• Energy Research

Abstract With the further development of the island regions and the development of the marine economy, solving the problem of energy and water scarcity of island area is becoming increasingly urgent and important. This paper summarizes and analyzes the existing mode of water and energy supply system in many islands of the world, and then tried to do a preliminary analysis of the island energy systems coupled with water system, based on which a framework of island's energy and water systems was proposed. The new framework reveals a trend for the renewable energy and water-supply system from “Full Input of Energy & Water (FIEW)” to “Semi-Input of Energy & Water (SIEW)” again to “Zero Input of Energy & Water (ZIEW)”. As a case study, the renewable energy-driven water-supply system in Maldives was analyzed, and summarized its potential problems. The results show that the ZIEW (Zero Input of Energy & Water) system can be implemented in Maldives in the future, and it would be the principal direction of future energy and water-supply system in island regions.

Abstract Under the background of rapid urbanization, the original urban energy system has changed significantly. The anthropogenic heat flux play an important role in the urban energy system. In this paper, the source inventory method is selected to estimate the anthropogenic heat flux in Beijing. The results show that the total amount of AH emissions in the main zones was between 1.1×10 18 J and 1.26×10 18 J from 2007 to 2016. The structure of anthropogenic heat in Beijing also changed significantly during last ten years. The contribution of anthropogenic heat increase from 39.6% in 2007 to 57.3% in 2016, while the contribution of industrial sector decrease from 42.7% to 27.6%. The contribution of transportation have not changed significantly. The contribution of human anthropogenic heat increase from 2.6% in 2007 to 4.2% in 2016.

AbstractThe present study preliminarily estimated carbon sink of forest and carbon sink of grassland of 13 provinces of the northern China, analyzed their spatial pattern characteristics and revealed the effect of carbon reduction of the northern vegetation system in China using the forest carbon sink volume method and grassland carbon sequestration rate method by using the forest resources inventory data in China and the relevant statistical data. Analysis results illustrated that the total volume of forest carbon sink of the northern China was about 1.2*108 t, of which the advantages of the forest carbon sink of Heilongjiang, Inner Mongolia, Shaanxi and Jilin were significant. The total volume of carbon sink of grassland was about 1.78*108 t, of which the advantages of the forest carbon sink of Inner Mongolia, Xinjiang, Heilongjiang and Shanxi were significant. It was suggested in this paper that the north China should transform mode of development to further strengthen afforesting and forestation work. The Northeast China should further dig potential of carbon sink of forest and participate in the international carbon trading. The development in the northwest area of China should further strengthen the construction of ecological environment to keep capacity of carbon sink.

Abstract In recent years, clean energies are more and more valued. Applying wind power and solar power to farm irrigation can contribute to energy saving and carbon emission reduction. Based on the irrigational water demand of cassava in an area in Guangxi Province, China, this study compared the supply capacity of hybrid wind/solar power water pumping and that of photovoltaic (PV) water pumping through experiments and calculation. Results show that, the hybrid pumping system supported by a 22kW solar panel and wind turbines of 44kW can fully satisfy cassava’s water demand for irrigation in a 26.66 ha field with surplus energy, so shutdown of wind turbines in the initial stages of cassava growth is suggested. The 22kW photovoltaic water pump alone is not sufficient for a 26.66 ha field, but a 1.5-time larger solar panel (33kW) with an enhanced pump should be able to meet the demand. Considering local uneven distribution of wind power and relative high cost of a hybrid power system, the enhanced photovoltaic water pumping is recommended for popularization.

Abstract Urban water supply systems consist of water intaking, water delivery, water purification, water distribution, and other processes that require energy. As urban population increases, water resources must be drained from a larger watershed and delivered through longer pipelines. Additionally, the requirements of water purification techniques are being raised, and higher building height poses challenges to water distribution. All these factors have caused evident changes in the energy use in the water supply system. Estimation of the energy used in the water supply system is one of the bases for low-carbon city construction and assessments. This paper provides a method for assessing the energy use by a water system in an urban area and performs a case study for Beijing, China. This study investigated the urban water supply system of Beijing from 1979 to 2017 by collecting data of water sources, water treatment techniques, delivery pipelines, water pressure, and seepage rates. It estimated the energy use per cubic unit of water in the water supply system and plotted the trend through time. The results showed that the energy use per cubic unit of water supply in Beijing increased from 0.30 KWh to 0.65 KWh from 1979 to 2014. After the commissioning of the South-to-North Water Diversion Project in 2014, the energy use per cubic unit water was altered structurally and remained steady, because the water transported by the project replaced groundwater and reduced the electricity requirement for pumping. The results demonstrate that the South-to-North Water Diversion Project significantly helps Beijing reduce carbon emissions.

Abstract Green infrastructure (GI) is a low-carbon solution for urban rainwater management. Hydrological processes and the corresponding emissions of greenhouse gas (GHG) during rainfall events are optimized by GI when the latter is compared with a traditional urban drainage system. This study establishes an city-scale quantitative analysis, based on hydrological processes, with which to assess the contribution of GIs to low-carbon urban drainage systems and cities. The emission factor method is applied to measure GHG emissions. Attributable sources of emissions are wastewater treatment plants and wastewater and rainwater pumps. The amount and rate of change in GHG emissions were selected as indicators of the impacts of GI-based urban drainage systems and a case study was conducted in Dongying, China, based on 48 hydrological scenarios from 1970 to 2017. The amount of annual GHG emissions decreased by 3752.5 to 26238.9 tons of CO2 equivalent at an average of 10677.3 tons/a. The rate of annual GHG emissions decreased by 25.9–68.7% with an average reduction of 45.9%. An S-shaped logistic curve fit the data, indicated that annual rainfall is non-linearly and positively correlated with both the amount and rate of annual GHG emissions mitigated. The probability of benefits to GHG emissions in the 48 hydrological scenarios is analyzed based on a Pearson type III distribution curve. These findings can provide information that local authorities can use to guide policies towards their goals of applying GIs to mitigate GHG emissions in the urban drainage system.

In the years 2009–2013, China carried out its eighth national survey of forest resources. Based on the survey data, this paper used a biomass conversion function method to evaluate the carbon stores and carbon density of China’s arboreal forests. The results showed that: (1) By age group, the largest portion of carbon stores in China’s arboreal forests are in middle-aged forests. Over-mature forests have the least carbon storage; (2) By origin, natural forests of all age groups have higher carbon storage and carbon density than man-made forest plantations. The carbon density of natural forests and forest plantations increases gradually with the age of the trees; (3) By type (dominant tree species), the 18 most abundant types of arboreal forest in China account for approximately 94% of the nation’s total arboreal forest biomass and carbon storage. Among these, broadleaf mixed and Quercus spp. form the two largest portions. Taxus spp. forests, while comprising a very small portion of China’s forested area, have very high carbon density; (4) By region, the overall arboreal forest carbon storage is highest in the southwest part of China, and lowest in the northwest. However, because of differences in land use and forest coverage ratios, regions with arboreal forests of high carbon density are not necessarily the same regions that have high overall carbon storage; (5) By province, Heilongjiang, Yunnan, Tibet, Sichuan, Inner Mongolia, and Jilin have rather high carbon storage. The arboreal forests in Tibet, Jilin, Xinjiang, Sichuan, Yunnan, and Hainan have a rather high carbon density. This paper’s evaluation of carbon storage in China’s arboreal forests is a valuable reference for interpreting the role and function of Chinese ecosystems in coping with global climate change.

Abstract As one of many potential applications for new developments in energy, there is a need to further explore renewable energy in urban ecological construction. In this regard, the construction of urban water systems that utilize renewable energy is important for safeguarding urban ecological environments while improving the aesthetic quality of residential areas. In this study, we examine a photovoltaic water lifting and pumping method to supplement an urban water system in Xiamen, China, with reclaimed water from a nearby sewage plant, which might serve as a water source during the dry season. We analyzed the current conditions for the planned water system in the Xiang’an District, Xiamen, as well as the requirements for maintaining a constant water supply to this system. This analysis illustrated the necessity for a water system that maintains the ecological balance in the area, and the necessary conditions for adopting the photovoltaic water-supply scheme as part of the Xiang’an water system. The sewage treatment plant in the Xiang’an District requires upgrades so that the standard of its reclaimed water complies with the Class IV water quality standard for post-treatment surface water. Furthermore, we analyzed water supply scenarios for the water system in the Xiang’an District based on the conditions in 2011, when the highest number of non-rainy days in the past ten years were recorded. Based on this analysis, we propose a photovoltaic water-supply scheme and describe the structure of a compatible photovoltaic water-pumping system scheme. The pump system includes three photovoltaic pump stations: one is the main pump station that operates throughout the year for water lifting, which utilizes a reclaimed water supply, while the other two are supplementary, and serve to increase the recirculation of water in the river, and operate when necessary during the dry season. The design of the photovoltaic panels in each pump station complies with the relevant water quality standards. This paper further describes the application, ecological effects, and economic feasibility of the proposed photovoltaic water-supply scheme. This study therefore provides a potential reference for future studies related to sustainable urban development and ecological remediation while highlighting a new application of renewable energy.