 > Definition Of Solar Terms

### A basic knowledge of the definition of solar terms can go a long way.

Ah: amp hour

Amps: a unit of electrical current or volume

Dynamic Head: the “net” head under actual working conditions. This # is always less than static head and is a result of friction losses in the penstock.

Flow: the quantity of water flowing through the nozzles in the hydro. Leaks don’t count. Most residential sized systems are measured in gallons per minute (GPM). Larger systems are measured in CFS (cubic feet per second). 450 GPM. = I CFS

Head: the vertical component or elevation change between the intake and the hydro-generator measured in feet or pounds per square inch (PSI) of pressure at the nozzle in the hydro. For those of you on the metric system, you will have to make your own conversions. 1 PSI = 2.31 feet of head. 1 foot of head = .433 PSI

kW: kilowatt, one thousand watts

kWh & Ah: By convention: amps, volts, and watts are instantaneous measurements of electrical energy. Over time, we commonly use: watt hours, kilowatt hours, and amp hours. One kilowatt-hour (kWh) equals the amount of electricity needed to burn a 100 watt light bulb for 10 hours. Amp hours is easier to understand and keep track of. For example, if your hydro is producing 5 amps for 24 hours, you have added (5 X 24) amp hours into your systems batteries which can be used or stored for later.

MPPT: maximum power point tracking

Ohms: a unit of electrical impedance. Ohms law states that 12 volts through 4 ohms impedance will allow 3 amps of current to flow. It is necessary to understand voltage drop in a run of wire and Ohms law is fundamental.

Penstock: a pipe or conduit used to carry water to a water wheel or turbine

PV: photovoltaic

Photovoltaic Module: solar panel

RE Source: renewable energy source

Solar Array: a group of solar panels

Volts: a unit of electrical force, Volts = Amps x Ohms

Watts: a unit of power and is a product of amps x volts, for example: 4 amps at 12 volts = 48 watts.

Power (watts) = Amps x Volts