Keywords:Building thermal design Air-conditioning Photovoltaic Off-grid Residential buildings should be places in which their occupants feel comfortable and content。 In an energy conscious world the challenge of offering improved indoor comfort is contrast with the desire to minimise grid energy consumption (both from an efficient distribution perspective and to minimise fossil fuel consumption) as well as the associated cost。 Occupant behaviour is one of the key drivers of energy consumption, and in particular peak energy consumption, which is largely the result of air- conditioner usage。 Selecting the most cost effective building designs or modifications that met these dual goals regardless of occupant behaviour is a non-trivial task。 One way of approaching this problem that guarantees no grid connected energy usage is to use an off-grid PV-battery driven air-conditioner。 Here we use a detailed simulation model to investigate the suitability of a small off-grid PV-battery system to power an air-conditioner to provide occupant comfort for a range of different building thermal designs across Australian climates。 The relative importance of different building parameters on the ability of the off-grid system to provide comfort is discussed。 Results show that even in tropical climates, there are certain building thermal designs that lead to indoor temperatures <25 ◦C at all times with a modest size PV-battery system。74109

1。 Introduction

The creation of a comfortable thermal environment in which occupants can live and work is fundamental aspect of a building’s function。 A building that the occupants find comfortable leads to numerous well established flow-on benefits, for example in terms of liveability, contentedness, productivity and health  [1,2]。

At the same time, in Australia as in many countries the energy required to condition buildings is substantial fraction of the total electricity generated, and rising energy costs and the concern for greenhouse gas emissions are driving an increasing focus toward design of low energy consumption buildings。 This is evidenced for example by the adoption of more stringent minimum energy effi- cient building standards in legislation  [3]。

An additional factor is the impact of peak electricity con- sumption events that in most locations are driven largely by vapour-compression air-conditioner usage, typically on  only  a few hot days of the year。 Meeting peak consumption demand contributes substantially to the overall electricity network cost with  end-consumers  who  don’t  use  air-conditioning    effectively

cross-subsidising those who do to an estimated present value of

$300 M–500 M dollars annually [4]。 While both overall and peak consumption have recently declined from a high in 2009, both are projected to recover and rise steadily in the period to 2018–19 [5]。 The recent reduction in overall electricity consumption (and continuing reduction in per capita consumption) can be attributed to various factors including increasing appliance energy efficiency [6,7], increasing retail prices [8], greater awareness of and con- cern for reducing energy consumption and, in particular, the rapid uptake of residential and commercial solar photovoltaics (PV) [5]。 However, although distributed PV has reduced total energy con- sumption, its impact on peak consumption has been much less evident。 In Australia increasing PV uptake has resulted in the peak summer demand shifting to later in the day since the peak in PV output occurs around the  middle  of  the  day。  This  has  resulted in a decrease in the ratio of  average  grid  electricity  consump- tion to peak consumption in all states except NSW where PV uptake has been lower [5]。 This highlights the fact that while PV output responds almost instantaneously to radiation loads, build- ing air-conditioning (cooling) requirement is governed firstly by occupancy, and secondly lags substantially behind solar radiation because of the building thermal mass and non-radiative component