Part of a series in renewal energy technologies brought by M/s Paavi Solar
Friends, let
we continue our topic of types of Solar PV Systems. Yesterday, we have learned about
Off-Grid Solar PV System. The main objective of the Off-Grid Solar PV was energy
security where either Grid connectivity was not available or where one does not
want to use Grid Electricity.
Today, we
want to talk about a system where Grid Connectivity is available but the objective
of the system is to save on energy bills.
First
of all, we will see how the On-Grid Solar PV system work and its objectives. As
stated earlier the main aim of On-Grid Solar PV Systems is to provide electricity
to our units and save on the electricity bills. In this system, some (or total) the load is fed by Solar PV Panels when the solar radiation is available. Otherwise
during off solar hours ie during the night or during cloudy/rainy days, the load is run
by connected Grid supply. This system does not have any storage (Battery Bank) and
hence the system is very cheap as the cost of the battery bank is minimized.
One of the main advantages of this system is that one can design the system to
partially or wholly supply the loads either from Solar Panels or through Grid
or a combination of Solar and Grid together.
Main
working Principles of On-Grid Solar PV System.
Solar
Photovoltaic panels installed on the rooftop (either on G.I. Structures or
directly placed on slanting roofs) in arrays of 12V/24V or 48V gather sunlight
during the daytime and converts sunlight into D.C. These arrays are connected to D.C. Distribution Boards.
These Distribution boards act as Collector and also contains fuses and Surge Protection Devices (SPDs) along
with circuit breakers. The generated D.C. is fed to Solar Inverters containing MMPT or PWM charge
controllers and converts incoming D.C. into usable A.C. (single-phase 240V or
three Phase 440 V). This A.C. runs loads of the household. After fully
meeting the consumption of the household in the day time, if any A.C. is left
unused, this idle A.C. energy is fed to the grid through bi-directional Net
Meter installed by DISCOMs. Simultaneously if the Power received from Solar Panels
in the day time is not sufficient to meet the full load of the household then
balance power is received from the Grid. Bi-directional Net Meter installed by
DISCOMs calculate the Net Energy consumed or fed(sold) to Grid and accordingly
adjusts the future bills. Hence this system is installed for lowering the
energy bill.
There
is no battery backup in the system and hence during the night time or off-solar
hours due to clouds/rain of shades, the entire load is met with Grid and metered accordingly.
This system is cheapest but has certain limitations which are given hereunder.
1. Due
to the absence of Battery Bank (storage) off solar hour loads are fully met with
Grid.
2. Suppose
Grid supply is not available and technicians are maintaining the Grid then Solar
Supply is also cut off to safeguard the lives of technicians.
Main
components of this system are given in the flow diagram given here. These days Hybrid Solar Inverters are also
called as Solar Power Conditioning Unit which
can be programmed to supply load either on Solar or on Grid or a combination of
both.
DISCOMs
provide Net Meter under the policy of Grid-Connected Solar Roof Top System. Different
states have different policies and subsidy guidelines but states follow the
directive regulations of MNRE. As this system is connected to the Grid and
hence proper installation testing is done by DISCOMs to ensure synchronization
and balancing of the systems ie feeding the Grid with stable A.C. energy at
proper voltage and frequency.
Friends
as stated earlier, individual components of the systems will be discussed in detail
in coming blogs. -G
P BOSE
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