Understanding Solar Power
"... Solar Power is an exponentially growing investment that outperforms most other investments available today...."
Is solar power the way to go?
Misperceptions of solar power
There is a general misperception amongst people that solar power is the ultimate, cheep, quick fix for becoming totally independent from traditional grid power like your municipality.
A typical misperception is that a few PV panels and "deep-cycle" batteries will be able to sustain i.e. a household. Unfortunately the rules of nature applies - what you put in, is (less) than what you get out.
Understanding the basics
There is a considerable voltage difference between the PV panels (12 - 30VDC) and that of the appliances (230 or 400VAC).
The multiplication factor for i.e. 12V @ 8 Amp to reach 220Volt is mathematically 20 times, which is theoretically the number of PV panels required in series to deliver 8 Amp @ 220Volt.
Although we are generating 220VAC from 12Volt DC power sources, must it be realised that the i.e. 8A @ 12VDC, will only deliver (8 Amp ÷ 20 =) 0.4 Amps @ 220V, barely enough to keep a TV going.
By applying the above maths it does not matter what kind of PV panel or inverter you use, these basics will always apply.
Types of solar Power Systems
Hybrid and Backup Solar Power Systems
Hybrid systems are a combination between an off-grid system with batteries, which can also take additional power inputs like:
If an alternative power source is available during after-hours to supplement the solar power (available only during day-time), the number of batteries and PV panels can be reduced substantially, making such a system much more affordable than an Off-Grid solar system. Due to the battery bank, it will however always be more expensive than a Grid-Tied solution.
Grid-tied solar Power Systems
The Grid-tied system supplements your electricity supply by producing electricity that you draw from the utility grid and is primarily used to save on electricity bills. This system is capable of pushing unused electricity back into the utility supply for later use (i.e. during night time.)
With grid-tied systems it is required by law that it will disconnect from the grid and switch off to prevent power being pushed back into the grid when there is a power failure on the grid-supply. This is to prevent maintenance people working on the grid of being electrocuted. This is called Anti-Islanding.
Off-grid Solar Power Systems
Off-grid systems are mostly used where electricity is crucial where there it is no other source of electricity supply available. It is an expensive method of producing power for "around the clock" use, for the following reasons:
Village Solar Systems
To meet the growing demand for larger and more complex rural electrification systems, Electrilabs offers a new concept for micro-grids.
This concept brings a very robust solution, which is simple to implement while providing flexibility in both its design and management. A standard hybrid unit is at the core of the system and decentralized units can provide redundancy, storage service, power assistance, and interface with other renewable sources to the micro-grid.
This concept offers the following advantages :
Sharing solar power in a village
Anti-Islanding of grid-tied and/or Hybrid Solar Power Systems
Please note that legislation dictates that any system that is grid-tied and still capable of generating power when the grid power has failed, MUST present power from being pushed back into the grid while the grid has failed.
Many countries (including South Africa) have adapted the international standard DIN VDE 0126-1-1 in terms of the isolation of embedded power plants (grid-tied power generation systems) to prevent the islanding effect.
Solar Battery Systems
A typical battery bank required for a mid-sized solar system of ± 10KW
Fundamentals - Solar radiation
One of the basic processes behind the photovoltaic effect, on which the operation of solar cells is based, is generation of the electron-hole pairs due to absorption of visible or other electromagnetic radiation by a semiconductor material.
Solar Power yield
Sunny day Rainy day
Selecting an inverter
Selecting the PV generator and solar charge controller
Selecting the system voltage
Cable lengths and cross sections
How important is the Efficiency of an Inverter?
Killer loads for (off-grid) solar systems
There are three types of solar fridges: ones that use batteries and solar panels, ones that use just solar panels, and ones that use neither batteries nor panels and are constructed from household materials. 1. A solar fridge that uses batteries actually uses a combination of solar panels and lead batteries - the batteries serve as back up overnight and on sunless days. While it can be effective, this type of solar fridge has many disadvantages. For instance, it is expensive to buy and the batteries are heavy and deteriorate quickly in hot climates. It is maintenance intensive and only lasts about three years. The batteries also need to be disposed of properly, otherwise they leak and cause lead pollution.
2. Solar-powered refrigerators that generate electricity with the help of solar panels, then use this electricity like a normal plug-in refrigerator. Although this type of refrigerator is powered by solar energy, it is not 100% eco-friendly as the cooling gases that are used in the refrigerator and the ones generated due to cooling, contribute to global warming and depletion of the ozone layer.
3. Solar-powered fridges that don’t require batteries or solar panels are better suited to developing countries, as they can be made from basic household materials. Although these fridges are technically solar powered, they rely on conduction, convection and evaporation to operate at an even 6°C. These refrigerators work according to atmospheric temperatures - the drop and rise in the heat of the sun directly affects the rate of cooling. The greater the heat of the sun, the lower the temperature will be in the inner cylinder. Many scientists predict that solar-powered refrigerators will totally replace all electricity powered refrigerators as the most energy-efficient refrigerators.