Solar Design Series – Summary of Passive Solar Design Principles

Solar Design Series - Summary of Passive Solar Design Principles

1 Overview

The independent power supply system is designed to meet the customer’s electrical energy needs. Therefore, it is particularly important to reduce the demand for this electrical energy as much as possible.

In general, the largest energy demand for a typical IPS customer is the heating and cooling of their residences. If the house is new, the house should be designed and built in conjunction with the solar design function, either passively or actively. The electrical needs of the home should be assessed when designing, and alternative energy sources (such as LPG for cooking) and energy-efficient appliances should be used wherever possible. The smaller the total amount of electricity a house uses every day, the smaller and less expensive an independent power supply system is required.

  1. Overview of passive solar design principles

The general principle of passive solar design is to use the sun to heat the house in winter and shade to protect it from overheating in summer.

2.1 Orientation
Except in the tropics, Australia’s sun is in the north. The orientation of the house and the location of the rooms in the house should be combined with the actual situation: the heat gained from the sun will mainly come from the north. For the positioning of the house, it is best to arrange the living area used during the day on the north side of the house. The south side of the house is generally cooler than the north side, so sleeping areas are best placed on this side of the house. The east wall, especially the west wall, is generally hotter.
Figure 1 shows the basic orientation principle of a house.

Figure 1 - The basic orientation principle of the house
Figure 1 – The basic orientation principle of the house

2.2 Thermal mass
Thermal mass is a term used to describe building materials that absorb the heat generated by the sun during the day and then release that heat at night. Thermal mass includes standard parts of the house, such as concrete floors and masonry walls, but some small parts (such as small concrete structures in front of windows) can also be incorporated into the house to absorb this heat.

2.3 Insulation
Heat can be gained from outside through walls and roofs in summer, while in winter heat is lost from inside. Insulation located on roofs and walls reduces this heat gain and loss. Insulation is given an R-value to indicate its effectiveness. The higher the R value, the greater its resistance to the flow of heat.

2.4 Windows
Glass windows are where the most heat is transferred between the exterior and interior of a house. In winter, glass is expected to absorb the heat during the day, but at night a double glazing or heavy curtains are required to prevent nighttime heat loss; in summer, double glazing will not reduce heat gain, while curtains can. Therefore, the ratio of windows to the house can affect the house overheating or underheating.

2.5 Sun Control
The sun is high in summer and low in winter. Therefore, the ideal design is to allow sunlight through the windows in winter and vice versa in summer. This can be achieved through the use of eaves or shading devices, as shown in Figure 2.

Figure 2 - North window shade in summer
Figure 2 – North window shade in summer

2.6 Ventilation equipment
On hot summer days, especially at night when the air is relatively cooler during the day, convection ventilation is required to move air throughout the house. Such equipment should be incorporated into the house so that convective circulation does not occur during the winter months.

2.7 Tree placement
If possible, trees and plants should be planted with the following benefits:
(1) During the summer months, the north side of the building can be shaded, but in winter, the sun cannot be blocked.
(2) In winter, it acts as a windbreak against colder southerly winds.

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