W. Saman1*, E. Halawa2, M. Krause3

1,2Sustainable Energy Centre — University of South Australia, Mawson Lakes SA 5095 — Adelaide, Australia
3Fraunhofer-Institute for Building Physics Project Group, Kassel

* Corresponding Author, Wasim. Saman@unisa. edu. au
Abstract

This paper discusses the application of an integrated thermal system for the provision of hot water, space heating and cooling in residential houses in Australia. The proposed system consists of a solar combisystem with the addition of a solar liquid desiccant sub-system to provide cooling and dehumidification. A two storey energy efficient house exposed to the weather data of Adelaide, Brisbane and Sydney is modelled to calculate the hot water, space heating and cooling loads. The results demonstrate the suitability of the integrated solar dehumidification/cooling and hot water systems for locations of medium/high humidity.

Keywords: integrated thermal system, solar cooling, dehumidification, liquid desiccant air conditioning

1. Introduction

The energy demand for air conditioning of both commercial and residential buildings has been escalating throughout the last decades. In Australia, space heating and cooling represents about 40% and domestic water heating about 30% of the energy demand of residential buildings [1]. Solar water heating is a well-established technology. In Australia more market penetration of this technology is expected due to improved public environmental awareness and government’s financial inducements [2]. Solar space heating systems, on the other hand, have not gained market acceptance due mainly to high initial cost. In addition, only a small amount of total annual heat collected by the system is eventually utilised due to the short heating season in most Australian population concentrations. Due to the absence of more viable systems in the market, consumers resort to reverse cycle air conditioning systems which provide both cooling and heating. With low initial costs, these systems are dominating the air conditioning markets, particularly in new housing. This, however, has resulted in dramatic increases in energy use and summer peak power demand with associated electricity generation and distribution requirements.

The use of solarcombisystems for the provision of heating and hot water has expanded in many European countries. However, in temperate climates such as Australia, this application cannot be economically justified due to the short heating period provided. Most Australian cities require cooling as well as heating. The paper investigates the feasibility of an integrated solar system which includes dehumidification/cooling.

Monitoring results in a new housing development in Adelaide has shown that on a hot summer day, up to 90% of the summer peak demand is due to domestic air conditioning [3]. Thermally driven cooling systems utilising solar energy is a promising option. Seasonal match between solar radiation availability and the building cooling load supports this argument. Solar liquid desiccant

air conditioning which provides both cooling and dehumidification has been found to be technically viable [4-6]. Numerical studies on the existing solar hot water systems revealed that despite the all year round demand for hot water, the “oversizing” of solar hot water system seems inevitable due to the need to adequately cover the winter peak hot water demand. A system which integrates the provision of heating, hot water, cooling and dehumidification is a logical approach to optimise the system’s overall effectiveness and at the same time minimise the system’s cost.

The paper reports on a study to advance this concept and to use current solar cooling and solar water heating technologies to provide heat for space heating and cooling as well as domestic hot water. The system under investigation consists of solar collectors and a storage tank, a desiccant cooling unit and an indirect evaporative cooler providing hot water, space heating and cooling all year round for a two storey home exposed to typical year weather data of Adelaide, Brisbane and Sydney, Australia. The purpose of the study was to assess the technical viability of this integrated system.