Four years ago, a viral campaign replaced the tarmac on the world's roads with solar panels, sending the world a commitment to fight climate change and kick-start the economy.
This bold idea has gone through some road testing since then.
The first result of the recent preliminary study came out, and they were a little boring.
Solar panels located under roads have many disadvantages.
Since it is not at the best tilt angle, it produces less power and is easier to color, which is a problem because only shadows on the surface of the panel can reduce the power generation by 50.
Panels may also be covered with dirt, and dustand needs much thicker glass than conventional panels to withstand traffic weight, which will further limit the light they absorb.
As it is not possible to benefit from the air cycle, these panels will inevitably heat more than the roof solar panels.
At the optimum temperature, a loss of 0 per 1 degree Celsiusover.
Energy efficiency is 5%.
Therefore, the performance of the solar road has dropped significantly compared to the roof solar panels, which must be expected.
The question is what is the economic cost?
Road test results are one of the first solar roads installed in the Tourau-Perchein, France.
It has a maximum power output of 420 KW square meters, covers an area of 800 m² square meters and costs 5 euros (£4. 5m)to install.
This means that the cost per installation kW is 11, 905 euros.
Although the road should produce 800 KW hours a day (kWh/day)
Some recently released data show that the yield is close to 409 KW hours/day, that is, 150,000 KW hours/year.
Wondering how much this is, British families use about 10 KW hours a day on average.
The capacity factor of the road-measuring the efficiency of the technology by dividing the average power output by the potential maximum power output-is only 4%.
In contrast, the Cestas solar plant near Bordeaux has a row of solar panels carefully tilted towards the sun with a maximum power output of 300,000 KW and a capacity factor.
Its cost is 360 euros, that is, 1,200 euros per installation, which is 1 out of 10 of our solar road cost, and it generates three times the original electricity.
In the United States, a company called "solar roads" has developed a smart highway with solar panels, including sensors and LED lights, to show any imminent dangers such as deer traffic warnings
It also has heating pads to melt snow in winter.
Several of its SR3 panels have been installed on a small portion of the road surface in Sandpoint, Idaho. This is 13.
Area of 9 m² square meters, installed capacity 1. 529 KW.
Installation costs $48,734 (about £37,482)
This means that the cost per installation of kW is 27,500 euros, more than 20 times higher than the Cestas power plant.
Solar Roadway's own estimate is that the LED light will consume 106 MW per lane mile, and because the panel generates 415 MW, the LEDs consume more than useful power.
This will further reduce performance.
The heating plate is also quoted as Figure 2.
Miles 28 MW per lane, so running for only six days will offset any net income from solar panels.
This is before we look at the data for the Sandpoint installation that generated 52.
At 397 KW hours in 6 months, that is, 104.
8 KW a year.
From this, we can estimate that the capacity factor is only 0.
782, 20 times less efficient than Cestas power plant.
Nevertheless, it should be noted that the group is on a city square.
If there is one thing we can conclude that in the snowy northern town, a section of the sidewalk surrounded by buildings is not the best place to find solar installations.
However, it may not be a good idea to have a larger solar road on the city streets.
The road is no longer as large as we think.
The Department of Transport has broken down the length of different road types in the UK.
Assuming we can cover these with solar panels, there are four lanes for each highway, two lanes for roads A and B, and half of the lanes for the C andU Road (
A lot is a one way street, just not suitable)
We came up with a surface area of 2 million square meters.
Before you realize that buildings in urban areas take up the area of 17, it sounds like it is. 6 billion m².
Therefore, just using solar panels to cover a small part of the UK's roof will immediately generate more power than putting them on the road.
This is very different from the benefits that higher locations will bring to larger power generation.
All of this suggests that it is appropriate to have only a small portion of the road network.
Moreover, given the relatively small size of the road network, solar roads can only become a niche energy source and will never be a shortcut to our energy supply in the future.
Dylan Ryan is a lecturer in mechanical and energy engineering at Napier University in Edinburgh.
This article first appears in The Conversation (Dialogue. com)