Complementary Resources for Tomorrow

Tomorrow literally means the day after today, but is also used to describe some point in the future. However, in terms of the transition to renewable energy what is that point, 2030, 2050, 2100, or even later? On the basis of 3 generations per century, by 2100 the grandchildren of those born at the start of the 21^st century will be having their own children. By this time, although birthrates are decreasing, life expectancy is increasing, and the global population is likely to be 48% higher than 2017, but could increase by 75%. It has been estimated that the amount of energy required by 2100 could be up to 124% higher than it is today. Consequently, it is highly unlikely that fossil fuels alone, irrespective of enhanced efficiencies of utilization, will be able to meet this demand. So other energy sources will be required regardless of the concerns of anthropogenic activity on climate change. Moreover, there are non-binding international commitments to be carbon-neutral no later than the second half of this century. However, because of these concerns the development of alternative energy sources will likely continue to concentrate on those that are sustainable and renewable. Will such sources be able to meet the increasing demand for energy, or indeed, be able to meet the overall global energy needs in the total absence of fuels which are not carbon-neutral as required by the UN’s Paris Climate Agreement? A recent study by a Stanford Group, based on the energy scenarios of 139 countries, concluded that all their energy needs could be met by renewables by mid-century, albeit that the rigor of their analyses has been challenged. Whatever the accuracy of such predictions, the underlying assumption that all countries will buy-in to the wholly renewable scenario is highly optimistic. The World Energy Council, in their ‘hard-rock’ 2060 setting have suggested that the availability of local resources and the concomitant political pressures will prevent global collaboration on energy and climate change issues. Thus, while predicting the eventual transition away from the dominance of fossil fuel energy is easy, the hard part is predicting when. A discussion of some of the factors involved in that prediction is a focus of this paper. In particular it is highlighted that there is no universally accepted definition of what constitutes a ‘renewable source’ and this is shown to create some ambivalence in the literature when discussing the use and future development of biomass and hydropower. Other anomalies are also apparent in that while Nuclear power is not a renewable it is a zero-carbon emission energy source but remains politically and socially unpopular. It is also clear that other factors, in addition to climate science and cleaner technologies, such as demographics, economic and varying regional policies are playing increasingly important roles in shaping what tomorrow’s global energy mix is likely to be. Consequently, a number of socioeconomic energy scenarios are being developed and studied. To date the findings of such investigations will disappoint many, since it appears that the use of fossil fuels will not be universally abandoned any time soon and therefore it seems unlikely that renewable sources alone will be used to meet all the global energy needs of the defined ‘tomorrow’ of this paper.

This study investigates a hybrid thermal insulation system for subsea pipelines. The insulation system combines a traditional insulation material, Aerogel, with a phase change material (PCM), paraffin wax, for thermal energy storage to better regulate fluid temperatures and improve flow assurance for subsea pipelines. This paper first discusses flow assurance challenges, including hydrate formation and wax deposition, for subsea pipelines in the harsh environment. Different mitigation methods are then reviewed, particularly the thermal insulation methods to prevent heat loss from the pipelines. Analytical and numerical heat transfer analyses show that the hybrid thermal insulation system can be designed with proper thickness of the Aerogel and PCM layer for heat loss prevention and cool down time extension during a flow line shut-in operation. A lab-scale prototype is designed, fabricated and experimentally tested on a flow loop. Measured temperatures provide useful data to understand the transient heat transfer in the hybrid insulation system, as well as lab demonstration of the good insulation performance, with the cool down period extended by more than three times than an Aerogel only case.

A large disadvantage to conventional diesel engines is the particulate matter emissions that are produced. The trade-off between NO_x and soot emissions has been the major challenge for diesel diffusion combustion. Exhaust gas recirculation is an established technique used to suppress NO_x emissions by diluting the combustion mixture, thus reducing the flame temperatures. In an effort to minimize soot emissions, studies on alternative fuels detail appealing emission advantages. Neat dimethyl ether (DME), an oxygen-borne fuel, presents itself as a high reactivity fuel with no carbon-to-carbon bonding. Furthermore, DME has good mixing ability, primarily owing to its low viscosity and surface tension. The spray characteristics of DME fuel injection are important for DI engine application. The injections are recorded with a high-speed camera to capture the spray behaviour, by means of measuring the spray cone angle and penetration length. In this work, high-pressure fuel injection sprays of DME fuel are analyzed and compared with those of diesel and n-butanol fuel. The results reveal that DME offers a wider spray cone angle and slower penetration rate than diesel and n-butanol fuel under 1 bar absolute background pressure. Under 110 °C background temperature, the DME fuel spray exhibits an enhanced flash boiling effect. These effects are strongly affected by background pressure.

Energy security, volatile petroleum prices, source depletion issues and global climate change have driven countries to consider adding alternative and renewable energy options to their conventional energy sources. The use of vegetable oil-based biofuel as an option instead of diesel is important for development of sustainable and eco-friendly energy sources. The fatty acid composition of biodiesel manufactured from diverse plant resources and their properties are different. The aim of the present paper is to select the most feasible vegetable oil as biodiesel by using Analytical Hierarchy Process technique, one of the multi-criteria decision making methods based on priority estimation model. Among vegetable oil species, the problem of selecting the most feasible vegetable oil is evaluated, using numerous criteria related to their properties. This article highlights a novel insight into assessment of the feasible vegetable oil-based biodiesels for the decision makers such as research and development engineers and engine manufacturers to empower the green revolution to obtain the emission norms and fuel economy. The quantitative results indicate that the Corn with a global priority of 0.0636 is the option that contributes the most to the goal of selection the best plant oil that satisfies all the criteria selected. On the other hand, Palm and Pumpkin are the vegetable oil alternatives that are ranked last with equal priority values of 0.0337.

Rice is the primary staple for the world’s population and it is one of the main cereals in the world. The tremendous global rice production results in a huge amount of rice husk, making rice husk a very important biomass fuel. LHV (lower heating value) and exergy are two important properties of a biomass fuel, and they are generally used for evaluating the energy of a biomass fuel. Also, exergy is usually used to assess the energy quality of a biomass fuel. This study aims to investigate the LHV and exergy of rice husk. The LHVs and exergy values of twenty eight rice husk samples are investigated in this study. The results show that the LHVs and exergy values of the rice husk samples are in the ranges of 8879.12–16200.00 kJ/kg and 10918.01–18457.87 kJ/kg, respectively. The higher LHV of a rice husk the higher exergy of the rice husk, and a positive linear relationship between exergy and LHV is observed for the rice husk samples. The relative errors between the estimated and calculated exergy values are in the range of −3.678%–1.704% for the rice husk samples, the simple relationship proposed in this study can therefore be used as an expeditious methodology for estimating the exergy of rice husks.

As a solid-state energy convertor, the thermoelectric generator (TEG) has been widely applied in heat recovery systems. However, its lower efficiency (about 5–7%) is one of the main challenges to employ the TEG technology further. Based on simulations, this research mainly investigated the effects of geometry parameters and substrate materials on TEG performance. A 3-D model for a TEG was created using ANSYS Workbench and validated using experimental results from the literature. A dimensionless parameter, shape factor ratio, was used to describe the geometrical characteristics of the P-N couples. In this study, this parameter is actually a ratio between the cross-sectional area of P and N semiconductors. Five values of shape factor ratios were considered. In addition, various combinations of couples’ lengths were also simulated as it is an important geometric parameter of a TEG. Finally, the effect of the substrate material (Zirconia, Boron Nitride, Aluminum Oxide, Aluminum Nitride, and Silicon Carbide) on the TEG performance was analyzed. Through the modeling study, it was shown that the performance of this TEG model is maximized when the shape factor ratio is 1. Meanwhile, couple length had opposite effects on output power and efficiency of the TEG. Finally, it was found that the most conductive substrate (Silicon Carbide) resulted in the best TEG performance.

This study investigates how artificial intelligence (AI) at offshore wind farms could potentially both improve meeting Annual Energy Production (AEP) targets as well as reduce avian mortality rates resulting from turbine collision. While turbine-related bird deaths are widely skewed in the current literature, this research aims to completely reduce the already low bird mortality statistic caused via wind power operation by providing solid evidence of true mortality rates. Additionally, securing long-term investments with stakeholders and increasing market size will be a side effect of the undergone investigation. This research took place along the Coastal Regions of Denmark and in California, USA, where heavy migratory flyways lie near offshore Vestas wind parks. As a collaborative research partner to Aarhus University, Vestas Wind Systems A/S engaged in research and testing throughout the duration of this study. A literature review comparing existing bird tracking technologies used for collision-avoidance purposes is examined and a SWOT analysis performed. This paper addresses gaps in the existing technologies while also introducing a new and improved approach to siting future wind projects. Since wind turbine curtailment can cost manufacturers and owners up to $100 per turbine per hour, this research additionally aims to reduce curtailment onset thanks to AI technology learning site-specific spatial patterns. By combining multi-sensory information from motion-sensor cameras, eBird database, magnetic fields and Doppler radar the following paper illustrates how such information can deem useful in improving collision-avoidance systems while also providing more knowledge of local conditions for both existing and future wind projects.

Existing statistical data on the sources of global electricity generation show that the world has been very slow to adopt renewable sources of electricity generation to replace our over reliance on fossils for such generation. Most modeling agrees that over the next 30 years, global demand for electricity will at least double meaning there is a requirement to bring an additional 3 TW of electrical generation on line. Ideally these new forms of electricity generation should be renewable and sustainable. It is in that context where we examine the feasibility of OFF shore wind and its capability of delivering this required 3 TW. On balance, there is reason to be optimistic in this approach. This optimism is largely based on the relatively rapid deployment of OFF wind facilities, primarily lead by the UK beginning in 2013 with the completion of the London Array. In addition, OFF shore deployment in 2013 used individual 3.6 MW turbines whereas by 2023, 12 MW turbines will likely become the unit turbine per OFF shore array, This is a significant increase in the scalability of this technology and a global commitment to eventually produce and install 10,000 12 MW turbines on an annual basis will reach the target goal of 3 TW. Here, we examine various logistical and material limitations that could possibly hinder the deployment of OFF shore arrays and conclude such potential obstacles can be overcome, although innovative transport and assembly infrastructure will be needed for the 107-m long blades that comprise a 12 MW turbine. The relatively high capacity factor of OFF shore windfarms (40–50%) favors this technology over solar PV which has a much lower capacity factor. Furthermore, nuclear power has a history of relatively slow build out and it’s very unlikely that this build out could be ramped up so that nuclear is a significant component of the required 3 TW; but in fact, since this can all be achieved through OFF shore wind, there is no real need for that alternative. As such, OFF shore wind production has a very bright future ahead of it and this should guide the necessary worldwide investment needed to help bring a new era of sustainability to the planet.

The wave energy conversion industry is in the early stages of progress and so far, few ideas have been implemented. Among them coastline converters have attracted major attention which is probably due to their simplicity and low maintenance costs. Oscillating Water Column (OWC) is one of the first implemented wave energy converters with large numbers of deployed prototypes. Because the bulk of the costs associated with the production of wave energy is spent on the design and construction phases of the structure, it is affordable to integrate the plant structure into a breakwater which is mainly used for coastal or harbor protection and an energy converter device. This has the advantages of saving the cost for construction and maintenance of the plant. In this paper, using Smoothed Particle Hydrodynamics (SPH) method the reflection coefficients of a multipurpose breakwater-OWC wave energy converter was studied. Results showed that OWC dramatically reduces the reflection coefficient from breakwater. Also, for these devices there is an optimum incident wave period for minimum reflection coefficient.

Computational Fluid Dynamics (CFD) was used to assess whether adding a stationary diffuser, known as wind lens, can improve the power performance of vertical axis wind turbines. Transient, two-dimensional simulations were conducted using a dynamic mesh and the Shear-Stress Transport (SST) \( k - \omega \) model to calculate the generated torque. Blades were set to rotate at a constant angular velocity to maintain an optimal TSR (tip speed ratio) at the studied freestream wind speed. The product of this angular velocity (in rad/s) and the calculated torque (in Nm) was assumed to be the mechanical power harvested by the turbine. The simulation setup was validated using experimental data. It was found that a properly designed wind lens enhances power production in two ways. First, it collects and guides a larger air flow into the turbine (the inlet effect). Second, it induces a flow separation along its trailing edge, which leads to a reduced pressure zone downwind of the outlet of the lens (the outlet effect). The enhanced pressure difference between upstream and downstream regions drives a larger flow into the turbine, which increases power generation. It was also found that if the throat of the diffuser is not sufficiently large, the shear caused by its inner walls decelerates the blades. This negative impact can dominate the above-described inlet/outlet effects, which leads to a net reduction in power production. Although no rigorous optimization was conducted to identify an optimal geometry for the diffuser, the proposed lens was found to improve power production of the turbine by more than 400%. It is shown that substituting the augmented turbine with a large open turbine with a swept area equal to the maximum cross-sectional area of the lens is a more effective strategy (increases power production by 600%), however, it may cost considerably more.

The performance of cavern-based Compressed Air Energy Storage systems is highly dependent on the ambient condition. In this work, the effect of ambient temperature and pressure on the round trip efficiency of this technology is investigated via exergy analysis. Three different cavern sizes 8k, 140k, and 450k cubic meters are considered. The result showed that the highest exergy destruction occurs in the intercooler, while the heat exchangers are most sensitive to weather variations. Also, low-pressure compressors and heat exchangers are more sensitive to the weather than their high-pressure counterparts. Detailed exergy analysis showed that for the large cavern size case, intercooler alone is responsible for 56% of exergy destruction of the plant in hot weather condition, followed by compressors and turbines group, cavern, heat exchangers and motors and generators with 20%, 9%, 8% and 7% of the total exergy destruction. Efficiency analysis revealed that cavern-based CAES plants have greater efficiency in cooler weather conditions, and the effect of ambient temperature and pressure on larger plants is smaller. The results of this work can serve as a guideline for predicting the effect of ambient condition on the efficiency of both cavern-based and regular compressed air energy storage systems.

The increasing attempt for energy saving in buildings needs the precise estimation of the thermal characteristics of buildings. In order to accomplish this goal, it is very important to conduct a transient thermal analysis of the building. However, the prior knowledge of the thermophysical properties of the building walls is essential to predict its thermal performance. Particularly when investigating existing and old buildings, for the case of renovation, wall materials and their thermal properties might be uncertain. To resolve this problem, the thermophysical properties are evaluated based on data obtained by in situ measurements of surface temperature and heat flux. Problems including complex geometries, which lead to thermal bridging effects, require more realistic, two or three-dimensional models to account for these effects. Therefore, the first objective of this study is to review the existing models available in the literature to investigate the thermal performance of buildings. The second objective is to present a numerical model for estimating the thermophysical properties of the building walls. The optimization process is integrated into the finite element analysis for solving one and two-dimensional coefficient inverse problems of heat transfer. The model is used to obtain the thermo-physical material properties of an equivalent wall, which provides a matching to the thermal flux behavior of an original multilayer wall under the same transient thermal boundary conditions and accounts for thermal bridges. The model presented in this investigation is considered promising to estimate the thermophysical properties of equivalent walls.

A snow melting system based on a ground source heat pump was implemented in Harbin, the coldest provincial capital of China. Two control methods (automatic on/off and variable frequency) were applied to investigate the performances of the snow melting system. Two continuous operations were conducted for 4 h which is the time for the snow melting. The ambient temperatures, the temperatures of supplied water and the energy analysis (COP, coefficient of performance) of the snow melting system were detailed. The results indicate that the variable frequency control method can supply more steady hot water (the maximum error values and accuracies were decreased by 63.9% and 64.2%, respectively) and it has higher energy efficiency (the average COP_sys and COP_hp were increased by 19.8% and 56.8%, respectively) as compared with the automatic on/off control method.

The present paper is aimed at the in-depth thermal-hydraulic analysis of supercritical water flow at various operating conditions in vertical circular tubes. Computational fluid dramatics model using two turbulence models, Reynolds Stress Model and \( {\text{k}}\,{-}\,\upomega \) SST model, have been used for the analysis in this paper. Three experimental cases, which are operated at various working regimes, are chosen for the detailed analysis of deteriorated heat transfer and normal heat transfer cases. The studies are carried out for the turbulent properties and velocity profiles and their effects on the heat transfer in the vertical circular tubes. It is found that the sharp increase in the wall temperature vanishes if the gravity is neglected. Hence, it can be concluded that buoyancy plays a dominant role in deteriorating the heat transfer for the cases of a low mass flux condition. Besides, the turbulence is found to be suppressed severely for the deteriorated heat transfer and is one of the reasons for the deterioration in heat transfer. Both turbulent models predicted the suppression phenomenon. However, compared with the previous direct numerical simulation studies, which showed two peaks in the turbulent kinetic energy profile, the \( {\text{k}}\,{-}\,\upomega \) SST model fails to predict the proper turbulent kinetic energy profile in the near wall region, which showed only one peak or no peak for the turbulent kinetic energy in the whole flow region.