Certainly we are not just talking about photovoltaic panels, the solar technologies can be active but also passive: the passive ones are also called 'direct' because they implement a direct exploitation of the radiation without other transformations (they are solar technologies passive for example windows and greenhouses), vice versa active ones are called 'indirect' because they operate a transformation (this is the case of photovoltaic panels).
The solar technologies passive, or direct, are the basis of bioclimatic design, which mainly consists in adapting the building to the natural characteristics of the place to improve indoor climate comfort and to reduce energy consumption. Exactly the opposite of dissipative architecture based exclusively on artificial air conditioning technologies.
The sun gives us natural light and heat, the more we use it, the less we will be forced to consume resources to illuminate and heat the buildings in which we live. This is so obvious that we often forget it, well then repeat it every now and then so as to be aware that the first solar technologies to consider in a project are those that do not require additions or machinery: windows, openings, in short, everything that allows you to take advantage of the solar gains.
Let's not forget that the comfort induced by the techniques of air conditioning and artificial lighting will never equal the gratification and psychophysical well-being that is able to offer true sunlight, physiologically necessary for living beings; it is therefore good to consider also the most immediate and natural part of solar technologies.
However you look at it or consider it, the sun is an immense resource and in both direct and indirect forms, solar energy has a very high degree of technical efficiency. The solar technologies active or indirect today allow the creation of systems for the accumulation of heat useful for heating water and also photovoltaic technologies that allow you to collect solar radiation and transform it into electricity.