balance of system
TRANSCRIPT
What is BOS ?
Everything in the “gap” between PV modules &
the Grid.
The balance of system or BOS encompasses all
components of a photovoltaic system other than
the photovoltaic panels.
This includes wiring, switches, a mounting
system, one or many solar inverters, a battery
bank and battery charger. For ground-mount
systems, land is sometimes included as part of the
BOS as well.
Power Electronics
• Inverters
• batteries
Mounting Structures
• Racking - Fixed tilt
• Tracking systems
I. Single axis
II. Dual axis
Cables and connectors
Weather measurement
Control the electricity generated by a solar module
Charge regulators are the link between the PV modules
and battery.
Control the amount of charge flowing in and out of a battery
Protect the battery from overcharge or excessive discharge.
High temperatures tend to reduce battery life because they
accelerate corrosion and self-discharge.
The resistance of lead-acid batteries to freezing is reduced
when they are discharged, so batteries should be kept charged
when they are left in low temperature conditions during the
winter.
Single module need charge controller of between 4A – 6A &
larger arrays may need charge controller of 40A or even more
Store electric energy
The simplest means of electricity storage is to use theelectric rechargeable batteries, especially when PVmodules produce the DC current required for chargingthe batteries.
Batteries store the electrical energy generated by themodules during sunny periods, and deliver it wheneverthe modules cannot supply power or cloudy days.
Most of batteries used in PV systems are lead-acidbatteries. In some applications, for example when usedin locations with extreme climate conditions or wherehigh reliability is essential, nickel-cadmium batteries areused.
The following factors should be considered when choosing a
battery for a PV application:
Operating temperature range (e.g.: -15°C to 50°C)
Self discharge rate (% per month)
Cycle life to 80% depth of discharge (DOD)
Capacity (Ah) at 10 hr & 100 hr rates (C10 & C100)
Robustness for transport to site
Resistance to overcharging
Cost
battery efficiency for most PV application is 85%
Inverters
DC to AC Converter
• The inverter's main functions are: transformation of
DC electricity into AC, wave shaping of the output
AC electricity.
• The most important features of an inverter for PV
applications are its reliability and its efficiency
characteristics. They are designed to operate a PV
system continuously near its maximum power
point.
• Inverters have efficiencies ranging from 85% to
95% for most PV application.
Mounting Structures
Main support of module
The structuring that supports the modules
Typically aluminum, galvanised iron
Should be corrosion resistant
Choose depending on soil, wind and weather
conditions!
Overwhelming majority : Fixed tilt
Rare: Single or double-axis trackers
Fixed Tilt
Single Axis
Double Axis
Fixed tilt
Source: Schletter
Type of Tracking systems
A. Manually operated
B. Motor operated
• Single Axis
• Dual axis
Available in both single axis and dual axis modes
Source: Linak
AS
Single axis
Dual axis
Cable and Connectors
The electricity carriers
Energy output directly related to ambient
conditions like
Amount of sunlight(Irradiation)
PV Module temperature
Ambient temperature
Irradiation sensors
Module and ambient temperature meaurement