Late last year, we learned about how companies are devising ways to install solar panels on roads. Having said this, is it a far-fetched idea to find more ways to harvest energy from roads?
Before we begin, here are a few facts about roadways, pavements, highways etc.:
- India has the second largest road networks with a road density of 1.66 Kms/Kms2.
- As of 31st March 2015, Indian Roads stretch up to a whopping 54,72,144 Kms .
- Average width of roads is around 6m.
- Most roads are built using Asphalt or Concrete. Both of these materials have a high heat storing capacity.
- Reports of roads warming up to 60° C by storing all the incident heat are not uncommon in India.
Technology has provided us with tools to harvest energy from light, heat, wind, vibrations. Based on these existing technologies, researchers around the world are proposing and identifying approaches for harvesting energy from roads.
Proposed Approaches include:
Harvesting Sunlight incident on Roads
This is one of the easiest approach. The idea is to install or embed photovoltaic cells in the top most surfaces of the roads which would convert the incident sunlight to generate electricity. This electricity could be used to power streetlights, road signs or even feed in the electrical lines of the city.
The technology for this already exists and companies have already started to fashion approach specific PV Cells. One of the most recent application of this approach can be seen in France. Learn More about it here.
Harvesting Solar Heat stored in the Roads
Somewhat complex but practical, this approach involves using the heat stored in the roads either to generate electricity or to warm the water utilities etc.
The Heating Effect
The heat stored in the asphalt or cement made roads can be used to warm the water running through subterranean pipes. This could have multiple applications.
The water could also be channeled into to nearby buildings to satisfy heating or hot water needs, similar to geothermal heat pumps. Though futuristic, this method could even be used to generate steam to turn a turbine in small traditional power plant.
This approach is heavily dependent on superior quality standards and highly efficient thermal components to insulate the pipes to avoid loss of heat energy.
An alternative approach suggests using thermoelectric effect to generate electricity. The electricity produced will be small but usable. The principle states that when two types of semiconductors are connected to form a circuit linking a hot and a cold spot, there is a small amount of electricity generated in the circuit.
Though the current technology is very limiting, the future for this is promising. Along with traditional semiconductors, researches have identified a family of organic polymeric semiconductors which can be fabricated inexpensively as plastic sheets or painted on a flexible plastic sheet.
Harvesting electricity from kinetic energy on the Roads
There has been high volume discussions about using piezoelectric effect to generate electrical energy from busy streets. Though this is the most complex approaches (owing to maintenance and wear and tear ) of all, scientists and researches are placing high hopes on this approach.
It involves placing piezoelectric sensors underneath roads or along the speed breakers which would absorb all the vehicular vibrations to generate electricity.
California is on its way to become the first state to implement such a method and is estimated to generate 44 megawatts of electricity per year for this technology.
Harvesting of energy from roads would pack a lot of advantages. One of the most direct advantage would involve reducing in generation of green house gasses which are a direct byproduct of methods involving fossil fuels. Harvesting of heat would in particular would help in reduce the urban island effect. (An urban island is an urban area which is significantly warmer compared to its surrounding rural areas.)