Power systems — solar arrays (I-V curve, power tracking), batteries (DoD, cycles), RTG: Foundations

3.6.22 · D1 · Physics › Spacecraft Structures & Systems Engineering › Power systems — solar arrays (I-V curve, power tracking), ba

Is page par yeh assume kiya gaya hai ki tumne kuch bhi nahi dekha. Hum har woh letter build karte hain jo parent note use karta hai, ek ek karke, taaki jab tum $I = I_{L} - I_{0} (e^{V / n V_{T}} - 1)$ se milo, to usmein har symbol tumhara apna ho.

Part 1 — Char quantities jo flow karti hain

Kisi bhi solar cell se pehle, humein char rozmarra ki physical ideas chahiye. Ek water system ki picture banao: yeh analogy humein poore raaste le jaayegi.

Topic ko in sab ki zaroorat kyun hai: Spacecraft par har box — radios, heaters, computers — ek khaas number of watts maangta hai. Kyunki $P = V I$ hai, power system ko sahi voltage aur current saath mein deliver karni chahiye. Poori "I-V curve" ki kahaani isi ke baare mein hai ki ek solar cell actually kaun se $(V, I)$ pairs offer kar sakti hai.

Part 2 — Energy vs. power, aur "-hour" units

Power ek rate hai. Energy woh total amount hai jo deliver hoti hai — power ko time se multiply karo.

Part 3 — Percentages, ratios, aur logarithms

Parent note mein do mathematical tools baar baar aate hain. Inhe hum abhi earn karte hain.

Topic ko $ln$ aur $e$ ki zaroorat kyun hai: Solar cell ke andar diode ka ek exponential current-voltage law hota hai, $e^{V / n V_{T}}$ . Iska inverse — logarithm — bilkul wahi cheez hai jo hume open-circuit voltage $V_{oc} \approx n V_{T} ln (I_{L} / I_{0} + 1)$ solve karne deti hai. Exponential kehta hai "voltage badhne par current explode hoti hai"; logarithm isse "undo" karke voltage recover karta hai. Diode is law ko kyun follow karta hai, iske liye Semiconductor Physics dekho.

Part 4 — Solar-cell equation ke andar ke symbols

Ab har ingredient define ho chuka hai. Yahan parent note ka core formula hai, jisme har symbol ko saade alfaaz mein naam diya gaya hai:

Symbol	Saade alfaaz	Picture
$I$	current jo cell load ko deliver karta hai	cell se bahar flow rate
$I_{L}$	photocurrent — sunlight se charge free hoti hai	brightness se set ek steady pump
$I_{0}$	dark saturation current — bina light ke bhi chhoti si leak	seedha peeche ek dheemi drip
$V$	cell ke across terminal voltage	cell ke outputs par pressure
$n$	ideality factor ( $1$ – $2$ ), diode kitna "non-ideal" hai	exponential par ek fudge dial
$V_{T}$	thermal voltage $= k_{B} T / q \approx 26 mV$	heat charges ko kitni zyada hilati hai
$R_{s h}$	shunt resistance — unwanted leakage path	ek chhoti si daraar jo current ko load bypass karne deti hai

Equation ko ek kahaani ki tarah padhna: Sunlight $I_{L}$ bahar pump karti hai (positive), diode exponentially on hone par kuch wapis peeta hai (middle term), aur ek leaky daraar $R_{s h}$ thoda aur chura leti hai (aakhri term). Jo bachta hai woh $I$ hai.

Woh rate jis par charge kisi point se flow karta hai, amperes mein measure hoti hai (coulombs per second).

Master power relation likho.

P = V \cdot I

(watts = volts × amps).

Power se energy kaise nikalte hain?

Power ko time se multiply karo:

E = P \cdot t

(jaise watts × hours = watt-hours).

28 V aur 20 Ah ko stored energy mein convert karo.

28 \times 20 = 560

Wh.

ln (x)

kis sawaal ka jawaab deta hai?

"e ko kis power par raise karein taaki

x

mile?" — yeh ek exponential ko undo karta hai.

Voltage ke saath diode ki current exponentially kyun badhti hai?

Junction cross karne ke liye kaafi thermal energy wale charges ka fraction Boltzmann factor

e^{V / n V_{T}}

follow karta hai.

Thermal voltage

V_{T}

kya hai aur room temperature par uski value kya hai?

V_{T} = k_{B} T / q \approx 26

mV at 300 K.

Cell equation mein

I_{L}

kya represent karta hai?

Photocurrent — absorbed sunlight se free hone wali charge, brightness ke proportional.

Maximum power point dhundne ke liye

d P / d V = 0

kyun set karte hain?

Power hill ke upar slope zero hota hai, isliye zero slope peak locate karta hai.

80% DoD physically kya matlab hai?

Battery ki total charge capacity ka 80% discharge ho chuka hai.

Foundations — Power systems — solar arrays (I-V curve, power tracking), batteries (DoD, cycles), RTG

Part 1 — Char quantities jo flow karti hain

Part 2 — Energy vs. power, aur "-hour" units

Part 3 — Percentages, ratios, aur logarithms

Part 4 — Solar-cell equation ke andar ke symbols

Part 5 — Derivative kyun aata hai

Prerequisite map

Equipment checklist