After Gutenberg

Solar PV shading can generate electricity while reducing solar heating in the summer, which cuts cooling loads and glare. To reduce cost, such shading makes use of thin film, photo voltaic laminate systems.

A repeated theme at After Gutenberg is the growth of Building Integrated Photo Voltaic systems, especially using thin film, photo voltaic laminates. Commenting on a recent story in Renewable Energy Access about Suntech supplying photo voltaic cells for a 750 kW BIPV project in Sicily, Dr. Hussain Alrobaei indicated that, among BIPV approaches, he favored shade screens.

The application of Building-Integrated (BI) PV systems is particularly interesting because it demonstrates several advantages compared with conventional PV power plants. This application actually expands technological potential of PV systems even further, because in buildings, they can play more roles than solely producing electricity. Besides generating electricity integrated BIPV systems can also enhance a building’s beauty, visibility, and prestige.

Speaking of expanding the technological potential of PV systems, Sharp makes translucent solar PV panels that incorporate light-emitting diodes to provide illumination.

Sharp LumiWall allows for passive solar day lighting because the panels are translucent. The panels capture solar energy because they are comprised of thin film, photo voltaic laminate. Also, the panels integrate LEDs (Light Emitting Diodes), so that architects could use the panels as a source of lighting 24/7. Even though very efficient, LED lighting previously was scorned as insufficient. Yet LED lighting has been improving.

There are two main BIPV application: new construction and retrofitting. In “Options for Integrating PV into Your Building” Niels Wolter, Director of WisconSUN, noted that an advatage to shade screens is that they “can be retrofitted onto existing buildings or integrated into a new building’s design.”

This blog previously noted another PV material that can be used for retrofitting. Power Glass is a very thin semi-transparent coating or film. Xsunx has focused on patented processes, such as reel-to-reel manufacturing techniques and multi-terminal cell structure designs, in the hope of introducing such thin film flexible plastics into commercial architecture.

Still most solar installations are new construction and, generally speaking, installing a new BIPV system is usually less expensive than a retrofit. Wolter explains, “This is because the PV panels replace building materials such as roofing, thus avoiding the cost of those materials.”

BIPV systems offer many advantages compared to adding a PV system onto an existing building. BIPV systems:

• Require no additional support structures because they use the building’s frame
• Have limited additional construction expenses
• Are easily designed to provide daylighting, heat control, and other benefits
• Can be easily designed in an aesthetically appealing manner to maximize visibility or educational impacts.
• Can be financed as part of the entire building

Photo: Warren Gretz
A BIPV atrium can be an economical option. According to a study by Kiss and Company Architects in 1995, a BIPV atrium had a 70 percent shorter payback period than a BIPV facade. This is due primarily to the large material credit that reduces the PV atrium’s first cost. Wolter notes that “insulated PV tiles and slates may have good economics as well. They are relatively simple and inexpensive, prolong roof life, and reduce heating loads.”

There are several ways to integrate PV into a building’s design: Roofing, Facades, Atriums, and Shade screens. The latter cost less than other BIPV systems because extra ventilation of the PV modules is not needed. Shade screens may promising economic advantages because they reduce cooling loads and glare.

On the other hand, solar PV shading is unlikely to ever achieve the building zero energy on its own, since any solar system depends upon area to absorb energy. Yet such a requirement certainly complicates, if not contradicts, architectural considerations, such as the cost per area of the building. Architects achieve energy gains from “active” and “passive” design.

By paying attention to the building in the environment, sunlight already provides heat and lighting without the addition of any mechanical systems for power generation. Passive solar means using or capturing solar energy without any external power. “Passive”, in a sense, is an unfortunate moniker for such intent, since a great deal of activity goes into ensuring that a building achieves suitable, passive solar collection.

Alrobaei notes:

Facades offer a large area for PV modules. Besides generating electricity PV facades must look appealing and protect the building from weather. They can be integrated with windows, daylighting, and shading schemes to provide multiple benefits. However, vertically oriented PV panels at the latitude angle from – 35 deg to 35 deg. have much reduced electricity output compared to panels sloped toward the sun. The reduction is greatest in the summer when the sun is high in the sky; this is also when electricity is most valuable. To overcome this problem, facades can be sloped using a saw tooth design.

Commercial building can achieve energy, economic, and environmental performance. Such ‘high performance’ building not only saves money for the owners, but also can provide healthy places to live and work. Furthermore, it can help to preserve our natural resources and significantly reduce a building’s impact upon the environment. Especially with government incentives, there is a growing recognition by property managers as to the value of DER (Distributed Energy Resources. Thus, there are more demands placed upon architects and builders to lower building costs by means of solar power.