Wind Energy Full Guide: July 2011

Solar Energy Generating Systems (SEGS)

is the largest solar energy generating facility in the world. It consists of nine solar power plants in California's Mojave Desert, where insolation is among the best available in the United States. SEGS I–II (44 MW) are located at Daggett, SEGS III–VII (150 MW) are installed at Kramer Junction, and SEGS VIII–IX (160 MW) are placed at Harper Lake. NextEra Energy Resources operates and partially owns the plants located at Kramer Junction and Harper Lake.

Solar Inverters

A solar inverter or PV inverter is a critical component in a solar energy system. It performs the conversion of the variable DC output of the Photovoltaic (PV) modules into a utility frequency AC current that can be fed into the commercial electrical grid or used by a local, off-grid electrical network. An inverter allows use of ordinary mains-operated appliances on a direct current system.Solar inverters have special functions adapted for use with PV arrays, including maximum power point tracking and anti-islanding protection.

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Types Of Solar Inverters

Solar inverters may be classified into three broad types:

Stand-alone inverters, used in isolated systems where the inverter draws its DC energy from batteries charged by photovoltaic arrays. Many stand-alone inverters also incorporate integral battery chargers to replenish the battery from an AC source, when available. Normally these do not interface in any way with the utility grid, and as such, are not required to have anti-islanding protection.

Grid tie inverters, which match phase with a utility-supplied sine wave. Grid-tie inverters are designed to shut down automatically upon loss of utility supply, for safety reasons. They do not provide backup power during utility outages.

Battery backup inverters, are special inverters which are designed to draw energy from a battery, manage the battery charge via an onboard charger, and export excess energy to the utility grid. These inverters are capable of supplying AC energy to selected loads during a utility outage, and are required to have anti-islanding protection.

Mirrors

The parabolic mirrors are shaped like a half-pipe. The sun shines onto the panels made of glass, which are 94% reflective, unlike a typical mirror, which is only 70% reflective. The mirrors automatically track the sun throughout the day. The greatest source of mirror breakage is wind, with 3000 typically replaced each year. Operators can turn the mirrors to protect them during intense wind storms. An automated washing mechanism is used to periodically clean the parabolic reflective panels.

Fresnel reflectors

Wind load is avoided by the low position of the mirrors. Light construction of tracking system due to separation from the receiver.

A linear Fresnel reflector power plant uses a series of long, narrow, shallow-curvature (or even flat) mirrors to focus light onto one or more linear receivers positioned above the mirrors. On top of the receiver a small parabolic mirror can be attached for further focusing the light. These systems aim to offer lower overall costs by sharing a receiver between several mirrors (as compared with trough and dish concepts), while still using the simple line-focus geometry with one axis for tracking. This is similar to the trough design (and different from central towers and dishes with dual-axis). The receiver is stationary and so fluid couplings are not required (as in troughs and dishes). The mirrors also do not need to support the receiver, so they are structurally simpler. When suitable aiming strategies are used (mirrors aimed at different receivers at different times of day), this can allow a denser packing of mirrors on available land area.

solar Chargers

Solar charger employs solar energy to supply electricity to devices or charge batteries. They are generally portable.

Solar chargers can charge lead acid or Ni-Cd battery bank up to 48 V and hundreds of ampere-hours (up to 400 Ah) capacity. For such type of solar chargers, generally intelligent charge controllers are used. A series of solar cell array plates are installed separately on roof top and can be connected to battery bank. Such arrangement can also be used in addition to mains supply chargers for energy saving during day times.

Most portable chargers can obtain energy from the sun only. Portable wind turbines are also sold. Some, including the Kinesis K3, can work either way. Examples of solar chargers in popular use include:

Small portable models designed to charge a range of different mobile phones, cell phones, ipods or other portable audio equipment.
Fold out models designed to sit on the dashboard of an automobile and plug into the cigar lighter, to keep the battery topped up whilst not in use.
Torches, often combined with a secondary means of charging, such as a kinetic charging system.

solar chargers in the market

Solar chargers mainly uses crystaline solar panels to generate energy. Crystaline solar panel offers best energy transfer efficiency of about 15-18%. There are other solar cells like amorphouse and flexible thin films that can be used for much less efficiency. Flexible films, such as power film, are good to use in certain circumstances because of its versatility but for higher cost. Solar chargers are mostly used to charge cell phones, and mobile electronics on the go.

Most of the solar chargers came with a battery in the middle before it's used to charge external electronics. The built-in battery saves the energy generated from solar panel, and use that energy to charge cell phones.There is certain amount of energy lose during two transfers (solar panel to built-in battery; built-in battery to cell phone's battery) between.

Without a battery in the middle, the solar panel could charges external devices directly. However, it does require a stablizer and circuit changes to allow the solar panel to charge a certain device.

Solar chargers can be rollable or flexible and are manufactured using thin film PV technology . Rollable