Modelagem transiente do armazenamento térmico em sistemas CSP
Among the renewable energies, concentrated solar power is capable of store energy in its thermal form, which is cheaper and has energy density higher if compared to the batteries of photovoltaic systems. This technology allows solar thermal plants to dispatch energy even when climatic conditions...
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| Formato: | Dissertação |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/23095 |
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| Resumo: | Among the renewable energies, concentrated solar power is capable of store energy in its
thermal form, which is cheaper and has energy density higher if compared to the batteries
of photovoltaic systems. This technology allows solar thermal plants to dispatch energy
even when climatic conditions are unfavorable, such as in periods of cloudiness and after
sunset. This work seeks, in a general way, to verify the solar potential of the brazilian
Northeast region through a transient study of the heat losses of a sensitive heat storage
system by two active-direct or indirect tanks in relation to environmental variables such
as solar irradiation, ambient temperature and wind speed. In addition, the work also aims
to verify the sensitivity of the system to its loading level and operating temperatures.
The solar potential of the brazilian Northeast region was compared to the main world
producers of heliothermic energy. The main storage thermal energy systems in operation
in concentrated solar power plants were identified, besides the storage and insulation
materials of the tanks. The transient analysis was performed by solving the diffusive terms
of the differential equations resulting from energy balance and heat exchanges using the
FDM in the implicit formulation for discretization of the system and the TDMA method
for solving the equations. The sensitivity study of the system to the climatic conditions was
conducted for two regions with distinct characteristics, South and Northeast. Experimental
data of the Solar Two thermal storage system were used for validation of the model
proposed by this work. The heat loss rates for the simulated validation model presented
values of 97.36 kW for the fully charged hot tank and 46.12 kW for the fully charged cold
tank, these values presented differences, related to experimental models, of 4.55% and
4.82%, respectively. The heat losses of the hot tank were higher for the region of São
Martinho da Serra - RS, however the difference in storage efficiency between these two
regions was less than 1.0 %. The heat losses were relatively sensitive to the tank loading
level, with a difference of 37.35% between the fully charged and fully discharged tank.
Operating temperatures were also quite influential on the thermal storage efficiency, being
10.78% for the tank at 300 C and 89.42% for the tank at 600 C. The model developed
for this work presented results consistent with experimental measurements and with the
physical phenomenon of storage. Finally, the tank showed little sensitivity to changes in
climatic conditions, however it showed real sensitivity to the loading level and operating
temperatures. The heat losses of a thermal storage system is function of several variables
and understanding the influence of each parameter on the system is primordial for the
advancement of the technology. |
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