Entirely renewable and self-sufficient municipal energy system

Transcription

1 Entirely renewable and self-sufficient municipal energy system Anja Kostevšek 1,2, Leon Cizelj 3, Janez Petek 4, Boris Sučić 5, Matevž Pušnik 5, Aleksandra Pivec 1 1 Scientific Research Centre Bistra Ptuj, Ptuj, Slovenia 2 Jožef Stefan International Postgraduate School, Ljubljana, Slovenia 3 Reactor Engineering Division, Jožef Stefan Institute, Ljubljana, Slovenia 4 Local Energy Agency Spodnje Podravje, Ptuj, Slovenia 5 Energy Efficiency Centre, Jožef Stefan Institute, Ljubljana, Slovenia anja.kostevsek@gmail.com Abstract. Municipal energy system is recognized as the one of the major development engines in greening the energy system. Integration of renewable resources into the energy system is the most appropriate choice in an attempt to decrease negative impacts on the environment. Various energy policies define targets with inclusion of different shares of renewable resources in specific time horizons. However, energy systems on 100% renewable supply still represent a challenge. The main objective of this paper is to demonstrate feasibility of the proposed renewable and self-sufficient municipal energy system. Energy model is used for setting the reference energy system and calculation of the scenarios. Performance of biomass, solar and renewable mix scenarios were conducted for this research. The paper discusses only technical aspects of the 100% renewable energy system. Keywords: municipal energy system, renewable energy sources, renewable and self-sufficient energy systems 1 Introduction Decarbonisation of energy systems represents a major issue in today s society. A variety of possible pathways is being proposed. With energy policies on European level additional targets were proposed, such as a 20% share of energy from renewable sources in the gross final energy consumption by 2020, and a 10% share

2 of renewable energy specifically in the transport sector [1]. On the other hand, some proposals are drafted to reach an 80% share from renewable energy sources (RES) by In the frame of the European Union energy climate package Slovenia set ambitious target by 2020 to achieve 25% renewable energy in the gross final energy consumption. According to the new National Renewable Energy Action Plan Slovenia 1 would play an active role in the development and promotion of the new technologies and solutions, which would enable wider usage of the renewable energy sources in industry, public, residential and transport sectors [2]. In order to accomplish future energy objectives on European and national level, additional work on local level has to be performed. The draft of Slovenian Energy Program 2 encourages the use of 100% renewable energy systems in five municipalities by 2020 and twenty municipalities by The importance of creation of a 100% renewable municipal energy system (MES) has also been recognized elsewhere [3]. This paper presents performance of energy scenarios to provide suitable structure of a 100% renewable and self-sufficient MES. The main focus is to demonstrate the technical eligibility of the 100% renewable MES. 2 Methodology 2.1 Model development The following step presents the selection of adequate energy planning tool for generating future scenarios of MES. Several modeling tools are available for local energy planning. In the Slovenian case, the decision was made on various assumptions and experiences from the constitution of previous energy models. MESAP (Modular Energy-System Analysis and Planning Environment) toolbox was brought up because it covers all the relevant tools for building an appropriate model for municipalities. The Reference Energy Environmental Model for Municipalities (REES-MOL), which was created for the city of Ljubljana, the capital of Slovenia, was transformed and adapted to calculate scenarios for renewable energy system of Podlehnik municipality. The REES-MOL is energy 1 National Renewable Energy Action Plan Slovenia National renewable energy action plan (NREAP) Slovenia, Ljubljana, July Slovenian Energy Program Proposal of the National Energy Programme of the Republic of Slovenia for the Period, draft, Ljubljana, June 2010.

3 system model which enables the analysis of energy policies on both the end-use and supply side. Model provides calculations of optimal combination of the local energy efficiency measures in all energy sectors and use of renewable sources for heat supply, distributed electricity generation, and wider usage of the combined heat and power production units [4]. 2.2 Scenario performance Calculations of numerous energy scenarios provide support to decision makers. By defining trade-offs among versatile parameters, an optimal solution must be identified based on an in-depth scenario analysis. A decision was made for processing three scenarios, based on two most important perspectives: the MES must implement the 100% renewable principle and the 100% self-sufficiency principle. At first, a reference energy scenario for year 2008 was performed. Through further research work the calculations of following scenarios were considered: biomass scenario (BIO), solar scenario (SOL) and RES mix scenario (MIX). Specific assumptions for each scenario are presented in Table 1. Table 1: Main assumptions of different scenarios Various assumptions BIO SOL MIX Individual heating: heat pumps 10% 10% 15% solar thermal 5% 10% 5% biomass boilers 45% 40% 40% district heating biomass (40%) biomass (40%) biomass (40%) Industry: biomass biomass biomass Electricity production mix 60% solar, 20% biomass, 20% biogas 80% solar, 10% biomass, 10% biogas 3 Practical applications in the Podlehnik municipality 70% solar, 15% biomass, 15% biogas Different supply mixes of renewable sources are provided at the basis of feasibility studies of every local renewable resource. Natural, economic, technological, social and political barriers put decision makers of future energy systems in a difficult

4 position. Potentials for RES deployment in the Podlehnik municipality were defined from previous analysis and are shown in Table 2. Table 2: RES potentials for Podlehnik municipality Types of RES Biomass Biogas from crops Biogas from manure Solar Geothermal Total potential Potential for future RES deployment MWh/a MWh/a MWh/a MWh/a MWh/a MWh/a Data for the present state and share of renewable resources are presented in Table 3 for year Table 3: Energy consumption for the Podlehnik municipality in 2008 Heat [MWh] Electricity [MWh] Conventional Conventional Total energy energy energy consumption RES share [%] sources RES sources RES [MWh] ,15 After the scenario calculations the results for the final energy consumption in year 2050 were provided and are shown in Table 4. Table 4: Final energy consumption for the Podlehnik municipality in 2050 Heat energy [MWh] Electricity energy [MWh] Total energy consumption RES share [%] RES RES [MWh] ,0 Scenario simulations indicate higher electricity consumption and lower heat demand in 100% RES municipal energy system. Overall energy consumption in year 2050 will be decreased in comparison to year 2008 in accordance to various energy efficiency assumptions adopted in the model.

5 4 Discussion and conclusion A modern MES with renewable supply mix differs in routes from present fossil based energy systems. Integration of 100% renewable and self-sufficient principles into MES presents the future goal of fighting climate change. The study confirmed technical feasibility of constituting a 100% renewable and self-sufficient MES. Assessment of scenarios should be performed on the basis of local conditions. On behalf of presented scenarios, decision makers may be able to depict the proper solution. For Podlehnik municipality the RES feasibility studies were included in the Local Energy Concept. Only general predictions from various previous analyses were presented. Further research would take place in defining more in-depth studies for specific RES potentials. This research considers only technical aspects of a 100% renewable MES. In the future perspective, also environmental, social and economic aspects need to be included. Penetration of new technologies and R&D activities in the field of renewable technologies will make an enormous impact on the outlook of the 2050 MES. To conclude with, transfer towards a 100% renewable MES would require a sequential adaptation process in different time horizons. Acknowledgements The research work of the corresponding author is supported by the European Slovenian Technology Agency under tender Young researchers from industry. Operation is partly financed by the European Union (European Social Fund). References: [1] The European Parliament and the Council of the European Union. Directive 2009/28/EC of the European Parliament and of the council of 23 April 2009 on the promotion of the use of energy from renewable sources, [2] National Renewable Energy Action Plan _action_plan_slovenia_en.pdf, 2010 [3] P. A. Østergaard, B. V. Mathiesen, B. Möller and H. Lund. A renewable energy scenario for Aalborg Municipality based on low-temperature geothermal heat, wind power and biomass. Energy, 35(12): , 2010 [4] Energy Efficiency Centre, Jozef Stefan Institute. Sustainable urban infrastructure-ljubljana- Prospectives by IJS, 2011.

6 For wider interest Climate change mitigation activities support usage of renewable resources due to their neutral impact on the environment. Various legislative acts stress the important role of municipalities in accomplishing the energy targets. This is why focus on municipality energy system and its development present a promising future orientation. Forming energy system on entirely renewable resources presents the new pathway, where the whole energy supply could be based on local supply facilities. In practice, the results could be applied for other municipalities, smaller local community, a district or a group of buildings. In addition, for concretizing the system more technical studies should be revealed. The case study was presented for Podlehnik municipal energy system. Analyses of three different scenarios leading to entirely renewable energy system with mixes of biomass, solar and electricity confirmed on the sufficiency of renewable resources. The results confirmed the technical feasibility to develop an independent renewable municipal energy system. Demonstration of possibilities to develop energy systems on a 100% renewable and 100% local supply represents added value. In the future several research activities should be focused in providing detailed analysis of integration of renewable resources into energy supply chain from technical, environmental, economic and social aspect.