- A hybrid project must be reviewed as one system, not as two independent assets on the same site.
- Separate revenue forecasts overstate value when the solar and the battery compete for the same point of connection, state of charge or dispatch opportunity.
- Shared infrastructure can reduce cost but may create a single point of failure and blurred performance responsibility.
- Mine-site solar, BESS and engines must be designed, controlled, tested and contracted as one reliable power system.
Shared connection capacity can create conflicts between revenue streams
Hybrid asset interface map
The combined asset is governed by shared interfaces. Separate component models cannot show these conflicts.
Solar wants to export during high irradiation. The battery may want the same connection capacity for an upward service or later discharge. If both share a limited point of connection (POI), the model must decide which asset has priority, which output is curtailed and who bears the lost revenue.
The battery is also a load while charging. An existing generation connection may not automatically provide unrestricted import capacity. Connection agreements, the generator performance standard, metering and dispatch arrangements must be checked. Export approval does not automatically allow import.
Who does what in a hybrid or BESS project
Assign each decision, interface and remedy to a named party. Then review the points where responsibility passes from one party to another, because most delivery risk sits at those boundaries.
Every shared function should have one design owner, one integration owner, one test and one contractual remedy.
Verify which costs the assets can actually share
AFRY cites potential hybrid savings in the order of 5–15% CAPEX and 10–20% OPEX, mainly from shared connection, substation, civil works and asset management. These are external experience ranges, not project assumptions. The battery, warranty, insurance, spares and market costs do not disappear because solar is nearby.
Diligence should identify which equipment can actually be shared, whether capacity is adequate, whether consent can be modified, who guarantees availability and whether either asset can operate independently during an outage. Any saving should be net of additional control, testing and contract complexity.
Gaps between contracts can leave key interfaces without a responsible party
When the battery supplier covers the battery blocks and power conversion while the construction contractor covers transformers, the plant controller, the monitoring system and the point of connection, their assumptions can diverge. A disagreement over equipment quantity, control mode or transformer configuration can become a variation, performance gap or schedule claim.
An integrated interface matrix should map each function to design, supply, integration, testing, performance guarantee and remedy responsibility. The financial model must also use joint dispatch at an appropriate interval, including connection constraints, SOC, losses, degradation, curtailment absorption and service conflict.
For mining hybrids, reliability is a constraint
Solar + BESS + diesel or gas adds black start, spinning reserve, step-load and extreme-weather requirements. The lowest-LCOE combination may be unable to maintain production. Reliability is a binding design constraint.
The real diligence question is whether the combined assets can perform as one power station under a common control system. If that is not built into the design, testing and contracts, the assets may share a site without operating as a reliable, financeable system.
Based on AFRY’s webinar One plus One Equals One: Better Due Diligences for Hybrid Assets. Experience ranges require project-specific verification. Australian mining application is independent analysis. Commentary only — not engineering, legal or investment advice.