Solar water pumping, sized and simulated
In a solar pumping project the load is water: a daily volume to deliver from the sun, buffered in a tank. pvSpline sizes the array, the pump and the tank from that need, then simulates the whole chain, from the sun to the water delivered.
Three hydraulic circuits
| Circuit | What it uses |
|---|---|
| Deep borehole | The static head, the specific drawdown per m³/h pumped and the maximum pumping depth. |
| Lake / river | The geometric static head and the friction coefficient. |
| Pressurisation | The setpoint pressure of the network it feeds, in place of a lift height. |
The pump and how the array drives it
- The pump: centrifugal for low head and high flow, positive displacement for high head, described by its nominal power, maximum flow, maximum head, wire-to-water efficiency and the power below which the motor does not turn. Load it from the catalogue, where pumps come in from .PMP files.
- The coupling: an MPPT converter tracking the array’s maximum power point, an AC inverter driving a variable-speed pump, or direct coupling, the array wired straight to the motor, which captures about half the performance.
- A battery buffer, if you want one, keeps the pump running through a cloud or at dawn.
The water need and the tank
The demand is a daily volume of water, month by month: type one daily figure and fill the twelve months, then edit them for a seasonal profile. The tank’s capacity and initial level set the buffer that carries the water from the sunny hours to the hours of need.
What the simulation reports
- Water: pumped, needed, delivered and missing, in m³, and the loss of load by volume.
- Efficiency: the specific energy in kWh per m³, the pump and system efficiencies, and the tank autonomy in days.
- Energy: the array energy at the maximum power point, the hydraulic energy, and the energy left unused while the tank was full or the pump at its limit.
Heatmaps show the tank, the flow and the missing water hour by hour across the year, and the report prints the totals on a page of their own.
A first size in a minute
The pre-sizing page needs neither a weather download nor an open project. Enter the total head, the daily water need, the efficiencies and the days of need the tank should cover, and it suggests the PV power, the pump and the tank volume, sized on the worst month. Apply (pump + tank) writes the pump and the tank into the project.
A pumping study in five steps
- On the Project tab, set System type on the SIMULATION card to Off-grid solar pumping.
- In the Solar pumping block of the Systems card, choose the hydraulic circuit and enter its heads.
- Choose the pump from the catalogue, or type its curve, then pick the coupling.
- Enter the tank and the monthly water need.
- Run the simulation and read the water delivered and the missing water.
Questions
Is there a financial model for pumping?
No. With no grid, a pumping run books no cash flow, so it reports no NPV or payback. The carbon balance still runs.
Can I size a system before the site survey?
Yes. The pre-sizing page runs on built-in monthly climate data for the coordinates, or on your own twelve monthly irradiation values, and gives a starting point to refine in the full simulation.
Does it model a borehole’s drawdown?
Yes. In the deep-borehole circuit, the water level drops with the flow, by the specific drawdown you set, down to the maximum pumping depth.
The fastest way to judge a simulation tool is to run it on a project you already know.