Dispatchable hydrogen production by multiple electrolysers to provide clean fuel and responsive demand in Libya

The Publisher's final version can be found by following the DOI link.The use of hydrogen as a fuel carries major environmental advantages because there are a number of ways of producing it by low-carbon methods. When electrolysis is used, additional benefits are obtained by flexible operation that offers the opportunity to reduce the cost of hydrogen production by absorbing electricity during off-peak hours, and stopping operation during peak hours. This can also act as a tool in support of balancing electrical systems. In this research, off-peak electricity is used to produce hydrogen via electrolysis, which is sold as a fuel at six garage forecourts in Darna, a small city on the east coast of Libya. In addition to the six forecourt electrolysers, a centralised electrolyser plant will be included in the system to consume the surplus energy and to satisfy any deficiency in hydrogen production at the forecourt. The capital cost of both forecourt and centralised electrolyser systems, plus fixed costs, were financed by bank loans at a 5% rate of interest over seven years. A MATLAB model with optimisation tools was used to formulate this problem. This research shows that forecourt hydrogen production at off-peak times (and without the centralised electrolyser) can satisfy nearly 53.93% of the fuel demand. This represents 59.82% of the total surplus renewable energy. The average hydrogen sale price at the forecourts is between £10.82-11.71/kg. After adding the centralised electrolyser, nearly 78.83 % of the total surplus power was absorbed and the average hydrogen selling prices were between £15.04-19.80/kg The centralised electrolyser can meet 43%, 49%, 50%, 42%, 57% and 53% of the deficit in consumption for stations 1, 2, 3, 4, 5 and 6, respectively

Potential economic benefits of carbon dioxide (CO2) reduction due to renewable energy and electrolytic hydrogen fuel deployment under current and long term forecasting of the Social Carbon Cost (SCC)

The 2016 Paris Agreement (UNFCCC Authors, 2015) is the latest of initiative to create an international consensus on action to reduce GHG emissions. However, the challenge of meeting its targets lies mainly in the intimate relationship between GHG emissions and energy production, which in turn links to industry and economic growth. The Middle East and North African region (MENA), particularly those nations rich oil and gas (O&G) resources, depend on these as a main income source. Persuading the region to cut down on O&G production or reduce its GHG emissions is hugely challenging, as it is so vital to its economic strength. In this paper, an alternative option is established by creating an economic link between GHG emissions, measured as their CO2 equivalent (CO2e), and the earning of profits through the concept of Social Carbon Cost (SCC). The case study is a small coastal city in Libya where 6% of electricity is assumed to be generated from renewable sources. At times when renewable energy (RE) output exceeds the demand for power, the surplus is used for powering the production of hydrogen by electrolysis, thus storing the energy and creating an emission-free fuel. Two scenarios are tested based on short and long term SCCs. In the short term scenario, the amount of fossil fuel energy saved matches the renewable energy produced, which equates to the same amount of curtailed O&G production. The O&G-producing region can earn profits in two ways: (1) by cutting down CO2 emissions as a result of a reduction in O&G production and (2) by replacing an amount of fossil fuel with electrolytically-produced hydrogen which creates no CO2 emissions. In the short term scenario, the value of SCC saved is nearly 39% and in the long term scenario, this rose to 83%

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Alcohol, tobacco and breast cancer – collaborative reanalysis of individual data from 53 epidemiological studies, including 58 515 women with breast cancer and 95 067 women without the disease

Alcohol and tobacco consumption are closely correlated and published results on their association with breast cancer have not always allowed adequately for confounding between these exposures. Over 80% of the relevant information worldwide on alcohol and tobacco consumption and breast cancer were collated, checked and analysed centrally. Analyses included 58 515 women with invasive breast cancer and 95 067 controls from 53 studies. Relative risks of breast cancer were estimated, after stratifying by study, age, parity and, where appropriate, women's age when their first child was born and consumption of alcohol and tobacco. The average consumption of alcohol reported by controls from developed countries was 6.0 g per day, i.e. about half a unit/drink of alcohol per day, and was greater in ever-smokers than never-smokers, (8.4 g per day and 5.0 g per day, respectively). Compared with women who reported drinking no alcohol, the relative risk of breast cancer was 1.32 (1.19–1.45, P<0.00001) for an intake of 35–44 g per day alcohol, and 1.46 (1.33–1.61, P<0.00001) for ⩾45 g per day alcohol. The relative risk of breast cancer increased by 7.1% (95% CI 5.5–8.7%; P<0.00001) for each additional 10 g per day intake of alcohol, i.e. for each extra unit or drink of alcohol consumed on a daily basis. This increase was the same in ever-smokers and never-smokers (7.1% per 10 g per day, P<0.00001, in each group). By contrast, the relationship between smoking and breast cancer was substantially confounded by the effect of alcohol. When analyses were restricted to 22 255 women with breast cancer and 40 832 controls who reported drinking no alcohol, smoking was not associated with breast cancer (compared to never-smokers, relative risk for ever-smokers=1.03, 95% CI 0.98–1.07, and for current smokers=0.99, 0.92–1.05). The results for alcohol and for tobacco did not vary substantially across studies, study designs, or according to 15 personal characteristics of the women; nor were the findings materially confounded by any of these factors. If the observed relationship for alcohol is causal, these results suggest that about 4% of the breast cancers in developed countries are attributable to alcohol. In developing countries, where alcohol consumption among controls averaged only 0.4 g per day, alcohol would have a negligible effect on the incidence of breast cancer. In conclusion, smoking has little or no independent effect on the risk of developing breast cancer; the effect of alcohol on breast cancer needs to be interpreted in the context of its beneficial effects, in moderation, on cardiovascular disease and its harmful effects on cirrhosis and cancers of the mouth, larynx, oesophagus and liver

Techno-economic assessment of dispatchable hydrogen production by multiple electrolysers in Libya

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI linkWith the worldwide growth of renewable energy generation, the value of hydrogen production by electrolysis as a demand management tool for electricity networks is likely to increase. Electrolytic hydrogen can be sold as a fuel, chemical feedstock or injected into pipelines to lower the carbon content of natural gas. The main obstacle to hydrogen’s use as a fuel or energy storage method is the price. The highest costs are in the capital expenditure and the consumption of feedstock (electricity and water). In this paper, three major techno-economic aspects of the system are investigated, including technical analyses of both the energy absorbed by the process in the provision of electricity demand management services and in its meeting of fuel demand, plus an economic assessment of the hydrogen price at the at the point of sale. Thus, the study investigates how only off-peak electricity is used to produce hydrogen via onsite electrolysis at a number of garage forecourts. In a simulated case study, six garage forecourts are assumed to be sited in Darnah, a small city on the east coast of Libya. An electricity pricing mechanism is devised to allow the energy producer (utility company) and energy consumer (garage forecourt operator) to make a profit. Short term (2015) and long term (2030) cost scenarios are applied. Matlab software was used to simulate this process. Without any government support or changes in regulation and policy, hydrogen prices were £10.00/kg, £9.80/kg, £9.60/kg, £10.00/kg, £9.40/kg and £10.30/kg for forecourts 1–6 respectively under the 2015 cost scenario. The electricity price represents around 17% of the total hydrogen cost, whereas, due to the investment cost reduction in 2030, the average prices of hydrogen dropped to £6.50/kg, £6.60/kg, £6.30/kg, £6.40/kg, £6.20/kg and £6.50/kg for stations 1–6 respectively. The feedstock cost share became 44% in the 2030 cost scenario. Nearly 53.91% and 53.77% of available energy is absorbed in short and long term scenarios respectively. Under the long term cost scenario, 65% of hydrogen demand can be met, whereas less than 60% of hydrogen demand is met under the short term scenario. The system reliability (i.e. the meeting of hydrogen fuel demand) is quite low due to the operational mode of the system. Increasing the system size (mainly electrolyser production capacity) can clearly improve the system reliability

Flexible operation of electrolyser at the garage forecourt to support grid balancing and exploitation of hydrogen as a clean fuel

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Rapid growth in the generation of renewable energy (RE) and its integration with electricity grids has been driven by concerns about both the climate impacts and the depletion of fossil fuels. Moreover, these concerns have prompted the need to develop alternatives to hydrocarbon fuels, leading to the expectation that fuel cell vehicle numbers will similarly increase. However, the variable and intermittent output of RE generators significantly affects the capability for electricity networks to balance supply and demand, although this may be addressed through energy storage and demand-side response (DSR) technologies. One potential DSR technique that can be implemented at industrial scale is water electrolysis, which is used for hydrogen production. When electrolyser operation is modulated, for example, to respond to the variable output of wind and solar power sources, it can be exploited as a dispatchable demand load. Naturally, this would need to be incentivized by electricity tariff structures that reflect the dynamics of RE availability. This paper aims to compare the economics of continuous and dispatchable electrolyser operation for producing affordable hydrogen at garage forecourts in Libya, while ensuring no interruption in the fuel supply to vehicles. Using the coastal city of Derna as a case study, with renewable energy generated by a wind farm, a suitable turbine specification and the number of turbines needed to meet demand was determined through an analysis of wind speeds. The constantly varying difference between RE power supply and electricity demand on the grinded the surplus power at any given time. Using a linear programming algorithm to optimize the hydrogen cost, based on the current price of electricity, this study examines a hydrogen refuelling station in both dispatchable and continuous operation. As the capital cost is already known, the optimisation focuses on the variable cost in order to reduce the price of hydrogen, which means using the cheaper of two electricity tariffs. Three scenarios were considered to evaluate whether the cost of electrolytic hydrogen could be reduced through using lower-cost off-peak electricity supplies: 1- Standard Continuous, in which the electrolyser operates continuously on a standard tariff of $16/kWh. 2- Off-peak Only, in which the electrolyser operates only during off-peak periods at the lower price of$7/kWh. 3- 2-Tier Continuous, in which the electrolyser operates continuously on a low tariff at off-peak times and a high tariff at other times. The results indicate that Scenario 2 produced the cheapest electricity at $3.89 per kg of hydrogen, followed by Scenario 3 at$5.10 per kg, and the most expensive was Scenario 1 at $9.26 per kg

Characterization of n-n Ge/SiC heterojunction diodes

In this paper we investigate the physical and electrical properties of germanium deposited on 4H silicon carbide substrates by molecular beam epitaxy. Layers of highly doped and intrinsic germanium were deposited at 300 and 500 °C and compared. Current-voltage measurements reveal low turn-on voltages. The intrinsic samples display ideality factors of 1.1 and a reverse leakage current of 9×10−9 A/cm2, suggesting a high quality electrical interface. X-ray diffraction analysis reveals the polycrystalline nature of the high-temperature depositions, whereas the low-temperature depositions are amorphous. Atomic force microscopy shows that the low-temperature layers have a rms roughness of 3 nm

The rectenna device : from theory to practice (a review)

This review article provides the state-of-art research and developments of the rectenna device and its two main components – the antenna and the rectifier. Furthermore, the history, efficiency trends, and socioeconomic impact of its research are also featured. The rectenna (RECTifying antENNA), which was first demonstrated by William C. Brown in 1964 as a receiver for microwave power transmission, is now increasingly researched as a means of harvesting solar radiation. Tapping into the growing photovoltaic market, the attraction of the rectenna concept is the potential for devices that, in theory, are not limited in efficiency by the Shockley–Queisser limit. In this review, the history and operation of this 40-year old device concept are explored in the context of power transmission and the ever increasing interest in its potential applications at terahertz frequencies, through the infrared and visible spectra. Recent modeling approaches that have predicted controversially high efficiency values at these frequencies are critically examined. It is proposed that to unlock any of the promised potential in the solar rectenna concept, there is a need for each constituent part to be improved beyond the current best performance, with the existing nanometer scale antennas, the rectification and the impedance matching solutions all falling short of the necessary efficiencies at terahertz frequencies. Advances in the fabrication, characterization, and understanding of the antenna and the rectifier are reviewed, and common solar rectenna design approaches are summarized. Finally, the socioeconomic impact of success in this field is discussed and future work is proposed