CE70035 - CCS and Energy Production Flashcards
What do FOAK, CCGT, and OCGT represent?
FOAK = First of a kind
CCGT = Combined / Closed Cycle Gas Turbine (gas turbine associated with steam cycle)
OCGT = Open Cycle Gas Turbine
What is Cost of Lost Watts?
What are the issues?
The cost of not having electricity available when you need it.
Whilst it may be cheaper to generate electricity from solar in some circumstances, it is necessary to have energy storage available.
The cost of a “lost” kWh (i.e. not having electricity available when you need it) is a lot more than the cost of generating the power.
How does energy supply vary for different energy resources?
Wind (zero fuel cost, switches on and off as the wind blows)
Nuclear = baseload (fuel costs very little compared to capex)
Fossil – relatively quick to run up and down, but not good from a cold start. (OCGT faster than CCGT faster than coal)
Hydro - very quick response, limited capacity
This is why you need a number of different power generation technologies – they each have different characteristics
What are the largest industrial contributors to GHG emissions?
Iron and steel largest single sector by emissions
•Five main sectors considered responsible for 63% of industrial emissions are iron & steel, cement, aluminium, chemical, and paper.
•Different technologies are more appropriate in some industries compared to others
•Some sectors produce high partial pressure / purity CO2 and are therefore easier to capture from.
What are the types of CCS?
- Post-combustion capture
- Pre-combustion
- Oxy-combustion
What happens in post-combustion CCS?
Exhaust gases with with CO2 are scrubbed by solvent. The CO2 rich solvent then passes through a solvent regeneration column, and the CO2 is compressed and stored.
What happens in pre-combustion CCS?
At energy plants, following gasification reactors, gases containing COx pass through reforming and shift reactors to produce CO2 and H2.
This undergoes separation processes where hydrogen is sent to power plants and CO2 is compressed for storage.
What is oxy-combustion CCS?
Oxy-fuel combustion is the process of burning a fuel using pure oxygen, or a mixture of oxygen and recirculated flue gas, instead of air. Since the nitrogen component of air is not heated, fuel consumption is reduced, and higher flame temperatures are possible.
Because oxyfuel combustion results in flue gas that already has a high concentration of CO2, it makes it easier to purify and store the CO2 rather than releasing it to the atmosphere.
What factors effect energy decoupling?
Decoupling refers to the disassociation of a utility’s profits from its sales of the energy commodity.
The decoupling trend is explained by at least four factors:
- energy efficiency improvements
- saturation in the ownership levels and improved efficiency of the main domestic appliances
- the unresponsiveness of certain industrial uses, like space heating, to long run output growth
- a structural shift away from energy intensive activities (such as steel making) towards low energy industries (such as services).
Note: this often implies manufacturing off-shoring!
What is energy decoupling?
In public utility regulation, decoupling refers to the disassociation of a utility’s profits from its sales of the energy commodity.
Instead, a rate of return is aligned with meeting revenue targets, and rates are adjusted up or down to meet the target at the end of the adjustment period.
This makes the utility indifferent to selling less product and improves the ability of energy efficiency and distributed generation to operate within the utility environment.
What are IAMs?
Integrated Assessment Models (IAMs) are sophisticated tools that combine elements of natural science, economics, technology, demographics, and policy to understand complex interactions within human and natural systems.
A large time-dependent model, which marches forwards in time with sub-models of (in this case)
- time-dependent energy demand, pricing, etc.
- features of different energy supply technologies (capital cost, operational cost, ramp rates, CO2 emissions, fuel cost) etc
- any energy storage on the system
- almost all models assume some form of cost reduction with time through learning
They integrate multiple disciplines to produce an overall model.
By substituting the “allowed” technology types / rates of progress in their development, it is possible to explore (say) which technologies are critical to develop, and the effects of different constraints (say, how much biomass is available)
IAMs help policymakers and researchers explore different future scenarios, assessing trade-offs and synergies between different sectors and policies. By considering the interconnectedness of these systems, IAMs provide insights into the most effective pathways for achieving sustainability and addressing global challenges like climate change.
What are disadvantages of IAMs? (Integrated assessment models)
- challenging to get risk profiles correct
- poor basis of information
- Will not necessarily choose the “best” path, can choose a pathway which is sub-optimal based on what is best at a particular time
Why do IAMs choose CCS?
- CCS can be integrated into an existing energy system without making large changes to the overall system.
- Renewables tend to become more expensive to the system at higher penetration rates (their intermittency impacts more on the system as a whole).
- If the system includes industrial sources of CO2, CCS is one of the only ways of decarbonising these emissions.
- There are some other emissions that are exceptionally expensive to decarbonise (say air travel). Once the cost of decarbonising the emission at source is more than the cost of BECCS, the system will choose BECCS
What do LCOE and VOTA stand for?
Levelised Cost of Electricity
Value of Technology Addition
What are examples of unconventional oil?
Tight oil (or shale oil) – oil that is trapped in shale rocks. Forms much the same as conventional oil, but is not mobile within the rocks. Needs to be hydraulically fractured to get the oil out.
Oil Shale - rocks that contain kerogen but which have not been heated in the past and so have not matured to produce oil. Pyrolysis of the oil shale produces a synthetic crude oil. Frequently considered for potential fuel production when the cost of crude oil becomes very high – but bad environmental credentials
Oil Sands (tar sands) – a mixture of extremely heavy oil (bitumen) with sand. Huge deposits in Canada and Venezuela (Canada has more oil in oil sands than the rest of the world put together has oil). Questionable environmental credentials. Different methods exist to enhance production (though many areas are simply strip mined), many relying on advances in directional drilling.
What are the conventional ways of mining coal?
Deep mines (pits)
Open-cast mining. (Digging down to the deposit from the surface, remove the overburden (the stuff above that isn’t coal) and dig out with a digger. Much cheaper than deep mining)
What are unconventional methods of obtaining hydrocarbon gas?
Fracking
Gas hydrates – vast stores of methane, stored in ice-like molecular cages. One of the largest sources of hydrocarbons available.
What are unconventional means of obtaining coal?
Underground coal gasification
– Dig a hole down to an unmineable coal seam
– Drill another hole a little way away in the seam
– Drill through the seam (directional drilling again) and link the holes (you can also do it by hand if you want the world’s worst job).
– Pump down air or oxygen to the first hole, and set the seam on fire.
– The hot combustion products move through and gasify the remainder of the coal, produce syngas at the other hole.
How does Reserves compare to Resources?
Reserves = profitably recoverable using today’s resources and price.
Resources = how much is out there.
List main uses of fossils fuels:
Coal:
- Chemicals (area of growth) – gasification covered in separate lecture(s)
- Power stations, Iron and Steel (coking coal), Cement production. Can be substituted for in some areas by biomass.
- Some heating (being phased out)
Oil:
- Transport fuels (vehicles, aviation)
- Petrochemicals
- Some heating and power (being phased out)
Natural Gas
- Power production
- Limited Chemicals
- Heating
What is pulverised coal combustion?
The principal means of the generation of electricity from coal worldwide since the middle of the twentieth century
Technology for the large scale utilisation of coal (other solid fuels) for generation of power and heat
How does it work?
* A mixture of pulverised fuel (100 μm) and air is injected into the combustion chamber (boiler)
* Combustion takes place within the boiler while the fuel is in suspension
* Heat is transferred to the boiler walls and then to the heat exchange tube banks as the combustion gases pass through the boiler
* Steam is raised by passing water through tubes located in the boiler
Some ash falls to the bottom of the boiler (bottom ash), some is carried over with the flue gases (fly ash)
* The flue gas is later cleaned up (i.e., remove NOx, SOx, particulates)
* Around 15 % CO2 in the exhaust.
What energy resource reserves are available and recoverable, from high to low?
Renewable:
1. solar
2. wind
3. geothermal
4. biomass
5. OTEC (ocean thermal energy conversion)
6. hydro
Non renewable:
1. coal
2. petroleum
3. natural gas
4. nuclear
What is the most costly type of energy plant to construct?
Nuclear
(& Open cycle gas turbine plants (OCGT)?)
How do open and closed cycle gas turbines differ?
In the open cycle gas turbine, the air enters from the atmosphere and passes through the compressor, combustor and turbine, so all working flow releases into the atmosphere.
In the closed cycle gas turbine, the working flow is continuously recirculated through the gas turbine.