A simple model: limiting storage capacity

In my series on the impact of intermittent power sources, I got to the point where I was working with a unlimited battery capacity to find out how big that storage needs to be to fill in the gaps of less production with stored power from earlier excess production. I came to the (surprising) conclusion that almost 2,500 GWh was needed to fill in all the gaps. To recap, this is how the stored power looked like over the year:

Solar Wind capacity model - charts007c - scenario x8.57 reference year 2018: with 2500 GWh storage

Which I found an awful high number for storage. Therefor my question back then was: is it really necessary to store all that power? What would happen when storage is limited to a value below the optimal capacity?

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A simple model: the amazing November dip

This post is a follow-up to the previous post, where I looked into the scenario of an unlimited storage device topping off the excess electricity at peaks and filling in the gaps when there is a shortage. I found that a storage capacity of about 2,500 GWh was needed to fill in all the gaps. That number seemed very high to me, so I wanted to check whether other people also found such large numbers.

I quickly found a back-of-the-envelope-calculation by the late David MacKay. He proposes that 33 GW of wind power, delivering on average 10 GW, needs roughly 1,200 GWh backup. This is his calculation:

10 GW × (5 × 24 h) = 1,200 GWh.

He starts from the assumption that it is necessary to bridge five consecutive days of no wind. The difference is that he only considers wind, while I also include another intermittent energy source (solar).

The average delivered power is rather similar in both cases. In my scenario I have ((3,369.05 MW x 0.12) + (3,157.185 MW x 0.24)) x 8.57 = 9,957.95 MW.

Which is a tad below the 10 GW of MacKay is working with. Yet, my result is almost twice as high. Is this the influence of another intermittent power source in the mix? Or just a coincidence? Or did I do something wrong?

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A simple model: shaving off peaks to fill in the gaps

A bit later than I anticipated, a follow-up on previous post where I presented a simple model that gave the opportunity to learn about the mechanisms that determine an increase of intermittent energy sources (solar and wind). It confirmed that, when increasing in capacity, the production lows don’t grow much, but the production highs will steeply increase. Which is, mathematical speaking, rather logical. In practice this means that the need for backup will not decrease much with increasing capacity, but that at the same time measures need to be taken to top off those ever growing peaks.

That led to the next question: is it possible, at least theoretically, to save the surplus electricity from production highs and use it later when there is not enough electricity at production lows? I adapted the model to a scenario that when more solar and wind energy is produced than consumed, then the excess energy will be stored and when less solar and wind energy is produced than consumed, the system would try to retrieve this from storage.

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A simple model: when capacity of solar and wind increase

In previous post, I described the particular dynamics in which electricity production from intermittent energy sources, when growing in capacity, will not increase much at the production valleys, but will steeply increase at the production peaks. This means that, when capacity increases, the needed backup capacity will stay high, even at multiples of the current capacity, but at the same time measures have to be taken to suppress the ever growing peaks.

I illustrated this with a (celebrated) record high of wind production on June 8, followed by a (neglected) low production (June 9). In less than 12 hours, the production fell from almost 3,000 MWh (capacity factor of 81%) to almost 20 MWh (capacity factor of 0.5%). This illustration was only for electricity production by wind energy. There is a complicating factor: solar is also an intermittent energy source and can intensify as well as dampen the effect of wind.

That made me wonder how this interaction would look like when capacity of solar and wind increases over time. In real-life, this is not witnessed yet, this is still to come. It is however possible to study the dynamics of such a system by modeling it.

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A new record for wind energy (during a storm)

A storm headed over our country at the end of last week. That inevitably means advocates of wind energy praising how wonderful wind energy is doing and how much electricity was produced by wind. That is exactly what happened and apparently we even have a new record…

It was Chris Derde (manager of energy provider Wase wind) who broke the news. He tweeted that wind energy had a “new record production of 3 GW” and that nuclear power plants lowered “their production by 0.5 GW”. This was one of the two images that accompanied the tweet, illustrating the record:

Tweet Chris Derde 20190608 chart wind

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“Extends” or “could extend”, that is the question

This is the wrap-up of the vehicle-to-grid series. In this post, I will go back to the article bringing the news that vehicle-to-grid networks increase longevity of electric car batteries. Now that I read the paper and have shed some light on several aspects, I re-read the article to find out whether the author was correctly representing that paper.

Unfortunately, this is not the case. It already starts with the title (translated from Dutch, my emphasis):

‘Energy storage in electric car extends the lifespan of the battery’

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Minimize battery degradation or minimize damage from battery degradation?

In the series of posts on the battery-life saving algorithm of the University of Warwick, I made (twice) the remark that the managers of vehicle-to-grid programs would not be very keen in implementing such an algorithm. This because this algorithm, although it is hailed as a break-though, will have a negative impact on the primary purpose of these schemes, therefor tolerating (some) battery damage might be the preferred option.

That made me wonder whether I could check this. The Warwick paper was published two years ago and the Smart Solar Charging program was presented as having developed its own bidirectional charging stations, so if there is some ability to make improvements based on this supposed break-through, then this project should be the one that will show it.

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