High level technical design and economic

assessment of renewable energy solutions

for radio base stations

by H. Rüterbusch
Dipl.-Ing (FH) / Dipl. Wirt. Ing. / Dipl.-Kfm

Term paper on the subject of `autarkic energy systems′ as part of the
University of Kassel/Germany′s renewable energy study module

Hausarbeit zum Schwerpunkt "Autarke Energiesysteme"
im Rahmen des Studienmoduls "AEE" des Studiums "E+U"

1 Introduction 4

1.1 About this document 4

1.2 About the author 4

1.3 Issue definition 5

1.4 Scope 5

1.4.1 In scope 5

1.4.2 Out of scope 5

2 Mobile operators 6

2.1 Role and motivation 6

2.2 Technical context 7

2.3 Technical characteristics 8

3 How to get RES@RBS 9

3.1 Network perspective: prerequisites (macro view) 9

3.2 Site perspective: planning steps (micro view) 9

4 Selected technical recommendations 11

4.1 General 11

4.2 Technical design 11

4.3 Solar 13

4.4 Wind 13

4.5 Batteries 15

4.6 Charger, controller 16

4.7 Diesel generator 17

4.7.1 Accessories (cabling) 18

5 High level RES assessment (RAFORS) 19

5.1 Purpose 19

5.2 Abstract 19

5.3 Simplifications / restrictions 20

5.4 How to work with RAFORS 21

5.4.1 General 21

5.4.2 Input data 21

5.4.3 Output 22

5.5 Calculation 23

5.5.1 Power 23

5.5.2 PV 23

5.5.3 Battery 24

5.5.4 Wind 25

5.5.5 Diesel generator 25

5.5.6 Economic aspects 25

5.6 Way forward 27

6 Definitions 28

6.1 Glossary 28

6.2 Abbreviations 29

6.3 Abbreviations (formulas) 30

6.4 Figures 31

6.5 Tables 31

7 Appendix 32

7.1 Example of a `Site questionnaire to plan RES based radio stations′ 32

7.2 Example of a 3-phase design 33

7.3 Example of an RES@RBS assessment with RAFORS 34

7.4 Suppliers (examples) 36

7.5 Symbols (electrical) 37

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1 Introduction

1.1 About this document

This document describes a high level technical design for and the economic assessment of renewable energy solutions for radio base stations (RBS). It proposes a way forward in the development of ′hybrid′ solutions with renewable energy sources (RES) for off-grid RBS sites.

The main purpose of this document is to provide initial practical, technical and economic guidance. It is accompanied by an easy-to-use EXCEL-based tool (RAFORS ­ Renewable energy Assessment FOr Radio Sites) for the assessment of the net present costs (NPC) of these solutions.

The following sections outline the specific requirements of mobile operators and provide specific technical guidance for the selection and implementation of the elements of a hybrid system.

This information will enable mobile operators without any detailed technical and commercial knowledge to develop initial ideas on the design of such a system and provide them with a common basis for further discussion, evaluation and benchmarking.

References to external documents in the glossary are in square brackets [ ] and cross links to specific sections of this document are indicated as follows: >> section_name.

Note: this document is part of my final examination in the renewable energy study module at the University of Kassel. The precise definition of the term paper can be found in >> Issue definition

1.2 About the author

Comments, remarks and questions about this document are welcome! Just send an e-mail to Heinz.rueterbusch@gmx.de The author is working in Vodafone′s Technology Network Department on energy and Infrastructure solutions to support the Vodafone operating companies.

He is a member of the Environmental Engineering (EE) Group within the European Telecommunications Standards Institute (ETSI).

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1.3 Issue definition

Subject: <High level technical design and economic assessment of renewable energy solutions for radio base stations>

The aim of this paper is to describe and discuss the different aspects of the technical design and economic assessment of renewable energy solutions for radio base stations. The following points should be considered:

A. Load profiles, user requirements, resources, typical technical concepts for radio base stations. >> Technical characteristics

B. Renewable energy-oriented technical design. Possible concepts, adaptation of different energy sources, integration of the components (PV, wind generator, diesel, batteries, chargers/inverters, management/control, accessories) >>How to get RES@ and >> Technical design

C. Economic assessment and comparison of different technical solutions >> High level RES assessment (RAFORS)

D. Design of a "Site questionnaire to plan RES based radio stations" >> Example of a `Site questionnaire to plan RES based radio stations′

E. Presentation of an example (including schematic diagram and nominal characteristics of the components) >> Example of an RES@RBS assessment with RAFORS Note: >> indicates the section in which the aspect is covered.

1.4 Scope

1.4.1 In scope

- Off-grid RBS sites

- Renewable energy

- Technical aspects

- Economic assessment

1.4.2 Out of scope

x

Detailed site-specific planning

- Switching centres

- Specific suppliers

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2 Mobile operators

2.1 Role and motivation

Two of the key challenges facing mankind today are protecting the environment and combating climate change. Mobile operators are part of the information and communication technologies (ICT) sector and, as such, they play a key role since they are both part of the solution and part of the cause.

Figure 1: Example of how ICTs are contributing to global warming [1]

The illustration shows how telecommunication services can help to prevent global warming by providing an observing system.
ICTs consume power, radiate heat and emit carbon dioxide due to the operation of the telecom network >> Technical context. The objective is to reduce carbon dioxide emissions because these emissions are what cause global warming. A reduction of carbon dioxide emissions can be achieved principally by
- improvements in energy efficiency and
- increased use of renewable energy sources (RES).
The challenge is to achieve energy-efficient and sustainable mobile communications through network and site optimisation and the use of renewable energy sources.
The use of RES will also help to reduce future operating expenditure (OPEX) on energy. However, the full net present costs (NPC) and financial expectations also have to be taken into account when considering alternatives.

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2.2 Technical context

The technical devices that are necessary for the operation of a mobile-to-mobile connection can be logically assigned to a `core′ network and an `access′ network. The access network contains the radio base stations (RBS), which are also called sites or base transceiver stations (BTS).

Figure 2: How a mobile network works [8]

The exchange switch is part of the core network. Around 80% of expended energy and the related carbon dioxide emissions are accounted for by the access network due to the number of RBS sites. Today′s European networks operate two technologies concurrently: 2G (GSM) and 3G (UMTS).
The RBS equipment mainly operates on direct current power (DC), with the exception of the conventional air-conditioning (AirCo or cooling) systems which cool the equipment and batteries >> Batteries. [...]