18 May 2017
Grid-connected photovoltaic (PV) power plants may lead to unwanted disturbance to the electricity grid. In addition, low feed-in tariffs motivate a homeowner and operator of the PV plant to maximize the electricity self-consumption. Thermal storage capacity enables to maximize the utilization of PV-power to pre- or “overheat” a water tank or the whole building, and avoid grid-overcharge and unwanted disturbances at the same time.
A PV system in connection with a speed-controlled compression heat pump (HP) for domestic hot water (DHW) and space heating (SH) purposes of a single family house (SFH) poses a challenging control task in this context. A model predictive controller provides a suitable approach to such a task with partly conflicting control objectives.
This research investigates a HP-PV system for Central Europe, consisting of a small-scale grid connected PV plant in connection with a HP charging a thermal storage and supplying the energy for space heating. The manuscript describes the reference system and explains the control task. The results for a single family house with a heating demand of ~45 kWh/(m2 a) and 20 m2 of south oriented PV modules indicate a share of 50% of the generated PV being directly used by the HP. During the heating season from September to April, this share is 77%. With respect to the total HP electricity consumption the average annual grid-consumption may be reduced to 40%.