Search

The importance of information and communication technology (ICT) sector on the global energy consumption and CO 2 emissions tend to grow. ICTs have a fundamental role in collaborating for a sustainable development by providing services in an efficient way, however, its own structure should also follow sustainable principles, for instance, by consuming lower energy amount. The quest for sustainability of ICTs has been focused on data centers (DC) optimization through techniques of sharing infra-structures, which would result in energy efficiency increase, carbon footprint reduction, and reduction of e-waste material disposal. In this scenario, the cloud computing technique rises as the most promising one, often receiving the “green” label. However, this label is usually based on electricity consumption reduction and disregards several other important “green” label-related aspects. This work uses emergy accounting (spelled with an “m”) and direct energy consumption in calculating indicators of eco-energy efficiency for DC operating under traditional and cloud computing techniques. A traditional decentralized DC and a centralized cloud computing DC are herein considered for illustrating figures and for discussion. Results show that centralized DC is able to provide a virtual machine (VM) by demanding 51% less electricity than decentralized DC, and it consumes 87% less electricity to store a byte. Under an emergy accounting perspective, the centralized DC demands 45% less global resources than the decentralized DC to provide a VM while demanding 85% less global resources to store a byte. Although the assessed indicators point out better eco-energy efficiency performance for the DC using cloud computing techniques, labeling it as “green” could be considered as premature due to a lack of threshold which allows for categorizing a system as “green”. Nevertheless, the centralized DC evaluated should be promoted due to its better performance as for the considered indicators. [ABSTRACT FROM AUTHOR]

Based on LEAP and WEAP, this paper establishes the coupled model of energy and water in cities. With Beijing as a case, 26 scenarios are designed to explore the energy saving/water saving of different policies in Beijing in the future and its nexus effect, including the sensitivity analysis of the results. The results show that the total energy consumption in Beijing will grow slowly by year. Carbon emissions will peak in 2020, and fluctuate after 2035 it will slowly increase until 2050. Total water demand is stable between 3.6 and 4.1 billion cubic meters. According to the forecasted water supply capacity, there is no shortage of water supply and demand. The proportion of groundwater from the source of water supply fell to 27%, and the proportion of water in the South-to-North Water Transfer increased to 40%. The total energy saving of the "13th Five-Year Plan" water saving policy is 1.003 million tons of standard coal, which is equivalent to 8.165 billion kWh of electricity. The energy saving policy has reached 276 million cubic meters of water, equivalent to 140 Kunming Lakes. The energy demand of residents' lives, service industry, construction industry and traditional manufacturing industry has a good correlation with water demand value, which proved they are important water-coupled sectors. In terms of energy-saving/water-saving effects in different scenarios and recent/long range periods, the industrial structure optimization policy showed good energy-saving potential in the short-term, but the long-term energy-saving effect was not obvious, while it was accompanied by an increase in water consumption. The irrigation technology innovation and planting structure optimization scenarios in the agricultural sector have better energy saving and water saving effects in the short term. However, with the occurrence and further expansion of water shortage, the medium and long term the water saving effect is sill, while the energy saving effect is not significant. The sensitivity analysis shows that the parameters of the scenario such as economic slowdown, industrial structure optimization, development of public transportation, and planting structure optimization are more sensitive. For the synergistic effect of water and energy conservation, the synergy effect is more obvious in the energy saving scenarios of the service industry and the industrial sector. For the policies of the same department, the synergistic saving effect of the situation of improving energy intensity is obvious. From the perspective of the difficulty in policy implementation process and overview effects, the water saving and energy saving policies of the industrial sector face more difficulties while implementation. The external power regulation policy and the capital rising residents' wareness of water saving policy has good performance both in the difficulty of implementation and overview effects. • This paper establishes the LEAP-WEAP coupled model of energy and water in cities. • Beijing energy saving policy has reached 276 million m3 of water, equivalent to 140 Kunming Lakes. • Beijing water saving policy is 1 million tce, equivalent to 8 billion kWh of electricity. • Water and energy saving policies of industrial sector face implementation difficulties. [ABSTRACT FROM AUTHOR]