Solar pumping terminology
Solar Water Pumping Glossary
Every term you will meet when sizing a solar pumping system — total dynamic head, suction lift, peak sun hours, MPPT — defined by the company that pioneered solar water pumping in 1983.
Definitions come from Dankoff Solar’s published technical guides — Solar Water Pumping Basics and Terminology and the Guide to Solar Water Pump Sizing— and from the official pump technical data sheets. Each term links to its definition, so you can cite or share it directly.
A
- AC (Alternating Current)
- Electrical energy which reverses its direction at regular intervals, typically 60 Hertz.
- Ampere (Amp)
- The unit in which electric current is measured.
- Array (Solar Array)
- A group of solar electric modules connected together.
B
- Battery Bank
- A group of batteries wired together to store power in a solar electric system. Allows power to be stored at night, on cloudy days, or to use more power than the array can produce at one time.
C
- Cavitation
- Vapor bubbles produced by excessive suction, creating noise and excessive wear in the pump. To avoid it, intake piping is kept generously sized and the pump is mounted as close to the water source as possible.
- Centrifugal Pump
- A pump which utilizes rotating impellers to accelerate water upward.SunCentric — Dankoff's centrifugal pump
- Controller (Pump Controller)
- Converts the power from the solar array in a certain voltage/current configuration to a voltage/current configuration more efficiently utilized by the pump.Pump system design guides
- Current
- The rate of flow of an electric charge, measured in amperes or amps.
- Current Booster
- A function of a controller which converts a given voltage and current output from the array to a more useful configuration for the pump, typically providing more current but nearly equal power.
D
- DC (Direct Current)
- Electrical energy flowing in one direction and of substantially constant value.
- Diaphragm Pump
- A positive displacement pump which utilizes a cam shaft causing piston displacement. A flexible elastomer (diaphragm) acts as a sealing mechanism in the cam and piston assembly.SolaRam — Dankoff's multi-diaphragm pump
- Drawdown
- The distance or depth the standing water level lowers when water is pumped from the well at a given rate.
E
- Elevation
- Vertical distance from the ground to the input level of a tank or other means of storage.
F
- Flow Rate
- Volume of water provided per second, minute, hour or day.
- Friction Loss
- Pressure loss due to the resistance to water flow in a pipe. It depends on the length, diameter and type of piping, the number of fittings, and the rate of flow — the greater the flow, the greater the friction loss.
G
- GPM (Gallons per Minute)
- Acronym for Gallons per Minute, used to measure the rate of water flow.
- Ground Mount
- A fixed array mounting method for solar modules which have multiple connections to earth.
I
- Inverter
- An appliance used to convert independent DC power into AC power.
K
- Kilowatt (kW)
- Unit of measurement reflecting 1,000 Watts.
L
- Line Loss
- Power loss across a length of wire. Copper wire, depending on its size, has a specified resistance per foot; wire is sized to meet a specified line loss, typically 3-5%.
- Linear Current Booster (LCB)
- Another name for the pump controller used in solar-direct systems. It facilitates starting and prevents stalling in low-light conditions; Dankoff pumps such as the SlowPump, SolarForce and SolaRam use one to start and run in varying light.
- LPM (Liters per Minute)
- Acronym for Liters per Minute, used to measure the rate of water flow.
M
- Module (Solar Module)
- Modular solar electric charger; the term is used interchangeably with solar electric panel.
- Mounting Angle
- Angle of the array, as measured from horizontal.
P
- Parallel Wiring
- A system of wiring for solar electric panels or batteries which increases the amperage of a given array. Parallel wiring is “+” to “+” (positive to positive) and “-” to “-” (negative to negative).
- Peak Sun Hours
- The average equivalent hours of full sun energy received per day, also known as solar insolation. It varies with geographic location and season — the arid central-west of the U.S. averages 5-6 peak hours in summer and as low as 3-4 in mid-winter. Daily gallons divided by peak sun hours gives the gallons per hour a solar-direct pump must deliver.Find Your Pump uses your state's peak sun hours
- Photovoltaic (PV)
- Photovoltaic essentially means to convert light into electricity. Often referred to as PV for short, and more commonly as a “solar panel”.
- Pole Mount
- A stationary pole-top solar array mounting method, where the panels are affixed atop a pole, as opposed to a ground mounted array.
- PSI (Pounds per Square Inch)
- A unit of measurement for pressure. To convert pressure to its equivalent head: head in feet = pressure (psi) × 2.31.
- PV-Direct (Solar-Direct)
- A system that runs the pump directly from the solar array, without batteries, using water storage instead. It is the simplest and most durable system for most applications; storage of 3-7 days' water demand is recommended.
S
- Sand Shroud
- An apparatus which “shrouds” the pump (using a collar and a section of large diameter pipe) to ensure input water enters the pump from below, so that sand and sediment are no longer entrained in the input water.
- Series Wiring
- A system of wiring, for solar electric modules or batteries, which increases voltage. Series wiring is “+” to “-” (positive to negative).
- Solar Cell
- The smallest basic solar electric device, which generates electricity when exposed to light. Typical solar modules are comprised of 36-72 solar cells wired in series.
- Solar Electric
- The preferred term used to describe something which uses sunlight to produce electricity.
- Solar Tracker (Tracking Mount)
- A mount structure that keeps the modules at a 90-degree angle to the sun all day long. This provides more power to the pump over a longer period of the day, producing 20 to 40 percent more water daily in the summertime.
- Standing Water Level (Static Water Level)
- The distance from the top of the well to the surface of the water in the well when no water is being pumped.
- Submersible Pump
- A pump installed under water. Submersible pumps are sometimes suitable for either deep or surface water sources; Dankoff surface pumps are not submersible.
- Suction Lift
- For surface pump systems, the distance from the water surface to the pump inlet port. Dankoff surface pumps draw water from up to 20-25 ft (7-8 m) below the pump at sea level; subtract 1 ft for every 1,000 ft of site elevation.Compare suction lift by pump model
- Sun Hours on Tilt (S.H.O.T.)
- The number of sun hours at a given angle from the horizon, on average.
- Surface Pump
- A pump that operates outside the water source. Surface pumps can draw water from 20-25 ft (7-8 m) below ground level, but they can push it far uphill — the Dankoff SlowPump pushes water as high as 450 vertical feet through miles of pipeline.Dankoff solar surface pumps
- System Grounding
- A means of electrically connecting a photovoltaic system to ground.
T
- Tank Pressure
- For pressurized systems, the operating pressure of the storage tank in psi or kPa. If water flows freely into the storage tank, the tank pressure value is zero.
- Total Dynamic Head (TDH)
- A means of expressing the load of a pumping system at a given rate of flow in terms of its equivalent vertical column of water. TDH is the sum of three factors: total vertical lift, friction loss and tank pressure — Total Dynamic Head = Total Vertical Lift + Friction Loss + Tank Pressure.The sizing calculator computes TDH for you
- Total Vertical Lift
- The sum of the static water level, drawdown and elevation. Standing water level and drawdown can typically be measured by the well drilling company or by testing the existing well.
- True Maximum Power Point Tracking (MPPT)
- A feature of the pump controller which ensures the solar array operates at its maximum power point.
V
- Voltage (Volts)
- The amount of electrical pressure, which causes electricity to flow in the power line. If electricity were water, voltage would be the measure of pressure at the faucet.
W
Missing a term? Ask our design team — and when you are ready to put the vocabulary to work, the sizing calculator turns these numbers into a pump recommendation.