Researchers in Spain have calculated the potential self-sufficiency of rooftop solar energy in eight districts of Madrid, Spain. They found that single-family homes can achieve a self-sufficiency rate of more than 70%, while urban areas with high-rise buildings can reach 30%.
A group of researchers from the Polytechnic University of Madrid and the Center for Energy, Environment and Technological Research (CIEMAT) have analyzed the potential self-sufficiency of solar photovoltaics on residential buildings in eight neighborhoods of Madrid.
The neighborhoods were chosen to determine the impact of urban and building features on meeting electricity consumption through rooftop photovoltaic systems. The results of the study are included in the article Potential for district-level photovoltaic self-sufficiency in Madrid. A scalable methodologypublished in Energy and Buildings.
To calculate the self-sufficiency potential, defined as the ratio of photovoltaic electricity generated to total electricity consumption, the annual electricity production and consumption was assessed for each residential building. The electricity generation assessment was carried out using solar cadastres generated through the Solar Energy on Building Envelopes model in QGIS (Quantum Geographic Information System), LiDAR data (light detection and location) and TMY data (typical meteorological year) for each neighborhood .
In addition, assumptions have been made about the main characteristics of the solar systems to ensure the representativeness of the photovoltaic sector. Electricity consumption was estimated by analyzing the consumption values defined by the Institute for Diversification and Energy Saving (IDAE), in addition to the values appearing in a Eurostat report entitled Consumptions of the Residential Sector in Spain, and some of the formulas used in the research article How to achieve positive energy districts for sustainable cities: a proposed calculation methodologypublished in 2021 in Sustainability.
The consumption figures were obtained by calculating the electricity consumption for lighting and household appliances in a typical home of 100 m2, excluding consumption for heating, cooling and hot water. The specific lighting requirement of a typical home is stated at 5 kWh/m2, while the average equipment in a home is specified as a refrigerator, two televisions, a washing machine, a dishwasher and a computer.
Together, these devices provide a consumption of 2,137 kWh per 100 m2 of home, which corresponds to 21.40 kWh/m2. The sum of these two figures to the average consumption per square meter gives a value of 26.40 kWh/m2. However, the study does not take into account electricity consumption for cooling, heating or mobility. The increasing use of heat pumps and electric air conditioning, along with the electrification of transport, will result in higher electricity consumption in households, which will reduce the potential for self-sufficiency, the researchers said.
The results of the analysis indicate that in areas consisting of single-family homes or low-rise buildings the self-sufficiency potential is greater than 70%. In contrast, urban areas with high-rise buildings have a self-sufficiency value of about 30%. This lower value can be attributed to the significant height of the buildings, which translates into greater energy consumption within the homes and an area available for photovoltaic installation that is insufficient to cover the energy needs of all residents.
In historic centers a greater spread of self-sufficiency potential is observed, with values ranging from 10% to 90%. This variability is attributed to the lower uniformity of the urban fabric, which requires a more detailed analysis at the building scale. “In urban centers, which are often protected by protective legislation due to their historical significance, BIPV systems are a crucial tool to harmonize distributed PV generation with the preservation of the architectural and historical essence of the built environment,” the authors add to.
They also emphasized that the analyzes were carried out by comparing annual production and consumption. While this approach is valuable for estimating the total PV energy generation potential, it cannot reproduce the real-time behavior of grid-connected PV systems, where the balance between generation and consumption is instantaneous. Typical energy consumption profiles of residential buildings result in self-consumption of 20-40% in PV systems without storage.
To carry out a more comprehensive analysis it would be necessary to have access to the daily generation and consumption curves of each building with an hourly resolution, or even better, a resolution of a few seconds, which would allow to determine the size of the installations are optimized to increase the capacity of the installations. self-consumption, the research group concluded.
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