Making Roofs More Functional with BIPV-T Systems 2

Wednesday, July 2nd, 2014
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The days of underutilised, single-purpose roofs appear to be fading. New roof technology can provide shelter, electricity, and heat from a single roofing system.

Called a building integrated photovoltaic-thermal (BIPV-T) system, the new technology integrates painted standing-seam steel roof panels with thin-film photovoltaic panels and makes use of the sealed chamber between them for thermal energy.

BlueScope Steel and the Australian Renewable Energy Agency (ARENA) have recently installed Australia’s first prototype BIPV-T system at a home in Glebe. ARENA CEO Ivor Frischknecht said the roofing system was designed specifically for Australia’s climate and building environments to ensure the PV systems were durable and robust. The companies are developing the systems for commercial sales.

“In addition to PV panels, an innovative thermal duct system warms and cools air to supplement air conditioning in the homes,” Frischknecht said. “These first installations are an important step as the technology moves towards commercialisation and cost competitiveness with conventional rooftop PV.”

The groups expect to continue to develop the prototype systems to lower system costs for labour and materials and make them cost competitive with PV systems. In addition, they are working to advance inverters, the electronic units that convert direct current produced by the PV panels into alternating current useable by home appliances and the electric grid.

Typical commercially available PV modules are not especially efficient at turning solar radiation into electrical energy, though researchers and manufacturers are making great strides. In late 2013, for example, an encapsulated thin-film unit from Avancis achieved 16.65 per cent efficiency, as verified by the U.S. National Renewable Energy Laboratory. Other types of PV units can do better, but PV modules commonly have efficiency levels of six to 18 per cent.

The remainder of the energy is lost as reflection or as heat. Removing some of that “waste” heat can increase the efficiency of the PV module. Rather than letting that heat escape into the air, researchers have employed the BIPV-T system to produce both electrical and thermal energy from one roof system.

On each roof panel, the thin-film photovoltaic fills the gap between the standing seams of the roof, creating a sealed channel for air movement. As the air heats up, it can be pumped into the house for heating use, and also pumped back out of the house.

The concept for the integrated photovoltaic-thermal system is not new; it was studied as far back as the 1970s and 1980s. More recently, the authors of the report Performance of A Building Integrated Photovoltaic/Thermal (BIPVT) Solar Collector undertook a study to examine an experimental BIPV-T system, with results validated “with experimental data from testing on a prototype BIPVT collector.”

The authors noted that solar thermal systems have been more widely adopted than PV systems.

“The solar thermal collector market in Australia and New Zealand was growing at a rate of 19% per annum,” the authors said.

PV systems, though not as prevalent, “could provide greater opportunity for the use of renewable solar energy technologies.”

In addition, the authors concluded, BIPV-T systems can can be made of lower cost materials without sacrificing efficiency, such as by using pre-coated steel for roof panels. Finally, the authors noted the potential for lower costs associated with integrating a BIPV-T system into a building, instead of adding it on to the top.

This $5 million roof system project was developed by BlueScope with $2.3 million in funding from ARENA. On June 19, the federal government introduced legislation repealing the 2011 Australian Renewable Energy Act and effectively scrapping the agency. Currently, the agency counts about 180 projects under way, worth more than $1 billion. Those projects have funding agreements in place and will proceed, according to ARENA, as the agency is absorbed into the Department of Industry. Shuttering ARENA will save about $1.3 billion over five years.

A government spokesman said the budget needed savings to get back on track, but the government remained committed to renewable energy projects, and “is now keen to see outcomes from these projects.”

Rich Bowden, blogging at SolarQuotes, noted that the final vote is not yet in, however.

“As those who have followed the twists and turns of the Australian political scene in recent times know, the Abbott government does not have the numbers in the Senate,” he wrote.

Frischknecht emphasized in a speech that ARENA makes commercially rigorous investments and uses a “commercial readiness index” to choose projects that will be commercially successful.

“This rigorous approach ensures we select only the projects that will deliver the affordable renewable energy technologies that can help make Australia’s future energy supply mix diverse, flexible, reliable and secure,” he said.

One of those projects is Vast Solar’s pilot 1.1-megawatt concentrating solar thermal plant, for which construction recently began near Forbes, NSW. Andrew Want, CEO of Vast Solar, said ARENA’s involvement in the project was crucial.

“We could not have achieved these advances without the strong support of the Australian Renewable Energy Agency, working alongside our private investors, over the past three years,” he said.

Without ARENA’s investment, he noted, the company company would have been forced to pursue funds offshore.

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  1. Lawrence Crushing

    These are a step in the right direction. According to the next generation of buildings are going to come with photovoltaics built into the home. Is there a siding application for the same system?

    • Steve

      I haven't seen PV siding, maybe because during the warm months, it's best to keep the sun off the walls with generous roof overhangs.