3. The annual, monthly, daily and hourly records of the amount
of solar radiation received at any given location over the
earth’s surface are essential for the design of solar energy
Therefore, solar radiation measurements are made
continuously at monitoring stations of different countries.
Measurements may include, direct component at normal incidence, diffuse
component at a horizontal surface, global radiation on a horizontal surface,
total radiation on an inclined surface, ground reflected radiation, and
spectral distribution over certain wavelength bands.
Solar Energy Measurement
4. A variety of instruments are used for the measurement of solar
radiation. They are categorized into two groups:
Pyranometers are used to measure the total radiation, incident on
a horizontal surface from the entire sky.
They can also measure the diffuse component if covered by an
appropriate shade band.
Operation of most pyranometers is based on measurement of
temperature difference between black and white elements using
Solar Energy Measurement
5. Low cost, low sensitivity to tilt and temperature,
pyranometers are built with silicon photovoltaic cell.
Pyrheliometers measure the intensity of the direct solar
radiation at normal incidence.
Most used for routine measurements operate on the
thermopile effect so are similar to pyranometers in this
They differ in that mechanically they must follow the sun to
measure the direct sunlight only and avoid the diffuse
In practice, direct solar radiation is measured by attaching the
instrument to an electrically driven equatorial mount for
tracking the sun.
Solar Energy Measurement
6. The diffuse component is avoided by installing a collimator
tube over the sensor with a circular cone angle of about 50.
Apart from the direct solar radiation records, there may be
records of bright sunshine hours and approximate cloud cover
for the location under interest.
Sunshine recorders are devices that measure hours of bright
sunshine, not energy. These devices are sensitive only to the
direct component of solar radiation when it is above some
The Campbell sunshine recorder is the classic recorder widely
used throughout the world.
13. Major system components
Solar PV system includes different components that should be
selected according to your system type, site location and
The major components for solar PV system are solar charge
controller, inverter, battery bank, auxiliary energy sources and
• PV module
converts sunlight into DC electricity
The solar array consists of one or more PV modules which
convert sunlight into electric energy.
The modules are connected in series and/or parallel to provide
the voltage and current levels to meet your needs.
The array is usually mounted on a metal structure and tilted to
face the sun.
• Solar charge controller
regulates the voltage and current coming from the PV panels
going to battery and prevents battery overcharging and prolongs
the battery life.
Although charge controllers can be purchased with many
optional features, their main function is to maintain the batteries
at the proper charge level, and to protect them from
converts DC output of PV panels or wind turbine into a clean AC
current for AC appliances or fed back into grid line.
An inverter is required when you want to power AC devices.
stores energy for supplying to electrical appliances when there is
The battery bank contains one or more deep-cycle batteries,
connected in series and/or parallel depending on the voltage and
current capacity needed.
The batteries store the power produced by the solar array and
discharge it when required.
is electrical appliances that connected to solar PV system such as
lights, radio, TV, computer, refrigerator, etc.
These are the appliances (such as lights or radios), and the
components (such as water pumps and microwave repeaters),
which consume the power generated by your PV array.
• Auxiliary energy sources
is diesel generator or other renewable energy sources.
These components provide the interconnections and standard
safety features required for any electrical power system.
These include: array combiner box, properly sized cabling,
fuses, switches, circuit breakers and meters.
18. What Factors Affect Solar PV System Efficiency
• Temperature. Solar panel efficiency varies with
• Soiling. Material that accumulates on the surface
of PV panels can block light from reaching the
solar cells, thereby reducing the generated power.
• Shading. ...
• Mismatch. ...
• Inverter Efficiency. ...
19. PV System Engineering
PV stand-alone power system with battery
A traveling clinic uses photovoltaic electricity to keep
vaccines refrigerated in the African desert area
The lift-force VAWT does not experience any starting
torque!!! This may be a critical issue for certain
Turbines connected to the electricity grid can use the
electric generator as a starting motor.
In stand-alone configurations, either electricity storage
devices (again using the generator as a starting motor) or
integrated drag-force turbines (as start turbines) can be
applied in order for the VAWT to spin up to a point
where the lift force can take over.
All main power train components (gearbox, generator, brakes
and main bearing) are placed on the ground, allowing for easy
access for maintenance and lower stress on the tower.
Yaw mechanism for facing the wind is not needed – the
turbine accepts wind from any direction.
The blades are easier to manufacture (symmetrical airfoils
without any twist or taper).
All these features result in a simple machine, easily scalable
to large dimensions, at lower costs than a horizontal axis one.
27. Residence Device and Load Calculating
As a first step, the electrical devices available at the residence are itemized
with their power ratings and time of operation during the day to obtain the
average energy demand in Watt-hour per day.
The total average energy consumption is used to determine the equipment
sizes and ratings starting with the solar array and ending with system wiring
and cost estimate as explained below.
The site under investigation is located at 12°19’ N 35°12’ E with an
elevation of 2300 meters above sea level and with a time Zone of
Africa/Addis Ababa UTC/ GMT+03. The Site has an annual solar irradiance
of above 1200 kWh/m2.
29. Sizing and Selecting of the Solar Array
Before sizing the array, the total daily energy in Watt-hours (E), the
average sun hour per day Tmin, and the DC voltage of the system (VDC)
must be determined.
Once these factors are made available we move to the sizing process.
To avoid under sizing, losses must be considered by dividing the total
power demand in Wh/day by the product of efficiencies of all components
in the system to get the required energy Er.
According the power, the selected panel is (Mitsubishi - MF180UD4, 180-
Wp, 24-V, 7.45-A).
The Specification of PV panel stated below
30. Manufacturer: MITSUBISHI ELECTRIC.
Model name: PV-MF180UD4.
Cell type: Poly-crystalline Silicon.
Number of cells: 50 cells.
Maximum power rating STC (Pmax): 180 watts.
Open circuit voltage (Voc): 30.4V.
Short circuit current (Isc): 8.03A
Maximum power voltage (Vmp): 24.2V.
Maximum power current (Imp): 7.45A.
39. Sizing of the Voltage Controller
According to its function it controls the flow of current. A good
voltage regulator must be able to withstand the maximum current
produced by the array as well as the maximum load current.
Sizing of the voltage regulator can be obtained by multiplying the
short circuit current of the modules connected in parallel by a
safety factor Fsafe. The result gives the rated current of the voltage
regulator. According to selected controller (Xantrex C-60, 24-V,
60-A), the rated current of the voltage Controller I and taking the
safety factor is 125% in this design.
41. Sizing and Selecting of The Inverter
When sizing the inverter, the actual power drawn from the
appliances that will run at the same time must be determined as
a first step. The power of devices that may run at the same time
The inverter needed must be able to handle about 2595-W at
220-Vac. So the selected inverter is Latronics inverter, LS3024,
3000-W, 24-Vdc, 220-Vac.