aquaponic system

Solar Aquaponics Designing a 100% Solar Aquaponics Greenhouse

Dan Chiras, Ph.D. Director, The Evergreen Institute Gerald, MO 63037 www.evergreeninstitute.org

 Creating a 100% solar operation

 Efficiency First!

 Solar electricity – lighting, water pumps, and aeration

 Not resistive heating!

 Solar thermal – heating water

 Passive solar heating and cooling

Topics

Understanding

Solar Energy

The Sun  Earth orbits around the sun

 Completing its path every 365 days

 Earth’s orbit is elliptical

 Distance from the Sun varies

 Earth is closest to the Sun during the winter

 Farthest from the Sun in the summer

Understanding Solar Energy

From Jim Dunlop, Photovoltaic Systems, ATP

From Jim Dunlop, Photovoltaic Systems, ATP

From Jim Dunlop, Photovoltaic Systems, ATP

The Sun’s Path

 Position of the Sun changes during the year  As a result of the changing relationship

between the Earth and the Sun  Sun “carves” a high path across the summer

sky  Reaches its highest point on June 21  June 21 = longest day of the year  Aka the Summer Solstice  Sun carves a low path across the sky on

December 21  Shortest day of the year  Winter Solstice

Solar Window

Solar Electricity

Solar Electricity -- Photovoltaics

Photo = sunlight

Voltaics = electricity

PV cells, modules, and array

 Lots of options  Easiest of all  Install a PV system on

your home  Simply plug in  If aquaponics system is

on its own meter  Can install a PV system

to supply it  Wire it into the panel  Add batteries for

backup

How to go solar

Types of Systems

 Grid Connected

 Grid-Connected with Battery Backup

 Off-grid or Stand Alone

Grid-Connected PV

System

When the grid goes down

so does your system!

Grid-tied with battery backup

Off-Grid or Stand Alone

Mounting options

Ground

Building—typically roof

Courtesy Rochester Solar Technologies

Orientation of Solar Modules

 For maximum output

 Solar modules should be perpendicular to the sun from sunrise to sunset

 This is possible with a tracker

 For fixed array, array should be pointed true south

 Not magnetic south

True south and magnetic south rarely coincide

Dedicated PV System for Aquaponics

PV Modules Charge Controller

Battery

Inverter

Air Pump Water Pump

Lights

45-watt system

Need to purchase 12-volt battery and 300-watt inverter

Will this work?

 Determine the size of the PV system

 Add up wattages of pumps

 Multiply each one by hours in use per day

 To determine watt-hours

 Convert to kWh per day

 Air pump -- 20 watts

 Water pump -- 40 watts

 Both run 24 hours per day

How to Size a System

 Total = 60 watts

 60 watts x 24 hours per day

 1,440 watt-hours per day

 1000 watt-hours = 1 kWh

 1.44 kWh per day

 Multiply by 365 for annual use

 1.44 x 365 = 526 kWh per year

How to Size a System

 1 kW system in Colorado

 5.7 peak sun hours per day

 X 365 days

 X 0.78 efficiency factor

 5.7 x 365 = 2080

 2080 x 0.78 = 1,622 kWh per year

 Unshaded array

 Orientation -- true south

How to Size a System

 526 divided by 1,622 = about a 0.32 kW system  A 320-watt system for air and water pumps  Most modules these days around 250 to 260

watts  So may need 2 modules  Cost about $1/watt or $250 each  Harbor freight 45-watt array is not going to

suffice  Then you need to size the battery to hold

electricity  Why?  Night time function  Power outages

How to Size a System

 Size battery bank for three days of battery-only operation

 60 watts x 24 hours = 1.44 kWh per day

 3 x 1.44 = 4.32 kWh

 Can’t discharge batteries more than 50%

 Need to double battery size

 Need 8.64 kWh of storage

 Four large solar batteries

 Cost of $400 each

How to Size a System

 Heating water can be a huge challenge  Resistive heaters consume lots of electricity  Water heater element – 4,500 watts to 5,500

watts  Run 4,500 watt heater  8 hours a day in cold weather  36 kWh per day – roughly $3.60 per day per

heating element  Won’t need that year round  But maybe for three to six months  Advice  Move South!

Heating Water in Aquaponics

 Smaller system

 Tank heater – 400 watts

 8 hours a day

 3.2 kWh per day per heater

 May not need that much electricity year round

 If you did, you’d need 1,168 kWh per year

 You’d require a 0.7 kW system

 Small solar system (approximately 1 kW) on your house would power your heater and your pumps

Heating Water in Aquaponics

 Suggestions

 For existing systems

 Improve efficiency – reduce the loss of heat from tanks and grow beds

 New systems – build them right!

 Insulate tanks and grow beds

 Insulate pipes, especially if they run through a concrete slab

 Starting new: Build a superefficient greenhouse that is thermally stable and hence provides most of the heat for the water!

 Provide heat via a solar hot water or solar thermal system

Heating Water in Aquaponics

 Two types of systems -- active and passive

 Components – solar collector and storage tank

 Often linked to conventional storage water heater or on-demand (tankless) water heater

Types of DSHW Systems

Solar Batch Water Heater

Integrated collector-storage

system

Passive system – no pumps, operates on line pressure

Open system

Progressive Tube Solar Water Heater

30, 40, and 60 gallon capacity

Progressive Tube Solar Water Heater

 Provide 100% of hot water on sunny days

 Preheat water on cloudy days

 Reduce fuel use and utility bill

 Fairly inexpensive

 Fairly easy to install

 No pumps

 No electricity

 No sensors or costly controls

 Little or no maintenance

 Heavy – be sure roof can support load

 Suitable for use in warm, sunny climates

 Not suitable for cold climates

 Can also use for domestic hot water

Progressive Tube Solar Water Heater

Active Systems -- Pump- Circulation systems

 Separate storage and collection

 Collector on the roof

 Storage tank located inside the house

 Advantage: reduces heat loss from storage tank at night

 Two common options

 drainback (water = heat exchange fluid)

 glycol (propylene glycol = heat exchange fluid)

Pump-Circulation systems

Solar Hot Water

 Drainback System  Active system --

pump driven  Heat exchange fluid

= water  Closed system  Designed for areas

where freezing occurs

Courtesy of Home Power Magazine

Solar Hot Water Design Ideas

Solar Collector Solar hot water

storage tank

Fish Tank

Controller

Temp. sensor

Pump

Heat Exchanger

Backup heating element

Solar Greenhouse

 Proper orientation and design of greenhouse

 Cooler in the summer

 Warmer in the winter Design all wrong

 Most greenhouses are spacious, uninsulated

 Too much volume

 No thermal mass

 Wide temperature swings year round

 Vent heat even in the winter

 Lots of energy to heat and cool them

Passive Solar Heating and Cooling

 We tend to use technology developed in Holland

 Large greenhouses

 Massive volume

 Single-pane glass

 Burn lots of wood, natural gas, coal, or oil to heat

 Then vent and cool in the summer

 Amount of fuel needed

 Exceeds amount needed to transport equivalent amount of produce from regions where it’s in season

Passive Solar Heating and Cooling

 Design to capture winter sun

 Plenty of sun in summer

 Orient greenhouse on an east-west axis

 No glass on north side

 Minimize or eliminate glazing on east and west sides

 Insulate north side

 Better yet, earth shelter and insulate on north side

 Provide thermal mass

 Double-pane glass or double plastic

Design Like a Solar Home

 In winter, store excess heat during day rather than vent

 Use stored heat at night in winter

 Produce heat

 Passively

 May also supplement with solar thermal system

 Store summer heat for use in winter

 Tricky but can be done

How do we solve these issues?

 Even larger challenge

 Store summer heat

 For use in winter

 Tricky but can be done

 Underground storage

 Sand beds

 Water storage tanks

 Ground beneath or around the greenhouse

 Draw that heat off during the winter

How do we solve these issues?

 Sound impossible?

 Consider the Chinese Greenhouse

 Passive solar greenhouses in China

 No supplemental lighting

 Little or no supplemental heating

 Produce vegetables through Fall, Winter, and Spring

How do we solve these issues?

 Chinese greenhouse

 Developed in mid-1980s

 Highly evolved technology

 In 2000, covered 650,000 acres

 No current estimate

 Virtually unknown in North America

How do we solve these issues?

 Long axis oriented East-West

 Not North-South

 Low-profile greenhouse

 Minimize surface area for winter heat loss

 30 to 46 feet wide

 Not all glass design

 Thick insulated back wall

 and partial roof

 Back wall contains thermal mass

Secrets of Success of Chinese Solar Greenhouses

 Large interior thermal mass

 Conventional greenhouse = soil, floors, and back walls

 In aquaponics systems – floors, back wall, and water

Secrets of Success

Solar Window

Design Features

 Arched struts (beams)

 Up to 12 meters (39.6 feet)

 Single layer of plastic

 Could be improved by applying a double layer

 Thermal blanket to insulate at night

Temperature Inside and Outside Chinese Greenhouse in Shenyang, China Temperatures were

10 to 15oC (18-27oF) warmer

Temperature inside and outside a Chinese Style Greenhouse in Manitoba, Canada Temperatures were 10 to

30oC (54oF) warmer

Design for heat retention

 You wouldn’t live in a greenhouse

 Because of wide temperature swings

 So how can our plants and fish?

 Redesign – Chinese Style

 Create heat storage for winter day-night cycling

 Underground heat storage for summer to winter heat storage

 Surplus summer heat pumped underground

 Released in winter

Design for heat retention

 Also earth shelter greenhouse

 Keep it cooler in the summer and

 Warmer in the winter

 Or consider

 Hoop houses over grow beds

 Underground heat storage

 Solar thermal heat storage

For Additional Information

For Additional Information

For Additional Information

 Dan Chiras, Ph.D.

 The Evergreen Institute

 www.evergreeninstitute.org

 [email protected]

 (720) 273-9556

Let the Sun Shine in!