The development of zero-energy buildings (ZEBs) is a critical pillar for designing the sustainable cities of the future. Photovoltaics (PVs) play a significant role in the design of ZEBs, especially in cases with fully electrified buildings. The goal of this analysis was to investigate different advanced PVs with integrated cell cooling techniques that can be incorporated into buildings aiming to transform them into ZEBs. Specifically, the examined cooling techniques were radiative PV cells, externally finned PVs and the combination of PVs with phase-change materials. These ideas were compared with the conventional PV design for the climate conditions of Athens, Barcelona, Munich and Stockholm. At every location, two different building typologies, B1 (a five-story building) and B2 (a two-story building), were investigated and the goal was to design zero-energy buildings. In the cases that the roof PVs could not cover the total yearly electrical load, building-integrated photovoltaics (BIPVs) were also added in the south part of every building. It was found that in all the cases, it is possible to design ZEB with the use of roof PVs, except for the cases of B1 buildings in Munich and Stockholm, there is also a need to exploit BIPVs. Moreover, a significant electricity surplus was reported, especially at the warmest locations (Athens and Barcelona). Among the examined cooling techniques, the application of the fins in the back side of the PVs was determined to be the most effective technique, with radiative cooling to follow with a slightly lower performance enhancement. The application of PCM was found to be beneficial only in hot climate conditions.

Building energy renovation planning should be based on a multi-criteria evaluation that targets both reduced energy consumption and a high-quality indoor thermal environment. The present study investigates the building energy retrofit technologies of thermal insulation, highly insulative windows, mechanical ventilation for cooling purposes, and shading, aiming to identify the optimum energy retrofit strategy for different building typologies. Indoor thermal comfort is evaluated with the thermal comfort indexes of the predicted mean vote (PMV) and the Predicted Percentage of Dissatisfied (PPD). Each renovation scenario is evaluated in terms of thermal performance and thermal comfort, while an optimum retrofit scenario is defined as the one that simultaneously achieves the maximum decrease in the yearly energy demand and the greatest decrease in the building’s indoor thermal discomfort. The multi-objective analysis is performed using the EnergyPlus simulation engine, which is used to perform yearly dynamic simulations and provide accurate results. This study considers a typical one-story apartment building located in the city of Athens, Greece. According to the calculations, the retrofit strategy that combines all four examined interventions results in an 11.8% and 56.1% decrease in the building’s heating and cooling energy demand, respectively, while an annual enhancement of 16.6% in the building’s thermal comfort PPD index is calculated.

This study suggests a newly developed model for estimating city-scale photovoltaic rooftop energy potential. This model aims to provide reasonable universal calculations regarding a city’s available space for mounting rooftop photovoltaic systems and their corresponding annual electricity production capacity. For the development of the model, a thorough literature review has been conducted, which compiles and presents mathematical expressions and performance coefficients. Necessary geographic and meteorological data have been obtained from European statistical repositories and the PVGIS tool, respectively. The main inputs refer to a city’s basic geographical data, population, total actual area, geographical coordinates, and, by extension, the optimum PV unit installation angle. This analysis presents a simple and accurate model applicable to European cities for assessing rooftop photovoltaic energy potential and suitable rooftop space for PV units. The findings can aid in advancing PV development in urban areas and contribute to creating environmentally neutral cities in the future. The methodology is verified with data retrieved from the Google Environmental Insights Explorer tool, which shows a deviation of 9.72%. According to the computational analysis for 40 European countries, the photovoltaic energy potential is between 12.31 GWh and 8200 GWh. These values correspond to a net available PV space between 0.03 km² and 31.86 km². The greatest photovoltaic coverage potential is equal to 117.4% for Patras, Greece, while the lowest is 7.27% for Oslo, Norway. Regarding the avoided greenhouse gas emissions, they are found to vary from 5.8 ktons of CO_2-equivalent for Valletta, Malta, and 8109.8 ktons for the city of London, United Kingdom. Finally, the final results of 86 additional cities located on the European continent are given.

Escalating climate change and the increasing frequency of weather extremes pose a threat to the resilience of urban environments and human health, highlighting the urgent need for implementing energy-efficient interventions and reducing building cooling loads. This study investigates the passive building envelope retrofit technologies of external shading, electrochromic windows, and thermochromic windows through a multi-criteria evaluation analysis based on energy savings, economic performance, and indoor thermal comfort improvement. Thermochromic windows are discerned by a mean colour transition temperature of 34 °C and operate throughout the entire year, while electrochromic windows are activated only during cooling periods. Both technologies present total solar transmittance indices of 72.6% and 8.4% in the bleached and tinted state, respectively. External shading devices are either static or movable, applied with an inclination angle, and are either standalone interventions or combined with chromogenic glazing. Eight retrofit scenarios are investigated for a single-story, fully electrified residential building in Athens, Greece. The building features south- and east-oriented windows, which is an appropriate case to assess the effectiveness of these passive envelope cooling technologies in regulating solar heat gains. Thermal comfort is assessed using Fanger’s PMV (predicted mean vote) and PPD (Predicted Percentage of Dissatisfied) indices. The combination of electrochromic windows and movable external shading yields the highest annual electricity savings at 22.2% and reduces the PPD by 15.8%. Local static shading, on the other hand, ranks as the optimal retrofit solution in terms of economic performance, with a life-cycle cost of €6378, a 9.3% improvement in thermal comfort, and a corresponding reduction of 626 thermal discomfort hours. While the proposed multi-criteria framework can be applied to other buildings and climates, the quantitative results reported here are linked to the specific case examined: a residential building with south- and east-facing glazing in Athens, Greece, representing Mediterranean climatic conditions.

Prosumer energy storage behavior alongside national rooftop photovoltaics (RTPV) penetration metrics is essential for decarbonization pathways in buildings. A research gap persists in quantitatively assessing storage strategies under varying regulatory frameworks that integrate both technical and financial dimensions while accounting for behavioral heterogeneity and policy feedback. This study introduces a novel degradation-aware, feedback-preserving framework that optimizes behind-the-meter storage design and operation, enabling realistic modeling of prosumer responses on large-scale RTPV adoption scenarios. Long Short-Term Memory (LSTM) and Compound Annual Growth (CAGR) models applied for the RTPV penetration rates projections in European urban contexts. The increasing rates in the Netherlands, Spain, and Italy respond to second-order regression behavior, with the former to emit signals of saturation and the latter to perform mixed anelastic and reverse elastic curves of elasticities. Accordingly, Germany, France, the United Kingdom (UK), and Greece remain in an inelastic area by 2030. The building RTPV energy storage arbitrage formulation is treated as a linear programming (LP) problem using a convex and piecewise linear cost function, a Model Predictive Control (MPC), Auto Regressive Moving Average (ARMA) and Auto Regressive Integrated Moving Average (ARIMA) statistical forecasts and rolling horizon in order to address the uncertainty of the load and the ratio κ of the sold to purchased electricity price. Weekly arbitrage gains may drop by up to 9.1% due to stochasticity, with maximized gains achieved at battery capacities between 1C and 2C. The weekly gain per cycle performs elastic, anelastic, and reverse behavior of the prosumer across the range of κ values responding to different regulatory mechanisms of pricing. The variability of economic incentives suggests the necessity of flexible energy management strategies.

Industrial heat demand is a major source of CO₂ emissions, making the decarbonization of this sector essential for achieving sustainability. This study explores and compares different methods for supplying useful heat to the industrial sector through a multi-criteria approach that considers technical performance, economic viability, and environmental impact. Both conventional and alternative systems are examined, aiming to develop sustainable designs. These include solar-based systems using parabolic trough collectors, supported by either electric heaters or natural gas boilers. In addition, a high-temperature heat pump (HTHP) utilizing waste heat is analyzed, also combined with either electric heaters or gas boilers as backup. For reference, a conventional natural gas boiler system is included as a baseline case. In total, five scenarios are evaluated for applications in the chemical industry. Each scenario is assessed in terms of energy and exergy efficiency, cost, and CO₂ emissions. A multi-criteria analysis is then applied to determine the most sustainable option under varying electricity and waste heat price conditions. The results indicate that the configuration combining a high-temperature heat pump with electric heaters (Scenario 3) achieves the highest performance, with energy and exergy efficiencies of 0.952 and 0.666, respectively. The lowest CO₂ emissions are observed in the case of using solar collectors with electric heaters (Scenario 1), reaching 4154 tons per year. From an economic perspective, Scenario 3 emerges as the most favorable option at lower electricity prices (0.10 €/kWh), with a levelized cost of heating (LCOH) of 0.0555 €/kWh. At higher electricity prices, the optimal design shifts to Scenario 2, which combines solar collectors with a natural gas boiler, resulting in an LCOH of 0.0603 €/kWh.