In $2019,$ the European Union $($EU$)$ consumed $403$ Mt$/$yr $($million tonnes per year$)$ of natural

gas $($NG$),$ of which one$-$third was imported from Russia. For this analysis, NG can be

approximated as being pure methane $(C{H}_4).$ The tables below will be useful for your answers.

$($a$)$ Calculate $E_{NG,Ru},$ the annual energy content of NG imported by the EU from Russia in

$2019$ in units of $TW\frac{h}{y}r.$

$($b$)$ Calculate $C_{NG,Ru},$ the annual $C{O}_2$ emissions released by the combustion of NG

imported by the EU from Russia in $2019$ in units of Mt$/$yr$.$

An approach that could be adopted to take climate action and increase energy security is for

the EU to replace the energy delivered by Russian NG imports with green hydrogen produced

by electrolysis powered by wind energy.

$($c$)$ Assuming electrolysis efficiency of $70\%,$ calculate $E_{El,H2},$ the annual electrical energy

needed to produce enough hydrogen to replace the energy delivered by NG imports

from Russia in $2019,$ in units of TWh$/$yr$.$

$($d$)$ Assuming an offshore wind capacity factor $($CF$)$ of $50\%,$ calculate $N_{\text{t}\text{u}\text{r}\text{b}},$ the number of

$15-$MW offshore wind turbines required to produce the electrical energy calculated in

part $($c$).$