Analysis of Avoided Transmission Through Decentralized Photovoltaic and Battery Storage Systems

Decentralized renewable energy systems can be low-carbon power sources, and promoters of local economies. It is often argued that decentralized generation also helps reducing transmission costs, as generation is closer to the load, thus utilizing the transmission system less. The research presented here addresses the question whether or not, or under what circumstances this effect of avoided transmission can actually be seen for a community-operated cluster of photovoltaic (PV) power plants in two sample locations, one in Germany and one in Japan. For the analysis, the newly developed instrument of MPI-MPE diagrams is used, which plot the maximum power import (MPI) and maximum power export (MPE) in relation to the reference case of no local generation. Results reveal that for moderately sized PV systems without battery storage, avoided transmission can be seen in the Japanese model location, but not in Germany. It was also found that additional battery storage can lead to avoided transmission in both locations, even for large sizes of installed PV capacity.

I. Introduction

Decentralized renewable power generation gains much attention as an environmentally friendly power source and a promoter of local economies. One additional advantage often advocated is that decentralized renewable electricity generation helps avoiding infrastructure cost, because the transmission system is used less, as generation is geographically close to the consumption [1]. However, in many cases, variable renewable energy hardly reduces the annual net peak load [2]. The authors of [3] quantitatively illustrate that grid interaction can decrease with the introduction of on-site photovoltaic (PV) systems in Australia, but show the effect only for one case with a fixed PV size. With larger PV sizes, increased generation could cancel out the avoided transmission and even require an enhancement of grid infrastructure for exporting the surplus electricity. Therefore, it is interesting to study how avoided transmission depends on the PV size, and how it changes if battery storage is added to the local energy system.