• Energy Research
• 11. Sustainability close
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• Energy Conversion and Management close

Abstract An attempt was made to develop multiple regression models for office buildings in the five major climates in China – severe cold, cold, hot summer and cold winter, mild, and hot summer and warm winter. A total of 12 key building design variables were identified through parametric and sensitivity analysis, and considered as inputs in the regression models. The coefficient of determination R2 varies from 0.89 in Harbin to 0.97 in Kunming, indicating that 89–97% of the variations in annual building energy use can be explained by the changes in the 12 parameters. A pseudo-random number generator based on three simple multiplicative congruential generators was employed to generate random designs for evaluation of the regression models. The difference between regression-predicted and DOE-simulated annual building energy use are largely within 10%. It is envisaged that the regression models developed can be used to estimate the likely energy savings/penalty during the initial design stage when different building schemes and design concepts are being considered.

Abstract Interest in solar chimney power plant (SCPP) has seen resurgence due to the continuously increasing awareness on environmental concerns, particularly greenhouse gas emissions from fossil fuels, since the 21st century. Although remarkable advances in the understanding of SCPP have been achieved through extensive theoretical, experimental, and numerical studies with different focuses on various aspects of the SCPP technology, no industrial scale SCPP has been built. In response to these new scientific advances and challenges for commercialization, seven questions, including parameter influences, turbine design, flow and heat transfer characteristics, similarity analysis, and hybrid systems, are presented in this work. In addition, answers and current understanding are included to provide succinct links to latest knowledge and identify areas that require further research.

Remanufacturing has received extensive attention due to its advantages in material and energy saving, emission reduction and is often considered a viable approach for the realization of a circular economy. Remanufacturing ecological performance reflects the ability of an enterprise to balance economic and environmental benefits. Therefore, evaluating the remanufacturing ecological performance is of great significance for leveraging the benefits of remanufacturing and promoting the concept of sustainability and the implementation of a circular economy in the industry. To this end, a set of data-driven techniques, i.e., data envelopment analysis, R clustering and grey relational analysis, are deployed to analyze and evaluate the ecological performance of a remanufacturing process. The effectiveness and feasibility of the proposed method are illustrated via a case study of remanufacturing for hydraulic cylinder and boom cylinder. Furthermore, a number of critical factors, e.g., energy-saving rate, remanufacturing process cost and rate of remanufacturing, for end-of-life products have been identified as the key drivers impacting the remanufacturing ecological performance. So as to improve remanufacturing ecological performance, optimizing production technology, implementing lean remanufacturing and raising public acceptability over remanufacturing products are effective measures. The research results of the present work can provide support for remanufacturing enterprises to guide and improve their ecological performance and formulate better development strategies.

Abstract The optimal turbine pressure drop ratio fopt for a solar chimney power plant (SCPP) is investigated using an analytical approach and 3D numerical simulations. Results indicate that the solar radiation and ambient temperature have obvious influences to the optimal turbine pressure drop ratio fopt and an improved performance of the SCPP system leads to a high fopt. The performance comparison between the cases with different collector shapes, a circular collector and a square collector with the same area, is conducted for the first time. It is found that the m-th power law assumption can also be applied to the SCPP system with a square collector; the values of fopt for the cases with a square collector are close to those for the cases with a circular collector. A fitting equation with variables of solar radiation and ambient temperature is obtained using the simulation results of the Spanish prototype; the results reveal that the fopt of the Spanish prototype ranges from 0.90 to 0.94 under normal climate conditions. This paper provides an approach to the preliminary estimation of plant performance, and reference data for an optimal pressure drop through solar chimney turbines.

Abstract A type of smart window using thermochromic glazing (TCG) is a promising technology for green buildings owing to the self-regulating feature and low-maintenance need. Its most important feature, thermo-optical properties that regulate the blockage of solar heat, is directly linked to the variation of surface temperatures. However, challenges from the inhomogeneity of thermo-optical properties, the coupled solar radiation and natural convection, and varying outdoor conditions all seriously hinder the understanding of its mechanism. In this paper, a validated Computational Fluid Dynamics (CFD) model achieves the simulation of inhomogeneous tinting of TCG by defining the thermo-optical properties of each finite volume according to the surface temperature. Solar radiation and natural convection at outdoor, indoor and the cavity are solved to reflect glazing temperature more accurately. The case studies compared six different switching temperatures in the range of 20 ∼ 42.5 °C with a transition gradient of 10 °C. Averaged meteorological data for both summer and winter, sunny days and cloudy days are selected to present realistic climate impacts. The result reveals the overall saving in transmitted solar radiation in summer and heating penalties in winter. It suggests the best switching temperatures for each climate condition. With the seasonal operation, the highest saving in solar heat gain is 20.9% when adopting a switching temperature of 25–35 °C, while the lowest saving can be negative, meaning TCG is not suitable for those climate zones. The proposed evaluation criteria help to quantify the applicability of TCG with the input of the summer/winter day ratio and sunny/cloudy ratio. The best region to apply TCG is where summer days are longer and winter solar radiation is significantly lower. The in-depth understanding of this temperature-sensitive process benefits the optimization of TCG in buildings, especially for its seasonal operation needs.

Abstract Photovoltaic (PV) windows are promising to reduce building net energy usage by power generation, cooling and lighting loads reduction. However, their shading effect usually leads to the rise of heating loads. A novel reversible PV window was proposed, which shared the same performance of a common one in summer but improved the solar energy utilization efficiency in winter by rotating the PV glazing into the room and reducing the heat lost to the environment. A numerical model of the proposed PV window was developed and validated with experimental data. By using the model, the thermal and electrical performance of the proposed PV window was investigated in the heating periods of Beijing and the influence of key factors on it was revealed. In comparison with a common double-glazed PV window, though the proposed one generated less electric power, its benefits from heating loads reduction outperformed the power reduction. In winter, its net electricity saving increased with the decrease of PV transparency and with the increase of glazing transmittance, and it could be 1.42–10.78, 15.67–34.57 and 18.81–39.78 kWh·m−2 lower than the reference one in naturally ventilated, non-ventilated and auto modes, respectively.

Abstract Sustainability is an important and difficult consideration for the stakeholders/decision-makers when planning a biofuel supply network. In this paper, a Mixed-Integer Non-linear Programming (MINLP) model was developed with the aim to help the stakeholders/decision-maker to select the most sustainable design. In the proposed model, the emergy sustainability index of the whole biodiesel supply networks in a life cycle perspective is employed as the measure of the sustainability, and multiple feedstocks, multiple transport modes, multiple regions for biodiesel production and multiple distribution centers can be considered. After describing the process and mathematic framework of the model, an illustrative case was studied and demonstrated that the proposed methodology is feasible for finding the most sustainable design and planning of biodiesel supply chains.

Abstract Solar chimney power plant (SCPP) is a promising renewable energy technology that needs policy support and market cultivation at the early stage of its development. An accurate prediction of the levelized cost of electricity (LCOE) can be used as basis for crafting effective support policies. This study presents an unsteady theoretical model that considers hourly meteorological data and soil heat storage in estimating the annual power generation of an SCPP. A cost benefit model is adopted to calculate the LCOE of a 10-MW SCPP in Yinchuan, a representative geographical location in the Northwestern region of China. By considering the cost advantage of China, the concessional loan, as well as the low operation and maintenance cost, the LCOE of the SCPP is estimated to be 0.4178 Yuan/kWh, which can compete with those of wind power and solar PV in China. This work lays a good foundation for the accurate prediction of power generation and provides a reference for the Chinese government in crafting effective support policies for SCPPs.

Abstract Heat dissipation through glass envelopes accounts for a large proportion of building heating loads in winter. Limiting heat transfer through windows is critical, especially considering the rapid development of glass buildings. A pipe-embedded glass envelope that arranges pipes in the shading device of a double window system is combined with a ground-source heat exchanger (GSHE) for heating in this study. The heat transfer process and energy efficiency of the presented system are simulated in consideration of diverse climatic regions. The results show that the water even much cooler than the room temperature is adequate for auxiliary heating by this system. Water at 12 °C can reduce 30% of the heat flux when the outdoor temperature is 0 °C. In addition, the coefficient of the performance of the piping system exceeds a value of 10 because water temperatures are low. The energy saving rates of the system when applied to Beijing, Shanghai, Guangzhou are 16.8%, 20.2%, and 55.9% during the heating season. In the meantime, capacity of the traditional heating system can be reduced as peak heating loads have been decreased, e.g., a reduction of 40.7% in Shanghai. And the payback period is acceptable in these cities. However, in severely cold regions such as Harbin, the energy efficiency is low because the soil temperature is too low. Overall, the studied heating system is very promising as an energy saving method for glass buildings.