Comparative analyses of seven technologies to facilitate the integration of fluctuating renewable energy sources

An analysis of seven different technologies is presented. The technologies integrate fluctuating renewable energy sources (RES) such as wind power production into the electricity supply, and the Danish energy system is used as a case. Comprehensive hour-by-hour energy system analyses are conducted of a complete system meeting electricity, heat and transport demands, and including RES, power plants, and combined heat and power production (CHP) for district heating and transport technologies. In conclusion, the most fuel-efficient and least-cost technologies are identified through energy system and feasibility analyses. Large-scale heat pumps prove to be especially promising as they efficiently reduce the production of excess electricity. Flexible electricity demand and electric boilers are low-cost solutions, but their improvement of fuel efficiency is rather limited. Battery electric vehicles constitute the most promising transport integration technology compared with hydrogen fuel cell vehicles (HFCVs). The costs of integrating RES with electrolysers for HFCVs, CHP and micro fuel cell CHP are reduced significantly with more than 50% of RES.     

Role of hydrogen in future North European power system in 2060

The Balmorel model has been used to calculate the economic optimal energy system configuration for the Scandinavian countries and Germany in 2060 assuming a nearly 100% coverage of the energy demands in the power, heat and transport sector with renewable energy sources. Different assumptions about the future success of fuel cell technologies have been investigated as well as different electricity and heat demand assumptions. The variability of wind power production was handled by varying the hydropower production and the production on CHP plants using biomass, by power transmission, by varying the heat production in heat pumps and electric heat boilers, and by varying the production of hydrogen in electrolysis plants in combination with hydrogen storage. Investment in hydrogen storage capacity corresponded to 1.2% of annual wind power production in the scenarios without a hydrogen demand from the transport sector, and approximately 4% in the scenarios with a hydrogen demand from the transport sector. Even the scenarios without a demand for hydrogen from the transport sector saw investments in hydrogen storage due to the need for flexibility provided by the ability to store hydrogen. The storage capacities of the electricity storages provided by plug-in hybrid electric vehicles were too small to make hydrogen storage superfluous.     

地源热泵运行经济性分析

根据北方寒冷地区冬天室外温度偏低的特点,提出利用地源热泵供暖。地源热泵存在三种驱动方式：电动机、柴油机、燃气机。三种辅助供暖热源：电锅炉、燃油锅炉、燃气锅炉。本文对其一次能源利用率和燃料价格变动时,系统运行经济性进行比较分析,得出燃气热泵的供暖费用比锅炉房集中供热的费用要高6％;电动热泵的供暖费用比锅炉房集中供热费高40％;柴油机热泵的供暖费用比锅炉房集中供暖高出57％。     

石油仓储企业热泵与燃油锅炉联合供热的探讨

针对目前石油仓储企业需要利用燃油锅炉产生蒸汽,对高凝点、高粘度油品进行保温的现状,通过分析燃油锅炉的热力系统,提出通过提升进入除氧器补充水的水温,从而减少热力除氧器消耗的蒸汽量以达到减少燃料油消耗量的思路。介绍热泵系统的特点和优势及其与燃油锅炉联合供热的方案,并通过实例阐明热泵与燃油锅炉联合供热的经济效益。     

Heating with wind: Economics of heat pumps and variable renewables

With the growth of wind and solar energy in electricity supply, the electrification of space and water heating is becoming a promising decarbonization option. In turn, such electrification may help the power system integration of variable renewables, for two reasons: thermal storage could provide low-cost flexibility, and heat demand is seasonally correlated with wind power. However, temporal fluctuations in heat demand may also imply new challenges for the power system. This study assesses the economic characteristics of electric heat pumps and wind energy and studies their interaction on wholesale electricity markets. Using a numerical electricity market model, we estimate the economic value of wind energy and the economic cost of powering heat pumps. We find that, just as expanding wind energy depresses its €/MWh_el value, adopting heat pumps increases their €/MWh_el cost. This rise can be mitigated by synergistic effects with wind power, “system-friendly” heat pump technology, and thermal storage. Furthermore, heat pumps raise the wind market value, but this effect vanishes if accounting for the additional wind energy needed to serve the heat pump load. Thermal storage facilitates the system integration of wind power but competes with other flexibility options. For an efficient adoption of heat pumps and thermal storage, we argue that retail tariffs for heat pump customers should reflect their underlying economic cost.     

Coproduction of district heat and electricity or biomotor fuels

The operation of a district heating system depends on the heat load demand, which varies throughout the year. In this paper, we analyze the coproduction of district heat and electricity or biomotor fuels. We demonstrate how three different taxation scenarios and two crude oil price levels influence the selection of production units to minimize the district heat production cost and calculate the resulting primary energy use. Our analysis is based on the annual measured heat load of a district heating system. The minimum-cost district heat production system comprises different production units that meet the district heat demand and simultaneously minimize the district heat production cost. First, we optimize the cost of a district heat production system based on the cogeneration of electricity and heat with and without biomass integrated gasification combined-cycle technology. We considered cogenerated electricity as a byproduct with the value of that produced by a condensing power plant. Next, we integrate and optimize different biomotor fuel production units into the district heat production system by considering biomotor fuels as byproducts that can substitute for fossil motor fuels. We demonstrate that in district heating systems, the strengthening of environmental taxation reduces the dependence on fossil fuels. However, increases in environmental taxation and the crude oil price do not necessarily influence the production cost of district heat as long as biomass price is not driven by policy measures. Biomotor fuel production in a district heating system is typically not cost-efficient. The biomotor fuels produced from the district heating system have to compete with those from standalone biomotor fuel plants and also with its fossil-based counterparts. This is also true for high oil prices. A carbon tax on fossil CO₂ emissions based on social cost damage will increase the competitiveness of biomass-based combined heat and power plants, especially for BIGCC technology with its high electricity-to-heat ratio.     

燃煤电厂主要节能降耗措施的经济性分析

面对节能发电调度、竞价上网、煤价上涨、环保治理等问题,燃煤电厂不仅压力大而且社会责任大。如何减少生产环节中各项损失,对低效高耗的主辅机进行技术改造,挖潜增效是关键。珠江电厂通过对锅炉运行进行优化调整,改造回转式空气预热器,锅炉采用等离子点火节油技术;对汽机运行进行优化调整,对汽轮机通流部分进行技术改造,凝结水泵采用变频调速节能技术。实施节能降耗措施后,电厂机组整体经济性明显提高,供电煤耗下降,取得了较好的经济效益和社会效益。     

Co-firing—A strategy for bioenergy in Poland?

Biomass provides the largest reduction of carbon dioxide (CO₂) emission when it replaces coal, which is the dominating fuel in heat and electricity production in Poland. One means of replacing coal with biomass is to co-fire biofuels in an existing coal-fired boiler. This paper presents an analysis of the strengths and weaknesses of co-firing biofuels in Poland with respect to technical, environmental, economical and strategic considerations. This analysis shows that co-firing is technically and economically the most realistic option for using biofuels in the large pulverized fuel (PF) boilers in Poland. However, from an environmental perspective, co-firing of biofuels in large combined heat and power (CHP) plants and power plants provides only a small reduction in sulphur dioxide (SO₂) emission per unit biofuel, since these plants usually apply some form of desulphurization technology. In order to maximize the SO₂ emission reduction, biofuels should be used in district heating plants. However, co-fired combustion plants can handle disruptions in biofuel supply and are insensitive to moderate changes in fuel prices, which makes them suitable utilizers of biofuels from perennial energy crops. Co-firing could therefore play an important role in stimulating perennial crop production.     

Role of energy efficiency standards in reducing CO2 emissions in Germany: An assessment with TIMES

Energy efficiency is widely viewed as an important element of energy and environmental policy. Applying the TIMES model, this paper examines the impacts of additional efficiency improvement measures (as prescribed by the ACROPOLIS project) over the baseline, at the level of individual sectors level as well as in a combined implementation, on the German energy system in terms of energy savings, technological development, emissions and costs. Implementing efficiency measures in all sectors together, CO₂ reduction is possible through substitution of conventional gas or oil boilers by condensing gas boilers especially in single family houses, shifting from petrol to diesel vehicles in private transport, increased use of electric vehicles, gas combined cycle power plants and CHP (combined heat and power production) etc. At a sectoral level, the residential sector offers double benefits of CO₂ reduction and cost savings. In the transport sector, on the other hand, CO₂ reduction is the most expensive, using bio-fuels and methanol to achieve the efficiency targets.     

The USA geothermal country update

Geothermal energy is used for electric power generation and direct utilization in the United States. The present installed capacity (gross) for electric power generation is about 2020 MWe, with 1902 MWe net delivering power to the grid, producing approximately 16,000 GWh per year for a 96% capacity factor. Geothermal electric power plants are located in California, Nevada, Utah and Hawaii. The two largest concentrations of plants are at The Geysers in northern California and the Imperial Valley in southern California. The latest development at The Geysers, due to recent declines in steam output, is the injection of recycled wastewater from two communities into the reservoir, which has at present permitted the recovery of 70 MWe of power generation. The direct utilization of geothermal energy includes the heating of pools and spas, greenhouses and aquaculture facilities, space heating and district heating, snow melting, agricultural drying, industrial applications and ground-source heat pumps. The installed capacity is about 4350 MWt and the annual energy use is 22,250 TJ, or 6181 GWh. The largest application is that of ground-source (geothermal) heat pumps (60% of the energy use), and the largest direct-use is that of aquaculture pond and raceway water heating. Direct utilization is increasing at about 6% per year, whereas electric power plant development is almost static. The energy savings from electric power generation, direct uses and ground-source heat pumps amount to 6.6 million tonnes of equivalent fuel oil per year and represents a reduction in air pollution of 5.8 million tonnes of carbon annually (compared to fuel oil).     

延迟焦化装置的能耗分析及节能优化实践

中国海油惠州炼油分公司420× 104t/a延迟焦化装置通过停用解吸塔上重沸器3.5MPa蒸汽、停用柴油汽提塔1.0MPa汽提蒸汽、降低循环比、采用先进控制(APC)提高加热炉热效率、降低高压水泵和罐区减渣原料泵电耗、提高水的回用率、加大装置处理量等工艺优化措施,装置综合能耗比设计能耗39.03kg标油/t原料降低3kg标油/t原料.为了进一步降低装置能耗,达到国内其他先进装置的能耗水平,该装置在2011年利用检修时机,通过加热炉节能改造降低排烟温度、利用柴油低温热发生0.45MPa蒸汽、焦化富气压缩机叶轮更换、焦炭塔区特阀汽封线改造等节能改造措施.加热炉热效率由89％提高至91.5％,节约3.5MPa蒸汽用量约6.5t/h,同时减少了燃料气、蒸汽和电的消耗,使装置能耗总体降低3.16kg标油/t原料.装置节能改造每年可增加4000万元的经济效益.     

计及弃风的“电气互补-冷热联供”模式研究

针对弃风严重以及传统供暖方式存在难以“热电解耦”的问题,提出一种将蓄热式电锅炉、燃气锅炉、吸收式制冷机相结合的“电气互补-冷热联供”弃风消纳模式。首先,根据弃风和冷热负荷特性建立“电气互补-冷热联供”模型;然后,考虑供暖与制冷成本,构建“电气互补-冷热联供”经济性模型;最后,通过算例分析与传统“燃气锅炉-空调”供暖制冷模型的经济性进行对比。结果表明：所提模式可在消纳弃风的同时减少碳排放量,达到提升系统收益的目的。     

Optimization of diesel engine design for combined heat and power

Prime movers and boilers have traditionally been optimized independently to convert fuel to power and heat, respectively. the design of devices to optimize the simultaneous production of heat and power has been neglected. This paper considers the optimization in this mode of diesel engines and concludes that simple modifications of design could increase the heat recoverable in the exhaust by the equivalent of 10 per cent of the fuel input. In monetary terms this is equivalent to about a 4 per cent increase in brake efficiency, recent improvements in brake efficiency of this magnitude have taken ten or fifteen years of continuous research and development. the changes now proposed would increase thermal loading and some development might be necessary.     

Wind energy status in electrical energy production of Turkey

Main electrical energy sources of Turkey are thermal (lignite, natural gas, coal, fuel oil, etc.) and hydraulic. Most of the thermal sources are derived from natural gas. Turkey imports natural gas; therefore, decreasing usage of natural gas is very important for both economical and environmental aspects. Because of disadvantages of fossil fuels, renewable energy sources are getting importance for sustainable energy development and environmental protection. Among the renewable sources, Turkey has very high wind energy potential. However the installed wind power capacity is only 0.22% of total economical wind potential. In this study, Turkey's installed electric power capacity, electric energy production is investigated and also Turkey current wind energy status is examined.     

Influence of massive heat‐pump introduction on the electricity‐generation mix and the GHG effect—Belgian case study

To evaluate the environmental impact of massive heat‐pump introduction on greenhouse gas (GHG) emissions, dynamic simulations of the overall electricity‐generation system have been performed for Belgium. The simulations are carried out with Promix, a tool that models the overall electricity‐generation system. For comparison, three heating devices are considered, namely conventional boilers, heat pumps and electrical resistance heating. The introduction of electric heating at the expense of classic heating increases the demand for electricity and generates a shift of emissions from fossil‐fuel heating systems to electrical power plants. The replaced classic fossil‐fuel‐fired heating represents emissions of about 300 kton. With regard to the heat‐pump scenarios, both direct heat‐pump heating with a coefficient of performance (COP) of 2.5 and accumulation heat‐pump heating with a COP of 5 are investigated. The results of the simulations reveal that the massive introduction of heat‐pump heating is favourable to the environment. In Belgium, the largest reductions in GHG emissions occur with heat pumps for direct heating, combined with newly commissioned combined cycle (CC) gas‐fired plants or with accumulation heat‐pump heating. These scenarios bring about overall GHG emission reductions of approximately 200 kton compared with the reference case with conventional heating for the years 2000 and 2010. The amount of additional electricity‐related emissions depends on the considered heating device. In 2010, the scenario with accumulation heat pumps results in an overall decrease of Belgian GHG emissions by 0.15% compared with the reference scenario. The expansion of the electricity‐generation system with new CC plants has an important favourable impact on GHGs as well. In most cases, the combination of higher electricity demand and the construction of new gas‐fired CC plants will lead to lower overall GHG emissions. Copyright © 2007 John Wiley & Sons, Ltd.     

Cost minimization for a local utility through CHP,heat storage and load management

The energy-system optimization model MODEST is described, especially heat storage and electricity load management. Linear programming is used for minimization of capital and operation costs. MODEST may be used to find the optimal investments and when to make them. The period under study can be divided into several linked subperiods which may consist of an arbitrary number of years. MODEST is here applied to a municipal electricity and district-heating system during three five-year periods. Each year is divided into three seasons. Demand peaks, as well as weekly and diurnal variations of, for example, costs are considered. The electricity demand is divided into the three sectors households, industries, and service. The electricity demand may be reduced by energy conservation, replacement of electric heating and load management. The profitability of load management, as well as cogeneration with and without heat storage at different prices of purchased power is calculated. At traditional Swedish electricity prices, the local utility should build a woodchips-fired steam-cycle CHP (combined heat and power) plant. Consumers would find it beneficial to reduce their electricity use by conservation and switching from electric heating to oil and biofuel. If just marginal power production costs are paid, the utility should introduce biomass-fired heat-only boilers instead. Electricity conservation is smaller at these lower prices. Load management is mainly profitable at the first price scheme which includes output-power-related charges. The heat storage should be used threefold: to cover demand peaks, as well as to enable increased CHP output when it is limited by the heat demand or to run heat pumps at cheap night electricity instead of in the daytime. © 1998 John Wiley & Sons, Ltd.     

Efficiency of wind energy utilization for electricity and heat supply in northern regions of Russia

The paper describes a method for assessing the economic efficiency of wind energy utilization within small autonomous systems for both electricity and heat supply. The obtained analytical solution allows the simplification of calculations in comparison to the methods of chronological modeling and numerical algorithms for application of the convolution method.The economic effect of using wind turbines is assessed for remote communities of the extreme north of Russia with a maximum electric load of 200 kW for the turbines with a capacity from 30 to 800 kW, taking into account variation of possible growth rates of fossil fuel price for back-up sources of electric and heat energy.The calculations performed have shown that at the existing and forecasted rates of fuel price escalation, the economic effect of using surplus (as a result of mismatch in production and consumption) electric energy for heat supply will be 1.5–2.0 times higher. In this case, the optimal capacity of wind turbines can substantially exceed electric load power (two to four times).     

采暖供热系统的应用浅析

随着环保要求的提高和电力峰谷差的拉大,燃煤锅炉采暖受到严格限制,而其他采暖形式,如燃气采暖、电动采暖和蓄热的应用,开始受到关注。本文对热电联产、燃气锅炉、电炉、电动热泵以及蓄热的应用前景做初步的分析与探讨     

Distributed multi-generation: A comprehensive view

The recent development of efficient thermal prime movers for distributed generation is changing the focus of the production of electricity from large centralized power plants to local generation units scattered over the territory. The scientific community is addressing the analysis and planning of distributed energy resources with widespread approaches, taking into account technical, environmental, economic and social issues. The coupling of cogeneration systems to absorption/electric chillers or heat pumps, as well as the interactions with renewable sources, allow for setting up multi-generation systems for combined local production of different energy vectors such as electricity, heat (at different enthalpy levels), cooling power, hydrogen, various chemical substances, and so forth. Adoption of composite multi-generation systems may lead to significant benefits in terms of higher energy efficiency, reduced CO₂ emissions, and enhanced economy. In this light, a key direction for improving the characteristics of the local energy production concerns the integration of the concepts of distributed energy resources and combined production of different energy vectors into a comprehensive distributed multi-generation (DMG) framework that entails various approaches to energy planning currently available in the literature. This paper outlines the main aspects of the DMG framework, illustrating its characteristics and summarizing the relevant DMG structures. The presentation is backed by an extended review of the most recent journal publications and reports.     

A new concept for integrating a thermal air power tube with solar energy and alternative, waste heat energy sources and large natural or man-made, geo-physical phenomenon

A method for power generation combining a solar concentration system and a pneumatic power tube system in a large open pit is described. Solar energy is concentrated by a plurality of heliostat mirrors placed along the embankment of the pit, which tends to be spherical in contour. The pneumatic tubes recover waste heat energy from the solar Rankine power cycle system and from a variety of sources that originate from or are in close proximity to the very deep, man-made open-pit mine or from other naturally occurring geo-physical chasms. The man-made or naturally formed chasms provide structural support for the pneumatic power tubes. The air in the tubes is heated by the recovered waste energy, and in so doing, its density is sufficiently reduced so as to produce air drafts from which mechanical power can be recovered from wind turbines and converted into electrical power by suitable electric generators. The deep chasms can be from a man-made phenomenon such as commissioned, open-pit mines or from naturally occurring fissures in the earth. The waste heat can be from solar energy, ground source energy or products of combustion from waste products that are to be mitigated or destroyed. The concept is novel in its integration of a solar powered heat engine with recoverable waste heat via the proposed pneumatic power tube as well as in the means of structural support that the geo-physical phenomenon provides and the modularity (for ease in manufacturing and installation) that makes the pneumatic power tube economically viable. The complete system uses state-of-the art wind turbine power recovery, solar reflective surfaces for solar energy collection, heat pipe arrays for ground source heat recovery, and air diffuser subsystems for enhanced wind turbine efficiency.