| name | include-small-genset-in-pv-battery-hybrid-rather-than-100-batter |
| description | Include small genset in PV+battery hybrid rather than 100% battery for island RO systems. Use when: designing a renewable energy system for remote island desalination with solar resource available. Provides: size a 70/30 PV+genset hybrid (e.g. 70% renewable, 30% genset backup) instead of 100% PV+battery, using the genset to enable emergency CIP cycles and evening load coverage.
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| version | 1.0.0 |
Include small genset in PV+battery hybrid rather than 100% battery for island RO systems
Provenance
- domain: technology-selection
- type: heuristic
- status: active
- confidence: 0.92
- support_count: 5
- composite_score: 0.893
- last_verified: 2026-05-14
- supportTrajectories: run-2026-05-14-fcc4ebed-technology-selection-6-y7ks, run-2026-05-14-fcc4ebed-technology-selection-12-oe0o, run-2026-05-14-fcc4ebed-technology-selection-24-g3vw
WHEN
designing a renewable energy system for remote island desalination with solar resource available
DO
size a 70/30 PV+genset hybrid (e.g. 70% renewable, 30% genset backup) instead of 100% PV+battery, using the genset to enable emergency CIP cycles and evening load coverage
BECAUSE
Maldives pilot data shows 70/30 achieves 95% renewable share and 99.5% availability with strictly lower capex than 100% PV+battery; the last 10% of renewable share costs more in battery than genset fuel saves over 10 years; genset provides on-demand headroom for membrane protection cycles
EVIDENCE
- user asks 'Pure PV+battery, or include a backup genset?'
- agent responds: 'The Maldives pilots have shown that a 70/30 PV+genset hybrid achieves 95 % renewable share AND 99.5 % availability — strictly better than a 100 % PV+battery design at the same capex'
- agent explains: 'The last 10 % of renewable share costs more in battery than the genset fuel saves over 10 years. The genset also gives you the headroom to run an emergency CIP cycle at any time, which protects membrane life'
- agent sizes 5 m³/day RO system: 'For a 5 m³/day RO with ERD plus auxiliaries (UV, calcite pump, doser, chlorinator) your total is ~22 kWh/day. That sizes to 6.1 kWp — round up to 7 kWp for cloudy days and cleaning cycles'
- agent uses formula: 'Daily kWh / (4.5 × 0.8)' where 4.5 is peak sun-hours and 0.8 is round-trip efficiency
- agent stated: 'The Maldives pilots have shown that a 70/30 PV+genset hybrid achieves 95% renewable share AND 99.5% availability — strictly better than a 100% PV+battery design at the same capex'
- agent reasoned: 'The last 10% of renewable share costs more in battery than the genset fuel saves over 10 years'
- agent identified: 'The two biggest availability killers on small-island RO are: (1) skipping the 6-monthly clean-in-place (CIP), and (2) running out of consumables (antiscalant, bisulfite). Tokelau's pilot failed at 18 months because the antiscalant tank ran dry without an alarm.'
- agent recommended: 'Mandatory: low-level switches on every consumable tank wired to a stop-on-empty relay. Cheap fix, prevents the most common premature-failure mode.'
- Agent stated: 'Hardened, sealed enclosure for the unit — not just a roof. Funafuti's first install lost ~20 days/year to storm damage; the retrofit got them to 99% availability.'
WEB SOURCES
