Passive solar energy is a type of solar energy in which no external energy is used. The objective is to take advantage of direct sunlight.
In the design of passive solar buildings the building materials are designed to fulfill two functions:
Collect, store, and distribute solar energy in the form of heat in the winter months.
Reject solar heat in the summer months.
This way of designing is called passive solar design. It does not imply the use of mechanical or electrical devices. It is widely used in living spaces.
The key to designing a passive solar building is to make the most of the local climate by conducting an accurate site analysis. Design techniques can be more easily applied to new buildings. However, existing buildings can be adapted.
Elements to consider include:
The placement and size of the windows.
The type of glazing.
The thermal mass.
Air movement and natural ventilation.
Thermodynamics plays a fundamental role in this regard. Temperature and heat transfer are the basis of this system.
Examples of passive solar energy
The best examples of passive solar energy are found in the architecture prior to electricity:
Thick and insulated walls. They prevent heat output in winter and keep the house cool in summer.
Ceilings with external ventilation. Roofs receive a lot of radiation in the summer. If they have cross ventilation, this heat dissipates. It works like a passive solar cooling system.
Orientation to the sun. South-facing windows are capable of capturing more energy.
Vegetation. Trees and vegetation imply shadows. Shadows reduce the solar radiation that the house receives. In summer it can be beneficial. In winter it can be harmful.
Dark surfaces absorb heat from the sun.
Driving water pipes exposed to the sun, you can get hot water.
What is the difference between active and passive solar energy?
The main difference between active and passive solar energy is that in the active one there is a process of energy transformation. Meanwhile, passive solar energy does not take advantage of any mechanical or electrical device.
Passive solar energy is the technique that allows you to harness solar energy directly without having to process it. For example, depending on the design in the construction of buildings, the amount of natural energy used can be greatly improved.
Techniques for passive solar use
Passive solar energy uses components to control the heat generated by the sun. For example: the construction of walls, floors, ceilings, south-facing glasses, windows, exterior building elements, and landscaping.
Solar heating designs attempt to trap and store heat from direct sunlight. Passive cooling minimizes the effects of solar radiation through shading or the generation of ventilation air convection currents.
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 outside in summer.
A good architectural design also allows us to improve natural lighting. A commercial building can reduce its electricity bill by using natural light. In this way it is achieved:
Create a pleasant environment.
Reduce air conditioning costs.
Reduce the amount of heat generated by light bulbs and artificial lighting sources.
A Trombe wall is a wall built on the winter sun side with a glass external layer and a high heat capacity internal layer separated by a layer of air.
What are the advantages of passive solar energy?
The main benefits of this technique are the following:
Low economic cost. The cost to carry out your work is low. Sometimes this cost is even nil.
The maintenance cost is very low.
The energy efficiency and savings in energy consumption depend on the size of an installation (either renewable energy or a conventional installation).
These criteria are a greater economic benefit if they are criteria that are considered from the beginning.
Passive solar technologies offer significant savings, especially when it comes to space heating. Combined with active solar technologies, such as photovoltaic energy, they can also become an excellent source of income.
Passive solar energy is a technique in which solar energy is used in a natural way. This does not require additional mechanisms or external energy sources.
The technique to achieve this is a good architectural design optimizing the position and dimensions of the different construction elements (walls, windows). Likewise, it is necessary to take into account air currents, the amount of solar radiation received at all times of the year, etc.