The sweet spot for UK renewables

Renewable energy over the last ten years has evolved substantially and increased beyond expectations, both in terms of installed capacity and generation. Countries across the world are participating to expand the renewable energy sector, and we recently had record wind output in the UK.  A key limitation of renewable energy is its intermittency and new projects are beginning to tackle this through storage.  Here we look at two recent innovations – one on a Pacific Island and one from Germany.  We look at how much renewable energy has evolved in the UK, what weather conditions lead to record breaking conditions, and whether we are likely to meet our 2020 target.

Leading by example

Ta’u Island in the Pacific has abandoned the use of diesel generators and have become entirely self-sufficient by relying solely on solar panels to generate the island by harnessing the heat from the South Pacific sun (Article from The Guardian).  The island is using more than 5,000 solar panels and 60 Tesla power packs for its electricity supply, which diminishes the need for delivery of gallons of diesel from the main island Tutuila.  Their 1.4 MW of solar generation capacity is enhanced with 6 MW hours of Tesla battery storage, so that enough energy can be stored to supply power to the island for three full days with no sun.

UK progress

It is unlikely that the UK will reach comparable achievements to Ta’u in the foreseeable future. However, we are making progress.  In 2015, fossil fuels contributed a record low,  for at least 5 decades, towards UK energy supplies.  Coal use fell by 21% from 2014 to 2015 and usage has continued to decline in 2016.  In contrast, renewable energy output – in the form of wind, solar and biomass – increased from 2014 and 2015 (Figure 1), with solar having the greatest increase and meeting 2% of UK’s electricity needs in 2015 (Carbon Brief, 2016).

Development in UK wind and solar installed capacity (Source of data: DUKES)

Solar success

In May, July and August 2016, solar generated more electricity than coal for the first time on record. Increases in solar capacity are expected to continue in 2017.

Looking forwards, a company called Colas are implementing a pilot study at three test sites in the UK next year, whereby solar panels will be fitted to large stretches of road and the energy then used to power buildings. The material is photovoltaic and can be glued to the top of road surfaces and can withstand weights of even the heaviest of vehicles, 12 feet of covered road surface can power a home for one year, given 1,000 hours of sunlight is received (Cassey, 2016). One of the test sites for the pilot study is expected to be conducted in Cambridge, where, on average, 1200-1600 hours of sunlight a year is received (Figure 2).

Figure 2: Average annual sunshine hours. (Source: Wikimedia commons)

Blowing away the wind power records?

High or even storm force winds, like those seen repeatedly in winter 2015/2016 (LSC blog: S is for Storm), may seem like the perfect conditions for higher wind generation, thereby suggesting that with a calmer winter so far this year (Figure 3), wind generation would be lower than last year.

Figure 3: Mean wind speed at the surface for 1st November 2015 to 4th December 2015 (left) and 1st November 2016 to 4th December 2016 (right). (Source: NOAA ESRL PSD)

However, this is not the case: a ‘sweet spot’ exists, whereby the maximum output from wind turbines is generated at around 16 m/s (when there are no transmission constraints), and they start shutting down in high winds to prevent storm damage (Figure 4).

Figure 4: LSC UK wind power curve

On the 22nd November 2016, the UK broke a renewable energy record whereby the highest ever wind generation value over a 30 minute period was recorded at 7.1 GW (Figure 5).

Figure 5: Half-hourly UK wind power output with dashed line showing highest value during the period

The average wind speed (across all regions in the UK with installed wind turbines, weighted by capacities) during the record generation period was 13.6 m/s, which under the Beaufort Scale is denoted as a “strong breeze”. Conditions which give the maximum half hour value are presented in Figure 6: the plot shows that offshore winds are high, whilst onshore winds are comparatively lower.  The sweet spot for maximum generation is comprised both of wind speed, but also the wind pattern.  This is more complex for the UK due to transmission constraints, a complex topic which is outside the remit of this blog!

Figure 6: Wind speed and direction on 22nd November 2016 at 11 am.

Evidence that maximum wind power production does not happen on maximum wind days is provided by wind generation figures over the last two years.  Table 1 shows the 10 highest generation periods and their associated wind speeds: favourable wind speeds for high generation are on average 14 m/s, ranging from 8.8 m/s to 17.6 m/s.

Table 1: UK Wind speeds associated with maximum wind generation hours

Overcoming intermittency

Germany are at the forefront of innovative ways of producing renewable energy and have plans to draw 100% of its energy from renewables in 2050 (Coren, 2016). Over the next year, Germany hope to overcome some problems faced my intermittent energy production by building new wind turbines that have built-in hydroelectric batteries. This will enable wind energy to be stored from the spinning blades by pumping water inside the turbines. When the wind stops, water then flows to generate hydroelectric power. The wind turbines have an installed generation capacity of 13.4 MW, with another 16 MW of installed capacity from the hydroelectric plant (see NaturStromSpeicher, 2016). The stored wind energy pumped via the hydro-electric power plant, has the potential to produce over double the amount of energy than the raw wind output alone.


Renewable energy has increased substantially in recent years and new innovative approaches worldwide mean the outlook is for a cleaner energy future. Improvements in energy storage are the next stage of a renewable future.

Within the UK, renewable energy currently accounts for 8.3 % of total energy consumption in the UK (Department of Energy and Climate Change, 2016).  Will the UK achieve its target of producing 15% of total energy from renewables in 2020?  2012 to 2015 saw over a three fold increase in installations, and this pace of growth would get the UK across the line… but that was an initial growth rate from a low starting point.  Certainly the new innovations will help the UK’s renewable output become more consistent.