Dual-Function Louvers for Energy-Efficient Daylighting in Existing Buildings

Objective

Evaluate the energy benefits of an innovative water-filled prismatic louver system that (a) redirects incoming sunlight for natural lighting benefits and reduction of artificial lighting needs; and (b) offers thermal insulation and thermal storage properties that harvest solar thermal energy, thus reducing heating and/or cooling needs.

Background

“Daylighting” refers to the introduction of natural light into buildings, and the active management of this light for efficient interior illumination.  Recently, there has been increasing interest in incorporating daylighting into the design of buildings in order to displace the need for high grade energy (electricity) used for interior lighting. In addition, daylighting strategies can lead to reduced energy consumption for heating, ventilation, and air-conditioning.  Moreover, increased daylight in buildings has been found to correlate with better employee and student productivity, and all-around health and well-being. Daylighting strategies, in short, play a vital role in the design and renovation of sustainable buildings.

This project will investigate and quantify the energy impact of an innovative daylighting strategy that exploits synergies among technologies in optics, materials, heat transfer, and architectural design. We will focus on a hybrid sun-shading system consisting of hollow prismatic louvers (blinds with horizontal slats) that are filled with water. The system’s optical transparency and dispersion and refraction properties enable it to redirect incoming sunlight so as to achieve both sun-shading and secondary indoor natural lighting. This provides physical and visual comfort for building inhabitants. Simultaneously, the proposed system harvests thermal energy. Water in the hollow prismatic blinds operates as a natural thermal insulation or storage medium, shielding building apertures from direct exposure to the prevailing weather conditions.  Hence, the system acts as a barrier for thermal loads in the summer, and potentially as a heat-exchange medium that will serve heating needs in winter.  If this system can be retrofitted into buildings with high amounts of glazing, it could simultaneously offer enhanced occupant comfort and health, as well as energy savings and the associated avoidance of green-house gas emissions.

Suggested Approaches

Note: An engineering Master’s Thesis student has installed the dual-function louver system in a CCNY lab, and has initiated measurement procedures. This capstone project will focus on a systematic evaluation of the system throughout the year, in different seasons and under different weather and daylight conditions. The capstone team will also investigate system control methods that minimize energy consumption and maximize occupant comfort. 

  • Phase 1:  Data collection for different seasonal conditions. 
  • Phase 2:  Analysis of data and re-evaluation of prism orientation.
  • Phase 3: Survey of occupant comfort and assessment of economic impact.  ​