Question

total annual usage of energy by humankind is in the order of

Answer 1

$\bold{\text{A healthy human consume energy in a day}} = \bold{2000 Kcal}$
$\bold{\text{we know}}$
1 Kcal = 4200 Joule {approximately }
then, uses of energy by humankind in a day = 2000 × 4200 = 8.4 × 10⁶ Joule

now, 1 annual = 1 year = 365 days
so, annual uses of energy by humankind = uses of energy by humankind in a day × 365days
= 8.4 × 365 × 10⁶ Joule
= 3066 × 10⁶ Joule
= 3.066 × 10⁹ Joule

hence, annual uses of energy by humankind = 3.066 × 10⁹ Joule {approximately }

we know,
kilo = 10³
mega = 10⁶
Giga = 10⁹
Tera = 10¹²
peta = 10¹⁵
exa =10¹⁸
zetta = 10²¹
yotta =10²⁴

now, it is clear that annual uses of energy by humankind = 3.066 Giga Joule
hence,annual uses of energy by humankind is in the order of Giga Joules .

Answer 2

Exa joules

world energy usage is 500 exa joules per year according to NASA image.