Solar thermochemical production of hydrogen--a review

A significant portion of the total primary energy is consumed by today's buildings in developed countries In many of these buildings, the energy consumption can be significantly reduced by adopting energy efficiency strategies Due to environmental concerns and the high cost of energy in recent years there has been a renewed interest in building energy efficiency This article strives to make an exhaustive technical review of the building envelope components and respective improvements from an energy efficiency perspective Different types of energy efficient walls such as Trombe walls, ventilated walls, and glazed walls are discussed Performance of different fenestration technologies including aerogel, vacuum glazing and frames are presented Advances in energy efficient roofs including the contemporary green roofs, photovoltaic roofs, radiant-transmittive barrier and evaporative roof cooling systems are discussed Various types of thermal insulation materials are enumerated along with selection criteria of these materials The effects of thermal mass and phase change material on building cooling/heating loads and peak loads are discussed Application of thermal mass as an energy saving method is more effective in places where the outside ambient air temperature differences between the days and nights are high Air tightness and infiltration of building envelopes are discussed as they play a crucial role in the energy consumption of a building Energy efficiency approaches sometimes might not require additional capital investment For example, a holistic energy efficient building design approach can reduce the size of mechanical systems compensating the additional cost of energy efficiency features

Passive building energy savings: A review of building envelope components

Solar thermal energy represents an increasingly attractive renewable source.However,to provide continuous availability of this energy,it must be stored. This paper presents the state of the art on high temperature(573-1273K)solar thermal energy storage based on chemical reactions,which seems to be the most advantageous one for long-term storage. The paper summarizes the numerical,experimental and technological studies done so far. Each system is described and the advantages and drawbacks of each reaction couple are considered.

/pdf/a-review-on-high-temperature-thermochemical-heat-energy-4qkpmhbwrp.pdf

A review on high temperature thermochemical heat energy storage

The review focuses on various hydrogen producing and storing methods that can be employed for creating a hydrogen economy. The latest advancements that have been made on different hydrogen storing materials and hydrogen storing technologies which have proven useful both on gravimetric and volumetric basis, have been highlighted. The encouraging and hopeful aspect of their developments is that the most of the materials are approaching the hydrogen storing capacity requirement that have been laid down by DOE. The classification of different systems has been done on basis of their storage mechanism, keeping in mind their advantages and disadvantages while they tend to store hydrogen both in the atomic and molecular form.

Hydrogen storage: Materials, methods and perspectives

Thermochemical cycles for high-temperature solar hydrogen production.

http://www.oocities.org/eblgn/ebthinfin.pdf

Natural convection in cavities with a thin fin on the hot wall

Natural convection in enclosure with heating and cooling by sinusoidal temperature profiles on one side

Conjugate heat transfer by natural convection, conduction and radiation in open cavities

Conjugate heat transfer in inclined open shallow cavities

The natural convection heat transfer in inclined rectangular enclosures with perfectly conducting fins attached to the heated wall is numerically studied. The parameters governing this problem are the Rayleigh number (102≤Ra≤2×105), the aspect ratio of the enclosures (2.5≤A=H′/L′≤∞), the dimensionless lengths of the partitions (0≤B=l′/L′≤1), the aspect ratio of micro-cavities (A≤C=h′/L′≤0.33), the inclination angle (0≤φ≤60∘) and the Prandtl number (Pr=0.72). The results indicate that the heat transfer through the cover is considerably affected by the presence of the fins. At low Rayleigh numbers, the heat transfer regime is dominated by conduction. When B≈0.75 and C≈0.33, the heat transfer through the cold wall decreases considerably. This trend is enhanced when the enclosure is inclined. Useful engineering correlations are derived for practical applications.

E. Bilgen

Papers

Natural convection in cavities with a thin fin on the hot wall

Natural convection in enclosure with heating and cooling by sinusoidal temperature profiles on one side

Conjugate heat transfer by natural convection, conduction and radiation in open cavities

Conjugate heat transfer in inclined open shallow cavities

Natural convection in inclined rectangular enclosures with perfectly conducting fins attached on the heated wall