Hybrid geothermal–fossil electricity generation from low enthalpy geothermal resources: geothermal feedwater preheating in conventional power plants

Hybrid steam power plants with geothermal feedwater preheating enable the conversion of geothermal energy into electricity in countries with low enthalpy geothermal resources. In order to estimate the potential of geothermal–fossil hybrid power plants with geothermal feedwater preheating, we examine the application of this concept using the examples of two modern coal fired power plants. In addition, energy output and economic efficiency calculations will be compiled for this concept utilising the thermal water data of an existing geothermal heating installation and an experimental facility for the hot dry rock technology. The process of geothermal feedwater preheating as a means of improving performance forms both an alternative and an extension to the existing electricity generation methods based on renewable energy. Photovoltaics or wind power, for example, tend to be expensive and also unreliable due to weather uncertainties. An electricity cost of around 85 EUR/MWh appears to be attainable through the geothermal preheating concept in Central Europe. In countries with the appropriate prerequisites, this concept heralds considerable benefits in terms of efficient electricity generation and environmental protection.     

Current status of research on optimum sizing of stand-alone hybrid solar–wind power generation systems

Solar and wind energy systems are omnipresent, freely available, environmental friendly, and they are considered as promising power generating sources due to their availability and topological advantages for local power generations. Hybrid solar–wind energy systems, uses two renewable energy sources, allow improving the system efficiency and power reliability and reduce the energy storage requirements for stand-alone applications. The hybrid solar–wind systems are becoming popular in remote area power generation applications due to advancements in renewable energy technologies and substantial rise in prices of petroleum products. This paper is to review the current state of the simulation, optimization and control technologies for the stand-alone hybrid solar–wind energy systems with battery storage. It is found that continued research and development effort in this area is still needed for improving the systems’ performance, establishing techniques for accurately predicting their output and reliably integrating them with other renewable or conventional power generation sources.     

The database–modeling nexus in integrated assessment modeling of electric power generation

Integrated assessment models (IAMs) are playing an increasingly important role in long-run sustainability analysis. At their core is a set of global economic and environmental accounts which capture a complete set of inter-industry and inter-regional relationships in the global economy in a consistent manner. While much attention is focused on the raw data and parameterization required to expand or add sectoral detail to IAMs, only rarely is there discussion of how different matrix balancing methods (i.e. translating disparate raw data sources into the consistent database) affect modeling results. This article offers an in-depth look into the database–modeling nexus in IAMs, focusing on the electric power sector which is both a major source of CO₂ emissions and a critical vehicle for climate change mitigation. Comparisons of the prevailing matrix balancing algorithms show how the choice of database reconciliation methodology affects modeling results using policy-relevant simulations in the context of the electric power sector. The resulting insights can be applied to the disaggregation of other, technology rich sectors in the economy. We conclude that appropriate selection of database reconciliation methodologies can reduce the deviation between bottom-up and top-down modeling.     

Public–private partnerships for wind power generation: The Portuguese case

Today’s portfolio of energy production, based mostly on fossil fuels, and increasing energy consumption go against a sustainable vision for the world’s development. Governments are shifting their energy policies towards renewable, nonpollutant sources of energy, developing large investment plans to ensure an adequate response to energy demand growth while keeping the environmental impact within reasonable boundaries. As in many other infrastructure-related sectors, new models for the provision of these facilities, and services, are being developed. Over the past 20 years, highways, hospitals, social housing, airports and dams have been developed in close collaboration with the private sector, not only in a contractor–supplier relation but also in deeper partnerships where the private sector assumes a substantial responsibility in managing and running the business. These models are known as public–private partnerships (PPPs). This research will look at the Portuguese experience in the application of PPP arrangements in the energy sector, particularly as far as the development of wind power plants is concerned. The evaluation procedures for selecting the private partner, the contract structure and the risk-sharing agreement are some of the issues deserving special attention.     

The effect of using sun tracking systems on the voltage–current characteristics and power generation of flat plate photovoltaics

An experimental study was performed to investigate the effect of using different types of sun tracking systems on the voltage–current characteristics and electrical power generation at the output of flat plate photovoltaics (FPPV). Four electromechanical sun tracking systems, two axes, one axis vertical, one axis east–west and one axis north–south, were designed and constructed for the purpose of investigating the effect of tracking on the electrical values, current, voltage and power, according to the different loads (variable resistance). The above mentioned variables were measured at the output of the FPPV and compared with those on a fixed surface. The results indicated that the volt–ampere characteristics on the tracking surfaces were significantly greater than that on a fixed surface. There were increases of electrical power gain up to 43.87%, 37.53%, 34.43% and 15.69% for the two axes, east–west, vertical and north–south tracking, respectively, as compared with the fixed surface inclined 32° to the south in Amman, Jordan.     

The status of conventional world oil reserves—Hype or cause for concern?

The status of world oil reserves is a contentious issue, polarised between advocates of peak oil who believe production will soon decline, and major oil companies that say there is enough oil to last for decades.     

Optimal design and techno-economic analysis of a hybrid solar–wind power generation system

Solar energy and wind energy are the two most viable renewable energy resources in the world. Good compensation characters are usually found between solar energy and wind energy. This paper recommend an optimal design model for designing hybrid solar–wind systems employing battery banks for calculating the system optimum configurations and ensuring that the annualized cost of the systems is minimized while satisfying the custom required loss of power supply probability (LPSP). The five decision variables included in the optimization process are the PV module number, PV module slope angle, wind turbine number, wind turbine installation height and battery capacity. The proposed method has been applied to design a hybrid system to supply power for a telecommunication relay station along south-east coast of China. The research and project monitoring results of the hybrid project were reported, good complementary characteristics between the solar and wind energy were found, and the hybrid system turned out to be able to perform very well as expected throughout the year with the battery over-discharge situations seldom occurred.     

Thermodynamic optimization of biomass gasification for decentralized power generation and Fischer–Tropsch synthesis

In recent years, biomass gasification has emerged as a viable option for decentralized power generation, especially in developing countries. Another potential use of producer gas from biomass gasification is in terms of feedstock for Fischer–Tropsch (FT) synthesis – a process for manufacture of synthetic gasoline and diesel. This paper reports optimization of biomass gasification process for these two applications. Using the non–stoichometric equilibrium model (SOLGASMIX), we have assessed the outcome of gasification process for different combinations of operating conditions. Four key parameters have been used for optimization, viz. biomass type (saw dust, rice husk, bamboo dust), air or equivalence ratio (AR = 0, 0.2, 0.4, 0.6, 0.8 and 1), temperature of gasification (T = 400, 500, 600, 700, 800, 900 and 1000 °C), and gasification medium (air, air–steam 10% mole/mole mixture, air–steam 30%mole/mole mixture). Performance of the gasification process has been assessed with four measures, viz. molar content of H₂ and CO in the producer gas, H₂/CO molar ratio, LHV of producer gas and overall efficiency of gasifier. The optimum sets of operating conditions for gasifier for FT synthesis are: AR = 0.2–0.4, Temp = 800–1000 °C, and gasification medium as air. The optimum sets of operating conditions for decentralized power generation are: AR = 0.3–0.4, Temp = 700–800 °C with gasification medium being air. The thermodynamic model and methodology presented in this work also presents a general framework, which could be extended for optimization of biomass gasification for any other application.     

Exergy analysis and investigation for various feed water heaters of direct steam generation solar–thermal power plant

The energy and exergy analysis has been carried out for the different components of a proposed conceptual direct steam generation (DSG) solar–thermal power plant (STPP). It has been found that the maximum energy loss is in the condenser followed by solar collector field. The maximum exergy loss is in the solar collector field while in other plant components it is small. The possibilities to further improve the plant efficiency are identified and exploited. For minimum exergy loss in receiver the inlet temperature of water to the receiver, which is governed by the number of feed water heaters (FWHs), bleed pressure and mass fraction of bleed steam, must be optimum. The only one FWH has been proposed in conceptual DSG STPP. In order to evaluate the optimum bleed pressure and mass fraction of bleed steam to maximize the STPP efficiency, the investigations are carried out for various bleed pressure and mass fractions of bleed steam of proposed conceptual DSG STPP having one FWH. The investigations for bleed pressure and mass fraction of bleed steam are also carried out by incorporating two and three FWHs. It has been found that there will be significant improvement in efficiency by using three FWHs and further gain in efficiency is possible by making provision for more FWHs.     

Green economy and green jobs: Myth or reality? The case of China’s power generation sector

This paper investigates the relationship between the green economy and green jobs in China through the following question: Can the current GHG mitigation policies in China’s power generation sector bring more jobs to China? Using both analytical and input–output models this paper analyzes the direct and indirect employment impacts of two main mitigation policies in the power generation sector. This paper proves that the above-mentioned question is not simple. Mitigation policies in China’s power generation sector from 2006 to 2009 caused a total of 44 thousand net jobs losses. However, as the share of renewable energy that has an indirect employment impacts increased in 2010, the policies from 2006 to 2010 actually resulted in 472 thousand net job gains. This paper asserts that to ensure the co-existence of green economy and green jobs in China’s power generation sector, policy makers should further promote solar PV, biomass and wind technologies. In 2010, for every one percent increase in the share of solar PV generation there could be a 0.68% increase in total employment in China, larger than any other power generation technology. Finally, this paper argues that a matching educational system and personnel structure is also needed.     

The impact of the EU ETS on the sectoral innovation system for power generation technologies – Findings for Germany

This paper provides an overview of early changes in the sectoral innovation system for power generation technologies which have been triggered by the European Emission Trading System (EU ETS). Based on a broad definition of the sector, our research analyses the impact of the EU ETS on the four building blocks ‘knowledge and technologies’, ‘actors and networks’, ‘institutions’, and ‘demand’ by combining two streams of literature, namely systems of innovation and environmental economics. Our analysis for Germany is based on 42 exploratory interviews with experts in the field of the EU ETS, the power sector, and technological innovation. We find that the EU ETS mainly affects the rate and direction of technological change of power generation technologies within the large-scale, coal-based power generation technological regime, to which carbon capture technologies are added as a new technological trajectory. While this impact can be interpreted as the defensive behaviour of incumbents, the observed changes should not be underestimated. We argue that the EU ETS’ impact on corporate CO₂ culture and routines may prepare the ground for the transition to a low-carbon sectoral innovation system for power generation technologies.     

The development and application practice of wind–solar energy hybrid generation systems in China

China is the largest developing country in the world. At present, more and more energy demand gives immense pressure to Chinese government. The inappropriate energy structure must be improved by Chinese government in order to achieve the sustainable development of economy and society. Development and application of renewable energy, such as wind energy, solar energy, biomass energy, etc., have been regarded by the government and the local people in the past 10 years, and more and more actual examples have been established, which are supported by government and plants in China. It is well known that there are abundant wind and solar resources in China. This paper presents the distribution zone and development and application practice status in China. However, a common drawback is existing in the stand-alone wind energy and solar energy generating power system, which is the unpredictable output electric power, and the output power depends on the unpredictable weather and climatic changes. Fortunately, the wind–solar hybrid generation system can partially overcome the problems. The conventional structure and key technology of stand-alone wind–solar hybrid generating system, the current status and outlook of wind–solar hybrid energy system are presented in the paper, for example, the city road lighting system, distributed generation, photovoltaic (PV) water pumping for irrigation, etc. At the end, the policies and laws of China central government and local governments are described, and the development barriers and recommendations are introduced.     

A real options–based CCS investment evaluation model: Case study of China’s power generation sector

This paper establishes a carbon capture and storage (CCS) investment evaluation model based on real options theory considering uncertainties from the existing thermal power generating cost, carbon price, thermal power with CCS generating cost, and investment in CCS technology deployment. The model aims to evaluate the value of the cost saving effect and amount of CO₂ emission reduction through investing in newly-built thermal power with CCS technology to replace existing thermal power in a given period from the perspective of power generation enterprises. The model is solved by the Least Squares Monte Carlo (LSM) method. Since the model could be used as a policy analysis tool, China is taken as a case study to evaluate the effects of regulations on CCS investment through scenario analysis. The findings show that the current investment risk of CCS is high, climate policy having the greatest impact on CCS development. Thus, there is an important trade off for policy makers between reducing greenhouse gas emissions and protecting the interests of power generation enterprises. The research presented would be useful for CCS technology evaluation and related policy-making.     

The three-dimensional simulation and optimization of an integrated power system for reformer–PrOx–fuel cell modeling

The present study is aimed at integrating a power system for reformer, PrOx and PEM fuel cells using a simulation model. A three-dimensional numerical model is established for predicting the effects of channel patterns and the inlet and outlet manifold configuration with a fixed inlet flow rate on a reformer. Distributions of velocity, gases concentrations and current density are predicted, and the methanol conversion ratios are evaluated as well. In addition, the mole fraction of CO is contained and removed in the reformer and PrOx reactions, respectively. The solution model is used to improve the design of both the micro reformer and the fuel cell. Results showed that a CO mole fraction can be decreased through the PrOx reaction effectively; furthermore, the methanol conversion ratio and the concentration of hydrogen can be improved from 83% to 99% and from 67.11% to 74.4%, respectively. Additionally, the relative standard deviations of velocity in channels are decreased from 58.68% to 0.048%, according to the manifold configuration design; from the point of view of a fuel cell, high fuel usage and current density are obtained using a z-serpentine channel pattern. The current density is increased by 184% on the basis of inlet flow rate for a steam reformer from Design 1 to Design 2.     

Wind power and photovoltaic power: How to improve the accommodation capability of renewable electricity generation in China?

China's wind curtailment and photovoltaic curtailment was one of the prominent issues in 2014, and the renewable curtailment worsened in 2015. With the rapid growth of renewables, the phenomenon of the insufficiency in renewable accommodation capability is becoming more and more serious in 2016. In that case, the problem of the insufficient accommodation capability is pointed out by analyzing China's development requirements. The renewable power generation scale, the renewable power consumption, and the restrictions on the renewable electricity generation are discussed from the China's market perspective. Meanwhile, the legal environment, the planning requirement, the institutional setting, and the policy tools are introduced from the perspective of governmental regulation. An empirical analysis, a cause analysis and a trend analysis are illustrated before explaining the problem of renewable curtailment and proposing a solution for enhancing the accommodation capability. According to the analysis results, the solution for addressing the wind curtailment and PV curtailment is offered with respect to the technology, the institution, the legislation, and the political aspect. Through the research, the research conclusions are drew finally and the corresponding policy recommendations are put forward.     

Production of biodiesel at small-scale (10 L) for local power generation

The transesterification reaction of two different types of raw materials, a refined cooking oil and a used cooking sample, was performed at small scale (10 L) at the constant temperature of 65 °C. The effects of several reaction parameters, such as KOH wt% with respect to the oil weight, methanol/oil molar ratio and reaction time, were investigated. Biodiesel yields as good as 97.5 and 93.2% were achieved for the refined and the cooking oils, respectively, in the following conditions: 1.2 wt% of KOH as catalyst, a methanol/oil molar ratio of 6:1 and reaction time of 60 min.The properties of the biodiesel obtained starting from the used cooking oil are as good as those of the biodiesels obeying the European standards. The resulting product was used in a diesel electricity generator engine, which operated in real conditions. The results showed that biodiesel combustion leads to higher concentration of CO and to a lower emission of NO_x as compared to a petrodiesel-fueled engine. An optimization of the operating parameters of the engine would guarantee lower CO emissions in conformity with the regulation.     

Impacts of a Japan–South Korea power system interconnection on the competitiveness of electric power companies according to power exchange prices

In many regions, international power system interconnections provide economic, energy-security, environmental, and technical benefits. In contrast, such interconnections remain scarce in Northeast Asia. In 2016, after approving a joint memorandum of understanding between major electric power companies from China, Japan, South Korea, and Russia, related initiatives regained momentum in the region. Nevertheless, the corresponding developments in Japan remain limited, mainly owing to the lack of involvement of Japanese electric power companies. This study represents a pioneering attempt to provide an economic assessment based on power exchange prices of a power system interconnection between Japan and South Korea regarding the competitiveness of electric power companies in terms of competitive business segments and strategic consequences. We found that although the position of Japanese generators may slightly deteriorate, that of the supply segment would substantially improve, thus suggesting that more opportunities than threats are derived from the interconnection. This promising outcome may foster the adoption of an interconnection with South Korea considering the positive economic and business perspectives in Japan. Furthermore, realizing the interconnection may improve the energy security and air quality in the region.     

Iron incorporated Ni–ZrO2 catalysts for electric power generation from methane

On the purpose to perform as functional layer of SOFCs operating on methane fuel, NiFe–ZrO₂ alloy catalysts have been synthesized and investigated for methane partial oxidation reactions. Ni₄Fe₁–ZrO₂ shows catalytic activity comparable to that of Ni–ZrO₂ and superior to other Fe-containing catalysts. In addition, O₂-TPO analysis indicates iron is also prone to coke formation; as a result, most of NiFe–ZrO₂ catalysts do not show improved coking resistance than Ni–ZrO₂. Anyway, Ni₄Fe₁–ZrO₂ (Ni:Fe = 4:1 by weight) prepared by glycine-nitrate process shows somewhat less carbon deposition than the others. However, Raman spectroscopy demonstrates that the addition of Fe does reduce the graphitization degree of the deposited carbon, suggesting the easier elimination of carbon once it is deposited over the catalyst. Ni₄Fe₁–ZrO₂ has an excellent long-term stability for partial oxidation of methane reaction at 850 °C. A solid oxide fuel cell with conventional nickel cermet anode and Ni₄Fe₁–ZrO₂ functional layer is operated on CH₄–O₂ gas mixture to yield a peak power density of 1038 mW cm⁻² at 850 °C, which is comparable to that of hydrogen fuel. In summary, the Ni₄Fe₁–ZrO₂ catalyst is potential catalyst as functional layer for solid-oxide fuel cells operating on methane fuel.     

Impacts of renewable energy regulations on the structure of power generation in China – A critical analysis

China is facing a number of energy-related challenges such as shortage of electricity supply and environmental pollution. The Government recognized the important role the renewable energy plays in the power generation structure. As a result, a series of supporting policies, laws and regulations have been issued to boost the renewable energies in China. This paper provides a critical analysis of the policy framework for the renewable energy in China and its impacts on the power generation structure. The relevant policy documents, including the most recent government work report delivered by Premier Wen Jia-bao during the Third Session of the 11th National People’s Congress (NPC) in March 2010 are analyzed. The patterns of renewable energy developments are found strongly correlated with the promulgation of relevant policies.