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Supercritical CO2 (S-CO2) thermodynamic power cycles have been considerably investigated in the applications of fossil fuel and nuclear power generation systems, considering their superior characteristics such as compactness, sustainability, cost-effectiveness, environmentally friendly working fluid and high thermal efficiency. They can be potentially integrated and applied with various renewable energy systems for low-carbon power generation, so extensive studies in these areas have also been conducted substantially. However, there is a shortage of reviews that specifically concentrate on the integrations of S-CO2 with renewable energy, encompassing biomass, solar, geothermal and waste heat. It is thus necessary to provide an update and overview of the development of S-CO2 renewable energy systems and identify technology and integration opportunities for different types of renewable resources. Correspondingly, this paper not only summarizes the advantages of CO2 working fluid, design layouts of S-CO2 cycles and classifications of renewable energies to be integrated but also reviews the recent research activities and studies carried out worldwide on advanced S-CO2 power cycles with renewable energy. Moreover, the performance and development of various systems are well grouped and discussed. [ABSTRACT FROM AUTHOR]

16 % of the carbon dioxide emissions in the UK are known to originate from wet domestic central heating systems. Contemporary systems make use of very efficient boilers known as condensing boilers that could result in efficiencies in the 90-100% range. However, research and development into the phenomenon of micro bubbles in such systems has been practically non-existent. In fact, such systems normally incorporate a passive deaerator that is installed as a ‘default’ feature with no real knowledge as to the micro bubble characteristics and their effect on such systems. High saturation ratios are known to occur due to the widespread use of untreated tap water in such systems and due to the inevitable leakage of air into the closed loop circulation system during the daily thermal cycling. The high temperatures at the boiler wall result in super saturation conditions which consequently lead to micro bubble nucleation and detachment, leading to bubbly two phase flow. Experiments have been done on a test rig incorporating a typical 19 kW domestic gas fired boiler to determine the expected saturation ratios and bubble production and dissolution rates in such systems.

In this study, ultrasonic assisted osmotic pretreatment and pulsed vacuum assisted osmotic pretreatment were applied to investigate their effects on water migration and volatile components of heat pump dried Tilapia fillets. To achieve that, some effective parameters including sample drying rate, water diffusivity, microstructure, water morphology, water distribution, and volatile components were compared and analyzed with some advanced measurement devices. The water diffusivity, water distribution characteristics, and composition of volatile components were obtained after different pretreatment methods. As the drying process progresses, the sample moisture content decreases. Meanwhile, the high-degree-of-freedom water migrates to the low-degree-of-freedom water and the water-solid bond strength increases. Subsequently, the effective water diffusion coefficients of control group (without pretreatment samples), ultrasonic assisted osmosis pretreatment group and pulsed vacuum assisted osmosis pretreatment group were measured as 4.304 × 10−7m2/s, 6.109 × 10−7m2/s, and 5.003 × 10−7m2/s, respectively. In addition, the control group, ultrasonic assisted osmosis group, and pulse vacuum assisted osmosis group contained 52, 59, and 41 volatile compounds, respectively. Compared to the results from the control group, the water diffusion coefficients of ultrasonic osmotic pretreatment and pulse vacuum osmotic pretreatment increased by 41.94% and 16.24%, respectively. From the point of view of increasing drying rate, the ultrasonic penetration pretreatment provided better improvement, which was exactly consistent with the results of microstructure. On the other hand, the ultrasonic assisted osmotic pretreatment group had more types of volatile compounds, which could stimulate more flavored substances to be released. Evidently, the samples with ultrasonic assisted osmotic pretreatment showed less drying time and more aromatic substances whereas the samples from the pulsed vacuum assisted osmotic pretreatment had better protein protection feature. Although the dried samples had higher ratio of bound water and better storage stability after these two pretreatment methods, from the point of view of increasing drying rate and stimulating flavor substances, the ultrasonic assisted osmosis pretreatment method had more advantages. The research outcomes can contribute to optimize better pretreatment methods for the process of heat pump dried Tilapia fillets. [ABSTRACT FROM AUTHOR]

In this study, a small-scale test rig of CO 2 transcritical power cycle (T-CO 2 ) system driven by low-grade heat has been developed and investigated experimentally. The test rig consists of a number of essential components including a CO 2 turboexpander with high speed generator, finned-tube air cooled condenser, liquid receiver, CO 2 liquid pump and CO 2 gas generator. The CO 2 is heated in the plate-type gas generator by hot thermal oil flow which is circulated and heated by exhaust flue gases from an 80kW e microturbine CHP unit. The test rig has been fully commissioned, instrumented, controlled and is ready to operate experiment as required. Subsequently, at constant heat sink (ambient) and heat source (thermal oil) temperatures, a series of experiments have been carried out to examine the effects of various important parameters on the T-CO 2 system performance. These include thermal oil flow rate and CO 2 mass flow rate etc. Preliminary experimental results show that the CO 2 TPC is applicable for the low temperature heat sources to generate power although further efficiency improvements are needed. In addition, the experimental outcomes can instruct future optimal system design and controls. [ABSTRACT FROM AUTHOR]