Techno-Economic and Environmental Performance of Two Distinct State-of-the-Art Solar-Assisted District Energy System Topologies
Notice bibliographique
Résumé
This study introduces a novel, ambient-temperature district energy system topology that enables bi-directional mass flow to booster heat pumps and includes distributed solarthermal generation.The ambient system topology is described, and a corresponding detailed model is developed in the MATLAB-Simulink® environment.An equivalent model is developed for a conventional, supply-return district system utilizing hot water (at 75°C) and chilled water (at 15°C), allowing for the direct comparison with the proposed topology-both with and without solar-thermal integration-in technical, environmental, and economic analyses.Technical performance is assessed using a system coefficient of performance and solar fraction, environmental performance is estimated using carbondioxide equivalent emissions, and economic performance is characterized using a levelized cost of energy approach.Annual simulations are conducted for the case study of an urban district energy system in Ottawa, Canada, connected to 12 commercial building clusters.The ambient-temperature system achieves an annual system coefficient of performance of 1.40 without solar assistance and 1.43 with solar assistance.The conventional system achieves annual coefficients of performance of 1.26 and 1.28, respectively.The solar fractions of the ambient and conventional systems are 5.5 and 4.0% for heating and 9.3 and 10.0% for cooling, respectively.Despite these noted improvements in performance with solar-thermal, the technical findings indicate that the rooftop solar collection fields are undersized relative to system loads due to rigid rooftop space constraints.Nonetheless, the ambient system (without solar) decreases annual carbon emissions by 32.16% relative to the conventional system, a significant improvement.Furthermore, while the ambient system's levelized cost of energy is higher than the conventional both without solar (8.1 iii vs. 6.0¢/kWh) and with solar (11.0 vs. 9.2¢/kWh), the ambient system becomes the most economically attractive option if the social cost of carbon is considered at any price above $16/tCO2-e-a rate far below the existing Canadian price of $50/tCO2-e.v Nomenclature 𝐴 Area (m 2 ) 𝐴𝐸𝑂 Annual energy output (kWh) 𝑏 𝑖 Incidence angle modifier coefficient 𝑖 (-) 𝑐 𝑖 Heat loss coefficient 𝑖 (-) 𝑐𝐿𝐶𝑂𝐸 Composite levelized cost of energy ($/kWh) 𝐶𝑂𝑃 Coefficient of performance (-) 𝐶 𝑝 Specific heat of water at constant pressure (J/kg-K) 𝐶𝑅𝐹 Capital recovery factor (-) 𝑐𝑇𝑎𝑥 Carbon tax rate ($/tCO2-e) 𝑑 Pipe depth 𝐷 𝑖 Pipe inner diameter (m) 𝐷 𝑜 Pipe outer diameter (m) 𝐸 𝐶𝑂2𝑒 Carbon-dioxide equivalent emissions (t) 𝐸𝐹 Emissions factor (tCO2-e/GWh) 𝑓 𝐷 Darcy friction factor (-) 𝐹 𝑡 Natural gas costs in year 𝑡 ($) 𝐼 𝑇 Incident solar radiation (W/m 2 ) 𝐼 𝑡 Capital costs in year 𝑡 ($) 𝑘 Thermal conductivity (W/m•K) 𝐾 𝜏𝛼 Incidence angle modifier (-) 𝐿 Pipe length (m) 𝑙 Solar collector length (m) 𝐿𝐶𝑂𝐶 Levelized cost of carbon ($/kWh) 𝐿𝐶𝑂𝐸 Levelized cost of energy ($/kWh) 𝐿 𝑑𝑒𝑠𝑖𝑔𝑛 Design load (W) 𝑚̇ Mass flow rate (kg/s) 𝑀 𝑡 Operations and maintenance costs in year 𝑡 ($) 𝑁 Number of computational nodes in tank model (-) 𝑛 Project lifetime (years) 𝑃 𝑡 Electricity costs in year 𝑡 ($) 𝑄 ̇ Rate of heat transfer (W) 𝑟 Discount rate (%, annualized) 𝑅𝑒 Reynolds number (-) 𝑆𝐹 Solar fraction (%) 𝑇 Temperature (K or °C) 𝑡 Thickness (m) 𝑡 𝑑𝑒𝑙𝑎𝑦 Build time (years) 𝑣 Velocity (m/s) 𝑉 𝑆𝑇𝑆 Tank volume (m 3 ) 𝑊 ̇ Rate of electrical power consumption (W) 𝑤 Solar collector width (m) Greek Letters 𝛽 Solar collector tilt (°) 𝛾 Solar collector azimuth angle (°) 𝛥𝑃 Design pressure differential (kPa) 𝛥𝑇 Design temperature difference (K or °C) 𝛥𝑡 Simulation time step (s) vi 𝜖 𝐻𝐸𝑋 Heat exchanger effectiveness (-) 𝜂 Efficiency (-) 𝜂 𝐻𝑃,𝐶𝑎𝑟𝑛𝑜𝑡 Heat pump Carnot effectiveness (-) 𝜃 Angle of incident solar radiation (°) 𝜌 Density (kg/m 3 ) (𝜏𝛼) 𝑛 Transmittance-absorptance product (-) Abbreviations and Subscripts AC Absorption chiller air Air amb Ambient topology AMY Actual meteorological year c Cooling CAD Canadian dollars casing Pipe casing CEEDC Canadian Energy & Emissions Data Centre CHP Combined heat and power chw Chilled water stream (in variable-compression and absorption chillers) cond Condenser (of heat pumps or chillers) conv Conventional topology COP Coefficient of performance CT Cooling tower CV Control valve cw Cooling water stream (in variable-compression and absorption chillers) DC District cooling DE/DES District energy/District energy system DH District heating DLSC Drake Landing Solar Community DN Diametre Nominal (metric standard pipe sizes) EIA United States Energy Information Administration eva Evaporator (of heat pumps or chillers) h Heating HEX Heat exchanger HP Heat pump hw Hot water stream (in absorption chiller) in Inlet ins Pipe insulation IPCC Intergovernmental Panel on Climate Change ISO International Organization for Standardization load Load side of plant solar dispatch loop LT Long-term (thermal storage) max Maximum (i.e., rated capacity) min Minimum NCR National Capital Region NG Natural gas NPV Net present value out Outlet PE Polyethylene return Return-side property, entering plant
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».