Techno-economic-environmental evaluation framework for integrated gas and electricity distribution networks considering impact of different storage configurations

Highlights

• Techno-Economic-Environmental (TEE) operation of Gas & Electricity Networks (GEN) evaluated.

• All the parameters affecting the TEE performance of GENs were studied.

• Both single-vector storage and vector-coupling storage devices were investigated.

• Impact of storage configuration on the TEE performance of GENs was investigated.

Abstract

This paper presents an evaluation framework for Techno-Economic-Environmental (TEE) performance of the Integrated Gas and Electricity Distribution Networks (IGEDNs). The proposed framework is based on a coupled gas and electric load flow model, facilitating the consideration of all the parameters affecting the operation of IGEDNs, such as different gas mixtures, gas temperature, pipeline characteristics and the electricity network topology. This framework can assess the impact of different storage configurations, different levels of Renewable Energy Sources (RESs) and different levels of energy demand on the amount of imported energy from the upstream networks, operational costs and emissions of the IGEDNs. The evaluation framework can perform the TEE operational analysis of future scenarios of IGEDNs through various coupling components and storage devices including Single-Vector Storage (SVS) as well as Vector-Coupling Storage (VCS) devices to provide a basis for well-informed design choices for meeting the Greenhouse Gas (GHG) reduction targets. The TEE evaluation framework is tested on a real-world case study from a rural area in Scotland, and analysed from different aspects, to show the effectiveness of the model for analysis of the interactions of gas and electricity distribution networks. The results reveal that integrated operation of the gas and electricity networks improves all the considered technical, economic and environmental parameters.

Introduction

Governments around the world are working hard to reduce their Greenhouse Gas (GHG) emissions. In the UK, the government has set a target of “Net Zero” GHG emissions by 2050 in order to reduce contribution to global warming [1]. This necessitates the integration of more Renewable Energy Sources (RESs) into the energy networks and consequently reduction in the use of fossil fuels while meeting and reducing energy demand.

To achieve the aforementioned objective flexibly and reliably, it may be necessary to couple the energy networks using several network coupling components such as gas turbine (GT), power-to-gas (P2G) and Combined Heat and Power (CHP) [2]. Also, the energy networks may benefit from different types of Energy Storage Systems (ESSs) in order to be able to compensate for any energy carrier deficit or other constraints in energy supply in any of the networks [3].

In order to comprehensively study multi-vector integrated energy systems and analyse ESS potentials, a Techno-Economic-Environmental (TEE) evaluation framework needs to be designed to investigate the mutual impacts of each of the networks on the operational, economic and environmental performance of others. This is the main aim of this study.

In this paper, ESSs are divided into two different categories of Single-Vector Storage (SVS) and Vector-Coupling Storage (VCS). The SVS refers to a storage device which is charged and discharged through one single vector (e.g. gas or electricity). Whereas, the VCS refers to a storage device which is charged by one of the vectors and discharges into the other vector. In other words, the VCS is at the interface of the two integrated networks and forms part of the coupling between the two networks. A conceptual representation of these storage devices in an Integrated Gas and Electricity Distribution Network (IGEDN) is demonstrated in Fig. 1.

Once the framework is developed then the performance of the future scenarios of the energy system can be assessed in terms of security, sustainability and affordability, namely the elements of the energy trilemma. In this way, the basis for well-informed design choices for meeting the GHG reduction targets is provided.

EnergyPLAN [4] and LUT-EST models [5], [6], [7] have been used to perform planning of the whole energy system of a few regions, namely Finland [4], India [5], Iran [6] and Europe [7] considering all the layers of the energy system from energy resources, energy transmission and distribution. Based on the documentation of EnergyPLAN [8] and LUT-EST model [9] these models do not perform a detailed operational analysis to ensure the integrated networks are operable and network constraints are not violated.

Different types of energy storage in multi-vector energy networks have been investigated at the hub level to perform techno-economic [10], [11], [12], [13], [14], [15] or TEE [16], [17], [18], [19] analyses. However, only a few of these references have studied the impact of the capacity of storage devices on technical [17], economic [10], [18] or techno-economic [16] parameters of the hub. Nevertheless, hub level analysis does not consider the detailed operation of the network to ensure the network is physically operable and will meet the load without violation of operational constraints.

On the other hand, references on operational analysis of integrated energy networks with storage at a detail network level have only carried out technical [20], [21] or techno-economic [22], [23], [24], [25], [26], [27] analysis. None of these papers has performed an environmental analysis. Also, none of these research works has evaluated the impact of different storage configurations¹ on the TEE parameters of integrated gas and electricity networks.

The framework presented in this paper can help in validating the solutions developed in these references in terms of the amount of imported energy from upstream networks, the operational costs and the emissions of IGEDN. In addition, since the framework is based on a more detailed model, it enables consideration of all the parameters affecting the operation of IGEDN, including various storage configurations as well as different percentages of gas mixtures, gas temperature, characteristics of the pipelines, and the electrical network topology and parameters.

Furthermore, there are several other references, such as [28], [29], [30], that have investigated either design or operational planning of different energy conversion/storage technologies in a single energy vector (usually electricity). Although these references have considered the point(s) of connection to the other energy vector(s), i.e. gas or heat networks, they have not considered the operation of those other coupled energy network(s). It is to be noted that considering the main research direction of this paper, only the references on more than one energy vector have been reported and summarised here and the papers on a single energy vector have not been considered.

In brief, a taxonomy of previously published works in the area is presented in Table 1 which highlights the main contributions of the current work.

The aforementioned literature review on the integrated energy networks including storage demonstrates that the following gaps need to be further investigated:

• Previous works on detailed network level operational analysis have only performed a techno-economic analysis and the environmental analysis is not yet considered.

• Previous works have not investigated the impact of different storage configurations, including types and capacities, on the TEE parameters of the networks.

• Previous works have not studied the impact of single-vector storage and vector-coupling storage, simultaneously.

According to the identified gaps, the main contributions of this paper can be summarised as follows:

• Development of an evaluation framework to investigate the performance of IGEDN in terms of the energy trilemma, to assess the TEE performance of IGEDN, through network level detailed operational analysis model.

• A precise model is developed of IGEDN to consider the inter-dependency of the networks and at the same time all the parameters affecting the TEE performance of the integrated networks.

• Application of the framework allows to evaluate the impact of different storage configurations on the TEE performance of IGEDN.

• Evaluation of the impact of including both SVS and VCS devices for better integration of the networks.

The proposed framework will enable researchers and decision-makers to assess future energy scenarios in terms of TEE parameters and hence make well-informed design choices for the energy system to meet specific GHG reduction targets. The framework will also help in addressing the following research questions:

• What are the TEE benefits of the integrated operation of gas and electricity distribution networks with storage in both networks?

• How does the variation of storage configurations impact the TEE parameters of IGEDN?

• How do load profiles and renewable generation profiles impact the TEE performance of IGEDN?

The rest of the paper is structured as follows: Section 2 describes the proposed TEE evaluation framework. The case study and description of the developed scenarios are reported in Section 3. Results and discussions on the case studies are explained in Section 4. Finally, the conclusion and future works are presented in Section 5.