Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

Bitsuamlak, Girma

2nd Supervisor

Tariku, Fitsum

Affiliation

British Columbia Institute of Technology

Co-Supervisor

Abstract

A direct exchange building integrated photovoltaic and thermal (BIPV/T) heat pump system is proposed where the heat extracted from the BIPV is used to drive the heat pump. To ensure a more stable diurnal system performance, especially at low solar conditions, air flow is instituted in the cavity between BIPV façade and the insulated inner wall. The airflow is directed from the heated or cooled space into the air channel and can be exhausted or returned to the space depending on the building operating conditions. The flow and geometrical parameters of the BIPV/T façade are optimized such that more than 40% of the peak performance is recovered by the airflow in the channel off-peak conditions. Also, BIPV façade surface temperature is reduced by up to 10°C compared to air based BIPV/T and the wall heat gain is reduced by up to 46%. A case study scenario is considered where the BIPV/T heat pump system is installed as supplemental heating for an electric water heater and the annual energy saving is quantified. A surrogate model of the BIPV/T heat pump system is developed and implemented in EnergyPlus. The annual energy analysis suggests the Domestic hot water (DHW) heating energy demand was reduced by up to 40.4% for a wall integrated system and 44.2% for a roof integrated system.

Summary for Lay Audience

The building sector is responsible for a considerable amount of energy use largely due to the space heating requirements. Of course, this translates to significant green house gas emissions. To curb this, several passive techniques have been introduced, of which the most common is the increasing the Insulation in the walls. However, there is the diminishing returns of adding more insulation. Beyond an optimum insulation level, the cost outweighs the heat loss reduction. A more sustainable approach is to incorporate renewable technology like photovoltaics in buildings in an integrated fashion such that the cladding is substituted with PV modules. This improves the cost effectiveness of integrating renewable technology in buildings in that the PV cells perform multiple functions. However, by integrating PV cells, in the building envelope there is potential to overheat since typical PV efficiencies are less than 20%. As such, 80% of the solar energy is converted to waste heat that can increase the temperatures. To maintain appropriate operational temperatures a thermal management system is proposed to extract the waste heat and utilize it for other domestic purposes like space heated, domestic water heating, etc. The potential of the system is investigated, and the energy savings quantified for a system that utilizes the waste heat for DHW. The findings suggest that the combined electrical and thermal energy extracted can offset at least 44.2% of the hot water energy demand depending on the climate and orientation of the building integrated photovoltaic concept.

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