Temporal matching instead of annual balance: Limits of a PV battery assessment from an anonymised energy consultancy report

Annual energy indicators and a stated battery capacity are not sufficient to determine unambiguously the operational benefit of a PV battery system. This paper examines the information limits of an anonymised energy consultancy report and develops a normalised, time-discrete storage experiment. From the stated system data, a ratio of usable storage capacity to PV peak power of about 4.58 hours is derived. Site-specific yield data, electrical load profiles, battery power and operating strategy are missing from the available export. Therefore, no annual yields or self-sufficiency rates of the case building are estimated. Instead, synthetic 24-hour profiles with identical energy integrals compare different temporal load positions. With an ideal battery, a constant load is fully covered, whereas a completely downstream load is covered by only 76.3 per cent. With separate charging and discharging efficiencies of 95 per cent each, these values fall to 92.7 and 72.5 per cent respectively. An additional charging power limit reduces the coverage of the constant load profile to 70.1 per cent. All percentages are results of an explicitly constructed experiment and not forecasts for the building. Using energy conservation, power limits and state of charge, the paper shows which conclusions annual balances cannot support and specifies the data needed for a robust follow-up assessment.