Elsevier

Applied Thermal Engineering

Volume 31, Issue 13, September 2011, Pages 2073-2083
Applied Thermal Engineering

Planning for a 100% independent energy system based on smart energy storage for integration of renewables and CO2 emissions reduction

https://doi.org/10.1016/j.applthermaleng.2011.03.014Get rights and content

Abstract

EU import dependence on hydrocarbons and resulting negative environmental impact related to their use led to setting of new measures and energy policy that will make, in time, a post carbon society more feasible and achievable. Energy systems of this society will be based on four pillars: Renewable Energy, Buildings as Positive Power Plants, Energy Storage and Smart grids in combination with Plug-in Vehicles. All these pillars must be supported by the use of smart energy storage. The results of previous research has shown that in order to increase security, efficiency and viability, there is need for energy storage, in primary or secondary form, in order to transfer energy surplus from period of excess to the period when there is a lack. The problem of today’s storage systems is that they increase the cost of already expensive, distributed and renewable energy sources. That makes the large scale use of storage systems even less economically viable in market circumstances, despite economics of scale. The paper shows results of an energy planning methodology applied to several cases where use of smart energy storage system helps integration of energy flows, transformations and energy demand at the location of the energy end-use or close to it. Main results presented in this paper focus on planning a 100% independent energy system of Croatia. They also show the role of energy storage in a self-sustainable energy system with excess electricity production from renewable energy sources. The technical and financial analyses have been carried out for periods of one year taking into consideration demands and renewable energy production during all hours.

Highlights

► Smart use of energy storage will support four pillars of the Post Carbon Society. ► RES in combination with energy storage may reduce CO2 emissions in Croatia by 82%. ► Use of energy storage could improve and guide development of a real energy system. ► The paper shows results of an energy planning methodology applied to several cases.

Introduction

In 2007, the primary energy import dependency of the EU-27 was 53.1%. It is expected that in the next 20–30 years it will reach or surpass 70%. The situation in Croatia is similar, where in 2008 the import dependence was 52.3%, while for 2030 it is predicted to reach 72% [1]. EU-27 imports: 41.2% of solid fuels, 82.6% of oil and 60.3% of gas [2]. Such dependence on imported hydrocarbons leads to decreased security of energy supply as the import from Russia surpassed 1/3rd of total imported fossil fuels and approximately 1/3rd of imported gas and oil come from unstable geopolitical regions. Of course, competition for those same resources from developing countries is progressively growing. Thus, the EU energy strategy and a compatible Croatian strategy are focused on policies and measures that will increase the share of renewable and distributed energy sources, increase energy savings and improve energy efficiency. All these measures will increase the security of energy supply and decrease green house gas emissions. Moreover, the latest actions of the EU energy policy makers are focused on promoting and planning of the Post Carbon Society [3] and [4]. The four pillars of energy systems of the Post Carbon Society, as they were presented by Carvalho et al. [5], are:

  • • Renewable energy

  • • Buildings as positive power plants

  • • Energy storage

  • • Smart grids and plug-in vehicles

These characteristics will also be the result of strong political, public and economic support for all renewable energy technologies. In the EU political support has been reflected through European Energy Policy and primarily by its directives, the EU “climate and energy package” and The Strategic Energy Technology Plan (SET Plan). EU had an indicative target to cover 12% of the gross inland energy consumption by RES in 2010. New RES directive is setting RES target for 2020 on 20% of the gross final energy consumption, while the most recent initiatives have already begun process to convert EU Energy supply to 100% RES. On 15th April 2010 RE-thinking 2050 Campaign [6] was launched in the European Parliament. It outlines a path how the European Union can switch to a 100% renewable energy supply (for electricity, heating and cooling as well as transport), and harvest the positive effects of Europe’s energy supply system and reduce CO2 emissions. RE-thinking 2050 and similar initiatives [7], [8], [9], [10] will help to create Post Carbon Society for the EU. As it is highlighted by Prof. Carvalho [3]: A post carbon society makes it possible to reframe the energy and climate change challenges as opportunities, not just to foster a wealthier society, but also to create a more equitable and sustainable one. The Post Carbon Society is the concept that explains a more sustainable world, independent from the use of fossil fuels. It describes the process of change and the necessary development of new technologies together with their integration in energy, environment and other systems. Aside technological change, it will require changing of society life-styles and behaviour. For more information on these issues see Refs [3], [4].

In order to increase efficiency and viability of power systems, there is need for energy storage, in primary or secondary form, in order to transfer energy surplus from period of excess production (or cheaper production) to other more appropriate periods. Although storage systems have a positive effect on RES integration, their problem is that they increase the cost of already expensive distributed and renewable energy sources, making them, in market circumstances, even less economically viable.

Many energy storage technologies have been present on the market for more than a century. What is novel and smart in these technologies is their use for specific purposes and their synergies with new processes and combination with other energy sources.

Use of traditional energy storage for increasing RES integration has been tackled and proposed by many authors. Use of pumped hydro storage (PHS) is proposed in [11], [12], [13] batteries in [14], [15], [16] and compressed air energy storage (CAES) in [17]. Use of emerging technologies as flow batteries and storages connected to new energy carriers has been explained in [15], [18], [19]. Thermal storage and heat pumps could be used to store excess of RES production as showed in [20] or effectively combined with smaller scale applications to rise profits as modelled and explained in Ref. [21].

Some solutions based on novel principle of use of the thermal storage for electricity storage and generation in cases where PHS or CAES are not applicable are explained in [22]. A more detailed review of thermal storage, in particular thermal storage with phase change materials and their application is given in [23]. Cooling storage could also be used for the integration of renewable energy sources [24], [25].

The idea behind this work was to see how smart use of energy storage could improve and guide the development of a real energy system. In addition, it was needed to investigate different approaches for addressing intermittency problems and energy independency for selected sectors. It was also important to compare the planned system without storage and an alternative with storage, thus highlighting advantages and disadvantages. Energy storage system could help with integration of energy flows, transformations and energy demand at the location of the energy end-use or close to it. The smart use of energy storage will support all four pillars of the Post Carbon Society.

Section snippets

Problem background, methods and tools implemented in the case study

This section presents the main issues that arise in using energy storage in long-term planning of energy systems. It continues by presenting tools used by the authors for modelling as well as three major scenarios/systems modelled and investigated.

By portraying three different cases, the current status and possible development of the Croatian Energy System will be given. Information used in the modelling will be presented together with the assumptions and regulation strategies applied to the

Analysis of the reference case for 2008

Despite difficulties in obtaining some data that represents real hourly consumption in 2008, the final numbers have showed that EnergyPLAN model could represent the Croatian energy system adequately. Comparison of the gross energy consumption by fuel and electricity exports for two different calculations (market and technical optimization) and data from the literature have been presented in the Fig. 1.

Gross fuel consumption by sector is given in Fig. 2. It shows big differences in energy sector

Conclusion

This paper presents a new approach in planning of the Croatian energy system with significant emphasis on integration of RES energy by use of different energy storage technologies and system regulation strategies. It presents results of planning for a 100% independent energy system as just one possible alternative for the development of the Croatian energy system. Even though total independency has not been achieved in a planning sense, due to different needs for fossil fuels in various

Acknowledgements

Authors would like to thank the National Foundation for Science, Higher Education and Technological Development of the Republic of Croatia for supporting the project “Role of the Smart Energy Storage in 100% Independent Energy Systems” and the Ministry of Science, Education and Sport of the Republic of Croatia for supporting the project “Smart Energy Storage for Sustainable Development of Energy Systems” that resulted in this work.

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