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Abstract: Denmark has more than 10 years’ of experience with a wind share of approximately 20 per cent. During these 10 years, electricity markets have been subject to developments with a key focus on integrating wind power as well as trading electricity with neighbouring countries. This article introduces a methodology to analyse and understand the current market integration of wind power and concludes that the majority of Danish wind power in the period 2004–2008 was used to meet the domestic demand. Based on a physical analysis, at least 63 per cent of Danish wind power was used domestically in 2008. To analyse the remaining 37 per cent, we must apply a market model to identify cause–effect relationships. The Danish case does not illustrate any upper limit for wind power integration, as also illustrated by Danish political targets to integrate 50 per cent by 2020. In recent years, Danish wind power has been financed solely by the electricity consumers, while maintaining production prices below the EU average. The net influence from wind power has been as low as 1–3 per cent of the consumer price. [Copyright &y& Elsevier]

Abstract: This paper presents the influence of different regulation strategies on wind energy integration into the existing energy system of Jiangsu. The ability of wind integration is defined in terms of the ability to avoid excess electricity production, to conserve primary energy consumption and to reduce CO2 emissions in the system. Firstly, a reference model of Jiangsu''s energy system is built using the energy system analysis tool EnergyPLAN based on the year 2009. The model results are then compared to actual values from 2009 to validate their accuracy. Based on the reference model, different regulations of Jiangsu''s energy system are compared and analyzed in the range of a wind input from 0% to 42% of the total electricity demand. It is concluded that operating power plants in a flexible way facilitates the promotion of more intermittent wind integration. [Copyright &y& Elsevier]

Abstract: This paper presents the ability of the existing Chinese energy system to integrate wind power and explores how the Chinese energy system needs to prepare itself in order to integrate more fluctuating renewable energy in the future. With this purpose in mind, a model of the Chinese energy system has been constructed by using EnergyPLAN based on the year 2007, which has then been used for investigating three issues. Firstly, the accuracy of the model itself has been examined and then the maximum feasible wind power penetration in the existing energy system has been identified. Finally, barriers have been discussed and suggestions proposed for the Chinese energy system to integrate large-scale renewable energy in the future. It is concluded that the model constructed by the use of EnergyPLAN can accurately simulate the Chinese energy system. Based on current regulations to secure grid stability, the maximum feasible wind power penetration in the existing Chinese energy system is approximately 26% from both technical and economic points of view. A fuel efficiency decrease occurred when increasing wind power penetration in the system, due to its rigid power supply structure and the task of securing grid stability, was left primarily to large coal-fired power plants. There are at least three possible solutions for the Chinese energy system to integrate large-scale fluctuating renewable energy in the long term: Redesigning the regulations to secure grid stability by means of diversifying the participants, such as including hydropower and CHP plants; integrating large-scale heat pumps combined with heat storage devices to satisfy district heat demands and developing electric vehicles to promote off peak electricity utilisation. [Copyright &y& Elsevier]

Future sustainable energy systems call for the introduction of integrated storage technologies. One of these technologies is compressed air energy storage (CAES). In Denmark at present, wind power meets 20% and combined heat and power production (CHP) meets 50% of the electricity demand. Based on these figures, the paper assesses the value of integrating CAES into future sustainable energy systems with even higher shares of fluctuating renewable energy sources. The evaluation is made on the basis of detailed energy system analyses in which the supply of complete national energy systems is calculated hour by hour in relation to the demands during a year. The Danish case is evaluated in a system-economic perspective by comparing the economic benefits achieved by improving the integration of wind power to the costs of the CAES technology. The result is compared to various other storage options. Furthermore, a business-economic evaluation is done by calculating the potential income of the CAES technology from both spot markets and regulating power markets. The evaluation includes both historical hour by hour prices during a 7-year period on the Nordic Nord Pool market as well as expected future price variations. The conclusion is that even in energy systems with very high shares of wind power and CHP, neither the historical nor the expected future price variations on the spot market alone can justify the investment in CAES systems. Other storage technology options are significantly more feasible. CAES may operate both on the spot market and the regulating power market, which indicates potential feasibility. However, such strategy is highly risky because of the small extent of the regulating power market and if CAES is to become feasible it will depend on incomes from auxiliary services. [Copyright &y& Elsevier]

Abstract: In 2005, wind power supplied 19% of the 36TWh annual electricity demand in Denmark, while 50% was produced at combined heat-and-power plants (CHP). The installed wind-turbine capacity in Western Denmark exceeds the local demand at certain points in time. So far, excess production has been exported to neighbouring countries. However, plans to expand wind power both in Denmark and in its neighbouring countries could restrain the export option and create transmission congestion challenges. This results in a need to increase the flexibility of the local electricity-system. Compressed-Air Energy-Storage (CAES) has been proposed as a potential solution for levelling fluctuating wind-power production and maintaining a system balance. This paper analyses the energy-balance effects of adding CAES to the Western Danish energy-system. Results show that even with an unlimited CAES plant capacity, excess power production is not eliminated because of the high percentage of CHP production. The optimal wind-power penetration for maximum CAES operation is found to be around 55%. The minimum storage size for CAES to fully eliminate condensing power plants operation in the optimized system is over 500GWh, which corresponds to a cavern volume of around 234Mm3 at an average pressure of 60 bar. Such a storage size would be technically and economically unfeasible. The analysis, however, did not include the potential role of a CAES plant in regulating the power services. [Copyright &y& Elsevier]

Abstract: The paper presents the ability of different energy systems and regulation strategies to integrate wind power. The ability is expressed by the following three factors: the degree of electricity excess production caused by fluctuations in wind and Combined Heat and Power (CHP) heat demands, the ability to utilise wind power to reduce CO2 emission in the system, and the ability to benefit from exchange of electricity on the market. Energy systems and regulation strategies are analysed in the range of a wind power input from 0 to 100% of the electricity demand. Based on the Danish energy system, in which 50% of the electricity demand is produced in CHP, a number of future energy systems with CO2 reduction potentials are analysed, i.e. systems with more CHP, systems using electricity for transportation (battery or hydrogen vehicles) and systems with fuel-cell technologies. For the present and such potential future energy systems different regulation strategies have been analysed, i.e. the inclusion of small CHP plants into the regulation task of electricity balancing and ancillary grid stability services and investments in electric heating, heat pumps and heat storage capacity. The results of the analyses make it possible to compare short-term and long-term potentials of different strategies of large-scale integration of wind power. [Copyright &y& Elsevier]

This article presents a methodology of showing the rate of integration of specific renewable energy sources (RESs) into the electricity supply system. The methodology is used on large-scale integration of wind, photo voltaic and wave power into a future Danish reference energy system. The possibility of integrating RES into the electricity supply is expressed in terms of the ability to avoid excess electricity production. The different sources are analysed in the range of an electricity production from 0 to 100% of the electricity demand. The excess production is found from detailed energy system analyses on the computer model EnergyPLAN. The analyses have taken into account that certain ancillary services are needed in order to secure the electricity supply system. The conclusion is that different patterns of each of the RES can be shown in terms of excess electricity diagrams. Such diagrams do not differ from one year to another, but do differ from one RES to another. [ABSTRACT FROM AUTHOR]

Both CHP (combined heat and power production) and wind power are important elements of Danish energy policy. Today, approximately 50% of both the Danish electricity and heat demand are produced in CHP and more than 15% of the electricity demand is produced by wind turbines. Both technologies are essential for the implementation of Danish climate change response objectives, and both technologies are intended for further expansion in the coming decade. Meanwhile, the integration of CHP and wind power is subject to fluctuations in electricity production. Wind turbines depend on the wind, and CHP depends on the heat demand. This article discusses and analyses two different national strategies for solving this problem. One strategy, which is the current official government policy known as the export strategy, proposes to take advantage of the Nordic and European markets for selling and buying electricity. In this case, surplus electricity from wind power and CHP simply will be sold to neighbouring countries. Another strategy, the self-supply strategy, runs the CHP units to meet both demand and the fluctuations in the wind scheduling. In this case, investments in heat storages are necessary and heat pumps have to be added to the CHP units. Based on official Danish energy policy and energy plans, this article quantifies the problem for the year 2015 in terms of the amount of surplus electricity, and investments in heat pumps, etc. needed to solve the problem are calculated. Based on these results between the two different strategies, the conclusion is that the self-supply strategy is recommended over the official export strategy. [Copyright &y& Elsevier]

Renewable energy has been prioritized in Danish energy policy since the early 1980s. This has led to the current situation where Denmark is one of the leading countries in the world in the field of wind energy utilization. The background for this success is a story about how a society can manage the development and diffusion of sustainable technologies so that they are simultaneously socially acceptable and environmentally benign. Consequently, this article describes the relationship between the organization of wind power and the protection of nature. The aim is to analyse which kinds of public planning and policy can promote wind power and nature protection in a situation where a conflict exists between these two issues. The discussion acknowledges that it has been a serious problem to balance these contrasting considerations. However, it also suggests that the problems seem solvable if technology development, the social organization relating to the use of the technology and proper planning are brought together to work in a spirit of local involvement. © 1998 John Wiley & Sons, Ltd. and ERP Environment [ABSTRACT FROM AUTHOR]

Local ownership models have proven to be an important way to avoid local resistance to onshore wind turbines. As wind power expands into onshore and nearshore wind farms, such ownership models become of increasing importance, while also undergoing further development. This paper uses the Choice Awareness theory to examine some of the barriers connected to the implementation of these new ownership models and presents recommendations to overcome such barriers. Choice Awareness addresses societal aspects (discourse, socioeconomics, and public regulation) mainly related to implementing alternatives to existing technologies. For the theory to be able to embrace the complexity of the transition of the energy system more holistically, we explore and specify the organizational dimension of choice-eliminating mechanisms. Based on the case of an NGO's attempt to bid for a tender for nearshore wind turbines, it is shown how the central administration prevents new innovative ownership models from entering the tender. A strong path dependency has led to a conscious or unconscious elimination of projects based on organizational structures that do not fit the definition of large energy companies. As a result of this, the paper makes three recommendations for policy changes with the aim to secure equal possibilities for actors involved in nearshore wind power tenders. [ABSTRACT FROM AUTHOR]

Highlights • Increasing variable renewable electricity sources has shown to lower market prices. • Researchers have investigated this effect using historical data electricity markets. • Here holistic energy system analyses are done with an energy system simulation tool. • The analyses are used to quantify the effect on a specific case. Abstract Variable renewable electricity sources have been shown to reduce wholesale electricity market prices. This is expected to reduce the incentive for investments in new electricity production capacity, and might even make these investments infeasible, if relying only on the income from trade on the current electricity market paradigms. In this paper, a novel approach for quantifying this effect in future energy systems is developed using a holistic energy system approach. The approach is applied to the case of Denmark in 2015, which is part of the Nordic and Baltic wholesale electricity market Nord Pool Spot. A holistic energy system model is created and verified according to both the Danish energy balance and the Nord Pool Spot system price in 2015. Using this verified model, the Nord Pool Spot system price is quantified at increasing amounts of onshore wind power, offshore wind power and photovoltaic in Denmark. It is found that regardless of which variable renewable electricity source is implemented, including a combination of the three, the Nord Pool Spot system price decreases as the amount of energy produced by these sources increases, and this effect occurs immediately as more is introduced. [ABSTRACT FROM AUTHOR]

Abstract: Renewable energy is one of the possible solutions when addressing climate change. Today, large-scale renewable energy integration needs to include the experience to balance the discrepancy between electricity demand and supply. The electrification of transportation may have the potential to deal with this imbalance and to reduce its high dependence on oil production. For this reason, it is interesting to analyse the extent to which transport electrification can further the renewable energy integration. This paper quantifies this issue in Inner Mongolia, where the share of wind power in the electricity supply was 6.5% in 2009 and which has the plan to develop large-scale wind power. The results show that electric vehicles (EVs) have the ability to balance the electricity demand and supply and to further the wind power integration. In the best case, the energy system with EV can increase wind power integration by 8%. The application of EVs benefits from saving both energy system cost and fuel cost. However, the negative consequences of decreasing energy system efficiency and increasing the CO2 emission should be noted when applying the hydrogen fuel cell vehicle (HFCV). The results also indicate that developing renewable energy is crucial for transportation electrification. [Copyright &y& Elsevier]

Abstract: Significant installations of individual heat pumps are expected in future energy systems due to their economic competitiveness. This case study of the Danish energy system in 2020 with 50% wind power shows that individual heat pumps and heat storages can contribute to the integration of wind power. Heat accumulation tanks and passive heat storage in the construction are investigated as two alternative storage options in terms of their ability to increase wind power utilisation and to provide cost-effective fuel savings. Results show that passive heat storage can enable equivalent to larger reductions in excess electricity production and fuel consumption than heat accumulation tanks. Moreover, passive heat storage is found to be significantly more cost-effective than heat accumulation tanks. In terms of reducing fuel consumption of the energy system, the installation of heat pumps is the most important step. Adding heat storages only moderately reduces the fuel consumption. Model development has been made to facilitate a technical optimisation of individual heat pumps and heat storages in integration with the energy system. [Copyright &y& Elsevier]

• A new method is presented to design water-energy systems in islands. • Optimal energy-water systems were obtained based on different indicators. • The proposed method increased the contribution of renewables from 2.4% to 24.6% • Wind power supports the renewable development of water-energy systems on islands. This paper presents a new method based on the Smart Energy System concept to link the water infrastructure and the energy system of an island. The principal aim of this study is to determine whether this new method can increase the contribution of renewables (wind power and photovoltaic) to the primary energy supply of the island. The method considers water production and treatment systems as flexible loads and explores a wide range of possible water supply infrastructures and PV/wind power combinations in the search for an optimal energy-water configuration. The final optimal solution is based on a balance between energy fuel needs and energy excesses, CO 2 emissions, oil consumption, minimization of total annual costs and maximization of the renewable contribution. The proposed method increased the contribution of renewables from 5.14% to 24.6%. This corresponds to, on average, over 35% of the hourly electricity demand throughout 2018 being covered by renewables, against the current 6.6%. The study reveals that wind technology integration is of fundamental importance for renewable exploitation in insular water-energy systems, with wind energy contributing more than 70% of the renewable participation in this case study. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present options to make low-carbon footprint large-scale desalination a reality on arid islands with weak electrical grids. Through these options, the goal is to reconfigure on-grid wind energy/desalination systems for large- and medium-scale water production. In this context, it is proposed to use lithium-ion batteries for stationary energy storage together with management strategies aimed at avoiding the wind energy/desalination systems having to consume energy from the conventional grid they are connected to. The control strategy is based on ensuring that the power provided by the wind farm and batteries remains in synchrony with the power demand of the desalination plant throughout the system's useful life. The interannual variation of wind energy is considered when sizing the renewable energy system and processes for its estimation are proposed. The case study is centred on the Canary Archipelago, a region that is especially vulnerable to the impacts of climate change, but which enjoys exceptional characteristics for the exploitation of wind energy. The results obtained show the optimal wind farm and energy storage system capacities of the analysed configurations. The approach presented allows a low-carbon operational footprint. If the control strategy were to be put into practice today, the current grid restrictions and a life cycle assessment of the system carried out in a societal context that continues to be fossil fuel dependent indicate a potential reduction of 77.4% of the footprint. However, the remaining 22.6% could be eliminated in the future when the manufacturing processes of wind turbines, batteries and desalination plants receive the benefits of carbon-neutral societies. [Display omitted] • A method for achieving large-scale, low-carbon desalination is presented. • Optimal wind farm and storage capacities for the system are determined. • The method offers substantial CO2 emission reduction potential. • Using climate ERA5 reanalysis data, enhances robustness by addressing wind variability. • Proposed adjustments enhance adaptability to technological advances and future scenarios. [ABSTRACT FROM AUTHOR]

Abstract: Aalborg Municipality, Denmark, wishes to investigate the possibilities of becoming independent of fossil fuels. This article describes a scenario for supplying Aalborg Municipality’s energy needs through a combination of low-temperature geothermal heat, wind power and biomass. Of particular focus in the scenario is how low-temperature geothermal heat may be utilised in district heating (DH) systems. The analyses show that it is possible to cover Aalborg Municipality’s energy needs through the use of locally available sources in combination with significant electricity savings, heat savings, reductions in industrial fuel use and savings and fuel-substitutions in the transport sector. With biomass resources being finite, the two marginal energy resources in Aalborg are geothermal heat and wind power. If geothermal heat is utilised more, wind power may be limited and vice versa. The system still relies on neighbouring areas as an electricity buffer though. The costs of the scenario are at a comparable level with the reference situation, but with significantly higher needs for investments and lower fuel costs. Implementation of the scenario would therefore have a positive socio-economic impact as investments are more local labour-intensive than fuel supply. [ABSTRACT FROM AUTHOR]

• Hybrid mechanical energy storage of TCAES-ORC is techno-economically investigated. • The levelized cost of storage of the hybrid system is compared to the competitors in the market. • Impacts of real fluctuating operating conditions on the system's performance are taken into account. • The results prove that the impacts of load fluctuations on the system performance are significant. • The levelize cost of energy storage for a wind farm case study is weakened by at least 10%. Trigeneration compressed air energy storage (TCAES) is one of the emerging solutions that will most likely find its market as a popular energy storage technology for sector coupling. The combination of a TCAES with an organic Rankine cycle (ORC) for waste heat recovery has also been found much effective for enhanced round trip efficiency and is thus to be preferred over conventional TCAES designs. The combined configuration is claimed to offer a very high coefficient of performance (COP) exceeding 1.5. This work aims to quantify realistic performance expectations from a combined TCAES-ORC subject to real operating conditions accompanied for instance by a wind turbine. The system is dynamically modeled, and its performance is analyzed regarding energetic/exergetic efficiency, environment, and economy. To make the investigations close to real-life conditions, a medium-sized 5 MW capacity TCAES-ORC unit is considered integrated with a wind farm for off-peak electricity utilization for storage and tri-generation of heat, cooling, and electricity when charging or discharging. The location of the use case is considered West Denmark, for which wind power production and pricing profiles are available. The results show that there is a considerable collapse in the cooling and power production when the system comes to low operating loads, while heat production potential is not significantly affected. The COP factor decreases from 1.5 in nominal mode to 1.26 in the off-design mode for a sample dynamic load, where the exergetic efficiency is reduced from 64% to 58%. With such a technical operation degradation, the levelized cost of storage (LCOS) is weakened from 141 €/MWh to 153.7 €/MWh, and the potential emission reduction will fall from 4163 to 3640 tonnes of equivalent CO 2 per year. [ABSTRACT FROM AUTHOR]

To deal with the high penetration of renewable energy, modern energy systems strive to introduce flexible resources to provide more flexible and higher quality services. This paper focuses on the coordination of flexible resources across different energy carriers under the market environment to accommodate different levels of wind power. The integration of gas, heat and electricity systems providing customers with multiple options for satisfying their energy demands is described. Considering that energy system operators are independent or have limited communication based on the existing market mechanism, an equilibrium problem is first formulated for the optimal scheduling strategy, where each subsystem operator pursues its own benefit. Since there is energy conversion between different energy subsystems, each subsystem operator has to consider the actions of other operators and coordinate with each other until an equilibrium. An illustrative case study is then analyzed to show that the proposed model allows each subsystem operator to make an optimal action for maximizing its profit, and reflects prices and volumes of the energy transaction among energy subsystems. Furthermore, the simulation results indicate that the coordination of flexible resources has significant benefits in the integrated energy system to reduce wind curtailment and improve total social welfare. • An integrated energy system with multiple flexible resources was described. • An equilibrium model for energy distribution and energy trading was proposed. • The effect of different wind power levels on subsystem operators was discussed. • The positive impact of DR on system operation and market behaviors was explored. [ABSTRACT FROM AUTHOR]

As the rapid development of wind energy and electricity markets, wind farms (WFs) in mounting numbers join the electricity markets such as spot and regulating markets, etc. The large-scale integration of WFs into the power system may threaten the safe and stable operation of power systems due to the inherent fluctuation nature of wind power, and as a consequence, the WFs may be penalized by the grid operator in the electricity market. In this case, WF owners will take actions to reduce the fluctuation and one of the promising strategies is to integrate battery storage system (BSS) into the WFs. Base on this idea, a novel framework of considering fluctuation penalty (FP) in the Danish spot market which is the electricity market investigated in this study is firstly proposed. The economic feasibility of integrating BSS into a WF in the spot market is analyzed and a bi-level programming is adopted to design the sizing of the BSS based on Return on Investment (ROI). This research also analyzes the impact of various fluctuation penalties and subsidies on the ROI. It is found that the net revenue of integrating BSS into a WF can increase by 15.8% and the FP can reduce by 64.9% in the spot market with the FP. [ABSTRACT FROM AUTHOR]