A coastal municipal utility in the Visayas replaced an 8-to-10-hour-per-day diesel supply with an 85kWp solar array, 120kWh of LiFePO4 storage and standalone solar street lighting, lifting community availability from roughly 55 percent to above 96 percent. This case study walks through the sizing logic, the real CMJ Solar products used, and the fuel and cost numbers behind the project.
Project Background: An Island Utility Dependent on Diesel
The barangay served by the utility sits on a small island reached by outrigger boat, with about 210 households plus a clinic, an elementary school, a church and a small port area. Before the upgrade, the grid was a single 120kVA diesel generator running four to five hours each evening. Households paid the equivalent of 25 to 30 Philippine pesos per kilowatt-hour, several times the Luzon tariff, because fuel had to be barged in during calm-sea windows and stored in drums.
The diesel model carried four problems the local government wanted removed. Fuel logistics failed completely for days during monsoon surges, the generator needed increasingly frequent servicing, evening-only power could not support the school's computers or the clinic's vaccine refrigerator, and the diesel noise and fumes dominated the waterfront. A missionary-electrification grant plus a municipal loan funded a solar-plus-storage microgrid with diesel retained purely as emergency backup. The design pattern mirrors the reliability-first approach described in our guide to off-grid solar battery systems for island and weak-grid markets.
System Design and Product Selection
The design started from a metered load study. Average consumption was modeled at about 300 to 320 kilowatt-hours per day, with an evening peak near 30kW driven by lighting, fans and television loads plus daytime commercial loads at the port and municipal buildings. The engineering team set four requirements: three-phase 230/400V supply, overnight storage covering roughly eight hours of average draw, motor-start headroom for water pumps, and salt-air tolerant outdoor equipment.
Generation is an 85kWp ground-mounted and carport array, chosen over rooftop mounting to avoid typhoon exposure on weak roofs. Storage was specified as eight units of the Ares 15kWh All-in-One ESS with 12KW Inverter, totaling 120kWh nominal and about 96kWh usable at an 80 percent design depth of discharge. Each unit carries a 51.2V LiFePO4 pack, dual MPPT trackers rated for two 7500W PV inputs, and a 200A discharge path. The eight 12kW inverters were distributed across three phases, and their combined surge capacity comfortably starts the community water pump and rice-mill motors that a single small inverter could not.
Public lighting was deliberately separated from the microgrid. Thirty-six units of the MJ-SSO100 all-in-one solar street light, each delivering 4500 lumens from 45 high-output LED chips with a 60Ah LiFePO4 battery and IP65 sealing, were installed along the port road, school path and main village lanes on 6-meter poles. Standalone lights mean the pathways stay lit even if the main microgrid is in maintenance, and they add zero nighttime load to the storage bank. The full fixture range is shown under the all-in-one solar street light category.
For future expansion the utility pre-provisioned rack space for modules identical to the Rack-Mounted Battery 10kWh (51.2V/200Ah), so capacity can grow as household consumption rises without changing the cabinet architecture.
Installation and Commissioning
Installation took about seven weeks including civil works, which is realistic for an island site where concrete and panels arrive by barge. The eight ESS units were set in a raised concrete equipment room with louvred cross-ventilation and a dehumidifier, an important detail in coastal humidity. The all-in-one architecture cut field wiring dramatically compared with a split system: each machine arrived as a tested battery-inverter pair, and commissioning focused on phase rotation, communication addressing and the export-control settings rather than on matching separate components.
Commissioning followed three stages. First, the array charged the batteries to 100 percent with BMS telemetry confirmed on each unit, including cell balance and temperature readings. Second, the team ran controlled black-start tests, proving the microgrid could form the grid from battery alone with no generator running. Third, lights, clinic and school circuits were transferred one feeder at a time while technicians logged voltage and frequency stability under motor starts. Product selection for the lighting component followed the public-project criteria in our solar street light selection guide, and structural choices drew on our solar street light installation guide.
Results: Fuel, Availability and Cost
Twelve months of operating data show the transformation. Generator run time fell from 28 to 35 hours per week to roughly 4 to 6 hours per week, used only during prolonged monsoon cloud cover and for periodic maintenance exercising. Diesel consumption dropped from about 110 liters per day to approximately 10 to 15 liters per day, cutting the fuel budget from roughly 40,000 to 45,000 dollars per year to under 6,000 dollars. Combined with lower generator maintenance, the utility nets about 35,000 dollars in annual savings against a total electrification capex near 210,000 dollars, which puts simple payback around six years before counting the avoided cost of replacing the aging generator.
Service quality improved even more visibly. Electricity is now available around 23 hours per day on average, with availability above 96 percent across the year versus roughly 55 percent before. The clinic now runs reliable refrigeration, evening study hours replaced kerosene and flashlight use, and the 36 solar street lights have operated continuously through two typhoon-season storm windows with no failures. The LiFePO4 banks cycled daily without maintenance, and every unit remained inside the manufacturer's 80 percent usable-depth-of-discharge design window, which is what the 5-year CMJ Solar battery warranty assumes.
Operations, Maintenance and Community Impact
Remote island systems cannot rely on weekly technician visits, so the operating model was designed around remote monitoring and simple local tasks. Each ESS unit streams state of charge, power flow, alarms and temperature to a dashboard at the municipal utility office and to the supplier's support team, which flagged one underperforming string combiner box within its first month and corrected it on the next scheduled boat trip. Local staff were trained for three jobs only: visual checks after typhoons, cleaning the panels and fixture lenses, and restarting the microgrid from a documented black-start procedure. Keeping the maintenance scope this narrow is deliberate; complex troubleshooting was centralised rather than pushed onto village operators.
The social outcomes showed up within the first quarter. Evening sari-sari stores extended opening hours, the school scheduled computer classes after lunch when solar production peaks, and the clinic reported that its vaccine refrigerator held temperature continuously through the wet season for the first time. Nighttime foot traffic along the port road increased once the 36 fixtures established a reliably lit corridor, which also mattered for emergency evacuations during storm warnings. These effects are difficult to capture in a simple payback model, but for municipal grant programs they are often the difference between a funded and an unfunded extension project, and they justify the modest extra cost of autonomous public lighting.
Lessons Learned
Four lessons transfer to other island projects. First, oversize PV rather than storage in cloudy coastal climates: an 85kWp array on a 30kW peak load sounds generous, but it is what refills 120kWh of batteries through rainy weeks and keeps the generator off. Second, all-in-one units with matched inverter and BMS firmware remove the single biggest commissioning risk on remote sites where return visits take days. Third, decoupling street lighting onto autonomous solar fixtures improves resilience and simplifies nighttime energy accounting. Fourth, the financial case should be built on barged-fuel reality: delivered diesel on small Philippine islands routinely costs twice the pump price, which is exactly what makes solar storage competitive even without subsidies. The complete battery lineup for similar projects is available in the energy-storage catalog, and municipal contractors can contact CMJ Solar for a modeled bill of materials matched to their load survey.
Frequently Asked Questions
Can a solar microgrid completely eliminate the diesel generator? Most island designs retain a small generator for prolonged cloudy spells and annual maintenance, but as this project shows it can be reduced from the primary supply to an emergency backup running a few hours per week. A fully diesel-free design is possible with more storage headroom and a larger array, traded against capex.
How long do the batteries last in a daily-cycling island microgrid? LiFePO4 packs operated within an 80 percent depth of discharge and the BMS temperature window are rated for thousands of cycles, which supports more than a decade of daily cycling in most microgrid schedules. CMJ Solar covers the storage with a 5-year manufacturer warranty and BMS log review.
Why use all-in-one ESS units instead of separate inverters and battery racks? On remote sites the tested battery-inverter pairing shortens commissioning, removes firmware mismatch risk and gives one supplier responsibility. Rack expansion remains an option later, which is why the project pre-provisioned space for 10kWh rack modules.
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