Shedding Light on Photovoltaics
Photovoltaics convert light energy into electrical energy. The word “photovoltaic” is derived from photo, the Greek word for light, and volt, relating to electricity pioneer Alessandro Volta.
In 1954, Bell Labs in the U.S. introduced the first solar photovoltaic (PV) device that produced a useful amount of electricity, and by the late 1950s solar cells were being used in small-scale scientific and commercial applications, especially for the U.S. space program.
When PVs were first introduced into the marketplace back in the late 1970s they were very expensive, not very efficient and not for the average residential or commercial construction project. In recent years, PVs have seen a huge surge in popularity and integration into building designs. The cost per “peak watt” continues to decline as the efficiency of solar cells continues to improve and more firms are manufacturing PV panels. We’ve seen a new industry of local solar companies sprout up to meet the demand for design and installation services.
The graph below shows the cost of PVs in dollars per watt has fallen from more than $10 in 1998 to less than $6 in 2012.
The opportunity for building integrated photovoltaics (BIPV) looks extremely promising. BIPV is set to become one of the fastest-growing segments in the solar industry with up to 4.6 GW of installations forecast through 2017. Pike Research sees BIPV as one of the fastest growing solar markets.
BIPV utilize the PV panels as part of the envelope of the building. Instead of installing PV panels to existing roof or wall areas, with BIPV, the panels are the roof or wall. This reduces the net cost of the PV system by deducting for the cost of the glass, spandrel panel or skylight that is being replaced. Building Applied Photovoltaics (BAPV) do not have this benefit.
The graphic below shows that BIPV/BAPV revenues have the potential to grow from about $600 million in 2012 to $2.5 billion in just five years.
BIPV installations require coordination among several entities. The general contractor, glazing contractor, electrical contractor, aluminum framing manufacturer, PV panel manufacturer and solar energy consultant must all understand what is required and who is responsible for each portion of work. This includes:
• Who will install the PV panels in the glazing system?
• How will the electrician wire the PV panels as they are installed?
• Will wiring be routed within the framing system? Will the framing system need to be modified to accept the wiring?
• Do the bidding documents clearly define who will bid what portion of the work?
The diagram below shows how PV panels were installed in the Tiger Woods Learning Center in California. The curtainwall was fabricated with access holes in the tongues to allow for the wring to be run down the mullion.
How cost effective BIPVs can be depends on several factors, such as:
• Anticipated amount of sunlight at the building site. Is there the potential for shading from other buildings or trees? Some areas of the U.S. get much more sunlight than others. By the way, PVs work with sunlight, not solar heat. A cold climate has no adverse affect on the performance of the solar cells. In fact, a bright, clear, cold winter day will show improved performance over a hot summer day.
(The map below shows the potential for PV performance across the country.)
• Are the panels facing due south for maximum efficiency?
• Are the panels on a slope or are they in a vertical wall. Tilted panels will perform better.
• How much was saved by eliminating other building fenestration products and replacing them with PVs?
• Is “net metering” allowed? This allows the building owner to sell back to the utility any excess solar energy being generated. In some cases, you can literally watch the electric meter spin backward!
• Are their local and/or state tax incentives or grants? (This site has a wealth of information on renewable energy financial incentives: www.dsireusa.org)
• Is their special financing available?
• Does the electrical utility provide any funding or rebates? Some utilities are willing to help fund PV installations in return for them getting Renewable Energy Credits (RECs) for the installation. These RECs can be used by the utility to show that they are generating a certain portion of their power from renewable energy.
Many times, it’s not just the “payback” that interests building owners to opt for BIPV. What’s the return on investment? Most solar PVs will last 25 years or more. How much will electricity cost in 2020, just eight years away? Is depreciation allowed on the installation?
Sometimes, in the end, building owners simply see this as the right thing to do for them and the environment by generating non-polluting, renewable, made in the U.S., domestic energy.