CHALLENGES TO CLEAN ENERGY, Part 1

Where the Sun Never Shines

Intermittency and Renewable Energy

Solar photovoltaics (PVs) and wind may seem like the best friends of environmentalists who want to take quick action to reduce harm caused by conventional fuels.  In a very literal sense, however, these energy sources are “fair weather friends,” because their power is not always produced when needed.  They are intermittent (irregular and to a degree unreliable) as opposed to dispatchable (provided immediately when demand requires it).

Almost all solar systems installed on buildings in the U.S. are grid connected.  They are “fixed” systems set at one angle the entire year, not tracking systems that point toward the sun’s angle at a given time of day to maximize energy harvest.  Most are fixed to maximize power collection since that is how these systems generate the most power and earn the most money.  However, in Texas, this does not assist the electric grid much when power is needed most.

Building-mounted PVs generally produce their peak power at High Noon.  Utilities in Texas peak at between 4 and 6 PM in the summer, and around 7 AM in the winter.

Theoretically, PVs can allow a home to be self-reliant.  In reality, a home using average amounts of electricity would be severely challenged to do this both economically and logistically.  When Austin has a week of rainy, almost sunless weather, which generally happens at least once a year, PV output can fall to as low as 1% of rated output.  Will the stand-alone home size its solar system for 100 times its average power needs?  Will this home fill its garage with batteries, which are quite expensive at even minimal sizes?  Will it have an inefficient noisy back-up generator that relies on expensive, polluting fossil fuel for this time period (which will have your neighbors brimming with joy)?

If you vault past these first hurdles, go further and ask how many survivalists will cut back their use by 25%, or 75%, on these and other days or weeks.  Will they use flashlights and cut off air conditioners to minimize power use?  Will they monitor the system every day, or several times a day?  Will they have access to a quick repair service if their home energy system blacks out?

Integrated solar/storage systems will have their place in the new energy future.  However, it will probably be to integrate with and enhance the existing grid during critical (and expensive) periods of peak generation, or for emergency back-up.  It will not generally be used to support rugged individualism.  The grid, then, becomes the ultimate storage battery.

Solar Energy and the Loch Ness Monster

Now assuming that electric consumers and utilities continue to install more solar capacity, and still want the convenience of the grid, there are going to be real challenges, or consequences, to system reliability.

Below is a chart created by the electric system operator for the state of California (CAISO) that is now quite famous in utility circles.  It shows the effect that deepening increments of solar energy have, and will have in the future, on the state’s electric demand profile.  It models utility-scale, as opposed to rooftop, solar cells that more closely correspond with peak demand.

Duck Curve

On a March day, you can see solar energy’s contribution (tan) building up incrementally under the green line of demand from about 8 AM until 4 PM when it peaks, after which the solar cells produce less power as the day progresses to the point of nightfall.  As years progress and more solar energy is placed on the system, the tan gap between the green line of system load and net load with solar gets even larger.

The Loch Ness Monster with high curved neck
Nessie (Shot on location)
Image: iStock.com/Matt84

 

Given its shape, some call it the “duck curve” because it resembles the shape of a deep belly with a rising neck.  Others call it the “Nessie curve” because it resembles the shape of a much larger mascot, the Loch Ness Monster.  Similar concerns pervade wind generation as well.

There is a profound difference, however, between this curve and the Monster: grid intermittency is real.  Solar and wind generation are weather dependent.  Any utility with a similar profile will have to adjust to this phenomenon to provide system stability.  This may require expensive electric storage batteries, less-expensive but bulky thermal storage, fast-ramping natural gas plants, or large amounts of “demand response” such as temporarily turning off electric water heaters, to balance intermittency.

Utility scale solar and wind will often also require expensive transmission systems to bring it from one part of a system, or state, to another.  Texas, for example, created its CREZ lines (Competitive Renewable Energy Zones) from North and West Texas to the Dallas-San Antonio corridor at a cost of $7 billion.1  As wind expands and utility-scale solar begins to make increments, renewable energy transmission costs will inevitably increase.

The “ultimate question” is: What percentage of intermittent renewable electricity can the grid handle?  This is particularly pointed at Texas, since the state lacks the geology necessary for any large amount of (currently economic) dispatchable renewable energy available in other places – hydroelectricity and geothermal power.

Searching for Nessie

In the past, experts have made a general estimate that an electric system can integrate 25% intermittency on an annual basis.  At various times of day and year, the percentage of intermittent power the system can absorb can be much higher than 25%.  However, to achieve higher percentages on an annual basis may require overbuilding intermittent power sources way beyond affordability.

If you always had to size a wind farm to provide the highest system peak demand at its lowest wind output, and had no storage, then the wind farm would be overproducing (“spilling”) most of its power for most of the hours in the year.

It is instructive to look at how some of the world’s renewable electricity leaders attained such a high degree of integration.  To do this, you have to look at the full context.  How much is intermittent vs. dispatchable?  How much does it cost?  How much can the situation be compared to where you live?

What you will find is that, while there are impressive examples and lessons that have been learned, no country or utility has truly solved the problem.  It is an ongoing search.

Hawaii

Kauai Island Utility Coop (KIUC) serves about 33,000 customers (about 67,000 people) on the 4th largest island in the state of Hawaii.  Due to its tropical climate (with abundant sunlight), mild temperatures (at least 74% of the households did not heat their home in 2013), and local energy resources, KIUC has attained one of the largest shares of intermittent electric power in the world – but it can only do it briefly, and with relatively high electric prices.2

The Coop can get as much as 75% of its midday needs from photovoltaic power, both from rooftops and utility-scale systems, for about 2 hours a day.  Another 15% is supplied by dispatchable renewable power from a biomass burner and hydroelectric plants.  The remainder is supplied by dispatchable oil-burning power plants.

The intermittent PVs are buffered by an expensive 10-MW battery bank that supplies short bursts of power (a few seconds in length) until the oil-fired generators can ramp up to fill the gaps.

However, this is at midday with fair weather.  The island’s peak demand takes place in the evening, when only about 18% of 2016 power was provided by the dispatchable biomass and hydropower.  So consequently, only about 37% of total 2016 electricity was provided by renewables.3

All this comes at a price.  Since the island’s power is still predominantly oil-fired, its retail power costs (including power plants and the grid that supplies customers) are typically 30 to 40¢/kwh.  (As a comparison, Austin’s average residential retail electric cost in 2016 was about 11¢/kwh.)  KIUC customers therefore have a higher tolerance to higher-priced renewable energy than the mainland U.S.

In an unprecedented expansion of renewable energy in the U.S., KIUC has signed a 20-year contract with national battery company Tesla to provide a 13-MW central solar array backed by as much as 4 hours of firm battery storage to meet part of its night-time peak. This will come at a wholesale price of 13.9¢/kwh beginning in 2017.  Texas ERCOT (Electric Reliability Council of Texas) wholesale costs were 4.1¢/kwh in 2014 and 2.7¢/kwh in 2015.4   

While there are currently several hundred Megawatt hours of battery storage around the U.S., almost all of this is experimental, or is cost justified as “ancillary services” (such as quick ramp up to fill in power gaps).  The KIUC project is the first solar/battery storage system in the U.S. that will be competitive with wholesale power supplied by the utility it serves, albeit a high-priced one.

Denmark

This small Scandinavian country has a territory only 16 times the size of Travis County.  Despite a population 5 times more than our county, the country only consumed 160% more electricity than Austin Energy customers in 2015.

In 2014, the Danish electric system had one of the largest percentages of renewable electricity in the European Union.  Approximately 41% of its power supply came from intermittent renewables (39% wind, 2% solar PVs), another 12% came from biomass, biogas, and solid waste.5  (Wind production actually increased 8% in 2015.)

Further, many of the plants that biomass is burned in are extraordinarily efficient.  (They use as much as 90% of available heat as opposed to 33% for older coal plants).  They are Combined Heat and Power (cogeneration) systems that generate electricity and reuse the waste heat to serve urban areas with piped-in district heating.6  Their efficiency is magnified further because many of these plants have onsite thermal storage.  This allows them to throttle down in times of high intermittent wind supplies while still providing essential heating needs, becoming de facto spinning reserve (generators that run at low power to be quickly ramped up or down with changing demand).

While about half of the country’s electricity does indeed come from renewable energy, it comes at a steep price, and with some curious trade-offs.

Denmark has among the highest residential electric prices in the world.  In 2013, it was 39¢/kwh, compared to Austin, at 11¢/kwh, and the average U.S. price of 12¢/kwh.7  The largest part of this cost is value-added tax that has nothing to do with the real price of electricity.  Still, the cost to operate the system was about 17¢ per kwh, and the combined high cost and taxes are a strong deterrent to consumption.

About 30% of the country’s biomass electricity is fueled by garbage incinerators.  Though the country recycles a high percentage of its solid waste overall, its household recycling rate was only 22% in 2013.8  Paradoxically, the more the country recycles, the less fuel it has, which raises the price of power from the incinerators since they run less often.  Denmark actually imports some garbage from other countries for fuel.9

The toxic ash produced by these incinerators is also a problem, with high concentrations of dioxins and furans from plastic combustion, as well as heavy metals from objects such as batteries.

About 21% of the country’s remaining biomass power (both electricity and heat) is from locally sourced straw pellets.  The remainder is from wood, with about 50% of this imported from other countries.  Several of its large coal plants, as well as some of its combined heat and power plants, have been converted to operate with wood pellets.  In 2013, the country used an estimated 2.3 million metric tons of wood pellets, virtually all of which was imported.10  Most of these imports came from other European counties, though about 2% came from the U.S.11

The majority of the high cost of wood and wood pellets is subsidized by the Danish government in order to limit (and eventually eliminate) coal to lower the country’s greenhouse emissions.

While these various factors have allowed Denmark to be a leader in renewable energy, the largest reason for its high percentage of intermittent wind and solar power is that it trades electricity with its neighbors.  It has several large high voltage transmission lines that connect to the larger Scandinavian grid.  It trades intermittent renewable power and surplus cogeneration with Norway’s hydropower, Sweden’s hydro and nuclear power, and Germany’s renewable and coal power.  Given that winter is Denmark’s peak season, it exports more electricity in winter (due to district heating operations) and imports more electricity in summer.

Denmark real-time electric trading
Screen-shot of real-time map for Denmark energy systems operator keeping track of imports and exports. Watch moment-by-moment electric trading online at http://energinet.dk/EN/El/Sider/Elsystemet-lige-nu.aspx

On July 9 of 2015, Denmark produced more than enough wind power to supply its entire demand.  At one point (3 AM), it produced 40% more than it needed.12  This was all absorbed by the neighbors.

Overall, Denmark’s electric use represents a small part of the collective use of these 4 countries.  In 2015, the overall percentage of intermittent renewable energy (not dispatchable hydro and biomass) for these 4 countries was only about 19%.13

SCANDINAVIAN INTERMITTENT RENEWABLE ELECTRICITY 2015

All Consumption Terawatt Hours

Wind/Solar Terawatt Hours

Percent Intermittent

Germany

563,630

126,318

22%

Sweden

135,537

16,666

12%

Norway

129,768

2,815

2%

Denmark

33,630

14,734

44%

TOTAL

862,565

160,533

19%

Seen from a distance, Denmark’s example is both inspiring and discouraging at the same time.  This tiny country is setting an example for the world, but the results cannot be duplicated where similar geography, peaceful neighbors, and tolerance for higher-priced power do not exist.

Iowa

Map of Iowa transmission lines connecting to other states
Transmission lines (purple) allow Iowa to trade electricity with other states.

The state of Iowa also generates a high share of electricity from intermittent wind power – 32% in 2015.14  The majority of the balance comes from coal, with gas and nuclear also contributing.  Unlike Denmark and KIUC, the state’s retail electric costs resemble those in Texas.15  Similar to Denmark, it appears that the state can do this because the state trades power with bordering states.  Iowa generates 20% more electricity than it consumes.

Norway

Norway also differs from Denmark and KIUC by obtaining almost all of its electricity from renewable energy at moderate costs.  Norway produced about 97% of its electricity from hydroelectricity in 2014, with residential prices below the average U.S. price, even after taxes.16

Costa Rica

During the Paris climate talks in December 2015, this small Central American country was toasted as a role model for the world.  In 2015, about 99% of its electricity was generated by clean energy.  However, in 2012, the country received 88% of its total generation from dispatchable renewables, with about 5% coming from wind and solar, and the rest from oil.17  While more intermittent wind and solar power have been built since 2012, the country’s electric system will be bolstered by the new 306 MW Reventazón hydroelectric dam that came on line in 2016.18  It is currently the largest hydro plant in Central America.

In June 2016, the country’s residential electric rates began at 13¢/kwh for minimum consumption levels, and quickly rose with higher use to 21¢/kwh.19

Iceland

Iceland received 71% of its electricity from hydropower in 2014, with the balance coming from geothermal power.20  Its industrial electric rates are so low that several aluminum smelters have moved to the island to take advantage of them.

Geothermal heat is provided to most households through district heating systems harnessing both low-temperature resources and waste heat from high-temperature geothermal electric plants.  In 2014, the costs for most residents ranged from below-average to average U.S. heating fuel prices.21

Iceland’s renewable electricity potential is 2 to 3 times its current use, with so much available that the UK and Western European counties are considering importing some of it through a proposed “IceLink” high-voltage DC line under the sea.22,23

Other Countries

Virtually all other countries that have a large percentage of their electricity coming from renewable energy rely on dispatchable power to accomplish this.24  Some notable examples are below.

OTHER COUNTRIES WITH HIGH PERCENTAGES OF RENEWABLE ELECTRICITY

Country

Percent Renewable

Type of Renewable

Austria

78%

66% Hydro; 7% Biomass; 4% Wind

Brazil

84%

76% Hydro; 7% Biomass; 1% Wind

New Zealand

74%

54% Hydro; 14% Geothermal;

1% Biomass; 5% Wind

Paraguay

100%

100% Hydro

Germany

Germany is not at the forefront of world countries in terms of absolute percentages of renewable electricity on its grid.  In 2015, it obtained 35% of its electric power from renewables; 22% of total electricity was from intermittent wind and solar power.  However, in many respects it has led the world with its Energiewende (“energy transition”) policies for a gradual conversion of all sectors of its energy use (including electricity, heating, industry, and transportation).  The country intends to both reduce its overall energy consumption and to convert its consumption to renewable energy for most of the balance.

The Energiewende had its roots in the Oil Crises price shocks of the 1970s and the antinuclear movement during the same time period, which was exacerbated by alarm many Germans experienced by the meltdown of the Chernobyl nuclear plant in 1986.   

The Energiewende had its roots in the Oil Crises price shocks and the antinuclear movement during the 1970s. This anti-nuclear protest took place in Bonn on October 14, 1979.
Photo: Hans Weingartz

 

Environmental protection is the largest motivation for this direction towards renewables; other important goals include enhancing national security and improving the economy.

Much has been written to both praise and lambaste this vanguard effort.  There is much to learn from Germany’s programs about what to do, and not to do, in advancing a renewable electric system in other countries.

Positive Effects

1. Single-Mindedly Lowered the World Cost of Renewable Energy – In 1991, an electric tariff went into effect that guaranteed a 20-year price to reward investment in renewable energy.  The price could be adjusted downward every year for new investments in that year, but would be kept in place for investments already made.  These tariffs were large enough to prompt more renewable energy investment in Germany than any other country.  From 1998 to 2004, between 25 and 46% of all wind capacity in the world each year was built there.25  From 2001 to 2012, between 25% and 68% of all solar PV capacity in the world each year was installed there, despite a cold and cloudy climate more resembling Alaska than Texas.26

The tariff created an anchor market that launched a learning curve that has reduced the cost of wind and solar energy to the point where it is today.   Had it not been for Energiewende, worldwide development of these renewable sources would have easily been delayed for several years (at a minimum).

In 1997, there were 2,089 MW of wind power in Germany.27  (There was so little wind capacity in that era that even this small amount was over a quarter of all the wind generation in the world.)  By 2015, Germany had over 45,000 MW of wind installed.28  In 1996, there were only 11 MW of solar power in the entire country; in 2015, there were 39,698 MW.29

Graph of percentage of world PV power installed in Germany

2. Environmental Protection – Germany is attempting to phase-out all nuclear power stations by 2022 and is intending to achieve an 80% reduction in fossil fuel use (including but not limited to electric generation) by 2050 with energy efficiency measures and renewable energy sources.30  The risk of nuclear accidents, nuclear waste disposal, and the need to drastically reduce greenhouse gases and emissions from fossil fuels are the biggest motivations.

3. Democratization of Grid Ownership – Most large German renewable energy systems are owned by cooperatives or municipal utilities, not large companies.  It is possible for a wind or solar farm to have hundreds of local investors, in contrast to the dominant model in the U.S., which relies on national or international corporations to build and finance the equipment.  While it is possible for large utilities to participate in Germany’s renewable tariff system, as of 2012, only 5% of renewable electric generation was owned by them, while almost half was owned by citizens, investment pools open to citizens, and farmers.31  One of the reasons is a higher interest rate for these corporations, but another is lack of motivation to pursue a new business model.

Municipalization of German utilities is also a trend, partially driven by environmental concerns about large corporations’ ownership of nuclear and coal plants and their seeming lackluster commitment to alternatives.  Since 2007, over 60 municipal utilities have been formed, with 170 communities attempting to purchase at least some part of the grid that serves them.32  In 2013, Hamburg, the country’s second largest city (population 1.8 million), held a successful referendum to authorize the purchase of two privately-owned utilities that served it.33

4. National Security Improved – Russia is the largest single provider of natural gas in Europe, and it wields the continent’s import dependency as a weapon of influence and political pressure.  In 2013, Germany imported 88% of the gas that it used, with 39% of these imports from Russia.34  Though most of this is used for heating, about 5% of Germany’s electricity is produced with this fuel.  In 2013, Germany also imported 97% of its oil, 87% of its hard coal, and 100% of its uranium.35  Reducing these imported fuels enhances national security while strengthening its balance of trade.

5. Employment – About 80,000 direct jobs had been created to install or service renewable energy.  (This is net of jobs lost in conventional energy production.)  This is expected to grow to between 100,000 and 150,000 in the 2020 to 2030 time period.  In 2013, Germany exported about 2/3 of its manufacturing output of solar cells and wind generators.

Negative Effects

1. Continued Reliance on Coal – Between 2013 and 2016, the country obtained between 40 and 45% of its energy from coal, despite a growing percentage of renewables in the mix.36  There are at least 4 reasons for this, some more palatable for environmentalists than others.

First, since utilities are obligated to purchase renewable electricity whenever it is available (with the exception of threats to grid integrity, such as too much power flowing at once), coal plants have become the first resort for spinning reserve to maintain a steady flow of power.  These plants are more quickly dispatched than nuclear plants.  Gas plants, while highly efficient, less polluting, and more quickly able to ramp up and down, have much higher fuel costs than in North America.

Second, due to Germany’s national policy of nuclear phase-out for safety reasons, which has already retired some of the reactor fleet and will retire the rest by 2022, there is a shortage of baseload power.  In the short-term, this is likely to grow (the safety of coal plants themselves not withstanding).37

Germany’s government began the phase-out of nuclear power in 2006.  The plants began retiring as they aged, with no nuclear replacement.  However, this phase-out was accelerated in 2011 following the meltdown at the Japanese Fukushima plant.38  By 2015, nuclear generation fell to about half of its level in 2006.

The third reason is that a lot of German coal power is exported to other countries to make up for lost corporate utility sales to renewables in their own country.

And fourth, lignite (soft coal) mining still supports many jobs, which will be lost when these plants stop operating.

2. No Stable Profits for Fossil Fuel Plants – Due to the preference for renewable energy, coal and gas plants run less often, and do not make as much money.  This makes it hard for them to make a profit, even though the system would crash without their contribution.

3. No Stable Profits for Storage – It should be noted that coal plants are not the only conventional electric facilities having financial problems because of the renewable dispatch priority.  Germany has several “pumped hydroelectric” facilities that can store intermittent renewable energy or cheap nighttime power by pumping water in a lower reservoir up to a higher one to rerun the fluid through a hydroelectric generator.  It is a relatively economic way to store large amounts of power, but Germany has no tariff that guarantees that these facilities will earn a profit.

4. High Rates/Energy Poverty – Germany has one of the highest residential electric rates in the world.39  In 2013, it was 38¢/kwh, compared to 11¢/kwh in Austin and 12¢/kwh in the U.S.  Germany’s cost was only slightly lower than Denmark’s.  German rates in 2015 were twice what they were in 2000,with about 20-25% of the cost attributed to renewable energy.  This pain is particularly acute among the nation’s poor.

This surcharge may go down over time as older 20-year tariffs for higher cost wind and solar power are replaced with newer, less expensive contracts resulting from economies of scale.  However, the cost mitigating effects of these newer contracts may be reversed by purchases of offshore wind power, which is much more expensive than land-based sites.

These higher costs do have the effect of driving down consumption, another goal of Energiewende.

5. Renewable Surcharge Exemption to Large Commercial Customers – Large industrial customers have been specifically exempted from the renewable energy surcharge.  This was intended to allow domestic, energy-intensive industries to better compete on the world market.  Over time, however, the exemption has been expanded to large customers where high-cost electricity is not critical to competitiveness.

6. Need for Transmission Upgrades – The country is in need of transmission and distribution upgrades, much of it driven by expanding renewable energy.  If this is not done, renewable electric generation will increase the amount of spilled (wasted) power that cannot be utilized.  For instance, offshore wind farms built in a sparsely populated northern part of the country cannot sell their power to the southern part without new lines.  While this is not a technical problem, it is an expensive one, with one estimate of 8.2 billion Euros.

7. Expensive Offshore Wind – In many parts of the world, building a wind plant offshore can increase electric production per wind turbine because of stronger and more consistent resources.  However, this comes at a hefty premium, currently about 175% more than land-based sites.40  By 2015, 4,608 MW of German wind power were commissioned, under construction, or approved in the Baltic and North Seas, with another 6,680 MW planned41.  It is expected that the price will fall with more completions, but this learning curve will probably be costly.

Offshore wind farm in Baltic Sea off German coast
Offshore wind farm in Baltic Sea off German coast
Photo: Walt Musial/National Renewable Energy Laboratory

*******

Again, the Energiewende is a comprehensive effort that deals with all sectors of Germany’s energy use.  The focus of this article is about electric generation; it has not discussed building codes, transportation, and heating to any degree.  These are essential in any long-range plan for clean energy.  Electricity, however, is a good starting point given Austin’s municipal ownership of its utility and its decades-long commitment to efficiency and renewable power.

The current limits of intermittent renewable energy technology and costs constrain their use to a fraction of total power needs.  Moreover, even if energy efficiency and smart grid strategies are added to intermittent renewables, and employed at an unprecedented level, it will still take large amounts of dispatchable power to maintain the system.

Another story discusses dispatchable renewable technologies in detail, including those that work today, and some more appropriate technologies for Texas climate and geology that might work in the future.

The reader is cautioned not to read too much into futuristic technologies.  With enough R&D money, time, and (corrected) mistakes, some of them may eventually become viable solutions.  But new technology development is not entitled to certainty.  If it were, the stark problems associated with the conventional power system would already be solved.

Continue to Challenges to Clean Energy, Part 2: The Limits of Technology ->

Endnotes

U.S. Energy Information Administration hereafter referred to as EIA.

1 EIA, “Fewer wind curtailments and negative power prices seen in Texas after major grid expansion,” June 24, 2014.  Online at www.eia.gov/todayinenergy/detail.php?id=16831

2 Much of this information comes from Jim Kelly, KIUC public information, in phone interview on April 6, 2016.  This was supplemented with interviews from Brad Rockwell, KIUC power supply manager, on June 15, 2016, and Beth Tokioka, KIUC public information, on June 28, 2017.

3 KIUC Web site, accessed April 6, 2016.

4 Wholesale costs are then added to the costs of maintaining the grid, (which is the price the consumer sees).  ERCOT Real time average price in 2015 from ERCOT, 2015 State of the Grid Report, p. 37.

5 Most/all statistics on Denmark’s electric use, unless otherwise noted, were derived from Energinet.dk (Danish Independent Systems Operator), “RE generation,” Environmental Reporting, Climate and the Environment, Denmark, 2015.  Online at http://www.energinet.dk/EN/KLIMA-OG-MILJOE/Miljoerapportering/VE-produktion/Sider/default.aspx

6 Ibid.

7 Marcy, Cara and Alexander Metelitsa, “European residential electricity prices increasing faster than prices in United States,” U.S. Energy Information Administration, Washington, DC, November 18, 2014.  Online at https://www.eia.gov/todayinenergy/detail.php?id=18851

8 Hill, A.L., et al., “Modelling Recycling Targets: Achieving a 50% Recycling Rate for Household Waste in Denmark,” Journal of Environmental Protection, 5, p. 628.  Online at http://dx.doi.org/10.4236/jep.2014.57064

9 “Imported waste worth €147m to Denmark, “ ENDS Waste & Bioenergy, November 26, 2014.  Online at http://www.endswasteandbioenergy.com/article/1323930/imported-waste-worth-%E2%82%AC147m-denmark

10 Flach, Bob, The Market for Wood Pellets in Denmark, USDA Foreign Agricultural Service, GAIN Report #: NL3036, November 5, 2013, p. 2.

11 Ibid.

12 Neslen, Arthur, “Wind power generates 140% of Denmark’s electricity demand,” The Guardian, July 10, 2015.

13 Mead, Samantha, Monthly Electricity Statistics, Data Archives, Paris, France: International Energy Agency, December 2015.  Online at iea.org/statistics/monthlystatistics/monthlyelectricitystatistics/

14 EIA, “Net generation for Iowa, annual” and “Retail sales of electricity, annual,” Electricity Data Browser, Washington, DC, accessed 2/9/17.  Online at http://www.eia.gov/electricity/data/browser/

15 Ibid., “Average retail price of electricity, annual.”

16 Statistics Norway, Electricity Prices, Q4, 2015, Oslo, Norway.  Online at ssb.no/en/energi-og-industri/statistikker/elkraftpris/kvartal/2016-02-25

17 EIA International Statistics.  Of 10 Twh generated in 2012, 72% came from hydroelectricity, 14% from geothermal, and 2% from biomass.

18 Arias, L., “Construction of Central America’s biggest hydroelectric dam is nearly finished in Costa Rica,” The Tico Times, December 19, 2014.  Online at http://ticotimes.net/2014/12/19/construction-of-central-americas-biggest-hydroelectric-dam-is-nearly-finished-in-costa-rica

19 Rates rose to 21¢ after the first 200 kwh.

20  Loftsdóttir, Ágústa, Energy Statistics in Iceland 2014, Reykjavik, Iceland: Orkustofnun National Energy Authority, April 2015, PDF p. 4.  Online at http://os.is/gogn/os-onnur-rit/orkutolur_2014-enska.pdf

21 Ibid., PDF p. 6.

22 Askja Energy, “The Energy Sector,” accessed 1/21/17.  Online at  https://askjaenergy.com/iceland-introduction/iceland-energy-sector/

23 Landsvirkjun (National Power Company of Iceland), Submarine Cable to Europe, Reykjavík: Iceland, accessed 1/21/17.  Online at http://landsvirkjun.com/company/mediacentre/contactus

24 EIA, International Energy Statistics, 2012.

25 British Petroleum, BP Statistical Review of World Energy, “Wind capacity,” June 2015.  Online at http://www.bp.com/statisticalreview

26 Ibid., “Solar capacity.”

27 Ibid.

28 British Petroleum, BP Statistical Review of World Energy, “Wind capacity,” June 2016.  Online at http://www.bp.com/statisticalreview

29 Ibid., “Solar capacity” and Note 26.

30 Morris. Craig and Martin Pehnt, Energy Transition,The German Energiewende, Berlin, Germany: Heinrich Böll Foundation, July 2015, p. 85.

Online at http://www.energytransition.de

31 Bayer, Edith, Report on the German power system, Berlin, Germany: Agora Energiewende, p. 9.

32 Rinehart, Ian and Charleen Fei, Taking Back the Grid: Municipalization Efforts in Hamburg, Germany and Boulder, Colorado, Washington, DC: Heinrich Böll Stiftung, June 2014, p. VI.

33 Ibid.

34 Federal Institute for Geosciences and Energy Resources, Energy Study 2014, Hannover, Germany, 2014, p. 24.  Online at http://www.bgr.bund.de/EN/Themen/Energie/Downloads/energiestudie_2014_en.pdf?__blob=publicationFile&v=3

35 Ibid., pp. 21, 27, 29.

36 AG Energiebilanzen, “Electricity generation by energy sources (electricity mix) from 1990 to 2016 (in TWh) Germany as a whole,” Facts and Figures, accessed 1/21/17.  Online at http://www.ag-energiebilanzen.de/#20161216_brd_stromerzeugung1990-2016

37 Op cit., Morris, Craig, p. 14.

38 Op cit., Morris, Craig, p. 35.

39 Note 7.

40 Lazard’s Levelized Cost of Energy Analysis, Version 8.0, p. 3

41 German Wind Energy Association, Yearbook Wind Energy 2015, Berlin, Germany, 2015, p. 43.