Electricity Generation

Introduction

The power sector currently accounts for around 40 percent of annual greenhouse gas emissions to the atmosphere, making it the highest-emitting sector, followed by industry and transportation. Of total worldwide electricity generation, fossil fuels represent 67 percent, nuclear 11 percent, and renewable energy sources just over 24 percent and growing, with the bulk (18 percent) being from large hydropower systems. In the last few years, the competitiveness of renewable sources for electricity generation has continued to increase due to the price evolution and the efficiency improvements of these technologies.

The Drawdown Electricity Generation Sector includes solutions both centralized and decentralized—such as onshore wind power and rooftop solar panels, respectively—and enabling technologies such as electricity storage systems that foster large-scale integration of renewable energy sources.

Solutions

Included in Project Drawdown’s rankings of the 100 most substantive solutions to global warming are 20* of the most impactful solutions for reducing greenhouse gas emissions, or for supporting the adoption and implementation of other solutions, in the Electricity Generation (formerly “Energy”) sector.

The solutions included in this sector have significant positive climate and financial impacts in the short, medium, and long term, since they can replace conventional electricity generation technologies such as coal, natural gas, and oil power plants.

*In the Drawdown book, solar water and methane digesters - small are included in this sector, while landfill methane is under the Buildings and Cities Sector for communication reasons. However, landfill methane was accounted under the modeling framework of the Energy Sector due to the common addressable market. The other two solutions were modeled under the Buildings and Cities Sector.

Electricity Generation Solutions

• Concentrated solar – an electricity generation technology that uses heat provided by direct normal solar irradiance concentrated on a small area, with and without storage.
• Geothermal – geothermal systems for electricity generation, combining both mature technologies and future expectations for enhanced geothermal.
• In-stream hydro – small-scale hydropower technologies under 10 megawatts, including in-stream hydrokinetic systems.
• Methane digesters (large) – large methane digesters associated with agriculture, manure, and wastewater facilities that produce biogas to be used for electricity generation in dedicated biogas or combined heat and power plants.
• Methane digesters (small) – small methane digesters used at the household level to replace fuelwood, charcoal, or even fossil fuel-based cookstoves.
• Micro wind – wind turbines that are rated less than or equal to 100 kilowatts of power capacity.
• Rooftop solar – distributed solar photovoltaic systems that include both residential and community-scale systems generally below 1 megawatt.
• Solar farms – utility-scale solar photovoltaic systems.
• Solar water – solar hot water systems supplementing existing electric and gas heaters in houses.
• Wave and tidal – wave energy converters and tidal systems for electricity generation.
• Wind turbines (offshore) – offshore utility-scale wind power technologies.
• Wind turbines (onshore) – onshore utility-scale wind power technologies.

Transitional Technologies

• Biomass – the use of perennial biomass feedstock for dedicated electricity generation and combined heat and power generation.
• Cogeneration – auto producer combined heat and power systems running on natural gas. Considered here as a transition technology, replacing conventional heat and power technologies and allowing for a greater efficiency and fuel optionality.
• Nuclear – the adoption of nuclear fission in the form of Uranium 235 as used in pressurized water reactors, a type of light-water reactor using low-enriched uranium fuel (the most prevalent form of nuclear energy in 2016).
• Waste-to-energy – the process of combusting waste (typically from the municipal solid waste stream) and converting it to electricity and usable heat.

Enabling Technologies

• Energy storage (distributed) – decentralized systems generally based on battery storage.
• Energy storage (utilities) – includes utility-scale storage units such as gravitational potential energy (pumped hydroelectric), chemical energy (batteries), mechanical energy (flywheels or compressed air energy storage, or hydrogen storage.
• Grid flexibility – represents a portfolio of practices and technologies (system operation, markets, load, flexible generation, networks, and storage) that increase grid efficiency, resilience, and ability to integrate variable renewable energy.
• Microgrids – a localized grouping of electricity sources and loads that normally operates connected to and synchronous with the traditional centralized power grid, but can disconnect and function autonomously as physical and/or economic conditions dictate

Methodology and Integration

Modeling Methodology

Each solution in the Electricity Generation Sector was modeled individually, and then integration was performed to ensure consistency across the sector and with the other sectors. Information gathered and data collected were used to develop solution-specific models that evaluate the potential financial and emission-reduction impacts of each solution when adopted globally from 2020-2050. Models compare a Reference Scenario that assumes current adoption remains at a constant percent of current electricity generation, with high adoption scenarios assuming a reasonably vigorous global adoption path. In doing so, the results reflect the full impact of the solution, i.e. the total 30-year impact of adoption when scaled beyond the solution’s current status.

Figure 1: Project Drawdown Electricity Generation Sector Framework

Total Addressable Market

The Drawdown Electricity Generation Sector solutions that generate electricity share a common market for future adoption, i.e. an electricity generation market. The total addressable market for these solutions is supported by the electricity generation results from a combination of models and scenarios from different sources (AMPERE, 2014; Greenpeace, 2015; IEA, 2016).

Three market prognostication scenarios were driven by comparable scenarios from each source, under distinct climate mitigation expectations (Ambitious, Conservative, and Reference). The Ambitious scenario is calculated from the 2ºC Scenario of IEA ETP 2016; the 450 Scenarios of AMPERE (i.e. GEM-E3, MESSAGE-Macro, and IMAGE/TIMER), and the Energy [R]evolution Scenario from Greenpeace. The Conservative scenario follows the average of the 550 Scenarios of AMPERE models and the 4ºC Scenario of IEA ETP. The Reference Scenario is built by the average of the 6°C Scenario of IEA ETP and the Reference Scenarios of AMPERE models and Greenpeace. The Greenpeace Advanced [R]evolution Scenario was excluded from these calculations since it considers a very ambitious scenario, with 100% renewable electricity generation imposed on the energy system. Therefore, it is not comparable to any of the other scenarios, but is considered as a higher benchmark.

Adoption Scenarios

Three Project Drawdown Electricity Generation Sector scenarios were developed for each solution:

• Plausible Scenario: this scenario represents incremental growth of renewable energy solutions using a high adoption trajectory to 2050, bounded by existing ambitious projections from other global energy systems models.
• Drawdown Scenario:  this scenario is optimized to reach drawdown by 2050 using more ambitious projections from existing sources. The scenario projects a 100% adoption of renewable energy, but includes several transitional renewable technologies that are considered regret/transitional solutions.
• Optimum Scenario: this scenario represents the most optimistic case, in which clean, renewable energy solutions such as wind, solar, and other sources capture 100% of energy generation, with regret/transitional solutions fully phasing out by 2050.

Electricity Generation Sector Integration

The majority of the electricity generation solutions have published adoption projections (either at a regional or global level), which were used to build our scenarios. From an integration point of view, all the energy solutions interact with each other, since they are all framed within a common total addressable market (Figure 2). If the sum of the total individual solutions adoption exceeded the total addressable market, individual adoptions were revised through a pre-defined priority ranking, following other collected alternative pathways. No-regrets solutions were considered as high priority and were not reduced, while regrets and transitional solution adoptions were assumed to be the first to change, if needed. In the Drawdown and Optimum Scenarios, the adoption of transitional and regrets solutions such as nuclear, cogeneration, waste-to-energy, and other waste-related solutions is reduced, with some, having no market share in the electricity generation portfolio by 2050.

Electricity Generation Sector solutions may also interact with other sectors’ solutions both as a whole, since the increased adoption of a solution can increase or reduce the need for electricity, and individually, since solutions in other sectors can influence and constrain the adoption of solutions in this sector. Therefore, through the process of integrating individual solutions with other solutions, the total addressable market for electricity generation technologies was adjusted to account for reduced demand resulting from the growth of more energy-efficient technologies such as LED lighting and heat pumps, as well as increased electrification from other solutions like electric vehicles and high-speed rail. Grid emissions factors were calculated based on the annual mix of different electricity-generating technologies over time. Emissions factors for each technology were determined through a meta-analysis of multiple sources, accounting for direct and indirect emissions.

Results

Mitigation Impacts

Together, Drawdown’s Electricity Generation Sector solutions are ranked second after Food in their global impact on greenhouse gas emissions. They are responsible for 23.41 percent of the mitigation impact in the Plausible Scenario (i.e. 246.14 gigatons of carbon dioxide-equivalent gases from 2020-2050, or 8.2 gigatons per year), 24.97 percent in the Drawdown Scenario (360.21 gigatons, 12.01 gigatons per year), and 21.92 percent in the Optimum Scenario (353.45 gigatons, 11.78 gigatons per year). These impacts include the negative impacts of nuclear and cogeneration adoption reduction in the Drawdown and Optimum Scenarios (Figure 2).

Figure 2: Mitigation Impact by Sector, 2020-2050 (in Gigatons of Carbon Dioxide-Equivalent)

Figure 3: Electricity Generation Sector Plausible Scenario Emissions and Adoption Results, 2020-2050

Looking at individual solutions in the Plausible Scenario (Figure 4), wind turbines (onshore) account for 35 percent of total Energy Sector avoided greenhouse gas emissions from 2020-2050, followed by solar farms (15 percent), rooftop solar photovoltaics (10 percent), geothermal (7 percent), nuclear (7 percent), wind turbines (offshore) (6 percent), and concentrated solar power (5 percent). All the other solutions account for the remaining 15 percent, representing less than 5 percent per solution. Enabling solutions such as storage systems, grid flexibility, and micro grids have no emission and financial impact results, since they have complicated system dynamics and their emissions impacts are accounted for in the individual solutions themselves, preventing double counting. Mitigation impacts for all the three studied scenarios by solution are depicted in Table 1.

Figure 4: Mitigation Impacts by Solution—Plausible Scenario, 2020-2050 (in Gigatons of Carbon Dioxide-Equivalent)

© 2017 Project Drawdown

Table 1: Mitigation Impact of Electricity Generation Sector Solutions Under the Three Studied Scenarios

Financial Impacts

Significant financial benefits are available through the adoption of Drawdown’s Electricity Generation Sector solutions, with over US$4,923.36 billion in total net costs but with US$20,958.67 billion in lifetime savings when compared to conventional electricity generation technologies (Table 2).

Table 2: Net Cost and Net Savings by Solution (in US2014$ Billion) – Plausible Scenario Only

Sector-Level Benchmarks

The International Energy Agency, in their published “Energy Technology Perspectives 2016”, presented the modeling results of three different climate mitigation scenarios for electricity generation and capacity, final energy demand by end use, and total carbon dioxide emissions, among others. These scenarios—6°C, 4°C, and 2°C—are increasingly aggressive for the adoption of renewable energy generation sources and other low-carbon generation technologies such as nuclear, and for efficient technologies in final energy sectors such as buildings and transportation. This technological portfolio induces the compliance with the mitigation goals. The 6°C Scenario (“6 degrees of average temperature increase above pre-industrial levels by 2100”) is closely comparable to the Drawdown Reference Scenario, while the 2°C currently represents their most aggressive scenario. Emissions reduction estimations in the 2°C compared to their 6°C indicate:

• 8.7 gigatons of greenhouse gases emission reduction in 2030, and
• 20.9 gigatons of greenhouse gases emission reduction in 2050.

Overall, Project Drawdown’s Plausible Scenario analysis for the Electricity Generation Sector (only considering the electricity generation technologies) shows an emissions mitigation impact below the IEA's results for a shift from the 6°C to the 2°C Scenario (just over 15.5 gigatons in 2050 compared to the Reference Scenario). The Drawdown Scenario has a similar, but higher impact, with 21.6 gigatons avoided. The Optimum Scenario, with 18.5 gigatons avoided, is below IEA results.

This variation can, in part, by accounted for by the following differences in Project Drawdown and the IEA’s analyses:

• In the Drawdown Plausible Scenario, overall electricity generation is 20 percent higher than the IEA 2°C estimate in 2050. The Plausible Scenario is instead more closely aligned with the scenario results from the AMPERE project and Greenpeace Energy [R]evolution.
• Project Drawdown does not consider power plants with carbon capture and storage in its solutions portfolio. In the 2°C scenario, coal, natural gas, and biomass power plants with carbon capture and storage represents 6 percent of the electricity generation market in 2050.
• Project Drawdown is less ambitious in the reduction of fossil fuels used for electricity generation in 2050, with fossil fuels still representing 30 percent of the electricity generation market then. In the IEA 2°C Scenario, their share is 17 percent. This is a result of the difference between the total addressable market of electricity generation and bottom-up sum of the modeling results of the Drawdown solutions.
• Project Drawdown is less aggressive in using biomass and waste for electricity generation than the IEA (a 3.8 percent market share by 2050 compared to 8.35 percent), since we only account for biomass from perennial crops and without the carbon capture option.
• In Project Drawdown, nuclear is considered a regrets solution, and has a lower market share in 2050 (i.e. 12 percent) than in the IEA 2°C Scenario (i.e. 16.3 percent).
• Project Drawdown is more aggressive in the adoption of renewable energy solutions, including wind, solar photovoltaics, geothermal, and waves and tidal.
• The Drawdown and Optimum Scenarios present mitigation results closer to those from the IEA, since they are more ambitious than the Plausible Scenario. These scenarios push the adoption of renewables toward 100 percent of the electricity generation portfolio, while reducing all fossil fuel generation, transitional, and regrets solutions.

Conclusions and Limitations

The importance of the electricity generation sector is clear for a low-carbon future and for drawdown pathways. In this sector, the cost-effectiveness of emissions reduction is usually higher than in other sectors. Relying on a combination of electricity generation solutions will be of great importance, while acknowledging regional differences in resource potential and the development stages of countries.  The three Drawdown scenarios rank the Electricity Generation Sector highly among the overall group of solutions. In the Plausible Scenario, 3 Electricity Generation solutions are in the top 10; 5 are in the top 20; and 13 are in the top 50. In the Drawdown and Optimum Scenarios, their rankings increase significantly.

The links between this sector and all the others is important, but major interactions occur with energy demand-side sectors like Transport and Buildings and Cities, with energy efficiency and demand reduction solutions affecting the need for increased generation capacity, and with an overall electrification of end uses calling for more electricity generation.