Final Review Flashcards
Units of energy
kW, mW
Nameplate capacity (kW)
The maximum rated output of a generator, prime mover, or other electric power production equipment under specific conditions designated by the manufacturer.
(Percent of Building Load * Annual Building Load (kWh)) / (8760 * Capacity Factor )
kWh (per day/month/year)
kW x #h
Sectors impacting climate change
Energy and agriculture
Sectors under energy
- transport
- heating and cooling
- electricity
Sectors under agriculture
- food production
- land use change
- deforestation
Parts of a solar panel
cell
forms module
forms array
Energy efficiency of solar PV (2020)
15%-24% of solar energy is converted to electricity
Transforming solar radiation energy into electrical energy
Solar array -> inverter DC -> AC, grid
Transforming solar radiation energy into electrical energy
Solar economies of scale
Bigger is better
Prefer commercial rather than residential buildings
Prefer old derelict sites to green fields
The sky is the limit
Solar collector loop
Hot water, underfloor heating and central heating → boiler → mains for cold water feed → solar thermal twin coil cylinder → pump → flat panel or evacuated tube collector → pump → boiler → hot water
Poly-crystalline vs mono-crystalline solar cell
Mono-crystalline is more efficient and more expensive
Solar district heating (SDH)
Consist of large fields of solar thermal collectors feeding their produced solar heat into block or DH networks in urban quarters, smaller communities, or large cities
Solar collector
Pipes with water heated by the sun, no electricity/moving parts
Should work even on a cloudy day (contrary to photovoltaics)
Low-tech, cheap, materials are widely available
Closed loop water
Closed loop, no waste of water
Very little electricity needed
Very cheap to install and run
Need hot water but no sun?
Insulated storage tank
Insulated pipes (hot and cold)
Large holes in the ground that is insulated and sometimes has black balls for covers
Hot water infrastructure costs
Hot water network is expensive to install but very cheap to run (low maintenance costs)
Summary of solar thermal
Bigger is better: economies of scale
Significant surface needed (competes with farm land)
Meets only a portion of the demand
Cheap technology
A number of barriers to overcome
Main components of a wind turbine
- blade
- rotor
- brake
- gearbox
- nacelle
- anemometer
- controller
- generator
- yaw drive
- yaw motor
- power cable
- computer system
Price of solar
Biggest drop in electricity production cost between 2009 and 2019 – 89% in these 10 years
What is the capacity factor?
The ratio of the actual energy produced in a given period, to the hypothetical maximum possible, i.e. running full-time at rated power.
It is geographically relevant
Capacity factor formula
Energy output (kWh/year) = nameplate capacity x capacity factor x hours of use per year
Average power generated by wind/peak capacity
ex. 5MW wind turbine, if it produces an average of 2 MW, then its capacity factor is 2/5=40%
Trias Energetica
- Limiting the demand for energy
- Use as much sustainable energy as possible
- (When necessary) deploying fossil fuels as efficiently and cleanly as possible, reducing the use of fossil fuels
Difference between energy and electricity
Electricity is a specific form of energy that you use to power your home/vehicle.
Basic principle of wind turbine
Transforming kinetic energy into mechanical into electrical energy
Betz Law
Maximum theoretical energy efficiency of a wind turbine
MAX of 59.3% efficiency
Pros and cons of bioenergy
Pros
-renewable
-waste reduction
-reliability
Cons
-expensive
-space requirements
-some adverse environmental impact
Limitations of bioenergy
Storing and processing of biomass requires large amounts of space (which limits the location options). Some fuel sources are seasonal, may compete with food production in specific cases, large footprint
Constraints of biomass
-lack of sustainable supply of biomass
-biomass production competes with food production
-bio-energy may not always be low carbon on a life-cycle basis
District heating in Copenhagen
The district heating system is supplied by heat from combined heat and power (CHP) plants and from waste incineration plants in the region.
A system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating.
Hydrogen formula
2H2 + O2 = Energy +2H20
Hydrogen + oxygen = energy + water
Basics of H2
Most common element in the universe
Can be produced anywhere you have electricity and water
Generates heat OR electricity
Produced, stored, transported, used without pollution/CO2
3x energy density of oil
Fuel cell can reach 60% efficiency
Challenges of H2
Does not exist in nature
Requires a lot of energy to separate
Needs to be stored at high pressure (700 atm)
Needs to be refrigerated (-253ºC)
25% of energy for the same volume of gas, big tanks needed
Fuel cells need maintenance (moving parts)
Subject to leaks (very small gas)
Exposive
Green H2
Only sustainable way, produces zero carbon emissions
Electrolyzers split water into hydrogen and oxygen (electrolysis)
May compete on cost vs blue/brown H2 in 2030
Demand side of H2
Industry: 50% efficient, worse than batteries, potential use in industries such as chemical production
Heating: space heating out-competed by heat pumps (efficiency and cost)
Transport: 20% more expensive than EV, hopefully for planes and ships
Potential for large power plant
Fertilizer, hydrogenation, methanol, hydrocracking, desulphurization, shipping, off-road vehicles, steel, chemical feedstock, long-term storage, etc.
Summary of H2
Large public funding
Big expectations: small achievements
Can help resilience in a fluctuating wind/solar economy
Good when large excess wind power available (unconnected island)
