## Abstract

Adding much variable renewable energy production such as photovoltaics (PV) may cause severe mismatch between power supply and demand, which could constrain the use of PV as the main power option. Here we analyze the role of energy storage to compensate for the mismatch over a wide range of geographical sites and load types. The impact of PV-storage systems was mainly characterized through changes in the PV self-consumption (F). The sensitivity of PV-storage system sizing to costs and weather variations, and impacts to the remaining power system, were also considered. The main method used was energy balance simulation and a graphical method for PV-storage cost optimization. The main finding is that already a moderate amount of storage capacity could notably increase the utility of PV across all sites (26–60°N) and load types (from single household to regional/national load) studied. The optimal benefit is obtained with a net storage capacity of up to 2 kWh for each kW_{p} of PV over all the loads and sites studied, when PV is sized equal to the yearly load. With a storage-to-PV ratio (r) of 2 WhW_{p} ^{−1}, a PV-storage system could reach a self-consumption of 60–70% in a northern climate and 80–90% in a southern climate, respectively. The sensitivity of the optimum to yearly variations in solar insolation was minor. Targeting for a higher solar share would sharply increase the storage demand – covering all demand through PV requires up to two orders of magnitude more storage. The exact value of the optimum storage to PV array size strongly depends on the self-consumption target, costs, and site. With present storage cost levels and decreasing PV prices, oversizing PV over storage would be preferred to minimize the investment costs for a given self-consumption. With a typical PV-to-storage unit cost ratio (μ) of $500/kWh–$1200/kW_{p}, the optimum for F = 70% is found at r ∼1 WhW_{p} ^{−1} for 42–60°N. The slope of the minimum cost is moderate, i.e. the sensitivity of the results to price changes in the vicinity of this minimum point is modest − halving the storage cost would affect the results by 10%. The analyses also indicate major impacts to the remaining energy system, which should deserve future attention. These findings help to better plan energy systems with PV.

Original language | English |
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Pages (from-to) | 218-228 |

Number of pages | 11 |

Journal | Journal of Energy Storage |

Volume | 18 |

DOIs | |

Publication status | Published - 1 Aug 2018 |

MoE publication type | A1 Journal article-refereed |

## Keywords

- Energy storage
- Optimization
- Photovoltaics
- Self-consumption
- Sizing