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CUBA INFRASTRUCTURE CHALLENGE 2013 Student Participation Form

Team Name:

Acere! (Alternative Cuban Energy Research Engineers)

University:

University of Florida

Faculty Advisor:

Herbert A. Ingley,III ingley@ufl.edu

Does the team need an Industry Advisor to be assigned by the Challenge Committee? Yes NoX If the team already has an Industry Advisor, please enter his/her name in the box below:

Team Members:

# First

Name Last Name Degree/Major

Expected Graduation

Date E-mail address

1 Antonio Diaz Bachelors/Aerospace/Mechanical Engineer

2014 tony52892@ufl.edu

2 David Cabrera Bachelors/Aerospace/Mechanical Engineer

2013 Ablot08@gmail.com

3 Andreea Coman Bachelors/Chemical Engineer 2015 a.coman@ufl.edu

4 Juan Tanquero Bachelors/Materials Engineer 2014 jgtanq@gmail.com

Team Leader Contact Information:

Name Antonio Diaz

Phone 305 2818891

Address 4000 SW 23rd ST Gainesville Florida 32608 Apt:6-208

E-mail ony52892@ufl.edu

Project Title:

Analysis of Alternative Energy sources, storage and transmission for Cuban infrastructure

Project Abstract (150 words max):

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Becoming energy independent is one of the modern goals that cannot necessarily be met by traditional sources of energy and countries such as Cuba must expand its options with alternatives. The infrastructure that Cuba currently has is primarily based on inefficient oil fired thermoelectric plants with an average availability of 60%. Transmission of power is another issue with unreliable high voltage power lines that also have associated inefficiencies. This research would pursue an evaluation of alternative energy potential in Cuba and propose possible techniques of gathering this energy while meeting objectives that are reasonable in the real world scenario. A life cycle methodology will consider the impacts that any proposed machinery may have. This includes the design phase, the impacts on the surrounding environment during construction and use, costs including those for maintenance and operation, and the issues involved in disassembly and disposal of the product.

Tony Diaz- Team Leader and Design Feasibility

Andreea Coman- Introduction and Conclusion

David Cabrera- Human Environmental Impacts

Juan Gabriel Tanquero- Financial Analysis

Miguel Morales- Proofreading

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ANALYSIS OF ALTERNATIVE ENERGY SOURCES, STORAGE, AND

TRANSMISSION FOR CUBA’S INFRASTRUCTURE

Antonio Diaz, Andreea Coman, David Cabrera, and Juan Tanquero

Introduction

The efficient functioning and development of a country relies on a viable energy

infrastructure. In recent years, the national energy consumption in Cuba has skyrocketed,

emphasizing a great need for enhanced energy awareness to lower consumption and diversify the

country’s energy resources (Avila 2008). This diversification will serve to avoid similar

situations in the future, and provide a cost-effective remedy to the national energy crisis.

Cuba currently relies most heavily on energy derived from fossil fuels to generate

electricity, consuming 7.6 million tons of oil a year. This energy staple is reactionary, as the

supply is controlled by a changing group of countries. Prior to 1959, the Cuban Electric Power

Industry was controlled by foreign capital. In the early 1960’s, the nationalization process

resulted in an oil blockade, forcing Cuba to turn to the Soviet Union for imported oil. The

collapse of the Soviet Union in 1990 devastated Cuba’s economy; industry, agriculture, and

transport sectors nearly collapsed, and blackouts became a common issue (Avila 2008).

Venezuela now subsidizes Cuba’s fuel imports, although the possible depression of the crude oil

market and its political nature puts this relationship at risk. Imported fossil fuel energy presents a

stark lack of energy security. The infrastructure that Cuba currently has is primarily based on

inefficient oil fired thermoelectric plants with an average availability of 60%. Cuba’s current and

main method of storage is designating fossil fuel storage areas (Avila 2008).

The National Electricity System was built in the 1970s and 1980s, interconnecting the

island through a transmission grid operating at 220/110 kV. The distribution grid covers 95% of

the island. Old technology and poor design in the system causes large losses. Cuba’s economic

crisis halted proper maintenance of transmission and distribution lines; long power transfers and

illegal connections to the electricity grid generated additional electricity losses. When Cuba lost

Soviet support, it suffered a large decline in GDP as well as energy consumption per capita,

mostly in industry and construction consumption, while households did not curtail consumption.

Frequent power plant breakdowns in the early 21st century brought on a wave of severe blackouts

and civil unrest. In response, the Cuban Government developed the “Energy Revolution” to

emphasize energy conservation and expand the country’s capacity to generate power. (Belt 2007)

Between 1998 and 2004, the Cuban Government attempted to address the issue of

transmission of power by setting up a network of small fuel oil and diesel generating plants.

Since 2005, they have purchased several thousand small generators (2MW or higher). 40.5% of

Cuba’s energy is now distributed (Avila 2008). This decentralized system allows Cuba to better

handle interrupted transmission. It offers greater protection from hurricanes, and strengthens the

delicate energy system characteristic of a large generator by supplying several smaller

generators, whose individual failures would have a nearly negligible effect on the overall grid

(Belt 2007). Despite this improvement, Cuba is still in dire need of a sustainable, non-imported

energy source.

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Alternative Energy Sources

The use of centralized energy in Cuba has historically been impeding a successful energy

infrastructure. Massive plants created an unstable energy source, and entire regions suffered

mass blackouts upon the failure of an individual plant. Hence, this paper proposes an alternative

energy plan focusing on distributed generation. Cuba is actively seeking methods of expanding

energy sources, primarily in the wind, solar, biochemical, and hydro-power sectors.

Hydropower. Cuba has a strong history of using hydropower technology. Two

hydropower plants, the Pilotos in the Pinar del Río province (155 kW), and the Gauso in the

Guantánamo province (1.75 MW) date back to 1912 and 1917, respectively. While both power

plants are still operating, Cuba’s hydropower potential is relatively low (Avila 2008). Although

the total hydropower resource has been estimated to be 650 MW, protected and naturally

sensitive areas contain much of the unutilized potential, rendering hydropower largely

unavailable for development. The remaining resource subsides in mountainous areas and areas

with seasonal energy availability. This is suitable for small facilities and off-grid electricity

supply, but cannot be exploited for the main grid demand (Belt 2007).

Biochemical. Cuba also has experience in bioenergy, and the conversion of bagasse

(sugar cane residues) into thermal energy. The power produced feeds the sugar production

process and generates electricity to satisfy the demand of sugar cane mills. The surplus energy, if

any, is transmitted to the national grid. This component of domestic energy resource

development has declined since the economic crisis of the 1990s; a 39% decrease in average

sugarcane yield (57.5 ton/ha to 22.4 ton/ha in 2005), and a decline from 21% of cultivable land

to barely 5% (Belt 2007). In addition, most biomass power plants in operation have low boiler

and thermal-plant efficiencies, as a result of both the small size of most facilities and the

characteristics of the fuel. The plants are also expensive to construct, costing approximately

$2,000 per kilowatt of electricity to build, and having a thermal efficiency of 40%. (Cereijo

2010).

Solar. Cuba has great solar resources, but the use of solar photovoltaic energy is greatly

limited by start-up cost. The country has implemented 7098 photovoltaic systems (2.75 MW), to

bring electricity to areas of need such as rural schools, health clinics, and social centers. (Avila

2008). Thus, solar energy has been implemented largely for off-grid use. Although the use of

solar energy is a reliable source, the limitation of capital investment makes the resource cost

prohibitive for Cuba.

Wind. Recently the island has invested heavily in wind energy technology and has

received promising returns (Figure 1). Currently the installed capacity is spread amongst three

wind farms at Gibara (9,600kW, 12 turbines), Isla Turiguano (450kW, 2 turbines) and Los

Canarreos (1650 kW, 6 turbines) (Wind Energy Power for Cuba 2013).

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Figure 1. Growth of currently installed wind farms in Cuba (Wind Energy Power for Cuba

2013).

Evaluation of Alternatives

Given the many alternative sources of energy available to Cuba, the research team

decided to carry out a structured decision making process to compare choices and arrive at the

most suitable alternative energy source for Cuba. This process was carried out using design

matrices, which are an engineering tool used to organize thought processes and aid in an

unbiased selection. These decision matrices are presented in the Appendix. Each decision matrix

evaluates alternatives based on a number of objectives which are weighted by importance using a

factor, with the sum of the weighting factors totaling one. The team then provided a score to

quantify how well each alternative met a certain objective. These scores were based on research

and best engineering estimates.

Six decision matrices were employed in a funneling structure where choices were made

at a broad scale and slowly focused into a final energy source and technology. The first decision

matrix (Table 1A) analyzed the energy resources naturally available to Cuba, as well as the

reliability and known technology for those resources. Solar, wind, hydro, and chemical energy

resources were selected as potential candidates for the proposal.

The four decision matrices that follow analyze the separate technologies available within

the four previously chosen energy resources. Marine microalgae and marine macroalgae were

determined to be the most fitting source of chemical/biofuel energy for Cuba’s energy

infrastructure, given their high qualitative scores in every objective (Table 2A). For hydro

energy, following the analysis for feasibility of LIMPET, dam with generator, and tide capture

technologies, the LIMPET was selected as the ideal candidate for hydropower energy (Table

3A). Three different solar technologies were evaluated in Table 4A, photovoltaic, heliostat field,

and solar water heater, resulting in the selection of the solar water heater as the most reliable

technology. The wind energy technologies were evaluated in Table 5A, with the Magenn Air

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Rotor system (MARS) exceeding all other competitors in terms of initial investment, a high

deciding factor for Cuba, as well as modularity and adaptability. The final decision matrix (Table

6A) narrowed the selection to algae and flying wind turbine technologies. The most important

objectives were maintenance cost and initial investment, as Cuba’s economic situation is a large

limiting factor. The final decision was determined through an extensive pro-and-con analysis, see

comparison Tables 7A and 8A.

Design Proposal

Following the decision making process outlined in the previous section and detailed in

the Appendix, the proposed alternative energy design for this project is the flying wind turbine.

This design will allow for energy distribution throughout the grid, as the turbines can be installed

in a wide array throughout the country. The flying wind turbines are very mobile, and can be

easily moved to different locations to correspond to changing wind patterns. Mobility is also

useful in emergency deployment and disaster relief situations.

As part of the design, hydrogen storage is proposed to handle any excess electricity

generated. The production of hydrogen complements the flying wind turbine design by

facilitating the replacement of lost hydrogen, while also serving as a springboard for a hydrogen

economy. For example, hydrogen could be used to fuel vehicles. This paper presents flying wind

turbines combined with hydrogen energy storage as an advantageous and cost-effective solution

that is especially suitable for Cuba as a decentralized and adaptable means of gathering and

storing energy.

Design Feasibility

Cuba has plenty of wind resources available to increase its annual electric generation but

before it continues to greater and larger wind turbines, it can learn from countries that have

already taken this route. Many of the current turbines have a tower height of approximately 55-

60m and rotor diameter of 32m designed to access the wind resources available at 50m (Figure

2). These wind farms are strategically placed in areas proven to contain moderate to excellent

wind resources (Figures 3 and 4). The two or three blade horizontal axis wind turbine placed

upon a tubular tower design is a popularized and time tested approach to wind energy (Figures 6

and 7). However, wind energy like all forms of energy has both positive and negative aspects.

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Figure 2. With a conservative estimate of 5MW wind turbine per km2, Cuba can potentially

generate 21,405 MW using traditional tower based horizontal axis wind turbines (NREL Cuba

Wind Report 1995).

Figure 3. Holguin and Isla de la Juventud have great potential as a wind resource and both areas

are currently being exploited with wind turbines. (NREL Cuba Wind Report 1995).

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Figure 4. Map of wind power density (W/m2) at 50m. North offshore coast has large spans of

moderate wind and south of Guantanamo there is an area of good wind, however it is far

offshore. Moderate to excellent inland sources of wind can be found at Holguin and Isla de la

Juventud (U.S. Department of Energy 2004).

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Figure 6. Many configurations exist for gathering wind energy each with its own advantages

(Pritchard 2011).

Figure 7. Currently two-three bladed Horizontal axis wind turbines are the primary choice for

Cuba. However each configuration has its own benefits and since the coastal winds of Cuba can

change direction often, a Vertical axis turbine can be a better fit considering its ability to gather

wind from any direction without additional moving parts (Pritchard 2011).

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Design Considerations for Wind Turbines

To reach greater velocity and consistent winds, turbines are typically built with ever

increasing towers and large propeller diameter. This significantly increases initial capital

investment due to the larger stress forces acting on parts and additional loading on the tower

which would require a permanent foundation. For many locations, the process of establishing a

foundation to withstand the bending cycles and loads associated with larger turbines is not an

issue. However, considering Cuba’s four month long hurricane season wind turbines must be

either small and dismantled in the event of dangerous wind speeds or large and engineered to

withstand hurricane strength winds by a combination of stringent design criteria, variable pitch

blades and increased factor of safety with the tradeoff of increased costs. During the 2012

hurricane season the turbines recently installed in 2011 successfully survived the 180 kph winds

of hurricane Sandy demonstrating the potential of the technology. A critical point to consider is

that both the turbines that are lowered and those that have a permanent foundation stop

generating power during strong winds by either removal from airstream or a combination of

brakes and varying the pitch of the turbine blades.

Another issue with traditional wind turbines is that of changing wind direction. Within

any given week wind direction and magnitude can change easily especially at lower elevations

(Figure 5). For the horizontal-axis wind turbines typically used in Cuba, additional moving parts

such as bearings must be added to provide the ability of another degree of rotation which further

increases maintenance costs and initial investment. The greatest problem with wind energy is

that of intermittency. This issue truly emerges when a significant percentage of the power used

on the national grid is dependent on wind turbines. Since winds of low altitude have inconsistent

speed and heading, wind turbines provide inconsistent power supply known as intermittency.

When directly connected to a large national grid, this would provide spikes in power that do not

match peak demand times of the population. Therefore, in places such as Denmark where wind

farms can produce up to 19% of the electricity used yearly, they are asked to use brakes when

providing too much power even if the winds are active (Rosenbloom 2006). In many cases

excess energy is sold to other countries at an extremely low rate which is not an option for Cuba.

Energy must be generated from other sources when demand is high and wind farms are not

providing enough. Similar issues occur with photovoltaic solar panels since solar energy is

intermittent due to clouds and the night. A solution to intermittent alternative energy generation

is to store energy when there is excess and use it when needed during peak demand. However,

large scale energy storage techniques also have downfalls.

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Time 1/25/12 7PM 1/26/12 7AM 1/26/12 7PM 1/27/12 7AM 1/27/12 7PM

Wind

Figure 5. Every twelve hours the overall wind magnitude and direction changed over the island

especially near key areas such as Holguin. The only way to consistently and effectively gather

this wind is with turbines that can adjust and pivot to automatically face the airstream (Wind

maps Cuba 2012).

Design Considerations for Energy Storage

The most commonly used large scale system in the world is that of pumped hydroelectric

storage (Pasrich 2012). The issue with this concept is that natural valleys located at significantly

different elevations must exist so that water can be shuttled to and from the different heights to

store potential energy. If Cuba could implement such technology it would risk damaging natural

environments with flooding. The greatest difficulty of pumped hydroelectric energy lies in

locating suitable sites. Batteries are independent of site location and have high efficiencies of 75-

85% (Figure 9) but are extremely resource intensive chemically, require large initial investment,

high maintenance, have a questionable lifespan and are difficult to set up at a large scale (Storage

battery maintenance and principles 1998). Hydrogen storage has the benefit of adaptability to its

location since it is not dependent on any unique site factors. The technology is reasonably

affordable and also has high energy density especially when the gas is compressed (Figure 8).

The largest downfalls of hydrogen are public fear of explosions and high cycle inefficiencies.

The many components used in the cycle including electrolysis, compression, and release of

energy through either fuel cell or internal combustion engine have many losses that stack

creating an overall efficiency of approximately 45% (Figure 9). However the greatest reason for

using hydrogen energy storage with the flying wind turbine system is that this turbine requires a

lifting gas and the three reasonable options available are hot air, helium and hydrogen. Hot air

has the major setback of requiring consistent heating and provides less lift when compared to

hydrogen and helium. Helium is an inert gas that is perfect for generating lift although the issue

is that it is in high demand for other applications and over 75% of the world market share is

controlled by the U.S. (Magill 2012). Hydrogen provides the greatest lift force and is readily

available in abundance through electrolysis although it is flammable.

Cuba can combine the technologies of hydrogen storage and flying wind turbines

effectively to solve many of the issues that arise in alternative energy. Instead of addressing

solely methods of gathering energy such as wind turbines as Cuba has been doing, it is feasible

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to invest in improvements to energy storage transmission and generation simultaneously. In this

fashion Cuba will improve the reliability of its energy transmission infrastructure and provide

energy security through storage and locally sourced power. The island will also eliminate the

issue of intermittency that plagues further wind turbine advancement in so many countries.

Figure 8. Life cycle costs comparison of different energy storage devices. Even though hydrogen

energy storage is not as researched as batteries it outcompetes in terms of cost per kW (nrel.gov

2010).

Figure 9. One of the negative aspects of Hydrogen energy storage is its round trip efficiency

(nrel.gov 2010).

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Prototype Wind Turbine Design

The initial prototype to be used in Cuba is designed to optimally generate 10kW.

Although this may seem small in comparison to the 225 kW horizontal axis wind turbines at the

Isla Turiguano farm, the goal of this prototype is to introduce and test this technology within

Cuba. Cuba has benefited greatly from the concept of distributed power and having more units of

less individual power capacity compliments this decentralized system. This decentralized style

prevents major power interruptions to large numbers of costumers, and reduces the distances

between the power source and consumer, decreasing costs due to transformers and cables while

simultaneously decreasing losses due to long distance cable resistivity. A smaller flying wind

turbine also reduces high initial investment typically associated with large wind turbines and

therefore reduces risk and losses that may occur in the chance of failure. Each side of the

cylindrical Aerostat will have a 5kW generator so as to maintain balance. In order to mitigate

any chance of a spark contacting a possible hydrogen leak and causing ignition, a shroud must be

designed that will also protect the generator from exposure to sunlight, house the shaft, cable

connections and gears and prevent overheating the generator. To further eliminate catastrophic

failure in the case of a lifting gas leak in flight, the hydrogen will be contained within twelve

heat resistant cells so that any loss of hydrogen will not lead to a sudden drop towards the ground

and ignitions will be isolated. Furthermore, design improvements in the form of electrical

sensors can be made to determine events such as accidental detachment from the grounded winch

and seeping gas so that appropriate actions can be taken.

Prototype Hydrogen Energy Storage System

The hydrogen storage system also has critical design choices to be made. This system

primarily consists of an electrolysis machine for generating hydrogen gas, a compressor to

efficiently store the gas into the hydrogen tanks and a hydrogen internal combustion engine to

burn the gas when necessary to generate electricity. A combination of traditional horizontal axis

wind turbines with hydrogen storage technology has been tested and used effectively in the field.

An example of this combination has been employed to self-sustain an island off of the coast of

Norway entirely on wind on a scale based on 2 turbines rated at 600kW. This system utilized a

hydrogen combustion engine of 55 kW an electrolyzer that produces 48 kW of stored hydrogen

energy, a 5.5 kW compressor and hydrogen storage capacity at 200 bar (Trygve Riis 2005). The

concept of wind turbines coupled with hydrogen storage has also been used in Bella Coola,

British Columbia at an even larger scale with an electrolyzer producing 320kW of stored

hydrogen (PowerTech 2011). These field tested systems show that a generated energy to

hydrogen combustion engine ratio of .055 is reliable and self-sufficient. For the floating wind

turbine prototype this leads to a hydrogen combustion engine of 550W and an electrolyzer of

400W. The hydrogen storage capacity can also be scaled down to 20 (Figure 12).

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Figure 12: Hydrogen energy storage used in the Utsira wind energy project (Trygve Riis 2010)

Financial Analysis

Financial history

Less than a decade ago, power blackouts were a common occurrence in Cuba, with 11 oil

fired power plants that only functioned 60% of the time. In 2004 two hurricanes hit eastern Cuba

leaving one million people without power for ten days (Avila 2008). Two years later La

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Revolución Energética, or the Energy Revolution, began and Cuba underwent extreme energy

reforms. Unfortunately these measures were not enough and Cuba had to invest further, this time

into new energy sources. Thus began a long chain of investments away from centralized energy,

towards distributed generation.

Following this model Cuba’s power will be primarily localized with many smaller

sources of power, rather than a few large sources that relied on electrical transmission for

distribution. With this strategy diversification of energy sources becomes important in

maintaining consistency. The largest benefit of the decentralized power grid is its resistance to

disruptions, such as from natural disasters. This becomes especially important given Cuba’s

location and size. Investments in wind, solar, hydroelectric, and biomass energy sources lowered

the average amount of oil needed to generate one kWh of electricity from 280 grams to 271,

which saved Cuba 961,00 tonnes of imported oil from 2006-2007 (Avila 2008). From this small

overall decrease it can easily be seen that any reduction in oil consumption can have very large

effects down the road.

Prototype Finances

The aerostat proposed in this design is especially good for decentralization given that it is

lightweight, portable, consistent, and based off the MARS which was specifically designed with

camping and islands with poor infrastructure in mind. Currently conventional wind generators

are about 20%-30% efficient with regards to their rated capacity. The aerostat should be about

40%-50% efficient, doubling the return on investment over a conventional wind generator

(MARS 2012). This increase in efficiency comes from the fact that the aerostat can be deployed

at much higher altitudes allowing more consistent wind flow. Another factor is that the aerostat

will turn to always face the wind. Due to its lighter weight compared to conventional wind

turbines the aerostat also generates electricity at lower wind velocities with its output further

increased by the Magnus effect (MARS 2012) The Magnus effect is present when the turbine is

rotating creating lift which raises the aerostat into higher velocity winds. It is even more cost

efficient than the commonly used diesel generator in Cuba at 20 cents per kWh versus 50 to 99

cents per kWh (MARS 2012).

An estimate of the total cost of purchase and installation of the floating wind turbine

coupled with hydrogen energy storage can be calculated. A components list with current market

prices approximates total material investment of the system with conservative values (Figure 10).

Equipment Approximate Costs ($) Quantity Total ($)

Electric Winch 300 1 300

Cord bundle 250 609.6 m 250

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Generator 5kW 2250 2 4500

Steel gas tank 60 25 1500

Electrolyzer 650 1 650

Compressor 750 1 750

Hydrogen I.C.E 650 1 650

Fabric tension skin

(Dacron)

136 510 m^2 136

Inner Lining (Mylar) 860 510m ^2 860

Outer Coating (Tedlar) 1630 510 m^2 1630

PMMA cone Shroud 38 2 76

Steel axle 30 14 m 30

Installation/Assembly/

Maintenance

700 Life Cycle 1000

TOTAL: 12332

Figure 10: This table summarizes the costs of the prototype 10kW flying wind turbine and

hydrogen storage system.

Each of these components is critical to the overall success of the design starting with the

5kW generators. These generators will be placed on either side of the flying wind turbine and are

specifically designed for wind turbine use due to their low total mass of 140kgs. The generators

will be connected to each other through a steel tube which will reduce stresses on the aerostat

skin. The electric winch is capable of pulling tensions up to 3638kgs which is overly designed to

safely reel in the turbine with upwards lift forces capable of carrying 388kgs. The cord bundle is

primarily composed of a 0.635cm diameter steel tether that can handle tensions of 3175kgs

surrounded by electricity conducting wires for the positive and negative leads of the generators,

and are also completely wrapped in a protective sheath.

For the hydrogen storage system, 25 steel gas tanks are designed to store a total of 6.7m3

of hydrogen at an optimal pressure of 20MPa. The electrolyzer produces hydrogen from water

for use as a lifting gas and as energy storage at a rate of a cubic meter every 30 minutes. The

compressor is capable of storing the hydrogen at 20 MPa and will be connected to an array of

hydrogen tanks so as to distribute pressures equally. It is important to note that hydrogen storage

is only required when electricity production exceeds demand. The opposite is also true. When

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electrical demand exceeds real-time wind energy production, a hydrogen internal combustion

engine can be used to produce 1kW of electricity. To protect the generator from the elements and

contain electrical sparks further, a PMMA polymer cone will be used as a shroud. The Dacron

tension fiber is the main load bearing component of the skin and was chosen due to its high

tensile strength diffusion rates and costs. Mylar will be used as the interior layer due to its heat

resistance flame retardant and low diffusion characteristics. The fact that hydrogen diffuses less

than helium due to its diatomic nature combined with Mylar will reduce diffusion rates

significantly. A Tedlar outer coating will protect against UV radiation damage and is tear and

fire resistant. This combination of materials will provide overly sufficient resistance to hazards

and result in an estimated service life of 15-20 years. Any damages to the skin can be patched

since it is composed of thermoplastics and the product can be disposed of through recycling. A

conservative estimation of installation, assembly and maintenance was also taken into

consideration. The total cost of 12332$ is on par with current market available turbines of

equivalent power while providing the ability to store power and access powerful winds.

Human and Environmental Impacts

A floating wind turbine using hydrogen as a lifting gas and as a method of energy storage

can incite fear and doubt within the public(Figure . In order to ensure that the public will

embrace this new alternative energy gathering source, a pilot program which will follow multiple

steps will be implemented. The prototype will be located in a semi-remote area in order to test

the design and minimize impact. The purpose of the prototype is to gather data and to gain public

acceptance. The semi-remote location where the design will be tested would be in Isla de la

Juventud since there are inland moderate winds (Figure 4) of about 6.4-7 m/s and the island is

not densely populated. After the design is tested, more can be assembled.

The biggest concern of the public when they hear hydrogen aerostat is the possibility of

failure. This design has many preemptive measures to ensure that if the system does fail, it will

not threaten the safety of nearby bystanders or infrastructures. The design will have a large

number of heat resistant balloon-like cells filled with hydrogen inside a fabric outer skin, which

controls failure by isolating ignited hydrogen from the rest of the lifting gas. If multiple cells are

punctured or ruptured, the system is designed to simply slowly descend. If the hydrogen does get

ignited, the fire will shoot upwards since hydrogen flies upwards at speeds of about 70kph

(hydrogen safety sheet 2012), not allowing the fire to spread out horizontally (Figure 14). This

design is safer than usual wind turbines since it does not have high momentum parts. During

storms it can be stored away preventing damages such as those due to lightning (Figure 13).Wind

turbines used in Cuba have heavy, high velocity components which pose possible dangers during

failure. These massive components may fly off the turbine in unpredictable directions and

distances, which can cause loss of both life and destruction of structures (Figure 11).

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Figure 11. HAWT failure, lubricating oils can ignite, causing an explosion which sends high

speed heavy components flying (Marks 2011).

Figure 13: HAWTs are susceptible to lightning damage since they cannot be stored during a

storm. (Kithil 2008).

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Figure 14: 1 minute after ignition of equivalent energy hydrogen gas and gasoline. (Fuel leak

simulation 2001)

This design has several benefits when compared to traditional wind turbines. For

instance, this design is quieter than traditional horizontal axis wind turbines (HAWT). When the

HAWT blade passes by the support tower, the air in between the blade and the tower gets

compressed causing a loud sound that can be heard for miles (Rosenbloom 2006). This design

avoids this issue since it is floating in the air and when it rotates the air doesn’t get pushed or

compressed against anything. Another problem that can be found with HAWTs is that the tip of

their blades are traveling much faster than the center of the turbine. These fast speeds cause

many bird casualties. It is estimated that between 10000 and 40000 birds and bats are killed each

year at wind farms in the United States alone (Farley 2010). The aerostat design avoids these

fatalities, as it doesn’t spin as fast as HAWTs and it is made out of a fabric, which allows for

impact absorption. Since this design only needs a building to hold it in place and to store the

energy it produces, the design will allow Cuba to gather renewable energy from different

locations. Unlike typical wind farms, which provide a very centralized source of energy since

they consist of multiple HAWTs next to one another, this design will be able to decentralize the

energy which can be gathered from the wind. Cuba is currently trying to transition from having a

centralized power infrastructure to a more distributed power infrastructure. Cuba’s poor energy

infrastructure makes a centralized energy source less ideal than a distributed energy generation

source due to hurricanes or other natural disasters. As of 2007, Cuba has 40.5% of the total

energy generation come from distributed energy generators (Avila 2008).

A great benefit of the design is its adaptability. Unlike traditional wind turbines, which

are in a fixed location, this design allows the user(s) to move the entire system if the need arises.

This flexibility causes little to no impact on Cuba’s infrastructure, since if a problem arises, and

the turbine is no longer wanted or it gets in the way of future structural expansion, it can easily

be transported somewhere that has no such limitations. There is no option when it comes to

traditional wind turbines, they impact Cuba’s infrastructure since they are fixed objects that need

a massive amount of space in order to function properly and meet safety regulations.

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Aside from the amount of space that HAWT farms take up, they also require a very large

quantity of concrete and time to be built. The foundation of most HAWTs consists of about 1250

tons of concrete (Rosenbloom 2006). Concrete production is a major source of CO2 emissions,

which make these behemoth structures responsible for large amounts of CO2 emissions. 1250

tons of concrete represent s 62.5 to 162.5 tons of CO2 emissions (Figure 15)(5%-13%)(Concrete

Co2 2012). A big problem that usual forms of energy encounter is emissions. Cuba’s energy

production is responsible for 94% of CO2 emissions (adsabs.harvard 2010), making any form of

energy generation which is clean very viable. This design has substantially low emission when

compared to fossil fuel energy, it is even lower than conventional wind turbines when you do a

life cycle analysis and consider manufacturing and assembly, making it an ideal source of clean

energy.

Figure 15. HAWT foundation, which typically consists of ~1250 tons of concrete. (NRMCA

2012).

Conclusion

Cuba’s energy infrastructure presents a high degree of opportunity for innovation. The

flying wind turbine proposal has been engineered to satisfy the energy needs of Cuba and

provide a cost-efficient and reliable form of distributed energy. Future improvements in the

functionality and reliability of the design will become evident as the flying wind turbines are

incorporated into Cuba’s infrastructure. We expect efficiency to increase and costs to decrease as

the prototype phase is completed and materials are optimized.

Cuba’s energy problem cannot be resolved with only one or two energy sources, but

rather through a carefully designed combination of several resources. Our proposal presents what

we believe will be an integral part of such a combination. The use of hydrogen in our flying wind

turbine design also presents an opportunity for Cuba’s economy in the possibility of hydrogen

infrastructure. Hydrogen can be used as an energy source for public transportation and vehicles,

and may also be introduced to international trade in the form of liquid hydrogen.

A sense of energy security will allow Cuba to address other problems in the country. The

stability of a constant, efficient, and well-distributed energy source will shift Cuba’s focus from

the current energy crisis to improvement of the country’s overall infrastructure. Furthermore, the

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exploration of alternative energy can incite a culture of innovation in the country, and contribute

to ecotourism in the area.

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Appendix. Decision Matrices

Table 1A. Cuba’s natural energy sources infrastructure decision matrix.

Table 2A. Cuba’s chemical/biofuel energy sources infrastructure decision matrix.

Chemical Energy Marine Microalgae Marine MacroAlgae Sugarcane Ethanol "Energy Cane"/Bagasse Marabu

Objective Weighting

Factor Parameter Mag. Score Value Mag. Score Value Mag. Score Value Mag. Score Value Mag. Score Value

Energy Generation 0.15 Research Great 10 1.5 Great 10 1.5 Okay 6 0.9 Okay 6 0.9 Fair 4 0.6

Environmental Impact 0.15 Research Great 10 1.5 Great 10 1.5 Okay 6 0.9 Okay 6 0.9 Poor 2 0.3

Maintenance Costs 0.20 Research Good 8 1.6 Great 10 2.0 Fair 4 0.8 Fair 4 0.8 Great 10 2.0

Sustainability 0.15 Research Great 10 1.5 Good 8 1.2 Okay 6 0.9 Okay 6 0.9 Fair 4 0.6

Initial investment 0.35 Research Good 8 2.8 Good 8 2.8 Okay 6 2.1 Okay 6 2.1 Good 8 2.8

Overall value 8.9 9.0 5.6 5.6 6.3

Energy Source Solar Energy Wind Energy Hydro Geothermal Chemical Nuclear

Objective Weighting

Factor Parameter Mag. Score Value Mag. Score Value Mag. Score Value Mag. Score Value Mag. Score Value Mag. Score Value

Availability 0.50 Research Great 10 5.0 Good 8 4.0 Great 10 5.0 Poor 2 1.0 Great 10 5.0 Poor 2 1.0

Technology 0.30 Research Great 10 3.0 Great 10 3.0 Great 10 3.0 Poor 2 0.6 Great 10 3.0 Poor 2 0.6

Reliability 0.20 Research Okay 6 1.2 Okay 6 1.2 Good 8 1.6 Great 10 2.0 Good 8.0 1.6 Great 10 2.0

Overall value 9.2 8.2 9.6 3.6 9.6 3.6

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Table 3A. Cuba’s hydro energy sources infrastructure decision matrix.

Hydro LIMPET(Waves) Dam+Micro Generator Tide Capture

Objective Weighting

Factor Parameter Mag. Score Value Mag. Score Value Mag. Score Value

Initial Investment 0.30 Experience Good 8 2.4 Okay 6 1.8 Poor 2 0.6

Maintenance Cost 0.10 Research Great 10 1.0 Good 8 0.8 Good 8 0.8

Availability 0.25 Research Good 8 2.0 Fair 4 1.0 Poor 2 0.5

Modularity 0.15 Research Good 8 1.2 Good 8 1.2 Okay 6 0.9

Energy Generation 0.20 Research Good 8 1.6 Great 10 2.0 Poor 2 0.4

Overall value 8.2 6.8 3.2

Table 4A. Cuba’s solar technologies energy infrastructure decision matrix.

Solar Photovoltaic Heliostat Field Solar Water Heater

Objective Weighting

Factor Parameter Mag. Score Value Mag. Score Value Mag. Score Value

Initial investment 0.35 Experience Great 10 3.5 Poor 2 0.7 Good 8 2.8

Maintenance cost 0.15 Experience Good 8 1.2 Okay 6 0.9 Good 8 1.2

Reliability 0.35 Hours Okay 6 2.1 Poor 2 0.7 Great 10 3.5

Modularity 0.05 Experience Good 8 0.4 Fair 4 0.2 Good 8 0.4

Impact on Infrastructure 0.10 Research Great 10 1.0 Poor 2 0.2 Great 10 1.0

Overall value 8.2 2.7 8.9

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Table 5A. Cuba’s wind energy infrastructure decision matrix.

Wind Energy HAWT 3 Blade VAWT Hybrid (Altaeros) FWT Magenn FWT

Objective Weighting

Factor Parameter Mag. Score Value Mag. Score Value Mag. Score Value Mag. Score Value

Initial Investment 0.30 Research Poor 2 0.6 Okay 6 1.8 Good 8 2.4 Great 10 3.0

Energy Generation 0.20 Research Great 10 2.0 Good 8 1.6 Okay 6 1.2 Fair 4 0.8

Maintenance Cost 0.10 Research Poor 2 0.2 Great 10 1.0 Fair 4 0.4 Okay 6 0.6

Modularity 0.15 Research Poor 2 0.3 Good 8 1.2 Fair 4 0.6 Great 10 1.5

Adaptability 0.25 Research Fair 4 1.0 Good 8 2.0 Great 10 2.5 Great 10 2.5

Overall value 4.1 7.6 7.1 8.4

Table 6A. Final energy infrastructure decision matrix.

Alternative Technology Solar Water Heater Algae LIMPET (Wave) Magenn FWT

Objective Weighting

Factor Parameter Mag. Score Value Mag. Score Value Mag. Score Value Mag. Score Value

Initial Investment 0.25 Research Great 10 2.5 Great 10 2.5 Poor 2 0.5 Great 10 2.5

Energy Generation 0.10 Research Okay 6 0.6 Good 8 0.8 Great 10 1.0 Great 10 1.0

Maintenance Costs 0.20 Research Okay 6 1.2 Okay 6 1.2 Great 10 2.0 Good 8 1.6

Modularity 0.15 Research Okay 6 0.9 Great 10 1.5 Poor 2 0.3 Great 10 1.5

Scalability 0.15 Research Fair 4 0.6 Great 10 1.5 Poor 2 0.3 Okay 6 0.9

Infrastructure Impact 0.15 Research Good 8 1.2 Okay 6 0.9 Poor 2 0.3 Good 8 1.2

Overall value 7.0 8.4 4.4 8.7

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Table 7A. Comparison table for vertical axis aerostat airborne wind turbine.

Comparison Table Pros Cons Design Improvements

Vertical Axis Aerostat Airborne Wind Turbine

The Magnus effect creates lift and controls the blimp so that it moves around less and the cable drags less. This creates a slightly smaller radius of flight. Operable between 1 meter/sec and in excess of 28 meters/sec. Altitudes from 400-ft to 1,000-ft above ground level are possible, without having to build an expensive tower, or use a crane to perform maintenance. Mobile and can be easily moved to different locations to correspond to changing wind patterns. Mobility is also useful in emergency deployment and disaster relief situations. The use of hydrogen as an energy storage technique is less resource intensive when compared to other methods such as batteries and potential energy storage. Batteries are typically expensive, require high maintenance, and have limited lifespans. However, when compared to hydrogen energy storage batteries are much more efficient. Hydrogen storage can also be used to alleviate intermittency problems common in other alternative energy sources such as photovoltaic solar panels.

This is a relatively new technology that has not been tested at a large commercial scale. Therefore consequences and risks can only be estimated. However, some prototypes are available and wind energy has been tested at large scale before. Tension cycles can cause fatigue failures at winch, ground attachment, turbine attachment or cable. Tension on main transmission line means the cables must be strong. However, the more sheathing and cases added to increase strength further adds weight causing additional strain on structure. Total Airports in Cuba~38. Aircraft flight heights depend on model: Cesna and Piper unpressurized~5000ft to a cap of 10,000ft. Typical cruising altitude of jets ~30kft. Optimal height for maximum wind speed in Cuban atmosphere ~1-2km = 3280.84-6561ft. However a longer cable would be needed since it does not fly directly above its tether. Wind Energy is not a reliable continuous energy source. Spikes in energy generation can lead to overloads in the power grid or moments of low energy. Therefore the electricity generated may not be used to its full potential unless stored. Leaking gas is an issue for aerostats expected to stay buoyant for long periods of time. Helium is becoming an increasingly rare and expensive gas of which 75% of the world’s supply is controlled by the US. If hydrogen is used as both the lifting gas and an energy storage method then either hydrogen fuel cells or hydrogen combustion engines must be used in conjunction with storage tanks. This infrastructure is not currently available in Cuba.

A generator can be added before the winch that gathers energy from the tension cycles of the winds and utilizes a spring as a damper. This extra energy generated can be used to run the winch. However will it be cost effective? This turbine will be limited in size and height according to what forces an affordable cable can withstand. Locations of airports are also a limiting factor. However stacking turbines on one cable can increase energy generation density to a level slightly more comparable to traditional turbines. Storage methods of energy all have pros and cons especially for initial investment. A mix of compressed gasses and hydrogen generation can be used. Hydrogen can even be generated from urine for less voltage than water. Polyester fabric coated with neoprene rubber is used for many modern blimp skins and might lead to less diffusion (see below). This design does induce the Magnus effect which induces some lift. Hydrogen is an alternative floatation gas. However, it also has downfalls, dangers and public fears.

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Table 8A. Comparison table for algae biofuels.

Comparison Table Pros Cons Design Improvements

Algae Biofuels

Cuba already has an infrastructure of largely liquid fuel based energy generation. This system includes distributed generation in the form of diesel generators and oil fired power plants that use fuel-oil. Due to this biodiesel derived from microalgae can easily be used with the current infrastructure while ethanol derived from macro algae can be utilized as a gasoline replacement. Cuba is largely agricultural based which lends itself to cultivation and harvesting of algae. Algae biofuel does not compete with land based food crops like other oil feedstock such as corn since it is can be grown in the ocean or ponds. The fuel generated per hectare of crop is greatest in algae when compared to other sources of biofuels. Algae does not contain lignin which leads to easier processing of grinding when compared to land based crops. When compared to other alternative energy sources, algae is easily scalable and can be initiated at a small scale with less capital investment but also less results. Algae do not use fertilizers and its growth can be accelerated using existing wastewater and emissions from the island.

This is a relatively new technology that has not been tested at a large commercial scale. Therefore consequences and risks can only be estimated. However, some prototypes are available and algae have been harvested at large scale before. Fuels have been produced successfully many times but not at an industrial level. Not all Micro and Macro algae lends itself to fuel generation and heavy research through experimentation will be required to choose a compatible species strain to cultivate. Although Cultivation of natural growing algae is the most affordable solution, the biodiversity present leads to inconsistent sources of algae that can only be processed reliably by fermentation into methane. Burning this methane will produce electricity which is not currently a major part of the Cuban infrastructure. Growing Algae is extremely water intensive and if fresh water species are used this would lead to a larger additional strain on the fresh water supply than the current agriculture system in Cuba imposes. A very delicate balance exists between microalgae that produce more oils and those that are sturdier. The more resilient strain produces significantly less oils since these properties are inversely related. Algae grown in a marine environment is greatly exposed to the elements which can destroy a crop. Native algae and wildlife may compete with any cultivated species. Cultivation of Algae requires infrastructure and machinery not currently available in Cuba. Refinery of algae into biomass and biofuel also requires many steps and machinery. Dispersion of wastewater and would require adaption of infrastructure. Too many factors must be taken into consideration for site location for algae to be grown effectively. These factors include: distances from a wastewater source, source, a location clear from water traffic, far from recreational beaches, close to land refinery for ease of cultivation, sheltered from dangers of marine environment, and suitable depths of water.

Only marine species of algae can be used so as to eliminate any strain on drinking water. Significant capital investment and testing will be required to find the right strains of algae for Cuba. Ocean water can be pumped inland to run marine open pond microalgae cultivation. However this would also utilize land. The more factors for site location satisfied the better the algae yields. However this narrows the list of potential locations greatly. Therefore the solution available is to compromise efficiency for availability.

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