Power plant engineering

How do ancillary services assist energy and capacity markets?

2022-12-04T11:14:00.003+05:30

While purpose of energy markets is to deliver energy on a day to day basis as MWh, and purpose of capacity market to secure capacity in future as MW,

Purpose of ancillary services is primarily to maintain frequency

Frequency varies based on dynamics between supply and demand. If the demand increases (or supply reduces)- Frequency goes down, and in case demand reduces- frequency goes up automatically. Demand can increase for example in summer months, in day time many people switch on air conditioning at same time. Supply can reduce for example if due a situation many power plants connected to the grid stop working. This can also be due to case where grid is depending on renewable energy sources, for example solar farms may not function optimally on cloudy days.

Job of ancillary services is to ensure stable frequency is maintained at 50 or 60 Hz depending on the region, and frequency in the grid does not swing wildly depending on changes in demand and supply- with which grid will not be able to function. Ancillary services build up Inertia in the grid, with governor response. This is typically achieved with technologies such as gas turbine power plant.

What is difference between boiling and vaporization ?

2022-12-03T23:38:00.001+05:30

Differences are as under:

1. Scope of molecules : In boiling molecules of whole liquid go into vapor state. In vaporization only surface molecules go into vapor state

2. Energy required: Boiling requires external source to break molecular bonds. In vaporization heat gained from sorroundings is enough for surface molecules

3. Temperature: Boiling occurs only at boiling temperature. Vaporization occurs at all temperatures.

4. Interface: Boiling has a solid-liquid interface whereas vaporization has a liquid-vapor interface.

What is difference between Capacity Market and Energy Only Market ?

2022-12-02T19:57:00.001+05:30

In Capacity Market - Grid 'reliability' or 'capacity' is ensured by paying the participants to commit generation in years in future.

Energy-Only Markets: They pay generators only when power is provided on a day-to-day basis.

In general 'Wholesale' electricity markets have combination of both Capacity Market and Energy Only Market. In some rare cases with low electricity prices and high confidence in future availability, there could be cases where there are no Capacity Markets.

How much has CO2 concentration in atmosphere increased ?

2022-12-01T23:41:00.006+05:30

Below is some data gathered on CO2 concentration in Earth's atmosphere. The references are also listed.

As per IPCC report, warming caused by humans was approximately 1 deg C above pre-Industrial levels in 2017 [1].

And it will increase at 0.2 deg C per decade (high confidence) [1]. Also warming greater than global average has been seen in some regions, with higher average warming over land than oceans [1].

Global average atmospheric carbon dioxide in 2020 was 412.5 parts per Million (ppm) [2] against pre-Industrial levels (1750) of 280 +/- 10 ppm [3].

The present atmospheric CO2 concentration in atmosphere has not been reached during the past 420,000 years, and likely also not for the past 20 million years [3]. I personally find this fact quite astonishing!

Since 2000, global atmospheric carbon dioxide amount has grown by 43.5 ppm, an increase of 12 percent [2]

References:

1. Intergovernmental panel for Climate Change. (2022, May3). Summary for policy makers. Chapter1. Executive Summary. https://www.ipcc.ch/sr15/

2. NOAA Science & Information for a Climate-Smart Nation. Climate Change: Atmospheric Carbon Dioxide. https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide. Accessed on 22 May 22.

3. Intergovernmental panel for Climate Change. Report: The Carbon Cycle and atmospheric Carbon Dioxide. https://www.ipcc.ch/report/ar3/wg1/the-carbon-cycle-and-atmospheric-carbon-dioxide/

Why does water change phase ?

2020-12-06T17:40:00.003+05:30

As seen practically in daily life, water can exist in form of solid, liquid or gas (vapour state). But as obvious at it seems, water does behave in some surprising ways, taking different amount of thermal energy for different phase change applications, or even for increase in temperature for the same phase.

Now why it really happens, the physics behind it on a molecular scale we will try to figure out in this blog, without sounding too technical and trying to remain at a layman level , which is principally my purpose of this blog to help people understand concepts without burdening them with terms and formulae.

If we think of a constant pressure application.. like for example having pressure as atmospheric pressure at for example 40C, water exists in liquid phase. At this temperature water is just at ease with itself and not really looking forward to vaporisation. Now when we increase thermal energy input to water, like for example through adding heat energy through a burner, temperature of water keeps on increasing.

Now this temperature is nothing but increase in average kinetic energy of water molecules... As we add more heat , more energy is transferred to molecules and more they collide with each other like balls on billiard board... and hence more kinetic energy they will have, in the same sense of kinetic energy that we learned in school. With increase in this average kinetic energy, we see in our instruments that temperature is increasing.

This follows this logical pattern till water reaches temperature of around 100 C, when it seems it has made up its mind that it can vaporise now. But what we see here is that water starts vaporising, that is it changes state from liquid to vapour state, but somehow its temperature does not increase ! (remains fixed at 100C).

Logically thinking adding thermal energy into water should increase the temperature (average kinetic energy of molecules) too, but it seems all this additional thermal energy is going somewhere else rather than to change kinetic energy of molecules.

Now when we start to think of it, let's think what happens in water in vapour state, apart from more kinetic energy of molecules, the major difference against liquid state is that molecules are more far apart from each other. Its just like I am running a race with my Son, who is another molecule, and while our speed is increasing , distance between us is also increasing... which we can say we changed into gaseous state.

This state at 100C, at which energy goes into change to vapour state is called latent heat. Basically they called it latent heat was because it was "latent" in the sense this additional energy could not be detected by instruments through a temperature reading with the reasons explained above.

Now this temperature remains at 100C and our water will be in mix of two phases (liquid and vapour), till all liquid is converted into vapour state... or "steam" that is generally called in day to day life.

Then we have this steam (with molecules having high K.E. and long distances between molecules), is basically a high energy state, which in turn is used in daily life to drive many applications like turbines, power plants, heating applications etc.

In order to ensure that this steam does not condense back to vapour state, it is mostly "superheated" by adding more thermal energy to ensure it remains in steam/ vapour state and can be used to drive these real world applications.

Hope I could help to increase some of your understanding on this topic. Thank you.

Difference between pinch and approach temperature in a boiler / hrsg

2014-09-25T16:29:00.001+05:30

Pinch point: It is the difference in temperature of flue gas at evaporator outlet and water temperature at evaporator. The lesser the pinch point, more shall be evaporator surface area (as higher surface area would be required to absorb more heat from flue gas). The decision of pinch point should ideally be made keeping in mind overall costs and boiler efficiency.

Approach temperature: It is the difference in temperature between economiser outlet temperature and saturation temperature. Approach temperature should not be kept very less due to the possibility of steaming.

Types of cfbc boilers

2014-09-18T22:59:00.001+05:30

From a neutral perspective following are the types of cfbc boilers:
a) Cold cyclone CFBC: Called as cold cyclone because cyclone temperature is "colder" (approx 400 Deg C) than a hot cyclone cfbc, which is because of some heating surfaces in the first pass. Aim is to have bed temperature at around 850 Deg C to aid in desulphurisation.

b) Hot cyclone CFBC: Heating surfaces in the second pass, hence cyclone is hotter.

c) Compact cyclone CFBC: Cyclone is part of pressure part circuit, done to reduce bed temperature.

d) U beam CFBC: U beams used instead of cyclone for filtering out coarse ash. Similar in nature as hot cyclone cfbc.

ASME Stamp

2014-09-15T21:57:00.001+05:30

ASME Stamp is applied in shops of pressure parts, piping, valves, instruments in the water steam cycle path.
For a master stamp to be applied on hrsg/boiler it has to be ensured that the etection contractor is asme authorised.
ASME stamp is generally accepted throughout the globe, with the notable substitutes being CE marking in Europe, GOST certification in Russia, IBR in India.

HRSG Harp

2014-09-10T16:39:00.002+05:30

While working on HRSG for some years i one day thought why on earth is a HRSG pressure part called as harp.. and a simple google search gave me the answer, it is actually like a classical harp instrument!

Image Courtesy: Wikipedia

Concept of Nuclear power plants and Uranium

2011-11-10T20:03:00.001+05:30

Concept of Nuclear power plants and Uranium

- Natural uranium contains 0.7% U 235. Uranium with an increased concentration of U 235 is called enriched uranium.

- Nuclear weapons require uranium enriched to 90% or more U 235. Fuel used in nuclear power plants use Uranium enriched to 3-5% U-235.

- U235 is the only isotope that is found in nature which can be fissioned by thermal neutrons.

- Natural Uranium has 99.284% 238U isotope and 235U constitutes 0.711% of its weight.

- Percentage composition of U235 is increased through isotope separation.

- Highly enriched uranium is mostly produced for nuclear weapons, naval propulsion and a small quantity for nuclear power plants out of the total 2000 Tonnes.

- Depleted Uranium: 238 U remaining after enrichment. It is less radioactive than natural uranium. Presently 5% in use for armor penetrating weapons as it is highly dense.

Facts about Hydroelectric Power plants

2011-11-09T21:38:00.000+05:30

Facts about Hydroelectric Power plants:

- It generates 24%of world's electricity
- Approximately 2000 hydroelectric power plants operating in United States
- Turbine that is most often used in hydroelectric power plants is Francis Turbine.
- More the water flow and head, more will be electricity generated.
- Hoover dam in USA generates 2000 MW consisting of 17 generators each generating 133 MW at Nevada, Arizona.
- Biggest hydroelectric power plant is Itaipu power plant jointly owned by Brazil and Paraguay. It produces 12,600 MW. Second largest hydroelectric power plant is Guri power plant at Caroni river Venezuela generating 10,300 MW.
- Largest hydroelectric power plant in USA is Grand Coulee at Columbia river in Washington. It can produce 7,600 MW.

Some nice facts about coal

2010-09-27T22:05:00.000+05:30

Some nice facts about coal

- Some coals after release of volatile matter become soft and pasty and form agglomerates. They are called caking coals. Extent of caking of coal is determined by swelling index. On the contrary, free burning fuels have high swelling index, expand in volume during combustion.
- Grindability index is inversely proportional to power required to grind coal. Grindability of a standard coal is defined as 100.
- Phosphorous in coal should be <0.01% as it can react with iron to form hard, brittle iron phosphide.
- Sulphur occurs in coal as a) Pyrites: FeS2 b) Organic sulphur coupled with carbon atom of coal molecule. c) In form of gypsum Ca SO4.
- Fixed carbon in proximate analysis is a hypothetical term and not a precise constituent of fuel. It is obtained from subtracting from 100 sum of % of moisture, volatile matter and ash content of fuel sample.
- Moisture can be present in coal as surface moisture(Formed during washing, scrubbing of coal), inherent moisture(Absorbed moisture through water absorbed in capillaries in coal), Combined moisture
- As moisture increases, free hydrogen for combustion decreases as 1/8th of weight of oxygen content is consumed as moisture.
- Organic Sulphur is inseparable from coal. Only pyritic sulphur can be removed.
- Basic contents of volatile matter are a) Gases containing: CO, H2, CH4, C2H6 and H2S
b) Tar: Complex mixture of benzene, toluene, napthalene, xylene, phenols, free carbon, anthracite and cresols.
c) Ammoniacal liquor: Aqueous condensate of nitrogen and sulphur compounds plus cynides.

Heat rate of a reheat turbine

2010-03-30T21:07:00.000+05:30

Heat rate of a reheat turbine
= ( ( Main steam flow at ESV inlet x (Enthalpy of main steam - Enthalpy of feed water ) + ( Reheat steam flow x ( Enthalpy of hot reheat - Enthalpy of cold reheat ) ) ) / New power output in MW.

Steam turbine

2010-03-30T21:04:00.000+05:30

Steam turbine shaft vibration is calculted as per ISO 7919.

Plant heat rate

2010-01-31T22:04:00.000+05:30

Plant heat rate = Turbine heat rate / Boiler efficiency

Heat rate of steam turbine

2010-01-31T22:01:00.000+05:30

Heat rate of Steam Turbine = Steam Flow at Turbine inlet x (Enthalpy of steam at inlet to turbine - Enthalpy of feed water at HP heater outlet) / MW generation

Unit of heat rate = kcal/kWhr

India Power- December 2008 Statistics

2009-03-13T13:34:00.000+05:30

Total power generation increased by 1.53% in December 2008 as compared to December 2007
%age increase in thermal and nuclear generation = 3.36%
%age increase in hydel generation = 10.58%
Total power generation 50.14 billion units.
Share of central sector --> ~ 25 billion units
Share of state sector -- > ~ 29 billion units

Coal as a fuel

2009-03-11T15:23:00.000+05:30

Worldwide, coal is right now the most widely used primary fuel, accounting for approximatley 36% of global electricity production. It is expected to remain same till at least 2020.
----> South Africa:
- About 77% of country's primary energy needs are provided by coal.
- Produces an average of 224 million tonnes of marketable coal annually.
- 5th largest coal producing country in the world
- Coal reserves expected to be 53 billion tonnes
----> India:
- Around 63% of electric generation through thermal power (90,000 MW of 1,41,000 MW)
- Indian Coal is generally with low GCV, high ash content.

Capacities

2009-03-07T16:28:00.000+05:30

----> Total installed power plant capacity in World: 28,12,000 MW
----> Total installed power plant capacity in India: 1,41,000 MW
----> % of Nuclear power in Total installed power stations in world: 14%
----> % of Hydor-electric power power plants in Total installed power stations in world: 24% (Around 6,75,000 MW)
----> Total installed power plant capacity in US: 5,00,000 MW
----> % of Nuclear power power plants in Total installed power stations in US: 20% (Around 1,00,000 MW

----> Largest Hydro-electric power station in the world: Itaipu power plant, Jointly owned by Brazil and Paraguay, producing 12,600 MW
----> Second largest Hydro-electric power station in the world: Guri Power plant, Caroni River Venezuela, producing 10,300 MW
----> Largest Hydro-electric power station in US: Grand Coulee power station, Columbia River, Washington, producing 7,600 MW being upgraded to 10,080 MW.

Hydropower

2009-03-04T16:05:00.000+05:30

Hydropower
---> 24% of world's electricity
Combined total of 6,75,000 MW
More than 2000 Hydroelectric power plants operating in United states
Largest Hydroelectric power plant: Itaipu Power plant, Jointly owned by Brazil and Paraguay, can produce 12,600 MW.

Nuclear Power

2009-03-04T15:16:00.000+05:30

Watts Bar1: Came online on Feb7 1996, last commercial nuclear reactor to go on-line.
----> Quoted as evidence of succesful worldwide campaign of nuclear power phase-out.
In US, 104 nuclear plants generate 1,00,000 MW approximatley 20% of nation's total electric consumption.
---->It's the largest suppier of nuclear power.

Calculate fuel flow

2008-12-03T11:00:00.000+05:30

Fuel flow to a boiler is calculated as,

Fuel flow = (Heat duty x 1000 x 3.6) / (4.2 x GCV x Efficiency /100)

Dulongs formula for GCV calculation

2008-09-04T16:46:00.000+05:30

If we know the ultimate analysis of fuel, we can easily calculate its GCV.
The basic principle is that there are only 3 components in a fuel which generate heat. These are:
Carbon, Hydrogen and Sulphur.
According to Dulong's formula gross calorific value of a fuel is;
GCV = ((35.5 x C + 114.8 x H + 9.5 x S – 14.5 x O) x 1000) / (100 x 4.1868)
Each multiple of carbon, hydrogen and sulphur represents heat generated by its one mole.
The formula gives GCV in kcal/kg. Simple isnt it !

Boiler Heat Duty

2008-09-04T16:44:00.000+05:30

Boiler heat duty = Tonnes per hour of steam generated x (Enthalpy of main steam - Enthalpy of feed water)

Various systems of a coal fired power plant

2008-09-04T16:06:00.000+05:30

•Coal Handling System: Consisting of crushers, conveyors, belts etc.
•Water treatment plant: Consisting of RO system, cation and anion exchangers, DM system, mixed bed system.
•Boiler package: PF, AFBC, CFBC etc.
•Turbine package: Consisting of turbine, generator, condensor (Air cooled or water cooled)
•Condensate system: With water cooled or air cooled condensor.
•Plant air system: Consisting of compressors, receivers
•Ash handling system: Slurry system or dense phase pneumatic ash handling system
•Electrical system including generation and distribution: Consisting of busbars, transformers, circuit brakers, MCC etc.
•Control and instrumentation along with DCS.: Consisting of transmitters, guages, PLC, DCS with the associated communication cables.
•Civil: With or without piling
•BOP package ( Air conditioning, ventilation, fire fighting, Public address system, plant illumination)