According to the graphs in previous two posts, wind energy was on average (annual as well as monthly) the most stable intermittent power source. There was also slightly more wind in winter (when demand is highest) than in summer (when demand is lowest), which theoretically may result in lower storage requirements. This in stark contrast with solar which is much less prevalent in winter and abundant in summer, thus entirely out of phase with demand and therefore the need for curtailment during summer and backup during winter. One might be tempted to come to the conclusion that wind energy alone would be the better intermittent power source, so why even bother with solar?

Let’s just test this theory. Would wind fare better on is own or is solar really needed in he mix?

First some assumptions:

• I will use he 2023 data from Belgium that I also used in previous two posts (source: demand, solar and wind)
• Production of electricity by wind or by solar+wind is 1.5 times demand (this is the most reasonable assumption that I encountered in my search of ways to make intermittent power sources work)
• Surplus production will be stored at a charging efficiency of 90%
• The gaps left by wind or solar plus wind will be filled in with storage at a discharge efficiency of 90%
• Production that could not be used and does not fit in storage will be curtailed.

Storage will be the bottleneck, so the power source that needs the smallest storage capacity without experiencing deficits over a one year period at our latitude wins this battle.

Let’s just jump in. This is how wind electricity production of 1.5 times demand looks like:

That is of course only one side of the story. Production higher than demand will be:

• or put in storage
• or curtailed (when storage is full)

(otherwise this amount of overproduction would fry the grid).

This is how it would look like when overproduction is creamed off:

The orange lines below the blue line means production lower than demand and this has to filled in by storage. The challenge is to dimension the storage capacity so it would not be drawn empty during the year (no blackouts).

Fiddling with the storage capacity, a capacity of 5000 GWh ensured that there were no deficits over the entire year. Meaning that wind and storage alone could manage the demand. More, there wasn’t even a need to have something in storage initially because there was already surplus at the get go. This because there is more wind during winter at our latitude (the start of the year is in winter) and January 1 is part of the Christmas/New Year holiday with less demand than average in winter.

This is how it looks like in the storage:

Although it came very close in September, there were no deficits in the simulation.

When storage is full and wind exceeds demand, the overproduction will be curtailed. These are the periods when curtailment of power was necessary:

Curtailment was mostly necessary in the beginning and at the end of the year (winter and early spring), but there was some curtailment in August too.

Now let’s compare with the same production, but this time adding solar to the mix. There was also no need for initial storage. Although solar production is close of it minimum at the beginning of the year, there was still enough wind to get something in storage before it was needed later on.

This is how intermittent production of 1.5 times demand looks like:

And this is only the production that wasn’t stored or curtailed:

The view into storage shows that it came close to a deficit in around February:

This most likely because February 2023 experienced less than average wind (see previous post) combined with a traditionally low production of solar at that time of the year.

There was however more curtailment, especially during summer:

This is most likely solar production because it is solar that is out of sync with demand (lots of it during summer when demand is lowest and hardly anything during winter when demand is highest).

Here are the numbers:

Wind clearly did not better than solar and wind combined, but maybe I didn’t ramp it for the advantages of wind to come through. During my search of ways in which intermittent power sources and storage could work, I also found one example with a production of 3.4 times demand. Although I think this is rather unrealistic, let’s try it anyway and see what happens. If I enter 3.4 as overproduction factor in the simulation, then it spews out these numbers:

Production of 1.5 times demand

Parameter	Wind	Solar + Wind
Demand 2023 (GWh)	78,866.65
Demand x 1.5 (GWh)	118,299.97
Simulated production (GWh)	118,299.97
Initial in storage (GWh)	0	0
Maximum storage (GWh)	5,000	1,900
Curtailed (GWh)	28,677.27	33,511.58
Conversion losses (GWh)	5,756.06	4,021.74

Also after ramping up production, wind did not do better than solar plus wind. Not sure what the reason for this is. Maybe the dynamic range is not wide enough in order to produce enough electricity in winter, yet staying out of the way in summer? Or maybe there are too many gaps left by wind that could be filled in with solar? Several windless days in a row is not unheard of while there is always at least some sun during the day.

Although wind is theoretically more in sync with demand than solar, adding some solar to the mix seems to help (drastically) reduce storage capacity. The flip side is that more production will need to be curtailed.

Production of 3.4 times demand

Parameter	Wind	Solar + Wind
Demand 2023 (GWh)	78,866.65
Demand x 3.4 (GWh)	268,146.61
Simulated production (GWh)	268,146.61
Initial in storage (GWh)	0	0
Maximum storage (GWh)	1,550	500
Curtailed (GWh)	184,661.64	186,910.53
Conversion losses (GWh)	3,068.32	1,869.43

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October 31, 2024 at 05:54PM