Low Energy System Design

...Download this Sketchup Model..

This system has two radial filters and a media bed to keep the deep water culture raft very clean, An airlift pump keeps the water moving via an air compressor; no mechanical water pumps are required

Water levels in all the tanks are the same. By not raising the water from a sump tank only a small amount of energy is required to move the water laterally.

If this entire system were buried flush with the ground the thermal mass of the earth would help regulate the temperature very well during both summer and winter 

Airlifts  provides both water circulation and aeration. I believe airlift pumps can be more efficient than an external pump.  (Ive never understood why submersibles are always less efficient, but the specs tend to indicate this).
Airlifts can be calculated.
This article Performance Study of an Airlift Pump with Bent Riser Tube presents an interesting conclusion is that bends in the riser pipe do not effect the performace of an airlift pump.
OPTIMIZATION OF A BACKYARD AQUAPONIC FOOD PRODUCTION SYSTEM
is a very good paper about aquaponics and it would be a very good source for information about airlift pumps but a critical table is missing.  Id still recommend reading it for everything else it presents.



I found this calculator for airlift pumps.  It is spot on against the real life experiments Ive conducted.

From my own experiments without math; I believe an airlift will provide enough water circulation.  That is also what Keith Tatjana demonstrates in his paper in which he assumes a circulation rate of one fish tank volume twice per hour.
I think air blowers are more reliable than water pumps, and less expensive.  Blowers do not provide the pressure like a compressor so this is a limiting factor when using a blower, but if at all possible use an air blower because air compressors like the Hydrofarm 70 and 110 lpm units tend to vibrate themselves to death.
I have not done any experimentation with how much ambient air temperature will affect the water temperature, but logically this would occur whether it be from an air stone or an airlift pump.
Other papers Ive found are

Performance Characteristics of Airlift Pumps withVortex Induced by Tangential Fluid Injection

Explore the Potential of Air-Lift Pumps and Multiphase   Explore the potential of air-lift pumps  A geyser pump, an improved airlift pump The Geyser Pump improved the amount of water pumped from 40 gpm to 60 gpm in one experiment I conducted.   This Video shows the Geyser Pump I built. http://youtu.be/ztHBHULkHNQ

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Energy

I began this aquaponics project [Click Here]  with a goal to create an energy efficient system and explore the viability of a commercial system.

On March 8th I added a water heater and have maintained the temperature between 72F - 80F.  My utility bill begins and ends on the 20th of each month, so the heater was added midway through the cycle. 

The tanks are well insulated R11 and the grow room is insulated at R19.  The heater was only required several hours a day.  The weather has been slightly warmer than normal, but many days were near freezing and the glazing is not finished so I have a fair amount of infiltration.

All of these variables detract from an accurate assessment, but it is my conclusion that the cost of maintaining the heat for tropical fish and an ideal grow bed temperature is adding about 120 KWH/month or $34/month during the winter.

Recently my efforts have been to cool rather than heat.  Im using an evaporative cooling system which consumes about 180KWH/month at a cost of about $50/month. 

My plants were lanky and pale, so on March 18 I added 270W of supplemental lighting, and they have improved.   I have also added one more light for the duck weed bringing the total to about 300W.

I have been running the lights for 18 hours a day which is consuming about 5.4KW/day.  This additional usage pushed me into the next tier and adds an extra 4 cents per Kilo-Watt, but Ill use my average cost of $0.28/KWH for these calculations.  Id estimate the supplemental lighting adds about 160KWH/month or $45.00/month.  I will reduce this or discontinue supplemental lighting when the long Summer days arrive.

In order to reduce costs  Ill look into solar or propane heating, and I may be able to reduce the hours I supplement light or find a better glazing design.   Currently I have 40 sq ft of South facing vertical glazing in front of 25 sq ft of grow bed.   Direct sunlight is cut short by the winter season as well as the solid insulated walls and ceiling.  

In addition to lighting and temperature control the pump also consumes about 36KWH/month or about $10/month and tank lights at about 16KWH/month or $4.50

Adding this all up I get
$40.00 - Temperature Control
$45.00 - Lights
$10.00 - Pump
$ 4.50  - Tank Lights
$99.50 - Total utility per month.  

I feel the options are:

1. Find a way to direct more light onto the grow bed
2. Build additional grow beds outdoors for use only in the Summer
3. Experiment with less supplemental lighting to find the minimum amount required.
4. Change my crop seasonally and switch to cold water fish.

I am currently running the indoor grow room as well as a pond and have begun construction of an outdoor cold water aquaponic system using IBCs.  I should be able to compare the costs and production in a few months, but it seems obvious to me that the only way to make aquaponics cost effective is to raise fish that are adapted to your climate and plant seasonal crops.

Even without the additional cost of supplemental lighting my costs would still be about $50.00/month.  That is probably a break even point considering the cost of food and other items such as test kits.

I have enjoyed doing this and will continue to look at it as a $1200/year hobby with food as a benefit.

Additional advancement may come from recent technology as found in these links

Solar Grow Tube 

Inteligentry

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The Great Energy Challenge

Today 9 households around the world start their energy diet.

Mine is not one of the 9 being featured in National Geographics 360º Energy Diet, but Ive signed up.

Here are the points one can earn in each of six categories (Goods, Food, Transport, Home, Water, and Waste). Ive colored the ones Im already doing green, the ones Im not yet doing red.

1) GOODS

15 points each

• Tally your water, electric, & gas use and calculate how you could cut CO2
  
• Switch to organic for three produce items you regularly buy
  
• Switch to natural/eco-friendly cleaning methods for three tasks
  
• Switch from an imported non-produce item to a version produced locally

10 points each

• Swap disposables that you regularly buy for reusables (e.g., cleaning wipes)
  
• Repair or extend use of clothing items rather than buying new ones
  
• Use old printer paper/magazines/retail shopping bags, etc. for wrapping paper
  
• Rent or borrow an item that you rarely use, such as a drill or steam cleaner

2) FOOD 15 points each

• Eat a vegetarian diet one day a week
  
• Eat at home or brown-bag it at least once per week
  
• Limit daily intake of beef to 8 ounces per person
  
• Only consume seafood that has been sustainably raised and fished

10 points each

• Start a food-based garden (hurray for aquaponics)
  
• Go vegan or raw one day per week
  
• Buy grass-fed beef instead of conventional
  
• Give up one processed food that you normally eat

3) TRANSPORT 15 points each

• Drive no faster than the speed limit, and avoid rapid acceleration/braking
  
• Remove extra weight from your car and inflate tires to the proper pressure
  
• Use public transportation instead of your car at least once a week
  
• Reduce planned air travel by one trip

10 points each

• Buy carbon offsets for your travel
  
• Carpool or find a ride-sharing program
  
• Switch to a more fuel-efficient car

4) HOME 15 points each

• Turn heat/AC off when gone & change the thermostat by 3 ºF to reduce fuel use
  
• Set frig to 37 ºF, freezer to 0 ºF, water heater to 120 ºF and washer to cold
  
• Replace at least one third of your light bulbs with CFLs or LEDs
  
• Disconnect TV, stereo, and computers and other electric devices when not in use

10 points each

• If you have a second old refrigerator in your house, get rid of it
  
• If your refrigerator is > 10 years old, get a new one with a top-mounted freezer
  
• Insulate your water heater
  
• Replace appliances with EnergyStar appliances
  
• Hang clothes up to dry instead of using the dryer
  
• Seal all windows and doors in your home with caulk or weather-stripping

5) WATER 15 points each

• Give up bottled water for filtered tap water
  
• Turn off the tap when brushing your teeth or scrubbing dishes
  
• Shortening your shower by one minute or more. If you bathe, switch to showers
  
• Replace shower head or tap with a low-flow model

10 points each

• Use xeriscaping for your yard and avoid thirsty plant types
  
• Install a rain barrel to collect water for garden, lawn and plants

6) WASTE 15 points each

• Recycle all glass, aluminum, plastic, paper, batteries, and CF lightbulbs
  
• Eliminate junk mail by taking yourself off their mailing lists
  
• Change to paperless billing for bank account, credit card and bills
  
• Eliminate the use of plastic and paper bags, both when shopping and at home

10 points each

• Begin composting at home
  
• Using biodegradable bags for walking the dog if the family has one
  
• Recycle old athletic shoes and clothes
  
• Recycle or donate old computers, cell phones and other electronics
  

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Food and Energy in the Cold Northeast

The Cold Northeast Regions of China and the United States
Point A: Shenyang, Jilin, China
Point B: Plymouth, Massachusetts, United States

I found a delightful report the United Nations put together in 1994 on how to produce crops and energy in the cold northeast (42 degrees north of the equator). Its got a wealth of information on topics from methane production to solar homes and greenhouses, and integrated plant/animal ecosystems.

Its also chock full of charts and graphs and experimental results.

The full title is "Integrated energy systems in China - The cold Northeastern region experience."

Happily, the cold northeastern region of China is eerily similar to the cold northeastern region of the United States - same latitude, near an ocean, and populated by millions of folks who like to eat and stay warm.

I particularly liked the documented results from the experiments comparing Subterranean heating/Cooling Systems or Underground Heat Exchange Solar Greenhouses (UHESG) to Conventional Solar Greenhouses (CSG). The 1980s-era researchers document greater than 50% improvement in yields (in both weight and money value) for UHESG over CSG.

The English in the report is a bit awkward and laden with engineer-ese, but there are plenty of great ideas for those of us who have uncomfortably cold winters.

[Post Script - Latitude isnt the only story. The hardiness zone in Shenyang is between 4 and 5, while the hardiness zone of latitudinal twin Plymouth is an ocean-warmed 6. Due to the Gulf Stream, London enjoys a hardiness zone of 9, though it is almost 10 degrees further north than either Shenyang or Plymouth. Id have to travel south to Florida to get to a hardiness zone of 9!]

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Ten Calories Of Energy To Produce One Calorie Of Food

I just read the article  "The Permaculture Solution – an Interview with Warren Brush". It said "Estimates are that the modern agriculture system uses ten calories of energy to produce one calorie of food."

Fearing that I too may be growing negative net energy food. I immediately looked at the energy costs involved with my soil-less gardens. My hydroponic pump uses 160 watts-hours per day or 137.6 KCal or about 576 KJ/day.   Chris Carr was kind enough to remind me that nutritional calories (KCal) are equal to 1000 chemistry calories (cal).    A chemist would probably use Joules and Kilo-Joules (KJ) rather than KCal.   But the we think of food in terms of KCalories rather than Joules, so Ill keep it in KCal also known as large calories as much as I can.  There were other errors in my first draft,  so heres the rewrite.  Many of my calculations will be done using the Energy and Work Unit Conversion at unit-conversion.info/energy.html. 

I did some research and found a daily harvest of 8lbs of lettuce and 100lbs of tomatoes to be respectable averages for a 100sf garden. So I will be using those figures throughout.
Just for grins lets say you irrigate 100 square feet of garden with 10 gallons per day, and you are pumping water from lets say 100 feet below the surface. 

To calculate the power used to pump 10 gallons per minute 100

P_whp = q h sg / 3960

where

P_whp = water horsepower (hp)
q = flow (gal/min)    = (10)
h = head (ft)              = (100)
sg = specific gravity = (1)

P_whp = 10x100/3960 = .2525whp = 0.04497210699688 KCal/sec
This could also be expressed as 188.2892175745  J/sec which is the definition of a Watt.

If you are following along and checking my math you can use the Power Unit Conversion to find the Power.
Power and Energy are different.  Energy is what is delivered and Power is the rate at which it is delivered.
In the above example we deliver 188 Watts for 10 minutes or 31.38 Watt-Hours



We pump for 10 minute so
0.04497210699688 KCal/s  x  600sec = 26.9 KCal
So how many lbs of vegetables would you need to produce 26.9 KCal
Lettuce is 67.37 KCal per lb so you would need 26.9/67.37 = 0.40 lbs of lettuce per day from your 100 sq ft garden. If you harvest 8lbs / day the net gain is 19.97 times
Tomato is 80 KCal per lb so you would need 26.9/80 = 0.34 lbs of tomatoes per day from your 100 sq ft garden  If you harvest 100lbs / day the net gain is 296 times

Below is a list of common vegetables which I got from http://www.freedieting.com/tools/calories_in_vegetables.htm


Lets put this in perspective of a soil-less aquaponic or hydroponic system:
Lets say you use a 20 watt pump 5 hours a day.
    Thats 20 watt-hours x 5 hours/day = 100 Watt-Hours / day  (W-Hr/day)
    Each W-Hr is equal to 0.859845227859  KCal so you spend about 86.0 KCal to pump water each day.

If you grow 8 lbs of lettuce per day on your 100 sq ft aquaponics garden,
8lb/day x 67368 cal/lb = 538944 cal/day or  ,  538.944Kcal/day

You would spend 86.0 KCal to pump water to produce 538.944 KCal of lettuce.
A return of over 6.27 to 1.  Not quite 19.97 times like soil gardening but pretty good!



How about tomatoes...
Lets say you grow 100 lbs of tomatoes per day in your 100 sq ft garden.   
Let also say you use the same amount of electricity - (86.0 KCal/day).
100 lb/day x 80 KCal/lb = 8000 calories/day
So you would spend 86.0 KCal/day to produce 8000 KCal of tomatoes.
A return of over 92 to 1.  Soil gardening was 296 but this is not bad!

Compared to soil gardening the power efficiency is not as good, but water is also a commodity worth preserving and my guess is any of the soil-less methods will beat soil based gardening several times over.   It gets pretty complicated if you consider that some of the water applied to soil returns to the aquifer but ponics are definitely more efficient with water.  

Back to my hydroponic system which consumes 137.6 KCal per day.  It would need to produce 1.72 lbs of tomatoes per day.  But this is just the power used to move water.  Warren Brush was including the power used to make fertilizers, mine, and apply nutrients, and maintain the crop from start to finish.  Thats beyond the data available to me, but at least it still looks like a positive net gain whether you are gardening with soil or without and probably far better than the modern agriculture system using ten calories of energy to produce one calorie of food.

Aquaponics has a side benefit of fish protein which I have not included, but the energy used to make fish food should be considered.  Bioponics on the other hand is free of any further input save iron and magnesium which is also required in aquaponics.


Ill admit this article was difficult for me,  I feel like I have dyslexia where it comes to keeping units straight.  If you find any errors I will correct them, but to my best knowledge I have presented this correctly.

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Water Storage

As water becomes more difficult to obtain we are going to be forced into looking for better solutions.
This is a section of a modular water wall.

I did a quick search and others are also thinking along these lines and some of the walls are very decorative.  The idea of free or cheap drums is admirable but they are not large enough nor are they aesthetic.
 
Its time to think outside the box.  What about large reservoirs of water under our houses or hidden within our walls which would also be used to moderate temperature with its thermo-mass.

I used to live in a very old house in downtown Tucson.  The walls were built of adobe and they were nearly 3 feet thick.  The hot Tucson summers were quite bearable due to the thermo-mass of these walls even though I had no air conditioning.

If we were to build houses like this our energy and water consumption would both drop.  A stucco finish would make the walls look like any other house except for thick walls, and the comfort would be amazing.  This water could be collected during the rainy season and used later in the hot dry summer months to grow food and ensure a beautiful cooling landscape.

.
A family of five uses  about 1 acre foot (about 325,000 gallons) or (1225 m³) of water a year.  So saving water from your roof top may only make a small difference, but small differences add up.   Right now it costs about $1000 to process that much water from waste water or to build a new reservoir.  

Desalination has been done in other parts of the world and California is going to build a desalination plant in San Diego capable of 50 million gallons (189000 m³) a day.  But the cost is probably going to be twice the cost we are used to.  There are also concerns that the plant will kill fish, but efforts are being incorporated that should solve this problem.

In total fifteen desalination projects using reverse osmosis are proposed along the coast from Los Angeles to San Francisco Bay.  In the past many other desalination plants have been closed due to the high cost of operation.  The plant will use an enormous amount of energy -- about 38 megawatts, enough to power 28,500 homes.  
The efficiency works out to be about 3 kWh for 1 m³or 88 gallons / kWh fresh water.  Sounds like a lot of water, but the reality is this will only provide about 7 percent of the total water needs of San Diego County.   

Another problem I see is that this is going to be privately owned.  I would prefer to see communities own their own water source.

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Energy Audit

Im writing this to get my head around what Ive just found out.  I hope it provides you with food for thought.

Ive noticed our electric bill climb as I continue to add to my aquaponic systems, so using a Watt meter I did an energy audit .  
The first thing to surprise me is the cost of moving air.   Im using a whole house fan and a 20" box fan.  Both use more than I expected.  The whole house fan consumes 530W, and the box fan 90W. 

My submersible pumps are not too bad for submersibles, but one is not as large as I would like.
The Alpine Hurricane 2400 GPH is drawing 129W.  It is delivering 1750 GPH at 4 foot head.
The undersized No Name pump I am using in the outside IBC system is drawing 20W and delivers 268 GPH at 4 foot head.


Expanding the grow beds in this IBC system is going to require a larger pump, so I just purchased an AZFlo 2400/4000 External Pump for 299.00.  It will deliver 1900 GPH using 105W at 4 foot head..  This is 20W less than the Alpine Hurricane delivering 1700 GPH.  If I were to replace that submersible with this external pump I would break even in 5.7 years.

Now heres something I find interesting.  Pump power usage is non-linear. These tables show as head increases GPH decreases as would be expected, but the Watts seem to peak around the midpoint of maximum head. 

I have also have a Sequence 3600 700 series pump on my pond.  139W delivers 2820 GPH at a 4 foot head.  As you can see the external pumps are a lot more economical.

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