Solar Radiation & Wind Speed
Blaise Kelly
14/11/2021
Comparison of Solar and Wind potential
Using the ECMWF cumulative solar irradiation and average daily wind speed data, it is possible to compare daily average generation potential for any location in the world. This gives a visual indication of how solar and wind complement each other.
Why solar and wind
Solar and wind energy are the cheapest sources of electricity. Generally, in northern Europe there is a lot more wind in the 1st and 4th Quarters of the year and a lot more sun in the 2nd and 3rd. When the weather is calm there are often fewer clouds meaning more sunlight reaches the ground.
The ECMWF reanalysis data covers the entire world. They are produced using a combination of Satellite and ground observations and modelled to provide uniform and consistent meteorological data at high resolutions.
The datasets used for meteo data are the ERA5-Land and ERA5 Pressure level. The ERA5-Land is only available over land and is gridded at a resolution of approximately 9km (varies depending on the exact latitude, but has fewer modelled parameters than the ERA5 pressure level data, which also covers multiple levels in the atmosphere, and is available for around 250 parameters, however, the resolution is approximately 30km, significantly less than the land.
Hourly ‘solar surface radiation downwards’ (ssrd) estimates for the year of 2020 were downloaded from the ERA5-Land dataset and the ‘10m u (u10) and v (v10)’ components of wind from the ERA5 pressure level. Ssrd was summed for the day and the u and v components of wind were combined to give speed and direction for each hour. The speed was then averaged for each day.
solar surface downward radiation (ssdr)
Total direct and diffuse solar radiation from the Sun that is incident on the Earth’s surface (represented by this variable). To a reasonably good approximation, this is the model equivalent of what would be measured by a pyranometer (an instrument used for measuring solar radiation) at the surface. The data comes from the ECMWF as joules per square metre (J m-2) and is converted to watts per square metre (W m-2) by dividing by the accumulation period expressed in seconds.
wind speed at 10m
wind speed is derived from the 10m u (u10) and 10m v (v10) components of wind. U10 is the eastward component of the 10m wind. It is the horizontal speed of air moving towards the east, at a height of ten metres above the surface of the Earth, in metres per second. V10 is the northward component of the 10m wind. It is the horizontal speed of air moving towards the north, at a height of ten metres above the surface of the Earth, in metres per second. 10m wind height is almost certainly an underestimate for wind potential as most modern wind turbines are closer to 100m, with some offshore turbines well above that. THe ECMWF does have a 100m modelled dataset.
United Kingdom in 2020
