Advanced multifunctional energy efficient building facades
: experimental and computational characterisation of concentrating photovoltaic thermal evacuated glazing

  • Mohammad Ghoraishi

Student thesis: Doctoral Thesis

Abstract

The environmental restrictions on consuming fossil fuel energy indefinitely and the increasing need for energy in human society have created a necessity to improve energy efficiency in all sectors of demand including buildings. Consequently, research interest has been provoked to enhance the energy performance of building facades. This research investigates a multifunction and energy-efficient glazing system in which both electrical energy and thermal energy are collected from the glazing while providing thermal resistance and intelligent daylighting.

Innovations such as Vacuum Glazing (VG) with its characteristics related to high thermal resistance have been investigated solus or combined with other innovations in intelligent energy-efficient facades. The vacuum-included building facades aim to reduce heat transfer through the glazing and potentially add an extra energy-related function to the system. Vacuum water flow glazing, vacuum electrochromic glazing, vacuum Suspended Particle Device (SPD) glazing, vacuum Photovoltaic (PV) glazing, and evacuated flat plate solar collectors are examples of multifunction vacuum-included building fa├žades.

Photovoltaic/Thermal (PV/T) is an innovation in solar energy technology that while absorbing the wasted heat from the PV phenomenon of the PV cells aims to increase output electricity as well as harvest benign thermal energy. Also, Semi-Transparet Photovoltaic (STPV) facades in which PV cells are placed between glass pane layers were introduced and widely investigated to control daylight and solar heat gain, also, to generate small-scale electric energy from the large fenestrated surface in zero/low energy buildings. In this research, the integration of VG, PV/T, and Concentrating Photovoltaic Glazing (CoPVG), which is an STPV glazing concept, has been investigated in the aspect of energy performance.

This research introduces an enhanced version of the CoPVG device. The original CoPVG system was designed as a seasonal glazing, that concentrates sunlight onto the focus of the lens to exploit electricity generation during summer. Whilst, in winter, the system transmits light for indoor daylighting purposes. The newly developed version of the glazing, entitled Concentrating Photovoltaic/Thermal Evacuated Glazing (CoPVTEG) is a Semi-Transparent Photovoltaic/Thermal (STPV/T) glazing which is capable of simultaneously harvesting thermal energy and electricity. In addition, VG has been integrated into the device to enhance its thermal resistance providing a low U-value semi-transparent glazing.

In advance, an experiment was conducted to test the optical efficiency of the lenses of CoPVG concept. The experimental results were compared with an analytical model developed at Ulster University. As discovered that the model predicts the optical performance of the lenses reliably, the model is then used to create a visual representation of the glazing's annual optical performance, demonstrating how the glazing responds to changes in the sun's position in the sky throughout the year. As an example, the results indicate that utilising the lenses in glazing towards the south in Belfast leads to a shift in its performance from room lighting to shading on April 1st, and vice versa on September 15th. The analyses, also, showed that utilizing the CoPVG lenses can potentially enhance the electrical output power of the glazing ranging between 5% and 8% and from 46% up to 52% during winter and summer, respectively, when that is compared with traditional STPV glazing with the same opaque area percentage.

A finite element method was employed to simulate the glazing computationally, aiming to determine the interaction of the device with the vacuum gap. The developed model was validated by conducting experiments including fabricating a full-size prototype, designing and constructing an experimentation rig, and performing tests. Two different configurations were considered for simulation. The VG can be positioned in either an outward-facing manner, known as disposition A, or an inward-facing manner, known as disposition B. These dispositions were analysed computationally to determine the thermal and electrical output powers of the device in Belfast, UK. It was found that locating the VG inside, i.e., disposition B, potentially doubled the output electrical power compared to the other configuration, ranging from 63.32 W/m2 to 92.56 W/m2 and from 36.03 W/m2 to 43.88 W/m2 at noon throughout the year for disposition B and A, respectively. However, the thermal harvesting potential of disposition A is higher than disposition B. In this case, the device potentially generates from 216.46 W/m2 to 406.20 W/m2 thermal power at noon throughout the year. While the potential will be reduced from 163.54 W/m2 to 396.11 W/m2 in disposition B. Disposition A is more advantageous for cold-dominant climate zones while disposition B is the suggestion for a temperate climate zone similar to the studied case.
Date of AwardJul 2023
Original languageEnglish
SponsorsVice Chanchellor's Research Scholarship
SupervisorTrevor Hyde (Supervisor), Jayanta Mondol (Supervisor) & Aggelos Zacharopoulos (Supervisor)

Keywords

  • Concentrating photovoltaic glazing
  • BIPV
  • PVT
  • Vacuum glazing
  • Optical performance
  • CoPVTG
  • CoPVTEG

Cite this

'