Off-Grid Solar PowerFrequently Asked Questions
Are government incentives available for Off-Grid Solar Power?
Providing the inverter / charger used is on the approved list an off-grid solar power system will qualify for the same government incentives in the form of STCs as grid connected solar power. For more information or contact us today
What does DoD or SoC stand for?
DoD, is short for the Depth of Discharge and is used to describe how deeply the battery is discharged.
If a battery is fully charged, it means the DoD of the battery is 0%, If however the battery has delivered 30% of its energy then the the DoD of the battery is 30%.
SoC, is short for State of Charge and is used to describe how much charge is retained by a battery.
If a battery is fully charged, it means the SoC of the battery is 100%, if however the battery has delivered 30% of its energy then the SoC of the battery is 70%.
Total Storage Capacity
The total storage of the battery can be calculated by multiplying the Ampere rating of the battery (Ah) by the system voltage. A 48V system with 4 x 12v 200Ah batteries would have a total storage capacity of 9600watt or 9.6kWh.
A 24 volt system with the same batteries would only have 4800watts of total storage of 4.8kWh.
Usable Storage Capacity
The usable storage capacity of an off-grid battery bank will depend on the type of battery used. Lead acid such as Gel or AGM usually has a maximum depth of discharge set at 50% therefore the usable storage will be 50% of the total storage.
A 48V system with 4 x 12V 200Ah AGM batteries would have a total storage of 9600watts however the usable storage would only be 4800 watts.
Lithium batteries have a much higher depth of discharge which is usually between 80% – 90% of the total storage
What is the C rating of a battery
All Lead Acid batteries will have a C rating which is generally shown in a table on the datasheet. The C rating is a measure of the rate at which a battery is discharged relative to its maximum capacity.
A C100 rate is the maximum amount of Ah a battery can safely discharge 100 hours. A C20 rate is the maximum amount of Ah a battery can safely discharge in 20 hours.
In an off-grid situation you will normally use the C10 rating of the battery to determine the total and usable storage of a battery. The C10 rating will be lower than the C100 rating for example a battery with a 200Ah C100 rating will have a C10 rating of around 160Ah.
Can my system be damaged by Hail
Yes – although all solar panels are tested against hail they can still sustain damage if the hail stones are large enough. If you think your solar panels have been damaged by hail it is vital that you turn the system off immediately and contact us for advice.
Will my solar power system produce power on overcast or rainy days?
Since the amount of electricity generated depends on light intensity and not irradiation or direct sunlight, your solar power system will work In cloudy and rainy conditions. However the greater the intensity of light, the greater the flow of electricity therefore more electricity is produced on sunny days.
What is the difference between Mono and Poly solar panels
All solar panels are made from silicon and there are 2 main types of silicon used in the construction:
As you can see from the image Mono-crystalline solar panels are mainly black in colour and have diamond shaped sections between the solar cells. Mono-crystalline silicon, as the name suggests, is grown from a single seed of silicon and forms a round, single cell piece of silicon. The edges are then trimmed to make the square solar cells with rounded corners.
Mono-crystalline solar panels were very popular a few years ago but have now mainly be replaced with Poly-crystalline solar panels.
Poly-crystalline solar panels are more blue in colour and there are no diamond shapes between the cells. Poly-crystalline solar is made up of small pieces of silicon which is melted at very high temperatures and slowly cooled to make large, square ingots from which cells are cut. Poly-crystalline is less energy intensive to manufacture and has become the most popular form of solar panel today.
There is no discernible difference between a quality poly and a quality mono solar panel. There are however large differences between good quality and poor quality solar panels.
What is a standard installation
A standard installation for a solar power system is defined as:
- Single story dwelling with a tin or tile pitched roof
- No split arrays i.e. all the solar panels are installed on the same area of roof
- No cathedral or raked ceilings
- Inverter mounted inside garage or other location with 15 metres or meter box or sub-board
Glossary of terms
ENERGY PAYBACK TIME: The time it takes for a solar module to generate the same amount of energy required for its manufacture. A modern photovoltaic module’s energy payback time is typically from 1 to 4 years, depending on the module type and location. REC Solar Panels have an energy payback time of 1 year.
GRID-CONNECTED OR GRID-TIED SYSTEM: Solar power system connected to the electric grid.
GRID PARITY: Grid parity is when solar cells can produce electricity at the same price as the electrical energy you can buy off the grid, (or less) without subsidies or feed-in tariffs.
INVERTER: A unit that converts the electricity from the solar system (DC – Direct Current) to electricity that is compatible with the grid (AC – Alternating Current).
HYBRID SOLAR POWER: A solar power system that is grid-connected and has a battery
kW (KILOWATT): Unit of power equivalent to 1,000 watts.
kWh (KILOWATT HOUR): A Unit of energy equal to that produced or consumed by one kilowatt in one hour.
MONOCRYSTALLINE SILICON: Processed silicon where all the material consists of only one crystal.
MULTICRYSTALLINE SILICON: Processed silicon where the material consists of several small (typically 1–20 mm diameter) crystal grains. Sometimes also called Polycrsystalline.
mW (MEGAWATT): Unit of power equivalent to 1,000 kW.
OFF-GRID SYSTEM: Solar power system not connected to the electric grid. Normally used in areas where grid-connected electricity is unavailable or available only at a high cost.
PHOTOVOLTAICS (photo=light, voltaic=electricity): Solar cells are made of silicon. When a photon (particle of sunlight) strikes a molecule within the solar cell, an electron is knocked free. An electrical field causes this free electron to move to one side of the cell. The accumulated effect of millions of this interaction generates electricity
SOLAR CELL: Semiconductor device that creates electricity when exposed to sunlight. Normally made from silicon wafers.
SOLAR MODULE (SOLAR PANEL): Interconnected solar cells encapsulated and protected behind transparent materials that protect against humidity, air and mechanical damage. Normally solar modules are made with a glass front, a polymer back sheet and aluminium frame. The photovoltaic module, more commonly known as the solar panel or solar module, is then used as a component in a larger photovoltaic system to offer electricity for commercial and residential applications.
Wp (WATT PEAK): Power from solar cells is normally measured in watts when the solar cell is exposed to a standard sunlight irradiation (1,000 W/sqm).