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Zero-energy skylines

By Lauren Duensing

November 2010- Tall towers of shimmering glass and solid metal are what make skylines so iconic--from New York to Dubai. But, globally, those skyscrapers, office buildings and condominiums are responsible for nearly 40 percent of worldwide energy demand and nearly half of greenhouse gas emissions, according to the U.S. Department of Energy.

Some existing structures aim to reduce consumption through retrofits. The Empire State Building launched a sus­tainability program, which includes a whole-systems retrofit, that is predicted to optimize the performance of the existing building and save a maximum of $4.4 million in energy costs.

The Department of Energy plans to install solar panels and a solar hot water heater on the White House by the end of next spring. This will be the third time the building or its grounds has been retrofit with solar power.

Because of programs like these, photovoltaic systems--devices that convert light energy directly into electricity--are gaining in popularity. Many of these systems are retrofits. However, the next-generation modules are building-integrated photovoltaic systems and are used as part of a total design strategy, offering architects more flexibility.

"Today’s standard PV modules and their application on roofs and even in roofs and on facades are so strongly limited and inflexible to meet any architectural requirement that they are hardly taken into consideration by building owners and planners. BIPV means using PV-modules as any other building or cladding material and providing maximum of flexibility in terms of size, function and aesthetic options. The more we can offer on this side, the better the acceptance will be. The potential is huge," says Max Radt, architect and head of the Solar Competence Centre, Hydro Building Systems, Barcelona, Spain.

Integrated into a building’s facade, BIPVs can be used in both residential and commercial structures, Radt says. "Nevertheless, the applications in commercial and public buildings are much more frequent. BIPV solutions are often applied in emblematic buildings (e.g. company headquarters) and public buildings (e.g. schools) to show a compromise toward energy efficiency and environmental consciousness."

Although the global economic crisis has hit the construction industry hard, which has a negative effect on BIPV manufacturers, the market still has a lot of untapped potential.

According to Radt, "true building-integrated photovoltaics have more functions besides pure energy production. In our products, we design a combination of what we call ‘passive effect’ (energy saving) and the ‘active effect’ (energy production) is pursued. A perfect example is the sun-shading device with integrated PV cells. The combination of both the effects and the aesthetic approach towards an architecturally attractive solution is the key for success in the future."

The ultimate goal for BIPVs is to contribute toward zero-energy buildings--a structure with greatly reduced energy needs because of efficiency gains so the balance of energy needs can be met with renewable technologies.

"Hydro Building Systems delivers many solutions contributing to our strategic goal of designing zero-energy buildings," Radt says. "We are talking about windows and facades with very high insulation rates, about the integration of intelligent ventilation systems and building automation as well as solar thermal solutions and finally BIPV."

Start at the beginning
BIPVs are effective both in new construction and retrofits where suitable aluminum systems are provided to integrate the solar panels into the facade.

"The decision of integrating photovoltaics is made by the architect or owner," says Sebastien Lebris, engineering service manager, for Metalbuilder Miroiterie RAUB, Guilers, France. He points out in certain projects it is necessary "to reach performing energetic balance, and, as a metal builder, we will propose the best constructive solutions to achieve this result."

Radt says BIPVs make sense only as part of the full building plan. "It is absolutely necessary for planners to consider BIPV from the very beginning of the building concept," he notes. "BIPV is not an add-on you can just put at the latest design stage, which, unfortunately, happens frequently. The ideal building for BIPV is a design which has a holistic approach toward an energy-efficient design, considering all possible measures from shaping the building, high thermal insulation, efficient heating and cooling systems to BIPV."

Hydro Building Systems designs solutions for integrating photovoltaic modules into aluminum curtain wall systems, glass roofs, sun shading systems and ballustrades. "For this purpose, we are designing new aluminum systems or modifying our existing systems in order to be able to receive the PV-modules and cabling," Radt says. "We also specify the minimum requirements for PV-modules for building-integrated solutions."

And in November, Hydro Building Systems will begin marketing the first complete BIPV sun shade catalog solution to metalbuilders.

Metalbuilder Miroiterie RAUB is using Technal brand aluminum systems from Hydro Building Systems in its projects. The 50-year-old Technal brand is a pioneer in architectural aluminum facade systems. Technal systems can provide enhanced thermal efficiency, design flexibility, ease of installation and long-term performance. They are tested to European standards, or relevant ones for overseas projects, for wind resistance, water tightness and air permeability. Hydro Building Systems has been pushing for energy-efficient solutions for years, including BIPVs, which are marketed by two of its commercial brands, Technal and Wicona.

When working with BIPVs, Lebris says one of his main challenges is managing the cables and wires. "One must consider that photovoltaic modules are a kind of glass infill, but the aluminum system has to be adapted to integrate the electrical components of the photovoltaic panels.

"There is yet no real catalog solution for these kinds of applications, which are quite new," Lebris continues. "For the ‘Communauté des communes’ building, my challenge was to design some specific machining with Technal curtain walls to integrate and conceal cables and diodes in a secure way in the aluminum profiles. Then, this solution had to be implemented at the workshop. We managed the installation on site with our teams, but in addition, for the photovoltaics, we had to coordinate with the electricians. The electrical connection of all PV panels on the curtain wall system and the connection to the electric installation of the building has to be done by workers qualified in PV electricity."

Encouraging renewable energy
Although BIPVs are a new technology, there is a lot of growth potential as a result of government incentives encouraging renewable energy.

"There is an increase in the demand for buildings relevant to the BBC label [Bâtiments Basse Consommation] low-energy consumption, which is less than 50 kilowatt hours per square meter per year or for zero-energy buildings," Lebris says. "Nevertheless, the projects that finally come out with these solutions are still very few. Building-integrated photovoltaics solutions are not well known among architects and owners because it is difficult to evaluate the initial additional cost and the return on investment, as well as finding the relevant constructive solutions and the competent fabricators to install them properly."

"BIPVs clearly have big potential anywhere in the world," Radt says. "Buildings are responsible for approximately 40 percent of the worldwide energy demand. Therefore, any improvement in the buildings’ yearly energy demand will have an impact on the worldwide energy consumption and associated CO2 emissions. BIPV is part of the solution and can provide part of the energy used in buildings and at the same time, help reduce the energy demand by shading. The more efficient buildings get through improved thermal insulation and better glazing, the more important the contribution of renewable production to the building’s energy balance will become.

"The aim today is to go toward zero-energy buildings, which means reaching the goal equalling the yearly energy balance of energy demand and on-site production," Radt continues. "Legislation plays a major role. By setting ambitious targets on low-energy demands of buildings per built surface area and year, the governments will certainly push indirectly for integrated renewable energies such as BIPV. This kind of legislation, setting clear targets in the direction of zero-energy buildings, is much more useful than any kind of feed in tariff for photovoltaics." MM

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