Memo

Date: November 18, 2014To: Ms. Effie Turnbull-Sanders

Governor’s Appointed CommissionerCalifornia Coastal Commission

From: Kyle RunionChristian NgAditya Srinivas

Subject: Recommendation Report for Researching Solar-Powered Desalination Plants in the San Francisco Bay Area

Attached is the report for our study, “San Francisco Desalination Plant Proposal.” We have completed the tasks in our proposal from October 7, 2014: identifying water needs and infrastructure logistics in the San Francisco area, identifying and selecting solar and desalination units and manufacturers, designing the system, and finding the feasibility of the project.

We conducted primary and secondary online research to perform these tasks. Water needs, locations, and technologies were reviewed. Contact to various manufacturers was attempted but did not come to fruition. There was ample published research online to sufficiently learn and report about solar-powered desalination.

Our findings show that San Francisco is a strong candidate for solar-powered desalination plants. Located in a coastal area currently experiencing drought, solar-powered desalination using concentrated solar stills and solar evaporation desalination would likely prove to be a successful project.

On the basis of these findings, we recommend that our system be built. Though we were limited to a preliminary cost analysis, our proposed system is less expensive than a previously proposed desalination plant that does not use solar energy. There is certainly a need for freshwater in the area and our project is the most effective solution.

We appreciate the opportunity you have given us in inviting us to research this proposal, and we look forward to working with you in other sections of the study as well as any related future study. If you have any questions or comments, please contact Kyle Runion at kylerunion@gmail.com or 975-3121.

Researching Solar-Powered Desalination Plants in the San Francisco Bay Area

Prepared for: Professor Daniel Saalfeld, Professional Writing InstructorUniversity of Maryland

Prepared by: Kyle RunionChristian NgAditya Srinivas

December 4, 2014

Table of Contents

Abstract

1Executive Summary

2Introduction

4Research Methods

8Task 1. Identify current water needs in the San Francisco Bay Area

8Task 2. Identify land in SF bay area that would be viable to build the plant

8Task 3. Identify water source and transportation

8Task 4: Find energy usage of desalination plant

9Task 5. Identify solar system to be used (array vs. concentrated, etc.)

9Task 6. Identify desalination technique to be used

10Task 7. Establish criteria to evaluate different manufacturers

10Task 8. Choose manufacturer of panels

10

Task 9. Determine number of panels

10Task 10. Design solar and desalination system

11Task 11. Determine equipment needed

11Task 12. Determine number of plants needed and identify locations

11Task 13. Cost analysis

12Results

13Task 1. Identify current water needs in the San Francisco Bay Area.

13Task 2. Identify land in SF bay area that would be viable to build the plant

13Task 3. Identify water source and transportation

14Task 4: Find energy usage of desalination plant

15Task 5. Identify solar system to be used (array vs. concentrated, etc.)

16Task 6. Identify desalination technique to be used

17Task 7. Establish criteria to evaluate different manufacturers

18

Task 8. Choose manufacturer of panels

19Task 9. Determine number of panels

21Task 10. Design solar and desalination system

21Task 11. Determine equipment needed

23Task 12. Determine number of plants needed and identify locations

24Task 13. Cost analysis

25Conclusions

26Recommendations

28References

28FAQ’s

31FiguresFigure 1

4Figure 2

12Figure 3

13

Figure 4

16Figure 5

19Figure 6

21Figure 7

21Figure 8

22Figure 9

23

Abstract

Researching Solar-Powered Desalination Plants in the San Francisco Bay Area

Prepared by: Kyle RunionChristian NgAditya Srivinas

On October 7, 2014, a research proposal for solar-powered desalination plants in the San Francisco Bay area was devised by three students at the University of Maryland. San Francisco and much of the southwest United States has been experiencing a drought and shortage of freshwater. With population increases and the rise of climatic instability through climate change, a sustainable source of freshwater is needed to supply for the city. Through research of the city’s water needs, possible locations, technology, and a cost analysis we attempted to create a feasible solution. We found that though the water usage in San Francisco is very high, it has been relatively low per capita recently due to water conservation efforts. A system consisting of concentrated solar stills and solar desalination units in Half Moon Bay near Pillar Point Harbor about 15 miles south of San Francisco could supply a large percentage of San Francisco’s freshwater. We recommend that a 500 module system be built in this location with the water to be transported to the city via pipes. This project is based on sustainability and follows that attitude wherever applicable, and should be a popular decision for San Francisco’s water shortage.

Keywords: San Francisco, solar power, desalination, Half Moon Bay, water, drought

1

Executive Summary

On October 16, 2014, we began to research the benefits of implementing solar-powered

desalination for the city of San Francisco.

Since the December of 2011, California has been experiencing a steady and precipitous drop in

rainfall, resulting in one of the state’s largest droughts since the late eighties and early nineties.

According to the Western Regional Climate Center, California’s average rainfall has been far

below that of the United States for the past year (10/1/2013 – 9/30/2014) (Climate Anomaly

Maps and Tables). Cities such as San Francisco only had around a quarter of the average

precipitation of the country. This has not only been a detriment to residents in the city, but also

an event poised to cripple the farmers of the area. While people in the city are being ordered by

the government to cut back on water usage, the lack of rain is forcing farmers to either pump

groundwater from wells or buy fresh water from local suppliers. Unfortunately, pumping

groundwater which not being replenished by rainfall is causing the ground to steadily sink,

putting a pin in any development programs in the area. To top it off, both methods of acquiring

water involve hefty costs. In order to keep up with rising costs, farmers have had to reduce the

amount of the crops that they grow, causing food prices to rise. With California being one of the

most productive agricultural regions in the United States, this dilemma extends to the rest of the

country and some parts of the world as well.

We focused on the city of San Francisco as we researched the practicality and feasibility of using

multiple small-scale solar-powered desalination plants, which would provide fresh water to the

city. It has been proposed to build a plant in the Bay Area; however, this plant would incur

around $150 million in setup costs alone and use plenty of energy operating. Solar-powered

2

plants could cost less, use less energy, and be self-sufficient. As we conducted our research, we

investigated the needs of the population, the most efficient solar system to use, the most effective

desalination technique, and the potential cost-savings of solar power.

We immediately found that it would be more cost-effective and efficient to purchase solar-

powered plants from a company known as WaterFX. The plant module is called an Aqua4, and it

uses a process called multi-effect distillation to separate the water from the brine. One module

only requires about a seventh of an acre and is estimated to cost around $292,500 (“FAQ”).

While we determined its energy use to be nearly 40 kilowatt-hours per cubic meter of freshwater

generated, this calculation did not account for the fact that the Aqua4 recycles waste heat. We

decided that Half Moon Bay would be the best location for a system of these modules and found

that 1250 plants could fit in the area. This was plenty of space considering we only needed 589

to satisfy the population of San Francisco. We decided, however, to cap the number of modules

at an even 500 in order to account for any obstacles (sidewalks, small facilities, etc.); this would

still provide a substantial amount of freshwater to the city.

Upon review of our findings and conclusions, we recommend the building of multiple small-

scale solar-powered desalination plants for San Francisco in the Bay Area.

3

Introduction

Since the December of 2011, California has been experiencing a steady and precipitous drop in

rainfall, resulting in one of the state’s largest droughts since the late eighties and early nineties.

According to the Western Regional Climate Center, California’s average rainfall has been far

below that of the United States for the past year (10/1/2013 – 9/30/2014) (Climate Anomaly

Maps and Tables). Cities such as San Francisco only had around a quarter of the average

precipitation of the country. It is estimated that around 80% of the state is in extreme drought

(Climate Anomaly Maps and Tables). As this drought enters its fourth year, it shows no signs of

ending.

Nov-0

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Average Monthly Discharge for Pilataros Creek in Half Moon Bay, California

Mean Monthly Discharge

Date

Dis

char

ge (c

fs)

Figure 1, Average Monthly Discharge for Pilantaros Creek in Half Moon Bay, California (U. S. Geological Survey).

As shown in Figure 1 above, the average monthly discharge in Pilantaros Creek, California has

been dropping recently. Discharge can measure precipitation by measuring the changes in the

discharge of a river or creek. With no water from precipitation, a creek will be at what is called

4

baseflow. This is the low flow experienced when the creek is only fed by groundwater. Any

additional water then can be attributed to precipitation. A major effect of the drought can be seen

late in the graph, in January 2014. This is normally a wet time of the year for Pilantaros Creek,

but the average discharge has a low peak through April 2014, the last recorded date. Without this

influx of water in early 2014 to be collected and recharge local aquifers, the past year has

experienced major drought through the dry season.

We intend to focus on San Francisco as we research a potential solution to this climate disaster.

The biggest problem with the absence of rainfall is the lack of fresh water. Farms, residences,

and even office buildings in the financial district require it. As farms suffer, the supply of fresh

food is further diminished. While farmers have found temporary solutions in pumping

groundwater or buying it from local suppliers, this has severe repercussions as well. Pumping

groundwater is causing the ground to steadily sink. One water supplier in Los Banos depends on

a dam to supply water to canals and then to customers; in five years, however, the dam has sunk

around three feet, meaning that the river is close to spilling over, resulting in even less water

(Fagan, California drought). If groundwater continues to be siphoned without being recharged by

rainfall, the land will continue to sink drastically, putting a pin in any development programs in

the area. The wells required to extract the water are also expensive to maintain, with costs

ranging well above $200,000 (Fagan, California drought).

Buying water is not much cheaper, if at all; about one year ago, farmers were charged around

$140 per acre by the Westlands Water District in Fresno (Vekshin). Now, however, they are

being charged $1100 or more per acre. Considering that many of these farmers have thousands of

acres of land, this can add up to a pretty hefty cost that could drive many farmers out of business.

5

Many of them are already being forced to reduce the number of acres that they regularly use.

This, as mentioned before, is decreasing the supply of food, thereby increasing the price.

California is one of the most productive agricultural regions in the United States, hosting 80,500

farms and ranches that offer produce such as beef, milk, fruits, vegetables, and rice (Vekshin).

These farms provide a sizable portion of the food that is consumed in our country, meaning that

this drought affects the rest of us as well. The US Department of Agriculture has predicted that

the prices of fresh fruit and dairy products will rise about 6% and 4%, respectively (Vekshin).

The farmers are not the only people suffering; residents in the actual city are struggling as well.

In response, Governor Jerry Brown requested people statewide to voluntarily reduce their water

consumption by 20% earlier this year (Steinmetz). Now, the drought is forcing the government to

finally institute largely unprecedented water usage restrictions to prevent people from wasting

water. San Francisco is mandating that users reduce their outdoor water consumption by at least

10%; doubling water rates on those who do not achieve this is also a possibility (Alexander,

“California drought…”). In fact, in the Bay Area city of Pleasanton, not adhering to the city

policy of reducing water usage can result in doubling (or even tripling) of bills. Throughout

California, fines of up to $500 can be imposed if residents (or organizations) are caught using

water to hose down driveways/ sidewalks, to decorate non-circulating fountains, or even to wash

their cars without a shut-off valve. This particular set of regulations will last for 270 days starting

July 29, 2014, though it is likely to be renewed until the drought show signs of receding

(Steinmetz). While San Francisco is late in administering these cutbacks, more stringent

regulations are likely to follow in response to the ongoing drought.

6

In order to solve the problem, in 2003, water agencies in San Francisco proposed the

construction of a desalination plant in the Bay Area; this would result in a massive and

welcomed influx of freshwater into the city (Fagan, Desalination plants). However, this plan has

drawbacks; the cost to build this plant is estimated to be around $150 million. This plant would

also require plenty of energy in exchange for the water, which would significantly increase

yearly costs in monetary and environmental terms (environmental costs come from extra

pollution). We wish to propose research of the benefits of constructing several small-scale solar-

powered desalination plants, which would, in theory, reduce costs and still provide sufficient

water. As we conducted our research, we investigated the needs of the population, the most

efficient solar system to use, the potential cost-savings of solar power, and the available fresh

water output of the system. Understanding these factors is vital in determining the practicality

and feasibility of this project versus that of a conventional desalination plant.

In the following sections, we further describe our research methods, our gathered results, the

conclusions we derived, and our final recommendation.

7

Research Methods

Task 1. Identify current water needs in the San Francisco Bay Area

It is understood that much of the Southwest United States suffers from water shortages. Finding

the current water needs and specific numbers on available water will helped us decide the size of

our desalination plant. Water prices will drop with a higher supply, so it is in our best interest to

supply water to a point where it is still profitable for us. We found the water needs by finding the

population of the area, researching industries and their water usage, and identifying current water

resources.

Task 2. Identify land in SF bay area that would be viable to build the plant

Water is expensive to transport, so a nearby location is vital for our proposal’s feasibility.

Specific area will be were found after the system design and size were determined. This section

of the research found primary sites before advancing in our research. Understanding that the

salinity concentration corresponds with higher operational costs, we wanted to find a balance

between transportation costs and input water quality. This was researched by looking through

Google Earth and following up with public records to see if the land could be acquired/leased.

We also considered to have our solar system and desalination plant in different locations, so if

one site is not suitable for both, then smaller, more remote locations would have been researched.

This option also included a need to research energy losses and costs through transmission, but

after initial research, it was found that this scenario was not necessary. Another option was to

have the plant(s) on a nearby island. This also proved undesirable as transportation costs were

high and land use was a troubling matter.

8

Task 3. Identify water source and transportation

We identified our water source and mode of transportation by first looking at all available

sources of water in the area. This mainly came down to aquifers, the San Francisco Bay, and

various rivers. The San Francisco Bay proved to be the most feasible option, as aquifers are

currently being used (and running dry) for water supplies. Rivers are often used for agricultural

irrigation and seeing as how supplies are unstable as it is, they would not be a suitable option for

our use. The Bay is a satisfactory source as it does not have an excessive salinity level and

contains an extremely large volume of water. The Bay also allows flexibility when choosing

specific sites for our plants as there is a large amount of shoreline, allowing for many different

locations.

Task 4. Find energy usage of desalination plant

Finding the energy usage of a desalination plant helped us to bridge the gap between energy

created and fresh-water provided. We needed to find the average energy usage of two different

types of desalination techniques: reverse osmosis, and solar desalination. This figure, along with

later finding exact outputs from our energy source, allowed us to adjust numbers in order to

make the project viable. The size of the desalination plant was then based on the water needs

previously found.

Task 5. Identify solar system to be used (array vs. concentrated, etc.)

Researching solar power systems allowed us to find the advantages to each type. Array and

concentrated solar systems were our main focus as they were found to be most realistic for our

project. Research was conducted on these technologies via manufacturer’s websites and

9

published research, and based on our size and cost constraints we decided on our type of

systems.

Task 6. Identify desalination technique to be used

After realizing there were multiple, viable, commercial-scale desalination techniques, we decided

we must research each in order to make an informed decision. Technical specification sheets and

review articles were used to weigh the pros and cons about both reverse osmosis and solar

desalination. Criteria to differentiate the two included energy usage and efficiency, brine

discharge composition, and ease of operation.

Task 7. Establish criteria to evaluate different manufacturers

Criteria must be established to be able to decide which manufacturer would be most efficient to

purchase and use. Through research of solar energy systems and desalination techniques, as well

as reviews of successful past proposals, certain criteria began to rise as vital to differentiate

manufacturers. It was necessary that this criteria be composed of the largest factors of success in

solar panels and desalination units for a successful project. After establishing this criteria, we

were able to begin to select certain products to propose for our desalination plant and find the

cost to benefit analysis.

Task 8. Choose type/manufacturer of panels

After deciding between an array and concentrated system, we started to focus on specific panels.

Research was done on both reflectors and thermal solar panels, the two popular options for

concentrated solar systems. This decision was based on the criteria mentioned in the Task 7.

10

Task 9. Determine number of panels

Our selection for the manufacturer made determining the number of panels very simple. The

panels are connected in a module and, with an attached desalination unit, can be rated in gallons

of freshwater produced a day. This simplifies conversions of energy and for our purposes,

produces the most efficient system possible. Our biggest constraints were cost and land

available. With enough available funds, this project could be scaled up to fulfill the entire city’s

water needs. We made a decision on number of panels based on providing a reasonable fraction

of the city’s needs and effective use of our land resources.

Task 10. Design solar and desalination system

After selecting the WaterFX Aqua4 solar desalination system, designing the solar and

desalination system was very simple. The Aqua4 is a complete, modular system, so it became

very flexible as to how to set the design. The size restraints were found and

Task 11. Determine equipment needed

Even though we had already chosen a specific, complete system, it was still important to learn

each part of this system to ensure we had a full knowledge of the system. This was done by

breaking down the system and researching each part. All parts of the system have been used

elsewhere for various applications, so literature was available to be found in places other than the

manufacturer’s webpage. This also allowed us to build our own similar system if the Aqua4

module was unavailable for some reason.

11

Task 12. Determine number of plants needed and identify locations

An expansion to our efforts in Task 2, we identified specific locations for desalination plants.

After knowing space and other requirements, we were able to hone in on certain areas and select

those that we thought would work well. As previously stated, there is no upper or lower limit to

the number of plants or modules, so we decided to select any location that would make sense

financially and logistically.

Task 13. Cost vs profit

Finally, we attempted to perform a cost/benefit analysis to determine our long term feasibility.

With some of our desired products in the pre-market stage, a cost/benefit analysis proved

difficult. We decided to stick by these products because while they may not be readily available,

they are without a doubt the most capable pieces of technology for our project.

12

Results

Task 1. Identify current water needs in the San Francisco Bay Area.

According to a map provided by the San Francisco Bee, in 2008 San Francisco County

consumed 108.4 gallons per capita per day (Williams). Currently, the San Francisco Bay Area

relies on water imported from the Sierra Nevada and Sacramento-San Joaquin Delta. These two

sources account for two-thirds of the water supply, however; they will not be able to keep up

with the growing population and increasing demand. Within the Bay Area are different water

agencies that control the distribution of water in their region as seen in Figure 1. Several of these

agencies are getting some of their water locally from sources such as the Mokelumne and

Tuolumne Rivers. However, this

accounts for only about 10% of their

water supply and these sources are

unreliable during drought. In accounting

for dry periods, these water agencies

store water in the ground, but with this

extended dry period, these ground basins

are being tapped out. Home to 7.44

million people, a number that is steadily

growing; the need for water in the San

Francisco Bay Area has never been

higher.

13

Figure 2. Major Urban Water Agencies in the Bay Area (“Maps of”)

Task 2: Identify land in SF bay area that would be viable to build the plant

San Francisco is a metropolitan area so finding a large area of land to build the desalination plant

on would be expensive and difficult so we chose an area right outside of the city. The area we

decided on is on the coast of Half Moon Bay,

particularly in the region near Pillar Point

Harbor as seen in figure 2. Only 15 miles

away from San Francisco, this beach town

would be suitable for the plant because of its

close proximity and the plants ability to blend

into the town. There are many piers and docks

in the town so the plant would fit in. The plant

we are constructing is not large so it would not

take up a huge amount of space and take away

from the town. Instead, we believe that the

plant would boost the town’s economy and give it a reliable source of income. The majority of

income for Half Moon Bay is based off tourism and the plant would provide yearlong jobs to

locals rather than the seasonal beach jobs.

Task 3. Identify water source and transportation

The water that will be used for the desalination plants will be retrieved from the Pacific Ocean.

Freshwater produced from our plants must be transported to the San Francisco Public Utilities

Commission which would then re-direct the water to the residents. We considered two sources

of transportation of the water: trucks and underground piping. Ultimately, we decided to go with

the underground piping because we determined that trucking would not be feasible due to cost.

14

Figure 3. Map of Half Moon Bay (““Map of Half Moon Bay”)

An underground piping system would be a large initial cost with little maintenance cost over

time while a trucking service would be a steady cost which would cost more in the long run. We

estimated that it would take about 25 miles of piping from our desired plant destination to the

San Francisco Public Utilities Commission. If one inch pipe is used from each of the 500

modules and connected to a water main, the water main would need to be 24 inch schedule 40

steel pipe. To install this water main for 25 miles, it would cost about $20 million for the pipe

itself and labor.

Task 4: Find energy usage of desalination plant

Every desalination plant, no matter how small, has a system of components designed to separate

salt from water, hence the name, “desalination plant.” There are a variety of methods we can use

to conduct the process of filtering; we are leaning towards a technique known as distillation (See

Task 6). This involves separating the water from the salt through evaporation. The main

advantage of this method is that it has a much simpler design and guarantees purer water than its

competitor, reverse osmosis. This method (reverse osmosis) has the water is pumped out of the

ocean and forced through a semipermeable membrane that separates the water from the salt. The

fresh water in both methods is then stored and distributed through a main into a water system.

According to a report from King Saud University, reverse osmosis plants use around 4-6

kilowatt-hours per cubic meter of fresh water (kWh/m3). The report also showed that distillation

plants use around 14-16 kilowatt-hours per cubic meter, which is a considerably higher amount

(Al-Mutaz). For the distillation plant data, we are using the electrical equivalent numbers, which

account for thermal energy as well. While reverse osmosis does use less energy, it also uses

much more complex parts, which have a higher probability of breaking down and require more

15

frequent maintenance. Distillation plants are inherently less complex and allow for better

packaging, due to the relatively low number of parts.

After plenty of consideration, we have decided that a system known as the Aqua4 would be the

most effective building block of our solution. The Aqua4, a product from WaterFX, is a small

desalination plant which uses solar panels to distill the seawater (as in the aforementioned

method). The obvious advantage of this is that the process of installing the plants would become

much simpler; we are purchasing stock of a single product. It also takes up about a seventh of an

acre which is a fairly small amount of space. The energy consumption is estimated at nearly 40

kilowatt-hours per cubic meter, but it also stores and recycles the excess thermal energy in steam

(Aqua4). It also runs entirely on the solar panels provided by WaterFX. We believe that this is a

viable option which would allow us to use a very compact space and minimize setup costs.

Task 5. Identify solar system to be used (array vs. concentrated, etc.)

While arrays of solar panels and concentrated solar power systems are both grouped into the

same category in solar energy, they are quite different. Solar arrays, a solar photovoltaic

application, are the common thought of solar energy, with grids of panels facing the sun and

converting sunlight into electrical energy. Solar panels can be used in small scale projects, such

as residential homes, or large scale, as a solar farm. Concentrated solar power systems, a solar

thermal application, work with mirrors to focus solar radiation and drive a steam turbine through

heat. This is more similar to our current large scale energy generation with coal (Covington).

Concentrated solar stills have been used through history for solar-powered desalination and still

prove to be the most efficient option (Solar Desalination - Clean water from solar energy, 1-4). A

concentrated solar still consists of an arc of mirrors aimed at a central pipe (Solar Distillation:

Technical Brief, 2).

16

Figure 4. Solar parabolic trough often used with solar stills (Parabolic Trough)

Water flows through this pipe and is heated until it flows to a storage tank and then to the

desalination unit (Solar Distillation: Technical Brief, 2). Alternatively, mineral oil, which can

more effectively collect and transfer heat, can be used in these pipes. The mineral oil pipe is a

closed system where it can run through a water tank and transfer heat (“Concentrating Solar

Power Thermal Storage System Basics.”) We propose to use concentrated solar stills in our

project design.

Task 6. Identify desalination technique to be used

The most popular type of desalination is currently reverse osmosis ("Desalination by Reverse

Osmosis"). In reverse osmosis, saltwater is put under pressure and the water and dissolved salts

are separated through a water-permeable membrane ("Desalination by Reverse Osmosis").

Though fairly simple, it is a very energy-intensive process. A newer method of desalination,

currently termed “solar desalination,” is based on evaporation. Water is heated and goes through

evaporation chambers, where it separates from salts and is collected (“FAQ.”). This process also

requires energy in the form of heat; this could be easily applied with our concentrated solar stills.

Instead of harvesting heat with the solar still to create electricity through a steam turbine, the

17

heat could be directly applied to the saltwater and used to promote evaporation. This makes solar

desalination a more attractive option for our project, as it allows conversions of energy to be kept

to a minimum, encouraging high system efficiency.

Task 7. Establish criteria to evaluate different manufacturers

With the selection of a concentrated solar still as our energy system and solar desalination as our

desalination technique, we must begin to decide which brand and manufacturer can best fit our

needs. A combination of quality and cost must be found to make our solution to the San

Francisco water troubles viable and worthwhile. Our criteria will include: cost, location of

manufacturer, applicability, energy consumption, discharge, and infrastructure.

Financially, this proposal must make sense. Single family residential buildings are currently

paying $4.86 per CCF (100 cubic feet or 748 gallons) of water (for the first four CCFs) (“Single

Family Rates”). By June, 2017, this price will be $6.42 (“Single Family Rates”). Non-residential

buildings in San Francisco currently pay $5.79 per CCF and will be paying $7.64 in 2017 (“Non-

Residential Rates). Should we recommend this desalination plant be built, it must be able to have

competitive pricing on water. Another pricing consideration we can make is the effect on

groundwater. San Francisco is currently using groundwater for their water uses at an

unsustainable rate. The state of California currently lacks groundwater regulations, but NASA

has found that nearby basins are running dry (Boehrer). This would require a more in-depth

study to find financial benefits of preserving the groundwater supplies, but we can acknowledge

that there certainly is an incentive to doing so. Location of manufacturer is a criterion in the

subset of cost.

Applicability is another aspect we must consider when evaluating manufacturers, in the sense

that the system must be able to collect solar energy efficiently. San Francisco receives an average

18

of 4.1-4.6 kWh/m2/day ("San Francisco Solar Map"). Though this is lower than most of the

California and Southwest U.S. region, it is at or above the average for the continental U.S.

("Solar Maps"). In order for our desalination plant to be successful, we must take advantage of

this solar energy with a solar system that can efficiently convert sunlight to heat or electrical

energy.

Energy consumption is a significant trait: the plant must have a low cost of energy in order to be

feasible. The solar system must supply sufficient energy to the desalination plant to keep external

costs low, and the desalination unit should use as little energy as possible while providing the

necessary quantity of a high quality output. This idea ties into the efficiency aspect, as in order to

keep costs low, a high efficiency is required.

Discharge, in the sense of the desired and undesired outputs, should be taken into consideration

as well. The desired output, freshwater, is obviously our main concern. Essentially all

desalination units on the market discharge extremely clean fresh water, so that will not be a point

of contention. Solar desalination, based on evaporation, is usually very efficient, with rates of up

to 93% (“FAQ”). This creates a smaller volume of salty wastewater, or brine, as compared to

reverse osmosis. The small volume of brine is more easily treated and has industrial uses as a

refrigerant or curing mechanism for seafood (Hilderbrand).

Infrastructure is our final criteria in evaluating manufacturers. In a highly populated city such as

San Francisco it is vital to make the most of the available space. Solar panels tend to use the

same amount of space per manufacturer, but space can be saved with the desalination unit. A

smaller unit, or one using vertical space more efficiently, will be favored.

19

Task 8. Choose type/manufacturer of panels

Located in the Central Valley in California (“Blog”), WaterFX is a local manufacturer to our

project site. Locality supports a theme in our project, sustainability, and is important to gain

support of citizens and officials in San Francisco. They also provide the type of solar system and

desalination unit we have chosen: a concentrated solar still and solar desalination (“FAQ”). A

single WaterFX Aqua4 solar desalination

module can provide up to 65,000 gallons of

freshwater per day (“FAQ”), which could

provide for over 1400 residents (Alexander,

“Amid drought…”), given their current water

conservation practices. The Aqua4 has shown

freshwater [of under five parts per million

(ppm) of total dissolved solids (TDS)] generation efficiencies of over 93%, with the 7% brine

being super concentrated with over 200,000 ppm TDS (“FAQ”). To give this concentration

perspective, freshwater is defined as containing under 1,000 ppm TDS, while sea water contains

30,000 to 40,000 ppm TDS (“Water Concentrations”). A very concentrated brine opens the

possibility for industrial use for the otherwise waste material, and at the very worst, a lower

volume of waste to treat/dispose of. The relatively small scale size of the Aqua4 of 6,500 square

feet will allow for flexibility on our part (“FAQ”). With modules being fully operational whether

there be a single or multiple, they can be placed on any piece of land we find close to a water

source. Even more flexibility is provided with the Aqua4 modules, as a single module is made up

of ten stages; modules can be scaled up or down depending on space and capacity needs

(“FAQ”).

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Figure 5. Solid salt composition from treated brine ("Blog")

Though this product seems perfect for our application, there are a few minor drawbacks.

WaterFX seems to be a very young company, with its first found mention online was published

in early 2014 (Kelly-Detwiler). The Aqua4 module is currently only available for lease, rather

than purchase (“Aqua4”). Depending on developments with the company, modules could be

leased to start to project, or the project could be delayed. With such a huge opportunity for

WaterFX, they may make the product available for purchase for this project.

Task 9. Determine number of modules

As found in Task 1, San Francisco Bay is home to 837,000 people (Alexander, “S.F.

Residents…”) with a consumption of 108.4 gallons of water per capita per day (in 2008)

(Williams). This works out to 90.7 million gallons of water per day. Within the current drought

in this past September, consumption per capita per day has dropped to 45.7 gallons (Alexander,

“S.F. Residents…”). With these conservation techniques, the city’s daily consumption drops to

38.3 million gallons per day. Hopefully these sustainable practices have been instilled in the

residents’ behavior and the per capita consumption stays close to 50 gallons per day. A single

WaterFX module can provide 65,000 gallons of water per day, meaning that with current water

consumption, 589 modules would be needed to completely satisfy the city’s water needs. This

may not be realistic, but seeing that a single module can provide for 1400 residents, even a small

number of modules can put a significant dent in the city’s water needs and reduce the need for

water imports. With the ample space found earlier in Task 2 and later in Task 11, we have

decided to propose a system of 500 Aqua4 modules.

Task 10. Design solar and desalination system

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With the complete modules from WaterFX, designing the system is relatively simple. The 500

modules will easily fit inside our target area in Half Moon Bay. Each module comes with a

desalination unit, eliminating the need for a large central desalination unit. Freshwater produced

can be collected into a holding container and piped into the city as needed.

Figure 6. Aqua4 Concentrated Solar Still

Figure 7. Aqua4 Desalination Unit

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Freshwater produced can be collected into a holding container and piped into the city as needed.

The pipe infrastructure will be expensive as our site is about 15 miles from San Francisco, but as

a one-time cost, it will be more cost effective in time.

Task 11: Determine equipment needed

Initially, when we were discussing our solution, we gave serious consideration towards building

our own plant. Even if we have decided that the Aqua4 is the best option, it is still necessary to

discuss what components it uses. This particular system uses a multi-effect distiller (MED) with

up to 10 effects. This uses multiple heating tanks so that any remaining salt water can move on to

the next tank until almost all of the fresh water has been harvested. According to the United

Nations Environmental Programme, the process starts off with a boiler, which is powered by the

solar panels. At least three pumps are needed: one to pump seawater into the heating tank, one to

pump steam into the initial heater, and one to pump remaining saltwater into the next effect

(stage); each added effect requires an additional pump. An MED can have any number of effects;

each one routes the newly separated freshwater down through the cold salt water of the next

effect (for cooling) and into storage. The unseparated saltwater from an effect is pumped into the

23Figure 8. Diagram of multi-effect distillation process (Al-Mutaz)

next one, where it is heated and separated again until the last effect, where the final distilled

water is released to the public and the brine (excessively concentrated salt) is disposed of

carefully. In summation, we would basically need a predetermined number of solar panels, a

boiler station, initial heater, any number of effects, and all necessary pumps; a relatively simple

system. If we do not end up using the Aqua4, we could design a plant with these components.

Task 12. Determine number of plants needed and identify locations

With approximately 7,000 linear feet of undeveloped shoreline ranging from 650 to 1750 feet

inland of open space at Pillar Point Harbor, there is ample space for more than enough plants to

supply for San Francisco (“Half Moon Bay”).

Figure 9. Viable land area on Half Moon Bay for the solar desalination plant ("Half Moon Bay")

The outlined space above

shows 8,150,694.73

square feet of coastal land

in Half Moon Bay (“Half

Moon Bay”). Without

accounting for specific angling and spacing issues, this is large enough for over 1250 modules at

6500 square foot/module. With ample space, we have chosen for the system to consist of 500

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modules. This will allow for the supply of most of the water San Francisco uses (with

conservation practices in effect). At peak efficiency, 3.25 million gallons of water per day can be

desalinated with this system. This additional influx of freshwater into the city will allow for

some drought restrictions to be lifted and for water scarcity to end.

Task 13. Cost analysis

Unfortunately, neither of the founders of the company was available for comment. As a result,

we have had to derive an estimation of the setup cost. The capital involved in the design and

building of a desalination plant is around $3.5 to $4.5 for the gallons of freshwater the facility

dispenses in a day (Banat). Given that the Aqua4 module generates around 65,000 gallons per

day and that our system is made up of 500 modules, we can say that the cost of building and

installing the system should be about $146.25 million (using $4.5 per gallon per day). This is $4

million less than the $150 million for the current proposed plant. The current prospective plant

also does not use solar power; the day to day costs run higher as the plant has to draw electricity

from a power grid. By comparison, solar power is not only an independent power supply, but it

also requires limited maintenance. The pipe infrastructure and installation would cost an

estimated $20 million, as derived in Task 3. This makes our proposal more expensive than the

actual current proposal, but with low maintenance and operational costs, ours should prove to

make more sense financially in the long run. It also allows us to split the pipe at any time and

spread our supply of water to neighboring regions if demand requires.

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Conclusions

In this section, we present our conclusions based on our research of the three main questions we

were asked to answer

Water Needs

The San Francisco Bay area is closing in on one year in drought status, and while conservation

techniques have worked well to reduce water consumption, additional sources of water still must

be investigated. In 2008, the water consumption per capita was 108.4 gallons per day in San

Francisco (Williams). This past September, consumption was recorded at 45.7 gallons per day

(Alexander, “S.F. Residents…”). While consumption is a great way to reduce the effects of the

drought, the current water usage is still unsustainable, mainly because of the water source. Water

is being pumped out a natural aquifer faster than the aquifer can recharge (Perlman). This leads

to the drainage of the aquifer and a loss of their water source. The rise in water needs can also be

shown by price increases: the price for water in both residential and non-residential buildings in

San Francisco is rising 32% by summer of 2017.

Available Locations

San Francisco, a large city, is likely not to have available land for development. Another

restriction is that any desalination plant must be located on the water, whether that be a bay or

the ocean. Luckily, nearby coastal locations are relatively rural compared to the city and do have

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open coastal land. An area in the city of Half Moon Bay, located about 15 miles from San

Francisco, has been identified as being suitable for a desalination plant development. Nearly two

hundred acres of land on the waterfront in Half Moon Bay are available for development. The

only drawback is the distance from San Francisco, but a one-time cost for a piping system will

sufficiently transfer the produced freshwater.

Technologies

Desalination is an aged proven process, yet there are multiple techniques emerging as potential

uses for drinking water. Reverse osmosis and solar desalination were researched to find the most

efficient process for this type of project. Solar desalination was found to be best suitable due to

minimal energy conversion losses. Another technology reviewed was solar panels. Options for

our solar energy system included arrays of photovoltaic panels or a concentrated solar thermal

system. Again, efficiency was the main factor in this decision, and concentrated solar thermal

was found to be more efficient. With solar desalination, heat is the main energy used.

Photovoltaics (PV) provide less heat than thermal panels as PV involves a conversion to

electrical energy while thermal does not. The piping system and distillation process were also

researched to fully understand a solar desalination system. After choosing these categories of

technology, a complete system of concentrated solar still and solar desalination unit was found in

WaterFX’s Aqua4. This is the most appropriate piece of technology for such a project.

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Recommendation

Based on our research, we recommend that a 500 module Aqua4 system be installed in the land

area mentioned in Half Moon Bay. This will provide a large fraction of San Francisco’s water

needs and though it will have no direct effects on the drought, it could be able to lift some of the

drought restrictions on water usage currently in place. This 500 module system could provide

water for 700,000 residents at peak efficiency and with the current water conservation

techniques. The project will have a large upfront cost but requires little maintenance and little to

no additional energy from the grid. Sustainability is a major theme in this project, and it’s

completion will allow the local aquifers to recharge and San Francisco to live more sustainably.

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Works Cited

Al-Mutaz, Ibrahim. Energy Consumption and Performance for Various Desalination Processes. Riyadh: King Saud University, 2008. Document.

Alexander, Kurtis. "Amid drought, water-use penalties hit Bay Area." SFGate 22 July 2014.Alexander, Kurtis. "California drought: San Francisco puts caps on watering." SFGate 12 August

2014.Alexander, Kurtis. "S.F. Residents Praised for Using Least Water in State." SFGate. San

Francisco Gate, 05 Nov. 2014."Aqua4." 2014. WaterFX. URL. 27 October 2014.Banat, Fawzi. Economic and technical assessment of desalination technologie. Jordan: Jordan

University of Science and Technology, 2007. Slideshow."Blog." WaterFX. WaterFX. Web. 30 Oct. 2014.Boehrer, Katherine. "NASA Satellites Reveal Shocking Groundwater Loss In Colorado River

Basin." The Huffington Post. TheHuffingtonPost.com, 24 July 2014. Web. 28 Oct. 2014.

Climate Anomaly Maps and Tables. 1 October 2014.<http://www.wrcc.dri.edu/anom/cal_anom.html>. (Primary)

"Concentrating Solar Power Thermal Storage System Basics." Energy.gov. U.S. Department of Energy, 21 August 2013.

Covington, Richard. "Shining Example." Smithsonian 41.4 (2010): 116-119. Academic Search Premier. Web. 28 October 2014

"Desalination by Reverse Osmosis." OAS.org. Organization of American States. Web. 27 Oct. 2014.

Drought in California. Sacramento: California Department of Water Resources, 2012.Fagan, Kevin. "California drought: As land sinks, farmers' brainstorm on water." SFGate 26 July

2014.Fagan, Kevin. "Desalination plants a pricey option if drought persists." SFGate 15 February

2014."FAQ." WaterFX. WaterFX, Web. 28 October 2014.“Map of Half Moon Bay” Half Moon Bay Coastside Chamber of Commerce and Visitor’s

Bureau. http://www.halfmoonbaychamber.org/“Half Moon Bay” 37°30’35.10” N and 122°30’19.99” W. Google Earth. 23 February 2014.

(Primary)Hilderbrand, K. S., Jr. Preparation of Salt Brines for the Fishing Industry. Publication. Oregon

State University, 1998. Web. 05 Nov. 2014.Kelly-Detwiler, Peter. "WaterFX Sees Solar Desalination As One Way To Address The World's

Water Problem." Forbes. Forbes Magazine, 7 Jan. 2014. Web. 06 Nov. 2014.Mapsof. 2014. Map. 15 October 2014."Non-Residential Rates." San Francisco Water. San Francisco Public Utilities Commission.

Web. 28 Oct. 2014.

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Parabolic Trough." Wikipedia. Wikimedia Foundation, 17 Nov. 2014.Perlman, David. "Sierra Rises, Quakes Erupt as Central Valley Aquifer Drained." SFGate. San

Francisco Gate, 5 June 2014. Rogers, Paul. "Nation's largest ocean desalination plant goes up near San Diego; Future of the

California coast?" San Jose Mercury News 29 May 2014."San Francisco Solar Map." San Francisco Solar Map. SFOG.us. (Primary)"Single Family Rates." San Francisco Water. San Francisco Public Utilities Commission. "Solar Desalination - Clean water from solar energy". Aalborg CSP. Practical Action. 25 August

2013."Solar Distillation: Technical Brief". engineeringforchange.org. 25 August 2013"Solar Maps." NREL: Dynamic Maps, GIS Data, and Analysis Tools -. National Renewable

Energy Lab. (Primary)Steinmetz, Katy. "Unprecedented California Drought Restrictions Go Into Effect." Time 29 July

2014.U.S. Geological Survey, 2014, National Water Information System data available on the World

Wide Web (USGS Water Data for the Nation), accessed December 3, 2014 at URL [http://waterdata.usgs.gov/ca/nwis/inventory/?site_no=11162630]. (Primary)

United Nations Environment Programme. "Water Quality Improvement Technologies." Sourcebook of Alternative Technologies for Freshwater Augmentation in West Asia (n.d.): 4.2.1. Website.

Vekshin, Alison. "California Water Prices Soar for Farmers as Drought Grows." Bloomberg 24 July 2014.

"Water Classifications." Water Classifications. Pacificro, n.d. Web. 06 Nov. 2014.“Who Uses How Much? California Waters by the Numbers.” San Francisco Sierra Club. Web.

06 Nov. 2014.Williams, Linda. "Willits Declares Phase 1 Water Emergency." Willitsnews.com. 16 Aug. 2013.

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FAQs

1. Where is water in the San Francisco Bay area currently being supplied from and why is it not sufficient enough?

In the bay area, water agencies are assigned regions in which they supply fresh water to. These agencies are only recently having trouble with keeping up with the demand because their stored water in ground basins are going dry due to the prolonged drought.

2. How long has the drought in California lasted?

California is amidst one of most severe droughts in state history. Rainfall has been steadily dwindling as of December 2011.

3. How does California’s drought affect other regions?

California is one of the United States’ largest agricultural suppliers, home to a diverse range of produce. As the farmers there struggle to grow crops, food prices go up, and the nation pays.

4. What is a desalination plant?

A desalination plant uses either distillation or a porous membrane to separate freshwater from a saline solution.

5. How old is the process of desalination

Desalination is possibly mentioned in the Bible, and the first recorded act of desalination occurred in 1684 in the UK.

6. What is solar desalination?

Solar desalination is a type of desalination that uses distillation to separate dissolved solids from water and then catches the fresh water for potable uses.

7. What is distillation?

Distillation is involves heating up a mixture containing water to boiling point. This means that the water evaporates and leaves any contaminants (like salt) behind.

8. What is a concentrated solar still?

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A concentrated solar still is a solar thermal system where a parabolic trough shaped solar panel collects heat by reflecting photons to a central point or pipe, where water or mineral oil runs through and can transfer heat.

9. What are kilowatt-hours?

A kilowatt-hour is a unit of energy equal to one kilowatt (kilojoule per second) of power dissipated for one hour.

10. Why is a desalination plant needed?

Due to the drought, various regions of the state of California have been running out of freshwater. Freshwater is needed for farming and consumption purposes.

11. Who is WaterFX?

WaterFX is a company founded by Aaron Mandell and Dr. Matthew Stuber. It is devoted to designing affordable solar-powered desalination systems.

12. What is Aqua4?

The Aqua4 is a small solar-powered desalination plant designed and produced by WaterFX. It uses a multi-stage distiller to generate freshwater.

13. How large is the Aqua4 module?

The Aqua4 module is 6,500 square feet (160 x 40ft)

14. How much freshwater can a single Aqua4 module provide?

A single Aqua4 module can provide 65,000 gallons per day of freshwater from a brackish or seawater input.

15. How often will the Aqua4 module run at peak efficiency?

Well above the U.S. average for sunny days in a year at 259 in San Francisco, we can estimate that the system will run near peak efficiency for much of the year. Even days not categorized as sunny days will still provide energy and a lower output of desalination, as photons are still hitting the panels.

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16. How can the brine output be used industrially?

Once collected and condensed to a solid phase, the brine output can be used as industrial salts would in various applications such as meat curing.

17. Where is Half Moon Bay?

Half Moon Bay is a coastal city in San Mateo County, California. It is located about 15 miles south of San Francisco. The Half Moon Bay body of water is located off of the Pacific Ocean.

18. What makes Half Moon Bay a suitable area to have a desalination plant?

Half Moon Bay is a town 15 miles away from San Francisco that with a coastline in the Pacific Ocean. This beach town has a harbor and an Air Force base near where we plan to build our plant which is why we feel that it will fit in.

19. Will a desalination plant provide enough fresh water for the region?

Desalination plants theoretically could provide fresh water for the region, but for the most part it is an unsustainable practice with regards to energy consumption. Solar desalination changes that, but it is still not efficient enough to be relied on as the only source of water.

20. What defines salt water?

Water’s salinity is based on the number (measured in parts per million) of total dissolved solids (TDS).

Water Classification ppm TDS

Fresh < 1,000

Brackish 1,000 - 15,000

Saline 15,000 - 30,000

Sea 30,000 - 40,000

Brine > 40,000

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