/ Engineering · Power resilience
Power resilience
UPS, BESS, DG layered for outage.
Online UPS for sub-second bridging, LFP BESS for medium runtimes, DG for the long tail — sized as one resilient power stack.
- Default UPS topology
- Online double-conversion, N+1 above 50 kVA
- Default BESS chemistry
- LFP — 8+ year cycle life, thermal stability
- DG starting margin
- 200-300% of nominal load
Power resilience above 50 kVA is a layered specification: online UPS to bridge the sub-second outage, LFP BESS to extend silently for 30-90 minutes, diesel generator to handle the long tail with proper switchover logic. Each layer covers a different time domain, and the layers integrate through the ATS, the UPS bypass and the BESS state-of-charge logic.
We size each layer separately and then validate the integration as a whole. The UPS is sized for the critical load plus 25% growth. The BESS is sized for the gap between UPS runtime and DG start-and-stabilise time, with 30% reserve. The DG is sized for the critical load plus the BESS charge demand, with 200-300% starting margin. The interfaces are documented — what triggers what, what happens when each layer fails, what the operator sees. The result is a power resilience stack that holds through the failure scenarios it was designed against.
/ Sample interoperability matrix
UPS + BESS + DG
UPS bridges short outages; BESS bridges medium ones with quiet headroom; DG handles long outages with switchover discipline.
| Partner system | Fit | Engineering note |
|---|---|---|
Vertiv EnergyCore BESS vertiv-bess | Native | LFP cabinets integrate with online UPS via DC-DC interfaces — typically 5-10 minute to 8+ hour runtimes. |
LFP Chemistry lfp-chemistry | Native | LFP's thermal stability and cycle life make it the default chemistry above ~20 kVA. |
Online UPS Pattern online-ups-pattern | Native | Double-conversion topology isolates load from grid disturbances — the foundation layer of any resilient design. |
Entity graph
Related entities in the engineering graph
technology
Vertiv EnergyCore BESS
Vertiv's LFP battery-energy-storage cabinet line. Drop-in lithium replacement for VRLA banks on mission-critical UPS, with eight-year TCO advantages above 20 kVA.
technology
LFP (Lithium Iron Phosphate) Chemistry
The lithium-ion chemistry of choice for stationary BESS — thermally stable, safe for indoor install, 6,000+ cycle life, with eight-year TCO advantages over VRLA above 20 kVA loads.
infrastructure system
Online (Double-Conversion) UPS
Double-conversion uninterruptible power supply. Rectifies AC to DC and inverts back to clean AC, isolating the load from grid disturbances. Default for mission-critical IT and life-safety equipment.
Interoperability
Related interoperability matrices
Services
Where this maps to services
Engineering toolkit
Tools for this work
calculator
BESS Sizer
Peak-demand and tariff curve in, indicative LFP battery size, annual savings and payback period out. Vertiv, Delta and Fuji-class deployments.
calculator
DG → Solar+BESS Crossover
Diesel price, DG capacity and monthly run-hours in — the kWp solar + kWh LFP BESS that breaks even against running the genset out, plus capex, payback years and CO₂ avoided.
Methodology
Methodology principles cited above
operations
Graceful degradation over heroic recovery
A system that fails gracefully — fails one zone, not the whole building — is more valuable than a system that promises five-nines.
lifecycle
Lifecycle economics over capex minima
The cheapest specification at year one is rarely the cheapest at year seven. Specify against total lifecycle cost.
Glossary
Related glossary terms
BMS
UPS
Uninterruptible Power Supply. Generic term for any device that provides backup electrical power; in our practice always refers to online double-conversion UPS u…
BMS
Online UPS
A double-conversion uninterruptible power supply that continuously rectifies AC to DC and inverts back to clean AC, isolating the load from grid disturbances. D…
BMS
BESS
Battery Energy Storage System. Lithium-ion (typically LFP) battery banks paired with online UPS or stand-alone inverters, used for peak-shave, demand-response, …
· Last reviewed 2026-05-17 · pillar
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Concept
Online (Double-Conversion) UPS
Double-conversion uninterruptible power supply. Rectifies AC to DC and inverts back to clean AC, isolating the load from grid disturbances. Default for mission-critical IT and life-safety equipment.
Concept
LFP (Lithium Iron Phosphate) Chemistry
The lithium-ion chemistry of choice for stationary BESS — thermally stable, safe for indoor install, 6,000+ cycle life, with eight-year TCO advantages over VRLA above 20 kVA loads.
Service
Online UPS
Clean power, isolated from grid reality.
Service
Battery Energy Storage (BESS)
Power as an asset, not a cost.
Tool
BESS Sizer
Peak-demand and tariff curve in, indicative LFP battery size, annual savings and payback period out. Vertiv, Delta and Fuji-class deployments.
Tool
DG → Solar+BESS Crossover
Diesel price, DG capacity and monthly run-hours in — the kWp solar + kWh LFP BESS that breaks even against running the genset out, plus capex, payback years and CO₂ avoided.