Special Case, PV System Integration

Besides solar thermal collectors, nowadays PV are also effectively used for converting solar energy. Recently, PV installed capacity is growing faster than previous four decades and PV cost is decreasing (Wu et al. 2015). This makes them good candidate for supplying electricity to SAGSHP, reducing the fossil fuel based consumed energy and consequently boosting the renewable energy consumption. Indeed, being electricity needed for running circulation pumps and heat pump, PV can potentially cover the electricity demand of SAGSHP system. Unless demand side management or load shifting procedures are not in place, direct connection between PV and SAGSHP in not recommend if the aim is to match the renewable energy onsite production with SAGSHP energy consumption. Demand side

Final energy balance

Fig. 4.13 Final energy balance (left axe), energy consumption (left axe), PV and solar thermal surfaces (right axe) of SAGSHP solutions (refer to Table 4.9 for system configuration description) for Milan, Rome and Palermo. Note Bars refer to the final energy balance, which includes the consumed PV energy, and the final energy consumption, which does not include the PV energy. Points refer to the PV and solar thermal surfaces (Reda et al. 2015) management and load shifting procedures applied to thermal generation often requires large thermal storages. In principle, storing heat produced by means of a heat pump supplied by PV is a winning strategy. However, if solar thermal collectors are also used, they will also produce heat at the same time when PV is producing electricity. Therefore, two systems (solar thermal collectors and heat pump) will produce heat and store it simultaneously. This could limit system operations. Thus, sizing both PV and thermal collectors becomes a serious issue to optimize the overall system efficiency. Batteries can mitigate this issue, adding more flexibility to the system. They are also key components for the transition towards smart grid and smart home, especially going for distributed generators based smart grid configuration. Indeed, bridging electrical renewable generation and storage (PV and batteries) and thermal grid and storage (heat pump and storage tank) represents a promising smart home configuration (Howlader et al. 2016). Even rather conventional (in accordance with local laws), not optimized, SAGSHP configuration with PV and batteries is able to achieve significant energy savings (Fig. 4.13) (Reda et al. 2015).

In localities where solar irradiance is high, SAGSHPs with relatively small solar energy production systems, both solar thermal collectors and PV, are able to achieve good final energy site consumption levels (final energy balance in Fig. 4.13): 7 kWh/m2 (Rome) and around 6 kWh/m2. Obviously, impact of PV generations on final energy consumption, which does not consider PV produced energy, is more tangible in hot climate (Palermo, Fig. 4.13), where PV energy production matches building cooling demand, than in mild climate locations (Milan, Fig. 4.13) (Reda et al. 2015). Indeed, the difference between final energy balance and final energy consumption is higher in such localities.

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