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ROOFS WITH PHOTOVOLTAIC SYSTEMS - Index S.p.A.

ROOFS WITH PHOTOVOLTAIC SYSTEMS - Index S.p.A.

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INTRODUCTIONThe architecture used in sustainable buildingis not limited to the design of a “conserving”shell in terms of energy: current design researchis intended to make the building shellperform an “active” energy role through theapplication of solar energy collectors and photovoltaicsystems for solar energy production.The European Directive promoting the use ofrenewable energy sources (Directive 2001/77/EC), assimilated in Italy through Law Decree387 of 2003 and followed up by subsequentimplementation regulations, introduced ContoEnergia, a working account scheme incentivisingthe production of electricity using solarenergy from photovoltaic systems connectedto the electricity mains on a permanent basis.Italy is one of the sunniest European countries,especially in the Southern regions, butits photovoltaic industry is one of the leastdeveloped in the world.It is estimated that in Italy, using current technology,a photovoltaic system is capable ofgenerating approximately 1150 kWh per yearfor each kWp of photovoltaic modules installed,a value which gradually rises to 1500kWh as you move southwards. Germany, inspite of its less favourable geographical position,is particularly advanced in its productionof electricity from solar energy; however, foreach kWp of photovoltaic modules installed,just 600 kWh/kWp is produced per year.Italy's favourable climatic situation allows thebeneficiary to recoup all outlay costs withinthe space of ten years, and to make approximatelythe same amount in the following tenyears. In the south, the situation improveseven further, as the investment tends to berepaid within approximately 8 years. Roofs ontop of buildings, especially non-walkable flatroofs with a visible waterproof covering, areGBC ITALIA (Green Building Council)AND LEED CERTIFICATIONGBC Italia, to which INDEXbelongs, has the task of usingthe guidelines commonto everyone in the LEEDinternational community todevelop the characteristicsof the LEED Italia sys-member of GBC Italiatem, which must take intoconsideration the specific climatic, buildingand legislative conditions in Italy.LEED opts for a view of sustainability by makingthe most of all opportunities to reduce thevarious kinds of environmental impacts andharmful emissions of the buildings being built.The LEED (Leadership in Energy andEnvironmental Design) standards are parametersfor sustainable building developed in theUSA and applied in 40 countries throughoutthe world. They indicate the requirementsfor eco-compatible buildings, able to “work”sustainably and self-sufficiently energy-wise. Itis essentially a rating system for the developmentof “green” buildings.LEED is a certification, which may be obtainedon a voluntary basis, where the designer actuallydeals with collecting data for the assessment.The system is based on the awardof credits for each of the requirements thatcharacterise the sustainability of the building.The certification level achieved comes fromthe sum of the credits.unused surfaces which could conveniently beutilised for the production of electricity fromsolar energy by means of a photovoltaic solarThe assessment criteria used by LEED (2009version) are grouped into six categories (+1only valid in the USA), which envisage one ormore compulsory prerequisites and a numberof environmental performances that conributeto the building’s final score:• Sustainable sites(1 prerequisite, 26 points)• Efficient water consumption(1 prerequisite, 10 points)• Energy and atmosphere(3 prerequisites, 35 points)• Materials and resources(1 prerequisite, 14 points)• Indoor environmental quality(2 prerequisites, 15 points)• Innovation and design process (6 points)• Regional priority (4 points) only applicablein the USAThere are 4 rating levels:• Certified: between 40 and 49 points• Silver: between 50 and 59 points• Gold: between 60 and 79 points• Platinum: more than 80 pointsThe following point in the LEED regulationsincludes the solar reflectance index:• SS Credit 7.2: Heat Island Effect - RoofSRI (solar reflectance index) limits of the roofingmaterialspanel system, in compliance with sustainablebuilding criteria.USEFUL INFORMATIONREGARDING <strong>PHOTOVOLTAIC</strong>PANELS INSTALLED ON A ROOFOrientation and slopeThe ideal orientation and slope for photovoltaicpanels is facing south, at approx. 30°; however,satisfactory results can also be achieved withsouth-east and south-west facing panels, atsloping angles of 20° and 40°.On a flat surface, output is reduced by approximately10% in relation to the figure achievedusing the ideal slope.System withdirected modulesSystem with flat,rigid modulesOutput and surfacesPhotovoltaic panels currently on the marketuse various technologies, offering differentperformance levels. Using high-output modulesto achieve a given power value only requires asmall surface area, saving space and makingit easier to position the panels in the sunniestareas on the roof, avoiding shady spots.The mass per unit area of a photovoltaicsystemThe weight per square metre of the photovoltaicsystem is particularly important; it must bealigned with the extra load capacity of the roof.The load not only depends on the unit weightof the panel, but also on the roof installationmethod used.The impact of panels secured by means of aballast (in order to avoid puncturing the waterproofcovering) is linked to the amount of windin the area and the geometry of the roof, and isgreater than the impact of systems which aremechanically fixed to the support (the averageweight is 40-50 kg/m 2 ).However, innovative tubular photovoltaic modulesare available which do not require ballastsor fixings; these can withstand winds of around208 km/h and weigh 16 kg/m 2 .Ballasted systemSystem fixedmechanicallySystem with supportedinterlocking modules2 <strong>ROOFS</strong> <strong>WITH</strong> <strong>PHOTOVOLTAIC</strong> <strong>SYSTEMS</strong> Technical specifications

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