Backyard Shrimping Equipment: Solar Power System*

* This document is a portion of the Backyard Shrimping Project. Click the "Home" button to review our effort.

The Process

Equipment and Tool List

Here is a list of the things you will need to construct your solar power system to power your pumps. We also have included recent costs and Amazon links to assist your ordering the part. Click on the image to see the specifications or to order from Amazon as it will help fund our efforts to provide sustainable urban shrimp farming in your backyard.

Calculating the power needs

We need to determine just how much power we will be using with the air and water pumps. To do this, we need to look at each of the pumps to see how many Watts each will use. We have one 30 watt air pump and one 0.2 amp water pump. To convert amps to watts, we take the amp rating and multiply it by the voltage to get the watts:

So, the watts our water pump will draw is

The water pump pumps water into the biofilter and needs to run at least 5 hours per cycle to keep the bacteria in the biofilter alive. The air pump can be run on 6 hour cycles. But to allow us some safety in case of poor solar panel output due to cool temperatures and cloudy days, we will calculate our power needs assuming that both the air and water pumps will run 24 hours each day.

So our total maximum Wh is 778 Watt-hours. Most power systems have a 30% loss, so

Selecting the Solar Panels

We know that we will need a total of 1011 Wh generated to power our pumps 24 hours each day. Solar panels are rated by watt output at maximum illumination, and during our growing season operate at about 72% efficiency. Solar panels receive an average of 4 hours with maximum illumination. We need to be generating at least 325 Watts each hour.

Constructing Solar Panel Bank and Charge Controller

We purchased one 200 watt and one 150 watt panel. These panels provide a 12 volt output to charge our 12 v storage battery. The actual out put for each panel may be greater than 12 volts (mine run at 17 and 18 volts), but the charge controller prevents damage to the storage battery bank. These need to be connected in a parallel circuit so that the wattage is increased and not the voltage. Once the panels are wired in a parallel circuit, the solar bank is connected to a 40A charge controller (350W /12V = 29, so we are using a 40A controller to allow some room for variation). The charge controller prevents back surges to the panels and overcharging of the battery. When connecting the controller, connect it to the battery first, then to the output from the panels that have been covered to prevent a electrical spike in the controller).

solar Wiring

Constructing the Power Storage Bank

We need to insure that there is a constant power stream independent of the time of day. To do this, we use deep cycle storage batteries. Deep cycle batteries are designed to avoid "charge memory". Most common 12 volt automotive batteries are damaged when they are frequently discharged to near "exhaustion'. Deep cycle batteries are used in industrial, RV, and marine applications as these require the battery to be almost or completely discharged and retain the ability to research the full charge. The most commonly and least expensive deep cycle batteries are called "flooded acid lead" batteries. These generally do not need acid level checks as in the case of the normal lead acid automotive battery and are sealed. The storage capacity of a battery is rated in Amp-hours 9Ah). To determine how Ah we need for our solar power system, we need to do some calculations so that we purchase enough batteries for our power storage bank.

Power Bank Calculations

We need to provide 1011 Wh of power at 12 volts. The required storage capacity is

We selected a Duracell Deep Cycle Marine battery (class 27M, 90Ah) from Batteries Plus. The retail cost was about $130 but we were able to order and pay online with local store pickup for $90 with a 10% discount. So check online first, you'll save enough to pay for the materials for the substrates. vantof this style of battery is that is has two positive and two negative terminals (a "screw" style and a "stud" style). The extra connections allow one set to be used to send power to the invertor (I used the "stud"/traditional terminals for outgoing power) and the other set ("screw" terminals with associated nuts) to connect both the incoming solar power and the float charge). Connect the float charger to the screw terminals on the battery, and the solar controller output to the adapted post terminals. The power invertor is also connected to the adapted post terminals.

Because we want to have a backup in case we have extended times without solar power generation, we use a 110v "float" battery charger. A "float" charger is different than a common "trickle" charger because it monitors the discharge state of the battery and can change the charging rate from a low to a high rate as needed. This is similar to the abilities of the charge controller that is between the power bank and the solar panels.

The last component in our solar power system is the power invertor. This lets us provide power to the air and water pumps that are 110 volt devices. Our pumps draw a relatively small current and we are using a 200 watt 12v DC to 110v AC unit.

Installing the Solar Power System

As mentioned above,The solar panels are wired in a parallel circuit, using a MC4 parallel connector. Use a UF 8/2 cable with MC4 connectors to connect the COVERED solar panels to the 40A charge controller. This cable has MC4 connecters on one end and stripped bare wire on the other end. The bare end will be connected to the charge controller. Use one of the controller USB power outputs to power a small fan to cool the controller. We used two large screen TV wall mounts to mount the panels to a 4' x 4' wooden "skid". At our lattitude, the panels need to be at a 12° to 13° angle, which covers the maximum tilt for the TV mounts (see Optimum Tilt for Solar Panels for the calculations). If you need more or less tilt, use wooden blocks to change the angle. Determine true south (Finding True South the Easy Way), then face the solar panel skid to true south.

Use ring battery cables to connect the battery to the controller. You will need to remove the ring connectors from one end of the cable so that the cable ends can be inserted into the controller battery connections. Attached the rings to the adapted post terminals on the battery. Use battery ring cables to connect the adapted battery post terminals to the power invertor. Attach the float charger to the screw terminals on the battery.

At this point, the air and water pumps can be connected to the power invertor, and the float charger connected to an external 110V supply. When the battery has been connected to the controller, the controller display should power on and you will be able to check the battery charge. Uncover the solar panels to begin power generation, and you will be able to check the solar panel output. Your solar power system is functional at this point.