Author : Mr. Rajendra Mahanjan.

Designation : Head – Smart Grid Business

Rooftop Solar System

In a rooftop photovoltaic or rooftop PV system electricity is generated by solar panels mounted on any rooftop structure of a residential, commercial, industrial or a government building. Rooftop systems are generally smaller in size as compared to ground-mounted photovoltaic power plants with higher capacities ranging in MW.

In the urban area a large amount of rooftop spaces can be made available for this purpose and can potentially save expensive land use.

Solar PV System

The rooftop solar system comprises of panels, inverters, cables, connectors, mounting systems and control switchgear.

Solar panels refers to solar photovoltaic (PV) modules electrically connected with appropriate mounting structure specifically designed depending on the roof surface. A PV module is an assembly of solar cells encapsulated in a panel.

A solar inverter, or PV inverter, converts the DC output of a photovoltaic (PV) solar panel into a an alternating current (AC) that can either be fed into a utility electrical grid or used by off-grid electrical loads. It is the most critical component in a photovoltaic system.

Rooftop solar in a utility grid

Typically utilities have power generation located at far off distances from the load. This results in power losses, sometimes in excess of 20-30% levels. This can be avoided in case the power generation close to the load, which is made possible by the rooftop PV systems which are often located right next to the load. This method is also referred as micro generation. These types of systems also take care of the deficient power within the distribution area. The grid must be capable of carrying the power generated by such micro-generators, hence the capacity planning.

Capacity planning

Since the solar power depends on availability of sunlight, it poses a challenge to the utilities to plan for the peak demand, which means despite having the distributed micro generation they have to still cater to the peak demand. This potentially can affect the benefit to an extent of sufficiency of the power in a network. There are two ways this issue can be addresses, one by way of storage of power and the second method by making the grid more responsive and flexible by using technology.

Storage

Since the solar system produces intermittent power, energy storage becomes one of the options to provide reliable energy supplies. The energy storage systems capture excess electrical energy during periods of low demand and high generation and store it in other forms. The energy is later converted back to electricity and returned to the grid as needed. However this method is expensive.

Solar Smart Grid

Alternatively the excess electricity generated is fed into the utility grid. This method is called net metering which means a customer is charged for the net of energy imported and exported. In some cases the utility pays for the extra energy over and above the net energy exported by the solar system into the grid. In other cases, the excess of the net energy is fed free of cost to the grid.

The other method is to use dynamic pricing to balance solar power with the use of technology such as smart grid. What this means is when the solar energy is available in abundance, it is offered at cheap rate to consumers so that they can utilize for various tasks like heating, washing etc. or running some process in the industry and on the other hand the prices go up during shortage of power.

With the right dynamic pricing model, demand response and storage, the issue of intermittent renewable energy source can be addressed to certain extent.

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