# Ragone plot

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{{Short description|Plot for comparing energy density of energy-storing devices}}
[[File:Lithium Ion Capacitor Chart.png|thumb|350px|Ragone plot showing [specific energy](/source/specific_energy) versus [specific power](/source/Power-to-weight_ratio) for various energy-storing devices]]

A '''Ragone plot''' ({{IPAc-en|r|@|'|g|o:|n|iː}} {{respell|rə|GOH|nee}})<ref>{{cite web|url= http://www.case.edu/its/archives/presidents/ragsummary.htm |title= President David V. Ragone |website= [Case Western Reserve University](/source/Case_Western_Reserve_University) |accessdate= 21 April 2015}}</ref> is a plot used for comparing the energy density of various energy-storing devices. On such a chart the values of [specific energy](/source/specific_energy) (in [W·h](/source/Watt-hour)/[kg](/source/kg)) are plotted versus [specific power](/source/Power-to-weight_ratio) (in W/kg). Both axes are [logarithmic](/source/logarithmic_scale), which allows comparing performance of very different devices. Ragone plots can reveal information about gravimetric energy density, but do not convey details about [volumetric energy density](/source/volumetric_energy_density).

The Ragone plot was first used to compare performance of [batteries](/source/electric_battery).<ref>{{cite journal |last=Ragone |first=D. V. |year=1968 |title=Review of Battery Systems for Electrically Powered Vehicles |url=https://saemobilus.sae.org/papers/review-battery-systems-electrically-powered-vehicles-680453 |journal=SAE Technical Paper |series=SAE Technical Paper Series |volume=1 |doi=10.4271/680453 |id=680453 |url-access=subscription}}</ref> However, it is suitable for comparing any energy-storage devices,<ref name=Theory>{{cite journal |first1= Thomas |last1= Christen |first2= Martin W. |last2= Carlen |year= 2000 |url= https://www.researchgate.net/publication/229122460 |title= Theory of Ragone plots |journal= [Journal of Power Sources](/source/Journal_of_Power_Sources) |volume= 91 |issue= 2 |pages= 210–216 |doi= 10.1016/S0378-7753(00)00474-2 |bibcode= 2000JPS....91..210C }}</ref> as well as energy devices such as engines, gas turbines, and fuel cells.<ref>{{Cite journal |title=Analogical understanding of the Ragone plot and a new categorization of energy device |last=Lee |first=Sang C. |author2=Woo Young Jung |journal=Energy Procedia |volume=88 |date=June 2016 |pages=526–530 |doi=10.1016/j.egypro.2016.06.073 |doi-access=free}}</ref>  The plot is named after [David V. Ragone](/source/David_V._Ragone).<ref name=Theory />

Conceptually, the vertical axis describes how much [energy](/source/energy) is available per unit mass, while the horizontal axis shows how quickly that energy can be delivered, otherwise known as [power](/source/Power_(physics)) per unit mass. A point in a Ragone plot represents a particular energy device or technology.

The amount of time (in hours) that a device can operate at its rated power is given by the ratio of its specific energy (Y-axis) to its specific power (X-axis). This relationship holds regardless of the device's overall size, as a larger device would have proportional increases in both energy and power. Consequently, the [iso curves](/source/contour_line) (constant operating time) in a Ragone plot are straight lines. 

For electrical systems, the following equations are relevant:

:<math>\text{specific energy} = \frac{V \times I \times t}m,</math>

:<math>\text{specific power} = \frac{V \times I}m,</math>

where ''V'' is [voltage](/source/voltage) (V), ''I'' [electric current](/source/electric_current) (A), ''t'' [time](/source/time) (s) and ''m'' [mass](/source/mass) (kg).

==See also==
* [von Kármán–Gabrielli diagram](/source/von_K%C3%A1rm%C3%A1n%E2%80%93Gabrielli_diagram)

==References==
{{Reflist}}

{{Commons category|Ragone plot}}

{{Authority control}}
{{Use dmy dates|date=March 2020}}

{{DEFAULTSORT:Ragone Plot}}
Category:Capacitors
Category:Electric battery
Category:Charts

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Adapted from the Wikipedia article [Ragone plot](https://en.wikipedia.org/wiki/Ragone_plot) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ragone_plot?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.