Solar

Typical continuous mechanical power produced by a human during physical farm work, accounting for rest and reduced efficiency.

Sustained Human Mechanical Power – 0.10 hp

Human power contribution per hectare over the operational season of 1-ha rice/corn land; accounts for less than 10% of total farm power in mixed systems.

Human Farm Power Contribution – 0.15 hp/ha

Power output of a carabao under moderate draft load and typical field walking speed.

Carabao Power Output – 1 hp

Average draft animal power contribution per hectare over the operational season of 1-ha rice/corn land.

Draft Animal Farm Power Contribution – 0.39 hp/ha

Total electromagnetic energy emitted by the sun.

Solar Radiation

Instantaneous power of solar radiation per unit area on a surface; measures intensity at a specific moment.

Solar Irradiance – W/m²

Cumulative solar energy received over a period, usually daily.

Solar Insolation – kWh/m²

Equivalent number of hours per day when irradiance equals 1,000 W/m². In the Philippines, approximately 5 hours/day.

Peak Sun Hours (PSH) – h/day

Time of day most favorable for solar energy collection, typically between 9:00 AM and 3:00 PM.

Solar Window

Instrument that measures global solar irradiance (direct + diffuse) on a horizontal or tilted surface.

Pyranometer – W/m²

Instrument that measures direct normal solar irradiance.

Pyrheliometer – W/m²

Fraction of sunlight converted into electricity.

Module Efficiency (ηPV)

Thin Film/Other Efficiency

10–20%

Polycrystalline Efficiency

15%-20%

Monocrystalline Efficiency

19–23%+

Overall efficiency of the PV system, including PV module, inverter, charge controller, and derating.

System Efficiency (ηsys)

Accounts for losses due to temperature, dust, shading, and wiring. Typical value: 0.75–0.85.

Derating Factor

Particles in the atmosphere that scatter or absorb sunlight, affecting the ratio of direct to diffuse radiation. High turbidity reduces direct radiation while increasing diffuse radiation.

Atmospheric Turbidity

Percentage of battery capacity that has been used. Important for sizing battery storage. Lead-acid: 50%; Li-ion: 80–90%.

Depth of Discharge (DoD)

Percentage of remaining battery energy relative to its total capacity. Helps prevent over-discharge.

State of Charge (SoC)

Regulates battery charging, prevents overcharging and over-discharging, and extends battery life.

Charge Controller

Converts direct current (DC) into alternating current (AC) for AC loads.

Inverter

Average solar radiation received outside Earth's atmosphere on a surface perpendicular to the Sun's rays. Value: 1,367 W/m².

Solar Constant (Gsc)

Sunlight reaching the Earth's surface without scattering.

Direct (Beam) Radiation

Sunlight scattered by air molecules, dust, and clouds before reaching the Earth's surface.

Diffuse Radiation

Total solar radiation received on a horizontal surface; combination of direct and diffuse radiation.

Global Radiation

Time when the Sun is at its highest point in the sky; maximum solar irradiance generally occurs.

Solar Noon

Tilt of the Earth's rotational axis, approximately 23.5°, causing seasonal changes in solar insolation.

Inclination of Earth (Axial Tilt)

Angle of the Sun measured clockwise from true north.

Zenith Angle*

Angle between the Sun's rays and the Earth's equatorial plane.

Declination Angle

Occurs twice a year when day and night are nearly equal and the Sun is directly above the equator. Vernal Equinox – March; Autumnal Equinox – September.

Equinox

Occurs twice a year, producing the longest and shortest days of the year when the Sun reaches maximum or minimum declination. Summer Solstice – June; Winter Solstice – December.

Solstice

Earth's closest distance to the Sun.

Perihelion

Earth's farthest distance from the Sun.

Aphelion

In the Philippines (Northern Hemisphere), solar panels generally face _______ for maximum annual energy capture.

true south

Process by which a photovoltaic cell converts solar radiation directly into electricity.

Photovoltaic Effect

Individual semiconductor device that converts sunlight directly into electrical energy.

Photovoltaic (PV) Cell

A unit consisting of interconnected photovoltaic cells.

Solar Panel (PV Module)

Group of multiple solar panels connected in series and/or parallel to produce the required voltage and current.

Solar Array