00Engineering case study
This is a real PKE Solution Configurator study for an Open Access consumer on Maharashtra’s new MERC “downhill” banking regime, with the client’s identity removed. Eleven months of 15-minute settlement data went in; a technology-neutral engineering requirement, a bill of quantities and a fifteen-year model came out. The charts below are the study’s own figures.
| HEADLINE | OPEN ACCESS · MSEDCL |
|---|---|
| Recommended system | 5.0 MWh / 2.5 MW |
| Annual energy cycled | 1.06 GWh |
| Year-one net benefit | ₹1.12 Cr |
| Investment (project capex) | ₹8.17 Cr |
| Cash positive by | 5.3 years |
The consumer is a captive-solar Open Access connection on MSEDCL HT-I A at 33 kV, contracted at 1,650 kVA against a 2,200 kVA solar OA allocation. Under Maharashtra’s new MERC downhill banking regime, solar exported at midday no longer redeems uphill at night — it’s stranded the same day it’s generated, or lost. That stranded surplus is the raw material a battery turns into evening value.
SOLAR
Zone-C solar generated on-site annually.
STRANDED
Can’t redeem uphill under the new rule — a battery’s opportunity.
DISPLACEABLE
Evening, night and morning grid import storage can offset.
CONTRACT
Against a 2,200 kVA solar Open Access allocation.
Under the new banking rule, energy stored in the solar window and released at the evening peak earns the full peak avoided cost — nothing is given up, because that surplus would otherwise be curtailed. The three tariff zones below set the reward for getting the timing right.
CSolar / charging
09–17h. Foregone value is zero — this energy would otherwise be curtailed.
A/BNight & morning
00–09h. Normal tariff.
DEvening peak
17–24h. +25% ToD loading. The discharge window.
The system is sized on the P60 design day under the Balanced objective, taking the daily minimum of stranded surplus and displaceable draw across eleven measured months. This is a technology-neutral requirement, established before a single catalogue was opened.
| Required nameplate capacity | 4.8 MWh |
| Required PCS rating | 1,363 kW |
| Annual stranded surplus | 1.46 GWh |
| Annual displaceable draw (evening + night + morning) | 4.33 GWh |
| Annual energy discharged | 1.06 GWh · 0.71 cycles/day |
| Usable depth / round-trip efficiency | 81.9% · 88% |
Charging is scheduled into the solar window, 09:00 to 17:00, where spare capacity below the 1,650 kVA contract demand is available against the 2,200 kVA solar allocation. Discharge lands in the evening peak, with no grid-charging assumed.
The same measured data was run against four sizing objectives — Minimum Investment, Balanced, Maximum Savings and Max Renewable Utilisation — so the consumer can pick the trade-off between investment and return. The recommendation runs the Balanced objective.
| Value stack, year one | |
| Annual captured energy | 1.06 GWh |
| Weighted avoided cost | ₹12.39/kWh |
| Gross energy saving | ₹1.25 Cr/yr |
| Less: O&M (1.5% of capex) | (₹0.12 Cr/yr) |
| Net | |
| Year-one net benefit | ₹1.12 Cr/yr |
Accelerated depreciation — 40% WDV plus a one-time 20% year-one allowance for renewable-classified assets — adds a further ₹1.23 Cr of tax shield in year one alone. That benefit is genuine, but it depends on the buyer’s own tax position and depreciation schedule, so it’s kept separate from the operating value above rather than folded in.
The 5.3-year figure below is the year cumulative cash flow actually turns positive. Capex divided by year-one benefit alone would read a misleadingly short 3.5 years, because year one carries a one-time depreciation credit that doesn’t repeat in later years.
| Component | Configuration |
|---|---|
| Battery | Vault 5000 · 5.0 MWh |
| Power conversion | 2.50 MW PCS |
| Transformer | 3,150 kVA ONAN |
| Enclosure | Containerised |
| Thermal | Liquid cooling |
| Fire suppression | Aerosol suppression |
| MV switchgear | MV RMU |
| EMS / controls | Pai Kane EMS |
SCALE
At 5.0 MWh this is right-sized to the site’s own stranded surplus, not the biggest battery available. Doubling to 2 × Vault 5000 lifts capture from 82% to 98% of the surplus but nearly doubles capex, cutting the 15-year IRR from 17.2% to 8.5% — returns fall fast once the physical surplus is mostly captured. The same method sizes a Core Mini for a rooftop or a Spike for a crane; only the numbers change.
NEXT
A study like this precedes every deployment: confirm contract demand and banking terms, site survey and single-line, firm quotation, then interconnection approvals.
Send yours. The study comes back with charts like these, drawn from your site.
