Passive Solar Buildings – Concept, Benefits and Performance
Neenu S K
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Passive solar buildings uses solar energy for its energy needs in different seasons. The Concept of passive solar buildings, performance and benefits are discussed.
The rate of increasing population growth with increasing innovations in the field of industries and technologies have all together resulted in the increasing energy consumption enormously. This high consumption is a concern for sustainability. This has a negative impact on the environment and energy conservation.
So, an innovation in building construction, that would perform with the existing energy, without exploiting any additional mechanical or electrical sources is called as passive solar building design concept. These buildings take the advantage of the climate, where it must be constructed. A proper site analysis would judge the performance of the building.
The concept of passive solar buildings is adopted in new buildings. But already existing buildings can be retrofitted to behave passively. The building is named passive solar buildings because we don't make use of any mechanical or electrical devices within the building to bring the concept.
The main concept of passive solar buildings is that its building elements i.e. the windows, walls and the floors are made able to collect solar energy and store them. This energy is then used in the winter for warmth and used to reject the heat during the summer seasons.
The buildings convert the solar energy into useful energy without the help of any other mechanical system.
The passive solar buildings work based on the following principles:
The first principle is based on the route of the sun in different seasons. The sun in winter will be traveling in a lower route compared to summer.
In winter, the south direction faced glass will help in energy absorption and storage in the building.
The location of thermal mass in a position enabling easy absorption of solar energy later would help in the easy release of the same during evening time.
The direct sun can be resisted by overhanging elements as shown in the figure below. These are also called control elements.
Elements Considered for Passive Solar Building Construction
The main elements considered are:
Room types, internal doors, walls and furniture in buildings and their placement.
The Equator faced orientation for the building
Building dimension extension in east-west direction
Window size fixed to get adequate solar in winter and shade in summer.
Windows in the west are avoided.
Use of thermal mass like floors or walls
Fig. Passive Solar Building Elements
Performance of Passive Solar Building
The efficiency of passive solar buildings depends upon the following factors:
The site climatic conditions
The passive solar building system adopted
The passive solar building design criteria
The building size
It is found out from the studies that when the passive system and the concept of energy conservation come together appropriately to sink with the climate, the net benefit is tremendous. The net benefit is defined in terms of backup heat reduction compared to a conventional building system.
Results from Monitored Buildings
A set of passive solar buildings were monitored for one or more years by using twenty or more sensors that record hourly. The results from the computer analysis of data give us the following results:
When compared to conventional home auxiliary heat usage, the passive solar building uses 70% less. On average the solar savings are in the range of 27% of the total heating load value.
There was a tremendous decrease in the demand of electricity when compared with the conventional building arrangement.
The cost of construction of passive solar buildings was found higher compared to that of the conventional method. This is because of time and cost used for proper optimization of energy. When compared with the final output the passive solar buildings provide, the system is economical.
Benefits of Passive Solar Buildings
The benefits of passive solar building systems are as follows:
The building interior are bright - The interior of the building would be filled with sufficient light. This is due to the transmission of visible light frequencies. The system is designed such a way that the control of glare and over lighting is kept in mind.
The ultraviolet energy is blocked - The direct ultraviolet rays are harmful. The passive solar building system has the advantage of blocking almost 99.9% of the ultraviolet radiation energy. Preventing this would save the interior fabrics as well as decor and make them long lasting.
Summer is Made cooler and comfortable - It keeps the interior cool during the hot season. This would obviously reduce cooling energy costs. This would give a low solar gain coefficient value (SHGC).
Winter made warmer
Problems Faced by Passive Solar Buildings
The passive solar building system is an innovation which is still in its developing stage. It presently faces two main concern that would result in other problems. The main two problems are discussed here:
Overheating
The result of improper design causes overheating by the sun. This can occur either in summer or in winters. If the glazing provided in the south is oversized or insufficient or insufficient thermal storage mass for direct gain are the reasons of overheating in winters.
A storage size that would limit the temperature within the building to 220C must be adopted.
When the facing of energy gain is more towards east or west, there are chances of overheating in summer seasons. This is a common issue found. The best remedy for this is to make use of south facing glasses and avoid glasses with any other orientation.
Skylights and overhead glasses must be covered in summer. Enable natural ventilation to avoid internal overheating during summers.
Perception
When a new building concept is put forward to the society, the first essential feature everyone should understand is what is the scope of the new concept? The problem of public, or the building industry or any of the designers is the lack of proper perception.
They are not ready to compromise their design and aesthetics for energy conservation. They are more concerned about the looks of their homes and this stops them to built their structure based on the passive solar design concept.
The only solution for this is public education. Studies on passive solar buildings with more architectural and aesthetics ideas must be made. Commercial buildings like schools, libraries have an excellent space of passive solar building design concept.
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