How to reduce heating expenses using solar energy?

Electrical power supply expenses - one of the main expense items for building maintenance. One of the cheapest and most efficient methods to make the building operation even cheaper is the use of Solar Architecture concept when designing and building. Solar Architecture or passive heating means accumulation of solar energy in the elements of the building (walls, floors,etc.) and its further distribution within the premises. Solar Architecture principles and passive structures that reduce heating expenses by 30-60% are applied already today for the most newly constructed objects in the UK, Germany, Switzerland, Finland, the USA and other countries.

So, let's consider it in detail. There are three methods for arranging passive heating: direct solar heating, indirect heating and isolated heating. 

What is direct solar heating?

Buildings with big windows through which the winter sun gets into the working space have a huge energy potential. Incoming solar energy serves to satisfy the current heating needs of the building or is accumulated to satisfy the heating needs arisen later (during the night).

In the building with the passive heating system, the light comes directly through the glass. Incoming heat normally warms up the inner surfaces of the building, such as concrete floor or masonry (they are usually dark or black), some part of the heat from the surfaces goes back in the room while the rest is accumulated and continues warming up the room during the night period (Figure 1a,b).

In addition, the heat accumulation surface must have sufficient heat capacity for the accumulation and subsequent release of thermal energy. It should be noted that the area of the heat accumulation surface is more significant than its thickness while maintaining the volume.

When implementing passive solar heating, the southern windows of the building must have heat transfer resistance not lower than the required one (from 1 m^{2 0}С / W) without an IR reflective coating. The area of the windows should not exceed 20% of the room area. In cases when the glass area exceeds 20%, it's better to use a combination with indirect solar heating system «Trombe walls».

What is indirect solar heating system «Trombe walls»?

In this passive system, a heat accumulation wall is located directly in the room behind the glass, the wall is covered with a specific solar radiation absorbent material or painted in black. During the whole day, solar radiation warms up the wall, where a Trombe wall is quite thick (about 30 cm) and the warming time is big, therefore, a heating flow reaches the inner surface of the wall located directly in the room only in the evening. If the wall is rather massive, it functions as a heater during the whole night. This solution is a perfect option, when there is no need for daylight in the room, but there is a need for thermal energy. As lighting is almost always necessary, a Trombe wall is normally applied in the combination with a direct solar heating system. In case of such a solution, the room is warmed up during the day due to the direct solar heating, and a Trombe wall accumulates the heat which warms up the room during the night.

A Trombe wall may be used both for the whole size of the window with the design of the sunlight openings and as a parapet or side (near the window) wall. Good design using a Trombe wall is shown where the room is heated and illuminated by direct sunlight during the first half of the day (after the wall became cold in the night), the heat gets in the room from the Trombe wall in the evening, at the same time the daylight is present during the whole day.

A curtain may be installed in the space between the window and the Trombe wall, which will prevent from radiant energy loss through the windows in the night. Nowadays this system may operate in an automatic mode (open during the day, closed - at night), reducing radiant heat losses from the wall to the street by 3 times.

In summer, it is necessary to shadow the wall to prevent heat accumulation, covers, canopies and other systems are used for this.

What is isolated solar heating system «Sun Space»?

Sun spaces are one of the most popular passive systems not due to its efficiency, but because of its convenience. Heat is accumulated in an isolated room with big windows (sunny room) which warms up the adjacent premises in the night.

This system is applied when additional residential sun space is needed which would sooner serve to comfort than functional necessity. 

Solar Architecture concept is widely used when building "passive houses", the heating need of which is covered with solar radiant energy. Experience of such system application proves that introduction of Solar Architecture concept reduces the building heating expenses by 30-60% when taking relatively low capital expenses.