Between the Poles

Innovative electric power for a sustainable future

We are not on track to constrain global temperature rise to 2°C let alone 1.5°C.  Therefore we need some innovative technologies to get us back on track.  At the Geography2050: Powering our Future Planet conference at Columbia University in New York, several presentations described innovative, potentially disruptive technologies that could dramatically change how electric power is generated and transmitted.

Wireless power transmission

General Rick Deveraux of Viziv Technologies described a way of transmitting electric power wirelessly using a technology called a Zenneck surface wave that orovides a direct wireless connection from a generator to a load. It supports much higher field strengths than conventional Hertzian waves and follows the Earth's curvature. Viziv is currently working in a global demonstration project that involves building a fiberglass transmission tower and field intensity monitoring stations around the globe. An advantage of this technology is that it could deliver power to people who are currently off grid. Testing of this configuration starts within 30 days and actual power delivery next year.

On demand emissionless power generation

Christofer Mowry of General Fusion, described how nuclear fusion can provide energy dense, low environmental impact, manufacturable, and dispatchable power generation. In other words a fusion installation requires very little land and can be placed near the sources of load avoiding long haul transmission lines. There are no emissions and very little waste. It does not require fuels that are constrained by supply like fission does. It can supply large volumes of power on demand. The amount of investment in fusion has increased dramatically since about 2007.

Cell phones not requiring recharging

Frank Prautzsch of Velocity Technology Partners described what is potentially a disruptive technology that could affect everyone carrying a cell phone. Thermionic energy conversion (TEC) provides a way of generating power from ambient thermal energy using nano technology. Developed by Birmingham Technologies the Nano-Boxx consists of two metal plates composed of different metals that are placed less than 10 nanometers apart with a nanofluid in between. An electric current is generated when electrons from one plate vaporize and collect on the other plate. The device that was shown was the size of a postage stamp. By stacking them the device can scale from milliwatts to megawatts. 8 to 9 of these will power a cell phone, 800-900 a satellite. It can produce power for about eleven years without charging. To date it has been tested by using it to power an LG Nexus cell phone for the past few years. It is cheaper to produce than a lithium ion battery, has 40% more energy density, and has no emissions.

Powering the world for a million years

Kevan Weaver of the Idaho National Laboratory outlined the results of their calculations that advanced reactors would enable depleted uranium stockpiles and known reserves of uranium to supply 80% of the world's electric power demand for about 2000 years with no carbon emissions. If you add the uranium in the oceans there is enough to provide a source of power for a million years. China and India are investing heavily in fission power generation.  Micro-reactors and small modular reactors can provide safe power to data centers, remote locations that are off-grid, and locations where fossil and other fuels are expensive. The latest reactors (generation III and III+) are much safer than the first and second generation reactors like those at Fukushima, primarily because they do not require an external source of power to cool them in the case of an emergency shutdown.

Carbon dioxide emissions from electric power generation decoupled from economic growth in US

As a rule of thumb increasing electric power generation is closely coupled with economic expansion.  Between 2005 and 2017 the U.S. economy as measured by real GDP expanded by about 20 % from $15 trillion to $18 trillion. New data from the U.S. Energy Information administration (EIA) reveals that over this same period, emissions from power generation dropped primarily because of flat demand which is evidence of a decoupling between economic growth and power generation.

Data from the EIA reveals that during this time US power generation remained flat, but the makeup of U.S. power generation changed significantly.  Generation from natural gas now exceeds that from coal and generation from wind, solar and other renewable sources now exceeds hydroelectric generation.

With respect to emissions the change is even more impressive.  In a business as usual scenario assuming that demand continued to increase as it had prior to 2005, energy intensity (the energy required to produce a dollar of GDP) had remained at its 2005 value, and the energy mix had remained at its 2005 value, the expected emissions from electric power generation would have been about 3,043 MMmt (million metric tonnes). In 2017 actual emissions were much less, about 1,744 MMmt.  About half of the drop in emissions in 2017 compared to the projected business as usual emissions was due to less demand (654 MMmt).  Since the economy expanded over this time this is attributable to a drop in energy intensity and is evidence of decoupling of economic growth from power generation.  The other important factors were switching among fuels, primarily switching from coal to natural gas (329 MMmt) and replacing fossil fuels with non-hydro renewables (316 MMmt). 

In 2017 actual emissions from power generation were 43% less than that projected in the business as usual scenario and 28% below 2005 emissions. This is important progress toward the Paris accord targets (which the U.S. has dropped out of) since emissions from electricity generation are about 28% of U.S. total emissions.

Department of Energy: Increased renewable power generation does not compromise grid reliability

On April 14, 2017 Secretary of Energy Rick Perry issued a memorandum directing preparation of a study to examine whether the retirement of many baseload plants (mostly coal-fired) are premature and whether their retirement reduces grid resilience. The Secretary directed the Department of Energy to conduct a rigorous analysis to answer these questions.  The final report is expected in a few weeks, but a draft has been obtained by Reuters.

Major drivers of retirement: High natural gas availability and low electricity demand

Based on an extensive review of the electric power system evolution and events over the past thirty years and analysis of DOE and other data sources using basic supply and demand principles, a preliminary draft of the study concluded that many baseload retirements are not premature because they are consistent with observed market forces, primarily low natural gas prices and lower than expected electricity demand.   Environmental regulations, state policies and competition with renewables are minor factors that have exacerbated and accelerated these trends. Since 2002 most baseload power plant retirements were victims of over capacity and relatively high operating costs that often reflect the age of the plants. The first tranche of fossil fuel retirements occurred before the explosive growth of renewable generation over the past five years.

Costly environmental regulations and subsidized renewable generation have exacerbated and accelerated baseload plant retirements, but these factors played minor roles compared to the long-standing drop in electricity demand relative to expectations and years of low electricity prices driven by high natural gas availability. While coal and nuclear power used to provide the bulk of U.S. electricity, wholesale electricity prices have closely tracked natural gas prices for the past 15 years beginning about the time that shale gas and oil entered the scene. Low natural gas prices and the fact that new, high efficiency natural gas generation and the pipelines required to provide fuel could be built rapidly helped grow natural gas plants relative to coal and nuclear.  Renewables didn't cause retirements - baseload retirements due to age, inefficiency, and inability to compete began appearing in the early 2000s well before any significant levels of wind and solar generation - but competition with renewables has exacerbated the problem.

Impact on grid reliability

Numerous technical studies for most regions of the nation indicate that significantly higher levels of renewable energy can be integrated without compromising system reliability.                

Region	Minimum level of renewable energy penetration (energy generated, not energy capacity)
New England	24%
PJM (Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and the District of Columbia)	30%
Midwest	25%
ERCOT
California	50%
Eastern US	30%
Western US	33% (wind and solar), 40% (all renewables)
Hawaii	100%
National	50%

The study outlines four principal ways to maintain and enhance bulk power system reliability: technology, rules and standards, business practices and last and most expensively, using high levels of transmission and generation.

• Technology advancements now enable wind plants to provide a full spectrum of balancing services. For example, Xcel Energy requires turbines to be on automatic generation control, which allows computerized control system to directly control wind generation output.
• FERC, NERC, and the RTOs and ISOs have undertaken several initiatives to use rules, standards, and grid codes to modify requirements for both interconnectioning renewables and legacy power plants to improve reliability.
• Bonneville Power Administration provides an example of how to integrate wind energy effectively using operational and business practices rather than bringing on more generation reserves. BPA dealt with the reliability risk by limiting the amount of transmission available to the wind fleet (control and curtailment), charging for using hydropower to balance wind generation, and setting a penalty rate to encourage accurate wind generation scheduling.

New era for big transmission lines in the U.S.

Big transmission lines have not been built in the U.S. for decades.  Now there are multiple projects all driven by bringing renewable energy from remote locations to market.  At the CG/LA Global Infrastructure Leadership Forum today two companies presented on major transmission projects that managed to overcome the regulatory and societal hurdles that are the major challenges for new transmission lines.  On average in the U.S. infrastructure projects require 9.5 years to get the required permitting. These projects include have been fully permitted after 8 years or less partly because of their innovative solution to people's reaction to unsightly transmission towers.

The first project (Champlain Hudson Power Express) is a 1,000 MW high voltage direct current (HVDC) line over 333 miles from Quebec to New York City.  Quebec power is nearly 100% hydro and this power will help both the State of New York and the City of New York reach their clean energy objectives.  In addition as the Indian Point nuclear power plant is scheduled to be shutdown, this power line from Quebec will cover about half of the power that will be lost with the Indian Point shutdown.  The innovative feature of this power line is that it is entirely underground, or to put it more accurately, underground and underwater.  It's route is across Lake Champlain and down the Hudson River.  This has made it much easier to acquire the required right of way and complete permitting because one of the biggest issues with transmission lines is the visibility of pylons and lines.  

A second project (New England Clean Power Link)has taken the same approach to bring a 1,000 MW buried HVDC to Vermont.  This line is 154 miles long, is completely underwater and underground and is fully permitted.  This has been in development only since 2013 and is scheduled to be in service by 2020.  That is remarkably fast for a transmission line in the U.S.

The third project is one of several being developed by Clean Line. This is the Plains and Eastern Clean LIne Line linking wind generation in the Texas panhandle to Arkansas and Tennessee.  This is a HVDC line HVDC line delivering 500 MW to Arkansas and 3,500 MW to western Tennessee. This is a traditional above ground transmission line which made getting all the stakeholders on side was more challenging than for undergound lines. Clean Line credits its communications department, which held thousands of meeting with stakeholders, for its success in completing the permitting in only 8 years.  It is expected that construction on this line will begin by the end of the year.  This remarkable project won two awards at the CG/LA conference including Strategic Project of the Year.

Siting uses geotechnology intensively.  In both cases the project people had to be willing and able to optimize the routing based on stakeholder input.  For example, one stakeholder wanted the line to pass along his southern property boundary instead of the northern boundary.  Micro siting and the ability to change the route on a moment's notice requires accessible, precision locating and the ability to show stakeholders exactly where the line would go.  Geospatial technology was essential to all three of these projects.

U.S. governors urge Trump to support renewable energy and grid modernization

The Governors' Wind and Solar Energy Coalition (GWSC), representing 20 U.S. state governors, both Democratic and Republican, sent a letter to President Trump presenting the benefits of renewable energy, arguing for a Federal commitment to support renewable energy and grid modernization, analytics and simulation and to streamline regulation of the grid.

The letter outlines how renewable energy is providing jobs and investment to low-income U.S. counties. For example, U.S. wind facilities pay rural landowners $222 million a year, with most of it going to landowners in areas with below-average incomes. $100 billion has been invested by companies in low-income counties, where some 70 percent of the nation’s wind farms are located.  Wind energy currently generates five percent of U.S. power demand. Last year, the country’s solar industry employed over 200,000 and added 31,000 new  jobs. Most of the installations are in rural areas and have provided landowners another income option.

Furthemore, the letter argues that any national infrastructure legislation introduced in Congress should provide significant funding for grid modernization. The complexity of the U.S. aging, multi-state grid makes the need for sophisticated modeling and analysis critically important. The GWSC asks the President to create a new state-federal task force, in conjunction with the Federal Energy Regulatory Commission (FERC) and the National Laboratories, to examine options to  modernize and streamline state and federal regulatory processes.

The GWSC suggests that if the United States does not continue robust federal research and development programs in wind  and solar energy, China will assume leadership and see most of the economic benefits in these critical technologies. The Governors make the case that the growth of the renewable energy industry is an American success story built on federal research and development, state policy leadership, private sector investment, and ingenuity.

OpenGridMap: open, crowdsourced project to map power grid infrastructure

Earlier this year on a Sunday renewable power supplied almost all of Germany’s power demand, a major milestone in Germany's “Energiewende” policy.  The transformation of the grid (called by some a revolution) is being driven by distributed energy (DER) and smart devices.  It requires profound changes to how we monitor and manage the power grid and to be able to understand the impact of  the integration of more distributed intermittent sources and new consumer, industrial, and commercial electronics requires data and tools that only exist partially today.

If you are familiar with OpenStreetMap (OSM), then the OpenGridMap project is not that different except that it focusses on mapping electric power infrastructure instead of transportation.  I had heard rumours about an OSM-like project in Germany to map electric power infrastructure several years ago, but was unable to find more information about it.  OpenGridMap is an new open community that crowdsources power grid geospatial location and related data to be used for research purposes.  The goal is to collect reliable grid data to enable researchers to conduct simulation studies. OpenGridMap is intended to support the entire process from data collection to making grid data available for various applications. An OpenGridMap app for Android for people interested in helping to collect grid infrastructure data is available on Playstore.

Using OpenGridMap data analytics developed at the Technical University (TU) Munich generates a power grid model in the form of a Common Information Model (CIM) description file which provides the basis for a power grid simulation model.  Experiments with OpenGridMap data have demonstrated the effectiveness of this approach for grid modeling and simulation.  It is expected that as more data is collected it will be possible to generate power grid simulations of larger size, more variety and more accuracy than the currently available state-of-the-art test power grids.

The project was initiated by Professor Hans-Arno Jacobsen, Chair of Business Information Systems, and José Rivera at the Technical University of Munich.  It is supported by a German Federal Ministry of Education and Research grant and the Alexander von Humbolt Foundation.  Collaborators include Siemens AG, World Bank's ESMAP, the Technical University Berlin's VEREDELE project and Universität Erlangen-Nürnberg (FAU) KOSiNeK project.

Related links

OpenGridMap: An Open Platform for Inferring Power Grids with Crowdsourced Data, José Rivera , Christoph Goebel, David Sardari, Hans-Arno Jacobsen, Energy Informatics, Volume 9424 of the series Lecture Notes in Computer Science pp 179-191, 06 January 2016

OpenGridMap: towards automatic power grid simulation model generation from crowdsourced data Rivera, J., Leimhofer, J. & Jacobsen, HA. Comput Sci Res Dev (2016). doi:10.1007/s00450-016-0317-4

Canada prices carbon

The Canadian government has announced a a pan-Canadian policy on climate change including a floor price on carbon beginning in 2018.  The Paris agreement commits Canada to a 30 per cent reduction in greenhouse gases from 2005 levels by 2030.  The floor price of carbon starts at a minimum of $10 per tonne of GHG emissions in 2018, rising by $10 each year to $50 per tonne by 2022. All of the money raised will be returned to the respective provinces, who can, in turn, distribute those funds to their citizens in the form of tax cuts.  The federal program will be compatible with existing provincial carbon pricing programs.  Ontario and Quebec already have a cap-and-trade program.  British Columbia already has a carbon tax of $30 per tonne.  Alberta has announced it will have a $20 per tonne carbon tax beginning in 2017, rising to $30 a tonne in 2018.  Eight of ten provinces have signed onto the agreement.  The federal government said it will impose a carbon price on the two non-signatory jurisdictions, Saskatchewan and Manitoba. The final agreement includes a list of already announced measures including new building codes to improve building energy efficiency, more charging stations for electric cars, expanding clean electricity sources and upgrading power grids.

Net zero energy building market growing rapidly

Energy efficiency

The IEA has projected that a cumulative $44 trillion in investment will be needed in the global energy supply over the next 15 years. Another $23 trillion will be required for energy efficiency improvements.  Worldwide 40% of energy is consumed by buildings.  In the U.S. 70 % of electric power goes to buildings.  Measures aimed at improving the efficiency of buildings have been introduced in Europe, the U.S., Japan and other jurisdictions.

Zero energy buildings

Zero energy buildings are loosely defined as buildings that generate as much energy as they consume.  But there is as yet no single standards body defining what a zero energy building is.  Different countries and even within the same country different bodies define zero energy buildings in different ways.  According to a new report from Navigant Research, global zero energy building revenue is projected to grow from less than $100 billion in 2016 to $1.4 trillion by 2035.

Nearly zero energy buildings in the E.U.

The European Union (EU) has taken a leading role in focussing energy conservation efforts on the energy efficiency of buildings.  The EU has mandatory carbon emission reduction standards, referred to as the 20-20-20 standard, which among other things requires the EU to improve energy efficiency by 20% by 2020.  Another important objective is reducing its dependence on imported energy, which currently accounts for half of EU energy usage.  In 2002 the European Commission promulgated the Energy Performance of Buildings Directive (EPBD) which requires all EU member states to upgrade their building regulations and to introduce energy certification schemes for buildings.  About a year ago the European Commission (EC) proposed a new Energy Efficiency Directive (EED) , also known as the EPBD recast, which imposes a legal obligation for all member states to establish energy saving schemes, with the public sector leading by example.

Energy efficiency is especially critical for Germany which not only needs to comply with the 20-20-20 standard, but also to find energy sources to replace its (non-emitting) nuclear power plants that are scheduled to be closed by 2022.  In Germany buildings currently account for 40 percent of power consumption and a third of CO2 emissions. The German 40 year master plan calls for aggressive energy efficiency policies including new insulation standards and for all buildings in Germany to be refurbished in line with the new insulation standards by 2050, reducing energy requirements for heating by 20 percent by 2020 and by 80 percent by 2050, and providing tax relief on energy taxes to companies contributing to energy savings.

A major area of focus in the EU is “nearly zero energy” buildings.  A nearly zero energy building on average over a year generates as much energy from renewable energy sources as it consumes.  For new buildings, the EPBD recast fixes 2020/2021 as the deadline for all new buildings to be designed to be nearly zero energy.  For public buildings the deadline is even sooner, by 2018/2019.

Zero emissions buildings in Japan

Japan‘s announced mid-term emission reduction target is to cut Japan's GHG emissions by 25% by 2020 compared with 1990, subject to international negotiations.  But Japan has said that it plans to revise this target in light of the Fukushima accident and presumably in light of the decision to shut down its nuclear power plants by 2040.  According to an analysis by the Ministry of Economy, Trade and Industry (METI), the largest reduction will need to be realized in commercial sector, by about 27%. Residential/commercial-sector accounts for 30% or more of final energy consumption and has increased remarkably compared to the industrial and transportation sectors.  Energy saving measures for commercial buildings are urgently required, since the commercial sector including office buildings consumes more than half of total energy consumption in the residential/commercial sector. Moreover its growth has been more striking than that of the residential sector.

The Government of Japan put forward its "zero emissions buildings" target in April, 2009.  It defines a zero emissions building (ZEB) as one that has net zero CO2 emissions on an annual basis through energy efficiency and renewable energy generation on-site.  The announced objective ia that all new public buildings will be zero emissions by 2030.

Zero net energy buildings in the U.S.

The U.S. Energy Independence and Security Act of 2007 (EISA 2007) requires that by 2030 all new Federal facilities must be "zero net energy" (ZNE) buildings.  On October 19, 2007, the California Public Utilities Commission (CPUC) adopted aggressive targets for ZNE

• All new residential construction in California will be zero net energy by 2020
• All new commercial construction in California will be zero net energy by 2030
• 50% of existing commercial buildings will be retrofit to ZNE by 2030.

According to the New Buildings Institute (NBI) there are 332 ZNE (zero net energy) verified and emerging commercial and multifamily buildings in the U.S. and Canada. The ZNE buildings on this list have either achieved or committed to the goal of producing as much renewable energy onsite as they consume over the course of a year.

Be Inspired Awards 2016: 3D design helps 1.8 GW hydro project generate power 10 months ahead of schedule

At the Year in Infrastructure 2016 conference in London, the Be Inspired Awards attracted over 300 submissions.  Many of these were impressive in how they applied digital technology to designing, constructing and maintaining buildings and infrastructure. The winner of this year's Power Generation sector award was a remarkable full-lifecycle BIM project for a hydropower projects in a remote part of Yunnan, China.

Longkaikou hydro-power station is located in Heqing County, Dali Autonomous Prefecture, Yunnan Province.  The primary focus of the project is generating electricity, but it also supports irrigation, water supply and flood control. The dam is a concrete gravity dam.  There are five turbine-generator units with a total installed capacity a 1,800MW.  Construction began in 2007 and in 2012 the reservoir began to fill.  By January 2014, all power generation units were fully operational.

The Longkaikou hydropower station is the first hydropower station in China that fully employed 3D digital design technology from the start of the project. Design of the power plant began in 2005.  More than 20 different disciplines were involved including geology, hydraulic, plant, water diversion, construction, road & bridge, metal structure, hydro-machinery, electrical, HVAC, and drainage.

PowerChina Huadong Engineering Corporation  (Huadong Institute) was responsible for design of the project.  It was the first institute in China's hydropower industry who migrated from traditional 2D CAD design to 3D collaborative design.  The project employed digital model throughout the lifecycle.  The project survey, design, construction and operation are all digital.  This is considered a revolutionary technical innovation in the Chinese hydropower industry.

3D digital design greartly improved the efficiency of the design process by enabling collaborative design.  Clashes between designs from different design teams were greatly reduced and product quality was significantly improved.  For example, equipment clashes were reduced by 95%.  The amount of on-site design change was reduced by over 80%. In the design of some equipment systems and the preparation of drawings, design time reduced by more than 50%.

The efficiency of collaboration between disciplines was significantly improved.  Being able to view designs from different design teams in one unified model greatly reduces the time for review and signoff. In the past, it usually took more than one month to review and signoff a power plant's layout drawings.  With 3D modeling, collaboration between disciplines improved design efficiency by over 40%.

The digital design platform made it possible to assess alternative design scenarios in order optimize designs. It is estimated that optimization of the dam's foundation surface construction based on a 3D geological model saved about CNY 194 million in engineering costs. The dam's foundation's is unique and complex and required innovative engineering because there was no previous model to follow. Using a 3D model of the geology (digital terrain model) made it possible to design and compare alternative construction scenarios to optimize the design. As a result of design optimization, the project was completed about 10 months ahead of schedule, creating economic benefits of up to CNY 1.79 billion.

With the use of 3D digital design and geo-coordination, the Longkaikou Hydropower Station project not only enjoyed a shortened design cycle, improved project and service quality, and reduced construction costs, but also provided the basis for digital operation and maintenance of the facility by the owner. Geo-coordination, a term minted by Bentley, is key to integrating data from many different sources including reality modeling, 3D building models and associated information.  Bentley recognized the value of geo-coordination very early on. With all Bentley applications in the last 12 years every infrastructure asset has geo-coordination in the form of real world x y z coordinates. It is recognized as essential for full-lifecycle (design, build, maintain and operate) BIM.  In this project it was fundamental not only for integrating the dam and hydropower plant design and the digital terrain model, but also for making it possible to reuse the BIM model and associated data during operation and maintenance.

The design was praised by both the construction contractor and the owner.  It enhanced the core competitiveness and reputuation of the Huadong Institute, establishing a strong foundation for winning future hydropower projects.

IEA World Energy Outlook projects world warming greater than 2° C based on COP21 committments

The International Energy Agency (IEA) has issued its annual World Energy Outlook 2016.  The IEA has examined several scenarios. All the Paris COP21 climate pledges from 190 countries have been incorporated into its main scenario.  (It does not include any assessment of what the Trump administration may do with respect to the COP21 committments made by the world's second largest emitter.) It has projected that this scenario will actually result in 2.7 °C of warming.  A scenario, called the 450 Scenario, with a 50% probability of limiting global warming to 2 ° C was also examined.

In its main scenario which includes emission reductions from COP21 pledges, the IEA projects a 30% rise in global energy demand to 2040.  In 2040 it is projected that 60% of all new power generation capacity will come from renewables.  In 2040 renewables are projected to represent 37% of all power generation.  By 2040 most renewables-based generation is projected to be competitive without subsidies. Solar PV is expected to see a further 40-70% reduction in cost by 2040 and onshore wind by an additional 10-25%. However, fossil fuel generation continues to be important. Natural gas consumption is projected to rise by 50%.  Growth in coal use essentially stops while growth in nuclearpower is limited to China.

Energy-related CO2 emissions plateaued in 2015 mainly because of a 1.8% improvement in the energy intensity of the global economy.   This is partly because a growing proportion of the $1.8 trillion currently invested in energy annually is directed to renewables.  But the IEA projects that even with the COP21 commitments energy-related emissions will continue to grow by 0.5% per year.

It is projected that a cumulative $44 trillion in investment will be needed in the global energy supply over the next 15 years.  60% of this will go to oil, gas and coal extraction and supply, including power plants using these fuels, and nearly 20% to renewable energies. Another $23 trillion will be required for energy efficiency improvements.   For comparison over the last 15 years, 70% of total energy supply investment went to fossil fuels.   This scenario requires a significant reallocation of capital from fossil fuels to renewables. This is aided by dropping fossil fuel subsidies.  In 2015 the value of fossil-fuel consumption subsidies dropped to $325 billion, down from $500 billion the previous year.

The IEA projects that the COP21 commitments will slow the projected rise in global energy-related CO2 emissions.  However, it does not believe that this is enough to limit warming to less than 2 °C.  The IEA's 450 Scenario, which is based on a 50 % probability of limiting warming to under 2 °C, requires a further major reallocation of investment capital going to the energy sector. A greater proportion of the $40 trillion in cumulative energy supply investment has to move from fossil fuels and towards renewables and other low carbon investments in nuclear and carbon capture and storage so that the share going to fossil fuels would drop to about a third. In addition, $35 trillion is needed for improvements in energy efficiency - that's $12 trillion more compared with the main scenario. The 450 Scenario implies that before the end of this century, the energy sector must become carbon-neutral.  That means all residual emissions from fuel combustion are either captured and stored, or offset by technologies that remove carbon from the atmosphere.