CALC-001

The 29 W/m2 figure is land power density, not beam intensity

Calculation · Cited by CLM-0005 , CLM-0317 , CLM-1452

What this is

This is the project's own arithmetic, published in full so it can be checked rather than taken on trust. It is not a source. Every input it uses is cited to a record, and the conclusion it reaches only carries as far as those inputs do.

Feeds CLM-0005. Answers part of QST-001.

Why it was needed. The UK executive summary (SRC-023 p17) gives 240 W/m2 and 29 W/m2 on the same page. If those were both RF power densities, one of them would be wrong by a factor of eight. An earlier pass here treated the low figure as the beam intensity and drew the opposite conclusion about safety. So the identity of the 29 W/m2 figure had to be established, not assumed.

Inputs, both from SRC-023 p17 and p15:

Quantity	Value	Source
Rectenna dimensions	6.7 km by 13 km, elliptical	CLM-0003
Power delivered to grid	2 GW	CLM-0001, CLM-0003

Working.

Semi-axes:      a = 6.7 / 2 = 3.35 km
                b = 13 / 2  = 6.5 km

Ellipse area:   A = pi * a * b
                  = pi * 3.35 km * 6.5 km
                  = 68.4 km2
                  = 6.84e7 m2

Power per area: 2e9 W / 6.84e7 m2 = 29.2 W/m2

Result: 29.2 W/m2. The source states "about 29W/m2". The match is within rounding.

Conclusion. The 29 W/m2 figure is delivered electrical power divided by rectenna land area. It is a land-use metric, directly comparable with the 10 W/m2 the same page gives for UK terrestrial solar. It is not an RF power density and must never be compared with an exposure limit. The RF figure is 230 to 245 W/m2, and it is a peak.

Three distinct quantities are in play in this question, and conflating any two gives a wrong answer:

Quantity	Value	What it measures
Peak RF beam intensity at rectenna centre	230-245 W/m2	Incident microwave power per unit area
Land power density of delivered electricity	29 W/m2	Grid output per unit ground area
ICNIRP general public reference level	10 W/m2	Screening threshold for human exposure

Cite this

energyaperture.com/calc/calc-001

CALC-001. The working above, not a source document.