Although solar energy has been around for millions of years probably, we only became aware of it recently, to be specific, since government started promoting solar energy use as renewable source of energy in India with solar subsidies. These subsidies save the user upto 50% initial investment cost in the form of payments through central and state government. In the wake of these new subsidies, the market is full of firms manufacturing "Solar Panels", (since most solar cells are actually manufactured in china, there are only a handful of brands that actually have a "made in India" panel) and rife debate about sustainability, energy efficiency and solar energy, and thus this seems an oppertune time to discuss how just putting solar panels on rooftops wont actually drive us through to an energy efficient destination.
There is a plethora of terms in use today specifically for the concept of "reduce, reuse and recycle" in architecture and they all seem to mean the same thing to a lay person. while the first two, namely Sustainable Buildings and Green Buildings, refer to the same concept, the other two are different. Sustainable and Green buildings, as the name might suggest, seek to minimize the negative environmental impact of buildings by efficiency and moderation in the use of materials, energy, and development space and the ecosystem at large. this makes these buildings environmentally responsible and resource efficient throughout the buildings life cycle. It has to be noted here that efficiency and moderation in energy is just a part of a Sustainable/Green building, while an Energy Efficient building is designed to provide a significant reduction of the energy need for heating and cooling (not depending on the equipments used to provide heating or cooling). In the above context, it can be deduced that, strictly going by the definition, a sustainable building has to essentially be energy efficient but an energy efficient building might or might not be sustainable (depending on the materials it uses, and the effect it has on the environment over the period of its Life cycle). The last one, namely the NZEB (Net zero energy Buildings) or in europe, nZEB (nearly Zero Energy Buildings), is an extension of the energy efficient building
genre meaning a building that has a net zero consumption of energyi.e. the amount of energy that is consumed is equal to the amount of energy produced through renewable sources onsite.
Although sustainability is a wide concept and new ways are developed everyday, energy efficiency can be maintained by following a few basic steps, what you use to maintain the steps may be different, but the steps remain the same. These steps are
A study of weather of the site, determination of the climatic parameters that would define the design and form, orientation and daylight optimization of the design based on the weather.
Thermally insulated building envelope including roof and floors.
Designed glaing for solar gains, avoiding thermal bridges hence preventing heat loss. Also taking into consideration condensation risk analysis on internal window panes and envelope during low temperatures.
Shading system design to avoid large solar gains and Glare on days with low sun angle and ventilation both natural and auxillary.
comparing the internal macroclimate with comfort conditions and completing the leftover energy demand with renewable sources.
The photovoltaic panels added on roofs, is usually the last step and maybe replaced with other renewables depending on the part of the globe the site is in. Since India recieves more than 2000 hours/year of sunlight, photovoltaics are the main goto renewable source. Although having renewable energy made onsite does help, in the long run the renewables alone without the concepts of energy efficiency and passive design, create a system which has more wastage and less useful energy.
Also, one main point that manufacturers and sellers dont tell you until you mention it, is the efficiency of the solar panel. Most manufacturers in India guarantee an efficiency of the panel to be more than 80% for the first five years after which the efficiency reduces steadily and some studies suggest that after the 25 years claimed lifespan of the solar panels the efficiency just doesnt remain useful enough. This would mean, a family of five with an average 2000 sq. ft apartment, may use atleast 10 solar panels (assuming a connection of 5kW minimum 10 panels) of standard size in a span of just 20years, and this number would grow exponentially in the next generation when the kids of the family start having a family of their own. In the wake of this argument it almost seems mandatory to reduse the amount solar panels used or atleast use them efficiently enough, so that we may push the government to take active steps to store the solar energy that is transferred in the grid because of reduced usage in urban areas.
Hence, from the above discussion it may be summarized that the push for solar renewables usage is a good thing but has to be combined with other energy efficient strategies to make the most of the environmental energy available. and towards achieving a sustainable built environment, but it definitely is going to be a war about knowledge that can only be won with information.
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