Analysis of Photovoltaic Plants with Battery Energy Storage Systems (PV-BESS) for Monthly Constant Power Operation

Abstract

Photovoltaic generation is one of the key technologies in the production of electricity from renewable sources. However, the intermittent nature of solar radiation poses a challenge to effectively integrate this renewable resource into the electrical power system. The price reduction of battery storage systems in the coming years presents an opportunity for their practical combination with utility-scale photovoltaic plants. The integration of properly sized photovoltaic and battery energy storage systems (PV-BESS) for the delivery of constant power not only guarantees high energy availability, but also enables a possible increase in the number of PV installations and the PV penetration. A massive data analysis with long-term simulations is carried out and indicators of energy unavailability of the combined system are identified to assess the reliability of power production. The proposed indicators allow to determine the appropriate sizing of the battery energy storage system for a utility-scale photovoltaic plant in a planning stage, as well as suggest the recommended operating points made for each month through a set of graphs and indicators. The presence of an inflection zone has been observed, beyond which any increase in storage does not generate significant reductions in the unavailability of energy. This critical zone is considered the sweet spot for the size of the storage, beyond which it is not sensible to increase its size. Identifying the critical point is crucial to determining the optimal storage size. The system is capable of providing reliable supply of constant power in monthly periods while ensuring capacity credit levels above 95%, which increases the penetration of this renewable resource. Despite the fact that the study focuses exclusively on the analysis from an energy perspective, it is important to consider the constraints associated to real storage systems and limit their oversizing.

Sizing of Battery Energy Storage Systems for Firming PV Power including Aging Analysis

“…In coherence with our previous research [21,22], the present study continues with the analysis of the behavior of a PV-BESS hybrid plant. The quantification of the BESS degradation and the appropriate assignment of the constant power are carried out for a Energies 2024, 17, 1485 5 of 30 correct evaluation of the system.…”

“…In this paper, part of the model previously proposed in [21,22] is used. Following that, the equations that characterize the PV-BESS model are briefly described.…”

“…The S2P parameter defines the storage capacity of the system according to Equation ( 9) [21]. C MAX represents the storage capacity of the BESS in MWh, and P P is the peak power of the photovoltaic installation in MW.…”

“…In Equation (10), the concept of the Constant Power Operating Factor is introduced [21]. P GRID is the constant power that must be supplied to the electrical grid.…”

“…In [5], PV production is regulated with BESSs to maintain a constant output level, which significantly contributes to power grid stability, but only in a certain time interval during the day. In [21], an analysis of the optimal relationship between the optimal size of the required battery and the peak power of the generation system is presented, as well as the optimal operating setpoint of a PV + STG system to provide firm capacity all year.…”