Passive solar energy: what it is, how it works and how to make the most of it

Spanish households have increased energy consumption by 28% after the 2020 pandemic of covid-19, accounting for 70% of total consumption.This is not only reflected in the time we were locked in, but because of this, there were changes in our habits with the introduction of teleworking. This meant more hours spent at home, so it is not surprising that consumption soared in many households.

But how can we solve this problem? The use of renewable energies, specifically solar energy, provides us with economic savings of up to 50-60% on our electricity bill.

However, when we talk about this energy source, we must differentiate between two types: active and passive.

Passive solar energy still has a wide field of development, but this new technology can cover a third of the heating needs in our house.

For this reason, in the following article we will take a closer look:

It uses the direct energy from the sun without the need to transform it through a photovoltaic system, as is the case with active solar energy.So how is electricity generated for domestic consumption? By means of the construction elements of a house, i.e. walls and windows that allow direct use of the energy produced by the sun.

These types of buildings are designed to fulfil the following main functions:

The concept of passive solar design was born in the 1990s in Germany. Passive houses take into account the climate of the geographical area in order to optimise the available resources. In this way, the energy demand of the building is reduced and the interior of the house is kept at a comfortable temperature.The temperature and solar radiation of the territory will also influence energy production.

What is the main benefit of passive houses? The possibility of reducing energy costs by 90% compared to a traditional house.

These designs are not only feasible for the construction of new buildings, it is also possible to renovate existing houses and apply this new technology, although the cost will be higher.

The first key difference between passive and active solar energy lies in the energy transformation.On the one hand, active energy requires an installation of solar panels to capture the sun’s rays and convert them into electricity suitable for domestic consumption, i.e. the photovoltaic system installed on our roofs transforms the direct current generated into alternating current for consumption.

On the other hand, what is the advantage of passive houses? The ability to use the sun’s energy directly without the need for installations. This is due to the architecture of the buildings with elements that allow the solar energy to be harnessed through this operation.

Therefore, a specific design is needed to be able to enjoy passive solar energy. Active energy, however, does not require a specific building, but other factors play a role in the installation.

In addition, the collection of a passive solar design is done through the building components, i.e. windows, roofs or walls. Active energy, on the other hand, uses the solar panels to generate that energy.

What you should be clear about is that both options are renewable, clean and inexhaustible energies.

A house can be considered a passive house if it meets a number of requirements:

A passive house must have a certain amount of window glazing in order to receive sunlight through the glass, whose task is to train radiation.Consequently, glazing is a key factor for enjoying energy in the home. Moreover, beware of using excessive glazing that can lead to energy losses.

Similarly, you should consider the dimensions of the windows, choosing the right size for your consumption.

Technological development is on the rise and thanks to advances in window components, insulation has been improved to conserve heat in the right rooms and avoid energy losses.

As with photovoltaic systems, the location has the same influence on passive houses. What is the best choice? A south-facing orientation with an inclination of 30°. In this way, no heat is lost in winter and not too much heat is retained in summer, thus achieving an optimum temperature in every season.

But be careful, this balance is sustainable as long as the location is correct and the right type of glazing is used.

Thermal mass is produced thanks to the heat absorbed by the different construction elements: walls, ceilings or floors. This energy is then stored for use in the home.But what happens in summer? The heat gain is reduced by the installed overhangs or by the blinds themselves to keep the house cool when high temperatures threaten us.

For this type of architecture, materials such as brick or stone are used, capable of storing energy for heat conservation and use. To be more explicit, they allow the maximum energy to be captured and release the heat generated in a progressive way, reaching the right temperature.

This will lead to a decrease in energy costs. But of course, the use of thermal mass must be done correctly in order to achieve energy efficiency and not reduce the comfort in the house one iota.

On the other hand, using materials such as wood will lead to a reduction in thermal mass. The result? Less available electricity.

Do not forget good external ventilation to prevent heat from accumulating in a particular room of the house, but to dissipate it inside the house. Otherwise, the solar radiation generated is stored directly below.

Poor insulation of the house can lead to losses of 30% in the coldest seasons.In short, part of the energy produced through our structure is being lost.

For this reason, it is important to emphasise superior insulation in geographic areas with adverse climates and to avoid heat leakage that loses the right temperature in the home.

In summer, however, a passive solar design allows to keep the environment cool with adequate comfort at the given temperatures.

And where should this insulation take place? In all building elements. We are not only talking about walls, but also windows and roofs.

If we want to avoid these losses, the best alternative is to add more insulation material on the roof, where more temperature control is needed.

Shading also affects the solar radiation received in a passive house.Let’s see how they can benefit us in the different seasons of the year. In summer, they reduce the perceived light, keeping the house cooler against excessive temperatures. In winter, on the other hand, they prevent overheating.

But be careful if the geographical area is constantly shaded and the windows do not generate the correct amount of energy for our daily consumption, causing significant losses.

For this reason, the orientation of the house plays an important role in receiving the right amount of solar energy and not producing losses in radiation and an excess that reduces the efficiency of our home.

A passive solar design has different functions that allow you to enjoy solar energy in your home: lighting, heating and hot water.The differential and particular feature of this technology is to avoid the inclusion of a photovoltaic system on the roofs to enjoy that energy at that very moment.

But we must emphasise how it works depending on the territory. It is not the same to talk about a region with a climate with mild temperatures, as it is to talk about locations with extreme winters where passive solar energy is not enough to cover the energy consumption of the house. In these cases, it acts as a complementary energy source to active energy.

In the following list, you can see several examples that show how to take advantage of a passive solar house:

Passive designs have great benefits, here are some of them:

It is a technology that is in full development and still needs significant capital to install it in our homes, especially if it is not a newly built house where it will be necessary to tear down windows and walls to install the appropriate elements.At present, both active and passiveenergy coexist, but the potential of passive houses will bring us numerous benefits, where energy savings could reach 90% and the monthly bill would be considerably reduced.

Opting for a passive solar house is an important decision that requires a significant investment.But the beauty of these designs is that they do not require external systems to harness solar energy.

Nowadays, the improvements are being very noticeable, but it still remains as a complementary energy source to the active one, obtaining greater economic savings and increasing the capacity of our home to produce more energy and supply us throughout the year, without having to resort to the conventional electricity grid.

The best initiative would be to build houses with these special materials that allow us to achieve greater self-consumption while at the same time being environmentally friendly.