Facts Flashcards
feedback systems for Climate sensitivity:
• changes in water vapor
(positive feedback)
• clouds
(positive or negative feedback)
• ice and snow cover
(positive feedback)
• the ”lapse rate”
(vertical temperature profile)
(negative feedback)
Climate sensitivity values:
3 deg C
Range: 1.5-4.5 deg C
(CCS)3 main CO2 capture technologies:
• Post-combustion:
- Scrubbing fluegases with chemicals (amonia/ amine?)
- Stripping teh CO2 with high temp steam
- Very heat/energy demanding.
• Pre-combustion:
- Cleaning the fuel before use, to easier strip teh CO2 after combustion.
- Used with gasification)
- Can not be retrofited to old coal powder plants.
• Oxyfuel:
- Burning the fuel with pure oxygen creates almost pure CO2 after combustion (you can capture all flue gas)
(CCS) CO2 storage:
• (Atmosphere) • Fossil fuel reservoirs - 100s - 1000s m underground • Carbonate rocks • Deep saline aquifers • Intermediate and deep oceans - Liquid and high density for high pressure • Ocean floors / sediments (Utsira formation Norway)
Nuclear (pros, cons, prospects):
Pros: • Almost CO2-free - Clean, except for radiation and waste. • Needs little fuel (Lots of fuel availabel) • Low running costs - Good baseload plant • May produce a lot of energy.
Cons: • Nuclear is expensive today - High investment/capital cost - You want to run it all the time • Political issue - Weapons - Who may have it? • Security (political) - Not good for all locations - Accidents - Terrorists • Storage of waste • Mining of fuel • Large cycling costs (hard to ramp up and down a lot and fast)
Future prospects:
• More cost-competetive with higher carbon taxes.
• When the 4th generation reactors are mature they might become cheaper to build.
• Better ramping technologies (better together with renewables)
• Cheaper breader technology
- Less waste (higher efficiency and less wepons)
Assumption values of Solar PV:
- Perpendicular insolation (optimal) 1000W/m2
- Avarage insolation 250W/m2
- Efficiency 15-30%
Basic concept of fuel cell:
In:
• Air
• Hydrogen
Out:
• Electricity
• Heat
• Water
Fuel cells (pros, cons, prospects):
Pros: • Clean • Quiet • Efficient (small and large scale)
Cons:
• High cost
• Material problems
• Hydrogen production/storage/transport
Prospects: • Useful in speciel aplications (space) • Where you have cheap electricity, over production, plenty of storage etc. • Stil too expensive, not competative • Probably not for transport
The levelized cost of electricity (LCOE), also known as Levelized Energy Cost (LEC)
The net present value of the unit-cost of electricity over the lifetime of a generating asset. It is often taken as a proxy for the average price that the generating asset must receive in a market to break even over its lifetime.
(See formula book)
Scarcity rent:
Scarcity rents occur in a market when potential demand exceeds possible supply. (Lecture)
(House in the center of a city. Scarce resource, we pay more.)
The marginal opportunity cost imposed on future generations by extracting one more unit of a resource today.
“Scarcity Rent” is one of two costs the extraction of a finite resource imposes on society. The cost of using up a finite resource because benefits of the extracted resource are unavailable to future generations.
The other is “Marginal Extraction Cost” the opportunity cost of resources employed in the extraction activity.
Efficiency is achieved when the resource price (the benefit society is willing to pay for the resource today) is equal to the:
sum of marginal extraction cost and scarcity rent.
Opportunity cost:
The net benefit of the best alternative
foregone. (Lecture)
“The loss of potential gain from other alternatives when one alternative is chosen.” Opportunity cost is a key concept in economics, and has been described as expressing “the basic relationship between scarcity and choice.”
Discount rate:
The discount rate represents the (opportunity) cost of capital and reflects the (risk–free) market interest rate plus a risk premium.
Resources vs reserves:
Resources: All the (known) existing amounts of this substance. The amount of resources only change if we find more.
Reserves:
All the resources that are economically (politically etc) and technlically possible to extract/retrive. This may change due to new technology or change in economy. Scarcety may incease price and then we might extract more.
Carbon content fuel:
(gC/MJ) (approx)
Gas: 15
Oil: 20
Coal: 25
Capacity factors for energy production:
Due to weather:
Wind: 25% (25-40%)
Solar PV: 15% (10-30%)
Nuclear: 80% ( 70-90%)
Hydro (complicated)
U235 concentrations:
(the rest is U238) U-natural: 0.7% U235 U-fuel: 4% U235 U-waste: • 1% U235 • 1% Pu (nuclear wepons) • 4% fission prod
Assume 90% enrichment efficiency
Nuclear waste:
5 kg uranium ore
-> 3 g used fuel + 2 kg CO2
(used fuel = toxic waste)
Materials to slow down fission reaction:
reactor types
- Water – small reactors, but need enriched uranium (Sweden)
- Heavy water – excellent moderator but expensive
- Graphite – excellent moderator, but burnable and need large dimensions
Dangerous fission products:
“short” half life
Cobolt-60:
• 1920 halflife days
• 0,3 kg
Strontium-90:
• 11030 halflife days
• 28 kg
Iodine-131:
• 8 halflife days (immediate danger)
• 0,7 kg
Cesium-137:
• 11000 halflife days
• 54 kg
Approx efficiencies thermal power:
Coal: 33%
Nuclear: 33%
NG: 44%
Oil: 31%
Pu breading:
U238 -> Pu239
About 0.6 Pu atoms produced/fission of U235
Half of them are fissioned and half end up in waste.
-> 0.3 Pu fissioned / 1 U235 fissioned
During fission of U235 neutrons are released and some of the neutrons are captured by U238 so that it is breaded into the Plutonium isotop Pu239. About half of this Pu will undergo fission reactions of its own and from this 20 % of the energy will be produced.
Un conventional fossil fuels
Shale oil: (from oil shale, a rock)
• Unconventional oil produced from oil shale rock fragments. Dirtier, more GHG. Needs more refining, by-products, landuse etc. (Canadian oil-sand)
Shale gas: (fracking of shale rock)
• (Gas) Water, sand and chemicals are injected into the rock at high pressure which allows the gas to flow out to the head of the well.
• The term fracking refers to how the rock is fractured apart by the high-pressure mixture.
• Fracking nowdays refer to drilling horizontally to the rock layer, which can create new pathways to release gas or used to extend existing channels.
Fracking uses huge amounts of water, which must be transported to the site at significant environmental cost. As well as earth tremor concerns, environmentalists say potentially carcinogenic chemicals may escape during drilling and contaminate groundwater around the fracking site.
Price elasticity:
eb = inf (fixed price)
• Regulated by competition, government etc.
eb = 0 (fixed quatity)
• Things we need a certatin amount of that doesnt change, like drinking water or similar. (Life neccesities)
Variation management:
- Storage- longterm and short term (+) batteries, pumped hydro etc.
- DSM- adjust flexible demand acording to supply (-+)
- Complementary technologies that can easily fill out “gaps in the system. (-)
- Trade/transmission (-+) High transmission capacity and large area for good result.
- Curtailment (+) Get rid of over production/turn off the generation.
Hydrogen storage:
Gas form:
• High-pressure tanks (350–700 bar tank pressure)
• Still takes up quite some space
Liquid form:
• Cryogenic cooling 33K
• High pressure and temp isolated.
• Little space, but hard to do
Solid:
• Stored onto the surface of some solid materials (adsorption) or within solid materials (absorption).
Ratio C to CO2
12 to 44 (g/mol)
44/12 = 3.67
