• Energy Research

Abstract The current paper presents the main steps in the design of large-scale photovoltaic (PV) power generation plants in University campuses towards their energy independence. As an example is used the campus of the Technical University of Crete as a base case to describe the design. Today the insular power system of Crete is based on oil fuel by 75%. Solar electricity is designed and discussed in this report. For this scope, the energy consumption figures of the buildings within the campus are analyzed. In parallel, a feasibility study of the PV energy generation is conducted revealing their potential contributions and applicability. The resultant electrical energy generation design satisfies the project objective by utilizing alternative energy sources and reducing the greenhouse gas emissions of the campus. The results obtained are satisfactory being both technically and economically feasible. To conclude, these designs proposed in this project can be the first steps towards a 100% green energy campus and get even more tempting with relevant technological improvements in the future.

Abstract This study presents a 2-years performance assessment of a 2.18 kWp grid-connected PV (photovoltaic) system, installed in the premises of the Technical University of Crete, Chania; important normalized parameters such as yields, losses and efficiencies are calculated and related to the local climatic characteristics. The scopes of this paper are: (i) the quantification of the effect of high temperature conditions on the electrical performance of a thin film PV system; (ii) the verification and comparison amongst the existing empirical models used to estimate PV frames operating temperature emphasizing on the accuracy of their predictions; (iii) the development of a new customized empirical model in order to determine the PV frames operating temperature, under real field conditions. The output provides safe estimates and information about the potential improvements in order to create small and large scale thin film PV installations in areas with similar climatic characteristics such as the Mediterranean coastal areas.

Decentralized multi-energy systems (MESs) are a key element of a future low-carbon energy supply. Here, we address the crucial role of grid-connected and off-grid MESs in achieving a low-carbon future, particularly relevant for regions like the Mediterranean with high renewable energy potential and carbon-intensive grid networks, using a mixed integer linear program for optimal economic and environmental MES design considering location-specific regulations. The results reveal that substantial cost (up to 30%, potentially saving 1.6 million) and greenhouse gas (GHG) emission reductions can be reached in Mediterranean regions with sufficient solar and wind energy resources currently relying on fossil fuel-based generators. However, our case study shows that the actual cost and emission reductions are most likely limited due to location-specific regulations (limiting cost savings to 0.8 million), especially those that constrain solar photovoltaic and onshore wind. Off-grid energy systems might be suitable decarbonization options in Mediterranean regions, to avoid absorbing current GHG-intensive power from the local power grid, under marginal cost increase (15%) compared to grid-connected cost optimization. However, off-grid MESs require substantial upfront investments and exhibit some environmental trade-offs, especially on material utilization, which could be overcome by balanced autonomy. Overall, truly sustainable and secure decentralized energy systems can only be reached by considering life cycle environmental impacts, social acceptance, and regulations during the design phase. Applied Energy, 377 ISSN:0306-2619 ISSN:1872-9118

Abstract Engaging communities to action under the new climate change regime and fostering citizens to adopt sustainable energy patterns, remains still a challenge. A new impetus for commitment was put in place for local regions, through the Covenant of Mayors (CoM) initiative by the EU communities. The key challenge is the penetration of Renewable Energy Sources (RES), since most rural communities have vast unexploited RES potential (solar, wind, biomass, etc.). RES promotion could also specifically support rural communities’ challenges as regards growth, jobs and sustainability, which are also aggravated by the current financial and economic crisis. One of the most significant steps throughout participating in this initiative is the evaluation of the community's sustainable energy status. Aim of this paper is to assess rural communities’ energy sustainability using the Principal Component Analysis (PCA), based on the outputs of two European “Intelligent Energy For Europe” projects on the following regions: Mountainous and Agricultural Communities and Islands. Appropriate customization of the PCA will be elaborated, to aggregate sustainability indicators, capture related interactions and interdependences. The results of this study can support the monitoring of such communities’ progress, which is an especially valuable parameter as concerns the development and mainly implementation of their Sustainable Energy Action Plans.

REScoops are cooperatives of renewable energy producers and/or consumers that are being formed in the developing European Smart Grid. Today, there are more than 2397 REScoops with more than 650,000 members. Their development indicates the necessity of producing and consuming green energy, assists the fight against energy poverty, and reduces greenhouse gas emissions by utilizing smart management systems and self-consumption techniques. An essential objective of the H2020 REScoop Plus project is to stimulate better understanding and promote the cooperatives’ commitment to behavioral change. To achieve such a goal, this paper presents the methodology adopted to assess the energy-saving activities and behavior of the REScoops. In order to obtain relevant conclusions, a detailed statistical analysis was undertaken. Moreover, the analysis led to an effective classification of the various members, providing insights regarding their contribution to consumption reduction according to various specific characteristics. The statistical analysis showed that REScoop members contribute significantly to energy conservation and the reduction of harmful gas emissions, and subsequently, the majority of the energy efficiency (EE) interventions led to achieving more than 20% reductions. Specific practices, already adopted by the REScoops, lead to increased energy efficiency and environmental benefits.

Abstract In several European rural communities, woody biomass is considered amongst the most important energy sources for heating and cooking. However, the use of old-fashioned fireplaces may affect indoor and outdoor air quality. To depict this situation and to plan the necessary improvement interventions, a pilot action was implemented in a typical mountainous Mediterranean area (town of Anogeia, Crete). The action involved: (i) identification of the quantities, use and source of the woody biomass used in the community based on the analysis of data collected through a systematic survey; (ii) on-site indoor and outdoor measurements of air quality (CO2, CO, NOX, PM), during wintertime and summertime. Based on the current survey, around 70% of the study area households in Anogeia using woody biomass for heating purposes in low energy efficiency systems resulted in high annual consumption of firewood. Fifty-three per cent of occupants didn’t consider indoor air quality as a result of wood burning. The analysis of the air quality showed very high concentrations of indoor air pollutants in the majority of old buildings with seniors using traditional heating systems. The type of main/supplementary heating system used in a dwelling depends on factors such as the size of the dwelling, year of construction, education level and age of occupants. The results also demonstrate a strong correlation/liaison between the heating season (summertime/wintertime), and the (significant increase in the) concentrations of air pollutants in the sampling sites.

Abstract The significance of the temperature effect on the performance of photovoltaics (PVs) has implied the necessity to develop PV cooling methods in recent years. In this research, the inclusion of phase change materials (PCMs) through an alternative type of enclosure in tubular shape was proposed and investigated as an option of mitigating the PV operating temperature to enhance their efficiency and lifetime. Two PVs incorporating different PCMs (PV + PCM systems) and a conventional PV module (reference case) were experimentally tested to assess their energy performance under the Mediterranean conditions in Chania, Crete. As PCMs employed were selected Paraffins RT 27 and RT 31. The results indicated that a peak temperature decrement of 6.4 °C and 7.5 °C could be observed by using 260 g of PCM27 and PCM31, respectively. Hence, PV + PCM27 and PV + PCM31 systems exhibited increased energy generation by 4.19% and 4.24%, respectively, while the increment in the PV conversion efficiency by PCM integration ranged from 2.86 to 4.19%. The proposed configuration of PCM enclosures took advantage of the synergistic effect of wind, as demonstrated by the recorded daily temperature profiles of the PV + PCM27 and PV + PCM31 systems, even after the time of complete PCMs' melting.

Abstract The temperature of the photovoltaic systems during their operation is a crucial determinant of their energy performance, life cycle and efficiency. A modified photovoltaic system (PV + PCM system) combining a conventional photovoltaic module (PV) with a selected type of phase change material (PCM) is designed and assessed in Mediterranean climate during a year-long period. This type of analysis allowed to recognise the core operational aspects (e.g. seasonal performance, stability) of such a system and serve a deeper understanding of the potential faults and underestimations. According to the results of this study, the operating temperature difference could arise up to 26.6 °C, so the yearly power generation of the new system increases by 5.7%. The obtained results provide essential findings on the benefits of the proposed system and complement the existing literature in terms of the real field experience of this configuration’s operation.