DEPARTMENT OF TECHNOLOGY AND BUILT ENVIRONMENT TECHNOLOGICAL AND ECONOMIC EVALUATION OF DISTRICT COOLING WITH ABSORPTION COOLING SYSTEMS IN GÄVLE (SWEDEN) Elixabet Sarasketa Zabala June 2009 Master’s Thesis in Energy Systems uuir Master Programme in Energy Systems Examiner: Ulf Larsson Supervisor: Åke Björnwall Preface This investigation, as final Thesis Project of Master in Energy Systems (University of Gävle), was started to carry out in February, in collaboration with the company Gävle Energi AB. Many people have been involved answering my questions, providing me with information and so forth; some of those are mentioned below. First of all, I would like to thank Åke Björnwall, my supervisor at Gävle Energi AB, very much for his attention, help and support. His knowledge, comments, guidance and advices have been essential for the development of my work. Needless to say that I have learnt a lot from him. Secondly, I would like to thank the rest of workers at Gävle Energi AB, who have done everything they can to help me, in addition to make pleasant my stay in the company. I would also like to thank Ulf Larsson at the University of Gävle for his help. Furthermore, I am very grateful for all information I have received from other companies. Finally, I do not forget the invaluable support of my mother, Rosa, during all my studies. No one mentioned, no one forgotten. Gävle, June 2009 Elixabet Sarasketa Zabala Abstract Gävle Energi AB is a company which produces electricity as well as heat that is delivered through a district heating network in the municipality of Gävle. Apart from that, as cooling demand is large when seen from a global perspective, at present it is building a district cooling network based on refrigerant compressor technology with the idea of replacing less efficient individual HVAC systems in the city center. High electricity prices lead to reduce its use as far as possible, so it is also needed to consider absorption systems as cooling technology. This way, the main aim of this thesis is to analyze possible benefits with the use of heat driven absorption chillers compared with conventional vapour compressor chillers. For carrying out this investigation, first of all background and literature study have been essential. As a result, information about cooling technologies, district energy and cogeneration plants is gathered in this work. The research is focused on three areas of the victinity of Gävle: city center, Kungsbäck and Johannesbergsvägen. In the first area, Gävle Energi AB might take the opportunity of using a new ORC plant in biomass based cogeneration system that Bionär is planning to build at LEAF, turning it into a trigeneration plant. So how bigger the installation should be (according to the expected cooling demand that has been calculated in the earliest steps) and the profits related to extra electricity production are estimated in this study, in addition to examine the absorption chillers to be introduced and their operational conditions. On the other hand, Mackmyra whisky factory, which is in Valbo nowadays, is going to build a new plant in Kungsbäck. Likewise, it is considering that extra steam might be produced to fire absorption chillers and fulfil the cooling demand of the hospital (Gävle Sjukhus), technological park (Teknikparken) and university (Högskolan i Gävle), which are located in this area. Like this, the same methodology as for LEAF has been followed for making decisions. Finally, there is Johannesbergsvägen area, where Johannes CHP plant is (a description of the plant is included in the Appendix) and which is runned by Gävle Energi AB. This plant is shut down in summer, as the demand for district heating is low, and hence, electricity production, from which the company makes a profit, is cut and restricted. A good solution to increase electricity output in warm periods is to introduce absorption cooling technology, as it is run on steam or hot water. Thus, Johannes could be the third trigeneration plant in Gävle that would supply Hemlingby shopping centers (which are located less than two kilometers far away from the production site) with cooling. Thus, the task has been also to decide on installations and gauge the profits. Next Table 0. gathers together costs, amount of heat that would be demanded to produce and accordingly generated electricity in each of the three production sites. It has been decided that double-effect chillers sets in the first two cases and single-effect hot-water fired absorption cooling machines in the last one might be introduced. Table 0. Costs of absorption cooling installations, extra heat to be produced for the absorption chillers and extra electricity output in the three studied sites PRODUCTION OPERATIONAL HEATING ELECTRICITY SITE &TOTAL INVESTMENT COSTS DEMAND PRODUCTION COOLING COST [SEK] [SEK/year] [MWh/year] [MWh/year] LOAD LEAF 22 627 000 4 753 485 17 977 4 135 21 385 MWh/year MACKMYRA 17 700 000 2 504 835 7 819 1 173 9 298 MWh/year JOHANNES 8 800 000 3 561 396 10 460 3 033 8 496 MWh/year Furthermore, explanations and calculations regarding distribution systems are presented, as these are also a component of district cooling systems. Nevertheless, they are not taken into consideration for final decisions, since necessary pumps and piping system would be the same in case of using vapour compressor chillers for cooling production. Lastly, it has been come to the conclusion that a sustainable energy system for Gävle for fulfilling the cooling demand can be the erection of district cooling networks with trigeneration plants by producing cooling in heat driven absorption cooling machines. Despite larger investment cost of absorption systems compared to compression ones, total costs after roughly five years are lower. Moreover, electric coefficient of performance is about 23% higher for the absorption cooling technology and there is a great electricity output too, which makes possible to reduce electrical loads, to use the biofuel in an effective way and, last but not least, to decrease global carbon dioxide emissions. TABLE OF CONTENTS CHAPTER 1. INTRODUCTION ..................................................................... 1 1.1. BACKGROUND ....................................................................................... 2 1.1.1. COOLING AND ITS PRODUCTION .................................................................... 2 1.1.2. GÄVLE ENERGI AB AND ITS PLANS FOR THE FUTURE................................ 3 1.2. PURPOSE .................................................................................................. 4 1.3. SCOPE....................................................................................................... 4 1.4. LIMITATIONS .......................................................................................... 5 1.5. METHOD .................................................................................................. 5 1.6. OUTLINE OF THE THESIS...................................................................... 6 CHAPTER 2. COOLING SYSTEM TECHNOLOGIES ................................ 8 2.1. REFRIGERANT COMPRESSOR INSTALLATIONS ................................ 10 2.1.1. COMPRESSOR AND SYSTEM EFFICIENCY ..................................................... 12 2.2. ABSORPTION COOLING INSTALLATIONS .......................................... 13 2.2.1. CONSIDERATIONS FOR DIMENSIONING ABSORPTION CIRCUITS............. 17 2.2.2. WORKING FLUID ............................................................................................... 18 2.2.2.1. WATER/ LITHIUM BROMIDE (H2O/ LiBr) .......................................... 19 2.2.2.2. AMMONIA/WATER (NH3/ H2O) ........................................................... 20 2.2.2.3. COMPARISON BETWEEN WATER/ LITHIUM BROMIDE AND AMMONIA/WATER SOLUTIONS.......................................................... 21 2.2.3. PRIMARY ENERGY ............................................................................................ 25 2.2.4. TYPES OF ABSORPTION CHILLERS ................................................................ 26 2.2.4.1. SINGLE-EFFECT ABSORPTION CHILLERS ....................................... 27 2.2.4.2. DOUBLE-EFFECT ABSORPTION CHILLERS ..................................... 28 2.3. REFRIGERANT COMPRESSOR TECHNOLOGY VERSUS ABSORPTION COOLING TECHNOLOGY ............................................ 30 CHAPTER 3. DISTRICT COOLING SYSTEM ............................................ 35 3.1. PRODUCTION ........................................................................................... 37 3.1.1. COGENERATION. BENEFITS WITH ABSORPTION COOLING ...................... 37 I TABLE OF CONTENTS 3.2. COOLING DISTRIBUTION SYSTEM....................................................... 39 3.2.1. PIPING NETWORK ............................................................................................. 39 3.2.2. MATERIALS FOR THE PIPES ............................................................................ 40 CHAPTER 4. PROCESS ................................................................................. 41 4.1. GATHERING OF INFORMATION ABOUT EXISTING INSTALLATIONS AND PRESENT SITUATION ..................................... 42 4.1.1. STEAM BOILERS AT LEAF AND KAPPA ........................................................ 42 4.1.2. BIOFUELED JOHANNES CHP PLANT .............................................................. 44 4.1.3. MACKMYRA .....................................................................................................