The following case study demonstrates the application of the strategic analysis of complex systems (SACS) method described in Chapter 13. This case study was the final project of an honors course on sustainable energy in which the following students participated: Nathaniel Amack, Anna Balzer, Michael Belazis, Jesse Fife, Nicholas Haase, Carl Husmann, Gideon Irving, Scott Pawlowski, and Charles Tse. The assignment asked the students to determine the steady-state carrying capacity of the island of Oahu based on food, energy, water, transportation, and population. As a first step, the students were asked to make back-of-the-envelope estimates to ascertain which of the above would be the limiting factor that determines the population that the island could support sustainably.

Sustainable Oahu

by

Nathaniel AmackAnna BalzerMichael BelazisJesse Fife Nicholas HaaseCarl HusmannGideon IrvingScott PawlowskiCharles Tse

1. Introduction

Within the next few years the world will change dramatically. Some weeks ago the United Nations proclaimed that the human population has passed 7 billion and predicted that it will reach 9 billion by the year 2048. This is a huge number of people which may exceed the carrying capacity of the global ecosystem.

The Earth is a closed system and except for an occasional asteroid its only energy exchange with the universe is by radiation; it is irradiated by the sun and radiates heat into space. Thus for a sustainable future, this energy exchange must come into balance. Although the amount of solar radiation reaching the earth is enormous, the usable energy to sustain an industrial society is limited by the laws of thermodynamics. The global energy balance was changed a few hundred years ago when humans discovered fossil fuels and began to use them at an ever increasing rate. This has led to a more complex social structure that has become increasingly vulnerable to collapse as the supply and quality of fossil fuels diminishes. There is global concern about an energy crisis, particularly about a decline in oil production, often called “peak oil”. But there are other factors, such as food and water, which may soon limit the population in some parts of the world.

The concept of an “ecological footprint was proposed in 1990 by William Rees and Mathis Wackernagel. Calculators are now available to measure humanity’s demand on nature. The measure indicates how much land and water a given human population requires to produce the

resource it consumes using current technology. “Carrying capacity” is a concept often applied at a global scale. It expresses the biophysical limits of the environment as a way to estimate the maximum population that can be supported indefinitely by a particular geographical environment. This paper reports the work of an interdisciplinary senior level course offered in the Department of Mechanical Engineering at the University of Colorado at Boulder. The class wanted to explore the questions of ecological footprint and carrying capacity from an engineering perspective. The engineer’s job is to apply science and facts about the physical world in order to design and build systems that work to achieve specified requirements. The case study of the Hawaiian island of Oahu was used, and new methods of Transition Engineering were applied. The method was to first assess the ability of Oahu to support the current population of one million, and then to examine the limiting environmental and natural resource availabilities to determine the population carrying capacity. Finally, strategic analysis of the possible supply and demand options was carried out to identify opportunities for sustainable development.

1.1 Case Study on Oahu

Captain James Cook arrived in 1778 it is estimated that there were about 300,000 native Kanaka Maoli islanders on the 7 Hawaiian Islands. Today, there are between 225,000 and 250,000 people of Hawaiian descent living on the islands. But the arrival of Europeans brought many diseases to which the natives had no immunity and the population shrank to 154,000 by the year 1900 according to the U.S. Census Bureau. By 1950 the population grew to half a million and today it is estimated that 1.2 million people live on all the islands with about 1 million on Oahu.

Hawaii’s gross state product is about $44 billion with financial services, tourism, government, and trade (including transportation), contributing about $10 billion each. Manufacturing contributes only about $1 billion. The islands import virtually all their food and fuel (mostly oil). The need to import oil also for electricity generation is responsible for its exorbitant cost of 26 cents per kWh, the highest in all the USA. This state of affairs is obviously unsustainable and for the future of the state, it is important to estimate its carrying capacity, especially of Oahu, where more that 80 % of its population lives. Shown below is a schematic of the island.

1.2 Carrying Capacity Analysis The looming energy crisis on Oahu due to declining world oil supply is only one facet of sustainability. Sustainability is multidimensional and interconnected, requiring consideration of a wide range of elements. For this case study of sustainability we selected the small island of Oahu, which is rich in renewable resources, but lacks any fossil fuels. Thus, it provides an excellent example for such a case study.

We focused in our study on five key elements generally considered necessary for a sustainable society:

1. Food2. Energy3. Water4. Transportation 5. Shelter

Initially we did not know whether any one the 5 would be the most important or if a combination of them would be the limiting factor on island population. Since each of them involved social and technical aspects of the question, each of the five elements was addressed by an interdisciplinary team of two students, one from within the engineering program and one from outside engineering. An analytic approach developed by Krumdieck and Hamm1 was used for the work. The approach entails developing a matrix of possibilities for each of the elements of sustainability. These matrices correlate possible resource supply and demand options and identify which combinations of supply and demand could be sustainable. These combinations are further evaluated for their energy impacts, costs, and risks.

1 Krumdieck, S. and Hamm, A., Strategic analysis methodology for energy systems with remote island case study, Energy Policy, Vol 37, Issue 9, September 2009, Pages 3301-3313

Each student team developed a possibility matrix for its focus area. These matrices were then compared to identify interactions and limiting resources. The information from this collaboration was used to refine the possibility matrices and develop conclusions. Each team reported on their focus area for the conclusion of an honors course in Global Sustainability. This article represents an abstract of that work.

2. FOOD and AGRICULTURE

Agriculture is one of the key issues when determining if a society is sustainable. Currently little agriculture exists on the island of Oahu because of the high land prices. All crops planted on the island are sold for profit, such as coffee beans. This section of the sustainability analysis will look at the arable land available on the island and develop a rough estimate of the population that can be sustained on the island with various types of diet.

ASSUMPTIONSThe following lists the assumptions made for this section: The amount of arable land is estimated at 125,000 acres. Electric tractors and other vehicles used in harvesting and transport of foods will be available. The current diet and calorie intake of the population of Oahu was assumed to be the same diet and

calorie intake as consumed by the people on the mainland. The diet of the entire population of Oahu is assumed to be uniform and identical.

SYSTEM ANALYSISUsing data of the average yields per acre, calculations were done to find out if the current population of one million can be sustained on Oahu given several diet-calorie-intake combinations. It was found that Oahu did not have sufficient arable land to sustain a population of one million.

To estimate the sustainable population the following table was constructed to see what population can be sustained based on the amount of land required per person per year. This number is dependent on the diet of the population. The acreage per person per year is listed in the table. The vegetarian diet was estimated to require 0.6 acre per person per year because the diet requires more land than the vegan diet to raise dairy cows. The pescatarian diet was assumed to require 0.4 acre per person per year because the diet allows fish to replace high protein vegetables, yet doesn’t require arable land. With these figures, the total sustainable population of Oahu ranged from about 200,000 to 300,000 people. For the purpose of this study, the higher figure was used because there are additional opportunities to grow food on rooftops and backyards.

This population, along with the food energy multiplier and the calorie intake, can be used to calculate the energy required in the agricultural sector. The food energy multiplier is a measure of the behind-the-gate farm inputs, processing, packaging, storage and preparation energy in the food system. The food energy multiplier decreases as the calorie intake decreases because it was assumed that a lower calorie diet contains a higher percentage of nutritious food. Higher calorie diets were assumed to contain more processing, packaging, transporting and storage processes, which is why the energy multiplier is higher. The current food energy multiplier for mainland American diets is 10-12 times the actual food energy content.

The chart uses the following color code to represent the possibility of implementing the diet-calorie-intake combination into Oahu’s society:

Red indicates that the combination cannot sustain a population of 200,000 to 300,000. Orange means that the combination can sustain a population of 200,000, but requires a

dramatic change in lifestyle. Yellow means that the combination can sustain a population of 200,000 with some changes in

lifestyle and little exports. Green means that the combination can sustain a population of 300,000 with some changes in

lifestyle and significant export of fruits and fish.

Table 1: Agricultural Sustainability Chart.

DEMANDSUPPLY

2700 2500 2300 2100 2000Calorie intake (kCal/person-day)

Acres/ person-yr. required

Total sustainable population

14 10 7 5 2Food Energy Multiplier

3209 2122 1367 891 340Energy Demand (GWh/year)

Current Diet 1.2 104167Pescatarian 0.4 312500Vegetarian 0.6 208333Vegan 0.5 250000Pre-Industrial 2.6 48077

Arable Land (acres) 125000Total sustainable population 300000

With a sustainable population of 300,000 people, a rough estimate about the total water required to produce the food for each diet can be found. For the vegetarian, vegan, and pescatarian diets, the required amount of water ranges from 26 billion gallons to 39 billion gallons. The latter amount of water is available as shown in Section 4.

DISCUSSIONThe red boxes in the matrix show that the current U.S. diet and the pre-industrial diets which cannot sustain a population of 300,000 because it would require too much arable land.

The orange boxes in the matrix show the diets that can sustain a population of about 300,000 people. This combination would require dramatic changes to the lifestyles of the inhabitants due to the reduction in energy use. Implementing this plan would eliminate refrigeration and storage, as well as processing and packaging of foods. The energy used would only be for cooking and minimal storage. Families would have to visit the outdoors market for fresh produce and fresh milk frequently. Daily fishing would also need to be done and food could not be exported.

The yellow boxes in the matrix show the diets that can sustain a population of 300,000, and there would not be dramatic changes to the lifestyles of the inhabitants. This plan would allow enough energy for storage, some processing and packaging, and cooking. However, little to no fruits and

vegetables will be available for export. The fish caught could all be available for export, except for the pescatarian diet. The green boxes in the matrix show the diets that can sustain a population from 250,000 to 300,000 people with some fruit, vegetables, and fish exports. This plan would only require a few changes in lifestyles. There would be enough energy to process, package, cook and store food. There would also be enough energy to freeze fish or coffee for export. The only change to the lifestyle of the inhabitants would be a change in diet.

3. Energy

In order for the island of Oahu to be a sustainable system it will need to provide all of its energy needs from indigenous renewable sources. For the purposes of this project, solar and wind sources on Oahu will be assumed to be the sole providers of energy through wind turbines and solar photovoltaic (PV) electricity.

ASSUMPTIONS No storage for electricity production (although pumped storage sites are available). Flexible consumption to match the produced renewable electricity. An adequate electric transmission system.

PV Amount Wind Amount

Maximum land available for PV production

90,000 acres Maximum land available for wind production

75,000 acres

Total rated capacity of PV on 90,000 acres

14,000,000 kW Turbine rated capacity 2 MW

PV capacity factor Roughly 20% Wind capacity factor 30%PV annual maximum production

2.6E+10 kWh Wind annual maximum production

1.5 E+10 kWh

SYSTEM ANALYSISUsing these assumptions, the chart below shows the feasibility of different annual production levels of electricity for Oahu (the x-axis) when produced by varying levels of wind and solar (the y-axis). Red squares indicate impossible or impractical scenarios (technologically and/or economically), orange indicates plausible but high risk and high cost scenarios, yellow indicates probable scenarios with some risk and cost concerns, and green indicates the most feasible scenarios in terms of supply source and production level.

Table 2: Energy Sustainability Chart

Current Total Energy Usage

Twice Current Production Capacity

Current Electricity Production Capacity

Current Electricity Usage

Half Current Electricity Usage

6.0E+10 kWh/year

3.0E+10 kWh/year

1.5E+10 kWh/year

8.0E+9 kWh/year

4.0E+9 kWh/year

All Wind 2.00E+05 1.00E+05 5.00E+04 2.66E+04 1.33E+04

75/25 Wind/PV 2.00E+05 1.00E+05 5.00E+04 2.66E+04 1.33E+04

50/50 Wind/PV 2.00E+05 1.00E+05 5.00E+04 2.66E+04 1.33E+04

25/75 Wind/PV 2.00E+05 1.00E+05 5.00E+04 2.66E+04 1.33E+04

All PV 2.00E+05 1.00E+05 5.00E+04 2.66E+04 1.33E+04

Values in table are kWh/person/year based on theoretical maximum sustainable population of 300,000Current consumption kWh/person/year – 6.00E+4

DISCUSSIONEnergy production would not be the limiting factor for the sustainability of the island. Using modern technology, 4.1E+10 kWh/year of energy could be produced by wind and PV, which is about two-thirds the current total energy usage, an amount of energy that could support the current population of 1,000,000 given some technical and lifestyle adaptations. A population of 300,000 instead of the current 1,000,000 would allow for higher per capita energy consumption and better quality of lifestyle. The middle column of Table 2, at a population of 300,000, is comparable to current per capita energy consumption, but is found to have high risk and cost. However, if energy demand can be reduced to the far right columns, then risk and cost fall to more reasonable levels. A combination of solar PV and wind, most likely relying more on the cheaper wind resource, could provide enough energy for a sustainable Oahu and the green boxes in Table 2 reflect this. The electricity then needs to be divided between all other sectors in the most efficient way possible. The over-riding conclusion is that using technically advanced renewable energy systems, enough energy for a more than adequate life on Oahu can be provided. The consequence of this level of wind development would be a dramatic industrialization of the landscape as even the Half Current Electricity demand would require numerous 3 MW wind turbines and solar PV panels.

4. Water

To evaluate the sustainability of water resources on the island of Oahu, five potential sources were investigated: rainwater, river water, desalination, recycled and other non-potable water, and aquifers. The ability of these resources to meet the demand of the current population of one million as well as the projected population of 300,000 for the island of Oahu was assessed on the basis of availability, cost, and energy requirements.

ASSUMPTIONS: Water availability was estimated for

populations of one million and three hundred thousand people.

The effects of climate change are not factored into the estimates; however, climate change is expected to have adverse effects on water supply.

Current per capita water use is estimated to be 180 gallons/person/day. This number reflects total island usage divided by the population.

Larger per capita uses are investigated under the assumption that per capita water use will rise with increase in agriculture and industrial processes for a sustainable society.

Fresh water is pumped from seven aquifers beneath the island with an estimated sustainable yield of 446 million gallons per day (mgd).

Necessary infrastructure adjustments to allow for large withdrawals are for the most part planned or under construction currently.

All wells are assumed to have a depth of 250 ft with relatively small exit velocities. The latter assumption reduces the calculated energy requirement of pumping water from the aquifers.

Pump efficiency was universally estimated to be 85%.

Energy requirements for inter-aquifer pumping were neglected.

Rainfall is assumed to be 1 in of rainwater per month. 1 in of rain over 1,000 sq ft will provide 600 gallons of water.

A total of 440,000 homes with an average roof size of 1,200 sq ft.

20% of water demand can be met by non-potable sources

SYSTEM ANALYSISTable 3: Water Sustainability Chart for One Million People

Water Demand (gallons/person/day)300 200 150 100 50

Pote

ntia

l Wat

er

Supp

ly S

ourc

es

Rainwater --- --- --- --- ---Aquifers 100 68 51 33 16

Desalination 2600 1800 1300 880 440Rivers --- --- --- --- ---

Recycled/Non-Potable Water 36 23 18 11 5.3

Note: The numbers within the colored blocks reflect the estimated energy input the corresponding water supply requires in units of kWh/person/year.

DISCUSSIONRivers would not be a good source of water for the population. This is primarily due to their perennial nature. Rivers cannot supply any consistent amount of water, so its role as a water source was rejected.

Rainwater is an equally unattractive option as a water source. While some areas of the island receive a lot of rain, most of the populated areas do not get very much. Using the assumptions listed above, rainwater could supply about 6 gallons/person/day for the average citizen. The 50 gallons/person/day block was left orange given the possibility of heavier rain fall in some areas.

Desalination is another source of water without a promising outlook. Current desalination capacity is only about 5 million gallons per day (mgd). The plant was designed to produce 15 mgd, so it can be assumed that this additional capacity could be gained at a relatively low cost. However this leaves a 35 mgd gap that would need to be filled to meet the minimum of 50 gallons per person per day. Since the capital cost required to build and operate additional plants is significant, more desalination would not be economically and energetically feasible.The recycled/non-potable water source is more attractive. Current estimates suggest a supply of about 40-70 mgd, of which about 40% is recycled. The amount of recycled water could increase if more treatment plants are constructed. However, given the high capital cost of the construction of such plants, it seems unlikely that this sector will provide more than 100 mgd. That being said, should additional treatment plants become necessary for the water that aquifers provide, recycled water capacity could be increased.

Given the limitations of the other sources, it becomes clear that aquifers would have to be the primary source of water in this society. Even at 300 gallons per person per day, the aquifers will be a sufficient source for one million people for the foreseeable future. Additionally, as noted in the assumptions, the current infrastructure to supply this level of water demand are already funded or completed, meaning that the capital costs will be a non-issue. Considering that only 300,000 people can be sustainably fed here, sustainable water supply is more than adequate for Oahu.

5. Transportation

The goal of this part of the project was to develop the concept of a transportation system for the population of Oahu that the island can support, assuming a resource limitation with no available fossil fuel for transportation support from outside of the island.

ASSUMPTIONS Oahu can support a population of 300,000 due to agricultural limitations. Electric vehicles such as cars, scooters, and buses will be available to island inhabitants.

Therefore trade for these vehicles outside of Hawaii will be possible for the purposes of this project.

Food and industry transport was not considered. All Oahu citizens are willing and able to bike a distance of five miles. Buses take 40 people per trip, cars take 1.8.

SYSTEM ANALYSISNo liquid fuels are available and transportation will be dictated by the amount and type of available energy on Oahu.

Table 4: Transportation Sustainability Chart

kWh/person/year Key2000 1500 1000 500 0

Walk & Bike OpportunityElectric Rail FeasibleElectric Bus Not PossibleElectric ScooterElectric Car

Walking and BikingWalking and biking were combined due to their similar energy needs. Both walking and biking require virtually no extra energy. Since energy needs have been broken down into kWh per person per year, and since walking and biking require little to no extra energy production, any amount of energy supply will meet the transportation needs of a walking and biking population. Because of this, all energy demands are feasible. Although this is the case, it is not reasonable to assume that all travel needs will be met through just biking and walking. If a person needs to travel a large distance, biking will not be sufficient to reach the destination in a reasonable amount of time. Therefore, not all transportation needs can be met through biking and walking alone.

Electric RailHawaii is already in the process of installing a rail system that will span twenty miles around Pearl Harbor from Kapolei through Honolulu. The energy needs of rail are extremely low once a rail system is installed. From a kWh per person per year approach rail seems like a winner, but for Hawaii there are a few problems. The current rail being installed costs at least $4.34 billion. When broken down into cost per mile of rail, the installation is at least $215 million per mile. A comparison is a proposed rail system in Michigan for a magnetic train. The cost of this railway is expected to be about $15 million per mile or about 14 times less than the cost of Oahu’s rail system. Because of this, rail has been deemed feasible but not a realistic opportunity and will not be recommended as a mode of transportation. Furthermore, rail would have to be extremely cheap to even justify its use based on its ability to alleviate the load (total amount of person miles traveled) of the transportation system. In an optimistic scenario for rail transportation, it would not provide any more than a 0.5% reduction of the total travel need.

Electric BusOahu already has a great bus transportation system imaginatively called TheBus. TheBus travels to almost every main location of the island. Routes include most of the coastal regions, airport transit, and extra routes to major locations such as Honolulu and Waikiki. Because of this, no extra transportation system will need to be developed to make an electric bus system viable; they can simply take over the existing gasoline-based bus system. Electric buses can have an average equivalent of 24 mpg as compared to 7 mpg for a regular school bus. This is a large improvement in efficiency compared to current rates. It was found that the population of Oahu could support its transportation needs through a bus system that used less than 500 kWh per person per year. This is by far the best option for energy use per person, aside from rail. One problem with a bus system is that residents would have to rearrange their schedules to account for the schedule of buses. Since many Americans tend to be somewhat impatient, Hawaiians would need to develop a patient lifestyle.

Electric ScooterElectric scooters are a great option for personal transport. Currently available electric scooters have an equivalent of over 250 mpg. If every resident of Hawaii used scooters for transport they would be able to use less than 1500 kWh per person per year. Scooters are relatively cheap compared to cars and would be able to meet the personal transportation needs for any citizen of Oahu. Some disadvantages include the inherent increased danger of driving scooters and their inability to transport large amounts of materials, such as groceries for a large family without a side car or trailer.

Electric CarElectric cars are the worst option when looking at energy use. They require more than 1500 kWh/person/year assuming the whole population of Hawaii uses them at an average 1.8 people per car trip. Although they are energy intensive, their benefits over scooters include safety and the ability to transport larger amounts of material. That said, scooter safety is greatly improved when not sharing the roads with cars.

Proposed Transportation SystemThe most sustainable transportation system is also the most energy efficient. In this respect, it would be best to include the maximum amount of biking and walking as possible and then subsequently utilize the next most efficient modes of transport. It is estimated that roughly 41 percent of work commutes are shorter than five miles. From a calculation using the population of Hawaii and the vehicle miles driven per month, it can be shown that the average Hawaiian travels roughly 25 miles per day. Using these two pieces of information, it is assumed that 41 percent of all citizens will bike ten miles of their commute per day (five miles to, and five miles from work). This leads to an approximate 16 percent of the transportation needs being met by biking or walking. The bus system currently on Oahu services 311,000,000 person miles per year. This accounts for about 2.5 percent of all travel for the current citizens of Oahu. It is assumed that a lifestyle change can increase bus use to 10 percent of the population. For scooters, a ballpark estimate of 50 percent of transportation usage was assumed because any individual trips would be possible for scooter. This would give every citizen of Hawaii 12.5 miles per day of scooter travel, a reasonable amount for personal use. All previous transportation methods were estimated to meet 76 percent of travel needs, leaving 24 percent of the transportation requirements for the island to be met by electric car. Under the current average distance travelled in Hawaii, this allows a family of four to travel more than twenty miles per day for any need. An electric car is required for things such as family trips, grocery shopping, and transporting large numbers of people or goods anywhere a bus does not go. Under this system, an estimated 1000 kWh per person per year would be needed to support the transportation demands of an Oahu population of 300,000 people.

6. Shelter

Of the many ways to decrease energy use and costs on the island of Oahu, sustainable building technology is very important. In the United States, residential and commercial buildings

consume nearly 39% of the nation’s primary energy, 71% of its electricity, and accounts for nearly 38% of its the total carbon emissions. Although sustainable building technology is available, a systemic shift in both lifestyle and use of energy efficient technology is necessary to implement it. This study presents the results of calculating the number of people that could be sustainably supported on Oahu, assuming a shift in lifestyle and energy efficient building technologies is put into effect.

ASSUMPTIONSFor the analysis the following assumptions were made: Current electricity usage of Oahu: 8000 GWh/year. Current fossil fuel usage of Oahu: 64482 GWh/year (220 *10^12 Btu/year). The percentage breakdown of usage in each sector is known. 57% of homes have mechanical air conditioning (from 2006 data). Air conditioning adds 70% to the energy usage of a typical home. By switching to high efficiency appliances, the residential energy consumption can be

reduced by 50%. Switching to high efficiency appliances, commercial energy use can be reduced by 30%.

SUSTAINABILITY CHARTThese assumptions, while based on verified data, still add a significant uncertainty to the results gathered below. The transportation and industrial sectors were neglected, and all numbers in the following chart are in units of kWh per person per year.

Table 5: Shelter Sustainability Chart

Current Usage

90% of Current

80% of Current

70% of Current

60% of Current

Current Infrastructure 8000 7200 6400 5600 4800Current without AC 6900 6200 5500 4800 4100Residential minus 50% (no AC) 5700 5100 4600 4000 3400Commercial minus 30% (no AC) 5600 5000 4500 3900 3400Residential minus 50% Commercial minus 30% (no AC) 4400 4000 3500 3100 2600

Note: Units in kWh/person/year

DISCUSSIONThe options shown in green use the least amount of energy, which is between 4000 and 5000 kWh per person per year, which corresponds to a total energy demand of approximately 800 to 1200 GWh per year for the sustainable population of the island. Considering the uncertainties inherent in the analysis due to the assumptions made, a value of 1350 GWh per year should be expected in order to ensure a reasonable capacity margin.

If the situations in yellow were implemented, then the minimum energy use that could be included is between 520 and 780 GWh per year or 900 GWh per year with a reasonable margin of safety. These situations contain energy conservation measures that would be expensive to implement and would only be necessary if other options have too much energy usage to be sustainable.

Even with the highest value of 1350 GWh per year, it would be possible to reduce energy use enough to allow for the island of Oahu to become individually sustainable and to provide adequate shelter for a population of 300,000 people. However, in order for Oahu to achieve sustainability, the populace would have to make significant changes to their lifestyles.

1.

2.

3.

4.

5.

6.

7. Conclusions

This study explored the implications of local resource constraints on population carrying capacity and lifestyle for Oahu, an isolated island without any fossil fuels. It investigated a future sustainable energy structure for the island, but did not address the question of how a transition from the current fossil fuel lifestyle to a zero fossil fuel society would occur. Oahu has, at present, a population of one million and imports most of its food and all of its energy. But because of food production limits, a population of at most 300,000 could be supported. Of the five key factors for a sustainable society, water, food, energy, transportation and shelter, the ultimate constraint was found to be land availability for agricultural food production. No limitations on water use were necessary because the recharge rates of aquifers on the island were sufficiently high, but this situation may not apply to other locations. Renewable energy generation was also found to be sufficient to provide for distributing water and adequate transportation and shelter. It was further found that modern technology for renewable energy generation and its efficient use can generate enough energy to provide a fairly high standard of living for the islanders, but a different lifestyle would be necessary. The key lifestyle changes to achieve a sustainable society without fossil fuel are:

1. Protein sources from fish instead of meat2. Starch intake mostly from taro3. Transportation without liquid fuel (no capacity for bio-fuel)4. Majority of trips under 5 miles made by bicycles, electric scooters, and/or mass transport5. Urban form of habitation optimized for these modes of transportation6. No mechanical air conditioning in private shelters7. No site restrictions for PV and Wind Turbine locations

8. Adequate electric power distribution system

This article is a preliminary analysis of the changes necessary to achieve sustainability for Oahu and provides an example of an approach to thinking about the interconnected nature of sustainable solutions. However, to obtain a broader prospective for the United States similar case studies would have to be carried out for locations with different environmental constraints.

ACKNOWLEDGEMENTS

The class members wish to acknowledge the course instructors and guest lecturers:

Professor Frank Kreith, Course DirectorPaul Norton, retired Senior NREL EngineerAssociate Professor Susan KrumdieckDr. Rita KleesDr. Gary PawlasProfessor Emeritus Albert BartlettProfessor Emeritus Ronald WestDr. Debby Lew, NREL