Step 1 · Demand & duty cycleThe same energy requirement feeds both powertrains.
Power & energy| Quantity | Value | Formula |
|---|
| Propulsion power at cruise | 10 kW | interp. speed–power curve @ 6 kn |
| Power required at max speed | 25 kW | interp. speed–power curve @ 8 kn |
| Daily range | 100 km | trips/day × trip distance |
| Duty cycle distance | 50 km | sum of segment distances (one recharge) |
| Recharges / day | 2 | daily range / cycle distance = 100/50 |
| Running hours / day | 9 h | duty-cycle run time × recharges/day |
| Idle hours / day | 0 h | 0-kn segments × recharges/day |
| Berthing time | 2 h | input (trips × embark min / 60) |
| Operating hours / day | 11 h | running + berthing = 9 + 2 |
| Propulsion energy (mech) / day | 90 kWh | propPower×runH = 10×9 |
| Propulsion energy (elec) / day | 100 kWh | propMech/ηmotor = 90/0.90 |
| Auxiliary energy / day | 11 kWh | aux×opH = 1×11 |
Step 2 · Power trainMotor and engine are both sized from the power needed at max speed.
Power train — motor & engine| Quantity | Value | Formula |
|---|
| Motor rating (with margin) | 30 kW | reqMax×(1+margin) = 25×(1+0.20) |
| Power train system (electric) | Inboard-15kW-48V system · 15 kW × 2 sets | auto-pick smallest system ≥ motor rating |
| Power train cost (electric) | ₹24.0 L | system price × 2 set(s) |
| Powering penalty vs electric | +60 % | traditional / efficient input |
| Diesel engine (interpolated) | 25 kW/set × 2 sets | reqMax×(1+penalty)×(1+engine margin)/sets = 25×(1+0.60)×(1+0.25)/2 |
| Diesel engine cost | ₹32.0 L | interp. diesel ₹/kW curve × sets |
Step 3 · Battery sizingThe pack is sized to one recharge cycle, then rounded up to whole strings and sets.
LFP + solar| Quantity | Value | Formula |
|---|
| Recharge range | 50 km | input |
| Charge leg fraction | 0.5 | recharge range / daily range = 50/100 |
| Solar credit for sizing (prop / aux) | 1.4 / 0.4 kWh | solar×consider% = solar×0.25 |
| Battery energy for sizing (prop / aux) | 98.6 / 10.6 kWh | max(0, demand − solar credit) |
| Grid energy / day (full solar, prop / aux) | 94.4 / 9.6 kWh | max(0, demand − full solar) |
| Battery sized — prop / aux | 74 / 8 kWh | battE×leg/DoD×(1+buf); DoD=0.80, buf=0.20 |
| Module (V / Ah / Wh) | 12.5 V / 105 Ah / 1,313 Wh | Wh = V×Ah = 12.5×105 |
| Battery voltage → series | 48 V → 4S | NMS = ceil(sysV/moduleV) = ceil(48/12.5) |
| Step (one 4S string) | 5.3 kWh | NMS×moduleWh/1000 = 4×1,313/1000 |
| Separate aux battery | No — with propulsion | input |
| Battery sets · min / set | 2 × 42 kWh | ceil((prop+aux req/sets)/step)×step |
| Selected / set → pack | 42 → 84 kWh | sets × chosen pack/set |
| Total pack | 84 kWh | aux load sized within the propulsion pack |
| Pack oversize factor | 1× | total pack / required = 84/82 |
| Cost rate prop (cost / repl) | ₹80,000 / ₹60,000 per kWh | input |
| Cost rate aux (cost / repl) | ₹30,000 / ₹15,000 per kWh | input |
| ESS cost (incl. charging) | ₹66.1 L | prop kWh×₹prop + aux kWh×₹aux + charger |
| Capital | ₹116.3 L | boat + power train + ESS + solar |
| Energy cost / yr | ₹2.7 L | grid kWh×days×CEEB = (gP+gA)×300×₹8.6 |
| Maintenance / yr | ₹0.3 L | energy cost × 10% |
| Annual running (Yr 1) | ₹3.0 L | energy + maintenance ; escalates 3%/yr |
| Charge cycles per year | 600 | days/leg = 300/0.5 |
| Life: cycle vs calendar | 6.7 yr / 7 yr | cycle life/cycles-per-yr ; shelf life |
| Replacement every | 6 yr (cycle-limited) | floor(min(cycle yrs, calendar yrs)) |
| Replacement years | 6, 12, 18 | multiples of interval within period |
| Replacement (each event) | ₹46.7 L | prop kWh×₹replProp + aux kWh×₹replAux |
Step 4 · Energy, fuel & running costSolar offset and energy price, then the diesel fuel burn over the duty cycle.
Solar & energy price| Quantity | Value | Formula |
|---|
| Solar generation / day | 7 kWh | kWp×insolation×ηsys = 2×5.5×0.64 |
| to propulsion / to aux | 5.6 / 1.4 kWh | ×share / ×(1−share), share=0.80 |
| Cost of energy at battery (CEEB) | ₹8.6/kWh | tariff/(ηbatt×ηcharger) = 7/(0.90×0.90) |
Diesel — fuel & running cost| Quantity | Value | Formula |
|---|
| Propulsion energy /day (diesel) | 144 kWh | propMech×(1+penalty) = 90×(1+0.60) |
| SFC bowl (best · load) | 250 g/kWh @ 80% MCR | minimum SFC point |
| SFC rise 25% / 100% MCR | +15% / +3% | parabola through these points |
| Effective SFC (duty avg) | 279 g/kWh | load-weighted over the duty cycle |
| Propulsion fuel / day | 47.2 L | Σ modes: SFC(load)×kWh/(1000×ρ×load-factor) |
| Aux genset SFC | 301 g/kWh | best 300 @ 70% MCR on the bowl |
| Aux mech / fuel per day | 12.2 kWh / 4.3 L | aux/ηalt × aux SFC |
| Annual fuel | 15,457 L | (propFuel+auxFuel)×days ; aux includes idle hours = (47.2+4.3)×300 |
| Fuel price | ₹100/L | input |
| Maintenance (% of fuel) | +10 % | input |
| Capital | ₹57.0 L | boat + power train = ₹25.0 L + ₹32.0 L |
| Fuel cost / yr | ₹15.5 L | fuel×price = 15,457×₹100 |
| Maintenance / yr | ₹1.5 L | fuel cost × 10% |
| Annual running (Yr 1) | ₹17.0 L | fuel + maintenance ; escalates 5%/yr |
Step 5 · Comparison & CAPEX splitAll money in lakh INR.
Diesel v/s Solar electric| Metric | Diesel | Solar electric |
|---|
| Capital | ₹57.0 L | ₹116.3 L |
| Annual running (Yr 1) | ₹17.0 L | ₹3.0 L |
| Battery pack (kWh) | — | 84 |
| Replacement (each) | — | ₹46.7 L |
| Payback (simple) | — | 4.2 yr |
| Breakeven (NPV) | — | 4.6 yr |
| Breakeven (undiscounted) | — | 3.9 yr |
| Residual value (yr 20) | ₹5.7 L | ₹11.6 L |
| 20-yr TCO (undiscounted) | ₹613.5 L | ₹324.9 L |
| 20-yr TCO (NPV) | ₹322.8 L | ₹218.7 L |
CAPEX breakdown| Bucket | Diesel | Solar electric |
|---|
| Boat (ex-system) | ₹25.0 L | ₹25.0 L |
| Power train | ₹32.0 L | ₹24.0 L |
| ESS (battery + charging) | ₹0.0 L | ₹66.1 L |
| Solar plant | ₹0.0 L | ₹1.2 L |
| Total capital | ₹57.0 L | ₹116.3 L |
Step 6 · Energy & emissionsAnnual energy split and CO2; fuel in litres, CO2 in tonnes.
Annual energy (LFP)| Energy from solar / yr | 2,112 kWh (6%) |
| Energy from grid / yr | 31,185 kWh (94%) |
| Total charged energy / yr | 33,297 kWh |
Fuel & CO2| Metric | Diesel | Solar electric |
|---|
| Diesel fuel / yr | 15,457 L | — |
| Diesel fuel lifetime | 3,09,136 L | — |
| CO2 factor | 2.68 kg/L | 0.71 kg/kWh |
| Annual CO2 (yr 1, t) | 41.4 | 22.1 |
| Lifetime CO2 (t) | 828.5 | 445.5 |
| — electric lifetime basis | — | Σ each year (solar degrades 1%/yr) |
| CO2 saved v/s diesel (t) | — | 383 |
Step 7 · 20-year cash flowCumulative cost, discounted (NPV) and nominal; lakh INR.
Cumulative cost — NPV v/s nominal| Year | Diesel NPV | LFP NPV | Diesel nom | LFP nom |
|---|
| Year 0 | ₹57.0 L | ₹116.3 L | ₹57.0 L | ₹116.3 L |
| Year 1 | ₹72.9 L | ₹119.1 L | ₹74.0 L | ₹119.3 L |
| Year 2 | ₹88.5 L | ₹121.7 L | ₹91.9 L | ₹122.3 L |
| Year 3 | ₹103.8 L | ₹124.3 L | ₹110.6 L | ₹125.5 L |
| Year 4 | ₹118.8 L | ₹126.8 L | ₹130.3 L | ₹128.7 L |
| Year 5 | ₹133.5 L | ₹129.2 L | ₹150.9 L | ₹132.1 L |
| Year 6 | ₹148.0 L | ₹162.6 L | ₹172.6 L | ₹182.2 L |
| Year 7 | ₹162.2 L | ₹164.8 L | ₹195.4 L | ₹185.8 L |
| Year 8 | ₹176.1 L | ₹166.9 L | ₹219.4 L | ₹189.4 L |
| Year 9 | ₹189.8 L | ₹169.0 L | ₹244.5 L | ₹193.2 L |
| Year 10 | ₹203.2 L | ₹171.0 L | ₹270.9 L | ₹197.1 L |
| Year 11 | ₹216.3 L | ₹172.9 L | ₹298.6 L | ₹201.1 L |
| Year 12 | ₹229.3 L | ₹195.4 L | ₹327.6 L | ₹251.9 L |
| Year 13 | ₹241.9 L | ₹197.2 L | ₹358.2 L | ₹256.2 L |
| Year 14 | ₹254.4 L | ₹198.9 L | ₹390.2 L | ₹260.6 L |
| Year 15 | ₹266.6 L | ₹200.6 L | ₹423.9 L | ₹265.1 L |
| Year 16 | ₹278.5 L | ₹202.1 L | ₹459.2 L | ₹269.8 L |
| Year 17 | ₹290.3 L | ₹203.7 L | ₹496.4 L | ₹274.6 L |
| Year 18 | ₹301.8 L | ₹218.9 L | ₹535.3 L | ₹326.2 L |
| Year 19 | ₹313.1 L | ₹220.3 L | ₹576.2 L | ₹331.3 L |
| Year 20 | ₹322.8 L | ₹218.7 L | ₹613.5 L | ₹324.9 L |
Step 8 · Profit & lossRevenue & crew are identical for both powertrains, so the NPV gap = the cost gap.
Revenue & crew (annual)| Quantity | Value | Formula |
|---|
| Annual revenue | ₹38.4 L | 20 pax×₹40×80%×20 trips×300 days |
| Crew cost / yr | ₹7.3 L | ₹1,000×2 crew×1 sets×365 |
| Revenue escalation | +5 %/yr | input |
Net present value (PV over 20 yrs)| Present value | Diesel | Solar electric |
|---|
| Revenue | ₹603.5 L | ₹603.5 L |
| CAPEX | −₹57.0 L | −₹116.3 L |
| Energy | −₹242.9 L | −₹36.1 L |
| Maintenance | −₹24.3 L | −₹3.6 L |
| Crew | −₹114.7 L | −₹114.7 L |
| Battery replacement | ₹0.0 L | −₹65.7 L |
| Residual value (+) | ₹1.5 L | ₹3.0 L |
| Net present value | ₹166.0 L | ₹270.1 L |
Step 9 · Sensitivity — break-evenValue at which each key assumption flips the 20-yr NPV decision, others held. Full sweep & tornado in the Sensitivity tab.
At current inputs solar electric is cheaper by ₹104.1 L (20-yr NPV).
Break-even thresholds| Parameter | Current | Break-even |
|---|
| Diesel price | 100 ₹/L | 61 ₹/L — electric cheaper above 61 ₹/L |
| Grid tariff | 7 ₹/kWh | 25.3 ₹/kWh — electric cheaper below 25.3 ₹/kWh |
| Battery prop cost | 80000 ₹/kWh | 220900 ₹/kWh — electric cheaper below 220900 ₹/kWh |
| Discount rate | 7 % | 22.4 % — electric cheaper below 22.4 % |
| Analysis period | 20 yrs | 5 yrs — electric cheaper above 5 yrs |
| Best SFC (engine) | 250 g/kWh | 144 g/kWh — electric cheaper above 144 g/kWh |
Step 01
Pick vessel & duty cycle
Speed-power curve, trip profile, hours, solar size.
Step 02
Propulsion power
Interpolate power at cruise and max speed from the curve.
Step 03
Operating & running hours
From trips/day, distance and embark time.
Step 04
Daily energy demand
Propulsion (mech → elec) and auxiliary energy.
Step 05
Solar generation & credit
Usable solar offsets part of the per-charge demand.
Step 06
Battery sizing
Propulsion pack — and a separate aux (XDLE) bank if chosen — in whole module-strings per set.
Step 07
CAPEX
Boat + power train + ESS + solar plant.
Step 08
OPEX
Diesel fuel cost vs grid energy at battery (CCB).
Step 09
Emissions
Diesel CO2 vs grid CO2 for energy solar doesn't cover.
Step 10
20-year cash flow
Inflate OPEX, add replacements, discount to present.
Step 11
NPV cost & breakeven
Total NPV and the year electric drops below diesel.
Step 12
Compare
Diesel v/s LFP v/s LTO — lowest NPV wins.