Integrated power blocks

How does Integrated power blocks work, step by step?

1. 1

   Step 1: Settle the arrangement at concept stage

   The choice between integrated blocks and separate conversion plant is made before the layout is drawn, because everything else follows from it. The electrical designer sets out what the connection point requires, the developer sets out the capacity and the duration the project is being built to trade, and the fire engineer confirms what each candidate arrangement would demand in space and separation. Comparing arrangements on unit price alone is the classic mistake. The comparison that matters covers land take, civils, cabling, spares, maintenance access and who carries the performance risk, over the whole life of the project rather than the construction period.

2. 2

   Step 2: Fix the block specification with the supplier

   Once the arrangement is chosen the supplier's standard product is reviewed against the project. Enclosure size and weight drive the foundations and the crane. Ventilation and access openings drive the spacing and the orientation. The control interface drives what the wider site control system has to speak. The specification records what the block must do, and the supplier confirms what its product does, and any gap between those two is closed on paper long before delivery. Late changes to a factory-built product are expensive and are often simply refused.

3. 3

   Step 3: Build the foundations and the routes to suit the product

   Foundations are designed for the block's point loads, its fixings and its tolerance for differential movement, which for a unit containing its own transformer is usually tighter than people assume. Cable routes, ducts and pits are set out to arrive where the block's entries are, not where the civils contractor would prefer. Access roads and hardstandings are designed for the delivery vehicle and the crane, and for the same vehicle returning years later to take a unit away. Getting a unit out again is a design case, not an afterthought.

4. 4

   Step 4: Take delivery and verify what arrived

   Blocks are tested at the factory before despatch, and the project should witness or at least receive the results of that testing rather than discovering problems on site. On arrival each unit is checked for transport damage, for the correct configuration, and for the documentation set that the commissioning team will later need. Units are heavy, awkward and delivered on a tight sequence, so the lift plan, the ground conditions under the crane and the delivery order are all agreed in advance. A unit set down in the wrong position is a bad day.

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   Step 5: Place, fix and connect

   Each block is lifted onto its foundation, levelled, fixed down and earthed in accordance with the electrical designer's drawings. The medium voltage cabling is brought in and terminated by the competent parties named for that work, and the control and communications cabling is landed and labelled. Terminations and labelling are the two items that consistently cost time later, so they are inspected as they are completed rather than at the end. Nothing is energised at this stage and the site remains a construction site.

6. 6

   Step 6: Integrate the blocks into one plant

   Individually the blocks are products. Collectively they have to behave as a single power station, which means the site controller has to see every block, dispatch every block and receive back what it needs from every block. That integration is done by the control system supplier working with the block supplier, and it is where most of the schedule risk on an integrated scheme actually sits. Interface testing is planned as a task in its own right, with its own duration, rather than assumed to happen during commissioning.

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   Step 7: Hand the block interface into commissioning

   Before the commissioning sequence starts, the responsibility for each block passes formally from installation to the commissioning team, with a documented record of what has been installed, inspected and left unenergised. The block supplier is present for the steps that concern its equipment, because the warranty on a factory-built product usually depends on it. From this point the site moves onto the commissioning process, which is a sequence of formal authorisations rather than a single handover.

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   Step 8: Plan for replacement from the beginning

   A battery unit is a consumable on a long timescale. Cells degrade, conversion equipment is superseded, and augmentation or replacement is expected within the operating life of most projects. The layout, the access roads, the crane standings and the spares strategy are all set up on day one for a unit to be taken out and another put in, with the supplier's route back to site understood. Projects that treat the blocks as permanent fixtures pay for it later.