The use of photovoltaic (PV) solar energy for self-consumption has shown clear benefits in promoting a sustainable campus of Higher Education Institutions (HEIs) [1,2^[1][2][3],3], especially in terms of the site’s carbon footprint reduction, energy costs reduction, or the possibility of reselling the electric energy generated to the national electricity grid when local regulation allows a situation of that kind. Solar panels are connected directly to the grid via inverters; therefore, the energy produced can be transmitted to the site for self-consumption, and, if possible, the excess can be sold to the national electric network and returned to the grid. There are, however, some situations in which the local grid operator does not allow the injection of electricity into the grid, shaping, therefore, a local network without authorization to export the produced energy that is designed to comply with the rules of a specific funding project or meet some specific regulation requirements. From the public energy supply network point of view, the injection of active energy is necessary to reduce pressure on the power grid and limit the reinforcement costs; however, the excess of locally produced energy is not always allowed to be exported. Based on this drawback, the question that needs to be answered is the following: what should be done when the site has excess power generation that cannot be injected into the grid, and how can different amounts of energy produced throughout the year be managed efficiently?

To help answer the question, a case study consisting of a photovoltaic solar system in a self-consumption regime, without energy injection into the public grid, was installed at the campus of the Technology and Management School of Polytechnic Institute of Viana do Castelo, Northwest Portugal; it constituted 225 monocrystalline PV modules (2.12 m × 1.05 m per module), with a peak power of 102.37 kWp covering a total installed area of 500.85 m². The PV system is a two-column solar carport mounting system installed in a single bay and was designed to be a shield for parked cars by providing sun shading while generating energy. The solar panels face west and have a 10° incline. The energy produced by the PV system varies throughout the year, and energy storage using batteries deals with the accumulators’ low durability and reduced lifetime.

The growing concern about climate change and the urgent need to reduce greenhouse gas emissions have led to a greater interest in renewable energy sources by HEIs, where photovoltaic systems, due to their low investment cost, ease of installation [4^[4][5],5], low maintenance needs, and quick assembly, are the most popular renewable energy solution; they are mainly used in southern European countries where solar availability is high. However, most funding programs that are mobilized to support system installation costs determine that electricity injection is prohibited, creating the so-called zero export systems. In practice, a “zero export system” implies that no part of the solar energy produced by the system is allowed to enter the grid and that excess solar energy is cut off by an injection limiter. The scenario is aggravated by the fact that in schools and universities, the demand for electricity on weekends and holidays is lower; therefore, there is a surplus of electrical production that must be managed smartly.

2. The Smart Use of PV Solar Energy in Higher Education Institutions

The urgency to mitigate climate change through reduced carbon emissions has heightened the focus on sustainable energy solutions, with solar energy taking a central role due to its clean, abundant nature. Universities, as microcosms of larger society, serve as critical platforms for the demonstration and promotion of sustainability. They are uniquely positioned to lead by example, integrating solar energy systems into their infrastructure, thereby educating and influencing the next generation of policymakers, engineers, and consumers. Through robust research programs, universities can explore innovative solar technologies, assess their feasibility, and optimize their integration into existing energy grids. Research initiatives can also provide valuable data on performance and environmental impact, promoting continuous improvement in solar technology and encouraging its wider adoption. This research, especially when disseminated through academic and industry publications, raises awareness of solar energy’s potential and challenges, guiding policy decisions and incentivizing investments. By championing solar energy, universities contribute to a culture of sustainability, inspiring other sectors to adopt these practices and technologies, thereby amplifying the transition towards a low-carbon future [10]^[6]. Several examples can be found that deal directly with the installation of PV systems on university campuses. However, following the focus of the current research, the use of carport systems is not so common, and the advantages of the system are not completely identified yet, or at least not yet sufficiently valorized. Alghamdi et al. addressed the subject as being a unique and innovative approach to harnessing solar power using car parking areas, which often remain an underutilized urban space, for the installation of solar photovoltaic (PV) systems [11]^[7]. One of the standout aspects of this research is its ability to turn a traditionally overlooked space, as the car parking areas usually are, into potential hubs of renewable energy. The researchers state that the projected 50% return on investment over 25 years at an export tariff of USD ¢4.5/kWh is promising, especially when considering the dual benefits of power generation and car shading. However, a crucial observation is the comparison of estimated generation tariffs with existing PV projects. While the research’s tariff requirements are slightly higher, this could be attributed to the smaller scale and higher cost/kWp of the current PV deployment. As the scale of PV deployments increases, and as labor costs are adjusted for local conditions (like in Saudi Arabia), the tariffs could become more competitive. Their work shows that by using these parking areas on the selected campus, a photovoltaic installation with a capacity of 36.4 MWp can generate up to 66.2 GWh of electricity per year [11]^[7]. Returning to the initial item of the advantages of the carport system, besides the obvious energy generation, the integration of PV systems in car parks offers indirect benefits. In regions with extreme temperatures, these canopies provide necessary shade, reducing the energy required for car air conditioning. Moreover, carport canopies offer protection against harsh weather conditions, enhancing comfort and safety for individuals and vehicles alike. These PV installations in dense urban settings can significantly offset energy imports for large organizations, showing the potential for large-scale renewable integration in urban planning, as stated by Alghamdi et al., who consider that, in a broader context, the deployment of such PV systems aligns with international development targets, notably the Sustainable Development Goals [11]^[7]. By harnessing the power of the sun in urban environments, cities can move closer to becoming more “inclusive, safe, resilient, and sustainable”, which is in line with the goals set for 2030 [12]^[8]. A different and innovative approach is presented by Fakour et al., which can be considered as an upgraded follow-up of the traditional use of carport systems, at a time when electric vehicles (EVs) are being heralded as the future of sustainable transportation, and given the pressing need to decarbonize the cities [13]^[9]. The researchers assume that the integration of renewable energy sources into EV infrastructure is crucial and discuss the feasibility of a solar carport canopy for EV charging in Kaohsiung City, Taiwan. In this way, the repurposing of open parking lots into solar farms with PV canopies emerges as a promising solution, be it located in a common car parking lot in any city or specifically located on a university campus. These installations allow the harnessing of renewable energy without compromising the utility of parking spaces. Open parking lots are easily accessible in urban areas and have the added benefit of providing shade for vehicles, reducing the need for air conditioning and, subsequently, the power consumption of EVs. Several studies, like those by Nunes et al. [14]^[10] and Malek et al. [15]^[11], have highlighted the potential benefits of such setups, from environmental to financial gains. However, as stated by the researchers, the existing literature has largely ignored the broader implications of such integrations, especially considering various driving habits, EV brands, and the public benefits of connecting these structures to popular sites, as is the case of a university campus, and concluded that solar carports offer a sustainable solution to the pressing need for renewable energy integration into EV infrastructure, contributing to efficiently charge EV models, reduce CO₂ emissions by a staggering 94% compared to traditional grid methods, and offer potential financial benefits to vehicle owners, especially if carbon pricing is introduced. Despite the approach being traditional, it is possible to find a few more studies reporting the results of such systems. For example, Zomer et al. presented the results from the evaluation of the Fotovoltaica/UFSC solar energy laboratory in Florianópolis, Brazil, which occurred from August 2017 to February 2020 for its energy balance and performance of its photovoltaic (PV) systems [16]^[12]. Designed as a zero-energy building (ZEB), the lab had PV systems on rooftops and façades, striking a balance between aesthetics and energy output. Additional PV installations included a carport, an electric bus (eBus) shelter and charging station, and ground-mounted systems. Over the review period, the lab conducted monthly analyses on factors like solar irradiation availability, occupancy changes, PV system capacity, and energy generation versus consumption. Despite some downtimes in PV systems due to research activities, the lab’s PV generation (111 kWp) could fulfill 148% of the building’s energy requirements and 97% of the building combined with eBus needs. Optimally, the lab could have produced 38% extra energy, translating to 134% of the combined energy consumption. Hence, the lab transcends its ZEB design, emerging as a positive-energy building (PEB). This study underscores the potential of building integrated photovoltaics (BIPV) in achieving energy-positive structures. Another study, by Horan et al., presents a novel method for quantitatively estimating the potential of decarbonization technologies in Higher Education Campuses (HECs) [17]^[13]. Recognizing a gap in standardized preliminary estimations, the researchers introduce a method focused on building integrated photovoltaics, micro-wind turbines, rainwater harvesting, and ground-mounted PV on HECs. Utilizing Google Earth imagery and online HEC maps, two primary variables were identified to gauge the deployment potential: roof area and open parking area. The method’s practical application was showcased in Ireland’s higher education sector, revealing the significant potential for decarbonization technology deployment. An essential insight from the study is the adaptability of this approach: while tailored for HECs, the building decarbonization aspect can be applied to commercial and industrial sectors, given their similar building footprints. Additionally, the open park component is versatile enough for city-scale analysis, owing to the consistency in open park designs globally. This adaptability underscores the method’s broader implications, providing valuable insights for city-wide transitions toward decarbonization. Regardless of the varied approaches taken by the multiple researchers studied, there is a unanimous consensus regarding the sustainable potential of carport photovoltaic (PV) systems. Every piece of the literature analyzed, whether focusing on design specifics, integration techniques, or impact assessments, invariably points to the ecological and operational efficiency of PV carport solutions. These systems not only optimize the use of available open spaces but also contribute significantly to reducing carbon footprints, especially in urban environments. Moreover, as global energy demands surge and the urgency for renewable energy sources becomes paramount, the role of such innovative solutions is emphasized even more. The adaptability of PV carports, as highlighted in many studies, makes them suitable for diverse settings, from educational campuses to commercial establishments, and even city-wide applications [18]^[14]. Their dual functionality, providing shade and generating power, adds another layer of appeal to their deployment. In the broader context of sustainable urban development and the push for decarbonization, PV carports emerge as a practical, efficient, and environmentally friendly solution. The overwhelming evidence from various researchers suggests that PV carport systems are not just a fleeting trend but a sustainable option that warrants serious consideration in the collective pursuit of a greener future [19,20,21]^[15][16][17].