Yugadanavi Combined Cycle Power Plant is a 300 MW thermal power plant located in Kerawalapitiya – around 50 minutes north of Central Colombo. Commissioned in February 2010, the plant houses two 100 MW gas turbines and one 110 MW steam turbine – all from General Electric. The whole site is built on a 25 acre plot of land located close to the ocean, from which it gains water for cooling and steam generation. The $300M plant was financed by the government, supported through a $160M loan from HSBC.
Schematic layout of the powerplant.
I visited the plant on the 5th of January for a tour along with some rigorous physics lessons on the functionings of the entire system. I ended up spending around 4~5 hours exploring and eventually tiring the superintendent engineer who was my tour guide.
Firstly, I was taken into the boardroom with the lead engineer of the plant – Mr. Shakthi (ironic as the direct translation of his name is power). Even though he had a tight schedule and only spent 20 minutes with me, he went into great detail about the unorthodox design of the plant – which was extremely enticing.
Control room diagram on the power output from each turbine.
A combined cycle plant is designed exactly as it sounds – a combination of ‘cycles’ which produces electricity in more than one method. Yugadanavi is primarily a thermal power plant, burning one of 52 compatible fuels in its two GE gas turbines to generate around 200 MW of electricity. It was quite baffling to find out about the extensiveness of fuels available for just combustion – the usuals that come to mind are just diesel, petrol and kerosene. When I visited the plant, it was consuming Heavy Fuel Oil (HFO), a very thick and dark fraction of crude oil used primarily as fuel for large ships (the plant uses 9.2L of HFO per second!). The plant has historically ran on both Liquified Natural Gas (LNG) and Diesel up until the fuel crisis – which forced the plant to use HFO of which our oil refinery in Sapugaskanda has a surplus of. This is the primary generation of the plant, which makes up one cycle.
HFO is quite a tough fuel to ignite and requires a lot of processing before it is suitable for ignition. Yugadanavi has its own mini refinery, which mixes the HFO with water and heats it to around 100°C whilst vigorously spinning the mixture, causing pure HFO to separate from the clunky crude oil mixture shipped from Sapugaskanda. Combined with the almost 30,000,000 litre fuel storage capacity, this enables the plant to function standalone for around one month.
Two main untreated HFO storage tanks. Treated HFO tanks are pictured behind.
The second cycle takes up most of the massive facility – the steam generation cycle. The exhaust gas produced by the gas turbines is extremely hot – around 520°C. Instead of simply releasing this exhaust into the atmosphere as waste (as is the normal procedure), the gas is passed over hundreds of metres of large thermal tubing containing pure water. The result is that heat is transferred from the hot exhaust to the water – which eventually boils to form steam. This makes up the Heat Recovery System (HRS), which can be identified from the outside by the distinct, massive exhaust towers releasing the exhaust gas – which now has been reduced to 120°C. The HRS produces two types of steam – high density and low density, both of which are channelled along more massive tubing to the singular GE steam turbine, which generates another 110 MW of energy.
I could not stop thinking about the geniuses of such a dual system. In institutions, engineering is usually thought as a hard-science isolationist subject – but in reality, to be a good engineer demands much of the critical thinking skills we take for granted from more abstract jobs. Combining two completely separate systems to produce an orchestra rather than a choir – for the same trouble really opened my eyes. Optimization is a common term used in engineering – how to do more for less – and is thought extensively for to-be-engineers. But I realized that such thought is more a representation of the awareness of your surroundings and profuseness in your craft – not a subject which can be memorized.
GE Turbine & Generator compartment.
GE Steam Turbine – covered with a thick layer of insulation to prevent heat from the steam escaping.
The water for the HRS system is channelled directly from the ocean from a large 8 km-long pipeline – which undergoes several purification and desalination processes before it is used in the system. Yugadanavi has its own waterworks, which: removes sediments, fine particles, salt and filters the water in that order. The plant uses around 25,000,000 litres of water per hour for steam generation and cooling of plant systems.
Seawater treatment diagram.
One of the two large cooling towers for the used steam.
The inclusion of the second cycle increases the efficiency of the plant from 30% to just over 45% – as pent up thermal energy, which would have been simply released to the environment, is harnessed in the HRS.
I was given an extensive tour of the plant – ended up walking, crawling and climbing around 5 km that day. The highlight was definitely seeing the steam turbine in action – the two gas turbine rooms were way too hot for people to enter during normal operation. Even so, the steam turbine room clocked around 50°C as well. Unfortunately, I was limited in the amount of pictures I could take due to security concerns – but I definitely left with a deeper interest in the extreme engineering that enables us consumers to take electricity, the backbone of modern society, for granted.
Set-up transformer for electricity generated from the gas turbines, from here onwards it connects directly to the national grid.
Model of the entire powerplant.
