Volume 1, Issue 2

In recent years extended focus has been placed on monitoring and understanding degradation mechanisms in both solid oxide fuel cells and solid oxide electrolysis cells. The time-consuming nature of degradation experiments and the disparate conclusions from experiment reproductions indicates that not all degradation mechanisms are fully understood. Traditionally, cell degradation has been attributed to the materials, processing and cell operating conditions. More recently, focus has been placed on the effect of raw material and gas impurities and their long-term effect on cell degradation. Minor impurities have been found to play a significant role in degradation and in some cases can overshadow the cell operation condition related degradation phenomenon. In this review, several degradation diagnostic tools are discussed, a benchmark for a desirable degradation rate is proposed and degradation behaviour and mechanisms are discussed. For ease of navigation, the review is separated into the various cell components – fuel electrode, electrolyte and oxygen electrode. Finally, nano-particle impregnate stability is discussed.

A huge amount of different nanomaterials is nowadays on the market used for various specific applications. Some nanomaterials such as TiO 2 , ZnO as well as several other semiconductors exhibit photocatalytic activity. Hence these materials are used for many applications, e.g., for self-cleaning and antibacterial coatings on different surfaces and for the purification of wastewater where the cleaning can be induced by simple exposure to sunlight. Because of the frequent use of these nanoparticles it is important to investigate the life cycles of these nanostructured materials as well as their environmental impact and their toxicity to animals and humans. This review first gives a short overview about nanotechnology and nanotechnological products as well as about photocatalysis and semiconductors used in this field. We then discuss the need for a new technology named nanotoxicology and the problems occurring when investigating the toxic potential of nanomaterials as well as the life cycle of nanomaterials. Furthermore, we focus on the environmental impact of TiO 2 and ZnO nanoparticles including toxic effects to bacteria, water organisms and plants as well as their toxic effects to humans including in vitro and in vivo studies.

Solar water heating can be considered to be an established mature technology. The achievement of this status is the outcome of over a century of system development that culminated with a flourish of innovation in the last thirty years. Drivers for research and development have been achieving economic viability by devising systems that, for specific applications in particular climate contexts produced more hot water per unit cost. Reductions in both initial capital and installation costs have been achieved as well as in those associated with subsequent operation and maintenance. Research on solar water heating is discussed with the emphasis on overall systems though some key aspects of component development are also outlined. A comprehensive taxonomy is presented of the generic types of solar water heater that have emerged and their features, characteristics and performance are discussed.

Solar thermochemical processes efficiently convert high-temperature solar heat into storable and transportable chemical fuels. In such processes, thermal energy is provided by concentrated solar energy and the source of hydrogen differs as a function of the investigated routes. In a transition period, carbonaceous feedstocks, such as fossil fuels, biomass, or carbon-containing wastes, can be solar-upgraded and transformed into valuable hydrogen fuel via cracking, reforming, and gasification processes. In the long term, H 2 O-splitting via thermochemical cycles based on metal oxide redox reactions can be considered to produce renewable H 2 that can be directly used in fuel cells or further processed to synthetic liquid fuels. The most promising different hydrogen production pathways are described by focussing on the existing state-of-the-art and on the latest technological advances in the field.

Conventional cooling technologies that utilize harmful refrigerants consume more energy and cause peak loads leading to negative environmental impacts. As the world grapples with the energy and environmental crisis, there is an urgent need to develop and promote environmentally benign sustainable cooling technologies. Solar cooling is one such promising technology, given the fact that solar energy is the cheapest and most widely available renewable energy that matches the cooling load requirements. However thermal storage systems are essential to overcome the disadvantage of the intermittent nature of solar energy and variations in the cooling demand. The enhanced utilization of solar energy and other consequences of thermal storage integrated systems have gained the attention of researchers in recent years. The concept of combined sensible and latent heat storage system is successfully introduced in several applications and it has many advantages. This paper presents the performance of the solar collector system and the charging characteristics of a PCM based latent heat thermal storage unit, which is designed to provide continuous supply of heat for the operation of 1 kW vapor absorption refrigeration unit. Investigations on PCM integrated thermal storage system have revealed improvement in heat storage capacity, lower heat loss and an increased solar collector efficiency due to better thermal stratification.

A simple consideration - based on an analytically solvable model of the momentum balance - is presented, which calculates the reduction in wind speed at hub height in an indefinitely large wind park as function of surface roughness, atmospheric thermal stability, and the mean distance between the wind turbines in this wind park. Weakest reduction occurs for a wind park erected on a rough land surface during unstable thermal stratification (minus 2%). Highest reduction occurs for an offshore wind park over a very smooth sea surface during stable thermal conditions (minus 45%). This model can be used to find the optimum distance between wind turbines in wind parks. Likewise this model calculates the wake length of entire wind parks as function of surface roughness and thermal stability. For offshore wind parks wake lengths between 10 and 30 km are found, for onshore parks this length is much less. This additional information can be used to find the optimum distance between adjacent wind parks.

A state-of-the-art Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) stack was investigated. The stack was a pre-commercial one, with a nominal power output of 600W. The study was focused on the electrical performance and the possible thermal energy recovery. Moreover, to evaluate the technology limitations for Distributed Generation (DG) applications, a 15 h test cycle with slow electrical power variation was performed. At the end of the tests, it was envisaged the capability of proper energy conversion efficiency. This technology appears promising for the high conversion efficiency of natural gas chemical energy into electrical energy, with proper perspectives for distributed generation.