Running power per line
20 kWDiffers
PV arch, 200.0 kWp4 lines × 20 kWOutage 14:00 to 18:00Usable reserveIllustrative day, single synthetic day
PV arch, 200.0 kWp4 lines × 20 kWOutage 14:00 to 18:00Usable reserveIllustrative day, single synthetic day
- Solar
- kW
- Load
- kW
- Reserve
- %
- Grid
GFT instruments / Energy continuity
Keep the line running.
Size against the clock.
Illustrative default: 200 kWp of solar and 444.4 kWh of battery for an 80 kW production load. Put the outage on the day curve to test what that equipment can serve.
Operate the instrumentProcedural visualisation. Schematic, not a facility.
01 / An instrument for the decision
How much solar and storage keeps the line running through outages?
Drag the outage across the day, or use the presets and sliders. Every curve, figure and read-out below answers as you move. Every starting input is an assumption, not a GFT programme measurement or a supplier quotation.
Illustrative / single day4 lines × 20 kW = 80.0 kWUsable reserve, % of windowA = illustrative default
Outage 14:00 to 18:00
Energy-match solar
kWp
=No change vs A (200.0)
Nominal battery
kWh
=No change vs A (444.4)
Unserved production
kWh/day
=No change vs A (0.0)
Illustrative equipment budget
USD, illustrative
=No change vs A (301,111)
- Solar serves the line
- Battery serves the line
- Grid serves the line
- Unserved
- Outage window, draggable
- Usable reserve
- Scenario A
15:00 to 15:15 · Grid unavailable · Battery serving load
- Load
- kW
- PV
- kW
- Battery to load
- kW
- Reserve at interval end
- %
Read the condition
The model serves the selected outage with the chosen solar curve and a full initial battery. This is a single-day energy result, not a guarantee of uninterrupted production. The battery finishes below its starting reserve, so repeating this day requires additional charging or a revised schedule.
Power is the interval average. Reserve is measured at the interval end as a share of the usable window, not absolute cell state of charge. The sun arc is schematic.
02 / The calculation is open
Energy balance comes before a continuity claim.
Four steps take your sliders to the verdict. The pinned drawing redraws on each step from your live inputs. The shift may cross midnight, and the outage follows the same local clock. An outage outside production does not test live-line backup.
1 / Load: what must stay on kW kWh/day
2 / Solar: match the energy, then test timing kWp kWh/kWp/day
3 / Battery: keep a usable energy window kWh nominal
4 / Dispatch: account for every flow kWh served kWh unserved
Add lighting, ventilation, compressed air, controls and other essential services to your measured boundary before sizing equipment.
The arch is a modelling assumption, not an observed sunrise, cloud pattern or season for Cameroon.
Charging efficiency is a separate assumption; ηc × ηd is the round trip in this simplified model.
PV 800.0 + grid 17.3 + battery 123.7 = served 800.0 + charge 0.0 + curtailed 141.1 kWh
- Running load
- kW
- Daily production energy
- kWh
- Grid energy still needed
- kWh/day
- Day-end usable reserve
- kWh
- Curtailed solar
- kWh/day
- Battery power allowance
- kW
Grid charging and tariff arbitrage are excluded so that dependence on the initial reserve stays visible.
P = line kW × lines · E = P × shift hours20 × 4 = 80.0 kW · 80.0 × 10 = 800.0 kWh
PV kWp = E ÷ Y × sizing % ÷ 100800.0 ÷ 4.0 × 100% = 200.0 kWp
B = P × autonomy ÷ u ÷ ηd80 × 4 ÷ 0.80 ÷ 0.90 = 444.4 kWh
PV + grid + discharge = served + charge + curtailment · Load = served + unserved800.0 + 17.3 + 123.7 = 800.0 + 0.0 + 141.1 kWh
- Step 01 of 04
Define what must stay on.
Start with the simultaneous running demand, not the sum of machine nameplates. Each selected line is a constant load while production is scheduled. The worked example is 20 kW per line across 4 lines: 80 kW, and 800 kWh over a 10-hour shift.
P = line kW × lines · E = P × shift hours20 × 4 = 80.0 kW · 80.0 × 10 = 800.0 kWh - Step 02 of 04
Match energy, then test timing.
At the illustrative net yield of 4 kWh per kWp per day and 100% sizing, the example needs 200 kWp. Yield means final AC energy after PV system losses: do not enter raw irradiance or deduct the same losses twice. The solar shape is a synthetic half-sine from 06:00 to 18:00, normalised to that energy.
PV kWp = E ÷ Y × sizing % ÷ 100800.0 ÷ 4.0 × 100% = 200.0 kWp - Step 03 of 04
Keep a usable energy window.
Four hours at 80 kW require 320 kWh delivered to the load. With an illustrative usable fraction of 0.80 and discharge efficiency of 0.90, nominal capacity is 444.4 kWh and the usable internal window is 355.6 kWh.
B = P × autonomy ÷ u ÷ ηd80 × 4 ÷ 0.80 ÷ 0.90 = 444.4 kWh - Step 04 of 04
Account for every flow.
PV serves production first. Surplus charges the battery up to the usable ceiling and the power allowance; the rest is curtailed, with no export credit. The battery supplies a deficit only while the grid is unavailable.
PV + grid + discharge = served + charge + curtailment · Load = served + unserved800.0 + 17.3 + 123.7 = 800.0 + 0.0 + 141.1 kWh
03 / Assumptions are part of the result
Every starting number is illustrative.
No electrical load, outage record, solar yield or equipment price is established by the programme evidence for this tool, so no preset is labelled as GFT programme defaults. Each value below is a demonstration to replace with site measurements and supplier data. The control limits are screening boundaries, not equipment ratings.
What must stay on: the running load per line, the lines running together, and the shift window they run in.
When the grid is unavailable: the start and length of the single daily outage that is tested against the shift.
What the sun supplies: the net yield and the sizing rule that matches array energy to the day.
What the battery can give: autonomy without sun, the usable share, and one-way efficiencies.
What it costs, as arithmetic: two unit prices and a fixed allowance. Never a quotation.
Lines running together
4 linesDiffers
Production starts
8 hourDiffers
Daily production duration
10 h/dayDiffers
Outage starts
14 hourDiffers
Outage duration
4 hoursDiffers
Net daily solar yield
4 kWh/kWp/dayDiffers
PV versus daily energy match
100 %Differs
Battery autonomy without sun
4 hoursDiffers
Usable share of nameplate
80 %Differs
AC to stored-energy efficiency
95 %Differs
Stored energy to AC efficiency
90 %Differs
Installed solar unit price
850 USD/kWpDiffers
Installed battery unit price
250 USD/kWhDiffers
Additional fixed allowance
20000 USDDiffers
The synthetic solar shape runs from 06:00 to 18:00. It is a positive half-sine evaluated at the midpoint of each quarter hour and normalised so that its integrated energy equals installed kWp multiplied by your net daily yield. This fixed daylight window is a modelling assumption. Battery charge and discharge power are each limited to the full running line load; that allowance is not an inverter selection.
kWh/kWp/day, illustrative
A lower yield asks for a larger array. This slider moves the same input as the bench controls.
04 / Keep the source with the input
Bring a site yield into the model.
Source receipt
The European Commission Joint Research Centre's PVGIS user manual ↗ describes a workflow for estimating PV production for a chosen location. Use the site's coordinates, mounting, orientation and losses to obtain a relevant net electrical yield, then test a difficult production season rather than an annual daily average. The manual was opened on 30 October 2026. No local yield for Douala or Garoua was extracted or implied here.
Not validated by the link
The equations and dispatch logic are GFT screening arithmetic, separate from PVGIS's detailed simulation, and not validated by linking to it. Before procurement, export the scenario, record where every substituted input came from, and reconcile it with an interval load record and the supplier's stated usable capacity and efficiency boundary.
05 / Usable against required
The battery has its own ledger.
The day starts with the usable battery window full. Charge and discharge are AC energy totals. A lower reserve at the end means the next day cannot simply start from the same condition without additional energy. For a shift or outage wrapping across midnight, the chart includes its early-day and late-day portions. It remains a single synthetic day, not a sequential multi-day weather simulation.
Usable from the battery, at the startkWh AC
≥Required through the outagekWh AC
Served. The reserve covers the outage.
End reserve = start reserve + charge × ηc − discharge ÷ ηd
355.6 + 0.0 × 0.95 − 123.7 ÷ 0.90 = 218.1 kWh
Required energy is what the battery supplies plus what stays unserved. Usable energy is the full window at the start of the day, after discharge losses.
Energy: the whole window, with usable (sage) against required (ochre), in kWh AC from your live inputs.
Power: the 14:00 edge of the window at twelve times scale. Illustrative drawing. Not a measurement.
Site: shade cut into the arch and a site schematic. Outside this screening boundary. Drawing, not a site survey.
Budget: the day collapsed into its cost bar. Illustrative USD, from your live inputs.
06 / Engineering continues at the site
A served day still needs a protection design.
Energy is only the first question.
The tool answers whether the battery can last through the outage on this synthetic day. A battery with sufficient kWh may still be unable to start or support a machine. Power, protection and the site itself come next.
- Usable
- kWh
- Required
- kWh
Power and protection are outside the model.
The tool assumes compatible island-capable PV and battery controls are available during the outage. It does not model automatic transfer delay, motor starting, reactive power, voltage dips, harmonics, protection coordination, anti-islanding behaviour or black start. The engineer must check continuous and surge kW, kVA, fault duties, cable sizing, earthing and switching arrangements.
The site decides what the model cannot.
Solar shading, roof condition, structural load, temperature, rain, soiling, degradation, battery ageing, cooling, fire protection, space and maintenance are outside this screening boundary. Each one can change the energy or the safety case, and each needs a site assessment.
- Shading
- Roof condition
- Structural load
- Temperature
- Rain
- Soiling
- Degradation
- Battery ageing
- Cooling
- Fire protection
- Space
- Maintenance
The budget is arithmetic, not a quotation.
Solar kWp multiplied by your solar unit price, plus nominal battery kWh multiplied by your battery unit price, plus the fixed allowance. Unit-price scope must be consistent. Financing, replacement, operating costs, taxes, duties and residual value are excluded unless included explicitly in your allowance. This is not a quotation, investment recommendation or bankable engineering study.
- Solar
- 170,000
- Battery
- 111,111
- Fixed allowance
- 20,000
07 / Commission against a measured duty
Commission the power system against a measured duty.
Replace the illustrative line demand with an interval meter record. Define critical machines and shared services, then test the low-solar season and actual outage timing. A daily energy match does not establish power quality, transfer performance or safe island operation.
Replace with your meter record
ServedThe reserve covers this outage on the modelled day.
- Solar
- kWp
- Battery
- kWh
- Unserved
- kWh/day
✓Served
Related instrument
OEE loss instrument ↗
Put downtime on the same shift boundary. Power availability is one constraint on productive time; quality loss and running speed need their own measurements before extra equipment can be justified.
Production window: 10 h from 08:00
wp06Water, Dye and Energy per Unit ↗
Read the web edition
Your day: 800 kWh over 10 h
wp07Factories on a Weak Grid ↗
Read the web edition
Your outage: 14:00 to 18:00, 4 h
wp13Financing the First Line ↗
Read the web edition
Equipment budget: 301,111 USD, illustrative
A full battery is a starting condition, not a free daily supply. The modelled day ends at 61% of the starting reserve. If the day ends below its starting reserve, this operating pattern needs extra charging before it can repeat. Even a balanced day needs a site study, equipment ratings and a protection design before any claim of continuity.
The model stays visible
Daily load = kW per line × simultaneous lines × production hours. Energy-match PV = daily load ÷ net yield. Nominal battery = running load × autonomy ÷ usable fraction ÷ discharge efficiency. Dispatch balances the AC bus in quarter-hour intervals.
A planning aid. Not investment, legal or tax advice. Verify inputs and boundaries before an operational decision. Method source: GFT illustrative screening arithmetic; PVGIS for the solar resource-data workflow ↗