MeeFog Boosts Power Output by 15% at Sahara Power Station | APR Energy Case Study

Overview

APR Energy, a fast-track mobile turbine power provider, was contracted by the General Electric Company of Libya (GECOL) to help address a national power shortage. The company needed to quickly bring generating capacity online at a remote power station in Samnu, in the Libyan Sahara, using mobile gas turbines that lose significant output in extreme desert heat.

Libya, with a population of just six million, holds the world’s ninth-largest proved oil reserves (48 billion barrels) and Africa’s fourth-largest proved gas reserves (55 trillion cubic feet), accounting for about 95% of its export earnings, 80% of its GDP, and 99% of government income.

There had been a lack of infrastructure investment in capital equipment during Muammar al-Gaddafi’s 40 year rule. – explained Tom Michaud, Project Manager for APR Energy

Despite this potential for prosperity, decades of underinvestment left the country’s power generation and transmission system overtaxed and prone to rolling blackouts. The new government sought to close this gap starting in 2012, when Electricity Minister Ali Muhairig turned to leasing bridging power from APR Energy to add capacity within months.

To recover the output lost to extreme desert heat without relying on scarce local water supplies, APR Energy installed MeeFog inlet air fogging systems on each turbine at the site. During testing, the MeeFog system improved gas turbine output by as much as 15%, while using half the water that traditional combustor water injection would require.

Customer Profile

APR Energy, based in Jacksonville, Florida, began operations in 2004 after cofounders John Campion and Laurence Anderson purchased the Alstom Power Rentals subsidiary of Paris-based Alstom Power.

The company provides large-scale, fast-track mobile power solutions for seasonal peak demand or bridging power during new plant construction. In 2013, GECOL and Libya’s Ministry of Electricity and Renewable Energy contracted APR Energy to help address a power shortage in Libya.

Technical Details

• While gas-fueled and water-injected, the FT8 turbines can generate more than 24 MW at 5°C (40°F)
• Output drops below 20 MW at 45°C (113°F), a typical summer temperature at the site
• Over that same temperature range, heat rate rises from 10,000 kJ/kWh to nearly 11,000 kJ/kWh
• The fogging system at Samnu was designed for an ambient dry bulb temperature of 45°C (113°F) and a wet bulb temperature of 20°C (68°F), a difference of 25°C (45°F)
• The system uses 14 fogging stages, each providing roughly 3.5°F of cooling
• The full system delivers the desired 45°F of cooling, plus one stage of overspray

What Was the Strategy MeeFog Used

Each turbine at Samnu was equipped with a dedicated fog pump skid consisting of three pumps and two motorized ball valves. These pumps operate in sequence to provide fourteen stages of fog output, each through 24 operating nozzles.

A weather station monitors temperature and relative humidity and sends that data to a programmable logic controller (PLC), which also connects to the turbines’ distributed control system (DCS) to receive data on inlet air volume. Based on ambient conditions and air volume, the PLC determines how many of the 14 fogging stages can be activated without exceeding the target set points.

APR Operations observed that MeeFog could provide the equivalent amount of power boost as the water injection system while consuming almost half the amount of make-up water,” says Michaud. “The quantity of water saved by not running the water injection system while maintaining the required power boost will significantly increase the overall life-cycle of the demin water system and its associated filters and mixed beds.

Operators can set the desired amount of overcooling or undercooling relative to saturation. Set points above 100% cause the fog system to inject more water into the airstream than can be evaporated under current ambient conditions. The excess water droplets, known as overspray, are carried into the compressor section, where the heat of compression evaporates them and further boosts power output.

Key Outcomes

• Recovered lost turbine output caused by extreme ambient heat at the Samnu site
• Boosted gas turbine power output by as much as 15% during testing
• Cut water consumption roughly in half compared to traditional combustor water injection
• Extended the service life of the demineralized water system and its filters and mixed beds by reducing water injection demand
• Delivered a power boost of approximately 3 to 4 MW per turbine, running up to 100% of the time depending on ambient conditions

“Depending on ambient conditions, the fogging systems can run 100% of the time to maintain the desired increase in output. By using the MeeFog system, APR experienced a power boost of approximately 3 to 4 MW per turbine.” – Tom Michaud, APR Energy Project Manager