Domestic solar hot water is becoming a more common technology used specifically with the residential market of New Zealand. Recently domestic solar hot water systems have been economically identified as an option in commercial applications. Commercial building owners in the corporate world generally base decisions on economic reasons, therefore this research investigates the need to economically optimise the size of domestic solar hot water systems for eight separate commercial applications within Christchurch. All modelling has been completed using Consol’s heat pipe evacuator tube panels orientated North at an angle of 45 degrees. The TRNSYS simulation program is utilised to model the domestic solar hot water system in the eight commercial applications. Each commercial application has a unique domestic hot water load profile. The heat pipe evacuated tube is locally available from Consol New Zealand Limited. A common proportional relationship was utilised to define the relationship between the size of the storage tank and area of solar panels, which enables a range of domestic solar hot water system sizes to be used in the simulations. A proportional relationship is identified to economically optimise the size of commercial domestic solar hot water systems in Christchurch. This proportional relationship enables engineers and designers of commercial domestic hot water systems to confidently implement domestic solar hot water system designs. This provides an economically optimal solution in regards to the size of the solar component that should be installed during the rebuild of Christchurch.

The beachfront hotel with hybrid geothermal heat pump system (HyGSHP), located in the hot-humid climate, is simulated by TRNSYS in the thesis, and the simulation results are validated by the measured data. The simulation of alternative HVAC systems, complete ground source heat pump and conventional air source heat pump, are included to conduct the comparative study with HyGSHP based on the energy consumption and life cycle analysis. The advantages and disadvantages of HyGSHP are discussed in the thesis. Two ground source heat exchanger parameters, U-tube size and grout materials, are investigated in order to study the effects on the ground heat exchanger thermal performance. The preliminary work and results are shown in the thesis.

This thesis is a study of an indirect heat pump assisted solar domestic hot water (I-HPASDHW) system, where the investigated configuration is called the Dual Side I-HPASDHW system. The study outlines the development of an Experimental Test Unit (ETU), and focuses on the experimental validation of TRNSYS models. Shortcomings of the system design realized throughout the validation process, as well as weaknesses in the control schemes used to operate the system are also provided. A description of the Dual Side I-HPASDHW system is provided along with the design intent of the system. The corresponding ETU is presented in detail to provide a comprehensive understanding of the ETU’s simulation capabilities. Components of the ETU, such as the heat pump, heat exchanger, and domestic hot water (DHW) tank are characterized in order to provide input data for built-in TRNSYS models, and to develop custom TRNSYS models for the heat pump and heat exchanger. Heat exchanger performance is modelled with a linear correlation, while the heat pump performance is mapped by applying experimental data to three-dimensional surface fitting software. For the purpose of validation, the ETU is used to simulate the performance of the Dual Side I-HPASDHW system under a realistic control scheme. Four full day tests are conducted using data from a fall, winter, and summer day. The full day summer test is repeated with and without electrical backup heating. The TRNSYS model of the Dual Side system is tuned in order to provide the closest match possible between the computer simulation and the measured performance of the ETU. Experimental tests were compared with TRNSYS simulations to reveal some disparity in the results. The majority of simulation error was attributed to inaccuracy in modeling DHW tank temperatures and water circulation patterns. The disparity created by the DHW tank model only resulted in substantial performance deviation when inaccurate DHW temperatures were used directly for vital control decisions. Conclusions were drawn suggesting that the TRNSYS model of the ETU was valid for a majority of operating conditions, often matching experimental tests well within experimental uncertainty. Caution was recommended towards the use of the developed TRNSYS model, where techniques were recommended for tracking and minimizing substantial simulation errors. Several key performance issues affecting the Dual Side I-HPASDHW system were targeted with recommendations for design and control alterations, along with future improvement and optimization studies.

This thesis is a study of an indirect heat pump assisted solar domestic hot water (I-HPASDHW) system, where the investigated configuration is called the Dual Side I-HPASDHW system. The study outlines the development of an Experimental Test Unit (ETU), and focuses on the experimental validation of TRNSYS models. Shortcomings of the system design realized throughout the validation process, as well as weaknesses in the control schemes used to operate the system are also provided. A description of the Dual Side I-HPASDHW system is provided along with the design intent of the system. The corresponding ETU is presented in detail to provide a comprehensive understanding of the ETU’s simulation capabilities. Components of the ETU, such as the heat pump, heat exchanger, and domestic hot water (DHW) tank are characterized in order to provide input data for built-in TRNSYS models, and to develop custom TRNSYS models for the heat pump and heat exchanger. Heat exchanger performance is modelled with a linear correlation, while the heat pump performance is mapped by applying experimental data to three-dimensional surface fitting software. For the purpose of validation, the ETU is used to simulate the performance of the Dual Side I-HPASDHW system under a realistic control scheme. Four full day tests are conducted using data from a fall, winter, and summer day. The full day summer test is repeated with and without electrical backup heating. The TRNSYS model of the Dual Side system is tuned in order to provide the closest match possible between the computer simulation and the measured performance of the ETU. Experimental tests were compared with TRNSYS simulations to reveal some disparity in the results. The majority of simulation error was attributed to inaccuracy in modeling DHW tank temperatures and water circulation patterns. The disparity created by the DHW tank model only resulted in substantial performance deviation when inaccurate DHW temperatures were used directly for vital control decisions. Conclusions were drawn suggesting that the TRNSYS model of the ETU was valid for a majority of operating conditions, often matching experimental tests well within experimental uncertainty. Caution was recommended towards the use of the developed TRNSYS model, where techniques were recommended for tracking and minimizing substantial simulation errors. Several key performance issues affecting the Dual Side I-HPASDHW system were targeted with recommendations for design and control alterations, along with future improvement and optimization studies.

This study is an attempt at achieving Net Zero Energy Building (NZEB) using a solar Organic Rankine Cycle (ORC) based on exergetic and economic measures. The working fluid, working conditions of the cycle, cycle configuration, and solar collector type are considered the optimization parameters for the solar ORC system. In the first section, a procedure is developed to compare ORC working fluids based on their molecular components, temperature-entropy diagram and fluid effects on the thermal efficiency, net power generated, vapor expansion ratio, and exergy efficiency of the Rankine cycle. Fluids with the best cycle performance are recognized in two different temperature levels within two different categories of fluids: refrigerants and non-refrigerants. Important factors that could lead to irreversibility reduction of the solar ORC are also investigated in this study. In the next section, the system requirements needed to maintain the electricity demand of a geothermal air-conditioned commercial building located in Pensacola of Florida is considered as the criteria to select the optimal components and optimal working condition of the system. The solar collector loop, building, and geothermal air conditioning system are modeled using TRNSYS. Available electricity bills of the building and the 3-week monitoring data on the performance of the geothermal system are employed to calibrate the simulation. The simulation is repeated for Miami and Houston in order to evaluate the effect of the different solar radiations on the system requirements. The final section discusses the exergoeconomic analysis of the ORC system with the optimum performance. Exergoeconomics rests on the philosophy that exergy is the only rational basis for assigning monetary costs to a system’s interactions with its surroundings and to the sources of thermodynamic inefficiencies within it. Exergoeconomic analysis of the optimal ORC system shows that the ratio Rex of the annual exergy loss to the capital cost can be considered a key parameter in optimizing a solar ORC system from the thermodynamic and economic point of view. It also shows that there is a systematic correlation between the exergy loss and capital cost for the investigated solar ORC system.

The influence of control strategies and storage tank sizes on the system performance of a solar thermal assisted ground source heat pump(SAGSHP) installation has been investigated. The system investigated is in the design stage and will be implemented in the project Slottsholmen in Västervik, Sweden during 2015. Using the simulation software TRNSYS the suggested system has been modelled in its entirety and the response of the system for different control strategies and storage tank size configurations have been investigated.The system is designed with a dual tank configuration where solar heat can either be used for direct domestic hot water(DHW) production(in a high grade tank) or utilized as additional source for the heat pumps(in a low grade tank) with the purpose of increasing evaporation temperatures of the heat pumps. Four different control strategies have been investigated. Two strategies where either tank is prioritized, one where the two tanks are run in series and heat can be delivered at two temperature levels simultaneously and one strategy where the low grade storage tank is by-passed and heat is only utilized directly for DHW production. For each control strategy a series of different tank size configurations have been tested. Results show that the influence of control strategies dominate the effect of different storage tank size configurations. Solar fraction for the system varies between 0.10 and 0.13 between control strategies while variations between storage tank sizes are close to negligible. The electricity use of the SAGHSP system has been compared to a reference system where the solar collectors are switched off. The results show that fractional energy savings of the SAGSHP system ranges from 0.066 to 0.099 between control strategies. Interestingly the fractional energy savings increases for cases with lower solar fraction. For control strategies which prioritize DHW production the temperature level in the solar collector loop increased thus leading to lower solar collector efficiency and less collected heat. However, solar heat used directly for DHW production leads to a higher electricity savings than using the heat as source for the heat pumps which explains the decoupling of fractional energy savings from solar fraction. An attempt to quantify the value of the harvested solar collected heat is done by introducing a performance figure named ''Solar Savings Efficiency'' which is the ratio of the electricity savings compared to the reference system to the collected solar heat. The Solar Savings Efficiency ranges from 0.23 to 0.46 with the higher value registered for strategies which prioritize DHW production. / Inverkan av strategier för styrning och ackumuleringsvolymer på systemprestandan hos en solkollektorassisterad bergvärmeinstallation har undersökts. Det undersökta systemet är i projekteringsstadiet och kommer att byggas i projektet Slottsholmen i Västervik under 2015. Genom att använda simuleringsmjukvaran TRNSYS har systemet modellerats i sin helhet och systemets respons på olika styrstrategier och konfiguration av ackumulatortankar har undersökts. Systemet är designat med två ackumuleringstankar för solkollektorkretsen där solvärme antingen kan användas för direkt beredning av varmvatten(en varm tank) eller som värmekälla för systemets värmepumpar(en kall tank) med syftet att då höja värmepumparnas förångningstemperatur. Fyra olika styrstrategier har undersökts. Två strategier där antingen den varma eller den kalla tanken är prioriterad, en strategi där båda tankarna är i serie och värme kan lämnas vid båda temperaturnivåer samtidigt samt en fjärde strategi där den kalla tanken alltid förbigås och solvärmen endast används för direkt beredning av varmvatten. För varje styrstrategi har en rad olika konfigurationer på ackumuleringstankarna testats. Resultatet visar att inverkan av styrstrategier dominerar över den effekt som olika ackumuleringsvolymer har. Andelen av systemets värmelast som betjänas av solvärme varierar mellan 0.10 och 0.13 mellan olika styrstrategier medan variation mellan olika ackumuleringsvolymer är nära försumbar. Elanvändningen i systemet har jämförts mot ett referenssystem där solkollektorerna är avstängda. Resultaten visar att besparingen i elektricitet relativt referenssystemet varierar mellan 6.6 % och 9.9 % mellan olika styrstrategier. Intressant är att elbesparingen är högre för fall med lägre andel solvärme. För styrstrategier som prioriterar varmvattenberedning ökar temperaturnivån i solkollektorkretsen vilket leder till lägre verkningsgrad för solkollektorerna och därmed lägre andel solvärme som förs in i systemet. Dock visas att solvärme som används direkt för varmvattenberedning leder till högre elbesparing än solvärme som används som källa för värmepumparna vilket förklarar den lägre elanvändningen vid lägre andel solvärme. Ett försök att kvantifiera värdet av den skördade solvärmen har utförts genom att introducera ett nyckeltal kallat ''Solbesparingsverkningsgrad (Solar Savings Efficiency)''. Nyckeltalet är definierat som kvoten av elbesparingen för en viss strategi/konfiguration jämfört med referenssystemet och total mängd solenergi som skördats. Solbesparingsverkningsgraden varierar mellan 0.23 och 0.46 med det högre värdet för strategier som prioriterar direkt varmvattenberedning.

To assess the long-term performance of a solar thermal system, mathematical models that accurately capture the effects of heat transfer within and interactions between individual components are required. For solar domestic hot water systems, the components can include the solar collectors, storage tanks, heat exchangers, pumps, and associated piping. In addition, weather data and demand profiles are also required. Simplified models for each component are needed to reduce the computational time required to run long-term simulations. The simplified models, however, must also be sufficiently accurate in order to provide meaningful system-level results. Accurate prediction of the temperature profiles in the storage tanks of these systems is important since the temperature within the tank has a large impact on the efficiency of the entire system. TRNSYS, which is a commercial code commonly used for such simulations, contains a variety of different one-dimensional storage tank models. Previous research has indicated that these models have deficiencies in predicting experimental data. Therefore, this thesis is focussed on the analysis of the tank modelling used in TRNSYS. Results of this thesis show that the poor predictions are a result of numerical diffusion due to insufficient grid resolution. The correct theoretical profiles could be obtained by using a large number of nodes. However, this would lead to a significant increase in computational time. Alternative modelling strategies were also developed using analytical techniques to more accurately predict the temperature profiles within a storage tank while keeping a relatively low computational cost. Different models were created which considered the different mixing mechanisms present in a storage tank, such as increasing inlet temperatures with time, heat losses to the surroundings, tank wall heat conduction, and inlet jet mixing. / Thesis / Master of Applied Science (MASc)

Baigiamajame magistro darbe nagrinėjamas mažaenergis administracinis pastatas ir AEI panaudojimo jame galimybės Lietuvos meteorologinėmis sąlygomis. Naudojant modeliavimo priemonę TRNSYS sukuriami mažaenerginio administracinio pastato bei AEI sistemų skaičiavimo – valdymo modeliai: saulės kolektoriai, foto elementai, vėjo jėgainės, šilumos siurbliai, imantys šilumą iš grunto bei oro. Atlikus modeliavimą gauti pastato energijos suvartojimai šildymui (54 kWh/m2), vėsinimui (20 kWh/m2) bei elektros (48 kWh/m2). Metiniame pastato energijos balanse, energija pagaminta iš AEI gali padengti 56,6% reikalingos šiluminės energijos, 102,9 % energijos reikalingos vėsinimui ir 4,5 % reikalingo elektros kiekio. Pastato energijos poreikių jautrumo analizė atliekiama 3 pastato variantams. Pastebėta, kad esant didesniam stiklinių atitvarų plotui pietinėje pastato pusėje pagamintas šilumos kiekis iš AEI gali padengti net 85 % pastatui reikalingo šilumos kiekio. Tačiau beveik du kartus išaugo energijos poreikis pastato vėsinimui. Mažiausias vėsinimo kiekis reikalingas stačiakampio ploto pastatui. Apibendrinus rezultatus, pateiktos išvados ir rekomendacijos. Darbą sudaro 5 dalys: įvadas, 5 skyriai, išvados ir rekomendacijos, literatūros sąrašas. Darbo apimtis – 63 p. teksto be priedų, 31 iliustr., 16 lent., 27 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai. / Thesis examined low energy office building and possibilities of renewable energy use in it by Lithuanian meteorology conditions. Using TRNSYS simulation tool the computing-control models for low energy office building and renewable energy systems (RES) (solar collectors, photovoltaic, wind turbines and heat pumps taking the heat from the soil and air) are created. After the simulation buildings’ energy consumption for heating (54kWh/m2), cooling (20 kWh/m2) and electricity (48 kWh/m2) were obtained. The annual building energy balance: an energy produced from RES can cover 56.6 % of the necessary thermal energy, 102.9 % of the energy required for cooling and 4.5 % required for electricity generation. The buildings’ energy demand sensitivity analysis is performed for three buildings’ variants. It is observed that of a larger area of the glass envelope of the building in southern direction the amount of heat produced from RES can cover up to 85% of the building required heat. However, almost twice rises electricity demand in cooling of the building. The minimum amount of cooling is required for a rectangular area building. Summarizing the results, conclusions and recommendations are presented. The work consists of 5 parts: introduction, 5 chapters, conclusions and recommendations, references. Work size – 63 pages without appendices, 31 figures, 16 tables, 27 references. Appendices.

The Swedish government has set a target of a 100% renewable electricity system by 2040. To reach this goal, many actions have to be undertaken. Electrification of buildings is one action to be undertaken as the residential sector accounts for a large share of greenhouse gas emissions, where the most energy efficient method is to use heat pumps. Ground Source Heat Pumps typically have the highest efficiency out of the different heat pumps. These types of heat pumps are most commonly used in single family houses, as multi-family houses often are located in highly densely areas. However, when adding hybrid PV/thermal collectors to ground source heat pump systems, studies have shown that the borehole drilling area can be reduced, which increases the potential for combined PV/thermal collectors and ground source heat pump systems in multi-family areas.  In this project, a time-efficient, flexible and user- friendly model was developed to increase the potential for designing combined PV/thermal collectors and ground source heat pump systems. The model is based on the research model by Sommerfeldt and Madani (2019), where the flexibility and time step of the model was investigated and adjusted. The finished model was verified to the model by Sommerfelt and Madani (2019). Overall, the results show that the new model gives similar results to the original model, despite all adjustments. The heaviest adjustments were made in the heat pump where the quantitative results show a mean bias error of -0.51 kWh and a total yearly difference of -5.18% for the compressor power. The corresponding values for the condenser heating rate are -1.05 kWh and -2.86%. The user is able to change boundary conditions such as location, PVT array, building size, and borehole field size. The model takes approximately 2 minutes to run for a 20 years simulation on a business grade desktop computer, which is a five-hour twenty minute reduction from the original research model and assumed to be an acceptable time range for a commercial applications. / Regeringen har satt ett mål om att nå ett 100% förnybart energisystem till 2040. För att nå målet måste många insatser göras. Bostadssektorn står för höga halter av växthusgasutsläpp och elektrifiering av sektorn är en lovande väg att gå. Värmepumpar tillhör de mer energieffektiva tillvägagångssätten, av vilka bergvärmepumpar oftast erhåller den högsta effektiviteten. Bergvärmepumpar är idag mestadels installerat i enfamiljshus där det finns utrymme för att borra borrhål. Flerfamiljshus finns ofta i tätbebyggda områden där ytan tillgänglig för borrhål är begränsad. Emellertid har studier har visat att kombinerade PVT och bergvärmesystem kan minska borrhålsytorna, vilket ökar möjligheten för dessa typ av system även till flerfamiljshus.  Detta projekt syftar till att utveckla en kommersiell modell för design av PVT och bergvärmesystem för att underlätta design av dessa system. Att modellen är kommersiell antyder på att den är användarvänlig, flexibel och tidseffektiv. Modellen är baserad på en forskningsmodell av Sommerfeldt och Madani (2019) men justerades för att möta kraven för en kommersiell modell. Den färdiga modellen jämfördes och verifierades med modellen av Sommerfeldt och Madani (2019). Övergripande visades resultat som är jämförbara med forskningsmodellen, trots alla justeringar. De största justeringarna gjordes i värmepumpen där de kvantitativa resultaten visar ett mean bias error på -0.51 kWh och en årlig skillnad på -5.18% för elbehovet i kompressorn. Motsvarande värden för värmeutbytet i kondensorn är -1.05 kWh och -2.86%. Användaren har möjlighet att ändra gränsvillkor så som geografisk plats, PVT system, byggnadsstorlek och storleken på borrhålsfältet. Den färdiga modellen tar cirka två minuter att köra för en 20-års simulering på en typisk arbetsdator, vilket motsvarar en minskning på 5 timmar och 20 minuter jämfört med originalmodellen. Detta kan anses vara inom tidsramen för kommersiella appliceringar.

Im Rahmen der vorliegenden Arbeit wird gezeigt, wie ein Gebäude- und Anlagensimulationsprogramm mit bekannten Optimierungsalgorithmen gekoppelt und zur theoretischen Lösung optimaler Steuer- und Regelprobleme in der Gebäudetechnik eingesetzt werden kann. Theoretische Optimallösungen erlauben im Sinne eines optimalen Vergleichsprozesses die Bewertung praktisch anderweitig umsetzbarer Steuerungs- und Regelungsmechanismen. Die im Hinblick auf ein gewähltes Gütekriterium erforderliche Notwendigkeit zur Verbesserung von vorhandenen Steuerungs- und Regelungsszenarien sowie die theoretisch maximal erreichbaren Extremwerte lassen sich leicht abschätzen.