 2020 FigureFigure 3. 3.Dacia Dacia Arena,Arena, Udine,Udine, vertical sections sectionsNew Fiorentina of of the the:: (a ()a West) WestStadium Gallery; Gallery; (b ()b East)40,430 East Gallery. Gallery. Florence A.C.F. Fiorentina ‐ New Cagliari Stadium 30,000 Cagliari Cagliari Calcio 2021 TheThe heating heating energy energy performances performances of the new areas areas were were evaluated evaluated for for each each zone zone by byconsidering considering New Stadio Castellani 20,266 Empoli Empoli F.C. ‐ thethe Primary Primary Energy Energy Index Index (PEi).(PEi). TheThe PEi refers to to pri primarymary energy energy for for heating heating calculated calculated yearly yearly for for Atleti Azzurri D’Italia Arena 24,000 Bergamo Atalanta B.F.C. 2020 eacheach square square meter. meter.It It representsrepresents thethe ratio between the the energy energy demand demand to to achieve achieve anan 18 18°C◦ indoorC indoor temperaturetemperature and and the the net net surface. surface. DependingDepending on on the the energy energy categories categories which which were were assigned assigned to the to the differentdifferent rooms, rooms, an an upper upper limit limit andand aa lowerlower limit,limit, expressed in in kWh/m kWh/m2 per2 per year, year, can can be bedefined defined in in TableTable8[ 854 [54].]. Then, Then, a a mean mean valuevalue waswas chosen and and multiplied multiplied by by the the surface surface to toquantify quantify the the energy energy requirements for guaranteeing the achievement of the thermal comfort zone in every area.

Energies 2018, 11, 2396 10 of 16

Energies 2018, 11, x FOR PEER REVIEW 10 of 17 requirements for guaranteeing the achievement of the thermal comfort zone in every area. Accordingly, theAccordingly, properties of the the properties building envelopeof the building were envelope defined and were used defined as input and valuesused as in input DB environment.values in DB environment. Table 8. Classification depending on Primary Energy Index levels. Table 8. Classification depending on Primary Energy Index levels. Lower Limit [kWh/m2 year] Category Upper Limit [kWh/m2 year] Lower Limit- [kWh/m2 year] Category A Upper Limit [kWh/m 26.0 2 year] 26.0- BA 26.0 39.0 39.026.0 CB 39.0 52.0 52.039.0 DC 52.0 65.0 65.0 E 78.0 52.0 D 65.0 78.0 F 91.1 91.165.0 GE 78.0 130.1 78.0 F 91.1 91.1 G 130.1 The configuration of the two levels and the hosted functions are reported in Figure4a (Level 0) 2 2 and FigureThe4 configurationb (Level −1) of as the modeled two levels on DB and environment. the hosted functions Level 0 isare 8000 reported m and in itFigure includes 4a (Level a 6000 0) m 2 areaand for Figure match-day 4b (Level services −1) as (toilets, modeled bars, on DB and environment. other services) Level and 0 twois 8000 1000 m2 m andextended, it includes uncompleted a 6000 m2 zones.area The for completed match-day parts—currently services (toilets, open bars, air—could and other be services)closed with and glazed two envelopes 1000 m2 extended, and heated byuncompleted the new system zones. to improve The completed users’ comfort. parts— Consideringcurrently open their air envelope—could (glazed) be closed is not with particularly glazed effectiveenvelopes in terms and ofheated thermal by the insulation, new system they towere improve evaluated users’ as comfort. C category Considering zones according their envelope to Table 8. Differently,(glazed) is the not uncompleted particularly rooms, effective which in terms would of hostthermal a fast insulation, food restaurant they were and evaluated a wellness as area, C shouldcategory achieve zones at according least a B level to Table of energy 8. Differently, performance. the uncompleted Level −1 is rooms, located which below would street host level a andfast is characterizedfood restaurant by an and extension a wellness of 12,000area, should m2. Two achie facilitiesve at least would a B level be realized of energy in thisperformance. part of the Level arena: −1 an indooris located training below center street and level a sports and is store characterized to promote by Udinese’san extension merchandising. of 12,000 m2. Two Both facilities were considered would in thebe realized calculation in thisas a Bpart category of the zone. arena: an indoor training center and a sports store to promote Udinese’s merchandising. Both were considered in the calculation as a B category zone.

(a) (b)

FigureFigure 4. Dacia4. Dacia Arena, Arena, areas areas served served by by the the newnew system;system; from the left left:: ( (aa)) Level Level 0; 0; (b (b) )Level Level −1.− 1.

3. Results3. Results and and Discussion Discussion TheThe proposal proposal for for a a sustainable sustainable plant plant toto powerpower the new zones zones (East, (East, North, North, and and South South Galleries) Galleries) waswas defined defined considering considering the the results results achieved achieved byby CIRIAF research research group group about about energy energy efficiency efficiency [55]. [55 ]. Firstly,Firstly, the the energy energy demand demand was was evaluated evaluated as as describeddescribed on the spec specificific section. section. Then, Then, two two alternative alternative systems’systems’ layouts layouts were were designed designed and and analyzedanalyzed from an energy energy point point of of view. view. In In one one system, system, the the PV PV plantplant is coupledis coupled with with a a geothermal geothermal heat heat pump,pump, and,and, in the other other system, system, the the PV PV cells cells are are integrated integrated withwith a biomassa biomass plant plant and and an an absorption absorption chiller chiller forfor coolingcooling and heating. Those Those plants plants would would power power thethe new new areas areas hosting hosting non-sport non-sport functions functions (training(training facilities, restaurants, restaurants, wellness wellness areas, areas, etc.), etc.), which which cannotcannot be be efficiently efficiently connected connected to to the the heating heating systemsystem presentpresent in the West West Gal Gallery.lery.

3.1.3.1. Energy Energy Requirements Requirements InIn this this section, section, the the results results of of the the dynamic dynamic simulationssimulations conducted conducted in in Design Design Builder Builder environment environment areare reported reported to to define define the the building building energy energy demand. demand. The energy consumptions are referred to Domestic Hot Water (DHW), heating, and cooling. They are organized based on the supplying plants: (a) methane-TPS; (b) ASHP; and (c) the new

Energies 2018, 11, 2396 11 of 16

EnergiesThe 2018 energy, 11, x FOR consumptions PEER REVIEW are referred to Domestic Hot Water (DHW), heating, and cooling.11 Theyof 17 are organized based on the supplying plants: (a) methane-TPS; (b) ASHP; and (c) the new plant. The plant.results The of Scenarioresults of 0 includedScenario 0 Plants included (a) and Plants (b), (a) whereas and (b), Scenario whereas 1 also Scenario exploits 1 also extra exploits energy extra from 2 energyPlant (c) from to heat Plant the (c) new to heat area the (22,000 new marea2). (22,000 m ). TheThe assessments underline underline how how the the increment increment of heated of heated surface surface could could lead to lead increase to increase the heating the heatingenergy demandenergy demand and the and cooling the cooling needs byneeds 35% by and 35% 63%, and respectively. 63%, respectively. In particular, In particular, the new the plantnew plant(Scenario (Scenario 1) should 1) should supply supply 783,000 783,000 kWh for kWh heating for heating and 159,500 and kWh159,500 for kWh cooling, for ascooling, reported as inreported Table9 inand Table Figure 9 and5. Figure 5.

methane-TPS ASHP new plant

6.0E+05 ]

2 5.0E+05

4.0E+05

3.0E+05

2.0E+05

1.0E+05

Energy requirements Energy requirements [kWh/m 0.0E+00

-1.0E+05 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

FigureFigure 5 5.. EnergyEnergy demand demand evaluated evaluated by by Design Design Builder Builder software software tool. tool. The The heating heating energy energy needs needs are are reported as positive values, while the cooling ones are considered negatives. reported as positive values, while the cooling ones are considered negatives. Table 9. Energy demands through the year for heating and cooling referred to each plant. Table 9. Energy demands through the year for heating and cooling referred to each plant. Heating Energy Demand Cooling Energy Demand Plant Heating Energy Demand Cooling Energy Demand Plant Total [kWh/year] Max [kWh/year] Total [kWh/year] Max [kWh/year] Total [kWh/year] Max [kWh/year] Total [kWh/year] Max [kWh/year] methanemethane-TPS-TPS 1,278,700 1,278,700 305,000 305,000 - -- - ASHP 165,000 50,000 94,000 27,500 newASHP plant 165,000 783,000 50,000 163,000 94,000 159,500 27,500 44,000 new plant 783,000 163,000 159,500 44,000 3.2. Alternative Strategies towards Zero Energy Stadiums 3.2. Alternative Strategies towards Zero Energy Stadiums The PV plant is integrated on the roof above the East and South Galleries. The panels are The PV plant is integrated on the roof above the East and South Galleries. The panels are characterized by low tilt angles ranging from 3◦ and 9◦, as reported in Figure6. The roof is divided characterized by low tilt angles ranging from 3° and 9°, as reported in Figure 6. The roof is divided into three rings (outer, middle, and inner). Except for the inner part that is made of transparent panels into three rings (outer, middle, and inner). Except for the inner part that is made of transparent to permit daylight reaching spectators, the remaining two sections (middle and outer) are covered by panels to permit daylight reaching spectators, the remaining two sections (middle and outer) are PV cells (about 7000 m2)[56]. covered by PV cells (about 7000 m2) [56]. The energy produced by the installed modules was estimated by the software Sunny Design for The energy produced by the installed modules was estimated by the software Sunny Design for each roof’s sector. According to the current regulations [57], both the age of the infrastructure (part of each roof’s sector. According to the current regulations [57], both the age of the infrastructure (part the arena has been built after 2017) and the PV extension (7000 m2) were considered for evaluating the of the arena has been built after 2017) and the PV extension (7000 m2) were considered for evaluating minimum required power, which turns out to be 140 kW. As summarized in Table 10, the plant can the minimum required power, which turns out to be 140 kW. As summarized in Table 10, the plant reach a peak power of 780 kWp (815,000 kWhe/year). It permits to supply enough energy for fitting can reach a peak power of 780 kWp (815,000 kWhe/year). It permits to supply enough energy for the requirements related to lighting during the match day (around 60,000 kWhe/year) [52]. fitting the requirements related to lighting during the match day (around 60,000 kWhe/year) [52].

Energies 2018, 11, 2396 12 of 16 Energies 2018, 11, x FOR PEER REVIEW 12 of 17

PV plant

(a) (b)

FigureFigure 6. 6Design. Design ofof thethe photovoltaic plant plant integrated integrated on onthe the roofing: roofing: from from the left the: ( left:a) section (a) section;; (b) plan. (b ) plan.

Table 10. Energy requirements for heating and cooling referred to each plant. Table 10. Energy requirements for heating and cooling referred to each plant. 2 LocationLocation ExposureExposure Tilt Tilt Angle Angle SurfaceSurface [m [m2] ] PowerPower [kW] [kW] Inverter Inverter [n] [n] SouthSouth 10521052 120 120 12 12 outerouter ring ring SoutheastSoutheast 9°9 ◦ 663 663 72 727 7 EastEast 1584 1584 180 180 18 18 SouthSouth 10521052 120 120 12 12 ◦ middlemiddle ring ring SoutheastSoutheast 3°3 982 982 106 106 11 11 EastEast 1584 1584 180 180 18 18

OnOn the the first first proposed proposed solution, solution, the the photovoltaic plant plant is is coupled coupled to to a a geothermal geothermal plant plant for for supplyingsupplying electricity electricity andand thermalthermal energy. energy. The The ground ground properties properties were were evaluated evaluated according according to [58]. to A [58 ]. A yield equal to 50 W/m W/m was was estimated estimated for for the the surroundings. surroundings. Based Based on onthe the dynamic dynamic simulation simulation results, results, the heat pump should guarantee around 500 kWt and 175 kWf. The proposed system includes two the heat pump should guarantee around 500 kWt and 175 kWf. The proposed system includes two heat heat pumps [59] which can power up to 240 kWt for each with a Coefficient of Performance (COP) pumps [59] which can power up to 240 kWt for each with a Coefficient of Performance (COP) equal toequal 4.6. The to 4.6. requirements The requirements to the groundto the ground in terms in terms of power of power are 390 are kW, 390 thuskW, thus 38 probes 38 probes of 200 of m200 depth m shoulddepth be should realized. be Nevertheless, realized. Nevertheless, considering considering the results obtainedthe results on obtained the “Sistema on thedi Climatizzazione “Sistema di Climatizzazione da fonti Energetiche Rinnovabili” (SCER) pilot project [60], it is possible to reduce da fonti Energetiche Rinnovabili” (SCER) pilot project [60], it is possible to reduce the probe number to the probe number to 13 as long as a 250 m3 heat storage tank is added. Although the plant is largely 13 as long as a 250 m3 heat storage tank is added. Although the plant is largely recognized as efficient recognized as efficient from an energy point of view, the interventions for its realization are from an energy point of view, the interventions for its realization are characterized by a high level of characterized by a high level of environmental impact. However, the extra power produced can be environmental impact. However, the extra power produced can be delivered to the energy grid to delivered to the energy grid to lower the environmental impact of the facility. Indeed, only 260,000 lower the environmental impact of the facility. Indeed, only 260,000 kWh/year of the 815,000 kWh per kWh/year of the 815,000 kWhe per year powered by the PV plant are directly exploited by the heate yearpump, powered and the by buil the PVding plant is energetically are directly autonomous exploited by for the the heat 80% pump, of the and investigated the building period. is energetically autonomousThe solution for the proposed 80% of the in investigatedthis paragraph period. evaluated the possibility of exploiting biomass instead of The geothermal solution power. proposed Using in this biomass paragraph represents evaluated an efficient the possibility strategy toof exploitingachieve the biomass reduction instead of offossil geothermal energy power. source Using exploitation biomass as represents confirmed an by efficient several strategy studiesto conducted achieve the by reduction the European of fossil energyRenewable source Energy exploitation Council as confirmed[61]. Biomass by severalcould cover studies up conducted to the 50% by of the the European European Renewable energy Energyrequirements Council by [61 contributing]. Biomass at could the same cover time up to to the the achievement 50% of the of European the goals energydeclared requirements on COP 22 in by contributingterms of reduction at the same of greenhouse time to the gas achievement emissions [62,63]. of thegoals In this declared proposal, on the COP PV 22panels in terms are integrated of reduction ofwith greenhouse a biomass gas plant emissions for supplying [62,63]. the In thisrequired proposal, heating the and PV cooling panels energy. are integrated The plant’s with layout a biomass is plantsimilar for supplying to the onethe pro requiredposed on heating [55]. The and boiler cooling has energy. a nominal The plant’s power layout of 500 is kW similart obtained to the by one proposedinstalling on two [55 ].modules The boiler by 250 has kW a nominalt [64]. Furthermore, power of 500 two kW thermalt obtained storages by installing were designed two modules for the by heating system and the DHW: their volumes are equal to 15 m3 and 6 m3, respectively. The cooling 250 kWt [64]. Furthermore, two thermal storages were designed for the heating system and the DHW: theirenergy volumes needs are are equal supplied to 15 by m an3 and absorption 6 m3, respectively. chiller connected The cooling to the biomass energy needsplant: the are water supplied heated by an absorptionto 106 °C chillerby the connected biomass plant to the generates biomass 175 plant: kWf the. The water cooling heated plant to is 106 completed◦C by the by biomass a 675 kW plant evaporative tower. In conclusion, the biomass consumption would be around 1250 m3 per year generates 175 kWf. The cooling plant is completed by a 675 kW evaporative tower. In conclusion, the considering the calorific power of the chosen biomass (700–900 kWh/m3) and the yearly energy biomass consumption would be around 1250 m3 per year considering the calorific power of the chosen demand. biomass (700–900 kWh/m3) and the yearly energy demand. The primary energy is calculated for both the proposed solutions. In the first, the primary The primary energy is calculated for both the proposed solutions. In the first, the primary energy energy exploited by the geothermal plant is the electricity derived from the PV panels integrated on exploited by the geothermal plant is the electricity derived from the PV panels integrated on the roof.

Energies 2018, 11, 2396 13 of 16

In the second, the primary energy consumption of the biomass plant is the chemical energy from biomass. Considering that the woodchips are characterized by a lower heating value and a density equal to 3.4 kWh/kg and 325 kg/m3, respectively [55], as well as the yearly woodchips consumption of 1250 m3 (440,000 kg), the primary energy is estimated around 1,500,000 kWh/year. This value is higher than the primary energy required by the geothermal heat pump (260,000 kWh/year). Table 11 summarizes the energy parameters presented in this study. These values are not enough to define the best solution from an environmental and economic point of view but they allow energetically evaluating the two alternatives as stated as the aim of the study.

Table 11. Energy requirements for heating and cooling referred to each plant.

Primary Energy Configurations Plant Size Primary Energy Type Consumption [kWh/year] Alternative a Geothermal Heat Pump Electricity form PV 260,000 (500 kW , 175 kW ) Biomass boiler and t f Chemical Energy from Alternative b 1,500,000 Absorption Chiller biomass

4. Conclusions The present work proposes a cluster of actions to reduce energy use of Dacia Arena. Most have already been realized during the upgrading of the West Gallery, and the demolition and reconstruction of the North, East and South Galleries. The interventions allow the creation of new areas—about 20,000 m2—available for commercial activities. Indeed, the economic crisis and the diffusion of other forms of on demand entertainment caused a reduction of the number of supporters at the stadium. Thus, developing and promoting activities that could be complementary to football would provide new profitability. The sustainability of the interventions has been evaluated in terms of operational energy use. The strategies included: (i) a photovoltaic system integrated on the new roof, for providing electricity; and (ii) a geothermal or a biomass plant for heating and cooling. The PV system turns out to be able to yearly power up to 815,000 kWhe. In the case of heat pump installation, part of that amount (around 500,000 kWh) is a surplus and it is not directly exploited by the arena facility. It is immitted in the energy grid and delivered to close neighborhoods to compensate the stadium’s carbon emissions. Differently, in the configuration with a biomass plant, the totality of the PV production could be delivered to the energy grid. In the first plant layout, the use of a geothermal heat pump system including two 240 kWt heat pumps was proposed. In the second, the biomass plant was composed by a boiler having a nominal power of 500 kWt (two modules by 250 kWt), integrated with an absorption chiller (175 kWf.) and an evaporative tower (675 kW). The energy analyses conducted on the two alternatives for the stadium plants layout demonstrated the feasibility of the proposed approaches, which could be replicated in other facilities.

Author Contributions: Writing—Original Draft Preparation, M.M.; Investigation, A.P.; Data Curation, V.C.; Validation, G.M.; and Supervision, A.N. Funding: This research received no external funding. Acknowledgments: The authors thank the technical studio Area Progetto Associati from Perugia and the Engineer Carlo Regni, which worked on the structural planning and the plant design of the new Dacia Arena in Udine, for the availability on sharing the results of their work with the Department of Engineering of the University of Perugia. Conflicts of Interest: The authors declare no conflict of interest. Energies 2018, 11, 2396 14 of 16

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