James Clerk Maxwell:
his contribution to Scotland’s all-renewable electricity target
Keith Barnham, Emeritus Professor of Physics/
Distinguished Research Fellow, Imperial College London
Around 30 participants attended the lecture, held at Old College, University of Edinburgh.
Maxwell's discoveries and laws
Keith started off by pointing out that solar photovoltaic (PV) is the only form of electricity generation that does not involve any moving parts. Unlike all other forms of electricity generation, which transform mechanical energy (turning of turbines) into electricity, solar PV produces electricity instantaneously i.e. the moment sunlight (photon) hits a PV cell. This shows the importance of James Clerk Maxwell’s discovery of solar energy as an electromagnetic wave in 1865, touted as the most significant event in 19th century by physics Noble laureate Richard Feynman.
Keith then proceeded to explain electric field and magnetic field and their respective equations (Gauss laws, now also known as Maxwell’s 1st and 2nd equations). Then came Maxwell’s 3rd equation, also known as Faraday’s law, saying that change in time of magnetic field through a loop generates electric field round the loop. This is the equation that explains all forms of electricity generation but one – photovoltaics. Finally, Ampere’s law, expressed as electric current in wire produces a magnetic field loop (Maxwell’s 4th equation). However, Maxwell observed that electric current does not turn off immediately when a switch is thrown, but takes time to fall to zero. (You have probably noticed this in the LED on your flat screen TV or laptop charger). Perhaps something was missing from Ampere’s law? To account for this extra factor, Maxwell amended Ampere’s law and made it anti-symmetric with Faraday’s law, stating that change in time of electric current in wire produces a magnetic field loop (Maxwell’s new 4th equation).
Combining this new 4th equation and Faraday’s law, Maxwell arrived at a single wave equation. The speed of this new type of wave was a very large number, very close to a number he knew very well. It was an important number in a very different branch of physics. The new wave had speed = 3 x 10^8 m/s.
It was the speed of light! Maxwell had discovered that light is actually an electromagnetic wave. Unlike other major theoretical discoveries in physics, Maxwell didn’t need to wait for an experiment to confirm his prediction. It couldn’t be a coincidence that the speed of his electro-magnetic wave was the same as this very large number.
This resulted in huge changes in physics :
1. Optics, the study of light, had suddenly become the study of electromagnetic waves.
2. By uniting electricity and magnetism into a new force electromagnetism, Maxwell had reduced the
number of fundamental forces then required to explain Nature:
- Previously 3 fundamental forces in physics: gravity, electricity, magnetism
- Now two fundamental forces: gravity, electromagnetism
3. He had unleashed a technology that ultimately gave us most of our modern devices, from giant particle accelerators down to mobile phone devices, and hopefully ultimately to non-burning energy security.(Reference: The Burning Answer, Keith Barnham 2015, Weidenfeld and Nicolson)
Maxwell’s law remains unchanged since 1865 – over 154 years until today – despite numerous physics revolutions and other unifications of fundamental forces.
Getting It From The Sun (GIFTS) – modeling using Excel
In the second half of the lecture, Keith explained how solar electricity could help UK and Scotland achieve 100% renewable electricity supply, specifically Scotland’s all-renewable 2020 target. As the power generation pattern of solar PV fits nicely with peak daytime demand, which happens around noon, solar PV was able to reduce the daytime peak price of German electricity by 20% when PV provided only 3% of the energy in a year. The GIFTS spreadsheet shows how PV and wind can provide around 80% of the UK power in a year and bio-electricity the 15% flexible back-up with around 5% storage. Had it not been for the Westminster government’s subsidy cuts the UK could have had an all-renewable power supply by 2025. Keith also suggested that UK should fully tap the potential of flexible bioelectricity from food and farm waste and pumped hydro for storage especially in Scotland.
As all of the case studies were based on UK data, it is important to assess the situation in Scotland alone. Through analysis of installation data, Keith argues that Scotland could achieve its all-renewable target by 2020 with huge contribution from wind energy even under a business-as-usual scenario. However, the all-renewable target is insufficient to supply for 100% of electricity demand hour-by-hour by 2020.
To achieve this, a paradigm shift especially in solar PV installation is imperative. Solar PV installation experienced exponential growth from 2010 to 2014 thanks to the introduction of Feed-in-Tariff (FiT) in 2010, but was plateauing from 2015 to 2018. With the FiT ending in 1 April 2019, solar PV installation could see a further stagnation if new policy is not in.
A detailed analysis of hourly supply and demand with the GIFTS spreadsheet was undertaken by Environmental MSc. students and showed that considerably more flexible bio-electricity is necessary. However, the amount of farm and food waste sent for Anaerobic Digestion, which then provides biomethane for the gas-grid, can be counted towards Scotland’s hour-by hour all-renewable target. Also, so can the proportion of households that have switched to an all-renewable electricity supplier. It was extremely encouraging that a show of hands indicated more than half the audience had switched.
The current practice of analysing annual total energy demand and supply does not give due recognition to solar power’s significant contribution to supply for peak energy demand and the complementary effect of wind and solar power, but encourages base load generations such as nuclear power.
Invitation for Collaboration
Thus, Keith proposed to work with SSEG and the Scottish renewable energy sector to conduct hourly energy supply and energy demand analysis to assess the potential of renewable energy in Scotland.
Analysis would require:
TALK and revelries