SE Academic Review 2023

10 ST EDWARD’S, OXFORD

Wind energy potential has increased dramatically since 2009 with the development of offshore wind technology. This allows the UK to access the higher wind speeds available out at sea. In addition, wind turbines have increased substantially in height, further raising the average accessible windspeed. As shown in the data above, wind turbines are now nearly 60m taller, supporting an increase of wind speeds from 6.7m/s to 9m/s. In converting wind speed to raw power (kinetic energy), the wind speed is cubed. Therefore, even small changes in wind speeds add a sizeable increase in raw power. Raw power can then be converted into watts per m 2 by factoring in the diameter of the turbine blades. This has also changed significantly since MacKay, although it has little impact on the power as the larger wind turbines need to be spaced further apart, cancelling the diameter (Mackay, 2009, p. 265). The turbines cannot be placed closer than five times their diameter without significant power loss. Raw power x E ciency x x Diameter of blad 2 (5 x diameter of blade) 2 π = power / area 8363200 = 7.44 W/m 2 (current) (5 x 212) 2 ½ x density of air x wind speed 3 = raw power ½ x 1.3 x 9 3 = 474 W/m 2 (current) Figure 4. Power Per Area Calculation ½ x density of air x wind speed 3 = raw power ½ x 1.3 x 9 3 = 474 W/m 2 (current) Figure 3. Raw Power Calculation

In the last decade, photovoltaic solar panels commonly used in rooftops have increased in efficiency from 10-20% to 20-30% through technological developments such as using multiple layers of materials with higher efficiencies. With this increase, the watts per metre squared has risen from 5-20W/m 2 to 20-30W/m 2 . Additionally, MacKay had significantly underestimated the available area of south-facing roofs. Commercial buildings alone provide 2,500m 2 of space or 40m 2 / person. An even bigger area is available when we add in residential homes. This increases the roof yield potential from MacKay’s 5kWh/p/d to around 25kWh/p/d. Along with rooftop panels, solar farms could produce an additional 50kWh/p/d based on 5% of the UK’s total land area, providing a total of 75kWh/ p/d from solar alone. This would represent a huge step forward in reaching carbon neutrality. WIND Along with the use of solar energy, the UK has the potential to harness wind energy on a scale which could provide an abundance of energy. The table below highlights the largest changes that have taken place in the production of wind energy since 2009.

Global Energy Use

Figure 2. Offshore Wind

7%

16%

OFFSHORE WIND MACKAY (2009)

CURRENT

19% Raw power x E ciency x x Diameter of blade 2 (5 x diameter of blade) 2 π Getting Around Growing Things Plugging In Making Things Keeping Warm and Cool 27%

31%

Wind Speed (m/s)

6.7

9

= power / area

Height of Turbine (m) Raw Power (W/m 2 ) Blade Diameter (m)

70

128 474 212 50% 7.44

195

8363200

90

= 7.44 W/m 2 (current)

(5 x 212) 2

Efficiency

50% 3.07

Power per area (W/m 2 ) Total Surface area (km 2 ) Offshore wind potential

Global Energy Use

40,000

40,000

The upshot is that, although efficiency has not changed, the total energy potential has more than doubled from MacKay’s estimate due to the higher wind speed. A report by Wind Europe (2017), provides a more detailed analysis of the UK’s wind potential. Their calculations include transmission loss from the wind farms to shore, but still conclude that around 1,500 TWh/year is possible, or 62kWh/p/d with a possible upside of over 2,500 TWh/year if floating wind turbines can also be used economically. If we add in the power of onshore wind estimated by MacKay (2009, p. 33) at 20kWh/ p/d, there is plenty enough for the UK’s energy requirements. 400 Solar and Wind Capacity (GW) 300 100 200 0 2015 10 14 12 16 13 UK Total 79 UK Statistics Lighting 4 Gadgets 5 Defence 4 400 Solar and Wind Capacity (GW) 16% 7% 19% 27% Getting Around Growing Things Plugging In Making Things Keeping Warm and Cool

UK Energy Consumption

49kWh/p/d 107kWh/p/d 200

Transport Stu 12

350

MacKay, 2009, pp.60-64, 264: Wind Europe and BVG Associates, 2017)

31%

Stu 48

150

250

Food, Farming 15

100

Heating/Cooling 37

Jet Flights 30

50

20 13 22 13 24 14 25

Car 40

0

MacKay

2016 2017 2018 2019 2020 Target

UK Energy Consumption

200

Defence 4

Transport Stu 12

350

Stu 48

150

300

250

Gadgets 5

Food, Farming 15

Lighting 4