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Wind and solar power are expected to play important roles in many countries to achieve carbon neutrality; however, their inherent instabilities pose significant threats to existing power grids. Because hydropower has been recognized as a viable compensatory resource for solar and wind energy uncertainties, many studies have sought to determine optimal scheduling strategies for hydro-PV, hydro-wind, and hydro-PV-wind systems. However, few studies have simultaneously considered the sizing and scheduling of large-scale hydro-PV-wind hybrid systems connected to long-distance transmission lines. Therefore, this paper develops a mathematical metric to measure the wind and solar output complementarity and incorporates it into a multi-objective sizing and scheduling model for a hybrid hydro-PV-wind system, in which resource complementarity, profit generation, system reliability, and power curtailment trade-offs are concurrently considered. The ɛ -constraint method is employed and decision makers' attitude parameters are introduced to transform the proposed model into its equivalent single objective form. A case study in China reveals that the maximum wind and solar power output complementarity rate can be at least 0.19 for the studied hybrid hydro-PV-wind system. The incorporation of wind enables the hybrid hydro-PV-wind system to provide 4.11% more load than a hydro-PV system. In addition, if 2% of power curtailment is permitted, 1.53% more load can be served and 14.9% higher profits can be earned. To better explore the application of hybrid systems, management recommendations are provided for system operators, the power industry, and management administrations. • Multi-objective sizing and scheduling method for the hybrid renewable system is proposed. • Mathematical metrics to measure wind and solar power complementarity is provided. • A complementarity rate of 0.19 can be reached with 100% reliable service and no curtailment. • Integrating wind power into the hydro-PV system can reliably serve 4.11% more load. • An optimal rather than minimal level of the renewable power curtailment is more efficient. [ABSTRACT FROM AUTHOR]

The total length of borehole heat exchangers (BHEs) is an essential issue for ground source heat pump (GSHP) systems. An insufficient number of BHEs may lead to the attenuation of long-term performance and may fail to meet the cooling or heating demands of buildings. Meanwhile, too many BHEs that exceed the system reliability requirement lead to excessive investment. In China, the total length of BHEs calculated using the current Chinese national standard GB50366-2009 is increased when a constant is simply multiplied by engineers; this approach is not economic nor reasonable. Therefore, this study revised the calculation method of the total length of BHEs in Chinese national standards by introducing a parameter called temperature penalty (T p) to ensure the long-term performance of GSHP systems and minimise the economic cost. A comparison of system reliability under the original BHE length calculation method and the optimised method was performed by simulation. The simulation method was verified through experimental measurement. Regression equations for the thermal conductivity of soil, specific heat capacity of soil, thermal conductivity of grout, daily operation time and T p were also proposed. [ABSTRACT FROM AUTHOR]

Battery lifetime is a key factor in the optimal design of hybrid renewable energy systems (HRESs). However, the integration of both battery calendar and cycle lifetimes into HRES design optimization poses challenges in achieving high computational efficiency and ensuring global optimality. In this work, a battery lifetime model considering both calendar and cycle lifetimes is adopted for the simultaneous sizing and scheduling optimization of photovoltaics-wind-battery systems. To reduce computational complexity, the nonlinear term originated from the minimum function, which determines the actual battery lifetime as the earlier-reached one of calendar and cycle lifetimes, is reformulated into a mixed integer linear programming framework. This modified model is then applied to conduct HRES design optimization in China, utilizing climate and load data with 0.5° × 0.5° spatial resolution. High-resolution results not only validate the wide applicability and satisfactory computational efficiency of the proposed model, but also underline the economic importance of incorporating both calendar and cycle lifetimes in system design. It is found that lifecycle costs of stand-alone and grid-connected HRESs could be reduced by 5000k CNY and 22,600k CNY in over 50% of the resource-abundant areas in China, respectively. Moreover, it is discovered that costs of HRESs might apparently increase when local maximum consecutive rainy days (MCRD) exceeds 3, suggesting that MCRD could be a useful indicator to assess system feasibility in diverse locations. This work provides efficient tools and valuable insights that could be generalized worldwide to assist investors and governments in the system siting, evaluation and design processes. • Design optimization of PV-wind-battery system is conducted across China. • A mode efficient model is used to integrate battery calendar and cycle lifetimes. • High-spatial-resolution analysis is performed for both on-grid and off-grid modes. • Incorporating both battery lifetimes greatly reduces cost under certain scenarios. • Maximum consecutive rainy days significantly impacts system design and cost. [ABSTRACT FROM AUTHOR]

Headforms are useful for designing and testing various types of personal protective equipment used to protect millions of workers from occupational hazards in China. Although the Chinese national standard of head-and-face dimensions for adults was first published in 1981, headforms based on those dimensions were never developed. In 2006, an anthropometric survey of 3000 Chinese civilian workers was conducted. As part of the survey, 350 subjects were scanned with a Cyberware 3D Rapid Digitizer. The manual measurements and 3-D digital scans from this survey were used to develop 3-D digital headforms that represent Chinese workers.Objective: The objective of this study was to develop headforms that represent today’s Chinese workers. Methods: Ten facial dimensions relevant to respirator fit were chosen for defining a principal component analysis model which divides the user population into five face size categories. Mean facial dimensions from manual measurements were then computed to target the ideal facial dimensions for each size category. Five scans were chosen from each face size category to be used in the construction process. Selected scans were then averaged to construct a representative headform for each face size category. Results: Five digital 3-D headforms were developed: small, medium, large, long/narrow, and short/wide. These distinct sizes of digital 3-D headforms take into account the linear distance between landmarks as well as the surface contours captured during the 3-D scan. The dimensions of constructed headforms were within ∼4 mm between the corresponding computed means and manual measurements of anthropometric landmarks for the sample population in each size category. Conclusions: These new headforms represent the facial size and shape distribution of current Chinese workers and may be useful for respirator research and development. The Chinese medium headform has a wider face width, shorter face length, and smaller nose protrusion when compared with the current U.S. standard headforms. Upon validation, it may be useful to incorporate these dimensions into Chinese and international respiratory protective devices standards. [ABSTRACT FROM AUTHOR]