Challenges Facing Grid Integration of Renewable Energy in the GCC Region
Banks_Capstone_Report
1. Agave Cultivation in the Southwestern
United States: A Model-Based Summary
of Energy Output and Greenhouse Gas
Offsets
Principal Author:
Aaron Banks
Chapter II Written in Conjunction with:
Millard McElwee
As Members of:
The American Jobs Project
Technology Roadmaps
Advised by:
Dr. Donald Wroblewski
Dr. Ian Holmes
May 10, 2016
3. Chapter 1
Technical Contribution
1.1 Introduction
The American Jobs Project (AJP) aims to provide state-specific recommen-
dations that will lead to growth in the advanced energy and manufacturing
sectors across the country. A large part of this mission involves analyzing per-
tinent technologies for viability, both in an abstract sense, and with the policy
and economic landscapes for regions in mind. The engineers working with AJP,
split into the two distinct sections outlined in Figure 1.1, perform the majority
of this analysis.
The two supply chain teams focus on the industry conditions in individual
states, determining which industries the state has an effective infrastructure
in and where in these industries they can improve. The technology roadmaps
team, which Millard McElwee and I make up, look at technologies in a general
sense, mapping out what pieces need to be in place in order to create an effective
economic cluster.
With analysis in both of these areas complete, we can provide effective rec-
2
4. ommendations on where effective investments can be made. And with this strat-
egy in mind, I have analyzed the potential, both currently and in the future, of
agave as a biofuel crop in the American Southwest.
1.1.1 Problem Statement
Figure 1.1: Diagram of the AJP
work breakdown structure. The re-
search of the Technology Roadmaps
team is represented by the right
side, while both Supply Chain
teams are represented by the left.
In order to have a completely renewable
energy system, we need to expand our
technologies to include methods of pro-
ducing and delivering energy in the gaps
formed by the intermittency issues in so-
lar and wind power[4]. As is shown in
Figure 1.2, otherwise known as the duck
curve, as energy generated from solar and
wind increases over time, less energy is
needed from fossil fuels during the day,
but demand at night increases slightly,
leaving us with a daily period where cur-
rent sources of renewable energy cannot meet demand[8].
To counter this issue, we need two solutions: that of large scale energy
storage and carbon neutral sources of energy that can be used to fill gaps in
energy production[4]. Biofuels can provide an answer to the second of those
requirements, as the plants used to make fuels store energy from the sun in
the form of sugar or cellulose, which can then be converted into ethanol or
other fuels. In addition, if used in conjunction with carbon capture technology,
biofuels have the potential to become a carbon negative energy source[23].
Unfortunately, the recent downturn in the price of oil, largely due to the
shale gas and oil boom, has caused the profitability of biofuels to plummet[25].
3
5. Figure 1.2: Typical load on fossil fuel energy producers in California[8], with
projected changes in load included by year. Note the significant increase in load
that occurs from hours 17 to 19.
Therefore, those in the industry have had to take a hard look at their business
model, with many companies choosing to become more flexible with the products
they can produce and the feedstocks they use, such that they can still make a
profit in adverse market conditions[24].
One feedstock that may be of use in these conditions is that of agave. Cul-
tivated for over a millennium to produce tequila, it has recently been proposed
as a biofuel crop due to its low water usage, high sugar content and ability to
be grown on marginal lands[19]. Water usage is an especially key parameter, as
the southwest, specifically California, is in the midst of a historic drought[13].
A high sugar yield allows for the utilization of a cheaper and more mature tech-
nology than cellulosic or even starch conversion[7], needed to produce ethanol
from corn.
The ability to be grown on marginal lands minimizes the risk of agave pro-
duction interfering with our food supply, which can produce a variety of unin-
4
6. Figure 1.3: Illustration of CAM photosynthesis[26]. Note the diurnal cycle of
carbon uptake at night and utilization during the day. This allows for an eighty
percent reduction in water usage[3].
tended results. For example, the indirect land use changes caused by increased
corn production during the advent of corn ethanol has been theorized to cause
significant amounts of deforestation in the Amazon[14]. This loss of terrestrial
carbon storage is a major reason why some have estimated corn ethanol to con-
tribute more to our carbon footprint than fossil fuels, per gallon of gas equivalent
(GGE)[10].
1.1.2 Agave Metabolism
Agave, along with a number of other plant species adapted to arid environments,
employs crassulacean acid metabolism (CAM) to perform photosynthesis[26].
Plants using CAM are able to grow using roughly twenty percent of the wa-
ter that plants using a traditional metabolism would need to grow[3]. This is
largely because the plant is able to uptake carbon dioxide at night, allowing it
to leave its stomata closed during the day, significantly reducing water lost due
5
7. to evaporation. As is outlined in Figure 1.3, the carbon dioxide is converted to
malate, a four-carbon molecule, and stored in the vacuole (the lilac oval in the
figure) until daylight[6].
Once sunlight is available, the stomata are closed and the malate is decar-
boxylated to form CO2 and a three-carbon acid. The C3 acid is converted to
starch through glycolysis and then cycled back through to form malate during
nocturnal carbon uptake. The carbon dioxide is put into the Calvin Cycle,
where it is eventually converted to a more permanent form of carbohydrate
storage, such as glucose or cellulose. While this process has a higher energy
requirement due to the increased number of chemical conversions necessary, the
energy requirements are often offset by the higher solar potential of the areas
in which CAM photosynthesis plants grow[15].
1.2 Methods
1.2.1 Growth Scenarios
To fully analyze the impact that agave growth could have on an area as large
as the American Southwest, multiple growth scenarios must be considered. The
first scenario that I have chosen to model is that of agave being simply grown
on marginal, unused land. The key parameters to be modified in this scenario
are that of soil nutrients, annual precipitation, and distance from the field to
the processing facilities.
The next situation to be modeled is that of agave and solar panel co-location.
The primary advantage of this scenario stems from the water currently used to
clear and prevent dust buildup on solar panels[22], which can reduce efficiency
by up to 35%[17]. Therefore, agave could be grown in the gaps between panels,
using only the water currently sprayed on panels and the dirt beneath them.
6
8. Third, I will model the growth of agave on fields left fallow, a relatively new
phenomena, found largely in California. Many farms managers in the central
valley have found that they can make more money by selling their water rights to
southern California rather than using them to grow crops[18]. This has resulted
in the loss of jobs for many laborers in the central valley[11], adding to the
tensions felt as a result of the multi-year drought in the region. Therefore, by
growing agave rather than water intensive crops such as oranges or almonds,
the operators can still sell their water rights while producing a valuable crop
and providing jobs to the local economy.
1.2.2 Life Cycle Analysis
To quantify the environmental impact of agave cultivation in these three sce-
narios, mathematical models highlighting to key parameters will be employed.
By taking the important factors for each scenario listed above, one can create
a model that can calculate the greenhouse gas (GHG) offsets and net energy
of each scenario, with a variety of conditions. The equations used to calculate
outputs for agave growth alone are listed below and are based off of the equa-
tions used by Ravi et al[22]; in addition, many of the parameter values used for
each scenario will come from this paper. Expanded equations can be found in
the appendix.
1.2.3 Uncertainty and Sensitivity Analysis
To account for the fact that this analysis is being performed over an area of land
that numbers in the millions of square miles, an uncertainty analysis known as
Latin Hypercube Sampling (LHS) will be used to show the range of possibilities
in each scenario. Using a defined range for each parameter, random number
selection will be employed through 1,000 simulations, with the outputs shown.
7
9. Table 1.1: Parameter values that were varied in the general growth scenario,
along with their sigma values, relative to both net energy and GHG offsets.
Parameter Range of Values Energy σ GHG σ
Nitrogen Usage 480-720 kg/ha -0.00796 -0.0541
P2O5 Usage 73.2-109.8 kg/ha -0.0485 -0.0489
K2O Usage 231.4-347.0 kg/ha -0.00871 -0.0707
Herbicide Usage 12.0-18.0 kg/ha -0.0749 -0.0243
Pesticide Usage 0.864-1.30 kg/ha -0.0464 -0.0705
Distance 160-240 km -0.0929 -0.00828
Total Agave 225-345 Mg/ha 0.653 0.750
Sugar Content 13.2-19.6 % by mass 0.681 0.669
Ethanol Yield 465-698 L/Mg Sugar 0.758 0.735
All simulations will be performed using Mathematica.
In addition to uncertainty analyses, sensitivity analyses will be performed
to calculate which parameters have the greatest effect on the outputs of each
scenario. Specifically, a partial rank correlation coefficient (PRCC) was deter-
mined for each variable. A value, , between -1 and 1 will be calculated, with
a value of 1 indicating a perfect positive correlation and a value of -1 a perfect
negative correlation. A value of 0 indicates no connection whatsoever to the
output variable. This information will then be used to identify which parts of
the agave plant could be genetically modified to provide the greatest benefits,
both economically and environmentally.
1.3 Results
Before specific situations were considered, a general model of agave growth was
used to determine the relative importance of parameter values. To provide
a degree of uniformity, each parameter was varied + 20% from its respective
literature value, and calculations were performed for 1,000 sets of randomly
sampled values. Agave yield was the baseline value from Ravi et al[22], which
equates to 350 mm of annual precipitation. A range of values for every parameter
8
10. Table 1.2: Key parameters from the solar co-location scenario, along with sigma
values.
Parameter Values Energy σ GHG σ
Total Agave 45-69 Mg/ha 0.661 0.715
Sugar Content Unchanged 0.703 0.635
Ethanol Yield Unchanged 0.762 0.674
varied in this scenario, along with sigma values for net energy and GHG offsets,
can be found in Table 1.1. Usage rates of agrochemicals, along with the distance
from the field to the processing facility, all had small negative correlations with
both net energy of the system and GHG offsets. In contrast, Agave yield, sugar
content and ethanol yield from sugar all had strong positive correlations with
both outcomes. The mean net energy from these simulations was 353 GJ/ha,
with 25 and 75% quantile values of 282 and 416 GJ/ha, respectively. The mean
GHG offset was 104 Mg CO2 equivalent per hectare, with 25 and 75% quantile
values of 87 and 119 Mg CO2 e/ha, respectively.
1.3.1 Solar Co-Location
As was discussed in Ravi et al[22], the energy return and GHG offset of agave
per meter is significantly lower than that of solar panels, specifically 353 to
2405 GJ/ha/yr and 104 to 464 CO2 e/ha. Therefore, the density of panels
in this scenario will not be altered. Rather, the situation simulated is one in
which the agave is planted in the existing spaces between panels, amounting to
a density and yield of 20% of a situation in which agave is grown alone. The
annual precipitation used in this model is 250 mm, in line with that of San
Bernardino, CA, augmented with 100 mm precipitation equivalent from the
existing irrigation used to clean the panels and prevent dust buildup, resulting
in a mean agave yield of 57 Mg/ha, which was then varied by +20%.
Over 1,000 simulations, mean energy return was 18.1 GJ/ha (0.18-32.3 1st
9
11. Table 1.3: Key parameters from the fallow fields scenario, along with sigma
values.
Parameter Values Energy σ GHG σ
Total Agave 100-300 Mg/ha 0.918 0.868
Sugar Content Unchanged 0.592 0.645
Ethanol Yield Unchanged 0.733 0.700
and 3rd quartiles), and mean GHG offset was 13.2 CO2 e/ha (10.1-15.8 1st and
3rd quartiles). In addition, the sigma values for usage rates and distance in
both models all remained between 0 and -0.1, while the sigma values for agave
yield, sugar content and ethanol yield had the same relative values as they did
in the general growth scenario. While the third quartiles of both outcomes were
less than 20% of the full-scale scenario, they both were positive in the first
quartile, indicating a strong likelihood that the addition of agave cultivation
could provide a boost, however small, to the water-use efficiency of solar power
installations in arid environments.
1.3.2 Fallow Fields
For modeling growth on fallow fields, average precipitation values were taken for
California’s San Joaquin Valley, between 127 and 406 mm per year[11], amount-
ing to annual agave yields between 100 and 300 Mg/ha. These precipitation
values represent water addition from rain alone, i.e. no irrigation used, allowing
the owner of the farm to continue selling the water rights to municipalities in
Southern California. All other parameters remained constant from the general
growth scenario.
The net energy production for this scenario was 229 GJ/ha (145-301), and
GHG offset was 70 Mg CO2 e/ha (50-88). Once again, sigma values for usage
rates and distance in both models remained between 0 and -0.1. Sugar content
and ethanol yield had similar sigma values to previous situations, but the sigma
10
12. Figure 1.4: Two graphs illustrating how sigma values of parameters relate to
the final outputs of the system.
(a) Graph displaying the relationship
between energy production and agave
yield in the fallow fields scenario. Note
the positive correlation between the
two data sets, reflecting the sigma
value of 0.918 for agave yield.
(b) In the marginal lands scenario, dis-
tance showed a significant negative cor-
relation with net energy. To find the
point at which energy reached zero
( 800 km), the maximum distance was
increased to 1,000 km.
values for agave yield were significantly higher in both models, with a value of
0.918 for net energy and 0.938 for GHG offset. This indicates importance in
the location of cultivation, as the level of natural precipitation will have a large
degree of influence over both the net energy produced and greenhouse gases
offset.
1.3.3 Marginal Land
To model agave cultivation on marginal land, three parameter changes were
made: first, lowering the range of agave yield to 99-198 Mg/ha, or the low
growth scenario in Ravi et al[22]. and half of that value, in order to account
for extremely low rainfall. Second, the distance from the field to the processing
facility was set to a range of 300-500 km; next, agrochemical usage (excluding
herbicides and pesticides) was increased by 25% to account for poor soil.
As a result, net energy was 104 GJ/ha (66-138) and GHG offset was 45 Mg
CO2 e/ha (34-54). In this scenario, agrochemical usage sigma values remained
between 0 and -0.1, but sigma values with respect to net energy and GHG offset
11
13. Table 1.4: Key parameters from the marginal lands scenario, along with sigma
values.
Parameter Values Energy σ GHG σ
Total Agave 99-198 Mg/ha 0.787 0.868
Sugar Content Unchanged 0.497 0.645
Ethanol Yield Unchanged 0.751 0.700
Distance 300-500 km -0.238 -0.126
Agrochem Usage 125% of original 0 to -0.1 0 to -0.1
for distance to processing facilities were -0.238 and -0.126, indicating a modest
negative correlation with both outcomes. Total agave yield once again had the
highest sigma values, followed by ethanol yield in both models. Sugar content,
despite its potential to increase the efficiency of transport to processing facilities,
had a significantly lower sigma value for the net energy model (0.497 compared
to 0.681 in the general scenario).
1.4 Conclusion
The models presented here demonstrate that growing agave on unused or un-
derused land, with little to no additional water use, can result in a positive
net energy and offset greenhouse gas emissions. While this would not be the
most beneficial use of the land by a calculation of gross energy or GHG offsets
(solar power has a 10-fold advantage in both metrics), the over-utilization of
solar power and loss of jobs in the central valley allow for agave cultivation to
provide valuable benefits to the region. In addition, other CAM plant, such as
guayule, which produces rubber, could be grown to produce products with a
small, or even negative, carbon footprint.
Future research into this topic should focus on the exact relationship between
annual precipitation and agave yield, as the models in this paper employed
estimates (based on historic data) of the correlation between the two values,
12
14. rather than a concrete mathematical function. In addition, attempts to modify
the genetic structure of agave to produce a more water efficient crop or one with
a higher sugar content would be well served by the strong correlations between
those two factors and net energy, as well as GHG offsets.
13
15. Chapter 2
Project Context
2.1 Problem Statement
Two problems stand tall on America’s horizon: environmental mismanagement
and economic inequality. Both of these issues have sprung from an inherent
tendency of humans to become complacent with their resources, to stick with
that which is proven despite opportunities for growth. The American Jobs
Project looks to alleviate these issues with one endeavor. Through the release
of state-specific reports, we will attempt to convince several states that adopt-
ing advanced energy technologies is in their economic and environmental best
interest.
Over the past two decades, the United States has shown an upward trend in
greenhouse gas emissions. As shown in Figure 2.1, the U.S. has increased emis-
sions by more than 6 percent from 1990-2013 with an average annual increase
of 0.3 percent. Although strides have been made to cap emissions, this alone is
not sufficient to prevent significant damage to the environment. Jobs will need
to be created that not only reduce emissions but remove the excess carbon from
14
16. Figure 2.1: Graph of GHG emissions in the US from 1990-2014[9].
the atmosphere. We cannot wait for slowly moving energy technology if the
crises can be averted through alternative measures.
Jobs in America are being replaced with faster and cheaper technology or
outsourced to countries with almost non existent profit margins. The manu-
facturing industry has been impacted drastically over the past 30 years. Man-
ufacturing jobs have decreased by almost 50 percent as shown in Figure 2.2.
This industry will soon be nonexistent if it continues along its current rate of
replacing jobs with temporary solutions. Engineers must create opportunities
for well paying sustainable jobs in the advanced energy sector.
Regardless of political standing, the vast majority of Americans disapprove
of our national representatives[5]. One of the key drivers of our inaction is
the current state of Congress. Years of partisan fighting has resulted in two
legislative bodies that have recently struggled to pass the most fundamental of
bills, a budget. Furthermore, the American Society of Civil Engineers (ASCE)
15
17. Figure 2.2: Graph of employment share by industry in the US, both in 1983 and
2012[27]. Note the significant decrease in manufacturing share of employment.
has rated America’s infrastructure a D+[2]. Roads and various transit facilities
are in need of major upgrades if reliable and safe transportation is a priority. A
decaying infrastructure and lack of action are indicators of Congress’s need for
assistance in addressing these issues.
Advances in computing and energy storage coupled with environmental and
policy reforms have spurred growth and interest in developing smart infrastruc-
tures that can automate systems to balance the supply and demand of electricity.
The electrical grid was originally built in the 1890s and now is also in need of
vast repairs. The main challenge this poses is how to shift from a producer con-
trolled network to a more interactive consumer network. Jobs must be created
that will develop a more responsive and resilient grid. The role of the smart
grid is not to replace a specific energy technology but to find the solution that
integrates multiple energy sources for maximum efficiency.
16
18. 2.2 Potential Solutions
Despite the problems facing us, there is reason for hope. This past December,
196 nations met in Paris to sign a historic agreement to limit emissions of carbon
dioxide. While it held no legal power over the emission reduction commitments
made by individual countries (due in large part to the opposition of our leg-
islative bodies), it signals a global consensus that fighting climate change is a
major priority. For our project, this shows that the US will not be alone in this
fight; in fact, the world is watching us closely, hoping we can use our influence
in the world to avert the crises that climate change brings.
In this phase of the AJP, some of the selected states are currently suing
the Environmental Protection Agency (EPA) over the Clean Power Plan which
calls for a 32 percent carbon emission reduction by 2030. The policy focuses
on capping emissions from coal power plants and increasing dependence on
renewables and energy conservation.
With governmental mandates requiring companies to become more energy
efficient, it will be advantageous for states to create jobs in the advanced energy
sector. The Presidents Climate Action Plan outlines the requirement of auto-
mobile manufacturers to increase average fuel efficiency of their fleet to 54.5
miles per gallon by 2025[21]. Through the use of advanced energy materials
such as carbon fiber, manufacturers can substantially reduce the weight of ve-
hicles. Weight and efficiency are inversely proportional; therefore, minimizing
the weight will drastically help reach the miles per gallon mandate. A study
conducted by the National Renewable Energy Laboratory (NREL) found that
the United States could produce 80% of its electricity through renewable energy
(wind, solar, biofuels, geothermal, and hydropower) by 2050[16].
Before our solutions ever end up on the desk of the key stakeholders in our
target states, they will have been thoroughly tested within our target market.
17
19. Figure 2.3: Graph comparing wind development in Texas versus other Western
states[12].
Industry leaders, politicians, academics and many others will be called to ask
their opinions on our proposals. These will be crafted with our stakeholders
in mind. The Department of Energy (DOE) will host workshops where their
national labs, the Department of Commerce’s Manufacturing Extension Part-
nerships (MEPs), university affiliates, and small businesses can network.
2.3 Our Work
As members of the technology roadmap group, our aim is to work with tech-
nology, industry and policy in mind to craft targeted proposals for individ-
ual states while acknowledging the fundamental differences that exist between
states. Working with state specific goals and objectives allows us to create
mutually beneficial strategies. We will leverage our partnerships with governors
and other elected officials so that we can do the most good with the least amount
18
20. Figure 2.4: Chart demonstrating the size of several markets in which products
can be made from biomass[24]. Note that the circle sizes are not drawn to scale.
of government intervention.
In order to increase the likelihood of our recommendations being adopted,
we will be utilizing policy best practices from other states with similar political
leanings. For example, a Georgia representative who supports renewable energy
may not receive support from colleagues, so we craft our narrative with that
in mind, choosing to focus on how Texas has invested heavily in wind and
solar. This was largely brought on by Texas instituting a Renewable Portfolio
Standard, mandating that a certain amount of their power comes from renewable
sources. As a result, Texas now leads the country in wind generation, depicted
in Figure 2.3.
In addition to policy, we also look to industry for effective strategies to
provide solid employment. Recently, many biofuels companies have been forced
out of business due to the low price of oil. However, some companies, such as
REG Life Sciences, have been able to survive due to their flexible business model.
In addition to producing fuels, they’ve developed their technology to be able to
19
21. Figure 2.5: A graph illustrating the two major capital shortfalls that can occur
during technological development[20]. These gaps are most pronounced during
the production of new energy technologies.
make various products currently made from petroleum, such as fragrances and
detergents. Outlined in Figure 2.4, these products can be worth anywhere from
two to fifty times as much as fuels, allowing REG to remain viable despite an
unfavorable market.
The government plays a small, but important, role in the research phase of
a newly formed company. Although the governments investment is relatively
smaller than other entities, it takes on the most risk by investing first, as shown
in Figure 2.5. Many of the the energy technologies will be facing a valley
of death during commercialization, which we hope to help avoid by including
recommendations on financing programs in our reports, such as the tens millions
of dollars in grants given by Lee County, Florida and the DOE to Algenol, so
that it could build its facility in Fort Myers, Florida[1].
One necessary change is the restructuring of the patent process which places
barriers to entry for newcomers in the advanced energy sector. Today’s patent
process operates against progress which can set innovation back. The govern-
ment is given the task to distinguish between companies who have a genuine
20
22. interest in preserving intellectual property and those who are trolls (companies
that hold patents with the sole purpose to stifle innovation). We must find ways
to incentivize corporations to license patents for innovation purposes similar to
how NASA has offered licenses of patented technologies to start-ups from a
database of 1,200 of their best patents. Despite these challenges, we must per-
suade states to adopt the proposed technology roadmaps. The roadmaps will
provide political and economic incentives for states that allow them to meet
state mandates and decrease levels of greenhouse gases. As one of our primary
goals is to foster innovation, fixing the patent system would be highly beneficial
to us, if not part of our mission. We are members of the American Jobs Project
who are focused on creating right fit solutions to create sustainable well paying
jobs in the advanced energy sector.
21
24. Figure 3.1: Equations used in the life cycle analysis to calculate net energy for
each scenario.
Figure 3.2: Equations were used to calculate the GHG offsets of agave use in
each scenario.
23
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