Exactly. Your last diagram shows power and heat utilization but it does not have the combined cycle power plant? Any reason why not?
I see one big problem with this whole concept which is the availability of gas. Pakistan is running out of the its natural gas reserves. So this will need to be imported from countries such as Iran, ME or central Asia. Can we do a rough calculation that how much gas will be needed if multiple such trigeneration power stations are setup in each city? I am thinking depending on the demographic, a city could have at least four of these facilities?
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Basically the large combined cycle plants have a steam cycle in addition to gas turbines, in order to increase efficiency. If their waste heat is used for say district heating or other industrial purposes, they would be called co-generating plant. But trigeneration systems are usually small, you can even fit them on roof tops or in basements of buildings. They have only a gas turbine. There is no steam cycle, so the waste heat either goes to be used on its own or be used for generation of cooling.
You are right that Pakistan is short on gas but as you noted, it can be imported. About the calculation for the gas, it is complicated. You see, till now we were talking about peak demand and meeting it. What you are talking about now is basically total consumption. As you know you are not peaking all the time during the whole year. Max peak times usually come in early evening and at the middle of the day on a very hot summer day. But the power consumption say in the middle of the night when almost everyone is asleep in autumn or spring is going to be much less. You are not all the time maxing out your generation capacity.
And then how do you define the consumption? Say a trigeneration plant, supplying a community, is providing it with airconditioning, heating as well as electricity. But if there was no trigeneration plant, the same community would be using way more electricity, more than double or even tripple in order to use air conditioning and heat. So it also depends on what kind of electricity generation method you are using. A community being supplied by solar or wind or hydro needs way more electricity than a community being supplied by trigeneration.
But I do a back of the envelope calculation for you here, just for illustrative purposes.
As per World bank Pakistan's percapita electricity consumption is 450 KWh.
Let say, we assume airconditioning and heating be considered as part of electricity in trigeneration. Let's also assume the efficiency of trigeneration is at 80 to 85% level.
Under such conditions if we want to double Pakistan's electricity consumption per capita from 450 KWh to 900 KWh, we would need to provide extra 450 KWh to each person in the country on average. This would be a huge improvement for living standard of people since they would be using twice more power as they are now. So for a population of 200 million this will come to 90 TWh (terawatt-hour) per year of extra power to allow this improvement in living standard.
If you went ahead and produced all this power from tirgeneration, you would need 10 billion cubic meters of natural gas per year (about 25% of the capacity of IP gas pipeline or 40% of total capacity of TAPI). If you wanted to import all of it, then this will come to 27.4 million cubic meters of gas or about 20 thousand tonnes of LNG per day on average.
As per
this price report, importing this much gas in current market conditions, would cost:
IP pipeline: 1.8 billion dollars per year
LNG: 2.5 billion dollars per year (not including the cost of ship transportation, storage/transportation evaporation losses and re-gasification which is about 10-15% additional cost).
TAPI: 2.13 billion dollars per year (not including royalty transit fee to be paid to Afghanistan which is about 10% additional cost).
