The difficulties of meeting cyclic demand for electricity with intermittent renewable generation have been addressed in a number of previous posts, but with wind, solar etc. usually considered separately. Here we will examine a hypothetical scenario involving a diversified mix of renewable energy sources that supplies 100% of electricity consumption in unspecified future year 20XX in Atlantis, an imaginary island country that is very much like, but not exactly the same as, the UK.
Details of the 20XX generation mix in Atlantis are summarized in the following Table.
This mix generates the same amount of electricity as the UK, and we will assume Atlantis too, generated from dominantly thermal sources in 2013 (380 vs. 374 TWh). Dispatchable capacity (biomass and hydro) provides 35% of total generation and non-dispatchable capacity (wind, solar, tidal) the remaining 65%.
And because Atlantis is very much like UK the scenario assumes that demand in Atlantis in 20XX will be the same as it was in the UK in 2013, so the 2013 Gridwatch data for the UK are used to define 20XX Atlantis demand. Atlantis generation in 20XX was estimated using the following simplifying assumptions:
Wind generation is the same as UK generation in 2013 but scaled up in proportion to the increase in output.
Biomass is assumed to provide constant baseload generation, although biomass plants would probably be able to operate in semi-load-following mode in the same way as UK coal plants do at present.
Hydro generation is used in either baseload or load-following mode with a maximum output of 13GW and no ramping restrictions. (Hydro supplying 15% of the UK’s energy is of course a pipe dream, but it’s not a problem in Atlantis.)
Solar generation is estimated using total solar radiation values for latitude 53 north on the 15th day of the month and is kept constant through the month.
Tidal power generation assumes tidal generators spaced around the coast of Atlantis in such a fashion as to cancel out diurnal and semidiurnal tidal fluctuations. (Tide times around the coast of UK vary enough to allow this to be done). Generation is estimated by straight-lining between a spring tide maximum of 5GW and a neap tide minimum of 1GW in accordance with the 28-day lunar cycle.
Imports and exports are not taken into account.
Cost is no object.
Generation from all sources was estimated at ~5 minute intervals to match the Gridwatch reading interval.
To keep the post to a manageable length only the power balances in the months of July and January 20XX, which are assumed to be “typical” summer and winter months both in the UK and Atlantis, are considered.