Economics of Renewable Power, simplified.

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GRA said:
WetEV said:
El Hierro has roughly two day's worth of storage. I don't think any reasonable design would need 400 days of storage.

To need 400 days of storage, you would need to be bridging gaps in production of over a year. Wind just isn't that variable.
Depends on what you mean by 'two days storage,' as that's highly dependent on how they use the reservoir.

Currently, they mostly seem to not be using the reservoir as pumped storage. However, if they pumped empty the lower reservoir into the larger upper reservoir, then used the water to generate electric power as it refilled the lower reservoir, the hydro power generated alone could provide enough for average load for about two days.
 
Judith Curry has an excellent guest post looking at the feasibility of a 100% renewable electricity grid in Texas. Texas is a good choice for evaluation since it uses 10% of all the electricity in the U.S., has excellent renewable resources, and has lots of available land area available for generation.

The article is encouraging about the technical possibility for achieving this goal. It will investigate costs in a second post.

One item which was particularly interesting to me was the mention of a new approach to long-term energy storage based on solid-oxide fuel cells which utilize CO2 and methane and can achieve a 70% round-trip efficiency. That's the kind of performance we need to achieve to make long-term storage a viable possibility.
 
GRA said:
http://euanmearns.com/an-independent-evaluation-of-the-el-hierro-wind-pumped-hydro-system/
Generally agrees with what many of us have been saying about the undersizing of the storage and the fact that the system had no hope whatsoever of achieving 100% wind even if it had worked as designed, but goes into far more detail about how much it's undersized, (possibly) why, and why it's been operated in the way it has been.
I went back to 2014 articles and found assessments of ~ 65% renewable generation. Still double the two year average output. I'd love to see a break-down of generation:

Wind power to grid
Wind power diverted to pump
Pumped water efficiency

It was interesting to note that the nameplate capacity of the wind-farm is about the same as the fossil fuel plant. That sounds way optimistic from the get go. Perhaps adding more wind capacity in the form of more windmills or a refit to bigger blades will help.

Addendum:
http://euanmearns.com/an-independent-evaluation-of-the-el-hierro-wind-pumped-hydro-system/

Does a good job of explaining the problems(s):
1. Inadequate storage (the upper storage turned out to be geologically unstable)
2. Very high seasonal variability

Their choice really does seem to be building excess wind for part of the year.
I wonder if the desalination could be a power sink.
 
RegGuheert said:
... and can achieve a 70% round-trip efficiency[/url]. That's the kind of performance we need to achieve to make long-term storage a viable possibility.

I disagree.

Long term storage is more driven by cost than efficiency. The opposite of short term storage.

Let me try out an example to illustrate:

$0.10 primary generation from solar cells. 10% ROI + expenses.
Li-ion batteries, $100 per kWh, 90% round trip efficient.
Flow battery, $1 per kWh, 25% efficient.

Cost for a short term storage: assumed to be once per day.

Battery total cost = energy cost + capital cost = 0.10/0.9 + 100*.1/365 = $0.14/kWh
Flow total cost = energy cost + capital cost = 0.10/0.25 + 1*.1/365 = $0.40/kWh

Cost for long term storage: assumed to be once per year.

Battery total cost = energy cost + capital cost = 0.10/0.9 + 100*.1/1 = $10.11/kWh
Flow total cost = energy cost + capital cost = 0.10/0.25 + 1*.1/1 = $0.50/kWh

To build a system with a minimum cost, some fraction of the storage should be low cost (and perhaps low efficiency) and some should be high efficiency and higher cost. Lowest cost will come with some amount of excess generation, enough short term storage to cover daily to a week or so, and some lower efficiency longer term storage.

This is the point to something like hydrogen fuel cells, which is a type of flow battery. Flow batteries are generally not potentially useful for cars, as the potential low cost technologies have low specific energy densities (kWh/mass).
 
WetEV said:
RegGuheert said:
... and can achieve a 70% round-trip efficiency[/url]. That's the kind of performance we need to achieve to make long-term storage a viable possibility.
I disagree.

Long term storage is more driven by cost than efficiency. The opposite of short term storage.
Actually, both long-term and short-term storage are driven by cost. (That's why there is virtually no installed storage beyond pumped hydro.) They have different cost drivers, but efficiency is a key driver for both of them.
WetEV said:
Let me try out an example to illustrate:

$0.10 primary generation from solar cells. 10% ROI + expenses.
Your example fails here. You assumed that the per-kWh cost of generation is the same for every bit of generation which is added. In fact, the per-kWh cost of generation goes up as more is added, since additional generation results in lower-and-lower additional kWh of generation. In the extreme case, once you have enough generation, additional generation has an infinite per-kWh cost since it provides no additional generation. (It may have other value, however, such as redundancy or margin.)

But we CAN readily calculate the relative costs of the low- and high-efficiency long-term storage options since the author of the article I linked provided details of how those two options impact the overall performance of the system. Here are the numbers:

RM = Renewable Methane
RMG = Renewable Mixed Gas

Code:
Component                 No Tier 2      RM       RM Cost      RMG         RMG Cost
-----------------------------------------------------------------------------------
Tier 2 efficiency                        34%                   70%            
Wind                        75 GW       75 GW       $0        72 GW         -$6B
Solar PV                    80 GW       80 GW       $0        75 GW         -$5B
Tier 1 storage             300 GWh     300 GW       $0       200 GWh       -$10B
Tier 1 inverters            60 GW       60 GW       $0        60 GW          $0
Electrolyzers                           40 GW      $20B       30 GW         $15B
Gas turbine generation                  40 GW(Exist)$0
Fuel cells                                                    40 GW        $280B
Tier 2 Storage                      14,000 GWh      $1B   18,000 GWh        $18B
====================================================================================
Total Costs:                                       $21B                    $304B
Cost assumptions:
Wind: $1/W
Solar PV: $2/W
Tier 1 storage: $100/kWh
Electrolyzer: $500/kW
Gas turbine: $3000/kW (But it is already exists!)
SO Fuel cell: $7000/kW
Tier 2 Storage (Natural Gas): Guess: Low since it can be stored in the existing pipelines and storage facilities.
Tier 2 Storage (CO2): Guess: $1/GWh

So this result agrees with your conclusion in that the lower-efficiency solution is cheaper. But the ONLY reason for that is that the natural gas generators already exist as does some of the natural gas storage. I used TODAY'S costs for solid oxide fuel cells. If in 2030, the solid-oxide fuel cells are the same cost or cheaper than natural gas turbines, then the result goes the other way by a long shot for systems that do not already have the gas turbines.

Let's see what the author comes up with regarding the 2030 cost model for these scenarios.
 
RegGuheert said:
Let's see what the author comes up with regarding the 2030 cost model for these scenarios.
O.K. Here is the author's follow-up post regarding the overall cost to move Texas to renewables by 2030.

Here is his list of projected per kW costs for equipment:

screen-shot-2017-08-05-at-7-00-13-pm.png


Here is what I had projected:

RegGuheert said:
Cost assumptions:
Wind: $1/W
Solar PV: $2/W
Tier 1 storage: $100/kWh
Electrolyzer: $500/kW
Gas turbine: $3000/kW (But it is already exists!)
SO Fuel cell: $7000/kW
Tier 2 Storage (Natural Gas): Guess: Low since it can be stored in the existing pipelines and storage facilities.
Tier 2 Storage (CO2): Guess: $1/GWh
So here is where we differed:

- My wind costs matched his high-end wind costs.
- My PV costs were about 3X his PV costs.
- My battery costs were about 2X his battery costs.
- My electrolyzer costs matched his low-end costs.
- My gas storage costs were about 4X his low-end costs.

Anyway, the author did not price the fuel-cell option. Here is what he came up with for system costs using natural gas generators:

screen-shot-2017-08-05-at-6-57-45-pm.png


The bottom line is that he projects wholesale costs to be between 6.1 c/kWh and 9.2 c/kWh in by the year 2030. If his numbers are in the ballpark, it seems possible that Texas could pull this off. They certainly have a much better chance than Germany of being able to do this.
 
Certainly TX has more solar, and probably more wind, than Germany. If only they would connect more to the US grid and send the excess to adjacent states.
 
Interesting article in Vox:

https://www.vox.com/energy-and-environment/2018/3/20/17128478/solar-duck-curve-nrel-researcher

The consensus is emerging that we can probably do 80 percent [renewables] with some combination of spatial diversity and short-duration storage.

For 100 percent, I don’t think we actually know what the right cost-optimal solution is. The seasonal nature of wind and solar is a problem.
 
https://www.cleanenergywire.org/news/renewables-cover-about-100-german-power-use-first-time-ever
Germany has crossed a symbolic milestone in its energy transition by briefly covering around 100 percent of electricity use with renewables for the first time ever on 1 January. In the whole of last year, the world’s fourth largest economy produced a record 36.1 percent of its total power needs with renewable sources.
At around 6:00 am on 1 January, a combination of strong winds and low demand after New Year's Eve celebrations meant that wind power alone produced about 85 percent of Germany’s power consumption, according to data provided by the Federal Network Agency. Hydropower and biomass installations covered the rest, as there was no solar power generation before sunrise.
Given the rapid growth of renewable energies, Germany has already reached its target of increasing their share of power consumption to 35 percent by 2020.

[youtube]http://www.youtube.com/watch?v=Rybpaqhg5Qg[/youtube]

[youtube]http://www.youtube.com/watch?v=VEh7V9_uIqM[/youtube]

[youtube]http://www.youtube.com/watch?v=YEQQl-qpkCc[/youtube]
 
WetEV said:
Interesting article in Vox:

https://www.vox.com/energy-and-environment/2018/3/20/17128478/solar-duck-curve-nrel-researcher

The consensus is emerging that we can probably do 80 percent [renewables] with some combination of spatial diversity and short-duration storage.

For 100 percent, I don’t think we actually know what the right cost-optimal solution is. The seasonal nature of wind and solar is a problem.
The seasonal nature of wind and solar is only a problem when one accepts paradigms that consider them to be a problem. The TIR process being used in a number of areas combines 100% renewable generation and a long-term storage solution that not only nullifies the seasonality of wind and solar, but of biomass and thus biomethane. And it does this while providing all needed energy of a modern industrial society,

The paradigm/plan/system must be selected before deep-dives into cost estimates are meaningful.
 
https://reneweconomy.com.au/portugal-reaches-100-renewables-ends-fossil-fuel-subsidies-32820/
Portugal’s renewable energy sources generated enough power to exceed total grid demand across the month of March, a new report has found, setting a standard that is expected to become the norm for the European nation.

...

The achievement comes nearly one year after hydro, wind, and solar power helped push the Iberian country to run on 100 per cent renewable electricity for 107 hours straight. Last March, however, the average renewables supply was 62 per cent.

The new record coincides with the move by the Portuguese government, last Tuesday, to suspend annual subsidies of around €20 million for guaranteed power supplies paid to producers – most of which goes to fossil fuel plants left in stand-by mode.

While fossil-fueled pundits in the US say it can't be done, the rest of the world is doing it. Move along - nothing to see here. :lol:
 
https://pubs.rsc.org/en/content/articlelanding/2018/ee/c7ee03029k#!divAbstract

80% solar + wind is feasible with 12 hours of storage.

100% requires several weeks of storage or more and/or large excess capacity.
 
WetEV said:
https://pubs.rsc.org/en/content/articlelanding/2018/ee/c7ee03029k#!divAbstract
80% solar + wind is feasible with 12 hours of storage.
100% requires several weeks of storage or more and/or large excess capacity.
If I am understanding the abstract correctly, they mention the worse case over a 36 year time frame. That is not the same as saying that 80% of energy use can be renewable, it just means that a couple weeks of back-up fuel is needed for uncommon events. Any bio-fuel can fill that role easily.
 
WetEV said:
https://pubs.rsc.org/en/content/articlelanding/2018/ee/c7ee03029k#!divAbstract

80% solar + wind is feasible with 12 hours of storage.
Shaner said:
Assuming minimal excess generation, lossless transmission, and no other generation sources,...
In other words: "No, that is NOT feasible."
 
RegGuheert said:
In other words: "No, that is NOT feasible."
In other words, the minimal excess generation covers the transmission losses.

I read the other day that high voltage, long distance DC lines can have as low as 1% losses. I don't know if that is even true but I think it correct that long distance transmission can be remarkably efficient.
 
SageBrush said:
RegGuheert said:
In other words: "No, that is NOT feasible."
In other words, the minimal excess generation covers the transmission losses.

I read the other day that high voltage, long distance DC lines can have as low as 1% losses. I don't know if that is even true but I think it correct that long distance transmission can be remarkably efficient.

DC was originally abandoned because it was too short range - it required a generator every mile or so. Either that was a typo you saw (AC lines have less than 5% losses in many cases) or they have developed a new kind of DC transmission.
 
LeftieBiker said:
SageBrush said:
RegGuheert said:
In other words: "No, that is NOT feasible."
In other words, the minimal excess generation covers the transmission losses.

I read the other day that high voltage, long distance DC lines can have as low as 1% losses. I don't know if that is even true but I think it correct that long distance transmission can be remarkably efficient.

DC was originally abandoned because it was too short range - it required a generator every mile or so. Either that was a typo you saw (AC lines have less than 5% losses in many cases) or they have developed a new kind of DC transmission.
DC lost in the Edison/Tesla competition at the level of the transformer. That has since been solved, although the DC transformer remains more expensive so DC lines are only price competitive for very long distances or very high voltages.

Addendum: The most advanced UHVDC line is 1100 kV, able to transmit 12 GW with 1.5% transmission losses per 1000 km. The technology has been improving rapidly in terms of performance and cost and I don't know of any reason that will not continue.
http://en.people.cn/n3/2018/0622/c90000-9474097.html
 
RegGuheert said:
WetEV said:
https://pubs.rsc.org/en/content/articlelanding/2018/ee/c7ee03029k#!divAbstract

80% solar + wind is feasible with 12 hours of storage.
Shaner said:
Assuming minimal excess generation, lossless transmission, and no other generation sources,...
In other words: "No, that is NOT feasible."

Some excess generation of renewable power is cheaper than storage. However, it is hard to find the economic crossover... So make an assumption that simplifies the calculation. Makes the answer a little worse than the correct value, by about 10%.

Transmission losses were 6.6% average for the most recent year for the USA as a whole, according to the US EIA. Makes the answer a little better than the correct value, by about the losses in the new network, which would complex to compute.

https://www.eia.gov/totalenergy/data/monthly/pdf/sec7_3.pdf

There are lots of other generation sources. Managing these will be complex. So just drop load, that is simpler to compute. But yes, not at all what would be realistic. I can't give a good guess as to how this biases the answer.

I don't see how you claim that the resulting 80% is feasible answer is very wrong. Sure, the study is a little wrong, maybe only 85% or 70% is feasible ... unless you add some excess renewable generation. Which they didn't.

http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
 
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