It is widely considered that our current generation is the last one that is capable of preventing irreparable damage from climate change, and at our current rate, it won’t be enough. The factors that cause climate change are multifaceted and complex, but one thing that is obvious is the impact that the built environment can have. This includes choice of material, construction techniques, and energy consumption methods. Renewable energy is becoming more common but still not used enough, with solar energy being one example of this; in the UK, less than 5% of energy from the national grid is from solar power.
There are many ways in which we can use solar power to our advantage in the urban environment and using it as an energy source reduces the need for energy from fossil fuels.
Use of solar panels
One of the most common methods of harvesting the sun’s energy is through solar panels. Photovoltaic panels can be installed on the roof or walls of a building and convert sunlight directly into electricity.
The initial set-up costs are fairly high, and the energy output is variable due to changing weather conditions. However, once up and running they have minimal running costs and all energy harvested from the panels is free and clean, and any excess energy can be sold back to the grid. As they are independent from the grid, they safeguard against power outages and price hikes.
Passive solar heating
Another way in which we can utilize the sun’s energy is through passive solar design.
Orientation of a building can impact the amount of solar exposure it receives. For a building in the northern hemisphere, placing the long axis along an east-west orientation ensures that it receives maximum daylight. Through considering the size and placement of windows, and combining this with building orientation, natural light can be used instead of artificial light, saving energy.
This strategy can also be used for passive solar heating, using the sun’s energy to heat the building.
Using materials that have a high thermal mass can reduce the energy needed to heat and cool a building. Concrete, for instance, has a high thermal mass, so when exposed to solar heat during the day, absorbs some of that heat helping to reduce the cooling requirements of the building. When the temperature drops at night, the stored heat is emitted, warming the building and again reducing energy consumption.
Solar shading
Designing a building to benefit from passive solar heating, if not properly considered, can lead to problems like glare and overheating. To minimise these risks, but to also benefit from sunlight for the previous stated reasons, various solar shading techniques can be employed.
- Louvres (Brise soleil)- External shading devices can be used to block sunlight. Horizontal or vertical slats are placed above or to the sides of windows, placed at angles with gaps between. This allows for light still to penetrate the interior but can block some of it helping to prevent glare and overheating. This can allow for blocking of high angle summer sun to prevent excessive heat, but still allow for low angle sun, i.e., winter sunlight.
- Roof overhang- Similar to louvres, overhangs in the roof design help to block solar irradiance into a building, physically blocking sunlight from hitting the window or façade.
- Green roofs– green roofs have many benefits, including increasing biodiversity, reducing stormwater runoff, reducing noise, and providing good insulation. In terms of solar shading, they also provide a service through evapotranspiration, a process that removes heat from the surrounding air.
- Internal shading devices- Inside the building blinds or screens can be used to help prevent glare. Window tint can also help to stop some of the solar radiation, allowing for daylight without the risk of overheating.
Stack Ventilation
Stack ventilation, sometimes referred to as chimney ventilation, can use the heat generated from the sun to provide natural ventilation. At the top of the building, some form of outlet will be fitted, either a window, vent, or opening in the roof. At the bottom of the building, there will be an inlet for fresh air. Hot air rises, due to it being less dense than cooler air so as a building warms up, either due to sunlight or from usage, the warm air goes up and out of the outlet which has the effect of drawing the cooler air through the building.
This method provides a flow of fresh, cool air through the building, and doesn’t require any energy usage.
As cities continue to urbanize, solar architecture plays a vital role in creating self-sustaining, energy-efficient structures. There are countless ways in which designers can harness solar power and reduce the need for non-renewable energy, and with modern technology always advancing it is possible to have buildings run purely from renewable energy. But this future is still far off, and at present, we will fall short. Sustainable design has never been more pertinent.
Images:
- Duco. Brise-Soleil Horizontal, www.duco.eu/fr/brise-soleil-horizontal/.
- Paul Mcredie. Solar Shading- Overhang , 2030palette.org/solar-shading/.
- Brown, and Dekay. Sun, Wind & Light : Architectural Design Strategies. New York Etc., Wiley, 2001.
