Designing Solar Power Purchase Agreement of Rooftop PVs with Battery Energy Storage Systems under the Behind-the-Meter Scheme

Chawin Prapanukool,Surachai Chaitusaney

doi:10.3390/en13174438

Abstract

With a significant growth of rooftop photovoltaic systems (PVs) with battery energy storage systems (BESS) under the behind-the-meter scheme (BTMS), the solar power purchase agreement (SPPA) has been developed into one of the most attractive models. The SPPA is a scheme where the investors propose to directly sell electricity from rooftop PVs to the customers. The proposed rates are typically performed in terms of the discount rates on the time-of-use (TOU) tariff with demand charges. The operation modes of the BESS should also be designed in accordance with the proposed rates. Therefore, this paper proposes a methodology to design the discount rates and operation modes of the BESS which will minimize the electricity charges of the customers while maintaining the revenue of the investors under the SPPA and BTMS. The reverse power flow is considered as additional revenue to the investors. This paper also implements the proposed methodology with tariff structure in Thailand. The result showed that the installed capacity of rooftop PVs and battery capacity directly affect the discount rates and operation modes of the BESS. The rate of excess energy also has a significant impact on the discount rates but not affect the operation modes.

Highlights

With a significant growth of rooftop photovoltaic systems (PVs) under the behind-the-meter scheme (BTMS), several investors have adopted and developed many business models of rooftopPVs [1,2]
This paper proposes a methodology to design the solar power purchase agreement (SPPA) and operation modes of the battery energy storage systems (BESS) for
This paper proposes a methodology to design the SPPA and operation modes of the BESS for rooftop PVs with BESS by applying the discount rates on TOU tariff with demand charges under BTMS

Summary

Introduction

With a significant growth of rooftop photovoltaic systems (PVs) under the behind-the-meter scheme (BTMS), several investors have adopted and developed many business models of rooftopPVs [1,2]. The SPPA is one of the most attractive models where the investors act as a third party to directly sell electricity from their rooftop PVs to the customers at a lower rate than the utility’s retail rate [4,5]. The challenge for all investors is the competitive discount rates on the TOU tariff with demand charges that can propose to the customers. Four necessary principles (battery energy storage systems, rooftop PVs with BESS, TOU tariff with demand charges and the behind-the-meter scheme) are applied in this paper. The rated energy and power capacity are presented by considering the roundtrip efficiency (ηrt ) and battery bi-directional inverter efficiency (ηbi-inverter ), as shown in Equations (1) and (2): Cnom = Cnom,dc ·ηbi−inverter · ηrt.

Methods

Findings

Discussion

Conclusion