Combined Cycle Power Plant at a Glance – An interview which I have done with Mr. Dammika Nanayakkara for EESoc newsletter

Mr. Dammika Nanayakkara obtained BSc Eng Degree in Electrical Engineering with FIRST CLASS HONOURS from University of Moratuwa in 1995. He is a Four Years Coloursman of University of Moratuwa and was Captain of University Basketball Team in 1994. He was the First Vice President of EESoc. Mr Nanayakkara obtained MEng Degree from University of Moratuwa in 2001. After the graduation in 1995, he joined LTL Holdings (pvt) Limited (formerly known as Lanka Transformers Limited). Presently he is working as the Project Manager of 300MW Combined Cycle Power Plant, Kerawalapitiya. Mr. Nanayakkara is a Charted Engineer. He is a Corporate Member of Institution of Engineers (Sri Lanka), Institute of Technology (UK), and Institute of Electrical and Electronics Engineers (USA). This is an Interview with him.

1.) What are the specialities of this power plant comparing to the other existing plants in Sri Lanka?

Kerawalapitiya is a Combine Cycle Power Plant, which is a combination of Gas Turbines (GT) & Steam Turbines (ST). It produces 300 MW of Power (15% of Peak demand) with an annual contribution of 1800GWh (20%of National demand). The entire investment is 300 Million US Dollars. This plant has the multi-fuel capability and it can be driven from HFO (Heavy fuel oil), LFO (Auto Diesel), and LNG (Liquid Natural Gas). Now we are currently using low sulfur HFO (2% sulfur). That is because, HFO is the cheapest fuel available currently for Rs 42/liter. When it comes to the LFO, the cost is around Rs 70/liter. Therefore, the energy cost is Rs 9/kWh for HFO and 13.2/kWh for LFO. Hence it saves 10billion US dollars per annum to CEB and cost of the power plant is paid back within 3 years.

Configuration of this plant is 2+2+1. It means 2 Gas turbines and 2 Heat recovery steam generators and 1 steam turbine. First phase is open cycle and second is the combined cycle. Open cycle consisted on two gas turbines. And output was 200MW. That is in commercial operation since 11/2008. Then the combined cycle very recently included and another 100MW added.

Another specialty of our power plant is for cooling, we use seawater. Although we use sea water, it is not once through. We have a seawater cooling tower. However, if you take Norochchola power plant, it is a once through plant. Where, you do not have a cooling tower. For example, our water requirement is 250000 cubic meters per hour. But we take only 1000 from the sea which is used as the makeup water. For the rest, you have a cooling tower for the circulation. But if you don’t have a cooling tower, then we have to take entire 25000 from the sea. Due to environmental limitations, we cannot use ground water or we do not have the river water. Therefore, we use desalinated water for all our other needs (process water and service water). The technology we use is Reverse Osmosis (RO). We produce 70 cubic meters per hour for the process and service water requirement. We have our pump house on the shore and intake point is 400m off shore. You have to go to fairly a deep sea to avoid silt and debris coming in. Then we have around 1km pipeline coming to the power plant for this purpose.

Considering about this land, this is the famous Muthurajawela marsh. Therefore, any construction will have to come on pile. We have driven more than 1500 piles in this site in less than four months time. All the piles are 20m long going to the ground and 1.2m in the bedrock as well. Reclamation of the land had to be done by filling earth. We had to use 130000cubic meters of soil for that. We did the filling in less than one and half month. In addition, we have erected the equipment weight of 12000 tones and 1200 tones of pre-fabricated buildings. We have use more than 40000cubic meters of concrete.

2.) What are the major social and environmental impacts of this project?

Concerning about the emission for this plant, the heavy fuel oil that we use is 2% low sulfur heavy fuel oil. But the normal heavy fuel can have 3.5% sulfur. Due to the environmental dispersion modeling, we use 2% sulfur heavy fuel oil as they recommended. Dr. Saman Samarawikrama from University of Moratwa did the environmental modeling part of seawater dispersion modeling. In our environmental impact assessment, all the aspects are covered. Impacts on the air quality, impacts on the seawater, impacts on the ground water, traffic, social impacts, sound impacts and so on.

3.) Who are the equipment suppliers for this plant?

We have gone for the world renowned equipments. The reason is, we are running this power plant on IPP basis. Therefore, we have to maintain our reliability at a very high level. So we had to go for the best. Gas Turbine (GT) Package is from GE (USA/France), Steam Turbine (ST) Package is from GE (USA/France), HRSG and Steam System Package is from NEM (Netherlands), Power plant control system is from ABB (Germany), entire electrical balance of plant with medium voltage switch gear/ low voltage switch gear/ transformers are from ABB (Germany), Condenser/Cooling tower/ Cooling water system/ Seawater intake system are from SPX (Germany), and Seawater desalination system is from NALCO (USA).

4.) Who owns this company and what is the local contribution for the entire project?

The owner of the plant is West Coast Power (Pvt) Limited. Yugadanavi is the name of the power plant. Actually, Lakdhanavi wanted to do the power plant on Lakdanavi owned. But the foreign loan lending counties wanted the government guarantee for the loan. To fulfill that requirement West Coast Power company was initiated and now the West Coast Power is the owner of the project. Lakdanavi is the EPC contractor and OM contractor of the project. That is how West coast Power came in to the picture. Lakdanavi is also a part of West Coast Power (PVT) Limited.

Since Lakdanavi is a sri lankan company, all our designing, decision-making and entire work was done by our local engineers. When you buy the set of equipments, you have to integrate them in to a one big power plant. Therefore, that integration part is completely done under an engineering management of our engineers. We call Lakdavavi is the EPC and OM contractor of the power plant. EPC contractor means Engineering, Procurement and Construction contractor. This is the first time a local company did the EPC contract for any project of this nature. It was a big challenge and an enormous work. Other than moragahakanda reservoir in all other projects, foreign engineers do the EPC part.

5.) Who are the investors of this plant?

Employee’s Provident Fund, Employee’s trust fund, NSB (National Savings Bank), LECO (Lanka Electricity Company) and Lakdhavani Limited. In addition, the debt financier is HSBC bank from Hong-kong. This is the largest loan ever raised by a Sri Lankan company.

6.) What is the fuel supply system for this plant?

Fuel is supposed to come from Ceylon Petrol Cooperation terminal. But, at the moment this black oil is not available at that pipe line. Therefore, we are getting fuel from Kolonnawa by bowser daily. But, now they are laying a marine pipeline. It is still under construction. Then it will be directly from ship to the tanks.

7.) What will be the unit cost for this plant with the CCP and without CCP?

On average, the unite cost is around Rs 20.00. When it becomes combined cycle Rs 15.00. The capacity charge is around 120 million rupees per month.

8.) What is your personal opinion about the oil dominated power generation in Sri Lanka?

It is obvious that, we have to go for the cheap power sources. What is available right now is coal. My personal view is when we become really a developed country; we will need a capacity of more than 15000 MW. Until we reach the milestone of 10000MW, we should try to go for cheap sources. So the first is coal and the second is CCP. We are happy to say that, this plant is the first CCP in South Asia, which is running on cheap heavy fuel oil. Therefore, this is the next cheapest option. Then after the 10000MW, you can go for other luxuries, which are more environment friendly. Because, by that time, your buying power would very high. That is my personal opinion.

What is Reactive Power....???

Reactivevpower is an essential component of power all pervading in electrical system. When you look around, you will find reactive loads at work, supplying reactive power to the system and consuming reactive power from the system everywhere around you.

There are innumerable examples of reactive power phenomena that change the face of the world’s energy sector. Reactive power is required for transmit the active power, control the voltage and system and normal operations of power systems. Therefore, reactive power managing service is one of the most important ancillary services in electricity market currently.

What is reactive power? This is the first question we were asked at the Kothmale power station while we were having our in-plant training at CEB. Why we calculate average power for the active part and maximum power for the reactive part? Is it a strange concept? These are some of answers come to our mind. It is the imaginary part of the apparent power. It is a manoeuvre to explain the energy conservation. If one follows any textbook, the concepts of active and reactive power are as the product of the voltage and current measured at the same point. The active power based on the cos part and the reactive power based on the sin part wher

e the angle is taken in between the voltage and current. Is this classic explanation smart enough to sense you something about reactive power? That is why I thought about sharing something ease your mind regarding this manner.

Reactive power refers to the circulating power in the grid that does no useful work. This results from energy storage elements in the grid mainly from capacitors and inductors. Since it is a main part of voltage, it has a strong effect on the system voltages. Therefore, it must be well balanced in the system properly to prevent voltage issues and collapses. As we know, reactive power is present when the voltage and current are not in phase, which measured in volt-ampere reactive (so called VAR). Most of textbooks say it like this.

So most of us imagine the rectangled triangle and then hypotenuse to represent the apparent power and other two legs represent the active and reactive power. Can we explain even the basic behaviours and differences of the active power and reactive power from this hypothetical representation?

Here is a one mathematical model to understand the reactive power and its physical behaviours at a glance. Considering the instantaneous voltages and currents,

,

Using trigonometric we can modify this as,

In generally we call above two parts as instantaneous active power and instantaneous reactive power. As you can see in the graph, the active power oscillates around an average value while the reactive power oscillates around the zero axis. But it is not practical to work with instantaneous values as far as we can’t measure it. So they introduced the average power of the instantaneous power with rms values of V and I as,

This is the so-called active power equation that we have been already taught. Then what about the average power of reactive power? If you observed the equation carefully there is only a single sin term in the reactive power function. So the average reactive power is obviously zero. Then what is the reactive power measured in the industry as,

This is the maximum of the instantaneous reactive power that transfer to the net work. For our convenience, we have dropped the sin term of time here. This quantity measures the maximum reactive energy that flows through the device during a cycle and therefore we can get a good estimate of how much of energy is moving through the circuit even if the average reactive power is zero. What I am emphasising here is, there is no symmetry in the active power and reactive power terms as inferred in many textbooks. So P and Q have different meanings while P denotes the average active power and Q denotes the instantaneous maximum reactive power. So, P and Q cannot be treated on equal foot as they are not similar.

For the active power there exists a net flow from one point of the network to another. However, keep this in your mind. The zero average does not mean that no energy is flowing. The actual amount that is flowing for half a cycle in one direction is coming back in the next half a cycle.

Then what about the reactive power loss in the transmission lines? Well, as you already know, we cannot talk about a gain or loss in the reactive power scenario. This is just a loss in the amplitude of the instantaneous reactive power, which partially shares by the line impedance and other network elements. Therefore, the so-called loss in reactive power is not a real loss but rather a loss in the amplitude of the sending end reactive power. Reactive power does not travel very far. That’s why they ask to produce it close to the place where it is needed.

Therefore the so-called loss in reactive power is not a real loss but rather a loss in the amplitude of the reactive power as no reactive energy is lost. Shunt capacitors, Synchronous condensers, Synchronous generators and Static VAR compensators are some reactive power supply mechanisms.

Upper Kothmale, the latest member of hydro power (An interview I have done with Mr. Shavi Fernando)

Mr. W. J.S.L Fernando graduated from University of Moratuwa in Electrical Engineering in 1978, and holds an M.Eng from Asian Institute of Technology in Energy Technology. He initiated his career as a shift charge engineer at Kelanitissa thermal complex. Within the following 20 years he had held a variety of posts in Thermal complex, Energy Unit and Environment and Generation Planning. He is also a representative fellow of IESL Executive Council. He has published many papers, publications and has partaken in numerous overseas seminars and training sessions.

Currently he works as the Project Director of Upper Kothmale Hydro Power Project. The following is an interview with him on the progress of the said Project.

1.) Where is the Upper Kothmale Hydro power project located?

This Upper Kothmale Hydro Power project site is located in the South central mountainous area of Sri Lanka. The water of the Kotmale oya will be diverted from the head pond through the intake. There the water enters into the headrace tunnel which is about 13 km long. It conveys the water to the powerhouse cave, through the penstock, where two Francis turbine units to be installed yet. This underground powerhouse is located nearby Niyangandora village which administratively belongs to Kotmale Divisional Secretary’s Division. After the turbines, water will be conveys to the existing Kotmale reservoir via a tailrace tunnel.

2.) What are the important milestones of the project?

1985 – 1987 – Feasibility study under the Japan International Cooperation Agency (JICA) technical assistance.

1992 – 1995 – Overseas Economic Cooperation Fund (OECF) of Japan funded the Conceptual Design, Environmental Impact Assessment and the Final Design.

2000 – Secretary of the Minister of Forestry and Environment gave final clearance to implement the project subject to the strict adoption of the proposed mitigation measures in accordance with National Environment Act No. 47 of 1980. (Amendment Act No. 56 of 1988).

2002 – Loan agreement between the Government of Japan and Sri Lanka was signed.

2003 – Central Environment Authority (CEA) appointed Environment Monitoring Committee to evaluate the implementation of the proposed mitigation measures by the CEB.

Electric Power Development Company Limited, Japan (J. Power) was appointed as Project Consultant.

3.) A brief description about the water falls affected?

Only St. Clair’s fall is affected by this project and it is proposed to release water intermittently 10 times a day to retain its natural beauty with a peak flow rate of 6.6 m³/s. 98% of the time this commitment can be met.

4.) Apart from Electricity, what are the other benefits of this project?

This project will provide more and more benefits during its installation and operation phase. While the local social benefits have been largely confined to the areas around Thalawakale town, Pundalu oya and Kothmale, the wider benefits of watershed management will extend to the whole of the upper basin.

So at the current installation phase, it has stimulated the local business growth with opportunities created by the construction activities. Skilled construction labours, Unskilled labours, Domestic staff, canteen staff and other residential facility support staff are some examples for the employment opportunities that are being provided by the project.

The project will provide the opportunity to make significant improvements to the social and economic environment of the local communities while it is on the operational phase. The business community also expects certain benefits due to local tourism from the reservoir landscape, attracting people to use restaurants and other facilities in the town. The project will furnish infrastructure development including roads, bridges, culverts, electricity, telecommunication, water supply and garbage disposal facilities. These improvements will certainly enhance.

5.) How does the environmental protection take place?

Prior to commencement of construction activities in 2003, a Comprehensive Environmental Management Plan (EMP) was prepared. This EMP served to provide supporting information to the tender process so ensuring that the environmental responsibilities of the contractors are known from the outset. An Environmental Management Office has also been established and it forms part of the project management office. The EMO is staffed by an Environmental and Resettlement officers.Environment inspections are often carried out by a team comprising environment representatives of the employer (CEB), consultant (J. Power) and contractors to ensure compliance with EMP requirements. In order to evaluate the implementation of the proposed mitigation measures in the EIA report the Central Environment Authority has appointed and Environment Monitoring Committee (EMC) in accordance with the Gazette extraordinary No. 1283/19 of April 10, 2003.

6.) What is the role of Environment Management office of Upper Kotmale Hydropower Project towards the safeguard of the environment?

Majorly it has to monitor the quality of air, noise and vibrations at construction sites. Further the surface water quality monitoring of stream of the projects area should be done monthly. They have to implement the recommendations of bio-diversity assessment which conducted by the IUCN about the streams impacted by the project. They will be doing a Ground water level and surface water discharge monitoring program along the tunnel route on a weekly basis. They should continue a Standardized photographic record of St. Clair’s waterfall on a monthly basis.

7.) What are the major features of resettlement?

All settlement will take place within the Talawakelle town limits and hence within an acceptable distance of their original settlement areas. Each individual sub-community will be offered the opportunity to resettle together in a clearly defined area, avoiding community fragmentation and maintaining ethnic balance and existing social networks. And also the all households will be provided with housing and services that are significantly better than their pre-settlement conditions. The settlement plan will be prepared through a process of consultation with the local communities and with the re-settlement committee.

8.) What are the direct benefits to the affected households?

The policy of the Upper Kotmale Hydropower Project is to provide alternative houses in lieu of all affected houses. Floor areas of mostly affected houses are less than 300 sq.ft. Some of the affected houses are semi-permanent and without even basic facilities such as electricity, pipe-borne water and proper access roads. A large number of householders do not possess any legal titles to the land on which the houses are built. There are encroachers on the State land.

The project under its Resettlement Policy treats all the affected households who were in occupation before the cut-off date of June 22, 2001 irrespective of whether they possess legal titles on the land or not.

The project has made arrangements to provide affected households with alternative houses with larger floor areas with much improved facilities such as electricity, pipe-borne water and better access roads. Also the affected common amenities such as kovils, creches, playgrounds etc. will be reconstructed at the new re-settlement sites, by the project.

9.) What are the major sections of the construction management?

Project is the broken down to five lots for easy management.

Lot 1- Preparatory works – contract was awarded in 2005

Lot 2- Main Civil works – contract was awarded in 2006

Lot 3- Hydro Mechanical works – contract was awarded in 2007

Lot 4- Electro Mechanical Generating Equipments – contract was awarded in 2008

Lot 5- Transmission Line

Construction of new access road with drains, culverts and bridges, construction of a new bridge (83m length) across Kotmale Oya at Talawakelle, widening and improving existing road Talawakelle – Tawalantenna of 33 km, construction of all resettlement sites( 495 houses, 33 shops, 6 workshops, six libraries, two churches, 3 kovils), and construction of new school (Talawakelle Tamil school) of five buildings with modern facilities such as auditorium, canteen and quarters for the principal are comes under theLot 1 preparatory works. Further the construction of three storied Urban Council building with all facilities, construction of modern buildings for rest house, playground and cinema hall in keeping with standards of film corporation and construction of New 32 km, 33 KV double circuit distribution lines are also comes under this lot. This lot is completely finished.

Construction of concrete gravity dam (Length – 157 m, Height – 35 m, Width – 7 m), Construction of Tunnel ( Length – 12.9 km, diameter – 5.8m/4.5m), Construction of Surgetank (12 m diameter. and height 94 m), Construction of the underground power house complex and switchyard comes under the work of Lot 2 Main Civil works.

Design and installation of Spillway Radial Gate, stop logs, trash racks, embedded tunnel steel liners, embedded steel penstock, discharge facility for St. Clair waterfall comes under the work of Lot 3 Hydro Mechanical works.

Design and installation of turbine, generator, power transformer switchyard equipment, power plant equipment, expansion of Kotmale 220 KV switchyard, expansion of 33 KV Nuwara-Eliya grid substation and flood forecasting system comes under the work of Lot 4 Electro Mechanical works.

Design and construction of 17.5 km length 220 KV double circuit transmission line between Upper Kotmale switchyard and Kotmale switchyard is comes under the Lot 5 Transmission Line work.

Except Lot 5, the other lots have been awarded in the period of 2005 to 2007. Under the Lot 5, transmission line profile survey is completed and bidding documents are under preparation.

The total construction will be finished by august in 2011.

10.) Is it achievable?

Absoluitly, yes.

11.) Can you comment about the principal features of this project with some statistical data?

This project is a Run-of-river type with a regulating pond. Concerning about the water level, the full supply level (FSL) is 1,194 mmsl, minimum operating level (MOL) is 1,190 mmsl and normal tail water level is 703 mmsl. (mmsl – meters above mean sea level)

Effective strong capacity is 0.8 million cubic meters and reservoir area is 0.25 KM2. The maximum plant discharge will 36.9 m3/s. Concerning about the water head the maximum gross head is 491m and net head at full operation is 473m. As you know the installed capacity is 150MW with 75MWx2 generators and the plant factor with 30%.

12.) What is the Project investment cost and what is the estimated cost of Generation?

The total project cost is 384 million US Dollars with total local investment of 87 million US Dollars. And the loan amount is 297 million US Dollars of an interest of 0.95 percent per annum with a grace period of 10 years. So the re-payment period is 30 years (Excluding the grace period).

When we move on to the Estimated Cost of Generation for the 1^st 10 years from commissioning, the Capital Cost is 0.65 Rs./kWh with an operational and maintains cost of 0.25 Rs./kWh. So that the total Cost is 0.90 Rs./kWh. From 11^th to 40^th year the capital cost will be 2.52 Rs./kWh with an operational and maintains cost of 0.25 Rs./kWh. So the total cost will be 2.77 Rs./kWh.