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In order to clarify the dependence relationship between the heat storage & preservation wall and the thermal environment, and to provide data base and theory foundation for the north wall construction of the Chinese solar greenhouse (CSG), the experimental measures has been employed to investigate the distributions of temperature, humidity and heat transfer of three different wall materials (i.e. perforated brick, fine coal ash brick, common clay brick). The dynamic variations of the heat-storage and heat-release processes were identified, and the thermal response characteristics were discussed. The effect of north wall materials on the thermal environment of the solar greenhouse in northern China was revealed. The results indicated that the daily heat-storage and heat-release of fine coal ash brick wall can reach ϕimput = 34.5~130.6 W·m−2 and ϕoutput = −24.15~-45 W·m−2, respectively. The daily heat-storage time can reach t = 5~8 h, and the wall temperature at night can be 3~4∘C higher than the air temperature. Moreover, the maximum indoor temperature of the fine coal ash brick wall can be maintained at t ≤ 16.7 ≤ 31.1∘C, the minimum humidity can be maintained at 29.75~45%. Fortunately, the construction cost is moderate, while the physical properties are obviously better than those of perforated brick and common clay brick in the CSG. The overall thermal performance of fine coal ash brick is the best of the three north wall materials, and it can make the most advantage of the heat-storage and heat-preservation performances of the CSG. As a consequence, the fine coal ash brick wall of the solar greenhouse has good promotion value in northern China and other high latitude, high altitude and long winter regions.

The current building’s energy supply chain model has the characteristics of high complexity, time-consuming, poor accuracy, and high pollution coefficient. In this paper, a renewable building’s energy supply chain model based on LCA is proposed. Based on the definition of planned supply chain, procurement, construction and delivery process, the operation reference model of renewable green building’s energy supply chain is analyzed. According to the analysis of LCA, the life cycle stage set of renewable green building’s energy supply chain is obtained. A renewable green building’s energy supply chain model with economic and low-carbon comprehensive objectives is obtained by combining the economic goal-oriented model with the low-carbon goal-oriented model and introducing the life cycle stage set. The experimental results show that the modeling complexity of the model is low and the time-consuming is less. The model fits the actual situation well. The pollution coefficient of the model is smaller than that of the current model. It is practical and provides technical reference for the field of green building.

This paper investigates the problem of reactive power sharing based on virtual flux droop method. Firstly, flux droop control method is derived, where complicated multiple feedback loops and parameter regulation are avoided. Then, the reasons for inaccurate reactive power sharing are theoretically analyzed. Further, a novel reactive power control scheme is proposed which consists of three parts: compensation control, voltage recovery control and flux droop control. Finally, the proposed reactive power control strategy is verified in a simplified microgrid model with two parallel DGs. The simulation results show that the proposed control scheme can achieve accurate reactive power sharing and zero deviation of voltage. Meanwhile, it has some advantages of simple control and excellent dynamic and static performance.

Gird-connected Photo-Voltaic (PV) systems rated as 5-10 kW level have advantages of scalability and energy-saving, so they are very typical for small-scale household solar applications. In this paper, an 8 kW three-phase grid-connected PV system model is proposed and studied. In this high-fidelity model, some basic PV system components such as solar panels, DC-DC converters, DC-AC inverters and three-phase utility grids are mathematically modelled and organized as a complete simulation model. Also, an overall power controller with Maximum Power Point Control (MPPT) is proposed to achieve both high-efficiency for solar energy harvesting and grid-connection stability. Finally, simulation results demonstrate the effectiveness of the PV system model and the proposed controller, and power quality issues are discussed.

In this paper the design stages of a mixed photovoltaic-wind energy system, supplied with solar and wind energy was discussed. First, general information about the employed wind turbines and solar panels is given and their basic characteristics are addressed. Then, essential information for the system setup and measurements was given. The system setup, operation of the system, the ways to store energy and how energy is consumed were described and the results were interpreted. This study serves as a background for the experimental studies in the future. [ABSTRACT FROM AUTHOR]

Wind power introduces variability into electric power systems. Due to the physical characteristics of wind, most of this variability occurs at inter-hour time-scales and coal units are therefore technically capable of balancing wind. Operators of coal-fired units have raised concerns that additional cycling will be prohibitively costly. Using PJM bid-data, we observe that coal operators are likely systematically under-bidding their startup costs. We then consider the effects of a 20% wind penetration scenario in the coal-heavy PJM West area, both when coal units bid business as usual startup costs, and when they bid costs accounting for the elevated wear and tear that occurs during cycling. We conclude that while 20% wind leads to increased coal cycling and reduced coal capacity factors under business as usual startup costs, including full startup costs shifts the burden of balancing wind onto more flexible units. This shift has benefits for CO _2 , NO _X , and SO _2 emissions as well as for the profitability of coal plants, as calculated by our dispatch model.

Estimates of global primary bioenergy potentials in the literature span almost three orders of magnitude. We narrow that range by discussing biophysical constraints on bioenergy potentials resulting from plant growth (NPP) and its current human use. In the last 30 years, terrestrial NPP was almost constant near 54 PgC yr ^−1 , despite massive efforts to increase yields in agriculture and forestry. The global human appropriation of terrestrial plant production has doubled in the last century. We estimate the maximum physical potential of the world’s total land area outside croplands, infrastructure, wilderness and denser forests to deliver bioenergy at approximately 190 EJ yr ^−1 . These pasture lands, sparser woodlands, savannas and tundras are already used heavily for grazing and store abundant carbon; they would have to be entirely converted to bioenergy and intensive forage production to provide that amount of energy. Such a high level of bioenergy supply would roughly double the global human biomass harvest, with far-reaching effects on biodiversity, ecosystems and food supply. Identifying sustainable levels of bioenergy and finding ways to integrate bioenergy with food supply and ecological conservation goals remains a huge and pressing scientific challenge.

We use time- and frequency-domain techniques to quantify the extent to which long-distance interconnection of wind plants in the United States would reduce the variability of wind power output. Previous work has shown that interconnection of just a few wind plants across moderate distances could greatly reduce the ratio of fast- to slow-ramping generators in the balancing portfolio. We find that interconnection of aggregate regional wind plants would not reduce this ratio further but would reduce variability at all frequencies examined. Further, interconnection of just a few wind plants reduces the average hourly change in power output, but interconnection across regions provides little further reduction. Interconnection also reduces the magnitude of low-probability step changes and doubles firm power output (capacity available at least 92% of the time) compared with a single region. First-order analysis indicates that balancing wind and providing firm power with local natural gas turbines would be more cost-effective than with transmission interconnection. For net load, increased wind capacity would require more balancing resources but in the same proportions by frequency as currently, justifying the practice of treating wind as negative load.