Abstract
This paper analyzes the optimal sizing of a particular solution for renewable energy residential building integration. The solution combines a photovoltaic (PV) plant with a heat pump (HP). The idea is to develop a system that permits the maximum level of self-consumption of renewable energy generated by using a small-scale solar array installed on the same building. The problem is analyzed using data obtained from an experimental system installed in a building in Pisa, Italy. The residential house was equipped with a PV plant (about 3.7 kW of peak power), assisting a HP of similar electrical power (3.8 kW). The system was monitored for eight years of continuous operation. With reference to the data acquired from the long-term experimental analysis and considering a more general perspective, we discuss criteria and guidelines for the design of such a system. We focus on the possibility of exporting energy to the electrical grid, from the perspective of obtaining self-consumption schemes. Considering that one of the problems with small-scale PV plants is represented by the bidirectional energy flows from and to the grid, possible alternative solutions for the design are outlined, with both a size reduction in the plant and utilization of a storage system considered. Different design objectives are considered in the analysis.
Highlights
During the last decade, the development of intermittent renewable energy systems (RES)—mainly photovoltaic (PV) systems—and increasingly decentralized production have been observed in many countries
One solution considered in various cases as fundamental to the concept of net zero-energy building (nZEB) is the solar-assisted heat pump, consisting of a HP system assisted by a PV plant installed on the building
The nominal power of the PV plant can be considered as about 70% of the peak power of the ground heat pump (GHP) to reduce the amount of energy exported to the grid, without increasing the energy imported from the grid
Summary
The development of intermittent renewable energy systems (RES)—mainly photovoltaic (PV) systems—and increasingly decentralized production have been observed in many countries. The promotion of integrated solutions of solar-assisted heat pumps (both the air type and the geothermal type) and a PV plant to support a system producing electricity to supply the HP can, in principle, add “flexibility” to the system In this case, a relevant problem is represented by the bidirectional energy flows of the external power grid, due to the electricity exported to the grid from a renewable-based system and the electricity imported from the grid depending on the electricity demand of a building. During summertime, heat pumps typically contribute to an increase in the flexibility of the system, as they can consume electricity during hours of excess production, while they can be effective during the winter For this reason, it is important to consider the possible connection between the production of electricity and use of thermal energy, as obtained in the case of integrated PV and HP systems for building services [11,12]. This will support further increases in RES while avoiding state interventions, which are often designed in an uncoordinated manner and have led to increasing distortions of the wholesale electricity market, with negative consequences for investors
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