A review on compressed air energy storage - a pathway for smart grid and polygeneration

The increase in energy demand and reduction in resources for conventional energy production along with various environmental impacts, promote the use of renewable energy for electricity generation and other energy-need applications around the world. Wind power has emerged as the biggest renewable energy source in the world, whose potential, when employed properly serves to provide the best power output. In order to achieve self-sustenance in energy supply and to match the critical needs of impoverished and developing regions, wind power has proven to be the best solution. However, wind power is intermittent and unstable in nature and hence creates lot of grid integration and power fluctuation issues, which ultimately disturbs the stability of the grid. In such cases, energy storage technologies are highly essential and researchers turned their attention to find efficient ways of storing energy to achieve maximum utilization. The use of batteries to store wind energy is very expensive and not practical for wind applications. Compressed Air Energy Storage (CAES) is found to be a viable solution to store energy generated from wind and other renewable energy systems. A detailed review on various aspects of a CAES system has been made and presented in this paper which includes the thermodynamic analysis, modeling and simulation analysis, experimental investigation, various control strategies, some case studies and economic evaluation with the role of energy storage towards smart grid and poly-generation

umerical simulation of atmospheric boundary layer and wakes of horizontal-axis wind turbines

Simulations of wind turbine wakes are presented in this paper using the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations employing the k-e turbulence model appropriately modified for the atmospheric flows. The actuator disk approach is used to model the action of the turbine rotor. Modified formulations of the inlet conditions and the wall functions are used to allow consistency between the fully developed atmospheric boundary layer (ABL) inlet profiles and the wall function formulation. Results are presented and compared with three wind turbines running under neutral atmospheric conditions. The results demonstrate that the accurate simulation of the atmospheric boundary layer applying enhanced inlet conditions and wall function formulation consistent with the k-e model can give very useful information about the wakes, directly contributing to the accurate estimation of the power of the downstream turbines

A COMPARATIVE STUDY ON ENVIRONMENTAL EMISSIONS AND PERFORMANCE OF A STATIONARY TYPE DIESEL ENGINE FUELLED WITH BIODIESELS DERIVED FROM TWO DIFFERENT FEEDSTOCKS

The objective of the present study was to experimentally investigate environmental emissions and performance of a stationary type diesel engine fuelled with biodiesels derived from two different feedstocks; one is more unsaturated (rice bran biodiesel) and the other one is more saturated in nature (palm biodiesel) and compare with petrodiesel. Tests were conducted in a single cylinder, air cooled, direct injection diesel engine. From the experimental results, it was found that the nitrogen oxides emissions were higher with biodiesel fuels. The hydrocarbon and carbon monoxide emissions of palm biodiesel were lower than the other test fuels. The smoke emission of rice bran biodiesel was the lowest compared to the rest of the fuels. A considerable reduction in thermal efficiency was found with both the biodiesels when compared to diesel. From the present study, it is concluded that the biodiesels derived from palm and rice bran oils with their different fatty acid composition, show lower exhaust emissions and closer performance characteristics to diesel

Fabrication and investigation of superhydrophobic surface by dip coating

The present research work is focused on to fabricate and examine the characteristics of a superhydrophobic surface on copper (Cu) substrates by dip coating method. Three different samples of ‘Cu’ are set with chemical etching, mechanical rubbing and the combination of above two methods. The variations in the exteriorsurface morphologies have been examined by profilometer, scanning electron microscope and energy-dispersive X-ray spectroscopy. The adapted samples are immersed in a solution of silver nitrate follow by immersing in a combination of ethanol and perflurodecyltriethoxysilane for 10 min. The presence of leaf and dendrites assemblies have been observed on the surface, which are useful to trap the air between them and the entrapment allows water to roll off from the surface. The outcomes reveal that the modified substrates have a water contact angle (WCA) of 159° in the case of ‘Cu’ using combination of chemical etching and mechanical rubbing followed by immersion coating. The proposed methodology has the advantage of size compatibility and easy scale up for the development of superhydrophobic surface on copper in a cost and time effective manner

Productivity enhancements of compound parabolic concentrator tubular solar stills

The performance of compound parabolic concentrator assisted tubular solar still (CPC-TSS) and compound parabolic concentrator-concentric tubular solar still (CPC-CTSS) (to allow cooling water) with different augmentation systems were studied. A rectangular saline water trough of dimension 2 m × 0.03 m × 0.025 m was designed and fabricated. The effective collector area of the still is 2 m × 1 m with five sets of tubular still – CPC collectors placed horizontally with north-south orientation. Hot water taken from the CPC-CTSS was integrated to a pyramid type and single slope solar still. Diurnal variations of water temperature, air temperature, cover temperature and distillate yield were recorded. The results showed that, the productivity of the un-augmented CPC-TSS and CPC-CTSS were 3710 ml/day and 4960 ml/day, respectively. With the heat extraction technique, the productivity of CPC-CTSS with a single slope solar still and CPC-CTSS with a pyramid solar still were found as 6460 ml/day and 7770 ml/day, respectively. The process integration with different systems cost was found slightly higher but the overall efficiency and the produced distilled water yield was found augmented

Thermal management of electronics: A review of literature

Due to rapid growth in semiconductor technology, there is a continuous increase of the system power and the shrinkage of size. This resulted in inevitable challenges in the field of thermal management of electronics to maintain the desirable operating temperature. The present paper reviews the literature dealing with various aspects of cooling methods. Included are papers on experimental work on analyzing cooling technique and its stability, numerical modeling, natural convection, and advanced cooling methods. The issues of thermal management of electronics, development of new effective cooling schemes by using advanced materials and manufacturing methods are also enumerated in this paper.

Evaluation Of Thermal Properties Of Cement-Exfoliated Vermiculite Blocks As Energy Efficient Building Envelope Material

Lightweight exfoliated vermiculite (EV) aggregate particles were mixed with cement-mortar to form exclusive cement-EV specimens of 1:0.5, 1:1, and 1:1.5 wt. % proportions, respectively. The thermal conductivity of these specimens was determined using a fabricated experimental setup, wherein the top and the bottom surface temperatures of the specimen were measured with respect to the heat flux within a specific time interval. Properties such as thermal resistivity, thermal transmittance, thermal performance index (TPI), and thermal damping are investigated using empirical relations and compared to that of the conventional cement-mortar specimen. The compressive strength was determined in accordance with the ASTM C31 standards for 7 and 28 days of curing. From the results, it was identified that the compressive strength of cement-EV 1:1 was 13.5 % less than cement-EV 1:0.5. The strength of cement-EV 1:1.5 was observed as 72 % and 51 % less than that of cement-EV 1:0.5 and 1:1, respectively. This is due to the increase in the porosity of the specimen. A significant reduction was noticed in the thermal conductivity of cement-EV 1:1.5 value (0.189 W/mK), with an increased value of resistivity (5.29 mK/W) when compared to that of the cement-mortar specimen. The TPI of the cement-EV 1:1.5 was reduced to 57 % less than the TPI of the cement-mortar, with an indication of the higher thermal stability of the material. Similarly, the results also showed an increase of 56 % and 71 % damping values for cement-EV 1:1 and 1:1.5, respectively. Hence, cement-EV proportions provide satisfactory strength and thermal properties for its usage as a lightweight building envelope in residential constructions, with higher thermal resistance and stability against fluctuating external temperature ranges