1,720,998 research outputs found
Payoff for geothermal heat pumps using shallow ground heat exchangers
No full textA discounted cash flow analysis (DCFA) and a cost benefit analysis (CBA) have been implemented in order to nvestigate the economic aspects of ground coupled heat pump (GCHP) for space heating and cooling, in comparison to traditional condensing boiler (CB). The DCFA allows the analysis of investment costs, operating costs and savings of the two different systems in order to understand if the GCHP’s pay back periods (PBPs) period is more interesting than CB in coming years. The first financial model (DCFA) takes account for economic factors as prices, costs and growth, while the economic approach (CBA) include the carbon price into the calculation, considering the social costs of carbon dioxide emissions. The whole analysis is implemented adopting a parametric approach, in which all the economic terms are linked to energy labels, degree-days and energy mix ratios (EMRs), the latter obtained as ratio between the cost of electricity and natural gas paid by the householder. Relating to different EMRs, the PBPs are presented in matrixes in which energy labels and degree-days are the row/column variables, to confront the benefits of choosing between GSHP versus CB. The PBPs are also calculated with the introduction of the carbon price, so that some considerations about the environmental aspects are presented. The results show that all higher energy labels have a good profitability ratio between costs and payback periods and demonstrate that GCHP system does pay off
Performance analysis of a multi-source renewable energy system for temperature control in buildings of varied thermal transmittance and climate zone
Full text linkEconomic performance of ground source heat pump: does it pay off?
No full textA DCF model (discounted cash flow model) is implemented in order to investigate the economic aspects of GSHP (ground source heat pump) for heating and cooling, in comparison to traditional CB (condensing boiler). The DCF model allows the analysis of investment costs, operating costs and revenues of the two different systems in order to understand if the GSHP outperform its conventional counterpart in coming years, explicitly taking account for factors as price/cost growth. The whole analysis is performed adopting a parametric approach, in which all the previous terms are linked to energy labels, degree-days and EMRs (Energy Mix Ratios), the latter obtained as ratio between the full unit cost of electricity and natural gas paid by the householder. Relating to different EMRs, the DPBPs (Discounted Pay Back Periods) are presented in decision support matrixes in which energy labels and degree-days are the row/column variables, to confront the benefits of choosing between GSHP versus CB. Some considerations are also presented in order to express the environmental aspects. The results show that all higher energy labels have a good profitability ratio between costs and payback periods and demonstrate that GSHP system does pay off. Lower labels become interesting when the EMR drops to 0,25 and the gas price goes up 0,70 €/Nm3
Valorizzazione di adduttori acquedottistici a fini termici: un caso studio
No full textLa possibilità tecnologica di avvalersi di grandi adduttori acquedottistici a supporto della climatizzazione civile rappresenta una soluzione ancora solo parzialmente esplorata, sebbene esistano già esperienze equivalenti che valorizzano i reflui fognari come sorgente termica per grandi gruppi a pompa di calore accoppiati a reti di teleriscaldamento. In analogia, la rete acquedottistica costituisce una infrastruttura diffusa nel tessuto urbano e può rappresentare un potenziale vettore termico, in relazione all’elevato calore specifico dell’acqua ed alla temperatura in condotta, tendenzialmente meno antagonista di quella dell’aria. La disposizione in ipogeo determina, inoltre, la possibilità di uno scambio termico, quanto meno parziale, con il terreno circostante, in analogia ai sistemi geotermici orizzontali superficiali.
Il tema è qui proposto per un adduttore cittadino primario a Ferrara (DN400, 5090 l/s, 825 °C), nell’ipotesi di una rete di teleriscaldamento a bassa temperatura (55 °C) destinato ad un nuovo comparto urbano di 90,000 m3. L’indagine ha sviluppato l’analisi di fattibilità nell’ambito di una ricerca svolta per il gestore del sistema acquedottistico.
Preliminarmente, le prestazioni di un gruppo a pompa di calore (R134a) sono parametrizzate in funzione delle sole temperature agli scambiatori; in analogia, il fabbisogno energetico per climatizzazione è messo in funzione della temperatura oraria dell’aria esterna e della classe energetica dell’edificio (A, B). Noto il regime invernale ed estivo in condotta sia termini di portata, sia di temperatura, è quindi possibile legare il fabbisogno elettrico per climatizzazione alle sole temperature in condotta e in aria, nonché alla classe energetica dell’edificio tipo. L’indagine è sviluppata sia per il caso con sorgente acquedottistica (WS, water source), sia per il caso tradizionale con sorgente l’aria (AS, air source).
Nel contesto considerato, il COP medio giornaliero rimane quasi sempre superiore a 3.6 per il caso WS e superiore a 2.8 per il caso AS. L’insufficienza del sistema WS è raggiunta per una domanda discontinua all’utenza, che determina una elevata potenza al ripristino delle condizioni termiche indoor dopo una prolungata interruzione. Tale eventualità rimane tuttavia remota per sistemi radianti, frequentemente previsti in simili classi energetiche. Il servizio di teleraffrescamento è invece attuabile solo in presenza di un sistema ibrido (AWS, air-water source), a seguito delle elevate temperature in condotta durante il mese di agosto. Più in generale, la soluzione ibrida risulterebbe comunque più adeguata, quale sorgente occasionalmente più vantaggiosa ed a cautela di un eventuale disservizio in rete.
L’analisi economico-finanziaria è condotta impiegando il metodo dei flussi di cassa scontati (Discounted Cash Flow Method), al fine di valutare il payback del sistema ibrido AWS rispetto al tradizionale AS. Al netto di eventuali benefici fiscali e della non monetizzazione di quelli ambientali, il payback del solo servizio di teleriscaldamento risulterebbe accettabile (<10 anni) a fronte di un extra costo del sistema AWS rispetto alla soluzione AS non superiore a circa 250 €/kWt, di un risparmio in gestione non inferiore a 3.4 c€/kWht e con un consumo complessivo superiore a 1,6 MWht/anno. Con l’estensione del servizio al teleraffrescamento, il rientro (<10 anni) dello stesso extra costo (250 €/kWt) si raggiungerebbe per risparmi in gestione pari a 2.3 c€/kWht, a fronte di un consumo di 2.2 MWht/anno (=1.6+0.6).
In presenza di una temperatura in condotta stabile e pari a 14 °C (pozzi idropotabili), il COP migliora di circa mezzo punto e risulta superata l’insufficienza estiva
Alternative experimental characterization of phase change material plasterboard using two-step temperature ramping technique
No full textThe increasing energy demand for heating and cooling is leading to the development of new strategies for reducing energy consumption and greenhouse gas emissions. Phase change materials applied on the building envelope can act as a heat modulation passive cooling strategy, reducing the energy requirement. An essential aspect for an effective application of PCM is the knowledge of its thermo-physical properties, namely heat conductivity, specific heat and latent heat. Differential scanning calorimetry (DSC) is one of the most used techniques, but the characteristics of the sample necessary for the test make it unsuitable for all those inhomogeneous or composite materials for which a small sample may not be representative of their properties. Alternative and unconventional tests have been developed to overcome this limitation and estimate experimentally one or more thermal properties of a selected material. In the research presented here, a new low-cost experimental set up was developed for the experimental estimation of the thermal conductivity, the specific heat and the latent heat of a plaster containing granular phase change materials through both steady-state as well as unsteady-state tests. The estimated values were then used in the numerical modelling of the experimental set up. A good agreement in thermal response between the experimental and the simulated values validates the proposed experimental estimation method.CO 2022 Elsevier B.V. All rights reserved
Energy analysis of a dual-source heat pump coupled with phase change materials
No full textInstallation costs of ground heat exchangers (GHEs) make the technology based on ground-coupled heat pumps (GCHPs) less competitive than air source heat pumps for space heating and cooling in mild climates. A smart solution is the dual source heat pump (DSHP) which switches between the air and ground to reduce frosting issues and save the system against extreme temperatures affecting air-mode. This work analyses the coupling of DSHP with a flat-panel (FP) horizontal GHE (HGHE) and a mixture of sand and phase change materials (PCMs). From numerical simulations and considering the energy demand of a real building in Northern Italy, different combinations of heat pumps (HPs) and trench backfill material were compared. The results show that PCMs always improve the performance of the systems, allowing a further reduction of the size of the geothermal facility. Annual average heat flux at FP is four times higher when coupled with the DSHP system, due to the lower exploitation. Furthermore, the enhanced dual systems are able to perform well during extreme weather conditions for which a sole air source heat pump (ASHP) system would be unable either to work or perform efficiently. Thus, the DSHP and HGHE with PCMs are robust and resilient alternatives for air conditioning
A Management Strategy for Multi-Source Heat Pump Systems
Full text linkThe recent H2020 IDEAS project is oriented to the study of multi-source heat pump systems by investigating their behavior through dynamic simulations and on-field experiments in real small and large-scale prototypes respectively. One of the main aims of the project is the exploitation of available free energy sources, solar, air and ground using the heat pump technology. The key point in the investigated multi-source heat pump system is the optimal management of the renewable sources and the keeping of the ground storage available also in case of undersize of it and in case of buildings with unbalanced thermal load profile. In the last year of the project the algorithm for the control of sources and devices in the IDEAS system has been developed to maximize the use of renewable energies and at the same time to minimize the consumption of auxiliary energy. The present paper shows the details of this part of the project highlighting limits, potential and properties of the management system with a discussion of the results obtained from the on-field experiments. In the last part of the project, the implementation of weather forecast and artificial intelligence in the algorithm is planned
A weather forecast-based control for the improvement of PCM enhanced radiant floors
Full text linkSignificant energy savings and thermal comfort improvement related to radiant floor systems may not be achieved when underfloor heating/cooling is adopted in lightweight building envelopes. Phase change materials (PCMs) are suitable candidates for providing the necessary thermal inertia with a minimum effect on the construction technology. Impacting variables like internal heat gains, weather conditions and dynamic energy price require the adoption of advanced control strategies to ensure and maximise the energy benefits of PCMs. Despite the potential of model predictive control using weather prediction data has been widely examined by the literature, there is a lack of studies experimentally analysing their implementation in PCM enhanced radiant floor systems. Within the H2020 European project IDEAS the integration of PCMs in a radiant floor system was examined by the University of Ferrara through numerical and experimental investigation. A first prototype was then installed in a small experimental building characterised by a low thermal capacity. Analysis of the monitoring data for the heating period showed that solar radiation strongly impacts on the lightweight building envelope in a short time. Without suitable control, the contribution of PCM that slowly reduced its heat flux during its transition, together with solar heat gains, resulted in an excessive increase in indoor air temperature, wasting the PCM energy saving potential. The aim of the study is the evaluation of a control strategy to improve the management of PCM enhanced radiant floor systems in relation to forthcoming weather conditions in lightweight buildings. The control routine was implemented in the corresponding dynamic energy model in TRNSYS. Results estimated achievable energy saving equal to about 4% and 8% on the heating and the cooling energy demand respectively
Study on thermal performance of a PCM enhanced hydronic radiant floor heating system
No full textRadiant floor systems enhanced with Phase Change Materials (PCMs) could achieve significant energy savings while improving the thermal comfort of occupants in lightweight buildings. Effective integration of PCMs typically requires customised solutions based on a comprehensive analysis due to their complex nature. The objective of the present study is the experimental and numerical investigation of a hydronic radiant floor heating system integrated with macroencapsulated PCM. Experimental tests were carried out on a laboratory-scale by the University of Ferrara, Italy, within the H2020 European project IDEAS. A 2D model was then implemented in COMSOL Multiphysics and calibrated in steady as well as in transient state according to the experimental tests. The behaviour of the system, including temperature distribution and heat flux, were analysed under different conditions. The impact of using dry and wet sand, as well as the effect of the position of PCM – above or under heating pipes – on thermal performance, were investigated. Results showed that the use of high thermal conduction in mortar increases much faster the overall performance of the PCM integrated underfloor heating system. Furthermore, the coupling technology with PCM containers installed under piping significantly enhances the positive effect of wet sand
A new approach for the transposition of a geological structure in a deterministic multilayer model
No full textIn a multilayer approach for a numerical modeling of an aquifer, a correct evaluation of stratigraphic columns allow first to define the geological units surfaces and then to build a proper geological model that must also represent the reference for the three-dimensional deterministic model. When the geological units are directly converted into the layers of the deterministic model, the evaluation of the hydrogeological parameters may result incoherent. The presence of a high hydraulic conductive lens disposed within an aquitard unit, in fact, may considerably alter the related characteristics.
A different approach can be followed by deepening the stratigraphic columns discretization through the hydrodynamic characterization of the granulometries when these are substantially different. This procedure determines the number of representative layers for each column. A further procedure is then necessary to render homogeneous the sample in terms of layers number. The number resulting from the last homogenization process, coincides with the number of the deterministic model layers.
In this paper the previous procedure is presented, together with the module development in Access in order to obtain a digital layout for FEFLOW. The reliability of the results is finally investigated with respect to data availability
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