Passive solar energy is a type of energy that uses sunlight directly, without resorting to external energy sources. Its main objective is to optimize natural solar resources to regulate the temperature in buildings, reducing the need for mechanical or electrical systems.
In buildings designed with passive solar principles, architectural elements serve two essential functions:
- Collect, store and distribute solar heat in winter , to maintain a comfortable temperature.
- Reject solar heat in summer , preventing overheating and ensuring a cool environment.
This approach, known as passive solar design, is based on a detailed analysis of local climate and site characteristics. While the techniques are easier to apply in new construction, existing buildings can also be retrofitted to incorporate these principles.
Key elements in passive solar design
The success of a passive solar building depends on several factors:
- Location and size of windows: Maximize solar radiation in winter and minimize it in summer.
- Glazing type: Improve insulation and thermal control.
- Thermal insulation: Reduce heat loss or gain through walls, ceilings and floors.
- Thermal mass: Materials that absorb, store and release heat gradually.
- Shading: Use of elements such as eaves, pergolas or vegetation to control sun exposure.
Thermodynamics is the basis of this technique, as it regulates heat transfer and internal temperatures, maximizing the energy efficiency of the building.
4 Examples of passive solar energy
Passive solar energy has been used for centuries in architecture, long before the advent of electricity, taking advantage of simple but effective principles to regulate the temperature of living spaces. These techniques, still in use, stand out for their functionality and sustainability.
1. Thick and insulated walls
Traditional constructions, such as adobe or stone houses, used thick walls that acted as a natural thermal barrier. In winter, these walls stored the sun's heat during the day and slowly released it at night, keeping interiors warm. In summer, the thermal mass of the walls prevented external heat from penetrating quickly, keeping spaces cool. This approach is a clear example of how architecture can regulate the indoor climate without the need for mechanical systems.
2. Roofs with external ventilation
In warm climates, roofs often receive a large amount of solar radiation. Roofs with external ventilation systems, such as pitched roofs with air chambers or strategic vents, allowed the accumulated heat to be dissipated before it reached the interior of the building. This principle is observed in many traditional Mediterranean and tropical buildings, where ventilated roofs ensure more comfortable spaces.
3. Orientation to the sun
Orienting homes to the south (in the northern hemisphere) or north (in the southern hemisphere) is a key passive design technique. This positioning allows for maximising solar heat gain in winter, when the sun is lower on the horizon. In addition, the strategic placement of windows and openings in these facades helps regulate natural light and heat throughout the year, reducing reliance on heating and electricity.
4. Vegetation and natural shadows
The use of trees, climbing plants and pergolas is another classic example of passive solar energy. In summer, vegetation creates shadows that reduce direct solar radiation on the home, lowering interior temperatures. In winter, when deciduous trees lose their leaves, they allow the sun to reach the facades and contribute to natural heating. This balance between shade and sunlight makes vegetation a strategic ally in passive design.
Passive solar architecture
Passive solar architecture is a design approach that harnesses the sun's natural resources to optimize the energy efficiency of buildings, without resorting to mechanical or electrical systems.
This type of architecture focuses on integrating elements such as building orientation, window size and placement, thermal insulation and the use of high thermal mass materials. These components work together to capture and store solar heat in winter and minimise its input in summer, ensuring year-round thermal comfort with low energy consumption.
This design also considers strategic shading through eaves, pergolas or vegetation, which help control seasonal solar radiation. In addition, passive solar architecture promotes sustainability by reducing dependence on external energy sources and minimizing carbon emissions associated with HVAC.
Although it is easier to implement it in new constructions, passive solar principles can be adapted to existing buildings, transforming them into more efficient, comfortable and environmentally friendly spaces.
What is the difference between active and passive solar energy?
Solar energy can be harnessed in two ways:
- Using active solar energy. Photovoltaic solar energy and thermal solar energy.
- Using passive solar energy.
The main difference is that in active solar energy there is a process of energy transformation. Using photovoltaic panels we transform sunlight into electrical energy. On the other hand, using thermal solar panels we transform radiation into heat energy.
Passive solar energy refers to techniques that allow solar energy to be harnessed directly without having to process it. For example, depending on the design of the building construction, the amount of natural energy that is harnessed can be significantly improved.
Techniques for passive solar use
Passive solar uses components to control the heat generated by the sun. Examples include: the construction of walls, floors, roofs, windows, exterior building elements, and landscaping.
Solar heating designs attempt to trap and store thermal energy from direct sunlight. Passive cooling minimizes the effects of solar radiation through shading or the generation of convection currents of ventilation air.
An important aspect of building design is knowing how to manage the flow of air currents inside the building. It is necessary to be able to capture heat in winter and dissipate it to the outside in summer.
- Create a pleasant atmosphere.
- Reduce air conditioning costs.
- Reduce the amount of heat generated by light bulbs and artificial lighting sources.
Advantages and benefits
Passive solar energy offers a number of significant advantages, both economic and environmental, which make it an attractive option for sustainable construction.
Low economic cost
One of the main advantages of passive solar energy is its low initial cost. In many cases, passive design strategies, such as building orientation, choice of materials or use of vegetation, do not require additional investments or can be implemented without significant costs. Even in renovations, the modifications required to optimize solar energy capture are usually minimal, making this option one of the most economical in terms of construction.
Low maintenance and environmentally friendly
Passive solar energy systems require extremely low maintenance, as they do not rely on mechanical or electrical devices that require constant repairs. Furthermore, by not emitting greenhouse gases, this technique does not contribute to climate change, making it an environmentally friendly solution. This energy efficiency, which depends on factors such as the location and proper design of the building, translates into substantial savings in energy consumption.
Energy savings and efficiency
Savings on heating and cooling is one of the most obvious benefits of passive solar. By harnessing the sun’s natural heat and avoiding thermal losses, passively designed buildings require less energy to maintain a comfortable temperature, reducing energy bills in the long run. Additionally, when combined with active solar technologies, such as photovoltaics, passive systems can contribute to generating additional income by transforming the property into a renewable energy source.