Set of Rules. German DWA. Advisory Guideline DWA-M 114E. Energy from Wastewater Thermal and Potential Energy. June 2009

Transcription

1 German DWA Set of Rules Advisory Guideline DWA-M 114E Energy from Wastewater Thermal and Potential Energy June 2009 Energie aus Abwasser Wärme- und Lageenergie German Association for Water, Wastewater and Waste Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V.

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3 German DWA Set of Rules Advisory Guideline DWA-M 114E Energy from Wastewater Thermal and Potential Energy June 2009 Energie aus Abwasser Wärme- und Lageenergie Publisher/Marketing: German Association for Water, Wastewater and Waste Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V. Theodor-Heuss-Allee Hennef Germany Tel.: Fax: Internet:

4 The German Association for Water, Wastewater and Waste (DWA) is strongly committed to the development of secure and sustainable water and waste management. As a politically and economically independent organisation it is professionally active in the field of water management, wastewater, waste and soil protection. In Europe DWA is the association with the largest number of members within this field. Therefore it takes on a unique position in connection with professional competence regarding standardisation, professional training and information. The approximately 14,000 members represent specialists and executives from municipalities, universities, engineering offices, authorities and companies. Imprint Published and sold by: DWA German Association for Water, Wastewater and Waste Theodor-Heuss-Allee Hennef, Germany Tel.: Fax: Internet: info@dwa.de Corrected version: January 2011 Translation: Julia Degens, Erkrath (Germany) Printing (English Version): BUB, Bonn, Germany ISBN: Printed on 100 % recycled paper DWA German Association for Water, Wastewater and Waste, Hennef, Germany 2013 All rights, in particular those of translation into other languages, are reserved. No part of this Advisory Leaflet may be reproduced in any form by photocopy, digitalisation or any other process or transferred into a language usable in machines, in particular data processing machines, without the written approval of the publisher. 2 June 2009 DWA Rules and Standards

5 Foreword Wastewater contains a large amount of heat which, using modern heat pump technology, can be employed to heat buildings. The potential of this renewable energy source is huge. Using wastewater heat we could in terms of availability heat 10% of all the buildings in Germany. Due to the proportions of process and/or hot water, wastewater has a comparatively high temperature. Even in winter, the temperatures of the wastewater in the sewer or at the wastewater treatment plant are, as a rule, between 10 C and 15 C, and are thus significantly warmer than the outside air. Wastewater is therefore a low-cost heat source for heat pumps for heating buildings. In wastewater heat utilisation, waste heat is recovered, and at the same time, water bodies are relieved of thermal pollution. Wastewater heat utilisation contributes to energy and resource conservation and reduces CO 2 emissions. Wastewater also contains potential energy. Its economic employment requires considerable height differences, so the utilisable potential is limited to power production. The idea of wastewater heat utilisation is not new: in 1982 a first German pilot plant was constructed in the Salemer Pfleghof, a community centre with cultural exhibition rooms in Esslingen. The overall project was funded by the then Federal Ministry of Research and the operation was scientifically supported for several years. In 1983, a heat pump system was put into operation in Berlin, which used municipal wastewater as a heat source. It originally had a heat output of 1.5 MW, which was later increased to 2 MW. In Basel, wastewater from the sewer has been used for space heating and shower water heating in the changing rooms of a sports complex since 1985 with satisfactory results. Since then, more than seventy such plants have been built in Switzerland. Due to rising energy prices on the one hand, and the technological progress in the field of heat pumps and heat exchangers on the other, the utilisation of wastewater heat is becoming increasingly attractive from an economic point of view. Given the right parameters, plants for wastewater heat utilisation are already economically competitive compared to fossil fuel heating systems. With the right planning and execution, they do not present any disadvantages either for the drainage system or the wastewater treatment. This fact, along with the practical experience gained from installed systems, supplemented by the results of current research from Switzerland and Germany, have led the DWA to develop an Advisory Leaflet on the subject Energy from wastewater. DWA Rules and Standards June

6 Authors This Advisory Leaflet was compiled by the DWA working group ES-1.8 Einbauten Dritter im Kanal [Third party installations in the sewer] of the DWA specialist committee ES-1 Grundsatzfragen/Anforderungen [basic issues/requirements] and was coordinated with the main committee HA-KA Municipal Wastewater Treatment. Further coordination was carried out with the Swiss water association Abwasser- und Gewässerschutzfachleute (VSA) and the Austrian water and waste management association Wasser- und Abfallwirtschaftsverband (ÖWAV). The DWA working group ES-1.8 Einbauten Dritter im Kanal [Third party installations in the sewer] is made up of the following members: BRUNE, Peter BUTZ, Jan HENZE, Michael HERWIG, Wolfgang GELHAUS, Christian KASTNER, Hans-Jürgen KOBEL, Beat MÜLLER, Ernst. A. SEIBERT-ERLING, Gerhard STODTMEISTER, Wolfram STUCKI, Beat UHRIG, Thomas WALLSTEIN, Dieter ZIMMERMANN, Gerold Dipl.-Ing., Saarbrücken Dr.-Ing., Stuttgart Dipl.-Ing., Seligenstadt Dipl.-Ing., Leverkusen Dipl.-Ing., Ingolstadt Dipl.-Ing., Brake Dipl.-Ing., Bern (CH), (Speaker) Dipl.-Geogr., Zurich (CH) Dr.-Ing., Kerpen Dipl.-Ing. (FH), Berlin Dipl.-Ing., Langnau (CH) Dipl.-Ing., Geisingen Dipl.-Ing., Recklinghausen Dipl.-Ing., Essen The following guests contributed: ERNST, Helmut GREDIGK-HOFFMANN, Sylvia KLINGER, Horst MÜLLER, Karsten RICHTER, Beate ROEDIGER, Markus ROMETSCH, Lutz Dipl.-Ing., Frankfurt Dipl.-Ing., Aachen Dipl.-Ing., Stuttgart Dr.-Ing., Aachen Dipl. Ing. (FH), Singen Dr.-Ing., Stuttgart Dr. rer. oec., Gelsenkirchen Project organiser within the DWA Head Office: BERGER, Christian Dipl.-Ing., Hennef Department Wastewater and Water Protection 4 June 2009 DWA Rules and Standards

7 Contents Foreword... 3 Authors... 4 List of Figures... 8 List of Tables... 8 User Note... 9 Introduction Scope Terms Definitions Abbreviations and Symbols References Types of Energy Production Covered Fundamentals of Heat Recovery Heat Recovery Locations Possible Positioning of the Heat Recovery Plants Function of a Heat Pump System General Information on Heat Pumps Functional Principle of a Heat Pump Construction Types of Heat Pumps Wastewater as a Heat Source Heat Transfer Systems General Retrofitted Heat Exchangers Factory-Integrated Heat Exchangers Heat Recovery Plants Positioned Outside of the Sewer Potential Applications and Limitations Conditions Based on the Provisions of the Standards DWA-A 125 and DWA-A Groundwater Pollution Control Installation Requirements for Heat Recovery Plants in the Sewer Installation Requirements for External Heat Recovery Plants with Bypass Heat Consumers Dimensioning of a Heat Recovery Plant Preliminary Examinations Heat Available Initial Situation Forecast Bivalent Plants Heat Requirement of Buildings DWA Rules and Standards June

8 6.4 Choice of Dimensioning Heat Output Design of the Heat Exchanger Physical Basis Formation of Sewer Film Variation of the Flow Rate and Periodic Flushing Corrosion, Abrasion Heat Pump, Buffer Storage Space Requirement Effects of Heat Recovery Plants on the Drainage System and the Wastewater Treatment Plant Conditions for the Installation of the Heat Exchanger in the Sewer (Hydraulic/Constructional) Influence of the Heat Recovery on the Drainage System Influence of the Heat Recovery on the Wastewater Treatment Plant General Temperature Balance and Profile in the Sewer Calculation of the Changed Wastewater Temperature in the Inlet to the Wastewater Treatment Plant (simplified) Calculation of the Changed Wastewater Temperature in the Inlet to the Wastewater Treatment Plant (detailed) Effects on the Cleaning Capacity of a Wastewater Treatment Plant Climate and Resource Protection General Basic Principles for the Calculation of Energy and CO 2 Balances Water Pollution Control Economic Viability General Basic Principles for the Calculation EEWärmeG [Renewable Energies Heat Act] Assessment Construction and Operation Installation of the Heat Recovery Plant Wastewater Drainage Operational and Occupational Safety After the Installation Shaft Construction Works Construction or Renewal of a Sewer Section Operation, Service and Maintenance Occupational Safety Integral Approach for the Implementation of Wastewater Heat Utilisation Plants General Initiative from Municipalities, Sewer System Operators or Building Contractors Initiative through Municipalities or Sewer System Operators Inquiries from Building Contractors Determination of Suitable Locations by the Municipalities or Sewer System Operators Long-Term Implementation of the Full Potential Using Energy Master Plans Project-Based Approach with Technical Discussion Feasibility Study Autonomous Implementation or Contracting Contractual Arrangements June 2009 DWA Rules and Standards

9 13 Electricity Generation from Potential Energy General Calculation Parameters Hydropower Utilisation Techniques Turbine Hydrodynamic Screw Water Wheel Potentials in Wastewater Collection Example Appendix A (informative) Example of an Agreement on Wastewater Heat Utilisation Laws and Regulations Technical Rules DIN Standards DWA Rules and Standards Other Technical Rules Literature DWA Rules and Standards June

10 List of Figures Figure 1: Heat utlisation Figure 2: Heat recovery locations Figure 3: Schematic representation of the different construction types of heat pumps Figure 4: Course of the monthly mean temperatures throughout the year, measured at a wastewater treatment plant Figure 5: Examples of retrofitted heat exchangers Figure 6: Schematic representation of a heat recovery and utilisation plant Figure 7: Sewer with integrated tube bundle heat exchanger Figure 8: Sewer with integrated capillary tube mat in the bottom half of the pipe Figure 9: Sewer with heat exchangers lengthwise Figure 10: Externally positioned heat recovery plant with shell and tube heat exchangers Figure 11: Externally positioned heat recovery plant with underground intake works with screening stage, conveyor and screenings and wastewater return Figure 12: Double-pipe heat exchanger positioned in the bypass Figure 13: Free flow plate heat exchanger for pre-screened raw sewage or treated wastewater (wastewater treatment plant) Figure 14: Energy flow diagram of a heat pump based on 1 m 3 of wastewater which is cooled by 1 kelvin Figure 15: Typical daily discharge curve for dry weather in a medium-sized sewer system in Germany (ca. 50,000 inhabitants) Figure 16: Diagram COP heat pump Figure 17: Ringermatte Zwingen CH Figure 18: Heat supply Binningen CH Figure 19: Relative space heating requirement in relation to the outdoor and wastewater temperature and relative coverage of the heat pumps Figure 20: Relative heat exchanger output before and after flushing of the biofilm Figure 21: Heat-exchange processes in the sewer pipe Figure 22: Soil temperature in relation to depth over the course of a year Figure 23: Dependence between aerobic design sludge age and design temperature for different safety factors Figure 24: CO 2 balances of wastewater heat utilisation in comparison to fossil fuel heating systems Figure 25: Eco-balance of a heat pump with wastewater heat utilisation from raw sewage with an electricity mix of a gas and steam power station (GuD) Figure 26: Water wheel in the outlet of the wastewater treatment plant Warendorf Figure 27: Efficiency curve of the water wheel from Warendorf List of Tables Table 1: Advantages and disadvantages of various heat recovery locations Table 2: Energy content of fossil energy carriers Table 3: CO 2 emissions factors June 2009 DWA Rules and Standards

11 User Notes This Advisory Leaflet has been produced by a group of technical, scientific and economic experts, working in an honorary capacity and applying the rules and procedures of the DWA and the Standard DWA-A 400. Based on judicial precedent, there exists an actual presumption that this document is textually and technically correct. Any party is free to make use of this Advisory Leaflet. However, the application of its contents may also be made an obligation under the terms of legal or administrative regulations, or of a contract, or for some other legal reason. This Advisory Leaflet is an important, but not the sole, source of information for solutions to technical problems. Applying information given here does not relieve the user of responsibility for his own actions or for correctly applying this information in specific cases. This holds true in particular when it comes to respecting the margins laid down in this Advisory Leaflet. Introduction Wastewater heat utilisation is employed for heating buildings and for water heating. Larger individual buildings or district heating networks with several buildings are especially suited. Wastewater heat utilisation is also ideal for heating swimming pools, for drying sewage sludge and given the right temperature conditions for commercial applications. The lower the temperature level of the heat recipients is, the more efficiently the heat pumps are able to operate. The heat pumps can also be used for cooling purposes, e.g. for commercial refrigeration, or in summer for space cooling. Here, the heat pump acts in reverse as a refrigerating machine. In order to be able to use heat from wastewater for space heating and water heating, a heat pump is required, which raises the heat to a higher temperature level. Using wastewater as a heat source, heat pumps achieve effective temperatures of up to 70 C. In combination with a boiler, they can even be employed where higher temperatures are required. The combination of heat pump and boiler also has other benefits: increased security of supply and improved economic efficiency. In addition, in areas served with natural gas, the heat pump can be coupled with a block heating works (BHW) which, alongside power for operating the heat pump, also generates waste heat at a higher temperature level. For very large projects with a heat output of 2.5 MW and over, heat pumps can be used which reach a temperature level of 90 C. In all cases, however, a sufficient amount of heat from wastewater needs to be available in the locality. The heat can be taken from the wastewater in the building itself, the sewer or the wastewater treatment plant. The first option is not examined here because it concerns building-internal heat recovery. The use of the sewer or the wastewater treatment plant, on the other hand, concerns sewage disposal and therefore falls within the scope of this Advisory Leaflet. Based on the statutory provisions, requirements for discharges into water bodies are determined against the background of water management conditions (water quality etc.). Heat utilisation in the sewer should not lead to a reduction in the required treatment capacity in the wastewater treatment plant. 1 Scope According to EN 752, Section Sustainable use of energy, the drainage system has to be energetically optimised over its entire useful life: The design and operation of the drain and sewer system shall, so far as is practical, minimise the use of energy over the life of the system. The Advisory Leaflet DWA-M 114 Energy from wastewater thermal and potential energy describes the aspects of energy production from wastewater systems with regard to design, construction and maintenance. The focus is on heat production from drains and sewers. An overview of the use of the potential energy which is also contained in the wastewater is provided by Section 13. Since so far in Germany there is little experience and knowledge of the use of hydro-electric plants within the sewerage for the utilisation of the energy potential, a current pilot project is examining the extent to which this potential can be used for generating electrical energy, and if this is feasible from an economic point of view. One focus is on the effects of energy production plants on the wastewater treatment plant downstream from the drainage system. The experience already provided by the guidelines in Switzerland and Germany has been incorporated in the Advisory Leaflet. One section of the Advisory Leaflet deals with the economic viability of such plants. DWA Rules and Standards June