Modelling the Energy Contributions of a PVT System to a Low Energy

House in Sydney

S. Bambrook* and A. Sproul

School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052.

NSW, Australia

* Corresponding Author, s. bambrook@student. unsw. edu. au

Abstract

A hybrid photovoltaic/thermal (PVT) air system integrated into a low energy residential house in Sydney is modelled. The thermal and electrical energy contribution of the PVT system to the house is examined to investigate the suitability of these systems in appropriately designed houses to eliminate the need for space heating systems, reducing household energy consumption and greenhouse gas emissions, and decreasing the peak load on the electricity grid. Simple heating degree day calculations showed that the PVT heating energy was slightly in excess of the monthly winter heating demand of the house and more detailed simulation results showed that PVT systems can provide an acceptable indoor temperature in winter in well insulated Sydney houses.

Keywords: Photovoltaic/thermal, PVT, modelling, building simulation.

1. Introduction

Sydney has a temperate climate with warm, humid summers and mild winters. Surprisingly,

Sydney is predominately a heating climate with significantly more heating degree days than cooling degree days. In Australia, 42% of household energy consumption is attributed to space heating and 2% is attributed to space cooling [1]. While only a small proportion of the space heating uses electricity as the fuel source, there are still significant greenhouse gas emissions resulting from the use of other fuels such as natural gas and liquid petroleum gas. A corresponding increase in the peak electricity demand requires significant expenditure on upgrading the electricity distribution network to cope with this peak demand.

To address these problems a holistic approach to energy efficient residential house design and implementation of a PVT air system is proposed. A well insulated house with passive solar design would have a much lower heating and cooling demand than the average Australian house. The silicon photovoltaic (PV) system is mechanically ventilated to lower the cell operating temperature in order to improve the efficiency and provide a higher power output. The waste heat energy can be used to heat the house in winter. This work aims to investigate the practical feasibility of a PVT system for meeting the winter heating requirement of the house.

The majority of research work to date on PVT air systems has focused on analysing the PVT system itself and examining performance improvements. Charalambous et al [2] provided a comprehensive review of various PVT collector types with particular emphasis on the parameters affecting PVT performance.

This work has a focus on the overall system, examining the effect of integrating a PVT system into a building. The Swiss AERNI factory building features one of the early PVT air system

installations. In this system the photovoltaic modules are ventilated and thermal energy is used directly in the building in winter and stored in earth storage during summer [3]. Lloret et al [4] conducted a case study of a PVT system integrated into the Mataro Library in Spain. The hybrid PVT air modules forming the facade wall and roof mounted array provide heated air which is used as an input to the gas heating system in winter and, in summer, the warm air is ventilated to the outside of the building. Cartmell et al [5] reported on the simulation and initial monitoring results from a combined ventilated PV and solar thermal air system installed at the Brockshill Environment Centre in the United Kingdom. Simulations used ESP-r to generate the hourly load requirements for the various zones within the building and this output was then used in the TRNSYS simulation to determine the contribution of the ventilated PV and solar air systems towards meeting the heating demand of the building. TRNSYS simulations were used by Bakker et al [6] to show that a PVT water system coupled with a ground source heat pump could meet the heating and most of the electricity demand of a single family house in the Netherlands.

This work represents the first steps in analysing the energy contribution of a PVT system integrated into a Sydney house in order to eliminate the need for space heating. The analysis focused on using building energy simulation programs to determine the energy requirement of the house and the expected thermal and electrical output of the PVT system. For initial calculation and comparison the heating degree day (HDD) method was also used.

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