Integrating distributed generation: Regulation and trends in three leading countries

This paper explores the trends in the deployment and integration of distributed generation in Germany, Denmark and Sweden. The study concentrates on the regulation of renewable energy generation with a focus on grid access and connection mechanisms. The high rate of distributed generation penetration is mainly based on the early support that these countries gave to the expansion of renewable energy generation – mainly wind and solar – within their respective national policies. Germany and Denmark are the ones with the most sophisticated support schemes, which have shown a dynamic design over time. In terms of connections, Germany has the most favorable connection regime which provides not only priority connection but also priority grid access for generation units that produce electricity from renewable energy sources. Sweden guarantees equal treatment among different technologies (i.e. a non-discrimination principle). High connection costs have been observed specially in Germany and Denmark. The costs of network upgrades are usually socialised across demand customers. However, integration issues should be taken into consideration in order to avoid expansion of distributed generation in a way which unnecessarily raises total system costs, via high connection costs.     

Evaluation of distributed building thermal energy storage in conjunction with wind and solar electric power generation

Energy storage is often seen as necessary for the electric utility systems with large amounts of solar or wind power generation to compensate for the inability to schedule these facilities to match power demand. This study looks at the potential to use building thermal energy storage as a load shifting technology rather than traditional electric energy storage. Analyses are conducted using hourly electric load, temperature, wind speed, and solar radiation data for a 5-state central U.S. region in conjunction with simple computer simulations and economic models to evaluate the economic benefit of distributed building thermal energy storage (TES). The value of the TES is investigated as wind and solar power generation penetration increases. In addition, building side and smart grid enabled utility side storage management strategies are explored and compared. For a relative point of comparison, batteries are simulated and compared to TES. It is found that cooling TES value remains approximately constant as wind penetration increases, but generally decreases with increasing solar penetration. It is also clearly shown that the storage management strategy is vitally important to the economic value of TES; utility side operating methods perform with at least 75% greater value as compared to building side management strategies. In addition, TES compares fairly well against batteries, obtaining nearly 90% of the battery value in the base case; this result is significant considering TES can only impact building thermal loads, whereas batteries can impact any electrical load. Surprisingly, the value of energy storage does not increase substantially with increased wind and solar penetration and in some cases it decreases. This result is true for both TES and batteries and suggests that the tie between load shifting energy storage and renewable electric power generation may not be nearly as strong as typically thought.     

The research agenda on social acceptance of distributed generation in smart grids: Renewable as common pool resources

The rapid developing literature on ‘smart grids’ suggests that these will facilitate ‘distributed generation’ (DG) preferably from renewable sources. However, the current development of smart (micro)grids with substantial amount of DG (“DisGenMiGrids”) suffers from a focus on mere ‘technology’. Ongoing problems with deployment of renewable energy have shown that implementation is largely determined by broad social acceptance issues. This smart grid development is very important for further renewables deployment, but again there is a tendency to continue the neglect of social determinants.Most technical studies apply implicit and largely unfounded assumptions about the participation in and contribution of actors to DisGenMiGrid systems. This lack of understanding will have severe consequences: smart grids will not further renewables deployment when there are hardly actors that are willing to become part of them. This review is a first attempt to address the social construction of smart electricity grids. As institutional factors have proved to be the main determinants of acceptance, these will also be crucial for further renewables deployment in micro-grid communities. Elaboration of the institutional character of social acceptance and renewables’ innovation calls for an institutional theory approach involving Common Pool Resources management, because these socio-technical systems aim to optimise the exploitation of natural resources. Citizens/consumers and other end-users increasingly have the option to become more self-sufficient by becoming co-producers of electricity.They may optimise the contribution of DG when they cooperate and insert their renewable energy in a cooperative microgrid with mutual delivery. Moreover, the option to include ‘distributed storage’ capacity (electric vehicles) in these microgrids, enables an increasing share of renewables deployment. However, all these options should be institutionally opened. This requires much self-governance and flexible overall regulation that allows microgrids.The research agenda should focus on how such new systems become institutionally embedded, and how they are socially constructed.     

Environmental benefits of distributed generation with and without emissions trading

The need for improving energy efficiency and reducing CO₂ emissions and other pollutants, as well as the restructuring of energy markets has favoured the increase of distributed energy resources (DER). The co-ordinated control of these sources comprising renewable energy sources (RES) and distributed generators (DG) characterised by higher efficiencies and lower emissions compared to central thermal generation, when based on coal or oil provide several environmental benefits. These benefits can be quantified based on DER participation in the CO₂ emission trading market. This paper provides a method to calculate emissions savings achieved by the marginal operation of DER in liberalised market conditions using available emissions data. The participation of DER in emissions trading markets is also studied, with respect to profits, pollutants decrease and change in operating schedules. It is shown that the operation of DER can significantly reduce pollutants, provided sufficient remuneration from CO₂ emission trading market participation is provided. Moreover, it is shown that using average emissions values to calculate the environmental benefits of DER might provide misleading results.     

Beyond smart grids - The need of intelligent energy networks for a higher global efficiency through energy vectors integration

From the energy point of view, the season we have been living more and more seems the era of sources diversification. The most correct scenario for a sustainable energy future foresees no predominance of one source over the others in any area of the world but a proper energy mix, based on locally available resources and needs.The concept and role of energy vectors is key: “(an energy vector) allows transfer, in space and time, a given quantity of energy, hence making it available for use distantly in time and space from the point of availability of the original source”. Therefore, a scenario that gives full scope for the ES to be immune from the characteristics of non-sustainable resource consumption and waste production, the system itself must shift the focus from resources to vectors (mainly electricity, hydrogen, heat).Smart grids have been largely indicate, in this context, as an answer for their characteristic “needful design” to move from the “old” grids (unidirectional power flows) to “new” bi-directional electricity networks. This is not enough: the real need is for an intelligent management of a complete set of energy sources and vectors, as electricity, heat, hydrogen, bio and non-biofuels, that requires a clear shift that goes beyond smart grids and looks at Intelligent Energy Networks.     

City density and CO2 efficiency

Cities play a vital role in the global climate change mitigation agenda. City population density is one of the key factors that influence urban energy consumption and the subsequent GHG emissions. However, previous research on the relationship between population density and GHG emissions led to contradictory results due to urban/rural definition conundrum and the varying methodologies for estimating GHG emissions. This work addresses these ambiguities by employing the City Clustering Algorithm (CCA) and utilizing the gridded CO₂ emissions data. Our results, derived from the analysis of all inhabited areas in the US, show a sub-linear relationship between population density and the total emissions (i.e. the sum of on-road and building emissions) on a per capita basis. Accordingly, we find that doubling the population density would entail a reduction in the total CO₂ emissions in buildings and on-road sectors typically by at least 42%. Moreover, we find that population density exerts a higher influence on on-road emissions than buildings emissions. From an energy consumption point of view, our results suggest that on-going urban sprawl will lead to an increase in on-road energy consumption in cities and therefore stresses the importance of developing adequate local policy measures to limit urban sprawl.     

Modelling of energy systems with a high percentage of CHP and wind power

This paper presents the energy system analysis model EnergyPLAN, which has been used to analyse the integration of large scale wind power into the national Danish electricity system. The main purpose of the EnergyPLAN model is to design suitable national energy planning strategies by analysing the consequences of different national energy investments. The model emphasises the analysis of different regulation strategies and different market economic optimisation strategies.At present wind power supply 15% of the Danish electricity demand and ca 50% is produced in CHP (combined heat and power production). The model has been used in the work of an expert group conducted by the Danish Energy Agency for the Danish Parliament. Results are included in the paper in terms of strategies, in order to manage the integration of CHP and wind power in the future Danish energy supply in which more than 40% of the supply is expected to come from wind power.     

Second generation biofuels: Economics and policies

This study reviews economics of production of second generation biofuels from various feedstocks, including crop and wood/forestry residues, lignocellulosic energy crops, jatropha, and algae. The study indicates that while second generation biofuels could significantly contribute to the future energy supply mix, cost is a major barrier to its commercial production in the near to medium term. Depending upon type of biofuels, feedstock prices and conversion costs, the cost of cellulosic ethanol is found to be two to three times higher than the current price of gasoline on an energy equivalent basis. The median cost (across the studies reviewed) of biodiesel produced from microalgae, a prospective feedstock, is seven times higher than the current price of diesel, although much higher cost estimates have been reported. As compared with the case of first generation biofuels, in which feedstock can account for over two-thirds of the total costs, the share of feedstock in the total costs is relatively lower (30–50%) in the case of second generation biofuels. While significant cost reductions are needed for both types of second generation biofuels, the critical barriers are at different steps of the production process. For cellulosic ethanol, the biomass conversion costs needs to be reduced. On the other hand, feedstock cost is the main issue for biodiesel. At present, policy instruments, such as fiscal incentives and consumption mandates have in general not differentiated between the first and second generation biofuels except in the cases of the US and EU. The policy regime should be revised to account for the relative merits of different types of biofuels.     

Paradigm shift in urban energy systems through distributed generation: Methods and models

The path towards energy sustainability is commonly referred to the incremental adoption of available technologies, practices and policies that may help to decrease the environmental impact of energy sector, while providing an adequate standard of energy services. The evaluation of trade-offs among technologies, practices and policies for the mitigation of environmental problems related to energy resources depletion requires a deep knowledge of the local and global effects of the proposed solutions. While attempting to calculate such effects for a large complex system like a city, an advanced multidisciplinary approach is needed to overcome difficulties in modeling correctly real phenomena while maintaining computational transparency, reliability, interoperability and efficiency across different levels of analysis. Further, a methodology that rationally integrates different computational models and techniques is necessary to enable collaborative research in the field of optimization of energy efficiency strategies and integration of renewable energy systems in urban areas. For these reasons, a selection of currently available models for distributed generation planning and design is presented and analyzed in the perspective of gathering their capabilities in an optimization framework to support a paradigm shift in urban energy systems. This framework embodies the main concepts of a local energy management system and adopts a multicriteria perspective to determine optimal solutions for providing energy services through distributed generation.     

Best operative strategy for energy management of a cruise ship employing different distributed generation technologies

This paper aims to study the application of distributed generation technologies on a naval energy system, investigating the best operating strategy for energy management throughout an annual load profile. The thermo-economic analysis is performed considering electrical and thermal load demands referred to hotel and service loads of a cruise ship (around 6 MWel), both variable with the season and the period of the day, taking into account the off-design curves and cost functions for the different generators. Four different solutions are investigated, comparing the operative strategies in terms of energy efficiency, CO₂ emissions and annual costs.The analysis is performed with dedicated software for the thermo-economic time-dependent analysis, developed by the University of Genoa. The thermo-economic approach has general validity, thus it can be also applied to different kinds of ships, even considering different technologies for energy generation and storage.     

Convergence of rule-of-thumb sizing and allocating rules of distributed generation in meshed power networks

This paper presents different approaches to find out and address some rules for distributed generation (DG) integrated mesh type networks, which can be used in the management of future power systems. There are so many influencing factors of efficiency in the integration of DG that we need to analyze these influencing factors obviously. Hence, carefully planning plays a key role in tackling these challenges in the future power systems. In contrast to the majority of existing observations, we focus on the case where the underlying states are multiple and single DG allocations with changing conditions. In several previous studies, the best single bus has been investigated under the specified conditions. However, it follows from the results of this study that all issues concerning DG strongly depend on power network structure and DG locations, and it is worth to note that the best location changes with penetration levels. Also, it is observed that the all buses show different characteristics in terms of DG integrations under the different cases, moreover their optimum size and power factor are different. It means that optimum bus in a network changes with the conditions. On the other hand, the problematic buses can be occurred in voltage profile after the DG integration. As a result, an investigation of rule of thumb approach is performed for evaluation of performance enhancement of DG integrated meshed networks. The results are also used to discuss the integration of DG management strategies under various operating conditions.     

Distributed energy generation and sustainable development

Conventionally, power plants have been large, centralized units. A new trend is developing toward distributed energy generation, which means that energy conversion units are situated close to energy consumers, and large units are substituted by smaller ones. A distributed energy system is an efficient, reliable and environmentally friendly alternative to the traditional energy system. In this article, we will first discuss the definitions of a distributed energy system. Then we will evaluate political, economic, social, and technological dimensions associated with regional energy systems on the basis of the degree of decentralization. Finally, we will deal with the characteristics of a distributed energy system in the context of sustainability. This article concludes that a distributed energy system is a good option with respect to sustainable development.     

Urban energy generation: The added value of photovoltaics in social housing

Social housing offers an alternative for low-to-medium income families and keyworkers (teachers, nurses, and police). In the United Kingdom (UK), this fairly priced, rental accommodation is normally owned by housing associations. This paper explores urban energy generation (micro-generation) focussing on photovoltaics (PV) and how its generated electricity can be used to provide added value in terms of demand reduction and contribute to a reduction in fuel poverty. It presents the results associated from in-depth monitoring of nine low-energy social housing units equipped with PV systems commissioned in 2004 in the South of England, UK. We report on energy load profiles and relate these to occupier behaviour and any changes in consumption that occur. The results highlight the impact of micro-generation showing a close correlation between occupant behaviour and energy consumption. Increased energy awareness can lead to changes in the way energy is used, reducing overall consumption but ‘education’ must be sustained to ensure long-term energy reductions. The financial benefit of operating high demand electrical appliances at the peak of the solar day as opposed to in the evening when overall demand on the central grid is higher is highlighted. The paper also draws conclusions allied to the challenges that PV micro-generation technology presents in the social housing context.     

Power-to-Gas integration in the Transition towards Future Urban Energy Systems

Temperature levels play a key role in the thermal energy demand of urban contexts affecting their associated primary energy consumption and Renewable Energy Fraction. A Smart Heating strategy accounts for those supply features requiring new solutions to be effectively renewable and to solve the RES capacity firming. Power-to-Gas (P2G) is the way to decarbonize the energy supply chain as fraction of Hybrid fuels, combination of fossil ones and Renewable Hydrogen, as immediate responsive storage solution. While, Power-To-Heat is conceived as the strategy to modernize the high and medium temperature heating systems by electricity-driven machines to switch from Fuel-to-Heat to Electricity-to-Heat solutions. The authors investigated on different urban energy scenarios at RES share increase from 25% up to 50% in the energy mix to highlight strengths and weaknesses of the P2G applications. Primary Energy Consumption was chosen as the objective function. Three Reference Cities were chosen as reference scenarios. Moreover, the analytical models of P2G was designed and implemented in the reference energy system. The results of the twelve scenarios, four for each Reference City were evaluated in terms of amount of Renewable Heat delivered. Finally, the interaction between P2G and renewable heat production was evaluated.     

Large-scale integration of optimal combinations of PV, wind and wave power into the electricity supply

This article presents the results of analyses of large-scale integration of wind power, photo voltaic (PV) and wave power into a Danish reference energy system. The possibility of integrating Renewable Energy Sources (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 idea is to benefit from the different patterns in the fluctuations of different renewable sources. And the purpose is to identify optimal mixtures from a technical point of view. The optimal mixture seems to be when onshore wind power produces approximately 50% of the total electricity production from RES. Meanwhile, the mixture between PV and wave power seems to depend on the total amount of electricity production from RES. When the total RES input is below 20% of demand, PV should cover 40% and wave power only 10%. When the total input is above 80% of demand, PV should cover 20% and wave power 30%. Meanwhile the combination of different sources is alone far from a solution to large-scale integration of fluctuating resources. This measure is to be seen in combination with other measures such as investment in flexible energy supply and demand systems and the integration of the transport sector.     

Stabilization and control of tie-line power flow of microgrid including wind generation by distributed energy storage

High penetration of wind generation in electrical microgrids causes fluctuations of tie-line power flow and significantly affects the power system operation. This can lead to severe problems, such as system frequency oscillations, and/or violations of power lines capability. With proper control, a distribution static synchronous compensator (DSTATCOM) integrated with superconducting magnetic energy storage (SMES) is able to significantly enhance the dynamic security of the power system. This paper proposes the use of a SMES system in combination with a DSTATCOM as effective distributed energy storage (DES) for stabilization and control of the tie-line power flow of microgrids incorporating wind generation. A new detailed model of the integrated DSTATCOM-SMES device is derived and a novel three-level control scheme is designed. The dynamic performance of the proposed control schemes is fully validated using MATLAB/Simulink.     

Incentive policies for promoting wind power production in Brazil: Scenarios for the Alternative Energy Sources Incentive Program (PROINFA) under the New Brazilian electric power sector regulation

The Alternative Energy Sources Incentive Program (PROINFA) was designed in 2002 to stimulate the electricity generation from three energy sources (wind, biomass and small-scale hydro) in Brazil. The Program was divided into two phases. The first one uses feed-in tariffs for promoting the development of 3300 MW. The second one that was originally based on feed-in tariffs was modified in 2003, in order to be based on biddings for renewables. These biddings are capped to limit their impact on the final electricity tariff. Due to this bound, the highest-cost power option promoted by PROINFA (wind power generation) might have development problems. Simulating different scenarios for the biddings, it was verified that the only way to reach the original goal set by PROINFA (10% of the annual electricity consumption provided by alternative sources up to 2020) and, simultaneously, not overcome the bidding bound is to promote biomass-fired power generation alone, during the Program's second phase. However, this action contradicts one of the targets of the Program, which is to diversify the energy matrix. An alternative option could be biddings for renewables according to specific criteria (complementarities, industrial and technological development and cost), based not only on their cost-effectiveness.     

Network investments and the integration of distributed generation: Regulatory recommendations for the Dutch electricity industry

An increase in the distributed generation of electricity necessitates investments in the distribution network. The current tariff regulation in the Dutch electricity industry, with its ex post evaluation of the efficiency of investments, average benchmarking and a frontier shift in the x-factor, delays these investments. In the unbundled electricity industry, the investments in the network need to be coordinated with those in the distributed generation of electricity to enable the system operators to build enough network capacity. The current Dutch regulations do not provide for a sufficient information exchange between the generators and the system operators to coordinate the investments. This paper analyses these two effects of the Dutch regulations, and suggests improvements to the regulation of the network connection and transportation tariffs to allow for sufficient network capacity and coordination between the investments in the network and in the generation of electricity. These improvements include locally differentiated tariffs that increase with an increasing concentration of distributed generation.     

Large-scale integration of renewable and distributed generation of electricity in Spain: Current situation and future needs

Similar to other European countries, mechanisms for the promotion of electricity generation from renewable energy sources (RESs) and combined heat and power (CHP) production have caused a significant growth in distributed generation (DG) in Spain. Low DG/RES penetration levels do not have a major impact on electricity systems. However, several problems arise as DG shares increase. Smarter distribution grids are deemed necessary to facilitate DG/RES integration. This involves modifying the way distribution networks are currently planned and operated. Furthermore, DG and demand should also adopt a more active role. This paper reviews the current situation of DG/RES in Spain including penetration rates, support payments for DG/RES, level of market integration, economic regulation of Distribution System Operators (DSOs), smart metering implementation, grid operation and planning, and incentives for DSO innovation. This paper identifies several improvements that could be made to the treatment of DG/RES. Key aspects of an efficient DG/RES integration are identified and several regulatory changes specific to the Spanish situation are recommended.