Microencapsulated PCM thermal-energy storage system
The application of phase-change materials (PCM) for solar thermal-energy storage capacities has received considerable attention in recent years due to their large storage capacity and isothermal nature of the storage process. This study deals with the preparation and characterization of encapsulated paraffin-wax. Encapsulated paraffin particles were prepared by complex coacervation as well as spray-drying methods. [1]
A review of solar collectors and thermal energy storage in solar thermal applications
Thermal applications are drawing increasing attention in the solar energy research field, due to their high performance in energy storage density and energy conversion efficiency. In these applications, solar collectors and thermal energy storage systems are the two core components. This paper focuses on the latest developments and advances in solar thermal applications, providing a review of solar collectors and thermal energy storage systems. [2]
Phase change materials for thermal energy storage
Phase change materials (PCMs) used for the storage of thermal energy as sensible and latent heat are an important class of modern materials which substantially contribute to the efficient use and conservation of waste heat and solar energy. The storage of latent heat provides a greater density of energy storage with a smaller temperature difference between storing and releasing heat than the sensible heat storage method. Many different groups of materials have been investigated during the technical evolution of PCMs, including inorganic systems (salt and salt hydrates), organic compounds such as paraffins or fatty acids and polymeric materials, e.g. poly(ethylene glycol). Historically, the relationships between the structure and the energy storage properties of a material have been studied to provide an understanding of the heat accumulation/emission mechanism governing the material’s imparted energy storage characteristics. [3]
Preliminary Study of an Efficient OTEC Using a Thermal Cycle with Closed Thermodynamic Transformations
The research work is focused on thermal engine structures undergoing isobaric expansion-compression based thermal engines powered by ocean thermal energy. The isobaric expansion-compression based thermal cycles referred to in this paper, differs from the conventional quadrilateral Carnot based thermal cycles in that the conversion of heat to mechanical work is performed assuming a load reaction driven path function, where as heat is being absorbed (isobaric expansion process) and rejected (isobaric compression process), mechanical work is simultaneously performed without the conventional quasi-entropic expansion, contrary to what happens in conventional quadrilateral based Carnot engines. [4]
Assessment of Heat Flow Stability Profiles in Response to Non-Linear Thermal Potential
Heat flow stability profiles in the presence of external thermal field require careful qualitative treatment. The computational data must be considered to agree with realistic models. A hexagonal plate endowed with the thermal and material properties of a pure metal was chosen as test case and finite element algorithm was employed to obtain the numerical solutions of the temperature distributions. This was simulated with the aid of Matlab tool. Result shows that the radiation and logarithmic potentials have no disturbance on the stability profiles when compared with a control model. Classically, the circular orbits result in the event that the total internal thermal energy equals the global minimum of the applied potential. It is thus predicted that adjustment of the computational data would influence the entropy profiles of the system which in turn distorts the stability profiles in a stochastic manner. [5]
Reference
[1] Hawlader, M.N.A., Uddin, M.S. and Khin, M.M., 2003. Microencapsulated PCM thermal-energy storage system. Applied energy, 74(1-2), pp.195-202.
[2] Tian, Y. and Zhao, C.Y., 2013. A review of solar collectors and thermal energy storage in solar thermal applications. Applied energy, 104, pp.538-553.
[3] Pielichowska, K. and Pielichowski, K., 2014. Phase change materials for thermal energy storage. Progress in materials science, 65, pp.67-123.
[4] Garcia, R.F., Sanz, B.F. and Sanz, C.F., 2014. Preliminary study of an efficient OTEC using a thermal cycle with closed thermodynamic transformations. Current Journal of Applied Science and Technology, pp.3840-3855.
[5] Okoro, C.I. and Onimisi, M.Y., 2011. Assessment of Heat Flow Stability Profiles in Response to Non-Linear Thermal Potential. Physical Science International Journal, pp.106-115.
Latest Research on Hydro Power : July – 2020
Small hydro power: technology and current status
Hydropower, large and small, remains by far the most important of the “renewables” for electrical power production worldwide, providing 19% of the planet’s electricity. Small-scale hydro is in most cases “run-of-river”, with no dam or water storage, and is one of the most cost-effective and environmentally benign energy technologies to be considered both for rural electrification in less developed countries and further hydro developments in Europe. The European Commission have a target to increase small hydro capacity by 4500MW (50%) by the year 2010. [1]
A global boom in hydropower dam construction
Human population growth, economic development, climate change, and the need to close the electricity access gap have stimulated the search for new sources of renewable energy. In response to this need, major new initiatives in hydropower development are now under way. At least 3,700 major dams, each with a capacity of more than 1 MW, are either planned or under construction, primarily in countries with emerging economies. These dams are predicted to increase the present global hydroelectricity capacity by 73 % to about 1,700 GW. [2]
On the optimization of the daily operation of a wind-hydro power plant
This paper proposes the utilization of water storage ability to improve wind park operational economic gains and to attenuate the active power output variations due to the intermittence of the wind-energy resource. An hourly-discretized optimization algorithm is proposed to identify the optimum daily operational strategy to be followed by the wind turbines and the hydro generation pumping equipments, provided that a wind-power forecasting is available. The stochastic characteristics of the wind power are exploited in the approach developed in order to identify an envelope of recommended operational conditions. Three operational conditions were analyzed and the obtained results are presented and discussed. [3]
Interface between Hydropower Generation and Other Water Uses in the Piabanha River Basin in Brazil
There is an increasing need in the field of water resource management to study ways to harmonise multiple user demands. This study investigates the interface among various users of the Piabanha River basin in the state of Rio de Janeiro, in particular the implications for the electricity sector of increasing upstream consumption by other water users. To estimate future losses of generation capacity as a function of growing use of water resources, we applied a mathematical model called Simulation System for Power Plants with Consumptive Water Uses (SisUCA in the Portuguese abbreviation), considering both the existing power plant cascade and the likely future configuration with the inclusion of new projects under construction and in the planning phase, along with projections for future water demand by other users. There was some difficulty in obtaining data about the basin, but this did not impair validation of the model, which converged to results that provide support for shared management of multiple water uses. Among the results attained, it is possible to state that 75% of the maximum usable water is already being utilised, thus leading to the conclusion that water conflicts are likely in the near future. [4]
Turbine Dimensionless Coefficients and the Net Head/Flow Rate Characteristic for a Simplified Pico Hydro Power System
The basic operational parameters of a simplified pico-hydropower system with provision for water recycling were investigated. Five simplified turbine of runner diameters 0.45, 0.40, 0.35, 0.30 and 0.25 m were designed, locally fabricated, and tested in conjunction with five PVC pipes of diameters 0.0762, 0.0635, 0.0508, 0.0445 and 0.0381 m as penstocks. Five simple nozzles of area ratios 1.0, 0.8, 0.6, 0.4 and 0.2 were fabricated for each penstock diameter. The turbines were successively mounted at the foot of an overhead reservoir such that the effective vertical height from the outlet of the reservoir to the plane of the turbine shaft was 6.95 m. A 1.11 kW electric pump was used to recycle the water downstream of the turbine back to the overhead reservoir. [5]
Reference
[1] Paish, O., 2002. Small hydro power: technology and current status. Renewable and sustainable energy reviews, 6(6), pp.537-556.
[2] Zarfl, C., Lumsdon, A.E., Berlekamp, J., Tydecks, L. and Tockner, K., 2015. A global boom in hydropower dam construction. Aquatic Sciences, 77(1), pp.161-170.
[3] Castronuovo, E.D. and Lopes, J.P., 2004. On the optimization of the daily operation of a wind-hydro power plant. IEEE Transactions on Power Systems, 19(3), pp.1599-1606.
[4] Chiappori, D.V. and de Azevedo, J.P.S., 2016. Interface between Hydropower Generation and Other Water Uses in the Piabanha River Basin in Brazil. Current Journal of Applied Science and Technology, pp.1-10.
[5] Edeoja, A.O., Ekoja, M. and Ibrahim, J.S., 2018. Turbine Dimensionless Coefficients and the Net Head/Flow Rate Characteristic for a Simplified Pico Hydro Power System. Journal of Engineering Research and Reports, pp.1-17.
