Solar Electricity Generation Basics

Solar electricity generation technology is a very viable form of green energy that is being used increasingly by individuals on their homes as well as in large scale solar farms.

Solar Energy Generation Includes:
Solar electricity generation     Solar panels     Monocrystalline vs polycrystalline solar panels    

Solar panels and solar generating systems are now part of the electricity generating landscape.

Not only do many people have solar panels on their roofs where they can capture the sunlight, but there are also very many solar farms that have large expanses of solar panels which can be sued to generate large amounts of energy.

As the technology moves forward, efficiency levels rise, and the costs for installing systems fall, as well as the need for more green electricity, the solar electricity generating systems are only going to increase in number.

Solar generation systems

Solar photovoltaic or PV systems come in a variety of scales and also topologies dependent upon how they need to operate. Whilst there are large scale "solar farms" there are also other ways in which the solar electricity generation systems can be differentiated.

The different types of solar generation system can be split into three main types.

  • Grid-Tied Solar Photovoltaic (PV) Systems:   The most common form of solar electricity generation systems installed on homes in many countries is a form of system called a "Grid Tied" system.

    Grid tied solar electricity generation systems allow the use of the electricity generated by the solar panels, and when additional power is needed this is drawn from the normal electricity power system. In this way, a constant source of power is provided whether day, or night, sun shine or rain, etc.

    Any surplus power from the solar panels is normally fed back into the power grid system, for which the power company will typically pay.

  • Off-Grid Solar Photovoltaic (PV) Systems:   Solar generation can be an option for situations where it is necessary to be completely off-grid. Some people may want to be totally self sufficient in energy, or there may be no power supply to a remote location, etc.

    Solar power can also be used for small home installations, for example, situations like powering a remote shed, etc. It may be cheaper and more convenient to install a solar electricity generation system than run a very long cable, etc.

    The downside of off-grid photovoltaic, PV solar electricity generating systems is that they rely on the sun. For periods when this is not generating much power an alternative generation system such as wind power and a battery back-up is also advisable if constant renewable power is needed.

  • Grid fallback or hybrid solar photovoltaic systems:   An increasing number of people are opting for hybrid solar generating systems. Here the solar panels are used to supply the current needs and any surplus is used to charge batteries. Alternative renewables such as wind power can also be used within the system.

    For times when the sun is sufficient, power will be drawn from the solar panels or other renewable source, next it will be drawn from the battery, and finally from the grid or power system.

    These systems also provide the possibility of exporting power to the power utility company as well.

    These hybrid photovoltaic systems need to protect against the situation where there is a power cut from the utility provider, as can happen. It needs to ensure that it isolates itself from the grid so that it only exports under safe conditions. Normally this protection is built into the system.

As the technology moves forward with solar electricity generating systems, more capabilities become available. For example it is possible to install equipment that maximises the use of the solar power generated, supplying power for the ongoing needs, but diverting excess to high power background applications such as water heating and electric vehicle recharging that may not always be so time critical.

Solar panels

The solar panels are probably the most obvious ingredient for a solar electricity generating system.

The solar panels are based around solar cell or photovoltaic semiconductor diode technology. These diodes have been in use for many years, but with the need for large scale photovoltaic systems, their development has moved on in leaps and bounds in recent years. Critically their efficiency and lifetime have significant improved.

Typical domestic solar panel installation showing solar panels mounted on a roof
Typical domestic solar panel installation

The solar panels that are available these days consist of an array of these diodes contained within an overall panel. There are a few different ways in which this can be achieved, but essentially they are all based around the same fundamental technology.

The panels a have the basic light sensitive areas, but they also provide a protective covering for the solar diodes as well as having a framework in which they are mounted. This framework also enables them to be mounted on a system on a roof or wherever else.

The panels generate DC and typically may provide between 200 and 300 watts each. As a result, systems are typically made up from a number of solar panels so that they can provide the required level of power.

Solar generation inverter

The solar panels provide a direct current output - they are diodes and only output current in one direction or sense.

In order to be able to interface with the mains power grid and also power domestic or other electrical goods, the DC from the solar panels needs to be converted into AC with the same frequency and phase as the incoming mains power line.

The inverters provide a number of capabilities. Primarily they convert the DC from the solar panels into AC for the mains power system.

Dependent upon the type of system that is being planned, there are three types of inverter that are available:

  • Centralised or string inverters:   This is the type of inverter that is used for most solar or photovoltaic electricity generating systems. It is the least expensive and it does a good job overall but where some of the panels fall into shade, its efficiency falls.

  • Power optimisers:   These power optimisers are the next stage on from a basic centralised inverter. They optimise the output of each solar panel, and then drive a string inverter for conversion to AC power.

  • Micro-inverters:   These inverters are attached to each solar panel, and they enable the maximum efficiency to be obtained even when some panels are shaded

In most instances a string or centralised inverter will be the optimum solution, especially if looking to see a return on the investment for a standard domestic installation.

Solar panel rack mounting

The solar panels cannot be mounted directly to roof or wherever they are to be mounted.

Specialised racking, fixing systems are used to enable them to be firmly fixed to the roof or whoever they are to be installed.

The system must be robust to enable the panels to stay firmly in place even when the level of wind rises. The system must also enable them to be fixed easily to wherever it needs to be mounted.

Monitoring and control

Solar electricity generating systems need to have a monitor the level of generation. This gives the user a very good idea of how the system is performing and whether larger, more current heavy devices can be turned on without drawing current from the system etc.

In addition to this, some control systems are available these days that enable the current delivered to some high capacity items like immersion water heaters or electric vehicle charging so that the maximum use is made of the available solar power without exceeding the amount that is generated and drawing from the power grid.

Solar electricity generation has now become relatively commonplace with homes, factories and many other buildings providing the ideal elevated location for small photovoltaic, PV generation systems. Obviously solar farms are also growing in popularity as the solar radiation is seen as an ideal source of renewable energy.

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