The exploitation of forest and agricultural biomass residues for energy production may offer significant advantages to the energy policy of the relevant country, but it strongly depends on a number ...of financial, technological and political factors. The work in hand focuses on the investigation of the energy, environmental and financial benefits, resulting from the exploitation of forest and agricultural biomass residues, fully substituting the conventional fuel (diesel oil) for building space heating in Greece. For this investigation, the energy needs of a representative building are determined using the EnergyPlus software, assuming that the building is located across the various climate zones of Greece. Based on the resulting thermal energy needs, the primary energy consumption and the corresponding emissions are determined, while an elementary fiscal analysis is also performed. The results show that significant financial benefits for the end-user are associated with the substitution examined, even though increased emissions and primary energy consumption have been derived.
•The application of heat storage in geothermal district heating networks was studied.•Integrated algorithms for the sizing and operation of the installation were built.•Heat losses in the pipelines ...decrease substantially with the developed algorithm.•The proposed solution is cheaper and more environmentally friendly.•The effect of a financial subsidy in a renewable project was highlighted.
Geothermal energy is a renewable energy source which can provide base-load power supply both for electricity and direct uses, such as space heating. In this paper, district heating systems that are fed by geothermal energy, the so-called geothermal district heating systems, are studied. It is proposed to apply a hot water storage tank in these systems to store hot water in times of low-load and release it to the system during peak load periods in order to minimise the use of peak-up boilers.
In this paper, two different models are presented and the results are shown for three different cases of heat demand coverage by geothermal energy. First, a model for the sizing of these systems is developed. The main findings highlight the importance of the insulation both for the storage tank and the pipelines of the network. Secondly, a model that studies the daily and the annual operation of the installation is developed followed by an integrated economic and environmental analysis of the proposed solution. The results indicate that the proposed solution is financially beneficial compared to the traditional case without use of the storage tank as all the financial indices and cash flows are improved. More specifically, the levelised cost of heating decreases by 4.3–14.9% leading to an increased potential income of £87,000–241,000 per year, while the NPV, the IRR and the BCR all increase. Furthermore, the emissions decrease by up to 54.2% and the load factor increases by up to 3.86%. Therefore, the proposed solution is proved to be beneficial from an economic, environmental and energetic point of view as more geothermal energy is utilised in a more economical way with subsequent environmental benefits.
The aim of this paper is to present a new procedure for the calculation of equivalent full-load hours of operation for heating and cooling systems, from hourly temperature bin data. Following the ...procedure and using dry-bulb temperature bin data, equivalent full-load hours for 40 Greek cities were calculated. Results are given in tabular form and data for both heating and cooling periods are presented. For the heating period the resulted data were calculated considering a 24-h operation of the heating equipment while for the cooling period, in order to distinguish between different types of building function, data for 12 and 24
h of operation of the cooling equipment are presented. Furthermore, in order to take into account the influence of building construction, internal heat gains and indoor design temperature on the energy requirements, different balance-point temperatures are considered either for the heating or the cooling period. Equivalent full hours may be used for a rough estimation of annual heating and cooling energy requirements in buildings.
The paper presents the basic parameters and the energy flows of a ground source heat pump system (GSHP) used for air conditioning the New City Hall of Pylaia (Thessaloniki area—Northern Greece). The ...building is a typical public one, with an air-conditioned area of 1350
m
2. The ground source heat pump installation is the largest in Greece, and its operation is monitored with the aid of a DAQ system. The energy flows presented in the paper are based on DAQ recordings of the first 3 years of system's operation. It is proved that the energy demand of the system is significantly lower, compared to that of conventional heating and cooling systems. The seasonal COP of the system has not yet been stabilized, gradually increasing, as it is expected due to the operation of the ground heat exchanger.
Carbon nanotubes (CNTs) have attracted great interest for applications due to their unique mechanical, electronic and optoelectronic properties. The advantages of the multiple wall carbon nanotubes ...for optoelectronic devices like photodetectors and photodiodes are the large effective photo-collector surface as well as the possibility to tune the band gap and absorbance by controlling the growth parameters. In this work, we demonstrate two types of hybrid Multi-Wall CNTs/Si3N4/n-Si photodetectors based on ordered (produced with Chemical Vapor Deposition – CVD) and solution processed MWCNTs and evaluate their performance in UV and visual spectrum (275 nm, 655 nm). Device parameters were obtained by comparison of I–V characteristics to Schottky barrier models and C–V characteristics to standard MIS capacitor models. The role of silicon nitride layer was also examined by comparing devices with different nitride layer thickness. Focusing on the UV part of the spectrum, the solution processed device was photosensitive in the voltage range 3V–6V giving its best performance (External Quantum Efficiency - E.Q.E. 85%@275 nm) at 5V and illumination of 5 μW. The CVD processed device showed lower EQE for the same bias voltage range. Both devices showed a low performance in optical part of the spectrum compared to the corresponding one in the UV part of the spectrum. The mean optical responsivity values obtained at the UV part of the spectrum in both cases indicate that the Visible light blind MWCNT/Si3N4/n-Si system have a potential use in UV photodetector applications. In particular, solution processed devices may pave the way for cheap production of UV sensor systems.
•We fabricate two types of hybrid Multi-Wall CNTs/Si3N4/n-Si photodetectors based on ordered (produced with Chemical Vapor Deposition – CVD) and solution processed MWCNTs and evaluate their performance in UV and visual spectrum (275 nm, 655 nm).•The basic device and some meaningful variations including different CNTs processes and different insulator thicknesses are electrically and optically tested and compared.•Focusing on the UV part of the spectrum the solution processed device was photosensitive in the voltage range 3V–6V giving its best performance (External Quantum Efficiency - E.Q.E. 85%@275 nm) at 5V and illumination of 5 μW.•The aim of this work is to demonstrate that the growth of dense ordered MWCNTs or solution processed MWCNTs can be successfully combined with other semiconductor clean room processes in order to fabricate photodetectors.
•We fabricate a hybrid MWCNT/Si3N4/n-Si photodetector based on ordered MWCNTs and evaluate its performance in the UV, visual and near IR spectrum (200–1000 nm).•The basic device and some meaningful ...variations including additional layers are electrically and optically tested and compared.•The overall results suggest that all devices had a satisfactory performance in the visual part of the spectrum and that the basic structure had the better performance as a UV detector (EQE 90% @ 275 nm@ 7 V).•The aim of this work is to demonstrate that the growth of dense ordered MWCNTs can be successfully combined with other semiconductor clean room processes in order to fabricate photodetectors, provided that the side effects are taken into account and the process flow is selected appropriately.
Multiple wall carbon nanotubes (MWCNT) present advantages for optoelectronic applications such as the large effective photo-collector surface as well as the possibility to tune their band gap and absorbance through the growth parameters. We demonstrate a hybrid MWCNT/Si3N4/n-Si photodetector based on ordered MWCNTs and evaluate its performance in the UV, visual and near IR spectrum (200–1000 nm). The basic device and some meaningful variations including additional layers are electrically and optically tested and compared. The overall results suggest that all devices had a satisfactory performance in the visual part of the spectrum and that the basic structure had the better performance as a UV detector (EQE 90% @ 275 nm@ 7 V). The aim of this work is to demonstrate that the growth of dense ordered MWCNTs can be successfully combined with other semiconductor clean room processes in order to fabricate photodetectors, provided that the side effects are taken into account and the process flow is selected appropriately.
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