Product

Solar Energy Harvesting Systems

Prototype Systems

Modular BIPV/T

By Efstratios Rounis, Concordia University, Canada

Product Description

Brief Concept Description

The Modular BIPV/T system allows the full integration of a photovoltaic/thermal system into the building envelope maintaining the potential of modular/unitized fabrication. The design of a typical curtain wall is here altered, so that an air channel is created between the PV layer and the insulated back surface and it is possible to cool down the PV layer collecting useful heat. In this case, multiple fresh air intakes can be used to boost the thermal performance of the system. The modular BIPV/T system can be applied to the opaque part of curtain wall facades, but is also suited for roof applications, as shown below.

A prototype of this system was developed at Concordia University in collaboration with Unicel Architectural and Canadian Solar (Figure 29, left) and a variant of such prototype was incorporated as a roof BIPV/T system in the Solar Decathlon House designed by TeamMTL for the event in China 2018 (Figure 29, right).


Figure 29. Architectural integration of BIPV/T in a curtain wall design on the left and example of the integration of the BIPV/T module in a roof (Solar Decathlon House, China 2018) on the right.

Architectural and Technological Integration into the Envelope

This system is designed for full façade/roof integration as it replaces traditional envelope elements. It can be either incorporated as stick-built (assembled on-site) or it can be prefabricated in modular form. The PV panels are supported by pressure plates, point supports on a metal frame and an air gap is left to separate them from the rear surface. The layers on the back of the PV panels guarantee air and water tightness as well as thermal insulation. Figure 30 shows the cross section of the experimental BIPV/T curtain wall. 

Integration into the Building: System and Comfort

Depending on the application and the outlet air temperature, the system can either deliver pre-heated fresh air either directly to the living space or convey it to a heating system (i.e. a heat pump) that works at a high COP levels, with a consequent reduction of the cost for space heating


Figure 30. Cross section of the BIPV/T curtain wall system.

SWOT Analysis

Strengths

  • Full building integration of the BIPV/T system: the PV panels are seamlessly integrated into façade or roof with a superior architectural result replacing traditional envelope elements
  • Design flexibility: PV modules of different typologies and sizes can be integrated
  • Both electric and thermal energy is generated by the building’s envelope
  • Water- and airtightness as well as thermal insulation requirements are fulfilled by the BIPV/T module
  • There is potential for modular fabrication and factory-controlled construction and testing
  • The construction technique is simple and suited to the existing building practices

Weaknesses

  • The electric wiring must be adapted: custom junction boxes may be required
  • External shading can limit the performance of the system, especially for façade applications
  • The orientation of the installation is critical, especially for the thermal output
  • A good level of communication is required between PV module manufacturer and frame manufacturer
  • The use of a fan is required. The optimization of the air flow in collector and manifold is then needed
  • The heat collected can be used only in low temperature applications

 
Opportunity

  • The solution could be standardized and introduced as building practice in the architectural and engineering community.
  • Institutional buildings can be used as showcases to prove the technology and spread awareness 

 
Threats

  • The lack of significant government incentives and the low electricity prices reduce the cost-savings for costumers
  • Architects may find difficult to incorporate new building techniques to the established ones

Lessons Learned

  • The architectural result can be aesthetically pleasing, and the PV panels seamlessly integrated with the rest of the building (Team MTL, Solar Decathlon, China 2018).
  • The curtain wall approach facilitates the implementation of skylights (daylighting), as well as thermal collectors (thermal boost) in series with the BIPV/T system.
  • The construction sequence including wiring, grounding and material placement need to be carefully planned, especially in the case of stick-built approach (on-site assembly).
  • The structural integration of the system needs to be considered in the early design stages of the building.
  • The water and air tightness of the rear surface of the channel need to be ensured to guarantee the building envelope continuity.
  • The BIPV/T operation and how it is coupled with the HVAC depend on the local climate. An early stage analysis is to be carried out to investigate optimal operation and sizing, depending on the intended use. In the same way, the manifold location, duct sizing and connections with the BIPV/T channels need to be addressed in the early design phases.
  • The orientation of the installation (tilt, slope) is critical for the performance of the system. Restrictions from the building codes (maximum height) can affect the system performance.
  • The collaboration between PV industry and building envelope manufacturers is essential for the development of standardized products that can be accepted and adopted by the constructions community.