The goal of 100% renewable energy from intermittent wind, solar and battery technology is firmly established in California and Germany. These are the leaders that generally determine where the US and Europe are headed. The 100% goal was established by environmentalists and academics who back the achievability of 100% renewable energy with studies based on elaborate simulations. 

The trouble with elaborate simulations is that their assumptions are opaque. Most simulate generation and consumption but assume transmission that connects the two. Intermittent generation is simulated using a limited history. The combination of these assumptions assume massive transmission over unrealistic long distances and omits rare extreme events.

The graph above shows approximate yearly solar intermittency data for events affecting the entire state of California. The horizontal axis represents the duration in days of outages. The vertical axis represents the number of outages. The first data point on the left shows 20 outage events of duration one day. The point on the extreme right shows one event lasting around forty days every 150 years. The point crossing the horizontal axis shows one event lasting four days. On average events exceeding four days occur with rapidly decreasing frequency and are unlikely in any given year.

These intermittency events mostly occur due to winter storms. The worst storm recorded in California occurred in the winter of 1861/1862 when it rained for 40 straight days. The geological record shows that storms of this magnitude occur around every 150 years. The phenomenon driving these events are known as atmospheric rivers which transfer tropical moisture in quantities exceeding the flow of the Mississippi and which occur randomly. Other points on the graph come from recorded storm events, mostly atmospheric river events of shorter duration. 

Current solar tries to deal with these events through storage and excess generation and distribution. To simply supply nighttime electricity without consideration of outages takes about 25% of peak DC generation capacity. So 1 GW of generation needs approximately 250MW (2.5GWh) of battery storage. To cover outages of one day adds double this storage requirement (500MW). Four days adds 8X etc. Both solar and battery costs are heading for the magical $1/W and will probably go lower over time. 

As I have covered in prior posts, as we increase solar, wind and storage capacity, capacity factor falls and electricity price rises. Four days of backup triples the cost of electricity from generation alone. More storage costs more. It is clear that covering longer duration outages is economically very painful. Building storage that only gets used once a decade seems folly. At that duration it is hard to trust that storage would still work. Forty days is even worse. However that forty day outage can occur in any year, and when it happens electricity will be desperately needed. 

California could build excess generation capacity in neighboring states and build long distance transmission. Both of these are expensive and outage events can exceed the boundaries of California. This with some storage would possibly work but at a similar overall cost to building storage. 

Other parts of the US and Europe would have possibly worse long duration outage events. They generally are farther north and have worse winter weather than California. The graph details would vary but the overall curve is the same,  frequent short events and increasingly rare long events.

When we compare this solar energy situation with a Stratosolar solution, the long duration outage problem simply disappears. Stratosolar simply needs nighttime storage for a complete dispatchable non interrupted solution. As battery technology becomes viable, Stratosolar can use this and it also has the option to develop gravity energy storage. The cost of Stratosolar generated electricity with around $1/W for solar PV and batteries is considerably lower than today’s fossil fuel cost of electricity. Solar would be viable in the cloudy north. No geographical dependency.

By Edmund Kelly

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Covid-19 has had us in lockdown since March. Slowly we are starting to surface, but early signs of an upsurge in the US States that are opening up are not encouraging. Work however  is continuing.

Back in August 2017 I wrote this post on the debate between idealistic 100% renewables advocates from academia and more realistic engineering based renewable energy pragmatists.
This new study (downloadable from here) is from the pragmatic side and continues the debate. 

While being more pragmatic, the report is still largely from academia and is weak on the economic costs. The report covers electricity generation for the US. The key difference with the 100% renewables approach is the willingness to include existing nuclear and large hydro in the mix and reduce the goal to 95% renewables by continuing to include natural gas. They propose to up the rate of deployment of wind and solar and add long distance transmission.

All of this is eminently reasonable, but a realistic analysis based on capacity factors would show that solutions like this will raise the cost of electricity significantly more than they estimate. For the US a doubling or tripling of the cost of electricity is probably feasible except for the current toxic political environment. Perhaps a post Covid, post Trump political environment might be more accepting of tackling climate change?

This kind of plan is possible for the rich nations of the world with an existing electricity supply that is being augmented by renewables investment. Developing nations have to provide all new infrastructure so the capital costs are higher as the investment for natural gas backup generation and transmission are additional new costs. 

Electricity generation is only a part of a clean energy solution. Transportation is as big if not bigger. A mass adoption of electric cars would have a significant impact on CO2 emissions.It is increasingly plausible that electric cars could be the majority by 2035. Electrification of transportation combined with incremental electricity plans like this could significantly reduce the rich world’s CO2 emissions.

However the developing world is where all the growth in world energy use is coming from. The rich world high energy cost solution would significantly depress their economic growth potential. Historically this has been an insurmountable obstacle. 

Realistically, current partisan politics in the US also make high cost solutions unlikely and resistance in Europe is also growing. This gets us back to the central issue of economics. A renewable energy replacement for fossil fuels has to be lower cost to gain acceptance. Current renewable energy is more expensive despite efforts to portray it as lower cost by focusing on a narrow view of LCOE. Those who portray it as lower cost are reducing their credibility and threaten the long term viability of renewable energy.

The Stratosolar approach could realistically provide a cheaper renewable energy solution acceptable to the developing world.

By Edmund Kelly

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Stratosolar can make today's solar energy technology an economically viable replacement for fossil fuel generation for the rest of the world that cannot afford the expensive energy of advanced economies.

​By Edmund Kelly

It is becoming an accepted part of the current energy/climate narrative that renewable energy electricity generation from solar and wind has become economically competitive with fossil fuel generation. So if this is true why are renewables not growing and supplanting fossil fuels? Because wind and solar are relatively new and only account for a small part of overall generation there is little data to inform the debate which largely relies on theoretical solutions with lots of assumptions. Rather than a bottom up theoretical model that tries to estimate and sum unknown costs there is a simpler macro level approach that uses real total system data, does not make lots of assumptions and inherently includes all costs. 

The price of electricity is determined by the overall cost of generation, transmission, distribution operation and maintenance. Most of the cost is capital cost. Utilities use the revenue from selling electricity to repay the loans used to build the capacity. Revenue to pay capital costs is heavily dependant on capacity factor, the ratio of average output to nameplate peak output. 

There are two large markets, Germany and California where there is significant renewable generation in the region of 20% to 30%. Both markets are representative of the overall market and have historical data on overall generation capacity, actual generation and average price of electricity to customers. Dividing overall generation by overall generation capacity gives overall capacity factor. The graphs below show the resulting capacity factor along with the average electricity price to customers for both markets. 

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The historical data is on the left and projected capacity factor and price are on the right. Both markets show the same behavior. Capacity factor has fallen as renewable generation was added and existing generation was still needed as backup. As capacity factor has fallen electricity price rose. A simple model that calculates the price as a constant for each market divided by the capacity factor closely matches the price rise curve.  

As California capacity factor has fallen from 41% in 2000 to 29% today, price has risen from $0.10/kWh to $0.16/kWh, a 60% increase. The US national average  electricity price has remained constant at around $0.10/kWh. California has expensive electricity by US standards. Projecting forward to full renewable energy, capacity factor falls from 29% to 13% as generation capacity,storage capacity and transmission capacity are added and legacy fossil fuel capacity cannot be retired because of long duration intermittency. This results in electricity price rising to over $0.32/kWh, over three times the price for US regions without renewable energy. 

Over a similar period, as German capacity factor fell from 57% to 33%, the electricity price rose from 16 cents to 29 cents. Projecting forward, capacity factor falls to 13% as price rises to over 70 cents, over four times its price in 2000. German capacity factor is better than California mainly because California has a lot more hydro-electricity which has a low capacity factor and very high multi year intermittency due to droughts. The German price is higher than California because of high taxes and the use of feed in tariffs paid by electricity customers to subsidize renewables.   

So despite lower generation costs for renewables, the price of electricity is rising because of the rising overall capital costs needed to accommodate them in the grid. The costs are high and already are getting pushback in Germany. Germany's renewable energy growth has slowed and along with resistance to higher prices, NIMBY forces that object to windmills and transmission lines have curtailed growth. High prices in California are not raising political headwinds yet but as prices continue their inexorable rise it  is likely that there will be political pushback. Nobody is telling customers that the price for electricity will at least double as we try to meet our 100% renewables goal.

High electricity prices have economic consequences if your competitors have prices one third your level. California is rich, but the bulk of the world building new electricity generation is poor and developing. They cannot burden their economy with such high priced electricity. Current intermittent wind and solar cannot escape this increasing price. 

An acceptable renewable energy solution needs a lower price than fossil fuels.  That is where Stratosolar comes in. Without long term intermittency Stratosolar can eliminate the legacy generation and its high capacity factor provides much cheaper generation. The following graph shows price trends for a stratosolar solution for California. Prices stabilize at around $0.15/kWh while capacity factor grows and the legacy generation is phased out. Then capacity factor stabilizes at around 50% and prices fall to around $0.08/kWh. Stratosolar cost of generation is low but this price includes generation, transmission, distribution, storage and operational costs for California.

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The contrast is stark. With current wind and solar, prices will rise continuously for the foreseeable future. With Stratosolar prices will cease growing and fall below current levels for fossil fuels. This economic story is not understood or accepted but the evidence from Germany and California is there for all to see. A solution that imposes economic hardship on those least likely to afford or accept it is doomed to failure no matter how noble the cause. 

By 
Edmund Kelly

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Two clean energy narratives have become common refrains. One, that 100% renewables is achievable today and two, that wind and solar generation are cheaper than coal generation. However, we see that world CO2 emissions continue to grow every year and clean energy investment has been stagnant at around $300B/year since 2011. Investment is actually falling substantially in 2019 as China, the largest investor by far is pulling back its subsidy regime. These two narratives do not add up. If solar and wind are cheaper, why are we not switching over? Is it a great conspiracy by the coal, oil and gas industries?

​The answer is that neither assertion is what it seems on the surface. It is true that wind and solar generation can have a lower levelized cost of generation (LCOE) than coal generation. However the two forms of generation are not equivalent. Coal generation can be turned on when there is demand. Wind and solar generation only happen when the sun is shining or the wind is blowing and only sometimes lines up with demand. The world operates on energy on demand. 

As I have written in previous posts, the two large economies with the most clean energy (Germany and California) are facing the problems of intermittent clean energy as it becomes a larger percentage of the total. Energy storage needs to be added to combat intermittency. This exposes the 100% renewables assertion. The 100% renewables goal is aspirational based on continued technological development, not proven available storage technologies. It also either ignores cost or assumes very optimistic cost estimates. 

Numbers do not clearly represent the nature of the problem with intermittent energy sources which is not visible from simple average energy numbers. A graphical illustration shows the problem better.

The graphs above show hourly direct solar insolation in W/m2 for two example US locations, (China Lake CA on top and  Oak Ridge TN below) for the months of January and June 2000. The data is from the National Solar Radiation Database 1991–2010. China Lake is in the Mojave desert in California and is among the best solar resources in the US. Oak Ridge is in Tennessee in the US south and is representative of more average US insolation. Any two locations in the US would show the same general intermittency.

The yellow lines are terrestrial insolation and the blue lines are StratoSolar. Stratosolar is constant during daylight and zero at night.  Terrestrial is far smaller than Stratosolar and far more variable during daylight. The database covers hundreds of locations throughout the US for over a decade. These graphs are only a snapshot of two locations to graphically illustrate the problems with terrestrial solar and the benefits of Stratosolar.  

Because there is so much data it is very uncommon to show this data graphically. It is usually reduced to daily, monthly or yearly averages. Unfortunately averages do not show the high variability of terrestrial solar and there is no convenient number that captures this variability.  January and June are chosen to show the worst and best months. Both locations show reduced insolation and higher variability in January.  As the graphs show, even the Mojave desert, one of the best locations in the world has significant variability that even with far beyond daily storage will have power outages. Oak Ridge is more representative of average locations in the US. Here the intermittency in both summer and winter is far beyond what daily storage can handle. Even three days storage would not guarantee the reliability of power. 

These graphs illustrate the advantages of Stratosolar. The amount of storage to guarantee stable electricity supply is totally predictable. Stratosolar with daily storage is as reliable a source of electricity as coal or natural gas. Stratosolar gravity energy storage is far cheaper than batteries. Also Stratosolar gathers far more energy than terrestrial solar, about 3X at Oak Ridge. These advantages add up to far cheaper electricity than terrestrial solar AND fossil fuels. 

Intermittency is the Achilles heel of renewable energy that is only slowly being acknowledged. Stratosolar solves that problem and is far cheaper to boot.

​By Edmund Kelly