The Utilization of Thermal Energy Storage in Turbine Inlet Air Chilling Applications

The Stellar Group installs the world largest man-made Thermal Energy Storage Tank in terms of capacity in one of its Turbine Inlet Air Chilling projects in Saudi Arabia

By Mohammad G. Abusaa, The Stellar Group

Turbine Inlet Air Chilling is a process that involves cooling down ambient air entering a gas turbine to a desired tem-perature. By doing so, the gas turbine is able to produce extra power because of the associated higher density of air at lower temperatures. Chilled water, passing through coils, is usually used as the medium that cools the inlet air (see illustration below).

1) Ambient air entering the gas turbine 2) Coils with chilled water inside them 3) Cold air generated from passing through the coils 4) Cold air going into the turbine

Why Turbine Inlet Air Chilling (TIAC)? The inevitable worldwide growth in population and indus-try increases the demand for more power. Power compa-nies are therefore faced with the challenge of covering such demand especially during peak-demand periods. One way of solving this challenge is to maximize the utili-zation of gas turbines through Turbine Inlet Air Chilling.

The Turbine Inlet Air Chilling System installed in Riyadh supplies chilled water to 10 GE PG7111 (EA) gas tur-bines, their generators and oil coolers. The system in-cludes a 10,000 TR cooling plant with a 30,000m3 Ther-mal Energy Storage Tank that holds a cooling capacity of over 190,000 TR-HR.

Build and Burn During off-peak hours, the 10,000 TR cooling plant is utilized to fill the Thermal Energy Storage Tank with chilled water - BUILD. At the end of the off-peak daily period (usually 18 hours), the tank will have 30,000m3 of 7.5°C water in it. This volume of water is then utilized during peak hours (usually 6 hours per day) to cool down inlet air temperature to the gas turbine from 50°C to 13°C, inlet air temperature to the generator from 50°C to 30°C and maintain the gas turbines lube oil tempera-tures at 70°C - BURN.

The Hidden Turbine At this installation, the stored energy in the TES tank is the source for recovering over 150 MW of lost power during peak summer days while consuming less than 0.8% of that value to operate. Such enhancement is closely equivalent to two GE PG7111 (EA) gas turbines running at 15°C. Because of that, Stellar’s Thermal En-ergy Storage Turbine Inlet Air Chilling system (TESTIAC) was often referred to as the hidden turbine because of its equivalence to having two gas turbines on standby while not physically having them installed in the plant. A case study: Central Region, Saudi Arabia

In Saudi Arabia, the demand for more power increases in the summer season because of the high load associated with industrial, commercial and residential cooling sys-tems along with the efficiency degradation of power distri-bution systems because of heat. On average, the daily pe-riod during which power demand is the highest usually occurs in the afternoon between 1PM and 7PM. During that time, the ambient air temperature could reach 50°C. At that point, a typical gas turbine could experience up to 25% reduction in power production relative to its capacity at 15°C ambient. For a typical GE PG7111 (EA) gas tur-bine, this translates to more than 15 MW. Therefore, a power plant that has 10 gas turbines of that model would experience a loss of 150MW in a peak summer day. This could have serious effects on factories, commercial build-ings and homes especially if such loss causes a blackout. For that reason, Saudi Electric Company contracted The Stellar Group to install a Turbine Inlet Air Chilling System in one of its power plants in Riyadh. The system was run-ning in May 2005.

Thermal Energy Storage Tank in Stellar’s TIAC installation in Saudi Arabia

Mohammad Abusaa is the Middle East Regional Business Development Manager of The Stellar Group (Jacksonville, Florida) and can be reached at (904) 899 9849 or mabusaa@thestellargroup.com

12 December 2005