Abstract
Innovative mechanical services coupled with renewable energy systems are crucial for achieving a net zero energy goal for houses. Conventional systems tend to be vastly oversized because they lack the means to buffer energy flows and are based on peak loads. This paper presents an approach to achieve a net zero energy goal for houses by using a solar PV system, heat pumps, and thermal and electrical storage batteries, all off-the-shelf. Constraining one part of the system and then showing how to manage energy storage and flow is a paradigm shift in sizing. The design is for a modest-sized house built in Melbourne, Australia. The output of a solar photovoltaic array drives a small-scale heat pump to heat water, buffering its energy in a thermal battery to energise a radiant space heating system. Space cooling is provided by a separate heat pump. Through energy storage in electrical and thermal batteries, it is possible to meet the electricity, heating and cooling needs of the house for the Melbourne climate with a heat pump that draws less than 1 kW. The design methodology is detailed in an appendix and can be applied to similar projects. This paper contributes to similar work worldwide that aims to reinforce innovative renewable energy driven service design.
Highlights
Over the last decade, research on the self-consumption of photovoltaic electricity within residential buildings has become a significant topic [1,2,3,4,5]
On the coldest days in winter, an average of 5 kW of heating is supplied between 6 and 8 am and between 6 and 10 p.m.—a total of six hours, leading to a requirement of 30 kWh of heating. This is the design heating load (DHL) for the system. Two questions at this point are: can this DHL be met within the constraints of a heat pump operating with less than 1 kW of power and a 6.5 kW solar PV system; and, if so, what other components of the system are required?
This study proposed that cooling be delivered directly via a conventional heat pump (HP) split-system, a case could be made for thermal storage for cooling, with another water loop circulated partly through the piping used for the hydronic heating system
Summary
Research on the self-consumption of photovoltaic electricity within residential buildings has become a significant topic [1,2,3,4,5]. While Stauffer et al do not go into great detail about their service system design, they provide a detailed theoretical explanation of a calculation for a self-consumption ratio [1]. Sánchez et al show a more detailed service system without a battery, but they select a 1 kW input heat pump to provide for increased PV self-consumption [2]. In their papers on the topic, do not explain the mechanical services but rather deal with battery sizing and theoretical algorithms to predict the optimization of self-consumption [3,4]. Luthander et al provide a review on self-consumption which deals more with PV and battery sizing. While the types of heat pumps applied to these purposes require further understanding and investigation, they do increase self-consumption through thermal storage
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