ESB hydroelectric dam ROV inspections

How the ESB programme began

The ESB work grew out of an earlier engagement with Irish Water. As Bob Foley, founder of Engineers With Drones, explains: "We got a call from Irish Water asking if we do underwater drone work, which we quickly tooled up for and started on." Having established that capability, Engineers With Drones reached out to the ESB with the same offer. That conversation was circulated internally, and it led to a long-running inspection programme that now covers most of the ESB's hydroelectric sites across Ireland.

Site managers contact Engineers With Drones when they have a specific issue, a routine inspection due, or an asset they need visual evidence on. Engineers With Drones request drawings of the relevant infrastructure beforehand — both to confirm whether the job is suitable for ROV deployment and to understand the layout before arriving on site.

A micro ROV built for confined spaces

The ROV used for this work is a new class of micro ROV, approximately the size of a cereal box. It is tethered — always physically connected to the operator by a long cable — which means it can be retrieved instantly at any point in the inspection. This is the fundamental safety advantage over a diver: if something goes wrong, you pull the drone out.

The ROV features a 4K camera and very high-powered lights, which are essential because most of the infrastructure it operates in is entirely dark. It has 360-degree thrusters, allowing it to move in any direction without turning. On-board sensors provide depth measurement, position holding, and altitude holding — the standard suite of features for a ROV of this class.

The system also supports accessories. A grab attachment allows the ROV to pick up and move objects. "We picked up a few dropped chains, lifting chains and stuff like that for gates and hydroelectric gates for the ESB in our time", Bob notes. This recovery capability means a single deployment can deliver both inspection data and practical task completion.

How inspections are planned and executed

Before any site visit, Engineers With Drones request detailed drawings of the infrastructure to be inspected. These are reviewed to confirm that the work is suitable for ROV deployment and to map out the intended route. On site, the ROV is set up at a suitable deployment location and the operator navigates from that point to the target asset.

The core rule of thumb for feasibility is straightforward. "If we had a very, very, very long stick, we should be able to touch the item", Bob explains. That means the preferred route is a direct, unobstructed line from the operator to the inspection target. There are exceptions — if the access route has no sharp corners, edges, or snag hazards, the ROV can navigate more complex paths — but the straight-line principle guides most deployment decisions.

What gets inspected

The range of assets inspected across the ESB programme is broad. Each site visit is typically driven by a specific inspection need from the site manager, but the variety of infrastructure covered over the course of the programme is extensive.

Inlet screens

Inlet screens are one of the most frequently requested inspection items. Debris — tree trunks, branches, leaves, general river material — accumulates on the screens over time, and the screens exist specifically to prevent that debris from reaching the turbines. Regular visual inspection confirms whether blockage is developing and whether the screen itself is in good condition.

"This would have been done with divers back in the day, but nowadays they just call us in. We can do it in a day usually, pretty quick, no problem at all", Bob explains.

Turbines and spiral casings

Engineers With Drones have inspected turbines by approaching from the downstream side — swimming the ROV up inside the structure when the turbine is inactive to capture imagery of its condition. The spiral casing, which guides water into the turbine, has also been inspected at several sites.

Gates, sealing surfaces, and weirs

Gate sealing surfaces are inspected to confirm they are maintaining a proper seal and have not deteriorated. Weirs and associated structures are also part of the programme. The ROV provides detailed close-up imagery of sealing surfaces that would otherwise require the gate to be removed or the structure dewatered.

Scour drains and valves

Scour drains and valve infrastructure are also routinely inspected. The ROV navigates down through tubes and channels to assess the condition of valves and check for blockages or defects. "Anything you could put a cereal box into realistically, we've gotten into", Bob notes.

A standout dive — through the ventilation shaft to the turbine

One of the most technically demanding deployments in the ESB programme illustrates clearly what the ROV makes possible. The inspection required access to the turbine at the base of a dam — an asset that, in most circumstances, would require the entire structure to be drained down.

Instead, Engineers With Drones operated the ROV from the top of the dam, sending it down a ventilation shaft into the intake. The ROV then navigated through the intake and accessed the turbine directly. "That sort of dive would be impossible, literally, to do with divers or any other sort of structure", Bob explains. The confined nature of the route, combined with the darkness and the pressure environment, ruled out any human entry — but for the ROV, it was a complex dive that presented no operational problem.

The tether provided the operational safety margin throughout. At any point, the operator could simply pull the ROV back out. In a confined environment with no visibility and no reliable communication, that physical connection is the entire risk-management strategy — and it works.

Why the ROV succeeds where divers and dewatering do not

The ESB programme demonstrates two distinct scenarios where the ROV offers a fundamental operational advantage over the alternatives.

The first is replacing dewatering. To inspect underwater infrastructure without an ROV, the conventional approach is to drain down the relevant section of the structure entirely and erect scaffolding to provide access. This is expensive, time-consuming, and puts the generating station out of service for an extended period. The ROV eliminates that requirement entirely — the inspection happens in the water, with no downtime beyond the deployment itself.

The second is replacing divers in locations divers will not go. Many of the confined spaces and narrow channels that form part of hydroelectric infrastructure are assessed as too dangerous for divers to enter. As Bob Foley, founder of Engineers With Drones, explains: "A lot of the time divers won't go into the places we go because it's too dangerous for them, but we can go there no problem because it's a drone, and because the drone is a lot smaller than the diver. If something goes wrong, we can just pull the drone out."

In both cases, the ROV provides the inspection data the client needs — in high resolution, in real time — without the cost, the risk, or the operational disruption of the traditional alternatives.

ROV inspection footage

ROV inspection footage captured during the ESB hydroelectric dam inspection programme, showing the type of underwater imagery provided to site managers for condition assessment.