Sökande Kunliga Tekniska Högskolan, KTH

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1 ANSÖKAN OM FORSKNINGSSTÖD Datum Dnr 1 (11) Projektnr Sökande Företag/organisation Organisationsnummer Kunliga Tekniska Högskolan, KTH Institution/avdelning Postgiro/Bankgiro/Bankkonto Energiteknik/ Avd. Tillämpad Termodynamik och Kylteknik PG: , BG: Postadress Brinellvägen 66 Postnummer Ort Länskod Kommunkod Land Stockholm Sverige Projektledare (förnamn, efternamn) Björn Palm Telefon E-postadress bpalm@energy.kth.se; Eventuell medsökande (ange organisation) Danfoss A/S, Lars Finn Sloth Larsen Projektet Ansökan avser nytt projekt Fax Webbplats Projekttitel (på svenska) Kost och energi-optimering av ångkompressionssystem Fortsättning på tidigare projekt, ange projektnummer: Projekttitel (på engelska) Cost and energy efficiency optimization of vapor compression systems Sammanfattning (på svenska). Sammanfattningen skall omfatta max 250 ord och skall skrivas både på svenska och på engelska. Sammanfattningen skall skrivas så att den i ämnet oinvigde med lätthet förstår projektets innehåll och syfte. Detta projekt är finansierat till 100% utanför Effsys, via en industridoktorand på Danfoss i Danmark. Projektet avser utveckling av en metod att systematiskt analysera tänkbara utföringsformer av kyl- och värmepumpsystem för att finna bästa balans mellan kostnad och energieffektivitet. Detta ska uppnås genom att använda ett i projektet utvecklat beräkningsverktyg, vilket kan uppskatta skillnader i kostnad och prestanda för systemet vid val av olika systemlösningar och olika komponenter. I första hand kommer värmepumpar för enfamiljshus att studeras, men metoden ska kunna tillämpas även för andra typer av värmepumpande system. Sammanfattning på engelska enligt ovan (max 250 ord). This project is financed to 100% outside of Effsys, through Danfoss financing an industry-ph.d. student. Development of a method to systematically analyze refrigeration and heat pumping tasks to find the Pareto front of cost and energy optimal system solutions. This being achieved by utilizing the system layout and the individual component efficiency as optimization variables. Focus application is residential heat pumps, emphasizing low refrigerant charge technology. Enskilt projekt Forskningsprogram, ange vilket: EFFSYS+ Datum för projektstart Tidpunkt då projektet beräknas vara genomfört STEM038 ver.n-1.1, Sekretariatet EFFSYS+ Institutionen för Energiteknik Avdelningen Tillämpad termodynamik och kylteknik Kungliga Tekniska Högskolan Stockholm Besöksadress Brinellvägen 68 Telefax E-post Effsysplus@energy.kth.se

2 2 (11) Totalt sökt belopp 000 kkr

3 3 (11) Motivering; Energi-/miljö-/näringslivsrelevans, max 250 ord. Ange koppling till resultat från tidigare genomfört program eller projekt. The growing awareness of global warming has driven legislation and customer demands towards more energy efficient and environmentally friendly solutions. This challenges the traditional way of building heating and refrigeration systems adopted by the HVAC&R industry, because higher energy efficiency is required by using a smaller refrigerant charge. Minimization of the refrigerant charge is necessary to reduce the use of environmentally hazardous refrigerants or of substituting them with environmental friendly but flammable or toxic refrigerants. The residential heating and refrigeration systems currently on the market are not designed to match these requirements. Hence the introduction of reduced charge technologies as well as approaches to increase energy efficiency is necessary. This however yields numerous new challenges and will therefore lead to major changes in system and component design. The focus of this project will be on residential heat pump systems, where the influence of reduced charge on cost and energy optimal solutions will be analyzed. Though a focus application is chosen, it is however the aim to develop a generic top-down approach to systematically analyze a heat pumping or refrigeration task, filter out unfeasible solution approaches and finding cost and energy efficiency optimal system, subsystem and component solutions. Bakgrund; vad har gjorts tidigare?, vad är nytt i detta projekt?, forskargruppens verksamhet?, samarbeten? etc, max 1 A4-sida Project Description There are two major drivers for technological changes in heat pump systems, namely end user requests and legislation. The end users of heat pump systems have during the recent years gained an increased awareness of global warming; combined with increasing energy prices this has brought their attention to energy efficiency. Further improvements to the indoor comfort are another point widely requested. In the interest of reducing global warming in the European Union new legislation and standards are setting limits to the energy use in refrigeration systems and heat pumps Error! Reference source not found.. International agreements already led to regulations regarding the usage of fluorinated greenhouse gases Error! Reference source not found. which are expected to be augmented by further restrictions on allowed types and amounts of refrigerants. Low charge systems offer a promising approach to meet the increasing restrictions on the use of refrigerants. From previous work it is however known that reducing the charge introduces new challenges, since without an appropriate system and component design the system performance can be affected negatively Error! Reference source not found.. An example is given in Error! Reference source not found., showing that the introduction of heat exchangers with low internal volume can lead to subcooling variations which reduces system efficiency. Various changes in the overall system design are possible to prevent these variations. For example a charge receiver could be used, which however again increases system charge. Alternatively an internal heat exchanger could be implemented which counteracts subcooling variations a component which in a residential heat pump with traditional refrigerant and heat exchangers is of little use, within the context of charge reduction however offers a high improvement potential. Changes in the overall system design and the introduction of energy efficient technologies like capacity controlled compressors, distributing valves or advanced control algorithms increase the variety of possible system solutions. It is further increased by taking into account trade-offs between different components. Microchannel heat exchangers (MCHX) are a popular example for heat exchangers with low internal volume. Besides reducing refrigerant charge a MCHX provides the same efficiency as a traditional heat exchanger at reduced size, weight and material costs Error! Reference source not found.. One way of reducing system costs while keeping up the same system performance is therefore to replace the traditional heat exchangers with the less costly MCHX. Alternatively bigger MCHX with higher efficiency can be used so that instead another component in the cycle can be exchanged with a less efficient and cheaper one - an approach that could potentially lead to a more competitive solution. To find the best solution, considering both energy efficiency and costs, among the vast number of possibilities is not straightforward. Even if all possible solutions were known a priori, the result of the comparison would depend on the conditions under which it is made. These conditions are defined by extrinsic and intrinsic characteristics of the heat pumping task. The extrinsic characteristics specify the ambient conditions under which the system operates, such as outdoor and indoor temperatures, capacity, sizes etc. The intrinsic

4 4 (11) characteristics describe component and system-inherent features, such as compressor efficiency, the need of superheated vapor at compressor inlet or the occurrence of mal-distribution in the evaporator etc. To perform an exhaustive and thorough analysis it is necessary to develop a framework in which the relevant knowledge can be congregated and formalized to enable a structured evaluation, optimization and decision process. This framework is intended for analyzing the impact of changes in legislation, customer request, and the introduction of new technology for an application such as a residential heat pump. It should however also be applicable for assessing other heating and refrigeration tasks. The objective of this project is therefore two-fold, 1) to develop a structured framework whereby the Pareto front of cost and energy optimal solutions as indicated in Fig. 2 for a given heating or refrigeration task can be found, 2) to use this framework to make a technological assessment of the optimal front of solutions for residential heat pumps taking low charge and high efficiency technologies into account. Hypotheses It is possible with little loss of optimality to split the optimization of the vapor compression system designs in two separate problems; optimization of cycle layout and optimization of the component selection given the cycle layout. It is possible to sufficiently describe the requirements for a heat pumping task by using extrinsic and intrinsic characteristics such that, given a performance criterion which evaluates cost and energy efficiency, to single out the optimal cycle layouts. It is possible, provided the vapor compression cycle layout, the relevant component characteristics and prices, to evaluate the Pareto front of cost and energy optimal component selection for the given cycle layout. It is possible to develop a procedure that does this in a structured way. Mål; Ange enkla, tydliga och mätbara mål i exempelvis kwh, max 250 ord. Scientific goal To establish an optimization methodology for finding cost and energy optimal vapor compression system layouts from a large number of possible solutions. The goal of the optimization is to find the Pareto optimal front as indicated by Fig 2. To contribute with novel system or component layouts improving the efficiency of low refrigerant charge residential heat pumps. To derive novel mathematical models which capture the behavior of low charge vapor compression systems (e.g. microchannel heat exchangers). These models will further be used to investigate the impact of low refrigerant charge on the overall system performance. Developmental goal To contribute with detailed knowledge and understanding of the focus application residential heat pumps. To contribute with in depth understanding of low refrigerant charge technology. To establish an overview of technical possibilities and challenges and point out optimal system and component solutions. To develop a methodology that can be used to systematically optimize a heat pump or a refrigeration system. On a long horizon it could possibly lead to a software tool that can support product development, sales and marketing. Commercial targets Danfoss is a manufacturer of components for HVAC&R systems with the reputation and ambition for being an innovative force in improving energy efficiency. In a growingly complex world it is necessary to evaluate a high number of technical ideas and solutions and isolate the ones that offer the highest

5 5 (11) commercial potential. This structured decision making process is mandatory for an efficient utilization of the company resources and must be based on a solid technical foundation. The long-term objective of the project is therefore to establish the knowledge and competence to support the evaluation of changing markets and new technologies for their challenges and potential. The market for residential heat pumps and refrigeration is highly competitive. It is therefore crucial to be first to market with new products to gain a high market share. The results of this project are expected to support sales, marketing and product development in introducing the right products at the right time.

6 6 (11) Genomförande, max 250 ord. Method & Scientific Content The framework should be able to efficiently sort out infeasible solutions from a vast space of possible cycle layouts, and subsequently enable a detailed comparison of a small number of relevant system solutions. The framework is expected to consist of four major steps. The explanations and examples given below are based on the task of residential heat pumps. 1) Characterization of the task Basis of the analysis is a description of the extrinsic and intrinsic characteristics. To determine the extrinsic characteristics information regarding the heating requirements and the ambient conditions under which the system operates must be understood. Therefore information like load profiles, ambient conditions i.e. temperature and humidity should be at hand. This information can be found in standards for indoor climate Error! Reference source not found., in application qualification standards (Error! Reference source not found., Error! Reference source not found.) and in metrological databases. The intrinsic characteristics, i.e. mal-distribution and pressure drop Error! Reference source not found., are determined by the cycle layout, the control strategy, the technical design of the system and its components. Many of these intrinsic characteristics are already understood and can be found in the literature referred to in the state of art. 2) Constraining the solution space There exists a vast number of ways to layout the vapor compression cycle, from simple to multi stage cycles with arbitrary many stages and hence arbitrary many components. In Error! Reference source not found. is presented a matrix of known cycles that can be used as base of this investigation. The reason for making the cycle more complex is typically to achieve higher energy efficiency. However for all applications there exist limits for the price the customers are willing to pay even if the performance would be extremely high. From a commercial point of view it is therefore uninteresting to investigate solutions which exceed a certain complexity/cost level. By developing a cost index which roughly represents the cost range of a given cycle, it is possible to prune a large number of commercially uninteresting solution away at an early stage. 3) Optimization of cycle layout In order to provide a first estimate of the potential system energy efficiency for the selected cycles, simulations at a high abstraction level must be performed. An example is presented in Error! Reference source not found., where a basic thermodynamic cycle computation is performed to evaluate the system performance at fixed conditions. This approach can be extended by taking into account the dominating extrinsic and intrinsic characteristics (Error! Reference source not found., Error! Reference source not found., Error! Reference source not found.). These characteristics need to be implemented in the model in a formalized way, possibly as a range for the parameters of components and operating conditions. For all cycle layouts the efficiency range can then be computed at the extreme points of the parameter range. Mapping the cost index over this efficiency range allows identifying the front of potentially best cycle layouts. 4) Optimization of component selection Based on the result of the previous step, the most promising set of cycle layouts Solution 1 Solution 2 are selected for a detailed study of the trade-off between the system efficiency Solution 3 versus the component efficiency. For this purpose a more precise and detailed description of the intrinsic and extrinsic characteristics is needed. Besides a suitable measure Fig. 2: Pareto for the optimal energy front of differen performance system must solutions. be defined, e.g. according to the standards Error! Reference source not found. or as the annual energy consumption Error! Cost Energy efficiency

7 7 (11) Reference source not found.. Models with an appropriate complexity level must be derived for the system (Error! Reference source not found., Error! Reference source not found.) and components (Error! Reference source not found., Error! Reference source not found.), such that the necessary characteristics can be represented. An example can be found in Error! Reference source not found., where the complexity level of heat exchanger models is discussed. Dimensional parameters, such as size and efficiency of the components, can be used as optimization variables. Utilizing these in optimization procedures, as discussed in the state of the art, the cheapest way of reaching a certain efficiency can be computed. The modeling and optimization process should result in a diagram which allows identifying optimal system solutions for different regions of efficiency, this front of optimal solution is known as the Pareto front, indicated by the red curve in Fig. 2. Complete plan for the course of the education and project, divided into phases (See also Gantt chart) The following plan is divided into project phases of approximately half years 1) Characterization of the task & Constraining the solution space (7 months) - Detailed problem formulation and study plan. - Comprehensive state of the art analysis for the heat pumping task. - Gaining practical experience and collecting cost information resulting in solution matrix. PhD Courses: - Business course for Industrial PhD Program, starting 20th September - Heat pumps, systems and heat sources, KTH Technical Report 1: Survey of low charge in residential heat pumps 2) Optimization of cycle layout I - Modeling & Simulation (6 months) - Formalizing intrinsic characteristics. - Thermodynamic cycle modeling resulting in cost / energy efficiency plot. PhD Courses: - Energy Systems and models, KTH - Theory and Practice in System Analysis, KTH Conference Paper 1: Cycle analysis with regard to system-intrinsic characteristics 3) Optimization of cycle layout II Validation (4 months) - Experimental validation by comparison of simulations with existing solutions. PhD Courses: - Problems of Advanced Optimization, AAU Conference Paper 2: Residential heat pumps: Cost and performance assessment of various cycle layouts 4) Optimization of component selection I Component and system modeling (7 months) - Establishing of significant performance and cost criteria. - Development of numerical models. - Validation of component models. Journal Paper 1: Challenges & potential of low-charge heat pump systems 5) Optimization of component selection II Optimization (6 months) - Formulation of optimization problem & method selection.

8 8 (11) - Simulation and optimization resulting in Pareto front of optimal solutions. Conference Paper 3: Cost and energy efficiency optimization of heat pump systems 6) Methodology verification (6 months) - Experimental validation of selected results. - Evaluation of methodology. - Writing of the PhD thesis Journal Paper 2: A top-down approach for system analysis and optimization

9 9 (11) Kostnader KALENDERÅR Lönekostnader Laboratoriekostnad Datorkostnad Utrustning Material Resor Övriga kostnader Ev förvaltningskostnader SUMMA Finansiering inkl. samfinansiärer Projektets totala kostnad Projektets totala kostnader per år % av heltid Andel i kronor och procent av projektets totala kostnader/år FINANSIÄR År 2011 År 2012 År 2013 År 2014 År Total (%) Energimyndigheten Danfoss SUMMA Detta projekt är i sin helhet i vissa delar lika med ansökan till annan myndighet, ange vilken: Sökt stöd för dyr utrustning (Vetenskapsrådet, Wallenbergsstiftelsen e.d.) Gäller endast högskola. Namn på doktorand Gunda Mader Namn på doktorand Namn på doktorand Namn på doktorand Övriga samarbetspartners (ange organisation och namn) Danfoss A/S, Lars Finn Sloth Larsen Nordborgvej 81 DK Nordborg Lars.Larsen@danfoss.com

10 10 (11) Resultatredovisning (ange här om resultatet kommer att redovisas på något ytterligare sätt än det obligatoriska, se information). Arbetet inom projektet kommer att redovisas tillsammans med andra delprojekt inom Effsys+. Resultat kommer även att redovisas internt på Danfoss, i vetenskapliga publikationer etc. och så småningom också i en doktorsavhandling. Bilagor Intyg med underskrifter från samfinansiärer Gantt-schema Övriga bilagor Datum Datum 28/11, /11, 2010 Behörig firmatecknares (prefekt motsv.) underskrift Projektledarens underskrift Namnförtydligande, titel och telefon Professor Björn Palm Namnförtydligande och titel Professor Björn Palm

11 Gantt schema (Se Genomförande) Fas 1 Fas 2 Fas 3 Fas 4 Fas 5 Fas