General Questions $($ please CORRECT THE WRONGS$)$

State which of the following is true and which is false then correct the wrong one:

$1-$ In the digester, the anaerobic bacteria start to work after the aerobic bacteria.

$2-$ The source of geothermal heat seems to be the radioactivity of elements at depth of earth.

$3-$ The ideal $C$:$N$ ratio in the biogas production $25.$

$4-$ Hot water at $81C$ can be used to generate electricity at power plant.

$5-$ The acid formers are more delicate than the methane formers.

$6-$ To be economic, the geothermal field must supply steam for about $50$ years.

$7-$ The maximum efficiency of wind turbine is obtained when $\frac{V_{\text{d}\text{o}\text{w}\text{n}}}{V_{up}}=0\mathrm{.}5$

$8-$ The ideal temperature for the operation of the digester is from $25-50C.$

$9-$ In salt pond, there is upper convective layer flowed by lower insulation layer.

$10-$ The sludge from the digester is a perfect fertilizer for the vegetables.

$11-$ The fossil fuel power plants are efficient for peak loads.

$12-$ The drag effect is higher than the lift effect.

$13-$ The minimum spacing between the wind mills is $2R.$

$14-$ The photovoltaic cell produces AC current.

$15-$ The onshore wind mills are higher than the offshore ones.

$16-$ As the temperature increases the performance of PV cells decreases.

$17-$ The wet steam field is the best type of geothermal fields.

$18-$ The output power of wind $=0\mathrm{.}5{}_{\text{a}\text{i}\text{r}}{V}^2{R}^3.$

$19-$ Geothermal energy is the use of water from the depth of earth.

$20-$ The heating value of the biogas is higher than natural gas.

$21-$ Fusion reaction takes place in the sun core.

$22-$ The absorber in the solar heater is made of bright copper.

$23-$ The solar chiller uses the water as refrigerant and Ammonia as absorber$.$

$24-$ The box cooker is the least efficient solar cooker.

$25-$Sensible and latent heat storage are used to store geothermal energy.