Friday, March 6, 2015

Too cheap to meter

It's going to be a bright sun shiny day
    Jimmy Cliff

The futures so bright
I gotta wear shades
     - Timbuk3


       I've been seeing all sorts of great stuff on renewable power lately.    Stuff like :PV cost drops 99%;  By 2030 All new energy will be provided by solar or wind.- All new mass-market vehicles will be electric.   

         I hope its all true, but as suggested below, the renewable world we are heading for may not look quite the way its portrayed.  

   The touchstone for a lot of this optimism, is a 2013 study by Mark Jacobson of Stanford University,  discussing a way for New York State to be powered purely by renewable power  see here.  For a review of a critique of that study by researchers in the Engineering Dept of Carnegie Mellon  see see here.   for other critiques see here.    Let's just say that this feasibility of his appraoch is still an open question.  

      But, let's not be so negative.  Suppose it were all true. 

     I recently came across a really good essay by Richard Heinberg, of the post Carbon Institute. Entitled " Our renewable future ".  It really covers all the bases, and I recommend you read for yourselves.   Here is an interview with him, which will also give you the flavor of the article.

      He makes a lot of good points.  First, of course we need to stop burning fossil fuels!  ( Which is no big surprise to hear from a  "post carbon" fellow! ).  So we need to move to an all renewable economy.   And of course that means lots of wind and solar.      

       So, lets fast forward to 2030, or when ever.  The remaining coal is left in the ground, either through carbon taxes, or market forces.   Most of energy consumption is in the form of electricity, generated by wind and solar.

       First, energy will be a lot more expensive.   This may seem inconsistent with the dropping price of solar panels. One reason is that, capacity costs for wind and solar are much higher.  This is from a Brookings Institute Report

"To place these additional costs in context, the average cost of electricity to U.S. consumers in 2012 was 9.84 cents per KWH, including the cost of transmission and distribution of electricity. This means a new wind plant could at least cost 50 percent more per KWH to produce electricity, and a new solar plant at least 200 percent more per KWH, than using coal and gas technologies."

      Furthermore  "all renewable" system will need more than just turbines and panel.  It will need storage.  (and lots of long range transmission)  .    This storage problem is what stopped the folks at Google, who looking into creating a renewable package that was cheaper than fossil fuels.  They couldn't do it with today's technology, and couldn't foresee a way it could be done in the near future.

       It's interesting to see what the Google folks actually said.  They were hoping to start a market transformation - one that  would make fossil fuels unnecessary, and would eventually bring the CO2 down to 350ppm. 

       "We decided to combine our energy innovation study’s best-case scenario results with Hansen’s climate model to see whether a 55 percent emission cut by 2050 would bring the world back below that 350-ppm threshold. Our calculations revealed otherwise. Even if every renewable energy technology advanced as quickly as imagined and they were all applied globally, atmospheric CO2 levels wouldn’t just remain above 350 ppm; they would continue to rise exponentially due to continued fossil fuel use. So our best-case scenario, which was based on our most optimistic forecasts for renewable energy, would still result in severe climate change, with all its dire consequences: shifting climatic zones, freshwater shortages, eroding coasts, and ocean acidification, among others. Our reckoning showed that reversing the trend would require both radical technological advances in cheap zero-carbon energy, as well as a method of extracting CO2 from the atmosphere and sequestering the carbon."
(Paradoxically, although the reenewable power wont be sufficient to stop Climate change, it may be enough to drive the Utilities into a death spiral.   NYT:  Solar power growth falters as utilities balk     But see Interesting bill in Oregon -  Bill to ban coal, limit natural gas expansion)

   Second, the energy costs of the all renewable system ( including storage) are also high.  This means they have a low EROI.   So there will be less energy " profit" to run all the non energy parts of the economy. 

    Heinberg refers to the EROI study by Weißbach et al., Energy 52 (2013).        Found here.  In that paper the EROI of solar,  wind , and solar CSP (with storage) is found to be 1.8, 3.9 and 9.   In contrast coal and nat gas generation are 30 and 28.    The following chart provides some idea of what "energy profit" is needed to support various non-energy activities.

      Happily,  this problem doesn't arise immediately, as long as we continue to use fossil fuel plants as our energy storage.  As it stands right now, we can add solar and wind any time we want, and fossil fuel plants to back off.  In the evenings or when the wind is low, the plants pop back on.  (see graphs below - illustrating Germany's solar generation profile over the day.  

      In the US, non hydro renewables provided 7.3 % in the first half of 2014.  That's a small enough amount to be fair;y easily addressed.  Its not clear how high that can get before causing trouble.  Estimates range from 30-80%.  Heinberg says:

"Grid managers tend to say that the inflection point arrives when solar and wind power provide about 30 percent of total electricity demand, though one computer model suggests it could be put off until 80 percent market penetration is achieved. (For two contrasting views on the question of how expensive and difficult intermittency makes the renewables transition—from renewable energy optimists Jacobson and Delucchi on one hand, and from “The Simpler Way” advocate Ted Trainer on the other—see a highly informative peer-reviewed exchange herehere, and here.) 

  So, how will things look in 2030?  Well hopefully we will be well on our way to the "renewable" economy.  If not we will have locked in 2 degrees, probably more.    Perhaps there will be a barrtery breakthrough.   But don't bet on it.  See this article from MIT Technology Review  Why we don't have battery break throughs:       


Large scale grid integration of solar power – many problems, few solutions

by Roger Andrews
On Sunday, July 7th, 2013, a day of unbroken sunshine and low demand, solar PV generated approximately 200 GWh of power, over 20% of Germany’s total electricity production for the day. (I’m indebted to CleanTechnica for the bar graphs):
And because peak sunshine and peak demand are more or less coincident on summer Sundays in Germany there was no serious problem admitting all of this solar electricity to the grid:

There was, however, one minor difficulty. The surge of solar power caused generation to exceed consumption for about ten hours and as a result about 13% of it, shown by the orange bars at the bottom of the graph above, had to be exported to other countries in the Central West Europe market region. The graph below moves the orange bars up to the top to illustrate the size of the surplus relative to consumption:
Surpluses like this are of course not large enough to cause a problem, and can in fact be eliminated simply by backing off a little on other forms of generation. But solar supplied only 5.7% of Germany’s total electricity generation in 2013, and if this is as far as it ever gets it’s not going to move Germany very far along the path to sustainable energy. Solar has to get much bigger to do that, and here we will briefly examine some of the obstacles that stand in its way.
How much bigger does solar have to get? Market analysts have predicted that it could ultimately supply 25% of Germany’s electricity, so we’ll use that as the target. Meeting it would require scaling up by a factor of 4.4 relative to 2013, with annual solar generation increasing from ~30TWh to ~130TWh and installed solar capacity from ~35GW to ~ 150GW. We can’t of course predict what consumption will be when and if this happens, but if 150GW of solar PV capacity had been in place on July 7th, 2013, this is what the generation mix would have looked like:
There would have been huge oversupply of solar electricity. Solar would have generated ~800 GWh, representing about half of total German electricity generation for the day, but only about 200 GWh of it could have been admitted to the grid, barely more than was admitted to the grid in 2013, all other things being equal. So in this example expanding PV capacity by a factor of 4.4 would have increased solar penetration by a effectively zero. (Note that the numbers given here and later in the text are scaled off graphs and are therefore approximate, although this does not impact the basic conclusions.)
However, conventional generation would presumably have been cut back to accommodate as much of the solar surplus as possible, and the graph below summarizes the impacts of doing this. By cutting conventional generation to zero between 8 am and 5 pm (wind, hydro and biomass generation are left unchanged) about 450 GWh of solar, representing about 45% of total generation, could have been admitted to the grid. But this still leaves a surplus of about 350 GWh:
And July 7th was a fairly typical summer Sunday. The solar surplus would have been similar on most weekends during the summer of 2013. Weekday surpluses would have been smaller because weekday demand averages 10-15 GW higher than weekend demand, so more conventional generation could have been taken out of service to admit more solar, but weekday surpluses would still be on the order of 150 GWh/day. The average of the weekend and weekday surpluses would be around 250 GWh/day.
A rough calculation based on these numbers indicates that if Germany installs enough PV capacity to supply 25% of its annual electricity consumption, and if no storage capacity or other means of matching production to load is available, and if the load curve remains substantially the same as it is now, about 20% of the solar electricity would have to be “spilt”, meaning that Germany would actually obtain only 20% of its electricity from solar. Additional PV capacity could be added to increase the solar contribution, but most of the added generation would get wasted because there would be nowhere to send it. Clearly the approach of expanding PV generation without anywhere to store the surplus power is not viable.
The question therefore becomes, is there any way of storing solar power surpluses for short-term re-use? Not with solar PV using existing storage technology. But it could be done with concentrated solar power (CSP), which uses heliostats to reflect solar energy into heat-retaining reservoirs containing a fluid (usually molten salt) that delivers steam to conventional turbines both when the sun is shining and when it isn’t. CSP plants can in fact act as load-following or even baseload capacity if enough storage is available, and this capability has been demonstrated at the Gemasolar CSP plant in Spain, which last year completed 36 days of continuous 24/7 operation. (Even Forbes was enthusiastic.)
So why aren’t there more CSP plants? Because a) they aren’t suitable for domestic use and b) they are much more expensive than solar PV plants.
But capital costs are actually not all that much higher. The Gemasolar plant (technical details here) is an example. It has a rated capacity of 19.9 MW and cost 230 million euros to build, which works out to 11,500 euros per installed KW, roughly five times the cost of a 19.9mW PV plant. Ofsetting this, however, is the fact that Gemasolar produces ~110 GWh a year, about three times as much as a 19.9 MW PV plant would produce, and at a much higher load factor (officially 63%, with recent estimates of up to 75%).
How can a solar plant have load factors this high? Because 19.9 MW is the capacity of the turbines, not the capacity of the solar array. The heliostats that melt the salt that produces the steam that drives the turbines in fact have a capacity of 76 MWe (304,750 sq m at 2,172 KWh/sq m/yr), giving an installed cost of slightly over 3,000 euros/KWe, not that much higher than the cost of an equivalent PV array. The 17% load factor calculated using the 76MW number is also comparable to the ~18% average for PV plants in Spain.
On a levelized cost basis, however, CSP electricity is about twice as expensive as PV electricity, with the Fraunhofer Institute estimating levelized costs at 6-10 euros/KWh for PV and 14-19 euros/KWh for CSP. But as Fraunhofer points out: “the advantage of the ability to store energy and the dispatchability of CSP …. was not taken into account.” How big an advantage is this? In the case of Germany very big indeed, because with CSP it could generate 25% of its annual electricity from solar with effectively no spillage at all.
So what’s not to like about CSP? Three things. First, it doesn’t work very efficiently at 50 degrees latitude, but for the purposes of analysis we can consider Germany as a generic example that would apply to sunnier countries closer to the Equator, such as the US.
Second, CSP storage can smooth out only short-term fluctuations. It can’t smooth out the huge seasonal changes in solar output that occur at higher latitudes and which are usually anticorrelated with demand. The next two plots of total monthly electricity generation and solar generation in Germany illustrate the problem (data from Fraunhofer):
Even with solar providing only 5.7% of Germany’s electricity, as it did in 2013, Germany would have to install about 8 TWh of storage to convert the seasonal fluctuations in solar output into continuous baseload generation, and at the 25% level it would need over 30 TWh. Installing this much storage capacity in Germany or anywhere else for that matter is far beyond the bounds of feasibility (current worldwide pumped storage capacity amounts to only 1 TWh). With 25% annual CSP generation Germany would therefore get 40-50% of its electricity from solar in the summer when it least needs it but only about 5% of its electricity from solar in the winter when it needs it most. So while expanding CSP capacity will have a positive overall impact on Germany’s renewable generation mix it will do little or nothing to reduce the requirement for large amounts of conventional backup generation.
Note: Some of the winter shortfall could theoretically be filled by wind power, which is positively correlated with demand over the seasonal cycle in Northern Europe, but integrating large quantities of wind power with the grid poses problems of its own. These problems were discussed in earlier posts herehere and here.
Third, it would be roughly three times cheaper for Germany to add low-carbon generation capacity by building nuclear rather than CSP plants, and nuclear delivers power at a steady rate without the need for storage and whether the sun is shining or not.

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