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The Path to 100% identifies the fastest, most cost-effective and reliable ways to decarbonize the electricity grid — not just city by city, but across entire states and nations. Here, we take a dive into the trends of decarbonization, the transition away from fossil fuels, and what it means for one leading entity: the state of California.
The Differing Paths to Decarbonization
Overcoming the Variability Challenge with Renewable Fuels
Stages Along the Journey to 100%
A California Case Study
Charting an Optimal Path
What's Next?
The Differing Paths to Decarbonization
Dispatchable Power Generation Technologies
Variable Power Generation Technologies
Energy Storage Technologies
Fuel Types
Dispatchable Power Generation Technologies
Boiler/Steam Turbine
Gas Turbine
Combined Cycle Gas Turbine
Reciprocating Engine
Nuclear
Variable Power Generation Technologies
Wind
Solar
Click on each category for more information
Energy Storage Technologies
Pumped Hydro
Batteries
Fuel Types
Natural Gas
Coal
Synthetic Renewable Fuels
Off-Gas
Biofuels
Renewable:
Charting an Optimal Path
Annual CO2 emissions outlook
The Optimal Path provides lower carbon emissions through the transition period, and achieves net-zero carbon emissions in 2045 by replacing inefficient, inflexible thermal capacity with a wider array of clean energy sources, storage and flexible thermal generation.
2020
2025
2030
2035
2040
2045
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Mt CO2
Cumulative Mt CO2
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100
Cumulative Diff
Optimal Path
Current Plan
The cumulative carbon reduction with the Optimal Path is approximately 125 million tons of CO2 compared to the Current Plan.
The Optimal Plan maximizes the use of renewables by leveraging Power-to-X technology to produce carbon-neutral synthetic fuels using excess solar and wind that would otherwise be curtailed.
Annual curtailment
2020
2025
2030
2035
2040
2045
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TWh
Cumulative TWh
Optimal Path
Current Plan
Throughout the middle phases of the transition, the additional flexible thermal capacity that is available in the Optimal Path allows California to make use of over-generated wind and solar, something that is wasted in the Current Plan.
Cumulative Diff
Introducing Power-to-X technology helps to lower the levelized cost of electricity (LCOE), minimizing the cost to decarbonize California’s electricity sector, and improving competitiveness of local energy intensive industries. The power system based on only solar and storage can provide reliable power, but at a very high cost.
Annual total cost
2020
2025
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2035
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2045
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8
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BUSD
Cumulative BUSD
Optimal Path
Current Plan
Compared with the Current Plan, the Optimal Plan yields a net saving of $8 billion USD between 2020 and 2045.
Cumulative Diff
6
7
9
8
Charting an Optimal Path
The Differing Paths to Decarbonization
Overcoming the Variability Challenge with Renewable Fuels
Boiler/Steam Turbine
Coal
Combined Cycle Gas Turbine
What many global decarbonization plans lack is low-cost, low-carbon flexibility. As power systems achieve higher penetrations of renewable energy sources, managing variability across days, weeks and months becomes crucial.
Because solar and wind supply does not match demand, grid operators rely on dispatchable resources – including battery storage and fossil fuel plants – to fill in the gaps.
Power-to-X fuels can overcome the long-term variability challenge. Excess electricity from periods of oversupply of solar and wind energy is used to produce renewable synthetic fuels, such as methane or hydrogen, which can be used in some existing power plants that undergo conversion. Those power plants can then provide power and balancing services to the grid.
Overcoming the Variability Challenge with Renewable Fuels
Power systems won’t decarbonize overnight. The pathway toward a 100% renewable power system will be a phased transformation, leveraging different mixes of technologies and fuels at different steps along this path. At the end of this journey, renewables will serve as the baseload source of energy, storage will be the main daily grid balancer, and flexible thermal capacity will provide carbon-neutral power to maintain grid balance during even extreme heat waves and dark and cold periods.
Stages Along the Journey to 100%
A California Case Study
California’s Renewable Portfolio Standard (RPS) mandates that 60% of retail electricity must come from carbon-free sources by 2030 and 100% by 2045. Yet, the Current Plan allows for some fossil fuel generation in 2045 and beyond to cover grid losses. This study explores the optimal path to transition to a 100% carbon-neutral power system.
Stages Along the Journey to 100%
A California Case Study
What's Next?
A variety of technologies and fuels will have a role to play along the Path to 100%. Some technologies commonly used today will see a decreased role as decarbonization becomes a priority. A decarbonized grid will require an electricity mix powered by carbon-free or carbon neutral sources, as well as technologies that can balance the seasonal and daily changes in consumption, and weather variability, of key renewable energy sources like wind and solar.
Water Electrolysis
Excess Renewable Energy
Captured CO2 From Air
Synthesis
Stored Gas
Power-to-
Process
CO2 is directly captured from the air as a source of carbon for synthetic hydrocarbon fuel production, ensuring that the process does not increase atmospheric CO2.
Over-generated solar and wind electricity - that would otherwise be curtailed - powers the production of new fuel.
Electrolysis of water generates hydrogen fuel.
Renewable electricity synthesizes carbon and hydrogen into a new hydrocarbon fuel.
The carbon-neutral, synthetic fuel can be stored in existing natural gas storage infrastructure. It can be used by flexible power plants to produce power and provide balancing services for the grid when needed.
Current Plan
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GW
California Case Study
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Optimal Path
Current Plan without Fossil Thermal
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26.3
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151.6
15.0
3.7
40.2
9.1
CC_Gas
Peaker
Flexible
Hydro
Solar
Wind
Hydro_PS
Battery
Other
Hover on each step for more information
Hover on each plan for more information
0%
18% Global Average Today
20%
80%
100%
Renewable energy sources, such as wind and solar, were more expensive compared to fossil fuels when they first emerged.
0%
Storage was used in a limited capacity to provide ancillary services such as frequency regulation and short-term reserves, and the largest share of energy storage was pumped hydro.
The majority of electricity was produced by inflexible steam power plants using coal and natural gas plants. It takes hours — or even days — to switch them on and off.
Flexible power plants were used primarily to provide power capacity during times of peak demand, such as very hot summer days.
0%
0%
Click on each technology to learn more
Common fuel
Efficiency
Availability
Renewable Balancing
Capital Cost
Fuel Cost
Carbon Emissions
Medium
High
Low
Medium/High
Medium
High
Natural Gas
High
High
Medium
Medium
Medium
Medium
Nuclear
Uranium
Low
High
Low
High
Low
None
Gas Turbine
Natural Gas
Medium
High
High
Low
Medium
Medium
Reciprocating Engine
Natural Gas
High
High
High
Low
Medium
Medium
Click on each technology to learn more
Availability
Fuel Cost
Carbon Emissions
Capital Cost
Low
None
None
Low
Wind
Solar
Low
None
None
Low
Click on each technology to learn more
Capital Cost
Cycle Efficiency
Pumped Hydro
High
Medium
Batteries
Medium/High
High
Click on each fuel type to learn more
Fossil Fuels:
Fuel Cost
Carbon Content
Medium
Low
Natural Gas
Coal
Medium
High
Oil
Oil
High
Medium
Off-Gas
Low
Low
Fuel Availability
Low
High
High
High
Biofuels
Low
Variable
Low
Synthetic Renewable Fuels
High
Low
High
Power is available to be deployed on demand
Dispatchable Power
Amount of power generated that is converted to usable electricity
Efficiency
How often a generation technology is available to produce power
Availability
Ability to ramp power generation up and down easily and quickly
Renewable Balancing
How often a generation technology is available to produce power
Availability
Power is generated at variable times, dependent on seasonal and weather variations
Variable Power
Percentage of electricity that charges the storage asset that is able to be discharged
Cycle Efficiency
Measure of the access to and quantity of the fuel type
Fuel Availability
Methanol
X
Hydrogen
Methane
20%
Renewables reach grid parity in terms of cost with traditional generation.
Storage develops into a more economically and technically feasible strategy. Ancillary services are widely provided by storage.
As intermittent renewable generation increases, inflexible plants become a burden. This is partly due to higher operating costs, partly because of their inflexibility to switch off automatically if there is sufficient renewable generation at any given time.
Flexible thermal capacity replaces inflexible generation to enable faster carbon reduction and more stable grids.
20%
20%
80%
Renewable sources become the new baseload source of energy for the grid.
Storage becomes a key feature in energy shifting and daily grid balancing.
Inflexible fossil-fuel-powered plants are phased out and retired.
Highly flexible thermal capacity is built out to maintain system reliability and minimize use of fossil fuels.
80%
80%
100%
Excess renewable energy is used to generate new synthetic fuels through Power-to-X.
Storage provides daily energy shifting for the grid, supported by Power-to-X for seasonal energy shifting.
No role for inflexible generation.
Synthetic gas and liquid fuels that can easily be stored provide long-term, flexible power for the grid to ensure seasonal security of supply.
100%
100%
California's Current Plan emulates the state’s Integrated Resource Plan, which emphasizes extensive solar and battery storage buildout, with some wind and small additions of geothermal and biomass included. Thermal power is gradually closed down during the transition. This scenario does not reach carbon neutrality even in 2045 because the RPS allows fossil-generation to cover grid losses, which are approximately 8% of the total annual load for the state of California.
Current Plan
An alternate scenario assumes that all fossil gas-fired generation must retire from the system by 2045. This plan would focus on building the whole system on solar, wind and battery storage additions, which brings major challenges on providing security of supply during varying seasonal weather patterns.
Current Plan Without Fossil Thermal
The Optimal Plan provides the lowest transition costs by including flexible thermal generation. The flexible thermal generation assets can be converted as needed to use carbon-neutral fuels produced with excess solar and wind energy through Power-to-X, forming a large, distributed, long-term energy storage system.
Optimal Plan
While there are a variety of paths to achieve broad decarbonization, modeling for California demonstrates that choices made for technology and fuel mixes can have sizeable impacts on CO2 emissions, renewable curtailment and cost. This requires a long-term strategy to pick the right path.
What’s Next?
The Devil is in the Details
Countries, states and communities around the world are charting pathways toward decarbonization. The technologies and strategies used to transition to zero-carbon power systems will impact how quickly clean energy goals can be achieved. As seen in the California case study, optimizing power generation, fuels and storage can greatly reduce costs, lower emissions and maximize the value of renewable energy.
The Path to 100% brings together thought leaders and industry experts to discuss solutions, raise awareness and discover operationally and financially realistic approaches to building a 100% renewable energy future.
11.5
141.3
15.6
6.9
403.1
9.5
3.2
19.1
10.1
11.5
108.7
40.0
2.9
34.0
7.1
Renewable Energy
Energy Storage
Inflexible Generator
Flexible Generator
RES
Example
Landfill Gas
Ethanol
Example
Synthetic Methane
Example
Join Us!
Power is available to be deployed on demand
Dispatchable Power
Amount of power generated that is converted to usable electricity
Efficiency
How often a generation technology is available to produce power
Availability
Ability to ramp power generation up and down easily and quickly
Renewable Balancing
Combined Cycle Gas Turbine
Natural Gas
High
High
Medium
Medium
Medium
Medium
Nuclear
Uranium
Low
High
Low
High
Low
None
Gas Turbine
Natural Gas
Medium
High
High
Low
Medium
Medium
Reciprocating Engine
Natural Gas
High
High
High
Low
Medium
Medium
Fuel Types
Natural Gas
Medium
Low
High
Fuel Cost
Carbon Content
Fuel Availability
Measure of the access to and quantity of the fuel type
Fuel Availability
Fossil Fuels
Coal
Fossil Fuels
Medium
High
High
Oil
Fossil Fuels
High
Medium
High
Off-Gas
Renewable
Low
Low
Low
Landfill Gas
Example
Biofuels
Renewable
Low
Variable
Low
Ethanol
Example
Synthetic Renewable Fuels
Renewable
High
Low
High
Synthetic Methane
Example
Variable Power Generation Technologies
Wind
Low
None
None
Low
Availability
Fuel Cost
Carbon Emissions
Capital Cost
Power is generated at variable times, dependent on seasonal and weather variations
Variable Power
Solar
Low
None
None
Low
Energy Storage Technologies
Pumped Hydro
High
Medium
Capital Cost
Cycle Efficiency
Percentage of electricity that charges the storage asset that is able to be discharged
Cycle Efficiency
Batteries
Medium/High
High
Renewable Energy
Energy Storage
Inflexible Generator
Flexible Generator
Renewable Energy
Energy Storage
Inflexible Generator
Flexible Generator
Renewable Energy
Energy Storage
Inflexible Generator
Flexible Generator
Renewable Energy
Energy Storage
Inflexible Generator
Flexible Generator
Designed & Created by Binh Nguyen
What's Next?
What's Next?
Charting an Optimal Path
Charting an Optimal Path
A California Case Study
A California Case Study
Stages Along the Journey to 100%
Stages Along the Journey to 100%
Overcoming the Variability Challenge with Renewable Fuels
Overcoming the Variability Challenge with Renewable Fuels
The Differing Paths to Decarbonization
The Differing Paths to Decarbonization
What's Next?
What's Next?
Charting an Optimal Path
Charting an Optimal Path
A California Case Study
A California Case Study
Stages Along the Journey to 100%
Stages Along the Journey to 100%
Overcoming the Variability Challenge with Renewable Fuels
Overcoming the Variability Challenge with Renewable Fuels
The Differing Paths to Decarbonization
The Differing Paths to Decarbonization
What's Next?
What's Next?
Charting an Optimal Path
Charting an Optimal Path
A California Case Study
A California Case Study
Stages Along the Journey to 100%
Stages Along the Journey to 100%
Overcoming the Variability Challenge with Renewable Fuels
Overcoming the Variability Challenge with Renewable Fuels
The Differing Paths to Decarbonization
The Differing Paths to Decarbonization
What's Next?
What's Next?
Charting an Optimal Path
Charting an Optimal Path
A California Case Study
A California Case Study
Stages Along the Journey to 100%
Stages Along the Journey to 100%
Overcoming the Variability Challenge with Renewable Fuels
Overcoming the Variability Challenge with Renewable Fuels
The Differing Paths to Decarbonization
The Differing Paths to Decarbonization
What's Next?
What's Next?
Charting an Optimal Path
Charting an Optimal Path
A California Case Study
A California Case Study
Stages Along the Journey to 100%
Stages Along the Journey to 100%
Overcoming the Variability Challenge with Renewable Fuels
Overcoming the Variability Challenge with Renewable Fuels
The Differing Paths to Decarbonization
The Differing Paths to Decarbonization
Designed and created by Wood Mackenzie
View on woodmac.com
