Building-Integrated Photovoltaics

With energy prices going through the roof, photovoltaic (PV) systems, which produce electricity from sunlight, are becoming more popular. However, the aesthetics (or lack thereof) of traditional PV systems, which were often free-standing panels on roofs or in yards, were seen as a drawback by many consumers.

Enter the Building-Integrated Photovoltaic (BIPV) system. BIPV systems consist of photovoltaic modules that are integrated into the building envelope, such as the roof or the façade. By simultaneously serving as building envelope material and power generator, BIPV systems can provide savings in materials and electricity costs, reduce use of fossil fuels and emission of ozone depleting gases, and add architectural interest to the building.

BIPVs are in use right here in sunny New York City!

• Millennium Towers (Battery Park City) - Solar cells were integrated into curtain wall solar panels, replacing side building materials. This system, designed and supplied by altPOWER, uses 126 BIPV panels, and was partially funded by the New York State Energy Research and Development Authority (NYSERDA).

• The Conde Nast Building (4 Times Square) - custom-manufactured thin-film PV panels replace mirror glass spandrels from the 37th to 43rd floors on the south and east faces of the tower.

• Whitehall Ferry Terminal - said to be Manhattan's largest BIPV project to date. 288 solar electric glass panels, manufactured by Atlantis Energy Systems, form the exterior of the terminal's facade and canopy. The 40 kW arrays, which cover over 8,000 square feet, will produce 52,000 kW of power annually. The panels also allow sunlight pass through, providing sunlight to interior areas.

• Stillwell Avenue Station (Coney Island) - the 76,000-square-foot solar roof, manufactured by RWE SCHOTT Solar, is expected to produce 250,000 kW hours annually. The roof, which contains 2730 BIPV panels, covers the full width of the station

Other residential buildings in Manhattan incorporating BIPVs include the Helena, the Verdesian, Tribeca Green, and the Solaire (see picture at right).

BIPVs can be integrated into various parts of a building, fulfilling specific aesthetic and structural needs:

• Roof-integrated systems integrate PV modules into each roof tile.

• Facade-integrated system can offset the cost of other facade materials.

• Semi-transparent or transparent installations can allow for some of the light to enter for day-lighting or viewing.

• BIPV can be used as a shading device. This method is highly efficient, depending on the type of PV modules used.

There are two major types of PV modules:

• Crystalline silicon uses wafers of silicon wired together and attached to a module substrate.
  
• Thin film technology, which utilises thin films of crystalline silicon grown on a foreign substrate like glass or steel, while less efficient, is easier to integrate.

While the cost of electricity produced from a BIPV system (when considering initial cost spread over the lifetime of the system, plus maintenance costs) can be more expensive than the average rate for utility supplied power, many states and the federal government have programs to reduce the capital cost and/or the installation cost of PV systems by providing tax credits, tax deductions and rebates. Through NYSERDA, New York State residents can get substantial cost-saving incentives and reduced loan rates for BIPV installation, which can help make such a system cost-effective for a single-family home or smaller multi-family dwellings. Check out the brochure, New York State is Making Solar Energy for Your Home More Affordable, a snippet of which appears below.


The importance of exploring alternative energy sources becomes more apparent every day. BIPVs can be incorporated into a remodeling project (considering redoing your siding?), so you don't even have to wait to build a new home! So, if you've been thinking about using solar energy in your home, BIPVs may be the way to go.

Concrete: The Green Debate

The debate over concrete as a green building material is on. While some (including the Portland Cement Association) are touting the eco-virtues of this material, others have been sounding the alarm regarding its carbon footprint.

So who’s right? Well, as with most things, concrete has both advantages and drawbacks. It does offgas a significant amount of CO2 during the production process, but there are steps you can take to ameliorate that effect (local sourcing is one of them, as the CO2 calculations usually factor in the high transport costs of this heavy material). So we’ve put together this list of pros and cons for your consideration:

Pros:

• Low-maintenance, smooth surface that won't offgas volatile organic compounds (VOCs) or collect allergens.


• Unique structural efficiency and inherently green qualities like a capacity to reduce recurring embodied energy (in other words, it’s highly durable and lasts a long time, and so you don’t need to keep replacing it, which takes energy).


• High solar thermal performance (highly insulating). Buildings with exterior concrete walls use less energy to heat and cool than similarly insulated buildings with wood or steel frame walls.


• Low maintenance requirements.


• Variations of concrete with high solar reflectance are considered effective for heat island mitigation.


• As it does not offgas like VOCs, concrete as an interior finish meets IAQ standards.


• If cements contains fly ash and/or slag (both post-consumer products) it can be considered post-consumer.


• Using recycled aggregate and a locally fabricated supply can reduce concrete’s environmental impact.
  

Cons:

• About 7% of global CO2 emissions come from concrete production.


• According to the U.S. EPA, 516 pounds of carbon emissions result from each ton of cement produced. CO2 is emitted from the mining and transportation of limestone and other concrete aggregates such as chalk and clay, the calcination process of limestone itself, the combustion of fuels in the kiln and associated power generation.

More developers are turning to cement in order to accumulate more LEED points. Buildings constructed of concrete are generally considered to be “mass,” meaning that they have enough heat-storage capacity to moderate daily temperature swings. The resulting benefit is reduced heating and cooling loads and lower energy consumption. The Solaire in battery Park City, the nation’s first green residential high-rise, makes use of the LEED credits and energy savings attributed to concrete. If you’re building or remodeling your home you might consider using concrete construction or pervious concrete for your driveway for stormwater management.

Riverhouse

Here at New York EcoSpaces, we've written a lot about topics like air quality and how the right air purifier can help alleviate asthma and allergies; low-VOC paints and finishes and how their use can dramatically increase the air quality of your home; and green roofs and how they help clean the air, save water, and provide an aesthetic link with nature.

We're glad to see that some forward-thinking residential developments in New York City are incorporating ideas such as these into their design. A good example of such a development is Riverhouse, a LEED-certified condominium tower in Battery Park City featuring a plethora of green features for a healthy planet and a healthy you, including:

• twice-filtered air with seasonally adjusted humidity levels,
• on-site water filtration,
• locally-sourced, renewable materials,
• low- or no-VOC paints, adhesives, and sealants,
  
• photovoltaic cells,
• green roofs that capture and recycle rainwater.

So if you're looking for someplace green to put down roots, feel free to contact me for more information.