Lecture 8 - Decarbonisation pathways

Question 1

What is the basic challenge for designing decarbonisation pathways?

Answer 1

How do we get from where we are now to a low carbon future?

Question 2

What key things do we need to know when designing decarbonisation pathways?

Answer 2

1. How much energy does the work need each year until 2100? -> population, wealth, behaviour
2. What technologies and fuels can provide that energy? -> fossil fuels, renewables, nuclear, what technologies are available?
3. How much do these fuels and technologies cost now and in the future? -> innovation, scale
4. How much CO2 can we emissions along our pathway? -> climate sensitivity

Question 3

What are the SSPs (Shared Socio-econimic Pathways)?

Answer 3

• Provide information on energy, land use, emission projections, demographics and economic projections.
• SSP1 = very technologically advances and energy efficient
• SSP5 = continuing to burn fossil fuels
• Each SSP scenario has different GDP, population, energy demand etc -> which is correct??

Question 4

How do we know which technologies to include in our pathways?

Answer 4

Tend to include those that have been proven and the costs are known:

• Biomass with CCS - we know that it works
• Air carbon capture - at demonstration stage

We don’t include those that we are less certain about:

• Hyperloop - beyond concept stage but not sure that it will work yet
• IETR fusion reactor - huge uncertainty around costs

Question 5

Why is it tricky to estimate future costs?

Answer 5

• Solar has continually exceeded expectations, but will the same be true of other technologies?
• Different models make very different projection about future costs

Question 6

What are the challenges around estimating our carbon budget?

Answer 6

• Huge range in models - hope that this will narrow as our understanding of the climate system improves.
  e. g. for a 50% chance of keeping temps below 2C, CMIP5 has cumulative CO2 emissions of 2,000 GtCO2 (2000-2100) but the range is 1000 to 4000 GtCO2.

Question 7

What is an energy system model (ESM)?

Answer 7

• A model that studies the interactions between the energy system, the economy, the environment and technology and can be used to analyse decarbonisation pathways.
• Key objectives of an ESM are to meet energy needs whilst staying within the budget (economic and CO2)

Question 8

What are the key inputs into an ESM?

Answer 8

Energy demand
Technology availability
Fuel costs
Technology costs
CO2 budget

Question 9

What are the key outputs of ESM?

Answer 9

• Least expensive mix of technologies and fuels that achieve achieves the pathway objective of: meeting energy needs and keeping within a budget.

Question 10

What does TIAM-Grantham specifically look at?

Answer 10

• TIAM - Times Integrated Assessment Model
• Part of AVOID-2: UK government funded climate change research programme. The research being undertaken will provide scientifically-robust, policy-relevant answers to questions directly related to the Ultimate Objective of the UN Framework Convention on Climate Change (UNFCCC), which is to ‘prevent dangerous anthropogenic interference with the climate system’.
• Simulates the evolution of the global energy system over the 21st century, under a variety of scenarios, imposing limits on global CO2 emissions in order to achieve specified long-term global temperature goals.

Key inputs:

• Fossil fuel supply - extraction, transformation
• CCS
• Bioenergy/renewable/nuclear supply - generation, cogeneration, heat
• Hydrogen production
• End use fuels
• Industrial technologies - industrial electricity
• Agricultural/commercial/residential/transport technologies

Question 11

What are the different types of EMSs?

Answer 11

• Sectoral coverage: single sector (WeSIM for electricity) or whole system (TIMES.
• Temporal/spatial granularity: fine (WeSIM), coarse (TIMES)
• Geographic: national (UK TIMES) or global (TIAM)
• Level of technological detail: rich (UK TIMES) or sparse (AIM)
• Feedback to macroeconomy: absent/basic (TIAM) or detailed/integrated (AIM)
• Solution objective: least cost (TIAM) or scenario (MUSE)

Question 12

What are the alternatives to EMSs?

Answer 12

• Scenario tools such as the Global Calculator

- Expert workshops to identify scenarios

Question 13

What are the typical features of a low carbon pathways (2DS)?

Answer 13

• Transformation of primary energy sources - more biomass, wind, solar, nuclear, and less coal, oil and gas. -> increasingly so towards 2100
• Electricity becomes zero or negative carbon
• End-use sector shifts to a mix of fuels: transport sees oil replaces with biofuels, electricity and hydrogen, industry sees increasing electrification and gas replacing coal as well as CCS, buildings see increase electrification (heat pumps) as well as less coal and oil for heating.
• Whilst the range of scenarios is huge, they generally agree that the later we reduce emissions, the quicker the rate they will need to be reduced by and the more negative emission years needed.
• Although in recent years we have seen a levelling off of emissions, we now need to see emission reductions along with healthy economic growth (saw a reduction during the credit crisis but this was a no growth period)
• Results highly dependent on key assumptions around technologies, e.g. no CCS, limited biomass, no new nuclear etc

Question 14

How fast do we need to deploy new technologies?

Answer 14

• Depends on when we start - later action means a higher deployment rate is needed once we start.
• Exception is nuclear - expect the costs of nuclear to remain the same, vs the other technologies where we expect the costs to reduce, therefore later action probably means less nuclear.
• Technology commercialisation takes time
• We can’t ignore history - individual technologies rarely grow >20% pa, growth does not continue exponentially, established primary energy sources decline gradually.
• > what if we can’t break with history? If there are no tech growth constraints then likely that the 2DS will be met, if growth is constrained to the historical maximum then 2.1C met.
• BUT policy can lead to very rapid technology growth (e.g. solar PV)

Question 15

How reliant are we on negative emissions?

Answer 15

• Delaying action by 10 years (i.e. to 2030) means we’ll need three times as much negative emissions before 2100 and we will need negative emissions earlier than if we act in 2020.
• Is this possible? If bio-energy uses existing forests then we could have net negative emissions.

Question 16

What are the limitations of EMSs?

Answer 16

• Energy system models (as part of IAMS) - set mitigation costs against BAU baseline, fail to account for dynamic innovation and fail to account for human behaviour and dynamics
• Energy system model exercises - lack transparency, do no systematically show why model results differ and seek to project costs beyond a reasonable time horizon.

However, ESMs still dominate policy making, e.g.ICPCC, estimating costs of EU mitigation targets, setting UK carbon budgets