Exam Q/A (old papers) Flashcards
(40 cards)
- When discussing the need for making a global energy transition to minimize damages from climate change, often a term called climate sensitivity is used.
a). Explain what is meant by climate sensitivity (exact physical definition not required), and what
unit is most commonly used to measure it. (3p)
a. According to the IPCC (Forth Asessment), “Climate sensitivity is a metric used to characterise the response of the global climate system to a given forcing. It is broadly defined as the equilibrium global mean surface temperature change (°C) following a doubling of atmospheric CO2 concentration.
Uncertainties in future emission scenarios and various feedback such as rates of oceanic heat uptake, clouds, changes in water vapor, ice and snow cover, and the “lapse rate” all
contribute to the uncertainty about the future rate of temperature change.
- When discussing the need for making a global energy transition to minimize damages from
climate change, often a term called climate sensitivity is used.
b). Approximately what is the best current estimate of this parameter, and roughly what is the
uncertainty range? (3p)
b. The “likely” (> 66% probability) range of climate sensitivity is between 1.5 –4.5 °C, according to IPCC AR5. Most mainstream scientists put their “best guess” for climate sensitivity somewhere in the middle of the range, between 2.5 and 3.5 C.
- When discussing the need for making a global energy transition to minimize damages from climate change, often a term called climate sensitivity is used.
c) . What are the implications of this uncertainty for the global energy system? (4p)
c. There are many implications for this uncertainty for the global energy system. For
example, stabilizing global temperature change to be below the 2 °C target will require very fast reductions of global emissions and the rate of reduction will depend on the climate sensitivity. If climate sensitivity is high (4.5 °C per doubling of CO2conc.), even reducing emissions to zero will not be enough. Global net emissions must be reduced below zero using negative emission technologies (e.g. BECCS). However, if climate
sensitivity is low (e.g. 1.5 °C per doubling of CO2), we have plenty of time to solve the problem (50-100 years).
What is emission factor?
Measure of the average amount of a specific pollutant or material discharged into the atmosphere by a specific process, fuel, equipment, or source. It is expressed as number of pounds (or kilograms) of particulate per ton (or metric ton) of the material or fuel.
What is Capacity Factor?
The net capacity factor is the unitless ratio of an actual electrical energy output over a given period of time to the maximum possible electrical energy output over the same amount of time.[1] The capacity factor is defined for any electricity producing installation, i.e. a fuel consuming power plant or one using renewable energy, such as wind or the sun. The average capacity factor can also be defined for any class of such installations, and can be used to compare different types of electricity production.
- a). Name the three general categories of CO2 capture processes from power production. (3p)
a. (1) flue gas separation, (2) oxyfuel combustion in power plants, and (3) precombustion separation.
3b). Once CO2 are captured, what are the options to store CO2? Name at least three options. (3p)
b. Captured carbon can be stored in geologic sinks and the deep ocean. Geologic storage options include deep saline formations (subterranean and sub-seabed), depleted oil and
2 gas reservoirs, formations for enhanced oil recovery operations, and unminable coal seams. Deep ocean storage approaches include direct injection of liquid carbon dioxide into the water column at intermediate depths (1000–3000 m), or at depths greater than 3000 m, where liquid CO2 becomes heavier than seawater, so CO2 would drop to the ocean bottom and form a ‘‘CO2 lake.’’ Other storage approaches are proposed, such as enhanced uptake of CO2 by terrestrial and oceanic biota (mineral carbonation). Finally, captured CO2 can be used as a raw material by the chemical industry.
what is load factor?
In electrical engineering the load factor is defined as the average load divided by the peak load in a specified time period.[1] It is a measure of variability of consumption or generation; a low load factor indicates that load is highly variable, whereas consumers or generators with steady consumption or supply will have a high load factor.
F load=Average load/Mx. load in given time period
An example, using a large commercial electrical bill:
peak demand = 436 kW
use = 57200 kWh
number of days in billing cycle = 30 d
Hence:
load factor = { 57200 kWh / (30 d × 24 hours per day × 436 kW) } × 100% = 18.22%
…4d). Briefly discuss (qualitatively) the effect of price elasticity of demand on CO2 avoidance cost.
What happens to the mitigation cost when the demand is more vs. less elastic? (3p)
d. When demand is responsive to prices, less emissions will occur as a result. The more
elastic the demand is, the lower the mitigation cost.
…4d) Mention three possible factors that could prolong the era of fission energy. (3p)
d) Discovery of new resources and reserves becoming economical due to increased
price of Uranium, better technology etc.
Reprocessing the spent fuel and using the fissionable materials in it.
Breeder reactors that can convers U238 and other fertile isotopes into fuel.
- Explain how a fuel cell functions and name a relevant application for such a technology. (3p)
- A fuel cell uses the chemical energy of hydrogen or another fuel to produce electricity. If
hydrogen is the fuel, electricity, water, and heat are the only products. The basic chemical
reaction is H2 + ½ O2 -> H2O. Fuel cell applications include:
• small scale: chargers, laptop
• medium scale: cars and heavy trucks, solar energy systems
• large scale: back-up power, stationary power.
Alternative answer:
A fuel cell is an electrochemical cell that converts the chemical energy from a fuel into electricity through an electrochemical reaction of hydrogen-containing fuel with oxygen or another oxidizing agent.[1] Fuel cells are different from batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy comes from chemicals already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.
- Give brief answers to the following questions on basic concepts.
• What is the energy efficiency gap?
Point out 4 factors that contribute to, or can explain why the energy efficiency gap exist? (4 pt)
Energy efficiency gap refers to the improvement potential of energy efficiency or the difference between the cost-minimizing level of energy efficiency and the level of energy efficiency actually realized. It has attracted considerable attention among energy policy analysts, because its existence suggests that society has forgone cost-effective investments in energy efficiency, even though they could significantly reduce energy consumption at low cost.
• “Transaction costs”: costs of searching and processing information
o Transaction costs are not absolute, they differ between actors
o Imperfect information. Households and small companies often lack energy
knowledge causing high transaction costs
o High in relation to energy which is often a small part of expenditures
o Bounded rationality: cognitive limitations to rational choices
• ”Split incentives”:
o E.g. Tenant- landlord problems:
§ The landlord chooses major appliances, the tenant pays the electricity
• Consumers have high discount rates
• Consumers maybe risk adverse.
• Consumers have
- Give brief answers to the following questions on basic concepts.
- Define price elasticity and write down the formulae for ε. (4 pt)
Price elasticity:
• Price elasticity of demand (ε) is the change in demand for a good due to a change in price. The formula is:
• ε = (dQ/Q) / (dP/P)
• i.e., the percent change in quantity (Q) divided by the percent change in price (P)
Name and describe four variation management (sometimes also called load management, load shifting or load smoothing) techniques for the electricity system. (4 pt)
Variation management:
• Active – thermal plants, wind curtailment, demand side management, storage, cogeneration and fuel production (hydrogen), Transmission and trade – both passive and
active.
• Thermal generation: Start-up /shut down, Part load
• Wind power curtailment
• Transmission and trade (Wind variations are reduced as geographical scope increases;
Trade with hydropower rich regions can reduce impact of variations
• Storage
• Demand side management
• Co-generation and fuel production (such as hydrogen production)
- A. Explain why is it that it is NOT necessarily the technology with the lowest levelised cost of electricity that is the most profitable to invest and that private actors on a market will invest in.
(4 pt)
A. If you have a technology A and a technology B to produce identical cars, and the cost of
producing a car using technology A is lower than when using technology B, then it is most
profitable to use technology A. This is not necessarily true for electricity because the price of
electricity varies over time1! Take two different technologies, for instance solar PV and coal.
They produce electricity at different points in time. This means that they will also generate
different revenues of income per kWh. For instance, if the price of electricity is higher during
the middle of the day when the sun shines, solar PV would get higher average revenues per kWh of electricity produced than coal, because coal also generates a lot of electricity night time when electricity prices are lower. This, in turn, means that the profitability of solar PV can be higher than that of coal even if the levelised cost of electricity from solar PV is higher than that of coal based electricity. Thus, the key here is to make a distinction between the profitability and the levelised cost of a given technology. Profitability is basically revenues minus costs. The problem with the levelised cost concept is that it does not consider variations in revenues (the price of the product sold).
what is levelized cost of electricity?
In electrical power generation, the distinct ways of generating electricity incur significantly different costs. Calculations of these costs at the point of connection to a load or to the electricity grid can be made. The cost is typically given per kilowatt-hour or megawatt-hour. It includes the initial capital, discount rate, as well as the costs of continuous operation, fuel, and maintenance. This type of calculation assists policy makers, researchers and others to guide discussions and decision making.
The levelized cost of electricity (LCOE) is a measure of a power source which attempts to compare different methods of electricity generation on a consistent basis. It is an economic assessment of the average total cost to build and operate a power-generating asset over its lifetime divided by the total energy output of the asset over that lifetime. The LCOE can also be regarded as the average minimum cost at which electricity must be sold in order to break-even over the lifetime of the project.
Previous:2. A. Explain why is it that it is NOT necessarily the technology with the lowest levelised cost of
electricity that is the most profitable to invest and that private actors on a market will invest in.
Actual question: If there are certain problems associated with this method and how it is being interpreted,
why do you have to learn about a concept such as the levelised cost of electricity? (4 pt)
B. The concept of levelized cost was primarily developed to compare the cost of technologies that generate baseload electricity and operate most of the time. Then the variation in the price of electricity over the day or the year does not really matter since all power plants meet the same price variation. In such circumstances, the technology with the lowest levelised cost of electricity will also be the most profitable to invest in. It is still useful to understand this concept since in public debates and in media, when people compare the cost of different technologies they (most often, if not almost always) use the levelised cost of technology as their method, and then it is good to know how it works and which conclusions you may draw and also, as pointed out here, the problems that exist with it.
What is baseload electricity?
Base load is the minimum level of electricity demand required over a period of 24 hours. It is needed to provide power to components that keep running at all times (also referred as continuous loa
What is Baseload Power?
The argument basically goes like this. When the wind isn’t blowing and the sun isn’t shining, renewables like solar and wind aren’t producing electricity. What happens during that time when we need energy? We need something more reliable — something that produces electricity all the time and that we can rely on. That’s baseload power, provided by reliable sources such as nuclear and coal fire power plants.
What is peak load?
Peak load is the time of high demand. These peaking demands are often for only shorter durations. In mathematical terms, peak demand could be understood as the difference between the base demand and the highest demand.
What is load (e.g. base load and peak load)?
Load, in electrical engineering, is the amount of current being drawn by all the components (appliances, motors, machines, etc.).
Load is further categorised as base load and peak load depending upon the nature of the electrical components connected. As you may be familiar, all electrical appliances at your home do not run at all times.
A toaster or microwave oven may be used for a few minutes,
A television or computer may be used for a few hours
Lighting in the house is only required during the evening and so on.
There are several appliances which keep running at all the times, no matter what. The refrigerator, for example, has to be plugged in at all the times. Another such example are the heating, ventilation and cooling systems in the house (HVAC system).
What is GWe?
Gigawatt electrical, abbreviated GWe
- a. Define Kaya identity (equation).
3 pt
The Kaya equation is an equation relating factors that determine the level of human
impact on the environment or climate, in the form of emissions such as the greenhouse gas carbon dioxide. In the case of climate impact, it decomposes GHG emissions into the
product of four drivers: population, GDP per capita, activity level per capita, and
emission factors (gCO2 per unit activity).
GHG = ( GHG/E) x (E/GDP) x (GDP/POP) x POP = POP x GDP x El x Cl
Alternative answer from lecture notes:
• Kaya identity is a form of decomposition
• Breaks GHG emissions into the product of several important (nonindependent)
drivers
• Simple yet important and useful framework for understanding the drivers of
changes in emissions
Equation: GHG= (Polulation) (GDP/Capita)(Energy/GDP)(GHG/Energy)
- Acvity is represented by economic ac@vity per capita
- Energy Intensity is represented by energy per unit of economic acvity
- Carbon Intensity is represented as the CO2/GHG emissions per unit of energy
Kaya identity.
c. What are the pros and cons of using historical trends to make this type of projections? (3 pt)
• Strengths
- Uses empirical / historical trends
- Good for business-as-usual forecasts and short-term forecasting
- Econometric approach is a more detailed form
• Weaknesses
o Cannot predict discontinuous events
o May miss structural changes
o May discourage determining underlying drivers
o Trends can be misleading (e.g. between 2005-2010 the global economy was
significantly affected by the economic crisis. It may not happen again between
2010 and 2020).
o Overlooks physical limits that prevent trends from continuing
what is the meaning of the saying “you cannot derive an ought from an is”
The role of science
• Science can make descriptive statements …
̶ ”If we burn all coal resources, global warming will exceed x°C.”
• …but not norma@ve, prescrip@ve, value-based statements.
̶ “Therefore, we should leave most of the coal in the ground.”
̶ This is the realm of politics, not science!
• David Hume (Scosh philosopher, 1711-1766):
“you cannot derive an ought from an is”.
