Building Integrated Photovoltaics (BIPV) shall be defined as a photovoltaic power generation component that is an integral part of a permanent building structure and, in its absence, would require non-BIPV building materials or components to replace it. The power generation performance of BIPV modules is considered secondary to their role as building materials or structural components. BIPV occupies a space in the architectural design and if removed from that space, its absence would be evident and noticeable. In this section, this issue of Millennial Solar will introduce you to the design of building-integrated photovoltaics.

Steps to Design a BIPV System

BIPV systems should adopt energy-saving design techniques and carefully select and specify equipment and systems. They should be viewed from a life cycle cost perspective, not just the initial first cost, as the total cost may be reduced by the avoided costs of construction materials and labor they replace. Design considerations for a BIPV system must include the building's use and electrical loads, its location and orientation, appropriate building and safety codes, and associated utility issues and costs.

1. Carefully consider applying energy-efficient design practices and energy-saving measures to reduce a building’s energy needs. This will improve comfort and save money, while also enabling a given BIPV system to provide a greater percentage contribution to the load.

2. Choose between utility-interactive PV systems and stand-alone PV systems:

(1) The vast majority of BIPV systems will be connected to the utility grid, using the grid as storage and backup. The system should be sized to meet the owner's goals - often defined by budget or space constraints; and, the inverter selection must understand the utility's requirements.

(2) For those "stand-alone" systems powered solely by PV, the system (including storage) must be sized to meet the building's peak demand/minimum power production projections. To avoid oversizing a PV/PV cell system due to abnormal or occasional peak loads, backup generators are often used. Such systems are sometimes referred to as "photovoltaic hybrids."

3. Peak shifting: If peak building loads do not match the peak power output of the PV array, it may be economically appropriate to incorporate PV cells into some grid-tied systems to offset the most expensive periods of electricity demand. The system can also act as an uninterruptible power supply system (UPS).

4. Provide adequate ventilation: Increased operating temperature will reduce photovoltaic conversion efficiency. Crystalline silicon photovoltaic cells are more realistic than amorphous silicon thin films. To increase conversion efficiency, please allow proper ventilation behind the module for heat dissipation.

5. Evaluation using hybrid photovoltaic-solar thermal systems: As an option to optimize system efficiency, designers can choose to capture and utilize the solar thermal resources developed through heating modules. 

6. Consider integrating daylighting and photovoltaic collection: Using translucent film modules, or crystal modules with custom spacer units between two layers of glass, designers can use PV to create unique daylighting features in facade, roof or skylight photovoltaic systems . BIPV elements also help reduce unnecessary cooling loads and glare associated with large areas of architectural glass.

7. Integrating photovoltaic modules into shading devices: Photovoltaic arrays are envisioned as “eyebrows” or awnings of the building’s glazed areas that can provide appropriate passive shading. When awnings are considered part of an integrated design approach, chiller capacity is typically smaller and perimeter cooling distribution is reduced or even eliminated.

8. Design for local climate and environment: Designers should understand the impact of climate and environment on array output. Cold, sunny days increase power generation, while hot, cloudy days reduce array output;

(1) Reflecting light onto a surface (e.g., snow) on the array will increase the array output;

(2) The array must be designed for potential snow load and wind load conditions;

(3) A correctly angled array will reduce snow loads relatively quickly

(4) Arrays in dry, dusty environments or environments with heavy industrial or traffic (automotive, aviation) contamination will require cleaning to limit efficiency losses.

9. Address site planning and positioning issues: Early in the design phase, make sure your solar array will receive maximum sunlight exposure and will not be obscured by site obstructions such as nearby buildings or trees. Of particular importance is the fact that during the peak solar collection period, which consists of the three hours either side of solar noon, the system is completely free of shadows. The impact of shading on a photovoltaic array is much greater than the impact of the shadow's footprint on electrical harvesting.

10. Consider array orientation: Different array orientations can have a significant impact on the annual energy output of the system, with tilted arrays producing 50%-70% more power than vertical facades.

11. Reduce building envelope and other site loads: Minimize the load on the BIPV system. Use daylighting, energy-saving motors and other peak reduction strategies wherever possible.

Professionals: The use of BIPV is relatively new. Ensure that the design, installation and maintenance professionals involved in the project are appropriately trained, licensed, certified and experienced in working on PV systems.

E-mail: market@millennialsolar.com

Current Continuity Testing System

Current Continuity Testing System is specially designed for the 10.11 high and low temperature cycle test clauses and 10.12 humidity and freezing test clauses in the IEC61215 standard. It mainly includes providing stable DC power, current recording, temperature recording and temperature control functions. Through temperature control of the DC power supply, it can monitor multiple currents and temperatures in real time for a long time. Used in conjunction with the high and low temperature cycle box, it can monitor the internal circuit continuity of multiple photovoltaic modules. Determine the fatigue resistance of the material, the rationality of the lamination process, and the stability of the welding quality of the solar cell module in high and low temperature alternating environments.

E-mail: market@millennialsolar.com

BIPV systems can be designed to integrate with traditional building materials and designs, or they can be used to create high-tech, future-proof looks. Millennial Solar believes that the future application and development of BIPV will be broader.