|
The adoption of Solar
energy for
Distributed Power Generation necessarily requires the
conversion of the energy into forms useable within the
context of the specific legacy Distributed Power Generation System. In this
respect, several Solar Energy Collector types have been analyzed
based on either the capture of the
Optical Energy, or
Thermal
Energy, or the combined
Thermal and Optical Energies.
The specifics about the integration of any one of these
collectors for the purposes of extracting the captured energy
should vary with extraction-design. Of particular significance
however, is the conversion of the heat into a mechanical energy
through driving turbines, particularly in a retrofit application,
given that such application is both critical and essential in
enabling the adoption of Solar Energy as an
alternative energy source to fossil fuels.
Given the object of
implementing retrofit adaption of existing Power Generation
Systems to use Solar Energy, the collector which is most appropriate
would be one that enables availing the Solar Energy in the form
of heat energy. Although virtually, every one of the collectors
can be integrated into a design that enables it provide the
energy as heat energy, the Solar Energy
Thermal Absorber-Tubes Collector permits the most
ready adoption for the purposes of retrofit engineering of
existing Power Generation System into Distributed Solar Power
Generation System.
Summarily
two salient features makes this collector quite suitable,
and drives its choice in this retrofit design analysis:
- Under proper
connection, the fluid should flow into the absorber through
the inlet and out through the outlet, and be available for the
application-specification use and then be fed into the
absorber in continuous circulating flow.
-
The modularity of the design
supports scalability, allowing for the integration
of several collector modules to provide scaled heat supply needs, as
in industries.
However, for the
purposes of an even enhanced performance, certain
modifications or improvements in the adoption of this particular
Solar Collector is possible. The design as presented does not
collect the optical energy component. The absorption and
simultaneous conversion into heat would result in significant
performance enhancement. Accordingly, such modification is
|
is implemented: The
outer surface of the inner tube is coated with a photothermal
substance that absorbs the optical energy while the thermal energy
is absorbed by the energy-absorber liquid, thereby enabling the full
capture of the two components of the Solar Energy. naturally, the
photothermal substance absorbs the optical energy converting same
into heat that is transferred by conduction preferably into the
liquid as well. The transfer is preferably into the liquid because
of the vacuum maintained in the space between the two tubes and the
selection and use of a photothermal substance that is not
significantly increase the base emissivity of the glass.
Operational considerations
also have roles, however. As per the analysis,
the Solar Thermal Energy is extracted by being conducted into or absorbed
by
liquid preferably with high thermal capacitance property.
Besides, this
fluid is generally intended to be recirculated continuously with
the heat extracted from the liquid as part of the circulation
process. As such, from a thermodynamics perspective, the overall
performance would be better if the energy-absorber liquid will be
flowing out of the Absorber Tubes at very high temperature relative
to the boiling point of water. In this regard then using a liquid
that has a significantly higher boiling temperature than the
temperature of water is preferred. Accordingly then a common liquid
that could be readily used would be glycol or something of
comparable thermal properties.
The conclusive addressing
of the specification, albeit implicit specification, the analysis of
the configuration of the steam generator is straightforward.
Steam ReBoiler Retrofit
The primary factor regarding the configuration of the steam
generator is that within the context of the preferred operating
conditions and Absorber-Tubes fluid thermodynamic properties,
the energy-absorber liquid should be contained in a closed
system, and should be used in that manner. Obviously then the
liquid would be flowing through a closed tube which would
then be used as a boiler-tubes immersed in water that is to be
boiled.
In this respect then
the chosen Solar collector is quite suited for retrofit with a
Horizontal Thermosyphon Reboiler. The fact is that with such
reboilers, the heating fluid flows through a tube that is
immersed in the water being boiled. For the
|
retrofit of the hot
stream pipe from the Solar Collector, the liquid is distributed into
as many inlet tubes as per the original design of the reboiler and
then fed into the equipment. The liquid looses the heat as it flows
through the tubes, finally exiting at the outlet where the streams
are are re-accumulated into a single stream and then pumped back to
the Solar Collector yet again, in an endless circulation, except for
occasional maintenance service on the system.
Although by analysis the most appropriate
configuration for the adoption of the Solar Energy Thermal Absorber
Tubes Collectors is the Horizontal Thermosyphon Reboiler, the
a vertical thermosyphon Reboiler could also have been used. the
performance, of course, would be relatively poorer in that the hot
stream of the Solar collector would now be in Shell-side of the heat
exchanger and there would lose some heat to the surrounding even
with insulation. in general the thermodynamic efficiency would be
lower.
The adoption of the
Vertical Thermosyphon Reboiler necessarily take the conventional
form of a vertical heat exchanger: The
configuration is essentially a reboiler multi-tube heat
exchanger, in which the water flows through the tubes, and the Solar
Energy Absorber fluid flows through the shell-side. The vessels is
made of such height based on the exit temperature of the hot stream
such that the water in the tubes should come to a boil somewhere
half-way up the tubes and become full dry steam at exit from the
heat exchanger.
Accordingly then two
forms of retrofit adoption are considered for retrofit: Vertical Thermosyphon Reboiler and Horizontal Thermosyphon Reboiler.
The specifics of the implementation in each case is slightly
different.
A significant development attending this
retrofit design analysis is the ease of Utility Companies to switch over
and adopt of Solar Power without the need for acquiring inordinate extra capital expenses,
given the opportunity for reuse for the legacy power generation
system. Moreover, the
opportunity is available to all Utility Companies irrespective of
the type of steam boiler or generator currently being used for the
operations of Power Generation. |
