Clean Energy

Mills, Stephen

2018 Clean Energy

doi: 10.1093/ce/zky004

Coal-fired power operators continue to look for ways to increase the efficiency and extend the working lives of their plants by improving operational flexibility and reducing environmental impact. Two possible options are explored here: combining solar energy with coal-fired power generation, and cofiring natural gas in coal-fired plants. Both techniques show potential. Depending on the individual circumstances, both can increase the flexibility of a power plant whilst reducing its emissions. In some cases, plant costs could also be reduced. Clearly, any solar-based system is limited geographically to locations that receive consistently high levels of solar radiation. Similarly, although many coal-fired plants already burn limited amounts of gas alongside their coal feed, for cofiring at a significant level, a reliable, affordable supply of natural gas is needed. This is not the case everywhere. But for each technology, there are niche and mainstream locations where the criteria can be met. The need for good solar radiation means that the uptake of coal-solar hybrids will be limited. Cofiring natural gas has wider potential: currently, the largest near-term market appears to be for application to existing coal-fired plants in the USA. However, where gas is available and affordable, potential markets also exist in some other countries.

Rusu, Eugen; Onea, Florin

2018 Clean Energy

doi: 10.1093/ce/zky003

The main objective of this article is to provide a comprehensive picture of existing wave technologies being used for wave energy extraction. The overview will explain their potential and also the challenges wave technologies face. The article will also briefly discuss the benefits of combined offshore wind-wave projects, also known as hybrids. Key factors and impacts on relevant existing wave technologies will be outlined, including capacity factor and capture width. Finally the levelized cost of energy (LCOE) targets for the most promising technologies will be discussed.

Liu, Congmin; Zhang, Zhe; Liu, Wei; Xu, Dong; Guo, Hua; He, Guangli; Li, Xianming; Deng, Yulin

2018 Clean Energy

doi: 10.1093/ce/zky001

Combustible agricultural waste is a potential source of energy because of its high organic content and heating value. As China’s economy develops, energy demand increases while environmental protection becomes more stringent. These competing demands make it urgent to find environmentally acceptable ways to extract energy from agricultural wastes. In this study, a liquid catalyst flow fuel cell (FFC) directly powered by combustible agricultural waste is investigated. This type of flow fuel cell can directly convert combustible agricultural waste at atmospheric pressure to electricity at 80–150℃ and it is environmentally friendly. Polyoxometalates act as catalysts and charge carriers to drive the FFC. Wheat straw and wine residues were used to represent the main components of combustible agricultural waste. Experiment results indicated that the power density reached as high as 111 mW/cm2, hundreds of times higher than the output of a microbial cell.

Wen, Chengyu; He, Guangli

2018 Clean Energy

doi: 10.1093/ce/zky006

This study is a review of hydrogen station patents using the Derwent Innovation system and also a secondary screening. This was undertaken by the researchers to better understand and identify hydrogen station trends. The review focuses on analyzing the developing trends of patent technologies associated with a hydrogen station. The results of the review indicated that the countries with the major distribution of patents were Japan, China, the USA and Europe. Japan is leading the developmental trajectory of hydrogen stations. The results of the analysis found the leading developers of these patented technologies are Kobe Steel, Nippon Oil, Toyota and Honda. Other active patent developers analyzed include Linde, Hyundai and Texaco. The review concludes with a suggestion that using a patent analysis methodology is a good starting point to identify, evaluate and measure the trend in hydrogen station commercial development.

Nakayama, Sumie; Azuma, Hitoshi; Fukutome, Suguru; Ogimoto, Kazuhiko

2018 Clean Energy

doi: 10.1093/ce/zky005

The growth of renewable energy has accelerated globally toward a low-carbon economy since the Paris Agreement entered into force in 2016. As a result of the increase of variable renewable energy (VRE), namely solar PV and wind, power systems require more flexibility from conventional power plants with less power generation to regulate increased variability. There are sources of flexibility other than conventional power plants, including enhanced power networks, storage capacity and demand response. To maximize economic utilization of VRE power generation, it is necessary to use the flexibility potential from all these sources. In Japan, the share of VRE has increased since the introduction of a feed-in tariff (FIT) and, in parallel, power market reform is underway. Japan has a unique power system of nine grids connected like a fish bone, making the uptake of an increasing share of VRE challenging. This paper assesses the value of flexibility by source in Japan’s power system in 2030. An analysis of different VRE scenarios is undertaken based on a newly developed production cost model. The result of the simulation shows the quantitative impact of each source of flexibility to the generation cost and VRE curtailment and demonstrates the mechanism by which flexibility works to impact VRE curtailment.

Amoo, L M

2018 Clean Energy

doi: 10.1093/ce/zky007

Renewable energy is plentiful; we need only develop the technology to harness and distribute it efficiently and economically. The conversion of energy to electricity continues to be an area of interest for engineers and researchers. Tidal energy has been classified as one of five energy innovations that could transform our world—the others being fuel cells, lithium–air batteries, the smart grid, and space-based solar power (http://oilprice.com/Alternative-Energy/Renewable-Energy/5-Clean-Energy-Innovations-That-Could-Transform-Our-World.html). Resource engineering assessment constitutes the first step to the effective utilization of any resource. There are various candidate sites for tidal stream energy in Nigeria. The objective of this research is to examine the tidal stream resource potential of seven coastal sites using the modified continuous wavelet transform (CWT) method with a levelized cost of energy (LCOE) analysis. Foster’s method is newly applied to the aperiodic tidal series data. The results indicate that meaningful power is viable and could be economically extracted at each respective site, with peak mean approximate velocities at each site of ~10 m/s, and the LCOE estimate was found to be lower than that of the International Renewable Energy Agency (IRENA). This work represents the culmination of a series of papers exploring tidal energy resources in tropical Nigeria.

Zhao, Jingbo; Deng, Wenxing; Yin, Zonglin; Zheng, Haibo; Hu, Ting; Yu, Weilin; Luo, Huageng

2018 Clean Energy

doi: 10.1093/ce/zky008

This article introduces a portable wind turbine condition monitoring system (CMS) and its applications in wind turbine drivetrain damage detection. The portable CMS based on vibration detection and analysis has a long application history in conventional rotating machineries, but it is not widely used in wind turbines. There are several reasons why it is not used, including the labor- and knowledge-intensive requirements for test setup and result interpretation. There are also reasons specific to wind turbines, such as the structural diversity of drivetrains, the uncertainty of operational conditions, and the complexity of the damage mechanism of different parts that make the conventional vibration-based CMS inefficient and not cost-effective. All these factors affect the wide application of the portable system. The portable wind turbine CMS discussed in this article is integrated using advanced vibration measurement and analysis methodology. Fault detection for the acquired acceleration response and high-speed shaft speed signal is carried out by a suite of data analysis techniques specifically designed for a wind turbine gearbox. Using these techniques, damage detection accuracy for all the components inside a gearbox is improved significantly, especially for those related to medium- and low-speed shafts. The new data processing techniques also are briefly described with the developed methodologies verified by three wind turbines with typical low-speed shaft-related component damages. These damage assessments include the low- and medium-speed planetary stage ring gear, the low-speed planetary stage planet gear and damage to the main bearing.

Nuortimo, Kalle; Eriksson, Timo; Kuivalainen, Reijo; Härkönen, Janne; Haapasalo, Harri; Hyppänen, Timo

2018 Clean Energy

doi: 10.1093/ce/zky002

This article discusses the market potential estimation results at different stages of second-generation oxy-fuel technology for carbon capture and storage, where oxygen content is increased in order to increase efficiency and product life cycle. The article highlights the challenges to commercializing an energy technology with long development lead times. Challenges related to external market environment, regulations and market price for carbon dioxide (CO2) also need to be resolved. The study is based on a second-generation oxy-CFB technology evaluation, SWOT analysis and product life-cycle estimation. The commercialization of second-generation oxy-fuel technology, estimated as a basis of oxy-CFB technology, is largely found to be dependent on technical, sociological and economical aspects related to the energy market environment. The CO2 price in European Union (EU) emissions trading is currently below 10 €/ton, which does not favour investment in CCS. CO 2 storage also faces public opposition and EU directive limitations. The CO 2 price needs to be in the range of 30 €/ton by 2030, the estimated time of commercialization. Technological development or subsidies would also be required for the second-generation oxy-CFB power production concept to become viable. This is one of the critical factors in market deployment as the price development is influenced by several external factors, including the EU’s environmental policy, politics and public acceptance.

Wen, Chengyu; He, Guangli

2018 Clean Energy

doi: 10.1093/ce/zky014

This is a correction notice for article zky006 (DOI: https://doi.org/10.1093/ce/zky006), published on 10 May 2018. Due to an error, the images for figures 1, 2, and 3 were swapped over. These have now been corrected in the published article. Fig. 1 View largeDownload slide Tendency of patent activity in the area of hydrogen station Fig. 1 View largeDownload slide Tendency of patent activity in the area of hydrogen station Fig. 2 View largeDownload slide Hydrogen station patent technology activity in priority countries Fig. 2 View largeDownload slide Hydrogen station patent technology activity in priority countries Fig. 3 View largeDownload slide IPC (Top 15) analysis of patented technologies Fig. 3 View largeDownload slide IPC (Top 15) analysis of patented technologies © The Author(s) 2018. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact [email protected]