{"id":5086,"date":"2026-08-29T22:47:24","date_gmt":"2026-08-29T14:47:24","guid":{"rendered":"https:\/\/www.solidess.com\/?p=5086"},"modified":"2026-08-29T22:47:24","modified_gmt":"2026-08-29T14:47:24","slug":"pv-charging-priority-ci-bess","status":"publish","type":"post","link":"https:\/\/www.solidess.com\/fr\/pv-charging-priority-ci-bess\/","title":{"rendered":"Priorit\u00e9 de recharge photovolta\u00efque : pr\u00e9server une marge pour l'\u00e9nergie solaire et l'\u00e9nergie n\u00e9cessaire \u00e0 la pointe du soir"},"content":{"rendered":"
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An ESSA0100B-0215<\/a><\/strong> is a sensible first screen when the required battery-charging duty stays within 100 kW and the day\u2019s surplus energy fits the validated SOC headroom. If a plant repeatedly produces 120 kW more than the facility uses, the cabinet can still charge at 100 kW, but the remaining 20 kW needs a defined destination: permitted export, PV curtailment or an approved flexible load. That decision belongs in the design, not in the first week of commissioning.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Consider the same plant at 11:30 a.m. Rooftop PV is producing 95 kW more than the site load, but overnight recovery left the battery close to its upper SOC. By 1:00 p.m. the battery is full and the plant controller is curtailing PV. Afternoon peak shaving then uses part of the stored energy, while the protected reserve locks another part. At 5:30 p.m. too little usable energy remains for the full evening target. Nothing failed; the schedule treated midday capture, afternoon dispatch and evening demand as separate jobs even though they share the same battery.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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MegSolid ESSA0100B-0215 gives this duty a 100 kW PCS, 215.04 kWh of nominal LFP energy and an integrated EMS. Its practical advantage is that the battery limits, PCS command and daily schedule sit in one storage-control platform. PV charging priority decides when to leave room, when to accept solar and when to release that energy. Coincident PV and load data still have to prove the power and energy fit before the cabinet is awarded.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Define solar surplus at the PCC<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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The PV inverter may report 180 kW, but that is not the battery\u2019s charging opportunity. If the facility is using 85 kW at the same moment, only 95 kW remains before the export rule is applied. Site load, the chosen export target and the live battery limit have to sit in one power balance.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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For an AC-coupled plant, count site load without BESS charging and write down the sign convention:<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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PV surplus requiring BESS action = max(0, PV generation \u2212 site load \u2212 export target)<\/code><\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Le export target<\/strong> is the operating value used by the EMS or plant controller. It is zero on a zero-export site and can be positive when the owner intentionally sells power. The contractual export limit remains the outer boundary, but it does not decide whether a permitted kilowatt-hour should be sold or stored. That commercial choice needs a signed operating target.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Charge request in the same interval:<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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PV charge request = min(PV surplus, PCS charge limit, live BMS charge limit, SOC-dependent charge limit)<\/code><\/p>\t\t\t\t<\/div>\n\t\t\t\t

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PCC feedback trims the request so measured export stays on target. If the meter becomes stale, a CT is reversed or a tie breaker changes the control boundary, the EMS must enter the approved fallback. Holding the last valid charge command can turn a data fault into an export violation.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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CT placement, fail-safe and who owns curtailment: PCC zero-export control page<\/a><\/strong>.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Follow one solar day from morning to evening<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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The worked example is a factory with a zero-export target and one 100 kW cabinet. All values are AC power at the site boundary.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Heure<\/th>PV<\/th>Gross facility load, excluding BESS<\/th>Immediate EMS decision<\/th><\/tr><\/thead>
08:00<\/td>40 kW<\/td>170 kW<\/td>Discharge 30 kW to hold a 100 kW import target, if reserve allows<\/td><\/tr>
11:30<\/td>180 kW<\/td>85 kW<\/td>Up to 95 kW is available for charging<\/td><\/tr>
13:00<\/td>210 kW<\/td>90 kW<\/td>120 kW surplus; a 100 kW charge limit leaves 20 kW for curtailment or another approved actuator<\/td><\/tr>
17:30<\/td>20 kW<\/td>150 kW<\/td>Discharge 30 kW to hold a 100 kW import target, if reserve and SOC allow<\/td><\/tr><\/tbody><\/table><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t
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The table has to be read in both kW and kWh. At 1:00 p.m. the cabinet may still have unused energy space, yet its 100 kW charge-power ceiling leaves 20 kW unabsorbed. At 5:30 p.m. the reverse problem can appear: 30 kW of discharge power is available, but the stored energy may not last through the full evening block.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Put a value on the 20 kW the battery cannot accept<\/h3>\t\t\t\t<\/div>\n\t\t\t\t
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If the 20 kW residual lasts for two hours on 250 operating days, the annual energy exposed to export or curtailment is:<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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20 kW \u00d7 2 h\/day \u00d7 250 days = 10,000 kWh\/year<\/code><\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Apply the site\u2019s verified energy value rather than a generic marketing tariff:<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Annual exposure = 10,000 kWh\/year \u00d7 verified site value of curtailed or exported kWh<\/code><\/p>\t\t\t\t<\/div>\n\t\t\t\t

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On a zero-export plant, that energy is lost through the inverter limit. Where export is allowed, compare the export credit with the value of holding the same energy for the evening peak.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Do not buy another power stage until this line is filled with site data. A small annual exposure may not justify a larger PCS. A recurring 80 kW residual lasting four hours, especially when the site later pays an evening demand charge, can change the decision quickly.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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SOC headroom is an energy budget<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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Charge power answers how fast the battery can absorb solar. SOC headroom answers how long it can keep doing so.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Keep dispatch and headroom on one energy boundary:<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Available charging headroom = energy at upper SOC limit \u2212 energy at current SOC<\/code><\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Suppose the noon forecast contains 120 kWh of PV energy above site load and the export target, while the battery has only 70 kWh of validated headroom on the same energy boundary. About 50 kWh of additional room is needed before the solar crest, plus the agreed allowance for forecast error and conversion losses.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Morning peak shaving, a lighter overnight grid charge, or a flexible midday load can open that room. Protected reserve stays closed when the forecast may miss.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Charging efficiency and auxiliaries must be aligned before battery-side headroom is compared with an AC-bus PV forecast. Otherwise, two different energy boundaries are being subtracted as if they were the same.<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Four inputs for a preliminary PV charging table<\/h3>\t\t\t\t<\/div>\n\t\t\t\t
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A useful preliminary screen needs:<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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