Power
Power is the rate at which energy is converted from one form to another. It is measured in watts (W) and kilowatts (kW), with 1 kilowatt = 1,000 watts, Solar Power is always talked about in kilowatts.
Energy
Energy is the ‘volume’ of electricity produced over time and is measured in kilowatts per hour (kWh). Electricity bills are expressed in kWh, with the typical Australian household consuming 18 kilowatt hours (kWh) of electricity per day. Source: Clean Energy Council (CEC).
Alternating Current (AC)
AC is a type of electrical current that moves back and forth at regular intervals. It is the standard ‘on grid’ electricity that powers your home via the wall outlets around your house.
Direct Current (DC)
DC is an electrical current that flows consistently in one direction and is typically used in things like flashlights and other battery powered appliances. DC is what solar panels produce and what solar batteries hold in storage.
Solar Photovoltaic (PV)
A technology that converts sunlight into direct current (DC) electricity by using semiconductors.
Irradiance
Irradiance is a measure of power. Solar irradiance is the amount of solar power that is received by a PV panels at any given moment.
Irradiation
Irradiation is measure of energy. Solar irradiation is the amount of solar energy that is received by a PV panels over a period of time.
Peak Sun Hours (PSH)
Daily solar irradiation. Peak Sun Hours are the number of hours in a day when the sun’s irradiance (power) is at its “peak” intensity of 1kW/m2 The more PSH, the better (in terms of maximising your solar system output).
Tilt Angle
The angle between the horizontal plane and the plane of the panel.
Solar Batteries – Glossary of Terms
While solar panel and battery terminology is similar, there are some small differences that could change the outcome of your system. This glossary will you understand exactly what your battery is doing and how to utilise it best.
Charge
The process of converting electrical energy to chemical energy, so you can power the battery.
Discharge
The process of converting stored chemical energy to electrical energy and therefore using power from the battery.
Depth of Discharge (DOD) %
The percentage of how much of the total capacity has been extracted, inversely related with State of Charge (SOC).
State of Charge (SOC)
The amount of charge percentage that is still in the battery.
Self-Discharge
batteries lose charge even when not used to power anything.
C-Rate
The rate of discharge (or charge) as compared to the capacity of the battery.
Life cycle
The number of charge-discharge cycles battery can provide.
kW = Power Rating
How much power can flow in or out of the battery in any given instant.
kWh = Capacity/Energy Rating
The measure of how much electricity the system can deliver or absorb over the course of an hour.
Understanding the difference between Power and Energy
The terms ‘power’ and ‘energy’ are often used interchangeably. However, the truth is, they mean different things.
Power
Power refers to an instantaneous output at any given moment and is measured in kilowatts (kW), eg, a solar power system may produce 2kW of electrical power at 9 am, but 5kW of power at 12 pm when the sun is shining the brightest.
Energy
Energy is a measure of the ‘volume’ of electricity over time and is measured in kilowatts per hour (kWh). Your solar system will generate a certain number of kWh per day. Similarly, the amount of energy that a solar battery can store is measured in kWh.
Batteries
Batteries are designed to maximise either the power rating or the energy rating of the battery, depending on the intended use of the battery.
For example, if a battery system is going to be primarily used to provide peak-time-shifting or generation/demand balancing, the battery will need to be able to be discharged over a longer period of time. In this instance, it will be designed with a higher energy rating (kWh) and less power to support a long duration.