Solar Energy Systems

Grid-Connected Systems

In grid-connected or grid-tied systems, solar energy is used during the day by the system owner. At night, the owner draws on the previously established electricity grid. An additional benefit of the grid-tied system is that the solar system does not need to be sized to meet peak loads—overages can be drawn from the grid. In many cases, surplus energy generated during the day can be exported back to the grid. Grid-connected systems must meet utility requirements. For example, inverters must not emit noise that can interfere with equipment reception. Inverters must also switch off in cases of grid failure. Finally, they must retain acceptable levels of harmonic distortion, such as voltage quality and current output waveforms.

Grid-connected systems can be applied to residential installations.


Stand-Alone Grid-Tied Systems

Stand-alone grid-connected systems are the same as grid-connected systems, except with battery storage added to allow power to be generated even if the electricity grid fails.


Stand-alone grid-tied systems can be applied to residential and business systems that require uninterrupted power.


Off-Grid Systems

Off-grid systems are not connected to the electricity grid. The output of an off-grid system is entirely dependent upon the intensity of the sun. The more intense the sun exposure: the greater the output. The electricity generated is used immediately, so the system must function on direct current and variable power output.


Off-grid systems can be used for water pumps and greenhouse ventilation systems. Specialized solar water pumps are designed for submersible use (in a borehole) or to float on open water.


Stand-Alone Off-Grid Systems

If a certain power output guarantee is required at any time of the day or night, either some kind of storage device is necessary, or the PV system should be combined with another energy supply such as propane or a diesel generator (see hybrid systems, below). Most off-grid systems use batteries to store power during periods of low to no sunlight.


Stand-alone off-grid systems can be applied to remote homes, lighting, TV, radio, and telemetry.


Stand-Alone Off-Grid Hybrid Systems

To meet the largest power requirements in an off-grid location, the PV system can be configured with a small diesel generator. This means that the PV system no longer has to be sized to cope with the worst sunlight conditions available during the year. Use of the diesel generator for back-up power is minimized during the sunniest part of the year to reduce fuel and maintenance costs.


Solar as a Distributed Energy Source

Solar energy carries the most value as a distributed energy source. Distributed energy means energy produced at or close to the point of use. Distributed generation typically ranges from 1 kilowatt to 5 megawatts in capacity. This contrasts with central generation, which is associated with large 500 to 3000 megawatt generating plants that are usually located at a distance from where the energy is consumed. The electricity is then transported through the transmission and distribution infrastructure to the consumer


Distributed generation is well-suited to the use of some renewable energy technologies because they can be located close to the user and can be installed in small increments to match the load requirement of the customer


Solar energy reduces the cost of investment in grid transmission extension, which carries both an economic cost and a time element associated with capital investment and planning approvals. Solar energy can also be introduced in small increments to closely match the load requirements and is a good fit with daily load peaks.It does not need to be guaranteed or predictable, as solar energy systems can pass surplus power back to a grid during the day while drawing on the grid at night.


The source of the information on this page comes from Solar Buzz.

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