By Serm Murmson Updated Mar 24, 2022
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Electric motors drive everything from wristwatches to water pumps. Solar panels can supply the energy needed, but the solar system’s capacity must match the motor’s power requirements.
The electrical output of a solar cell depends on how many cells you use and how you connect them. A single cell typically produces 0.5–0.6 V. Connecting cells in series adds voltage, while parallel connections increase current. By arranging cells in a series‑parallel matrix you can tailor the voltage and current to the motor’s needs.
Solar arrays generate power only when sunlight hits them, so a direct connection to a motor would leave the device idle after sunset. A battery between the panels and the motor stores excess energy, delivering a steady supply even when the sun is out or when the motor demands a high start‑up surge. Weather, latitude, and seasonal changes affect panel output, so a battery also buffers these fluctuations, ensuring reliable motor performance.
Electrical power is the product of voltage and current, measured in watts. A standard U.S. outlet delivers 120 V at 15 A, yielding 1,800 W. Motors translate electrical power into mechanical power (torque × angular velocity). Motor power ratings vary widely: a ceiling‑fan motor may need only 65 W, whereas a dishwasher motor typically requires at least 1,200 W.
Motor nameplates usually list only output power. To determine the input power you must account for efficiency, the ratio of useful output to total input. For example, a 100‑W motor operating at 75 % efficiency draws 75 W of input. Most electric motors run at a minimum of 50 % efficiency, so a motor that can’t receive the required input power will run poorly or fail to start. Since solar panels and batteries supply direct current, an inverter is required if the motor needs alternating current.
