This is the second update of last year's Bingham u3a STEM Group presentations relating to climate change and in particular renewable energy.
Which renewable energies are best?
There is a wide range of renewable energy technologies and a method has to be found to determine which is worth building. This is determined commercially using the strike price which is a price for wholesale electricity reflecting the cost of investing in a particular low carbon technology and is used to determine which generating plant are likely to be built in the future. Recent (2020) estimates put large scale solar and wind ahead of other technolgies, for example ...
- large scale solar - £44 per MWh (4.4p per kWh)
- onshore wind - £46
- offshore wind - £58
- tidal - £93 (with subsidy) to £150
- wave - no figures available
- combined cycle gas turbines - £85
- nuclear - £95
... so it is no surprise that wind and solar dominate the market for new plant. Many new sites are combined with battery storage which enables them to receive additional support for providing network resilience services such as backup and frequency control.
Capacity factor is a large factor in determining price
Capacity factor is the ratio of the actual annual electrical output in MWh compared to that which would be produced if the plant operates 365/24/7 and the strike prices take this into account. So solar power is cheap despite its very low capacity factor of 11% - a plant with a nameplate output of say 50 MW will produce only 5.5 MW on average. This low value is determined mainly by seasonal and daily variations in sunshine and cannot be improved upon.
The average offshore wind capacity factor in 2019 was 38.9% but this has been steadily increasing with projections of 58% for new-build as technology improves and turbine sizes increase. Some very interesting live data for Eurpope can be found here. A comparable average figure of onshore wind is 26.6% and we can expect similar improvement if and when more onshore turbines are built.
Wind power generation in 2020
In the UK, wind was the second most dominant source of energy, providing 24.8 per cent of the grid mix
Wind also set a new record for highest share in the energy mix on 26 August, when it contributed 59.9% of the nation’s electricity
The 1.2 GW third phase of the 3.6 GW Dogger Bank wind farm owned by Equinor and SSE will become the world’s largest offshore wind farm when complete in 2026. It uses the 248m high 14MW Haliade-X wind turbines |
| Credit: Dogger Bank |
Solar
The current installed capacity of utility scale solar power is 13GW peak but an astonishing additional 13GW is at the planning stage. Many are 50MW sites which do not require government approval and there are two local ones, the Belvoir Solar Farm near Barkestone and Green Farm Solar near Bottesford. These are ten times bigger than ones we are used to seeing and occupy a great deal of (low grade?) agricultural land so there has been some local opposition.
One example of the larger schemes is the 350MW Cleve Hill Solar Park in Kent, granted planning permission in 2020. Many of these solar farms are now combined with batteries to help in the management of the grid.
There are more renewable energy sites that you might think
Below is a map of current grid-connected renewable schemes, an an illustration of just how much effort has been put into clean power over the past few years. Just pan up or across to view the UK, zoom in and then click on a marker to show details of individual schemes.
Can we have too much renewable energy?
Electricity market prices have surged tenfold in a day to reach a new record high of £1,000 per megawatt hour, as colder than normal temperatures and lower electricity generation left a dent in Great Britain’s power supplies. (Guardian, 5th Jan 2021)
Fortunately, most consumers in the UK are protected against spikes of this sort though some electricity traders are not (hard luck on them). A similar cold period in Texas in February has caused blackouts as well as serious financial problems for unprotected domestic consumers. The problems in Texas were (unfairly) blamed on the State having too much renewable energy and it is a fact that integrating renewables into any grid presents many challenges to do with intermittancy and other factors.
In conclusion - a remarkable reduction in carbon intensity
The electricity supply sector leads the UK in the process of decarbonisation mainly due to the decline in the use of coal. For example, whereas coal has a carbon intensity of about 1,000g CO2/kWh, oil is 800g CO2/kWh, natural gas is around 500g CO2/kWh, nuclear, hydro, wind and solar are all less than 50g CO2/kWh. The figure below covering the period from 1970 summarises this progress as first nuclear plant, then gas-fired plant, then renewables displaced coal so that the average for 2020 had fallen to 181 g/kWhr. By 2035, emissions are projected to be less than 10% of those in 1970.
These annual averages hide the fact that there is considerable hourly variation - see below for December 2020. In May last year, levels dropped to an all-time low of 46g of CO2 per kWh on the 24th. It is likely that domestic consumers will be able to take advantages of these variations to reduce their own carbon footprint, making use of the features of their smart meters and even to trade the power from their electric vehicles back into the grid.
