In the last five years, there has been an increasing trend in fitting roads and pathways with solar panels, making these otherwise dead spaces work harder towards a greener future. The latest of these is the world’s first solar panelled road which was opened in December 2016 in Normandy. Costing the French tax payer €5m, the 1km stretch provides clean, free power for street lighting in the local village. However, such projects have been attacked as a poor use of public money begging the question; is investment in solar walkways and roads an efficient means to improving sustainability?
From an engineering and economic perspective, the answer may be no. If every motorway and trunk A road in the UK had one lane fitted with the same panels as described in the introduction they would provide a modest 34 square kilometres of capacity, about half a square meter per person1 of solar power2, which is less than 1% of the UK’s overall renewable generation target for 2020 and does not even meet level 1 on the DECC 2050 pathways. This system would cost an eye-watering £52 billion to install3, over five times more than domestic solar installations. You might have thought that this would buy you the Aston Martin of solar panel arrays but is actually paying for the unnecessary requirement of making the panels robust enough to survive the challenges of being a road, whilst actually placing solar PV panels in a very inefficient configuration.
So what are the alternatives? Which investment options will deliver more green impact per taxpayer pound? The baffling exercise of prioritisation is made easier by energy flow data visualisations such as a Sankey diagram. The Sankey diagram for the UK in 2015 suggests that waste reduction and improved transmission efficiency are the low-hanging fruit…
Prioritise waste reduction
Capturing wasted energy from power stations and industrial processes is a more cost effective approach than adding solar capacity. In the UK over 50% of the energy available from fuel for electricity generation is wasted4 and less than 10% of thermal power stations have an energy recovery system5. Physics will never allow all this energy to be recovered but investment in technologies such as CHP (Combined Heat and Power) and TEG (Thermoelectric Generator) are a cost-effective means improve efficiency, radically reducing fossil fuel demand. Copenhagen is a well cited example of the benefits of this approach; 98% of its domestic heat is provided by otherwise wasted energy recovered by CHP, saving the average household €1,400/year and cutting oil demand by 203,000 tons/year.
Improving the efficiency of Transmission and Distribution (T&D) networks would also yield greater benefits for less effort and cost. In the UK, 8% of electrical power generated is lost between the power station and the plug, a statistic which has not changed for over 25 years. Following the lead of countries such as Germany and the Netherlands by investing in modern transformers and power management technology could cut these losses in half, increasing the UK’s capacity by the equivalent of 2 large coal-fired power stations6.
- Assumes UK population of 67M in 2020
- Assumes 7600 miles and same road width as Normandy installation (2.8m). Calculated using UK mean insolation.
- Assumes same cost/per length as Normandy installation (5 million EUR/km)
- DECC, 2015, Digest of United Kingdom Energy Statistics, Chapters 5 and 7
- Ricardo-AEA, 2013. Projections of CHP capacity and use to 2030. Report for DECC. Cost effective potential based on a discount rate of 15% over 10 years
- Calculated from the capacity of Aberthaw B, 1550MW.