First 2 guest lectures - introduction Flashcards
What is an electricity grid?
- Electricity grid that converts energy from one form to another
- matches the amount of consumption to the amount produced
What are the main goals for an energy system?
- convert energy
- regular and continuous supply
- efficiency
- store excess eenergy
- supply == demand
What is energy used for?
electricity - 10kwh/day
heating
transport
What are the challenges of building an energy system?
- finite energy resources
- sustainability
- robustness/ reliability
- cost
- maintenance
- land / resources available
- accessibility/ equality
- large scale of transformation
- integration of renewables
- economic cost
How much more energy are humans likely to need in the future?
50%
What is leading the increase for the demand of energy?
increasing industrialization - GDP growth
How much energy i used in the UK a day?
190 kWh/p/day
How much energy in the UK could theoretically be gotten from reneewables?
180 kWh/p/day
What is peak oil?
The point at which oil production reaches its peak value and after which enters a terminal decline
Why is predicting peak oil so important?
- too late and we risk fuel shortages
- too soon, economic damage
What is Ohms law?
V = IR W = VI W = I^2 R
What kind of energy do fossil fuels provide?
1 barrel of oil - 6GJ 1 tonne of oil - 42 GJ 1 m^3 of gas - 40 MJ 1 tonne of coal - 29 MJ 1 kcal - 4.22 kJ
What is the first law of thermodynamics?
Energy is neither created nor destroyed, but converted from one form to another
Q = q + work
What is the second law of thermodynamics?
A device operating continuusly cannot export only work from an isolated source of heat
1 =/ 0
What is the theoretical maximum extractable work called?
exergy
What types of work are usually treated as 100% exergy?
Mechanical, electrical, chemical
What does the maxiumum amount of exergy depend on?
the hot source temperature
the coolest heat sink temperature
As temp –> inf. the source tends to pure E, when the heat source temperature is close to that of the ambient, the energy is of low grade
What is primary energy?
the raw fuel enetering the economy
What is secondary energy?
The energy reaching consumers
What are some examples of secondary energy?
- refined oil
- town gas
- electrical power
What is the equation for the work dependent on temperature?
W = (1 - Tc/ Th) Q - carnot efficiency
What kinds of impacts do fuels have on the environents?
Upstream: spoil at mines, oil extraction and transportation, gas extraction using fracking
E.g. Aberfan disaster, piper alpha, deepwater horizon
Getting energy from fuels: Wood or coal creates smoke
What is temperature inversion?
When the raidative cooling of the ground or warmer layer is created by a warm fron 1-2 km above the surface
What does temperature inversion lead to?
COnvection cannot disperse the emissions, become trapped in the cool air
1952 london smog - 8000 deaths
What is the strategic solution to air pollution?
- dispersing from urban centre
- generating power at remote large power stations
- omporving domestic fireplaces and fuel
- distribution of heat via district heating
What is district heating?
When heating is shared amongst buildings by a system of pipelines
What is the ideal use case for district heating?
in residential or commercial propertires where they cna provide higher effciencies and better pollution control
What are some of the environmental consequences of renewable technologies?
- wind turbines effect bird migration
- wildlife disruption
- large amounts of resources needed
- environmental considerations of geothermal energy (aquatic)
- carbon footprint
- noise pollition
- land use (wind/ solar)
- dams have consequences on river ecosystems
What is the definition of weather in climatology?
the state of the atmosphere at any give pooint at a given time
What is the definition of climate in climatology?
the set of weather statistics at a location averaged over a long period
What is the definition of a greenhouse gas?
Tranpsarent to sunlight, absorb cooler, reflected radiation
What is climate forcing?
The extra solar radiation that would be needed to obtain the same temperature elevation the absence of the effect
What is the equation for climate forcing?
deltaF = 5.35(ln(C/Co))
Logarithmic variation comes from the fact that the adsorption of CO2 in the new atmosphere is already nearly saturated. Tis means te increase of forcing with concentration for other greenhouse gases is much sharper
What is climate sensitivity?
the global average temperature rise resulting from the forcing equivalent to doublng the CO2 concentration over pre-industrial levels:
delta T = lamda*deltaF
lambda is the climate sensitivity
What is albedo?
a measure of the reflection of sola radiation out of the toal rediation recieved by an astronommical body such as the earth
What does an albedo = 0 mean?
the object is a blackbody (absorbs all light)
What does an albedo = 1 mean?
The object is a pure reflector
What is the average albedo of the earth from the upper atmosphere>
30-35%
If the earth is treated as a heate engine what energy is it creating?
wind and ocean circulation between the equator and the poles
What is the snowball earth?
the earth has been entirely frozen at least once
This state is associated with low GHG concentration
The hypothisis is that an ice-albedo feedbac would result in global ice
What is the grounded/ floating ice and sea level model?
Floating ice displaces the same volume of sea water as when it melts, so makes no contribution to sea level
The ssea level depends on the amount of fresh water locked up in grounded ice, like glaciers - and the antarctic
How much would the complete melting of the antarctic raise the sea level by?
60-70 metres
What is the runaway greenhouse effect?
When the net positive feedback between surface temperature and atmospheric opacity increases the strength of the greenhouse effect on a planet until its ocean boils away
This is thought to have happened in Venus, where the increase in evaporation from the ocean produced large amounts of water vapour
