Thursday, July 24, 2014

Is the Renewable Revolution Over?

All graphs in this blog post are from the Renewables 2014 Global Status Report. A link to the full report can be found at the bottom of this page.

It is obviously premature to declare the renewable revolution over, however, the latest data on the subject does indicate a substantial deceleration in investments as well as on new installed capacity.

Below, we show some highlights from this report:

For the second year in a row, investments in renewables dropped. 

It could be argued that part of the reason for this drop is that prices of these technologies have been dropping, however, the growth year over year of Solar PV (photo-voltaic) and of Wind are beginning to moderate.

In Solar PV, the percent growths year over year have been:
2005: +38%
2006: +37%
2007: +29%
2008: +78%
2009: +44%
2010: +74%
2011: +75%
2012: +43%
2013: +39% (+26%)

In Wind, the percent growths year over year have been:
2005: +23%
2006: +25%
2007: +27%
2008: +29%
2009: +31%
2010: +25%
2011: +20%
2012: +19%
2013: +12% (+7%)

Sure, the bigger the installed base the more difficult it it to maintain youthful growth rates.

On the other hand, it was China, almost single-handedly that supported the growth of both PV and Wind in 2013. The numbers above in parenthesis don't consider China.

On the positive side, Solar + Wind + Geothermal + modern biomass have finally exceeded 1% share of global final energy consumption: 

Here is the link to the full report:

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Friday, July 11, 2014

Is Storage the Solution?

In the energy discourse we hear often that once the challenge of grid scale energy storage is implemented, wind and solar energy will be able to fully replace fossil fuels for generating electricity.

Instead of just staying at this philosophical level, let's make our homework.

This exercise is an oversimplification to illustrate the challenges of relying on intermittent sources for all of our energy.

Let's take Germany as our working example.

According to the latest report by the IEA (International Energy Agency), Germany consumed 551 TWh during 2013*. To convert this amount into average power we perform the following calculation:

     551 TWh / 365 days / 24 hours = 0.63 TW = ~63 GW.

The actual energy consumed by this country fluctuates hour by hour and seasonally. Germany tends to consume more energy in winter than in summer. However, to simplify, we'll make our numbers with the average power consumed.

Let's consider a solar capacity factor (CF) of 12% for this country (a little generous).

Also (and again with the purpose of simplifying our homework) we'll consider that every day of the year is exactly the same and thus that the daily capacity factor is equal to the annual one.

Thus, the installed solar capacity we would need is (considering 90% efficiency in the battery / inverter system):

     63 GW / 0.15 CF / 0.90 efficiency = 583 GW 

     (Today Germany has ~36 GW of solar installed capacity).

At the very least, the batteries would need to store 12 hours of power and this translates into:

     63 GW x 12 = 756 GWh

According to the Guinness Book of World Records 2013 edition, the largest battery in the world** (pictured below) can store 36 MWh. Thus, we would need this many to store 756 GWh:

     # Batteries = (756 GWh x 1000) / 36 MWh = 21,000

According to the Energy Information Administration (EIA), by 2040 global solar electricity production will be 452 TWh. This would be 82% of the 551 TWh Germany consumed in 2013 (and would "leave" nothing for the rest of the world).***

To calculate the required investment we need to multiply the cost of the solar watt (including inverters and installation) by 583 billion (see installed capacity above). Additionally, the cost of the storage needs to be added. We are easily talking here of more than a trillion euros.

However, these "rosy" numbers won't pass muster in the real world. Why? Because in the real world we have sunlight variations between days and, even more important, seasonality. Germany, for example, tends to consume more energy during winter when there is less sunlight.

Thus the above amounts would have to increase significantly. In other words, in real life we would need considerably more than the 583 GW of installed solar capacity and at the same time the batteries would need to store not 12 hours of electricity, but full days or even weeks. The required investment would thus be much higher than in the simplified case we presented above.

Conclusion: storage for renewable energy is not a silver bullet and it is doubtful that a fully renewable economy (solar and wind) would ever make sense in financial or even environmental terms.

Feel free to add to the conversation on Twitter: @luisbaram

Thank you.


1. Sure, the renewable energy doesn't have to be 100% solar. We could have a combination of solar and wind. This would obviously make the exercise much more complicated but would make more sense in the real world. However, solar and wind are not fully complementary. Solar (obviously) operates only during the day. Wind is more random. See graph below for the first months of 2012 where we can see that solar / wind do complement themselves somewhat. We can see that in January there was little solar production but was a very good month for wind. Then, July was a very low month for wind but had substantial solar production. However February (a full month) was low on both. More storage would be required for compensating those long lulls. Additionally, February was the month with the highest consumption in the first 7 months of 2012. (If somebody can share the full year statistics, they are welcomed). Let's bear in mind that the randomness of wind can only be somewhat compensated by solar during the day, so for half of the year (nights) wind is by itself.

2. Another concern is the variability of wind, here we can see annual variations (solar is more stable although its CF is considerably lower than wind's in Germany):

Both graphs are from the last reference below.



** According to the Guinness Book of World Records, this battery is "larger than a soccer field."


German capacity factors for solar and wind:

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Monday, July 07, 2014

By the Seat of Your Pants

Governments do things that would never pass muster in a disciplined corporation.

Imagine me going to the CEO of a company and telling him: give me 100 billion euros to invest in renewable energy (solar plus wind).

He would shower me with questions and demand a very carefully tailored plan.

The conversation would probably go this way:

CEO: what are you trying to achieve with those 100 billion euros?

Me: replace nuclear generation and reduce the carbon emissions of the electrical grid.

CEO: If nuclear is low carbon energy, why replace nuclear and not better fossil fuels?

Me: Because some people are afraid of nuclear.

CEO: Is that fear justified?

Me: For the most part, no.

CEO: Then why don't you spend a small part of that money in education / marketing / PR and better tackle the real culprits of Global Warming: fossil fuels?

Me: It makes sense.

CEO: Considering renewables need backup, usually fossil fuels, what is the floor of emissions an RE / FF electrical system would deliver?

Me: North of 300 grams per kWh if the backup is natural gas, north of 700 grams if the backup is coal.

CEO: Would that be enough to effectively combat global warming?

Me: No, sir, it wouldn't and today we already have important countries with electrical grid emissions well south of 100 grams.

CEO: How did those countries achieve their low carbon electricity?

Me: Without a single exception they did it mostly with hydro and / or nuclear.

CEO: Then, why are you proposing to spend loads of money on an unproven path?

Me: Well... Greenpeace says...

CEO: Greenpeace!  What do they know about energy?

Me: Not much, sir.

At this point, I was literally kicked out of his office.

Moral of the story: we cannot just pour gigantic amounts of money because we "feel" something might turn out to be a solution.

No, in the energy discourse we need to be disciplined, make our homework, evaluate alternatives and make rational choices not clouded by feelings.

Here is a suggestion respecting the basic questions we should answer during the homework phase:

Feel free to add to the conversation on Twitter: @luisbaram

Thank you.

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