Partial radiogenic heat model for Earth revealed by geoneutrino measurements

Abstract

The Earth has cooled since its formation, yet the decay of radiogenic isotopes, and in particular uranium, thorium and potassium, in the planet's interior provides a continuing heat source. The current total heat flux from the Earth to space is 44.2 ± 1.0 TW, but the relative contributions from residual primordial heat and radiogenic decay remain uncertain. However, radiogenic decay can be estimated from the flux of geoneutrinos, electrically neutral particles that are emitted during radioactive decay and can pass through the Earth virtually unaffected. Here we combine precise measurements of the geoneutrino flux from the Kamioka Liquid-Scintillator Antineutrino Detector, Japan, with existing measurements from the Borexino detector, Italy. We find that decay of uranium-238 and thorium-232 together contribute 20.0 +8.8 −8.6 TW to Earth's heat flux. The neutrinos emitted from the decay of potassium-40 are below the limits of detection in our experiments, but are known to contribute 4 TW. Taken together, our observations indicate that heat from radioactive decay contributes about half of Earth's total heat flux. We therefore conclude that Earth's primordial heat supply has not yet been exhausted.

Multi-Criteria Decision-Making Approach for the Sustainable Autonomous Energy Generation through Renewable Sources. Studying Zakynthos Island in Greece

“…Is limited to the first 3 kilometers from the earth's surface and can relatively easily be exploited. It is relatively mild, alternative and may cover a significant part of the energy needs (Gando et al, 2011). The greenhouse gas emissions generated from geothermal electric stations are on average 50gs CO2/kW-h, or approximately 5% less than the conventional coal based energy production stations (Moomaw et al, 2011).…”

Review article "Geo-neutrinos"

“…The histograms indicate the backgrounds, whereas the best fit (including geo-neutrinos) is shown in blue. achieved by both Borexino (Bellini et al, 2010) and Kam-LAND (Gando et al, 2011). The observed energy spectra of the prompt candidates are shown in Figs.…”

“…Horizontal solid red lines: predictions of the Fully Radiogenic and Minimal Radiogenic Earth (only the crust contribution considered) models. (Gando et al, 2011): ∆χ 2 -profile from the fit to the total number of geo-neutrino events. The BSE model from (Enomoto et al, 2007) prediction is represented by the shaded bend.…”

“…The fully radiogenic, homogeneous hypothesis is therefore excluded at 97.2% C.L. (Gando et al, 2011): Prompt energy spectrum of low-energy anti-neutrino spectrum. The histograms indicate the backgrounds, whereas the best fit (including geo-neutrinos) is shown in blue.…”

Reviewing the relationship between thermal reservoir parameters and geothermal energy output

“…This heat is produced in approximately equal proportions from high core temperatures caused by the initial formation of the planet and the radioactive decay of matter [1]. This energy can be utilized by pumping geothermal fluids, heated gases or liquids found in deep thermal reservoirs, into geothermal systems that contain steam-powered turbines to produce electricity that is directly supplied to the grid.…”