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Are you thinking of switching from conventional energy to solar power? A rooftop solar PV power plant is not only a money-saver, it can also generate cash by supplying excess power to neighbours or the local power company.
In No Name Key, the Florida community where money-grubbing locals recently stumped up $650,000 to bring Utility power onshore, the economics of solar power has been transformed. The existing solar homes will now be able to wring a hefty income from the Keys Utility company which has laid the cables into the island paid for by those who want to push up property prices.
These rooftop powerplants, solar photovoltaic (PV) modules installed on rooftops, fall into two categories — standalone use and to feed into the grid.

Installation requirements

Some factors to consider before installing solar on your rooftop include the electrical load, current price, roof size, load capacity and the location of the building. The subsidy given by Central and state governments, local utility, and local community regulations and incentives are also key determinants in evaluation.
Rooftop solar arrays are best installed on a large, flat roof where direct sunlight is available without shadows from surrounding structures. If there is shadow on a part of the terrace during the day, PV solar panels will be less efficient in harvesting the sun’s energy for that period of time.
Here is a basic guide to the components of a solar power system and how it generates electricity.
A set of PV panels that transform sunlight (photons) into DC electricity
A racking system that firmly holds the panels to the roof, and exposes the panels to the sun at an advantageous angle
Inverters that transform DC electricity into AC electricity
Wiring that connects everything
A storage battery In the case of a grid-connected power plant, a large battery is less necessary to store and use that power after sunset but you may want it to protect against outages. However you will need to have an extra switch fitted to disconnect yourself from the main supply for the safety of repairers.
A variety of means to tilt the panels toward the sun to generate more electricity Energy meters to record the energy that is supplied to the grid
Junction boxes Earthing kits
Currently, commercially available silicon based solar panels (called PV solar panels) are made from solar cells encased in a special type of toughened glass. Silicon solar modules have been in the field for more than 50 years and perform quite predictably. These are guaranteed for 25 years of field life but the power yield drops about 0.6 per cent per year. One can use monocrystalline (made from a single crystal) or polycrystalline (made from multiple crystals) panels. Monocrystalline panels are a little more efficient but the cost per watt is almost the same.
Copper indium gallium diselenide (CIGS) panels may become the preferred type for commercial rooftop projects in another five years. These have the potential to deliver reasonable efficiencies at a lower cost than traditional crystalline panels. However, the cost per watt may not necessarily go down, only the panel size per watt will drop. Today, solar panels (depending on the brand) are bankable, that is, banks will loan you the capital for their purchase.
The energy generated can be used both for power consumption or be exported to the gridThe energy is then stored in the batteries during the sunshine hours, which can be utilised as and when required. The energy stored into the batteries is then converted to mains compatible energy, using inverters. This energy automatically synchronises with the grid and injects power into it.
Installation by integrators
Solar system installers can anchor the panel structures. This has to be done with care. It is possible to have non-anchored installation systems but these need to be carefully designed to withstand heavy winds. Such systems are designed to connect the solar power system to a roof using weights, rather than fasteners that must be anchored in the roof. Solar installation companies, often called integrators, can complete a small rooftop project within a few weeks. Before signing a contract with an integrator, do consider the following issues.
Roof condition: If you have an old roof that needs significant maintenance or replacement, you may want to complete that task first before installing the solar array.
Space availability: Solar power projects work best on flat roofs without obstructions.
Weight load: Some roofs are not designed to hold much additional weight. Ascertain the acceptable weight you can add to your roof before signing a contract.
Investments involved
Of all the components, the solar module accounts for the biggest cost, which can be 70 per cent of the total project cost. Cost per watt is currently about $2. The investment primarily depends upon the amount of power to be generated, which varies from a kilowatt to multi-megawatt plants. At present, good quality off-grid rooftop solar power plants can be installed at a cost of $5000 per kW..
Economic advantages
Many would not know that the total investment in a small power plant, for example, 100 x 50 kW, will be the same, if not less, than in a large 5 MW plant. Therefore, it is viable to go for small grid-fed or standalone plants. At current electricity prices in Europe and the US, solar power can be a fiscally sound investment that reduces electricity payments immediately, as well as acting as a hedge against local utility price increases.
Today, the cost of generating power using diesel generation (DG) is nearly double the cost of generating power using sunlight. Based on the current prices and assuming that one takes advantage of the 40 per cent depreciation permitted on such investments, in the first year, the cost of power per unit, kWh, from a well maintained solar plant will be lower than Utility power for many users.
Thus, a solar rooftop installation is a good investment option if both tangible and intangible benefits are considered. The government is also encouraging the use of rooftop power plants as a substitute for DG sets that are consuming fossil fuels and polluting the environment.
With a rooftop installation, one can recover the projects¡¯ costs within 5-6 years, while it also has to be noted that a solar power plant has a typical life of 25 years with proper maintenance. Hence, it is a viable investment option.
The return on investment completely depends on the power purchase agreement entered into by the local utility company.
More benefits for companies
Commercial establishments will benefit more from this system as compared to installations at a residential complex. This is because businesses can use the power in the day during peak hours of work, thus saving the money required to set up battery banks. If these battery banks are already installed, they can be used during the night when energy consumption is lower (may be 10 per cent as compared to the day).
Moreover, for small business establishments or small and medium enterprises (SMEs), a rooftop installation for grid connection is far more profitable than installing multi-megawatt plants, for which it is necessary to install six to eight transformers, which are 98 per cent efficient. Thus, while generating costly solar power, 12-16 per cent of energy is lost due to the inefficiency of these transformers. Thus, it is profitable to install smaller power plants where 100 per cent power is generated, which can then be transferred to the local utility.
Change in government policies will ensure rapid growth in the solar power sector via rooftop and other low power solar plants. .
While no special arrangements are required to inject power into the grid, there is a safety aspect that needs to be factored in while transmitting energy. There is always a risk involved as when the grid fails, the solar power system automatically stops injecting power into the grid. This is called islanding, where the inverter isolates itself. This is a standard feature built into solar power inverters making them safe for residential and commercial applications. A standalone feature in the inverter would enable captive consumption of the solar power generated in the event of any grid outage.

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