Dissertationen zum Thema „District heating driven cooling“

Absorption cooling system driven by district heating network is relized as a smart strategy in Sweden. During summer time when the heating demand is low, the excessive hot water can be directly sold to drive absorption chillers instead of decreasing its production. In addition, this is also one answer to satisfy the cooling demand in more environmentally way since currently only around 26% of cooling demand in Sweden is satisfied by district cooling, the rest is fulfilled by individual air conditioning. Realizing this potential, the purpose of this study is to examine the returning hot water temperature in the district heating network with supply temperature of 70°C and also the effect to the absorption chiller’s COP. Through the simulation result, it is found out that the lowest possible returning water temperature is 55 °C at COP 0,69 with heat rejection (re-cooling) temperature water at 22 °C. This implies that the desired returning hot water temperature of 47 °C cannot be achieved. The lower returning hot water temperature is preferable since it gives the district heating network benefit in term of less distribution pump work, and energy recovery for the condensation process at central heating plant.

This independent degree project has been implemented on behalf of FVB Sverige AB in collaboration Sundsvall Energi AB with the initial purpose of mapping manufacturers of hot water driven absorption chillers. After that, several technical solutions are examined to manage the peak load of a theoretical object which cannot produce the cooling power required with only an absorptions chiller, due to limitations in the district heating supply. The market study has shown that the supply of absorption chillers with drive temperatures of 70–90˚C is limited to a few manufacturers. World Energy offers a unit with drive temperatures of 70 ˚C and efficiency (COP) of 0,4. Due to limitations of district heating flow, a unit with drive temperature of 85 ˚C and efficiency of 0,77 is chosen. The technical solutions are dimensioned for a building with a peak power of 264 kilowatt, where the required peak load ranges from 31 to 39 kilowatt. The technical solutions examined are a solar collector system, tap water heat exchanger, and a conventional compressor driven chiller. The solar collectors are dependent on location but use no refrigerants that are affected by the F-gas regulation. The tap water solution consumes large flows of tap water, but the installation is simple. The conventional chiller is not location dependent but uses ozone degrading refrigerants and has a high cost of operation. From an economic perspective the technical solutions are equally profitable with a present net value of approximately 500 000 SEK and pay-back of 13 years. The examination has also shown that the present value is one million crowns in sales of heat and building after a ten-year period. In conclusion the conventional chiller has the biggest prerequisites to be used as a standardised solution for buildings with a bigger cooling load. Based on the technical and economical conditions.

Increasingly intensive efforts are being made to enhance energy systems via augmented introduction of renewable energy along with improved energy efficiency. Resource constraints and sustained high fossil fuel prices have created a new phenomenon in the world market. Enhanced energy security and renewable energy development are currently high on public agenda worldwide for achieving a high standard of welfare for future generations. Biomass and municipal solid waste (MSW) have widely been accepted as important locally-available renewable energy sources offering low carbon dioxide (CO2) emissions. Concerning solid waste management, it has become a critical issue in Southeast Asia since the most popular form for waste disposal still employs open dumping and landfilling. While the need for a complete sustainable energy solution is apparent, solid waste management is also an essential objective, so it makes sense to explore ways in which the two can be joined. Electricity production in combination with energy recovery from flue gases in thermal treatment plants is an integral part of MSW management for many industrialized nations. In Sweden, MSW is considered as an important fuel resource for partially meeting EU environmental targets within cogeneration. However it is normally difficult to justify traditional cogeneration in tropical locations since there is little need for the heat produced. Similarly, MSW-fired cogeneration usually operates with low capacity during non-heating season in Sweden. Therefore, it is very important to find new alternatives for energy applications from waste, such as the implementation of thermally driven cooling processes via absorption cooling in addition to electricity production. The work presented herein concentrates first on an investigation of electricity generation from MSW power plants and various energy applications from waste in tropical urban areas. The potential for various types of absorption chillers driven by MSW power plants for providing both electricity and cooling is of particular interest. Additionally a demonstration and analysis of decentralized thermally driven cooling in district heating network supplied by low temperature heat from a cogeneration of MSW have been conducted. This study aims at developing the best system configuration as well as finding improved system design and control for a combination of district heating and distributed thermally driven cooling. Results show that MSW incineration has the ability to lessen environmental impacts associated with waste disposal, and it can contribute positively towards expanding biomass-based energy production in Southeast Asia. For electricity production, the proposed hybrid dual-fuel (MSW/natural gas) cycles feature attractive electrical efficiency improvements, leading to greenhouse gas emissions reduction. Cogeneration coupled with thermally driven cooling is a solution that holds promise for uniting enhanced sustainability with economic advantages. The system offers great opportunity for primary energy saving, increasing electrical yield and can significantly reduce CO2 emissions per unit of cooling as compared to compression chiller. The demonstration and simulation have also revealed that there is a potential with some modifications and improvements to employ decentralized thermally driven cooling in district heating networks even in temperate regions like Sweden. Thus, expanding cogeneration towards trigeneration can augment the energy supply for summer months in Europe and for year-round cooling in tropical locations.
QC 20110408

For a district heating company it is of importance to have an efficient and well performing system. A central part in the work to lower temperature levels in district heating networks is to acknowledge and improve cooling capability in substations. The aim of this thesis is to analyse substations in Polish district heating systems in order to identify reasons of poor cooling and to present suggestions of implementable measures. Furthermore, the economical saving potential from an improved cooling is evaluated. The analysis was carried out for two of the five Polish companies included in this report; Sydkraft EC Slupsk and MEC Koszalin. It was followed by two scenarios created for evaluation of improvement possibilities based on calculated financial savings from reduction of distribution heat losses and distribution pumping. The results show that there are significant improvement possibilities. From the carried out scenarios a saving potential between 15 000 to 20 000 PLN/substation is possible to achieve for selected worst substations, if their individual annual average cooling is set to 30°C. The analysis further shows that causes of poor cooling in substations are highly individual but points out that customer owned substations are represented in the majority of worst substations.

Astra Zeneca plant in Gärtuna has many compression cooling machines for comfort that consume about 11.7 GWh of electricity per year. Many of the cooling machines are old; due to the increase of production of the plant, cooling capacity was limited and new machines have been built. Now, the cooling capacity is over-sized. Söderenergi is the district heating plant that supplies heating to Astra Zeneca plant. Due to the strict environmental policy in the energy plant, last year, a bio-fuelled CHP plant was built. It is awarded with the electricity certificate system.

The study investigates the possibility for converting some of the compression cooling to absorption cooling and then analyzes the effects of the district heating system through MODEST optimizations. The effects of the analysis are studied in a system composed by the district heating system in Södertälje and cooling system in Astra Zeneca. In the current system the district heating production is from boiler and compression system supplies cooling to Astra Zeneca. The future system includes a CHP plant for the heating production, and compression system is converted to absorption system in Astra Zeneca. Four effects are analyzed in the system: optimal distribution of the district heating production with the plants available, saving fuel, environmental impact and total cost. The environmental impact has been analyzed considering the marginal electricity from coal condensing plants. The total cost is divided in two parts: production cost, in which district heating cost, purchase of electricity and Emissions Trading cost are included, and investment costs. The progressive changes are introduced in the system as four different scenarios.

The introduction of the absorption machines in the system with the current district heating production increases the total cost due to the low electricity price in Sweden. The introduction of the CHP plant in the district heating production supposes a profit of the production cost with compression system due to the high income of the electricity produced that is sold to the grid; it profit increases when compression is replaced by absorption system. The fuel used in the production of the future system decreases and also the emissions. Then, the future system becomes an opportunity from an environmental and economical point of view. At higher purchase electricity prices predicted in the open electricity market for an immediately future, the future system will become more economically advantageous.

 

 

This project presents a feasibility study and an investigation of the potential for low temperature district heating system in Västerås. The investigation treats integrations possibilities for 4GDH (4th Generation District Heating) in Kungsängens area in Västerås, which is undergoing a large-scale building-up and construction.  The study is conducted for the company Mälarenergi AB. The advantages of 4GDH technology are identified and analyzed, where energy effectiveness and economic benefits aspects were concluded. Problems with existing technology and higher cooling demand expectations drive 4GDH to be an interesting and necessary technology in the future. Four Different integration solutions between old and new networks are presented, analyzed and discussed. Quantitative analysis conducted where initial cost for the four technical solutions were estimated and compared. The results show that low temperature district heating could lead to reduction in the initial cost for the network by using PEX instead of steel as pipe material. The results show also that one solution using heat exchanger as exchange stations has the lowest cost between the four solutions. The results show that the cost for the retention flow that is linked with 4GDH stands for 20%-30% of the total cost. The importance of the retention flow pipe is investigated using two physical models in OpenModelica and Excel, where simulations were conducted. It is concluded that it is possible to provide Kungsängen area with low temperature district heating without having the retention flow pipe. Three parameters were identified to be critical which are, geographical placement of the consumers, pattern variation for the heat demand and heat systems installed inside consumer’s buildings. The results show also that it might be critical to have a variate and optimized supply temperature for the area, depending on the demand. The simulations of a fictive area that could present a future heat demand for Kungsängen area shows that a temperature of 55°C is satisfying during winter season where the demand is high and a temperature between 60-65°C must be available during spring/autumn seasons and specially during summer. The variation depends directly on the temperature drop through the supply pipes to the consumers. The temperature drop is directly linked with water velocity inside the pipes. The losses increase during summer nights when the heat demand is low which lead to low water velocities.

Domestic and industrial water demands are growing globally due to population growth and rapid economic development, placing increasing strains on water resources. Wastewater effluents generated from these and other activities impact the environment and are thus subject to tightening regulation. The focus of research and development in water treatment processes aims at both pollutant removal efficiency and cost of purification. Membrane distillation (MD) is a developing thermally driven technology capable of achieving extremely high environmental performance utilizing renewable energy sources to a high degree. District heating networks, and in particular those driven by biomass, represent an ideal heat supply for MD systems. This thesis presents a technoeconomic assessment of district heating driven MD for water purification in selected industrial applications. The study covers analysis of MD separation performance and the related costs from different district heating integration scenarios. The analyses are based on three types of semi-commercial MD modules, with experiments conducted at laboratory and pilot scales. The case studies include pharmaceutical residue removal from effluents of municipal wastewater treatment plant, wastewater purification in pharmaceutical industry, and ethanol concentration in bioethanol production plant. Full-scale simulation studies were carried out for the identified case studies based on the experimental data obtained from MD module along with process information gathered from the industries. Results from the pharmaceutical residue removal pilot trials showed very good to excellent separation efficiency for 37 compounds at feed concentrations ranging from ng/L to mg/L. From alcohol-water feeds, ethanol concentrations were increased from 5% to nearly 90%. Simulation studies revealed that district heating integration of MD systems is feasible. Costs per unit volume of purified water are higher than competing technologies, however the configurations enable enhanced environmental performance that would be difficult to achieve otherwise.
Kommunala och industriella vattenkrav växer globalt på grund av befolkningstillväxt och snabb ekonomisk utveckling, vilket ökar belastningen på vattenresurserna. Avloppsvatten från alla verk-samheter påverkar miljön och är därmed föremål för tilltagande reglering. Fokus i forskning och utveckling av vattenreningsprocesser syftar till att både öka effektiviteten i avlägsnandet av föroreningarna och att minska kostnaderna för detta. Membrandestillation (MD) är en ny termiskt driven teknik som kan uppnå extremt hög miljö-prestanda genom att den är effektiv och i hög grad kan drivas av förnybara energikällor. Fjärrvärmesystem, särskilt de som drivs av biomassa, utgör en idealisk värmeförsörjning för ett MD-system. Avhandlingen presenterar en teknoekonomisk bedömning av fjärrvärmedriven MD för vattenrening i utvalda industriella applikationer. Studien analyserar MD-systemets separations-prestanda och kostnader i olika fjärrvärmeintegrationsscenarier. Analyserna baseras på tre typer av semi-kommersiella MD-moduler, med experiment utförda på laboratorie- och pilotskala. Fallstudierna innefattar: borttagning av läkemedelsrester från avloppsvatten från kommunalt avloppsreningsverk; avloppsvattenrening i läkemedels-industrin; och uppkoncentrering i bioetanolproduktionsanläggning. Fullskaliga simuleringsstudier har utförts för fallstudierna baserat på experimentella data erhållna från MD-modulen och med processinformation som samlats in från industrin. Resultaten från försöken med läkemedelsrester visade mycket god till utmärkt separationseffektivitet för 37 föreningar vid förorenings-koncentrationer som sträckte sig från ng/liter till mg/liter. Vid uppkoncentrering av alkohol ökades etanolhalten från 5 % till nära 90 %. Simuleringsstudier visade att fjärrvärmeintegration av MD-system är möjlig. Kostnader per volym renat vatten är högre än konkurrerande teknik, men konfigurationerna möjliggör förbättrad miljöprestanda som skulle vara svår att uppnå på annat sätt.

This doctoral research has been carried out in the context of an agreement on joint doctoral research supervision between KTH Royal Institute of Technology, (Stockholm, Sweden), and Politecnico di Torino − PoliTo, (Turin, Italy). Erasmus Mundus Joint Doctorate, SELECT+ (Environomical pathways for sustainable energy services) program. QC 20170523

SLECT+ Erasmus Mundus Joint Doctoral Program

The aim of this thesis is to identify measures which should be taken in DH systems (DHSs) in order to contribute to the development of the DHSs and other energy systems (especially transport, industrial and power sectors) toward sustainability. Four business strategies were analysed: delivering excess heat from biofuel production industry to DHSs, conversion of industrial processes to DH, integration of biofuel production in DHSs and integration of DHdriven absorption cooling technology in DHSs. Delivering excess heat from biofuel production industry to DHSs was analysed with a focus on the biofuel production costs for four biofuel production technologies. Integration of biofuel production and integration of DH-driven absorption cooling technology in DHSs were analysed with a focus on Stockholm’s DHS, using an optimisation model framework called MODEST. When the conversion of industrial processes to DH was analysed, DHSs and industrial companies in Västra Götaland, Östergötland and Jönköping counties were used as case studies; a method for heat load analysis called MeHLA was used to analyse the effects on the local DHSs. The results showed that when considering biomass an unlimited resource, by applying the abovementioned business strategies DH has a potential to reduce global fossil fuel consumption and global GHG emissions associated with power, industrial and transport sectors. DH producers may contribute to the sustainable development of the  transport sector by buying excess heat from the biofuel production industry. This business strategy results in lower biofuel production costs, which promotes development of biofuel production technologies that are not yet commercial. Moreover, introduction of large-scale biofuel production into local DHSs enables development of local biofuel supply chains; this may facilitate the introduction of biofuel in the local transport sectors and subsequently decrease gasoline and fossil diesel use. Conversion of industrial processes from fossil fuels and electricity to DH is a business strategy which would make the industry less dependent on fossil fuels and fossil fuelbased electricity. DH may also contribute to the sustainable development of the industry by buying waste heat from industrial processes, since this strategy increases the total energy efficiency of the industrial processes and reduces production costs. Furthermore, DH has a possibility to reduce fossil fuel consumption and subsequently GHG emissions in the power sector by producing electricity in biomass- or waste-fuelled CHP plants. When the marginal electricity is associated with high GHG emissions (e.g. when it is produced in coal-fired condensing power (CCP)) plants, the reduction of the marginal electricity production (due to the conversion of industrial processes from electricity to DH and due to the conversion of compression cooling to DHdriven absorption cooling) results in higher environmental benefits. On the other hand, the introduction of biofuel production into DHSs becomes less attractive from an environmental viewpoint, because the investments in biofuel production instead of in CHP production lead to lower electricity production in the DHSs. The increased DH use in industry and introduction of the biofuel production and DH-driven absorption cooling production into the DHSs lead to increased biomass use in the DHSs. Because of this, if biomass is considered a limited resource, the environmental benefits of applying these business strategies are lower or non-existent.
Syftet med denna avhandling är att identifiera åtgärder som bör vidtas i FJV-system (FJVS) för att bidra till en hållbar utveckling av FJV och andra relaterade energisystem som transport, industri- och energisektorn. Fyra affärsstrategier är analyserade: att leverera överskottsvärme från produktion av biobränsle för transportsektorn, konvertering av industriella processer till FJV, integration av biobränsleproduktion för transportsektorn i FJVS och integration av FJV-driven absorptionskylteknik i FJVS. Att leverera överskottsvärme från produktion av biobränsle till transportsektorn analyserades med fokus på kostnader för fyra olika produktionstekniker. Integration av biobränsleproduktion till transportsektorn och integration av FJV-driven absorptionskylteknik i FJVS analyserades på Stockholms FJVS med optimeringsmodellen MODEST. När konvertering av industriella processer till FJV analyserades, användes FJVS och industriföretag i Västra Götaland, Östergötlands och Jönköpings län som fallstudier. Metoden MeHLA som används för analys av värmebelastning tillämpades för att analysera effekterna på de lokala FJVS. Resultaten från studierna visar att när biomassa anses vara en obegränsad resurs har FJV en potential att minska den globala konsumtionen av fossila bränslen och de globala utsläppen av växthusgaser som förknippas med transport-, industri- och energisektorn, for samtliga analyserade affärsstrategierna. FJV producenter kan bidra till en hållbar utveckling av transportsektorn genom användningen av överskottsvärme från produktion av transportbiobränsle. Den analyserade affärsstrategin ger lägre produktionskostnader för transportbiobränsle vilket främjar utvecklingen av produktionsteknik som ännu inte är kommersiell. Dessutom möjliggörs utveckling av lokala försörjningskedjor av transportbiobränsle på grund av den storskaliga produktionen av transportbiobränsle i lokala FJVS. Detta kan sedan underlätta införandet av transportbiobränsle i lokala transporter och även minska användningen av bensin och fossil diesel. Konvertering av industriella processer från fossila bränslen och el till FJV är en affärsstrategi som skulle göra FJV-branschen mindre beroende av fossila bränslen. Att använda spillvärme från industriprocesser ökar den totala energieffektiviteten i de industriella processerna och minskar produktionskostnaderna. Genom att dessutom öka FJV-användningen inom industriella produktionsprocesser och genom att konvertera eldriven kompressionskyla till FJV driven komfortabsorptionskyla, minskar säsongsvariationerna av FJV lasten, vilket leder till ett bättre utnyttjande av produktionsanläggningar för FJV. Om produktionsanläggningarna för baslast i FJVS är kraftvärmeverk, leder dessa två affärsstrategier till en ökad elproduktion i FJVS. När marginalproducerad el förknippas med höga utsläpp av växthusgaser (t.ex. när det produceras i koleldade kondenskraftverk), resulterar en minskning av den marginella elproduktionen (på grund av konvertering av industriella processer från el till FJV och på grund av konvertering eldriven kompressionskyla till FJV-driven absorptionkyla) i minskade globala emissioner av växthusgas. Om man däremot tittar på införandet av produktion av transportbiobränsle i FJVS är denna affärsstrategi mindre attraktiv ur ett miljöperspektiv. Orsaken till detta är att investering i produktion av transportbiobränsle istället för i kraftvärmeproduktion, leder till minskad elproduktion i FJVS. Den ökade FJV-användningen inom industrin och införandet av produktion av biobränsle för transportsektorn och FJV driven absorptionskylproduktion i FJVS leder till en ökad användning av biomassa i FJVS. När biomassa anses vara en begränsad resurs, är de miljömässiga fördelarna med att tillämpa dessa affärsstrategier relativt låga eller till och med obefintliga.

This PhD thesis is a demand led study taking into account changes in ambient conditions and power settings of a tri-generation power plant. Includes an evaluation tool for combined heat, cooling and power generation plant. The thesis is based on an overall technical-economic analysis of the tri-generation system, including: 1. Energy demand analysis and evaluation of actual tri-generation case studies. 2. Modelling of the prime mover (Gas Turbine, GT) 3. Modelling of the absorption cooling system, (LiBr/Water). 4. Economic analysis and evaluation of the entire tri-generation plant. Initially, the main effort is to carry out research concerning the energy demands of different actual cases. The research includes sourcing, collecting, classification and evaluation of the available information. The cases cover a wide range of economic life and the resulting data specifies the energy needs which the purposed tri-generation power plant needs to cover. The second part deals with the prime mover (namely the Gas Turbine, GT) modelling and simulation. The technical part of the assessment includes the Design Point (DP) and Off Design (OD) analysis of the GT. In other words, the performance analysis simulates different thermodynamic cycles (Simple, or with Heat Exchanger), and different configurations (one or two shafts). Also, the computer programming code is capable of simulating the effects of the use of different types of fuel, ambient conditions, part load conditions, degradation, or the extraction of power for district heating or for absorption cooling. The third part includes the simulation of the absorption cooling system alone and/or in co-operation with the prime mover. The simulation is based upon the premise that the original prime mover is replaceable. Finally, an evaluation methodology of tri-generation plants, is introduced taking into account, both technical facts and economic data -based on certain cases from Greek reality- helping the potential users to decide whether it is profitable to use such technology or not. The economic scene will include the basic economic facts such as initial cost, handling and operational cost (fuel prices, maintenance etc), using methodology based on Net Present Value (NPV). This thesis suggests several tri-generation technology modes. The more economic favourable than the conventional technology is the 2-shaft simple cycle mode for the cases of international airport (12MW total power demand) and the isolated island (120MW), while the 1-shaft simple cycle mode is the more economic favourable for the case of hotel (1MW). The main contribution of the thesis is that it provides an intergraded realistic tool, which simulates the future operation (technical and economic) of a trigeneration plant, capable of helping the potential investor decide if it is profitable to proceed with the investment.

Exploiting solar energy technology for both heating and cooling purposes has the potential of meeting an appreciable portion of the energy demand in buildings throughout the year. By developing an integrated, multi-purpose solar energy system, that can operate all twelve months of the year, a high utilisation factor can be achieved which translates to more economical systems. However, there are still some techno-economic barriers to the general commercialisation and market penetration of such technologies. These are associated with high system and installation costs, significant system complexity, and lack of knowledge of system implementation and expected performance. A sorption heat pump module that can be integrated directly into a solar thermal collector has thus been developed in order to tackle the aforementioned market barriers. This has been designed for the development of cost-effective pre-engineered solar energy system kits that can provide both heating and cooling. This thesis summarises the characterisation studies of the operation of individual sorption modules, sorption module integrated solar collectors and a full solar heating and cooling system employing sorption module integrated collectors. Key performance indicators for the individual sorption modules showed cooling delivery for 6 hours at an average power of 40 W and a temperature lift of 21°C. Upon integration of the sorption modules into a solar collector, measured solar radiation energy to cooling energy conversion efficiencies (solar cooling COP) were between 0.10 and 0.25 with average cooling powers between 90 and 200 W/m2 collector aperture area. Further investigations of the sorption module integrated collectors implementation in a full solar heating and cooling system yielded electrical cooling COP ranging from 1.7 to 12.6 with an average of 10.6 for the test period. Additionally, simulations were performed to determine system energy and cost saving potential for various system sizes over a full year of operation for a 140 m2 single-family dwelling located in Madrid, Spain. Simulations yielded an annual solar fraction of 42% and potential cost savings of €386 per annum for a solar heating and cooling installation employing 20m2 of sorption integrated collectors.

District-heating and/or cooling systems are gradually becoming popular all over the world for heating and/or cooling of large premises. Current conventional practice for the DHC underground distribution networks is to place the supply and the return pipelines side-by-side in air-filled trencRe's. However, t present investigation has shown that by optimising the location of the pipelines, the thermal insulation provided by the air around the pipes can be maximised. This is achieved by placing the hot pipeline above the cold one, the exact position depending upon the temperatures involved. For most purposes, it is recommended that the displacement ratio for the hot pipe is to be at -0.7 or -0.08 and that of the cold pipe at 0.05 or 0.67 for district heating or cooling respectively [i. e. the hot and cold pipes being placed in the upper and lower halves of the trench respectively]. Each chapter is presented in such a way that it can be read independently of the others as far as possible.

This PhD thesis is a demand led study taking into account changes in ambient conditions and power settings of a tri-generation power plant. Includes an evaluation tool for combined heat, cooling and power generation plant. The thesis is based on an overall technical-economic analysis of the tri-generation system, including: 1. Energy demand analysis and evaluation of actual tri-generation case studies. 2. Modelling of the prime mover (Gas Turbine, GT) 3. Modelling of the absorption cooling system, (LiBr/Water). 4. Economic analysis and evaluation of the entire tri-generation plant. Initially, the main effort is to carry out research concerning the energy demands of different actual cases. The research includes sourcing, collecting, classification and evaluation of the available information. The cases cover a wide range of economic life and the resulting data specifies the energy needs which the purposed tri-generation power plant needs to cover. The second part deals with the prime mover (namely the Gas Turbine, GT) modelling and simulation. The technical part of the assessment includes the Design Point (DP) and Off Design (OD) analysis of the GT. In other words, the performance analysis simulates different thermodynamic cycles (Simple, or with Heat Exchanger), and different configurations (one or two shafts). Also, the computer programming code is capable of simulating the effects of the use of different types of fuel, ambient conditions, part load conditions, degradation, or the extraction of power for district heating or for absorption cooling. The third part includes the simulation of the absorption cooling system alone and/or in co-operation with the prime mover. The simulation is based upon the premise that the original prime mover is replaceable. Finally, an evaluation methodology of tri-generation plants, is introduced taking into account, both technical facts and economic data -based on certain cases from Greek reality- helping the potential users to decide whether it is profitable to use such technology or not. The economic scene will include the basic economic facts such as initial cost, handling and operational cost (fuel prices, maintenance etc), using methodology based on Net Present Value (NPV). This thesis suggests several tri-generation technology modes. The more economic favourable than the conventional technology is the 2-shaft simple cycle mode for the cases of international airport (12MW total power demand) and the isolated island (120MW), while the 1-shaft simple cycle mode is the more economic favourable for the case of hotel (1MW). The main contribution of the thesis is that it provides an intergraded realistic tool, which simulates the future operation (technical and economic) of a trigeneration plant, capable of helping the potential investor decide if it is profitable to proceed with the investment.

Tough competition from local heating and cooling solutions fuels the pursuit of new cost efficient heat sources for district energy companies. This master thesis explores the possibilities for a district heating and cooling company to integrate data centers for recovery of residual heat. Recovery of the residual heat from data centers into the aggregated heat demand of a district energy system can lead to less primary energy input for the two operations combined. The thesis is based on a single case study on Norrenergi, a district heating and cooling company in the Stockholm region, and nine semi-structured interviews with representatives from the data center industry. An industry interview compilation, case company interviews, and literature review were applied on a framework for industrial symbiosis. Synergies, enabling factors, and obstacles to successful cross-industry collaboration was evaluated and visualized in SWOT-analyses for four different examples of configuration for integration. The analysis shows that integration of data centers into district energy systems can provide synergies on all levels of industrial symbiosis: By-product reuse; Utility/infrastructure sharing; and joint provision of services. The data center market consists of diverse actors, with a range of business models and operational conditions. Some key obstacles to instigate collaboration are related to cultural differences, reliability concerns for district cooling, uncertainty in heat delivery potential from data centers, and data center reluctance to invest in equipment for heat recovery. To mitigate the obstacles, the energy companies should tailor the service offer for each collaboration on the diversified data center market. Residual heat from data centers should be recovered in the district cooling system, where possible. When district cooling is not accessible, energy companies should explore the possibility to invest in local heat pumps for recovery into the district heating supply flow. The thesis concludes that energy companies interested in heat recovery from data centers can apply a broad range of mitigation tools to facilitate collaborations.
Hård konkurrens från lokala värme- och kyllösningar driver fjärrvärmeföretag att leta efter nya, billiga värmekällor. Det här examensarbetet har utforskat möjligheterna för ett fjärrvärme- och fjärrkylaföretag att integrera datacenter i sitt energisystem för återvinning av restvärme. Återvinning av restvärme från datacenter till det aggregerade värmebehovet hos  ett fjärrvärme-och fjärrkylasystem kan leda till minskad total primärenergianvändning för de båda verksamheterna tillsammans. Examensarbetet baseras på en fallstudie hos Norrenergi, ett fjärrvärme- och fjärrkylaföretag i Stockholmsregionen, samt nio semi-strukturerade intervjuer med representanter från datacenterindustrin. Ett ramverk för industriell symbios applicerades på en sammanställning av intervjuerna från datacenterindustrin, intervjuerna på Norrenergi samt en litteraturstudie. Synergier, möjliggörande faktorer samt hinder för framgångsrikt, inter-industriellt samarbete utvärderades och visualiserades i SWOT-analyser för fyra olika integrationsmöjligheter. Analysen visar att integrationen av datacenter in i fjärrvärme-och fjärrkylasystem kan erbjuda synergier som korresponderar till alla nivåer av industriell symbios: återvinning av restprodukter, delad infrastruktur och gemensam tillgång till tjänster. Marknaden för datacenter består av olika aktörer med flera olika affärsmodeller och förutsättningar för verksamheten. Några av de främsta hindren för samarbeten mellan energiföretag och datacenter är relaterade till kulturella skillnader, oro över hur pålitligt fjärrkyla är, osäkerhet för potentialen för värmeleverans från datacenter och datacentrens ovilja att investera i utrustning för värmeåtervinning. För att överbrygga hindren behöver energiföretagen skräddarsy tjänsteerbjudandet till varje samarbete på den diversifierade datacentermarknaden. Restvärme från datacenter bör, om möjligt, återvinnas i fjärrkylasystemet. När fjärrkyla inte är tillgängligt bör energiföretag utforska möjligheten att investera i lokala värmepumpar för värmeåtervinning till fjärrvärmenätets framledning. Sammanfattningsvis kommer studien fram till att för energiföretag intresserade av värmeåtervinning från datacenter så finns det flertal verktyg för att främja samarbeten.

Several steps are followed in order to evaluate the cycle as the title suggests. The diffusion absorption refrigerator (DAR) cycle performance is evaluated when using helium or hydrogen as auxiliary gas. A slight increase in COP is found when using helium, but it is not sufficient to justify the cost. A secondary simulation of an alternate dual-pressure cycle using a pump is done as feasibility comparison with the same parameters as the diffusion cycle. It was found that the second cycle is not acceptable due to high evaporator temperatures needed to ensure liquid enters the pump instead of partially evaporated solution. This would greatly increase the work input required for what essentially becomes a compressor. Optimisation of the DAR is evaluated by simulating the use of a rectification column and the effects of different design points on overall performance. Meteorological data for Potchefstroom, South Africa is used to perform a yearly analysis on the simulated cycle and to specify a suitable design point. The use of a radiative cooling system as heat sink for the system is then investigated and incorporated into the system model. Finally, the performance characteristics of the simulated DAR cycle are discussed, verified and compared with available data from similar research. It is shown that a 40% solution aqua-ammonia-hydrogen cycle driven by 526 kW of solar thermal energy at 130°C and a system pressure of 1.5 MPa can easily achieve a COP over 0.4 with an air-cooled absorber at 40°C and a water-cooled condenser at 35°C. A 231 kW refrigeration capacity at an average evaporator temperature of –20°C is achieved, satisfying the requirements for a domestic refrigeration system.
Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.

This work presents a model predictive control system for heating and cooling supply planning in an urban heating and cooling network. The control approach addresses the need for strategic operation of distributed production technologies and thermal energy storage in increasingly complex heating and cooling networks. Predictive optimization handles this complexity with an optimization strategy taking future demand, prices, and energy source availability into consideration. The model predictive control is integrated in a model built in a co-simulation approach. The co-simulation approach allows for models to run in their own simulation environments, preserving their levels of detail.  The model is adapted to a case study of an urban district under construction in Stockholm. Yearly simulations of the network and comparisons of the outcome when operated by the model predictive controller and by a reference rule-based controller are performed. The results show performance improvements in the form of reduced operational costs of 9.7 % and 18.8 % reduced carbon emissions, depending on how the objective function of the model predictive controller is formulated. An objective function aiming to minimize district heating imports is also formulated. While that objective function decreases the imports compared to the other objective functions, it increases the imports compared with the reference scenario, albeit from an already low share in the total energy supply of 0.2 %. A sensitivity analysis is performed to investigate the robustness of the control system. The sensitivity analysis shows that the reference controller is not robustly programmed for variations in parameters compared with the model predictive controller, which performs consistently better with both increases and decreases of the parameter sizes.  Future work could include detailed modelling in other simulation tools integrated in the co-simulation platform. Another possibility is developing a closed-loop system approach which would include, for example, feedback from the buildings’ indoor temperatures. This would allow for the utilisation of the buildings’ thermal mass as thermal energy storage. Lastly, more detailed economic and environmental calculations, such as life-cycle analysis or investment calculations, would further emphasize the real-world applicability of the findings.
Det här arbetet presenterar ett Model Predictive Control system för planering av värme- och kyltillförsel i ett urbant värme- och kylnät. Distribuerade energiresurser och termisk värmelagring leder till ökad komplexitet i planering och drift av framtidens värme- och kylnät. Prediktiv optimering hanterar komplexitet med en optimeringsstrategi som tar hänsyn till framtida efterfrågan, priser och tillgänglighet av energiresurser. Model Predictive Control systemet är integrerat i en modell uppbyggt i en Co-Simulation miljö. Co-Simulation möjliggör detaljerad modellering av olika delsystem i dess specifika simulerings miljö för att bevara dess detaljnivå.  Modellen är anpassad till en fallstudie av ett urbant distrikt under uppbyggnad i norra Stockholm. Årliga simuleringar av distriktet genomfördes. Därefter jämfördes resultat mellan simuleringar med Model Predictive Control systemet med ett konventionellt regel-baserat kontrollsystem. Tre målfunktioner var formulerade för Model Predictive Control systemet. Den första att minska driftkostnader för systemet, den andra att minska koldioxidutsläpp och det sista att minska importen från fjärrvärmenätet. Den första målfunktionen ger en minskning på 9.7 % i driftkostnader, den andra ger minskade koldioxidutsläpp på 18.8 %. Den tredje och sista däremot uppnår inte målet och ökar importen från fjärrvärmesystem jämfört med det konventionella regel-baserade kontrollsystemet. Utöver det så är en känslighetsanalys genomförd för att visa på robusthet av kontrollsystemen. Den visar att det Model Predictive Control systemet anpassar sig till förändringar i parametrar bättre än det andra kontrollsystemet.  Framtida arbeten inom området kan inkludera mer detaljerade modellering av de olika teknologierna inkluderade i studien. En annan möjlighet är utveckling av ett återkopplingssystem från byggnadernas inomhustemperatur. Det skulle möjliggöra användningen av byggnadens termiska massa som termisk energilagringssystem. Slutligen, mer detaljerad ekonomiska beräkningar och miljöberäkningar, såsom life-cycle analysis eller investeringskalkylering skulle utveckla resultaten från arbetet också.

This study is aimed to evaluate the techno-economic feasibility of implementing heat driven cooling technologies in buildings connected to Tafjord Kraftvarme’s district heating network in Aalesund, Norway. Heating and cooling demands were found by projecting two 4000 𝑚2 office buildings according to Passive House and Low Energy Building criteria, within the frame of the energy requirements in the TEK17 building regulations (Standard Norge, 2012) (Norwegian Building Authority, 2017). Suitable cooling and heating equipment, both electrical and heat driven, were dimensioned based on the peak cooling load of the projected buildings, and technical and economic information obtained from the distributors of the equipment. LCOE analysis shows that the heat driven cooling solutions could be able to compete economically, in variable extent, with the electrically driven solutions given relatively low heating demand or by applying investment subsidies or price reduction on district heat for cooling purpose. The desiccant cooling solution could even compete with the electrical driven solution even without subsidies or price reduction on DH for cooling. This is mainly because of its enhanced heat recovery reducing the heating demand. The absorption cooler on the other hand, has both a higher consumption and higher power input of district heat while running, and is therefore less competitive without subsidy or price reduction on DH for cooling. In the building cases explored, the absorption cooling solution requires either subsidy or price reduction on DH for cooling to compete with the electric chiller and district heat solution, while it require both to come close to compete economically with the heat pump solutions. With increasing heating demand the heat driven solutions, which use district heat as their heat source, become less competitive compared to the heat pump solutions. This is because, with the mild winters in Aalesund, the heat pumps can run with a COP of 2-3 while the COP of district heat it is considered to be 1. Other important factors that is not covered by the LCOE analysis is the reliability and environmental aspect. None of the heat driven cooling solutions use any environmentally unfriendly refrigerants, and the maintenance of the cooling machines are minor. The lifetimes of the machines are estimated to be 20 years for the desiccant and 40 years for the absorption cooler, compared to 15 years for the heat pumps and electric chiller. The heat driven cooling solutions can therefore be considered more reliable both in terms of regulations on refrigerants and on maintenance and lifetime. An additional important factor is that compared to the heat pump solutions, the heat driven cooling solutions with district heat to cover the heating demand can replace large quantities of electricity consumption with low-grade thermal energy. Considering both the economic, environmental and reliability factors, the heat driven cooling solutions could be a viable option and should be considered when implementing heating and cooling equipment in buildings connected to the district heating network in Aalesund or other locations with similar climate.
Studiens syfte är att utvärdera den tekno-ekonomiska genomförbarheten av att implementera värmedrivna kylelösningar i byggnader knytna till Tafjord Kraftvarme’s fjärrvärmenetvärk i Aalesund, Norge. Uppvärmnings- och nerkylningskrav hittades vid at projictera två 4000 𝑚2 kontorsbyggnader enligt “Passive House and Low Energy Building” kriterier, inom ramen av energikrav i TEK 17 byggnadsförordningar (Standard Norge, 2012) (Norwegian Building Authority, 2017). Passande nerkylnings- och uppvärmingsutrustning, både elektrisk och värmedriven, blev dimensionerande baserad på toppbelastning till de projicerade byggnader, och den tekniska och ekonomiska information tagen från utrustningsdistributörerna. LCOE-analysen visar att den värmedrivna nerkylningslösningen kan vara konkurrenskraftig ekonomisk sett, i variabel utstreckning, med de elektriska drivna lösningarna om varmebehovet är lågt eller vid at använda subventioner eller prisnedsättning på fjärrvarme som används för kylning. Nerkylningslösningen med torkmedel kan även vara konkurrenskraftig med den elektrisk drivna även utan subventioner eller prisnedsättning på fjärrvarme. Det är huvudsakligen på grund av dens förbättrade värmeåterhämtning som reducerar uppvärmningskraven. Absorptionskylaren å andra sidan, har både högre ströminmatning av fjärrvarme medan den är i gång och är därför mindre konkurrenskraftig utan subventioner eller prisnedsättning på fjärrvarme som används för kylning. I de utforskade byggnadsfallen kräver absorptionskylaren antigen subventioner eller prisnedsättning på fjärvarme för att kunna konkurrera med den elektriska kylmaren, medan det krävs både för att kunna konkurrera med värmepumpelösningen. Med ökande uppvärmingskrav blir de värmedrivna lösningarna som använder fjärrvarme som värmekälla mindre konkurrenskraftiga jämfört med värmepumpelösningarna. Detta på grund av de milda vintrar i Aalesund som leder till att värmepumparna kan köra med en COP på 2-3 medan den anses vara 1 for lösningarna som brukar fjärrvarme. Andra viktiga faktorer som inte ingår i LCOE-analysen är pålitlighet och miljöaspekten. Ingen av de värmedrivna nerkylningslösningarna andvänder något miljöovänligt köldmedium och underhållet av nerkyningsmaskiner är minimalt. Maskinernas livsläng är beräknad till 20 år för torkmedelkylaren och 40 år för absorptionskylaren, jämfört med 15 år för värmepumparna och den elektriska kylaren. De värmedrivna nerkylningslösningarna kan därför  anses vara mer pålitliga både beträffande reglering av köldmedium och underhåll samt livslängd. Ytterligare en viktig faktor är att de värmedrivna nerkylningslösningarna, jämfört med värmepumplösningarna, kan vara et livskraftig alternativ, både med hänsyn til den ekonomiska faktoren, miljöfaktoren och pålitligheten och borde därför tas hänsyn till vid implementering av uppvärmings- og nerkylningsutrustning i byggnader knytna till fjärrvärmenätet.

The supply of cooling has increased significantly in recent years, the trend shows that the increase will continue one reason is that the standard of living has increased, but EU has also set a requirement that energy consumption must be better at the same time. With “better” means more efficient and environmentally friendly. District cooling today uses either chillers or naturally available cold sources such as deep sea water, lake water or cold air. Cold air is, of course, only available when the seasons permit it and the cold air is not available when comfort cooling is needed for e.g. offices. The only alternative for areas that do not have a cold water source nearby is to use chillers. The most common chillers today are compressor chillers and absorption chillers. The most interesting chiller for the energy and environmental company HEM in Halmstad, is the absorption chiller which is driven by heat. HEM has, during the summer, surplus heat produced in Kristinehed plant which they want to use, they also have an increased inventory of waste during the summer which they get from the municipality of Halland. This heat is, of course, qualified to be used in the making of cold. Absorption chillers is today, however, not as common as compressor chillers which are capable of dealing with most cooling capacities, from small to large, and simultaneously works more or less flawlessly. Most of today’s absorption chillers are of a few hundred kW and upwards while there are no absorption chillers for the smaller effects, they are also very expensive and can have problems with crystallization of the absorbent if the operation is handled incorrectly. But it’s also expensive when it comes to piping of district cooling networks depending on where the pipes are desired, for example if it is the middle of town or over a grass field. A fictional project of the area Sannarp is used for a case study in this thesis where one investment alternative was to extend the existing district cooling pipes and another alternative was to invest in absorption chillers to meet the company's cooling demand. The results were obviously much affected by the area's layout and the distance to the first company starting from the existing pipe. The company's cooling demand also affected the results and the first alternatives investment cost could only be competitive with alternative 2 because the distance was just of the right length. If the distance to the company had been shorter, then the cooling demand for the same company has had to be less. The conclusion of the project was still in the end that and expansion of the current district cooling network to the company was the most feasible and economically advantageous.

Detta examensarbete utfördes på uppdrag av Akademiska Hus som äger och förvaltar fastigheterna på campus i Umeå. Projektet bestod av att utifrån en övergripande bild på det interna fjärrvärme- och fjärrkylanätet på campus, ta fram alternativa utformningar på systemet i syfte om att göra det mer energieffektivt. Systemets interna fjärrvärme- och fjärrkylanät VP100 och KB100 växlar över värme och kyla från Umeå Energi som sedan distribueras vidare till fjärrvärme- och fjärrkylacentraler på campus. Några av centralerna har egenproduktion där returledningen från KB100 går till en värmepump som producerar både värme och kyla. Producerad värme används till att förvärma returledningen från uppvärmningssystemen från de byggnader som hör till respektive central. När behovet av värme är tillräckligt stort är systemet, tack vare värmepumparna, självförsörjande gällande kyla. Produktion sker alltså endast under de perioder då det finns behov i uppvärmningssystemen. Det leder till att systemet tvingas köpa både värme och kyla samtidigt under sommaren då behovet av kyla i stort sett är konstant under året. Två alternativa utformningar till det befintliga systemet har undersökts. Det första fallet har som syfte att reducera värmeförlusterna i VP100. Det andra fallet byggdes vidare på det första fallet med syftet att utvidga arbetsområdet för värme- och kylproduktionen i värmepumparna. Resultatet visar att det finns potential att mer än halvera värmeförlusterna i det befintliga VP100 och att produktionen av värme och kyla skulle kunna öka med 10 % respektive 6 %. Totalt skulle systemet kunna spara drygt 1,3 miljoner kWh per år genom en kombination av de två alternativa utformningarna. För att däremot få energibalans i systemet där det aldrig behöver köpas både värme och kyla samtidigt bör andra effektiviseringsåtgärder övervägas.

[EN] For more than a decade, the urban heat networks (District Heating, DH) combined with the use of renewable energies have been consolidated as a leading tool for energy efficiency and reducing emissions of greenhouse gases. Among the various possibilities of generation in the North and Central Europe, with little or no annual demand for comfort cooling, since the 80s a large number of facilities, that use solar energy with large seasonal accumulators capable to store surplus heat captured in the period of increased solar availability and minimum demand (summer) and hold until the time of heating demand (autumn), have been built. In this type of installation, the cost of seasonal storage represents a significant percentage of investment for DH. In warmer countries of southern Europe, as in the case of Spain, where in most of the territory the energy demand for cooling is more important or the same order as the heating demand, and taking into account the high costs incurred by the seasonal deposits, a more efficient solution would be using solar energy in summer to cover a percentage of the cooling by thermal chillers (absorption / adsorption). These systems today have little implementation compared to the previous ones, and design criteria do not allow a systematic approach regarding the possible configurations and sizing of the various teams. This Is the technical solution proposed in this thesis. In the present thesis, after a timely review of the state of the Solar District Heating art, SDHC, a technical solution is proposed, intended to be easily replicable, of generation for a solar installation of hot and cold coupled to an urban network to four tubes, District Heating & Cooling, DHC. In addition, practical aspects of the business model for the operation of the network are reviewed. Two TRNSYS dynamic simulation models are developed: One for the DHC and one prior to the study of demand. A practical methodology is also provided on a first initial study to evaluate the technical and economic viability of future projects based on the same technical solution. Finally, the discussion in the previous chapters is expressed in the development of a case study. The DHC studied supplied cold and heat to 2,228 new housing in a suburb of Valencia capital. In view of energy, economic and environmental results of the case study, it is concluded that the proposal for a DHC in Valencia, as the representative city of the warm Spain, technical solution is a viable option generation and energy supply in the residential sector (and associated tertiary).
[ES] Desde hace más de una década, las redes de calor urbanas (District Heating, DH) combinadas con el uso de energías renovables se han consolidado como una herramienta de primer orden para la eficiencia energética y la reducción de emisiones de gases de efecto invernadero. Entre las distintas posibilidades de generación, en los países del Norte y Centro de Europa, con escasa o nula demanda anual de refrigeración en las viviendas, desde los años 80 se han construido un gran número de instalaciones que utilizan energía solar con grandes acumuladores estacionales capaces de almacenar el calor excedente captado en la época de mayor disponibilidad solar y mínima demanda (verano), y mantenerlo hasta la época de demanda de calefacción de otoño. En este tipo de instalaciones, el coste del acumulador estacional representa un porcentaje muy significativo dela inversión para el DH. En los países más cálidos de Sur de Europa, como el caso de España, donde en gran parte del territorio la demanda energética para refrigeración es más importante o del mismo orden que la demanda de calefacción, y teniendo en cuenta el alto coste que suponen los depósitos estacionales, una solución más eficiente podría ser la que utiliza la energía solar en época estival para cubrir un porcentaje de la demanda de frío mediante enfriadoras térmicas (absorción/adsorción). Estos sistemas tienen, a día de hoy, poca implantación en comparación con los anteriores, y no existen criterios de diseño consolidados que permitan una sistemática en cuanto a las posibles configuraciones y dimensionamiento de los distintos equipos. Esta última opción es la solución técnica que se propone en esta tesis. En la presente tesis, tras una oportuna revisión del estado del arte de los Solar District Heating, SDHC, se propone una solución técnica de generación, que se pretende fácilmente replicable, para una instalación solar de frío y calor acoplada a una red urbana a cuatro tubos, District Heating & Cooling ,DHC. Además, se revisan aspectos prácticos del modelo de negocio para la explotación de la red. Se desarrollan dos modelos de simulación dinámica TRNSYS: uno para el DHC y uno previo para el estudio de la demanda. También se proporciona una metodología práctica que permita, en un primer estudio inicial, evaluar la viabilidad técnico-económica de los futuros proyectos basados en la misma solución técnica. Por último, lo expuesto en los capítulos previos se concreta en el desarrollo de un caso práctico. El DHC estudiado suministra frío y calor a 2.228 viviendas de nueva construcción en barrio periférico de Valencia capital. A la vista de los resultados energéticos, económicos y medioambientales obtenidos en el estudio del caso, cabe concluir que la solución técnica propuesta para un DHC en Valencia, como ciudad representativa de la España cálida, constituye una opción viable de generación y suministro energético en el sector residencial (y terciario asociado).
[CAT] Des de fa més d'una dècada, les xarxes de calor urbana (District Heating, DH) combinades amb l'ús d'energies renovables s'han consolidat com una ferramenta de primer orde per a l'eficiència energètica i la reducció d'emissions de gasos d'efecte hivernacle. Entre les distintes possibilitats de generació, en els països del Nord i Centre d'Europa, amb escassa o nul.la demanda anual de refrigeració en les vivendes, des dels anys 80 s'han construït un gran nombre d'instal·lacions que utilitzen energia solar amb grans acumuladors estacionals capaços d'emmagatzemar la calor excedent captat en l'època de major disponibilitat solar i mínima demanda (estiu) i mantindre-ho fins a l'època de demanda de calefacció. En este tipus d'instal·lacions, el cost de l'acumulador estacional representa un percentatge molt significatiu de la inversió per al DH. En els països més càlids de Sud d'Europa, com el cas d'Espanya, on en gran part del territori la demanda energètica per a refrigeració és més important o del mateix orde que la demanda de calefacció, i tenint en compte l'alt cost que suposen els depòsits estacionals, una solució més eficient podria ser la que utilitza l'energia solar en època estival per a cobrir un percentatge de la demanda de fred per mitjà de refrigeradors tèrmiques (absorció/adsorció). Estos sistemes tenen a hores d'ara poca implantació en comparació amb els anteriors, i els seus criteris de disseny tampoc permeten un criteri sistemàtic quant a les posibles configuracions i dimensionament dels distints equips. És la solució tècnica que es proposa en esta tesi. En la present tesi, després d'una oportuna revisió de l'estat de l'art dels Solar District Heating, SDHC, es proposa una solución tècnica, que es pretén fàcilment replicable, de generació per a una instal·lació solar de fred i calor acoblada a una xarxa urbana a quatre tubs, District Heating & Cooling, DHC. A més, es revisen aspectes pràctics del model de negoci per a l'explotació de la xarxa. Es desenrotlla dos models de simulació dinàmica TRNSYS: un per al DHC i un previ per a l'estudi de la demanda. També es proporciona una metodología pràctica que permeta, en un primer estudi inicial, avaluar la viabilitat tècnic-econòmica dels futurs projectes basats en la mateixa solució tècnica. Finalment, allò que s'ha exposat en els capítols previs es concreta en el desenrotllament d'un cas pràctic. El DHC estudiat subministra fred i calor a 2.228 vivendes de nova construcció en barri perifèric de València capital. A la vista dels resultats energètics, econòmics i mediambientals obtinguts en l'estudi del cas, cal concloure que la solució técnica proposta per a un DHC a València, com a ciutat representativa de l'Espanya càlida, constituïx una opció viable de generació i subministrament energètic en el sector residencial (i terciari associat).
Galvany Castillo, FJ. (2016). Metodología práctica para evaluar la viabilidad de redes de frio y calor urbanas integrando energía solar y biomasa en la España cálida [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61306
TESIS

Fernkälte bietet das Potenzial, wirtschaftlich und ökologisch vorteilhaft zur Deckung des stetig zunehmenden Klimakältebedarfs beizutragen. Im Rahmen dieser Arbeit wurde ein dynamisches thermohydraulisches Netzmodell „ISENA“ entwickelt, mit dem während der Planung und des Betriebs von Fernkältesystemen auftretende Fragen, beispielsweise in Bezug auf Wirtschaftlichkeit und Energieeffizienz, beantwortet werden können. Das Netzmodell setzt sich aus einem quasistationären hydraulischen Modell und einem instationären thermischen Modell zusammen, das auf der Verfolgung von Wasserpfropfen durch das gesamte Netz basiert (Lagrange-Ansatz). Mit diesem Modellierungsansatz können numerische Fehler sowie Bilanzungenauigkeiten vermieden werden, sodass sich eine höhere Ergebnisgüte im Vergleich zu bisher bekannten Netzmodellen erreichen lässt. Ebenfalls neu entwickelt wurde das Teilmodell zur Abbildung der Wärmeströme über die Wände unterirdischer Rohrpaare (Kälteverluste und -gewinne). Dieses Modell erlaubt die Bestimmung der instationären Rohrwand-Wärmeströme für wärmegedämmte unterirdische Rohrpaare, Rohrpaare mit gedämmtem Vor- und ungedämmtem Rücklauf sowie ungedämmte Rohrpaare. Anhand von Validierungs- und Verifikationsrechnungen wird gezeigt, dass ISENA verlässliche Ergebnisse liefert und für die praktische Anwendung geeignet ist. Abschließende Beispielrechnungen geben einen Einblick in die Untersuchungsmöglichkeiten, die das neue Modell bietet – unter anderem im Hinblick auf den Vergleich von Pumpenregelungsvarianten, den Einfluss von Rohrdämmung und Erdreicheigenschaften auf Kälteverluste und -gewinne sowie die Einbindung von Hochtemperatur-Kälteverbrauchern in den Netzrücklauf
District cooling can provide economic and ecological benefits while supplying the increasing cooling demand for air conditioning. In the present thesis, a dynamic thermo-hydraulic model “ISENA” is presented which may be used in order to answer questions arising during design and operation of district cooling networks—e. g., that are related to economic and energy efficiency. The network model consists of a quasi-static hydraulic module and a transient thermal module being based on the tracking of water segments through the entire network (Lagrangian method). With this approach, numerical errors and inaccuracies in the balance of conserved quantities could be avoided, which eventually leads to a better reliability of the results as compared to that obtained from other network models. Additionally, a new sub-model has been developed for predicting the transient heat flux through the walls of buried pipes in order to model thermal gains and losses. This model covers un-insulated, insulated and combinations of insulated as well as un-insulated pipes. Calculations performed for the purpose of validation and verification are presented in order to demonstrate that ISENA provides reliable results and hence is suitable for practical applications. Finally, example simulations show the various possibilities provided by the new model—for example, concerning the comparison of different strategies for pump control, the influence of pipe insulation and soil properties on thermal gains and losses as well as the connection of buildings equipped with high temperature cooling systems to the return line of the network

Satellite District Heating and Cooling (DHC) systems offer an alternative structure to conventional, centralized DHC networks. Both use a piping network carrying steam or water to connect disparate building heating and cooling loads together, providing a platform for improving energy efficiency, reducing emissions, and incorporating alternative means of energy generation. However, satellite DHC networks incorporate thermal production units that are distributed amongst the buildings nodes, which offers greater operational flexibility and reduced capital cost savings for applications using existing building stock. This study was focused on the development of the methodology behind a comprehensive energy model that can assess the practical and financial viability of satellite DHC network scenarios. A detailed scenario application of the model demonstrated significant energy savings and investment potential. Additionally, environmental assessment methods and alternative generation technology were explored in supplementary studies of Deep Lake Water Cooling (DLWC) and building-scale Combined Heat and Power (CHP).

博士
國立臺灣大學
機械工程學研究所
103
This dissertation numerically investigates the optimization design of a district heating and cooling system using waste heat recovery from the diesel generators of power plants on an isolated island and the feasibility assessment of energy savings performance contracts (ESPC) with energy-savings project. Firstly, the mathematical models of the hourly available waste heat for systems and the power consumption of systems are developed. In consideration of both parties, the power company and the energy service company (ESCO), the ESPC of energy-savings project is planned. This study then compares the performances of four updating rules of the particle swarm optimization (PSO) through applying four mathematical problems. The linear-decayed inertia weight method is favorable for this study because stability is the target solution. The objective function of the optimization design includes the initial cost and the running cost during the life-cycle period. In this study, the PSO method is adopted to acquire the minimum value of the objective function, where the constraints include the conservation of energy between absorption chiller and chilled water storage tank of district cooling system (DCS). The optimization result of the DCS is achieved with a 380 kW absorption chiller and a storage tank with a capacity of 1,500 kW-hr. Furthermore, the study compares energy-saving efficiency with and without the district heating and cooling system. In district heating system (DHS), it has been proved that the yearly average energy conservation rate, electricity consumption, diesel consumption, and CO2 emissions can be reduced by 95.1%, 9,237.6 MWh, 23,220 L, and 168 ton respectively. In district cooling system, it has been shown that the yearly average energy conservation rate is approximately 75.7%, whereas the yearly electricity consumption, diesel consumption and CO2 emissions can be reduced by 955.8 MWh, 32,566 L and 228 ton respectively. Setting the project period of 10 years, and the project lending rates of 2.25%, the results show that the energy-savings project combining DHS and DCS yield maximum income. For the power company, operation without ESPC results in the most income. The payback period and the income with ten-years of timespan are six years and 21,758,719 TWD respectively. Moreover, the return on investment is 54.9%. For ESCO, the contract type of shared savings has maximum income. The payback period and the receipts of ten-years are six years and 19,912,488 TWD respectively. Additionally, the return on investment is 48.3%. According to the current interest rate of this energy-saving project, the discounted interest rate for isolated islands’ constructions lower than 2.25 % would provide incentive for the execution of this project. Otherwise, the execution of this project would be hindered due to higher costs and longer payback periods.

Thermal energy storage (TES), the storage of heat or cooling, is a cost-effective energy storage technology that can greatly enhance the performance of the energy systems with which it interacts. TES acts as a buffer between transient supply and demand of energy. In solar thermal systems, TES enables the power output of the plant to be effectively regulated, despite fluctuating solar irradiance. In district energy systems, TES can be used to shift loads, allowing the system to avoid or take advantage of peak energy prices. The benefit of TES, however, can be significantly enhanced by dynamically optimizing the complete energy system. The ability of TES to shift loads gives the system newfound degrees of freedom which can be exploited to yield optimal performance. In the hybrid solar thermal/fossil fuel system explored in this work, the use of TES enables the system to extract nearly 50% more solar energy when the system is optimized. This requires relaxing some constraints, such as fixed temperature and power control, and dynamically optimizing the over a one-day time horizon. In a district cooling system, TES can help equipment to run more efficiently, by shifting cooling loads, not only between chillers, but temporally, allowing the system to take advantage of the most efficient times for running this equipment. This work also highlights the use of TES in a district energy system, where heat, cooling and electrical power are generated from central locations. Shifting the cooling load frees up electrical generation capacity, which is used to sell power to the grid at peak prices. The combination of optimization, TES, and participation in the electricity market yields a 16% cost savings. The problems encountered in this work require modeling a diverse range of systems including the TES, the solar power plant, boilers, gas and steam turbines, heat recovery equipment, chillers, and pumps. These problems also require novel solution methods that are efficient and effective at obtaining workable solutions. A simultaneous solution method is used for optimizing the solar power plant, while a static/dynamic decoupling method is used for the district energy system.
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