There are a number of ways
to harness solar energy to generate electricity. New Solar offers a
number of these solutions (or variations) to our clients, and they are
described in the following sections. We help our clients to select the
best combination of technologies and financial parameters that can
deliver the most value and performance. We optimize the technology mix
to meet our customers' requirements on return-on-investment, power
production, reliability, and schedule. Our staff will be happy to
discuss with you on the various tradeoffs of these technologies.
The sun constantly hits the Earth with 120,000 Tera-Watt (1012 watts)
of energy. More energy from the sun hits the earth in one hour than all
of the energy consumed on our planet in an entire year. To put it
another way, the solar energy received globally is approximately
1,540,000,000,000,000,000 kWh/year (1,540 peta kWh/year). This is
15,000 times more than the worldwide energy consumption today. Let's
see how we can tap into this tremendous source of clean energy.
Solar
Photovoltaic (PV) System
Solar Photovoltaic (PV) is a method of generating electrical power by
converting solar sunlight into direct current electricity using a
semiconductor material that exhibits the photovoltaic effect. This
photovoltaic effect to tap into solar energy was first discovered in
1839 by the physicist Alexandre-Edmond Becquerel. The strange-sounding
term "photovoltaic" originates in the driving force behind this
technology -- the light beam.
Solar cells are the smallest units of a photovoltaic installation and
solar cells convert light into electric current (photoelectric effect).
Individual solar cells are connected together in a solar module (or
solar panel). A solar module is the flat panel-looking unit constructed
from these solar cells. A photovoltaic (PV) solar system is built from
an arrangement of solar modules and strings of solar modules.
Below is a brief description of a typical solar PV system that can be
installed on top of a residential building or commercial building.
- Individual solar cells are
connected inside the solar panel, and strings of solar panels are
connected together on the roof to convert sunlight into direct current
(DC) electricity.
- An electronic component box called
the "Inverter" converts direct current (DC) electricity into
alternating current (AC) electricity.
- This AC electricity is fed from the
inverter to a residential or commercial building, and this AC power is
what we normally used to power electrical equipments, appliances, and
electronic devices.
- The AC electricity from the
inverter is also fed to the utility electric meter. The meter records
the net amount of energy generated through the solar PV system. The
meter is used by your local utility company to figure out how much they
charge you for your electricity use. This meter normally spins forward
to record the amount of electricity you draw from the grid.
- The meter is also connected to the
utility electric grid. When your solar system is creating more
electricity than you are using, your meter will spin backwards and the
excess electricity is sent to the electric grid from your solar system.
This backward spin offsets the amount of charges you have to pay your
utility firm. The meter will "normally" spin forward at night or on
cloudy days when your solar system is generated less power than you are
consuming at that time inside the building.
Solar modules can be installed in large quantity in an open field to
form a large-scale solar power plant, or solar farm. This solar power
plant is similar to a coal-powered or natural gas-powered power plant,
except it is power only by sunlight.
Below is a brief description of a typical solar PV farm that can be
installed in an open field. 
- Individual solar cells are
connected inside the solar panel, and a large number of strings of
solar panels are connected together on the open field to convert
sunlight into direct current (DC) electricity.
- Electronic equipment, called the
"Inverter", converts direct current (DC) electricity into alternating
current (AC) electricity.
- This AC electricity is fed from the
inverter to a power substation where the voltage is raised by a set of
transformers to a level suitable to connect to the nearby power
transmission line. The substation also has equipments to monitor the
overall system performance.
- The transmission line carries the
electricity generated from the solar farm to the power grid where the
electricity can be consumed by the general public.
Solar modules can be made from a few types of technology:
- Crystalline Silicon - and it can
be classified by the silicon technology used as either
- mono-crystalline silicon, or
- poly-crystalline silicon.
- Thin-film Technology - and it can
be classified by the materials used as
- amorphous silicon,
- cadmium telluride, and
- copper indium gallium selenide
("CIGS")
These technologies have different trade-offs. For example, Crystalline
Silicon technology generally requires much less surface area (roof
space or open field space) to install than thin-film technology. This
translates to lower cost in acquiring the open space for the
installation. On the other hand, thin-film Technology can have an
advantage in lower solar module cost in large-scale projects. We will
be happy to discuss these detail tradeoffs with you in person.
|
|
Concentrated
Solar Power System
Legend has it that Archimedes used a "burning glass" to concentrate
sunlight on the invading Roman fleet and repel them from Syracuse.
Although historians continue to doubt the Archimedes story, in 1866,
Auguste Mouchout was successful in using a parabolic trough to produce
steam for the first solar steam engine.
Concentrated solar power (CSP) systems use lenses or mirrors to focus a
large area of sunlight onto a small absorptive area. An absorptive
material translates this solar energy to generate electricity. There
are generally two types of concentrated solar system - concentrated
photovoltaic, and concentrated solar thermal.
Concentrated Photovoltaic (CPV)
In a concentrated photovoltaic system, electrical power is produced
using photovoltaic effects when the concentrated sunlight is directed
onto photovoltaic semiconductor solar cells. Sunlight is concentrated
from 3X to 500X with some optical focusing system. At the receiving
end, though regular crystalline solar cells can be used as a receptor,
in most systems, multi-junction solar cells are favored over regular
crystalline solar cells as they are more efficient to generate
electricity. The efficiency of these solar cells generally rises with
increased sunlight concentration.
Regular crystalline solar cell normally has a single p-n junction in
the semiconductor material. Multi-junction solar cells are a series of
p-n junctions stacked together inside the semiconductor material, and
it is capable of absorbing the sunlight energy over a much wider light
spectrum. One example is the Gallium Arsenide triple junction solar
cell made of three layers of multiple p-n junctions: InGaP / InGaAs /
Ge, as shown below. 
Concentrated Solar Thermal (CST)
In a concentrated solar thermal system, sunlight is concentrated with
an optical focusing system to heat up a transfer fluid. The energy from
the heated transfer fluid is used to power a conventional turbine-based
power generator to generate electricity.
A wide range of concentrated solar thermal technologies exists,
including the parabolic trough, linear reflector, and solar power
tower. Each concentration method is capable of producing high
temperatures and correspondingly high thermodynamic efficiencies. Each
of these systems varies in the way how they focus the sunlight and the
way they track the Sun. These technologies all have different
trade-offs. For example, a system with a higher concentration of
sunlight directly translates to higher temperature and pressure of the
transfer fluid, and generally speaking, this translates to higher
construction cost. We will be happy to discuss these detail tradeoffs
with you in person.
Below is a brief description of a typical parabolic trough concentrated
solar thermal system: 
It is constructed as a long parabolic mirror (usually coated with a
reflective silver or metalized material) with a thermal absorptive tube
running its length at the focal point. Sunlight is reflected by the
mirror and concentrated on the absorptive tube. The mirror trough
assemble is usually aligned on a north-south axis, and rotated to track
the sun as it moves across the sky each day. Accurate tracking of the
sun is important in order to focus the sunlight onto the absorptive
tube throughout the day. A transfer fluid is pumped through the
absorptive tube, and the solar heat gets absorbed by the transfer
fluid. The energy from the transfer fluid is used to power a
conventional turbine-based power generator to generate electricity.
|
