Fundamentals Flashcards
Which types of energies exist in energy conversion?
Primary, Secondary, Final, and Useful
What do the laws of thermodynamics state (0st, 1st, 2nd)?
0th: if two thermodynamic systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
1st: Every closed system can be described by an extensive state function: Energy
A closed system can change its energy content only by transferring over the system boundary
2nd: -The disorder within a closed system increases or doesn’t change due to an energy conversion.
-The conversion of energy in a orderly form to an energy in a disordered form is completely possible but not backwards.
-Every natural process is irreversible.
-The part of energy, which is convertible into work, decreases during every natural process.
What is exergy, anergy?
Exergy is the maximum useful work dischargeable if you bring a system into equilibrium with its ambience
Anergy is the part of energy that cannot be converted into exergy.
The total of exergy and anergy is constant
Most types of energy conversion are based on which
thermodynamic processes? Which process does theoretically achieve
the maximal efficiency possible?
The process that achieves the maximal efficiency possible is Carnot. -Combustion, Nuclear Conversion -Piston and flow machines -Generator Electrical motor -Renewable energies
Name the four steps of this process and sketch a Ts/pV diagram
therefore
Isentropic compression supllying work w1-2.
Isothermal expansion supplying heat qin.
Isentropic expansion discharging work w3-4.
Isothermal compression dischargin heat qout.
On which parameter(s) depends the efficiency of such a process
Tout and Tin
What is the difference between Lower Heating Value and Higher
Heating Value? Which of them is used to calculate efficiency values
and what is therefore possible?
LHV is the energy released during the combustion of a specified quantity of fuel, with the reactants and products having a temperature of 25ºC and the product water vapor being gaseous.
HHV is the amount of heat released during the combustion plus the latent heat of the produced water vapor.
LHV are used to calculate efficiency values and therefor is possible to have more than 100% of efficiency.
Which energy conversion concepts for fossil fuels do you know?
Approximate the exergy efficiency of each concept!
Heating plant: 12%
Power plant: 40%
Combined heat and power plant: 40%
Combustion engine: 40%
Which energy conversion concepts for renewable energies do you
know? Approximate the exergy efficiency of each concept!
Water power: 95%
Wind power: 45%
Solar cell: 15%
Solar collector: 60%
Name four of the main greenhouse gases and sort them after their impact on the (total) greenhouse effect (in%) /anthropogenic greenhouse effect?
H2O: 36-70%
CO2: 9-26%
CH4: 4-9%
Ozone 3-7%
Why is even a small change of global temperatures problematic?
Relocation of climate zones.
Higher probability of natural disasters.
Higher wind speed.
Sea level rise.
In which countries will the energy consumption grow the most in the future (until 2035)?
China, India and non OECD countries
How much of the primary energy is actually converted into
electricity by power plants (which efficiency η)
~46%
Which will be the most used source for electricity generation by
2040?
Renewable energies
How will the global CO2 emissions develop in the future?
Distinguish between OECD and non OECD countries!
non OCED countries will increase, and OCED countries will decrease
What are possible scenarios of the CO2 emissions outlook?
In a evolving transition it will increase only.
In a faster transition it will start to decrease in 5 years time.
In an even faster transition it will decrease right now.
What are the goals for the share of renewables in gross electricity
consumption by 2030/2050 in Germany? Which is the most dominant
energy source?
50% and 80%.
Windpower
Energy economics: which cost categories with example?
Fixed costs: capital charges, salaries, insurances, taxes, storage costs.
Variable costs: fuel, ammonia, lime, water treatment.
The more operating hours per year of a powerplant the smaller the
…, the higher the…, no impact on…?
The more operating hours per year of a power plant the smaller the electricity production costs, the higher the variable costs, no impact on fixed costs
Compare a gas turbine power plant to a geothermal powerplant in
terms of cost categories in dependency of hours of operation.
Compare both the costs in Euros and the cost per kWh.
The absolute cost in Euros: The gas turbine power plant has low fixed costs, but it uses expensive fuels, which makes a large ratio of variable costs. The geothermal power plant has high fixed costs, but low operation costs, which makes a small ratio of variable costs. This means that the gas turbine plant in long hours of operation has higher costs than the geothermal power plant, but in small hours of operation has less costs than the geothermal power plant.
The cost per kWh: Electricity generation can be deduced from the cost structure. In case of low hours of operation gas turbine power plants are more cost effective compared to geothermal power plants. Geothermal power plants are only cost effective at baseload.
Which of the gas turbine power plant or geothermal powerplant is more cost effective in case of low hours operation?
In low hours of operation the most cost effective is the gas turbine power plant.
