Case Studies

Each case describes a practical problem on an operating or planned asset, the analysis carried out and the result.

Desalination Designing a Record-Low Water Tariff A seawater reverse osmosis plant of almost 1 million m³ per day, built around one of the lowest costs of water in the world. ›

The Project

One of the largest seawater reverse osmosis plants in the world, producing almost 1 million m³ of water per day under a long-term water purchase agreement. The plant is powered by the grid and by a dedicated solar PV field, which covers more than 30% of its energy demand.

The Challenge

At this scale the cost of water depends on three things: specific energy consumption, plant availability and the cost of replacing membranes and consumables. A small difference in any of them changes the tariff over the whole contract period, so the operating assumptions had to be defined with the same rigor as the design.

The Analysis

• Specific energy consumption by train and operating point
• Availability and the maintenance assumptions behind it
• Membrane ageing and replacement strategy
• Integration of the solar field with the grid supply

The Outcome

The plant was awarded at one of the lowest water tariffs in the world, with a specific energy consumption among the lowest for a plant of this scale.

Load forecasting Rebuilding a Regional Load from Monthly Measurements Recreating the hourly electricity demand of a whole region from partial monthly data, as the basis for sizing a solar and storage investment. ›

The Project

A utility-scale solar PV plant with battery storage, connected to the grid by a dedicated transmission line and expected to supply the electricity needs of hundreds of thousands of people. The size of the investment depended on one figure that nobody had: how much electricity the region actually consumes, hour by hour.

The Challenge

Only partial monthly measurements of the regional consumption were available. A monthly total cannot show when the demand occurs, and without that it is not possible to say how much solar production the network can absorb, or how large the storage has to be.

The Analysis

• Reconstruction of the annual hourly load profile from the partial monthly measurements
• Weather-driven discomfort and human-activity indices derived from typical meteorological year data, used to describe when and why consumption rises or falls
• Machine learning models trained on the load patterns of comparable networks, applied to the region and checked against the measurements that existed (this approach typically reaches 2 to 9% error)
• Comparison of the reconstructed load with solar production to size the PV plant and the battery storage

The Outcome

A reliable hourly load profile for the region, which made it possible to size the solar plant and the storage on actual demand, and therefore to commit to the investment.

Due diligence Technical Due Diligence of a Solar Portfolio Independent technical review of a multi-site PV portfolio for an infrastructure investor. ›

The Project

A portfolio of solar PV plants owned by a developer and operator, reviewed on behalf of an infrastructure investment fund considering an investment in the company.

The Challenge

An investor pays for the energy the portfolio will produce over the coming decades. Plant performance, construction and O&M quality, equipment degradation and grid limitations all change that figure, and they differ from plant to plant.

The Analysis

• Verification of the energy yield estimates against measured production and performance ratio
• Review of availability, degradation and curtailment history
• Assessment of design, equipment and O&M quality, with site visits where required
• Identification of technical risks and their effect on expected production and cost
• Ranking of the plants within the portfolio

The Outcome

An independent technical opinion on expected production and risks, used by the investor in the valuation and in the negotiation of the transaction.

Design standard Removing the Contactor from Motor Feeders A design review showing that the contactor is redundant when the drive has Safe Torque Off, later adopted as the standard for all the plants of the company. ›

The Project

The motor feeders of a manufacturer of power plants. Each motor controlled by a variable speed drive was fitted with an additional contactor between the supply and the drive, following the usual practice of the sector.

The Challenge

The contactor adds cost, space, wiring and a component to maintain on every motor. If the drive already provides Safe Torque Off (STO), the question was whether the contactor still performs any function that the drive does not.

The Analysis

• Review of what a contactor is designed for under IEC 60947-1: operational switching, with no short-circuit capacity
• Review of what STO does: it removes the torque on the motor at once, and corresponds to stop category 0 under IEC 60204-1 and ISO 13850
• Analysis of how a motor under a drive is started and stopped, and of the warnings of the drive manufacturers against using a contactor on the drive input for this purpose
• Definition of the maintenance and isolation practice: a breaker or disconnector, never the contactor or STO alone, and an STO circuit with two independent contacts

The Outcome

The contactor was removed from the motor feeders. The solution was established as a company design standard in 2015 and has been applied to all the plants built since.