GLUMAC - Engineers for a sustainable future

David Summers, P.E., LEED^®AP, Los Angeles Associate Principal

The term Building Integrated Photovoltaics (BIPV) refers to any technology that integrates PV cells into a building component.

Crystalline silicon cells have been used in BIPV applications such as roof tiles and glazing. The cells have the "solar cell look" and have a significant impact on the building™s aesthetic appearance. Nevertheless, crystalline panels can often be integrated into the building facade, and they also make excellent shading devices such as window overhangs or parking lot covers.

With the development of thin-film technology, the opportunities for BIPV applications have grown due to the seamless integration with the architectural aesthetic. The film can be applied to roofing and siding materials as well as windows and skylights. When applied to a glass surface, the film can be perforated with a laser to achieve the desired light transmission.

One advantage of using BIPVs is that the first cost of the solar cells is partially offset by the avoided cost of the replaced building component. For example, if a PV array is used as a mechanical equipment screen, the cost of a traditional screen is avoided.

With BIPV applications, it is especially important to remember that all PV technologies are sensitive to even partial shading of the cells. Both crystalline and thin-film cells should be applied in locations that will not be shaded by adjacent buildings, landscaping, or other obstructions. In applications where some shade cannot be avoided, technologies such as bypass diode are available to somewhat reduce the negative impacts.

For custom-made BIPV units, a UL listing must be obtained as part of the project cost.

ECONOMIC ANALYSIS

Photovoltaics are recently becoming more economically feasible due to the following factors:

• Continuing advances in cell manufacturing technology.
• Government and utility rebates and incentives.
• Rising electricity costs.

Rebates and Incentives for PV Systems in California

California Solar Initiative. The State of California will fund the up-front costs of a solar PV installation through the Self-Generation Incentive Program (SGIP). The program is administered through the following utility companies:

• Southern California Edison (SCE)
• Pacific Gas & Electric (PG&E)
• San Diego Gas & Electric (SDG&E)

To be eligible for the SGIP, the building must be served by one of these three utilities. The current incentive amount is $2.50/watt to purchase and install the system, if funds are available. The installation must be greater than 30 kW, and the incentive is capped at 1 MW.

For systems less than 100kW, the SGIP incentive is paid in a lump sum based on expected electricity generation. For larger systems, the incentive is paid monthly over a period of five years based on actual metered electricity generation.

Los Angeles DWP. The Los Angeles DWP™s Commercial Solar Power Incentive will rebate $0.04/kWh for installations above 30kW. An additional $0.01/kWh is available for BIPV systems. The incentive is based on the total calculated energy (kWh) produced over the expected 20-year system life. The LA DWP incentive program results in a rebate that is roughly 40-60% of the SGIP incentive if the project were located in SCE territory.

Other Utilities. Other utilities, such as those serving Pasadena, Glendale, Burbank, Sacramento and Silicon Valley, have their own incentive programs. More information is available at www.californiasolarcenter.org/incentives.html

Federal Energy Policy Act (EPAct) Tax Credit. The federal government offers a 30% tax credit on solar energy systems. Federal tax credits may be subject to state tax, and utility incentives may be subject to federal tax. Consult a professional tax advisor for more information. Additional guidance is available in the SEIA Guide to Federal Tax Incentives for Solar Energy, published by the Solar Energy Industries Association (available for download at http://www.seia.org/). Updates are also posted at www.energy.gov/taxbreaks.htm

Electricity Rates in California

For California commercial customers, average electricity rates have fluctuated between 0.12 - 0.15/kWh over the last five years (Source: www.cpuc.ca.gov). The longer historical trend shows that rates have increased an average of 6.7% over the 30-year period from 1970-2000 as shown in the graph below (Source: CPUC "Electric Rate Compendium" 2001). These figures include energy, peak usage, and other charges combined.

Current commercial rates are currently around $0.15/kWh. The actual electricity costs vary depending on a customer™s rate schedule and usage patterns.

Estimated Costs and Paybacks of PV Systems in California

The cost and payback period of a photovoltaic system will vary depending on several factors:

• Type of PV cells
• Size of system
• Whether the PV cells avoid the cost of another building component (BIPV)
• Rebates or incentives
• Electricity rates
• Local market conditions for materials and labor

The cost examples below are based on Glumac™s research and experience across a broad range of projects.

Example 1: 200 kW Polycrystalline Array. This hypothetical example is for 200 kW, 20,000 sf polycrystalline silicon PV array. The installation is in SCE, PG&E, or SDG&E territory. The estimated cost break down is as follows:

The estimated electricity production and payback period for this array would be as follows (Source: www.ladwp.com, link to Solar Incentives and PVWatts version 2).

The above values assume a DC-to-AC derate factor of 0.77 and an average electricity rate of $0.15/kWh.

Example 2: 200 kW Polycrystalline BIPV. This hypothetical example is the same as the previous example, with the exception that the PV panels replace a building component. The avoided cost of the component is assumed to be $15/sf. The estimated cost break down is as follows:

The replaced building component is typically a horizontal or vertical surface, so the calculation for 34° fixed angle is not included. The estimated payback period for this array would be as follows:

As shown above, the avoided cost of replaced building components has a significant impact on the economic feasibility of PV systems. If the avoided cost were higher, the payback period of the PV system would be shorter.

Example 3: 200 kW Polycrystalline BIPV in LA DWP territory. This hypothetical example is the same as the previous example, with the exception that the incentives are based on the LA DWP program. To simplify the analysis, the calculation is presented for the fixed horizontal case only. The estimated cost break down is as follows:

The estimated payback period for this array would be as follows:

Conclusion

The economic feasibility of photovoltaic systems is significantly improved by the avoided cost of another building component such as a facade, overhang, or equipment screen. The more expensive the building component would have been, the better the payback of the photovoltaic system will be. The potential for building integrated photovoltaics is in finding opportunities for avoiding the cost of other expensive building components.