Energy Security

Energy Flow Charts

Depicting National-Scale Energy Systems

Lawrence Livermore’s energy flow charts help us understand the structure of the nation’s energy system by illustrating where energy comes from, how much is used in various sectors and how efficiently. Scientists, analysts, decision-makers and the public use the charts to understand energy usage and its effect on the nation’s economic security. The charts also inform opportunities for the development of long-term energy use.

These single-page reference charts contain quantitative data about resource, energy and byproduct flows as infographics, illustrating the complex relationships involved in managing our nation’s resources. For example, users can visualize the amount of natural gas required to generate electricity for eventual residential energy use. Every line’s width is proportional to the amount of energy used by a sector in quadrillions of British Thermal Units (BTUs) — a unit that quantifies all forms of energy, from heat to electricity. Color coding denotes the kind of energy.

flow chart US 2022

Energy flow charts produced by LLNL present information about where the nation’s energy comes from (left), how much is used in various sectors (center) and how efficiently that energy produces end-use services (right).

Energy Flow Chart History

Livermore scientists first adapted the Sankey diagram to depict quantitative data describing U.S. energy generation, flow and end uses. Sankey diagrams date back to the 1800s and were used during the industrial revolution to map the flow of raw materials and finished products into and out of factories. LLNL’s experts turned to the Sankey diagram for its versatility in displaying quantitative information visually.

LLNL produced the first diagrams illustrating U.S. national energy use in the mid-1970s. The changing economics of energy created the need to understand how much energy the United States used from coal, petroleum, nuclear and renewable sources, and how that energy is diverted into commercial-, industrial-, residential- and transportation-related end uses.

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historical flow chart

Many of Lawrence Livermore’s early energy flow charts were visually complex and showed myriad details, such as this 1976 chart which includes information on imported and exported energy. Charts created in the ‘70s and ‘80s were hand-drawn, whereas later versions have been created with various software tools.

UK energy flow 2017

Released Annually

LLNL’s energy flow charts ultimately became a yearly release. The development team combines data from the Energy Information Administration with its own software to generate updated charts of the United States' and individual states' energy use annually. The charts, which are also available for many other countries, depict solar, nuclear, hydroelectric, wind, geothermal, natural gas, coal, biomass and petroleum energy.

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ca freshwater flow 1995

 

Water and Carbon Join the Mix

In the 1990s, at five-year intervals, flow charts of United States water use at the national and state levels became available. These provide a simplified map illustrating usage of fresh and saline surface water and groundwater in domestic, commercial and industrial applications, as well as for irrigation and cooling of power plants. The use of water in cooling power plants, called "thermoelectric cooling," is responsible for more than 50 percent of withdrawals from surface water in some areas of the country.

The water flow charts also track the fate of water, whether it be consumption (mostly by evaporation), return to rivers and lakes or discharge to the ocean.

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co2 emissions 2001

Sources and End Uses

Beginning in the early 2000s, the carbon flow charts mapped carbon emissions from their physical sources — mostly coal, natural gas and petroleum — and displayed the proportion of these emissions attributed to each of the major end uses.

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globe with nodes

Supporting Institutions Across the World

LLNL’s energy and water flow charts are useful to those seeking to understand national-scale energy and water systems. Federal, state and municipal energy organizations utilize the charts, as do private sector and nongovernmental organizations and institutions that perform energy research and development. Middle school teachers and college professors use the charts to engage students, and news organizations refer to them as an easy-to-understand source of information. Now in their fifth decade of production, these charts continue to serve as powerful informational, educational and communications tools.

Read more about Energy Security

Energy Flow Charts
Carbon Initiative
Disaster and Infrastructure Resilience

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