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What Is Passive Solar Energy?

We define passive solar energy as a type of solar energy in which no external energy is used. The objective is to take advantage of direct sunlight. This concept is handy in bioclimatic architecture.

What is passive solar energy?

In the design of passive solar buildings, the building materials are designed to fulfill two functions:

  1. Collect, store, and distribute solar energy in the form of heat in the winter months. When sunlight enters the building 

  2. 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 take advantage of the local climate. To do that, we need an accurate site analysis. It is possible to apply design techniques easily to new buildings. However, existing buildings can be adapted.

Elements to consider include:

  • Depending on the placement and size of the windows, we can get heat gain or heat loss.

  • The type of glazing will affect the heat transference.

  • Thermal insulation reduces heating and air conditioning costs.

  • The thermal mass can work as heat storage and reduce the cost-effective of a heating system.

  • Shading.

  • Air movement and natural ventilation will help us to deal with warm air.

Temperature and heat transfer are the basis of this type of energy. The laws of thermodynamics play an essential role in this matter.

Examples of Passive Solar Energy

The best examples of passive solar energy are found in the architecture:

  • 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.

  • It is possible to obtain hot water driving water pipes exposed to the sun.

What Is the Difference Between Active and Passive Solar Energy?

The main difference between active and passive solar energy is that there is a process of energy transformation in the active one. Meanwhile, passive solar energy does not take advantage of any mechanical or electrical device.

Concerning active solar energy, photovoltaic panels, we transform sunlight into electrical power. On the other hand, using thermal solar panels, we convert radiation into heat energy.

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 buildings' construction, we can significantly improve the amount of natural energy used.

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 essential aspect of bioclimatic building design is knowing how to manage air currents inside the building. It is necessary to be able to capture warm air in winter and dissipate it outside in summer.

What is passive solar energy? An excellent bioclimatic architecture design also allows us to improve natural lighting. A commercial building can reduce its electricity bill by using sunlight enters. In this way, the goals we can achieve are:

  1. Create a pleasant environment.

  2. Reduce air conditioning costs using passive solar cooling techniques.

  3. 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 an external glass layer and a high heat capacity internal layer separated by an air layer.

Passive Solar Collection

Within the passive solar collection, we can differentiate different systems according to their behavior, distinguishing between the collector elements and the accumulators.

The collectors, as their name suggests, perform the function of collecting solar radiation. These elements, in turn, can be classified into:

  • Direct: are those in which the solar capture is direct and affects the room or the premises to be heated.

  • Indirect: they are those systems that, through the interposition of construction elements, capture solar energy and store it, transmitting it to the rooms.

The accumulators are responsible for storing energy for later use. Some systems allow to accumulate energy during the day and release it at night, and others are capable of storing heat energy for long periods, days, or even months. 

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, and sometimes this cost is even nil.

  • The maintenance cost is meager.

  • It is friendly to the environment. Passive systems do not emit greenhouse gases. Therefore, it does not contribute to climate change.

  • The energy efficiency and savings in energy consumption depend on the installation's size (either renewable energy or a conventional facility).

These criteria are a more significant 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 income source.

Summary

Passive solar energy is a technique in which solar energy is used naturally. It does not require additional mechanisms or external energy sources.

The technique to achieve this is an excellent architectural design optimizing the different construction elements' position and dimensions (walls, windows). Likewise, it is necessary to consider air currents, the amount of solar radiation received at all times of the year, etc.

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Published: April 9, 2015
Last review: June 2, 2020