This paper presents a practical methodology to facilitate decision-making for the development of a renewable energy community (REC) in the municipality of Hersonissos in Crete, Greece. The impact of energy sharing produced from renewables through direct or indirect citizen participation presents an enormous opportunity to strengthen energy democracy and to alleviate energy poverty. Triggered by the latter being amongst the most essential goals for implementing policies towards low-carbon economies at the local level, the current study presents a step-by-step methodology to facilitate decision-making for building a municipality-led REC. Initially, potential sites and alternative sittings of photovoltaic (PV) plants are explored for detecting the optimal installation with respect to technical and possible legislative restrictions. The best REC business model is then selected based on a SWOT analysis, complemented with a detailed techno-economic analysis of the foreseen investments. According to the design calculations, the optimal PV plants/business-model option that emerged may achieve impressive environmental and economic benefits, i.e., reducing the municipality’s annual electricity-induced CO₂ emissions and electricity expenses by at least 68.40% and 594,461.54 €, respectively.

According to the latest energy efficiency European directive (EED 2023/1791/EU), the expected energy renovation rate of at least 3% of the buildings’ floor area each year towards nearly zero-energy buildings (nZEBs) is extended to include public buildings not only of the central government (as per the first EED 2012/27/EU) but also of regional and local authorities. This poses a great challenge, especially for Municipalities that often manage large building stocks with high energy demands. In response to this challenge, this paper presents the application of the so-called “typology approach” for conducting public buildings’ energy renovation plans at the local level. A computational survey is initially introduced to decide the optimal set of building-stock clustering criteria among all possible combinations, involving the minimization of the RMSE index regarding the primary energy consumption of each building. For a representative building from each identified typology, the key performance indicators (KPIs) are computed for alternative energy-upgrading scenarios. Exploiting the IMPULSE Interreg-MED project tools, the KPIs from each representative building are at first extrapolated to all buildings of the examined stock and, finally, a gradual energy renovation plan is automatically produced based on user-defined decision parameters including the required annual renovation rate. The methodology is applied for the case of the Municipality of Hersonissos in Greece. For the specific 44-buildings’ stock it was found that the optimal clustering set included four criteria, building use, construction year, heating, and a cooling system, leading to 15 building typologies. Finally, assuming a 7% renovation rate per year, a 12-year gradual renovation (nZEB transformation) plan is obtained foreseeing an 85% CO₂ emissions’ reduction.

In view of the European Union’s strategy on hydrogen for decarbonization and buildings’ decarbonization targets, the use of hydrogen in buildings is expected in the future. Backup power in buildings is usually provided with diesel generators (DGs). In this study, the use of a hydrogen fuel cell (HFC) power supply backup system is studied. Its operation is compared to a DG and a techno-economic analysis of the latter’s replacement with an HFC is conducted by calculating relevant key performance indicators (KPIs). The developed approach is presented in a case study on a school building in Greece. Based on the school’s electricity loads, which are calculated with a dynamic energy simulation and power shortages scenarios, the backup system’s characteristics are defined, and the relevant KPIs are calculated. It was found that the HFC system can reduce the annual CO₂ emissions by up to 400 kg and has a lower annual operation cost than a DG. However, due to its high investment cost, its levelized cost of electricity is higher, and the replacement of an existing DG is unviable in the current market situation. The techno-economic study reveals that subsidies of around 58–89% are required to foster the deployment of HFC backup systems in buildings.

Ever since European Directive 2012/27/EU, particular attention has been focused on the improvement of the energy efficiency of the public building stock. According to the directive, local public authorities, regions and municipalities, are expected to develop and implement energy efficiency retrofitting plans for their public building stocks. While conducting such plans, important challenges are raised mainly related to data collection and the manipulation of key performance indicators (KPIs) for many buildings. The present paper deals with the aforementioned challenges through (a) the evaluation of freely available tools developed in the framework of Mediterranean territorial cooperation projects, with respect to the main pillars of energy efficiency planning, and (b) the introduction of a stepwise methodology using selected tools toward a reliable energy efficiency plan extending from the classification of the building stock to the prioritization of projects in terms of a gradual renovation plan based on energy and cost criteria. The methodology is applied for a case study in Greece, which refers to 10 public buildings of the Municipality of Aigialeia in Greece. A reliable renovation plan is developed, taking into account the municipal authority’s directions in a specialized decision-making scheme. It is concluded that the suggested methodology is very practical for planning purposes, while for the case studied, a 6-year gradual renovation plan is emerged until a deep retrofit of all buildings, associated with an estimated primary energy saving and CO₂ emissions avoidance of more than 1850 MWh and 400 tns, respectively, with a total investment of about EUR 3 million.

The development of electric vehicles (EVs) as part of the electrification of the transportation sector plays a significant role in energy transition to a low-carbon and highly renewable society. The use of EVs has been promoted through the development of inclusive strategies for electromobility in the recent years. Apart from actions directed and funded by the European Union, national strategies have also been employed to support electromobility. Such a strategic plan has already been enacted by the Hellenic Ministry of Environment and Energy, funding municipalities to prepare siting and sizing plans for electric vehicle chargers. In this paper, the final study of this strategic plan for the municipality of Heraklion in Crete is used as a case study to investigate the effect of EV chargers on the operation of the Cretan power system. Their selected siting points are evaluated by performing a power flow analysis at the level of 150 kV. Thus, they are aggregated in each 20 kV/150 kV distribution substation of the electrical grid with the aim of investigating their effect on substation loading and transmission line losses. Generally, extensive fast charging should be avoided to minimize the risk of sudden stress of the existing cities’ grids and control strategies should be implemented to mitigate the need for upscale substation equipment or even postpone reinforcements.

The current research presents a practical approach to assess energy performance and thermal comfort in households through monitoring campaigns. The campaigns are conducted in a Greek city, involving the installation of low-intrusive recording devices for hourly electricity consumption, indoor temperature, and relative humidity in different residences in winter and summer periods. The recorded indoor environmental conditions are initially compiled to the Predicted Mean Vote (PMV) index, followed by the formulation of databases of hourly electricity consumption, PMV and local outdoor climate conditions retrieved by an official source of meteorological conditions. A special algorithm for database processing was developed which takes into account the eligibility of data series, i.e., only the ones corresponding to non-zero electricity consumption are treated as eligible. First, the sequential temporal progress of energy consumption and thermal comfort is produced towards the assessment of energy-use intensity and thermal comfort patterns. Secondly, through summing of the electricity consumption within 0.5-step PMV intervals, under three outdoor temperature intervals with approximately the same number of eligible measurements, reliable interrelations of energy consumption and PMV are obtained even for residences with limited amount of measured data. It is revealed that the weekly electricity consumption ranged within 0.15–3.59 kWh/m² for the winter cases and within 0.29–1.72 kWh/m² for the summer cases. The acceptable range of −1 ≤ PMV ≤ 1 interval holds an occurrence frequency from 69.46% to 93.39% and from 37.94% to 70.31% for the winter and summer examined cases, respectively. Less resistance to discomfort conditions is observed at most of the summer examined households exhibiting the electricity peak within the 1 ≤ PMV ≤ 1.5 interval, contrary to the winter cases for which the electricity peak occurred within the −1 ≤ PMV ≤ −0.5 interval. The study provides graphical relationships of PMV and electricity consumption under various outdoor temperatures paving the way for correlating thermal comfort and energy consumption.