Build a Simple Solar System to Power Your Survival Garden

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Noel Chase
5 years ago
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1 Build a Simple Solar System to Power Your Survival Garden

2 HYDROPONICS is a revolutionary way of growing food in the comfort of your own home. The appeal with hydroponics is essentially that you can control all of the conditions that would normally affect the plant outdoors, resulting in a higher yield, bigger fruits and vegetables, and faster grow times. There are two main things you can control with deep water hydroponics that you really can t in a conventional soil garden; 1) the nutrients the plant receives, and 2) the amount of light the plant gets. It s these two things that give hydroponics growers the edge over soil based systems. Many people today are considering hydroponics to be an alternate food source during a crisis situation, such as a natural disaster or civil unrest scenario. Certainly the ability to grow your own food at home while everyone else is starving is a major benefit if you know how. The intrepid hydroponics gardener might spot a problem with the idea of growing food hydroponically during such a scenario namely, where to get the power to run the grow lights. This is a valid concern; part of the appeal of hydroponics is the ability to grow the food indoors. Without grow lights, most hydroponic systems will simply fail most people do not possess the necessary amounts of natural light within their homes to grow anything, much less a bumper crop. So how do we get around this problem? Simple with solar power. SOLAR POWER THE ANSWER TO YOUR POWER NEEDS Solar panels are ubiquitous in our modern society, being used to power everything from dime store calculators to small cities, and just about everything in between. The technology of converting the sun s rays into energy isn t exactly new; French scientist Henri Becquerel discovered what is referred to as the photovoltaic effect in While solar panels as we know them today really came into use around 1950, they were far too expensive for the average person to use and were limited to industrial, scientific, and military uses. As the methods and materials used to make the panels became cheaper, they exploded into widespread use. While we all know what they look like - how do they work? The classic solar panel that everyone immediately recognizes is essentially a collection of pure silicon cells which harness the previously mentioned photovoltaic effect to produce energy. Photons of light strike the solar cell (made of silicon) and excite the electrons within that cell. Excitation

3 means nothing more than getting the electrons to move about quickly, and the motion of these electrons causes energy to be released in the form of electricity, which emerges from the panel in the form of DC (Direct Current) voltage. DC voltage is the same sort of voltage released from batteries, as opposed to AC voltage (wall plugs). The limiting factor in solar panel pricing was the ability to grow silicon crystals of a sufficient size so as to be powerful and cheap enough and that barrier has mostly been overcome. We ve seen solar panel prices drop remarkably within the last decade, as solar manufacturers move away from crystalline technology and towards thin film PV technology made from far cheaper elements. Solar panels are now light enough to be mounted just about anywhere, and powerful enough so as to not require football field sized panels. Modern solar panels are also far more efficient than older models, which needed direct sunlight to perform at their peak: the newest designs are readily adaptable to shade and oblique sun angles precisely the sorts of conditions you might see in a survival situation. TYPES OF SOLAR PANELS There are currently four main types of solar panels, which are also knows as photovoltaic or PV panels: Monocrystalline panels are the types of panels most people think of when they think of solar panels. As the name implies, each cell is composed of a single (i.e. mono) wafer of silicon, which gives them an extremely high efficiency rate but at the expense of cost; they are among the most expensive panels to make. Polycrystalline panels are a cost cutting design that decreases the cost by adding smaller and thus less expensive crystals in a conglomerate. Each cell is made up of several silicon crystals of smaller size combined to make one big cell. All this comes at the cost of reduced efficiency. String ribbon panels are a variation of the polycrystalline method of producing crystals and have the same efficiency rates as polycrystalline panels, all the while

4 reducing the cost of the panels since each cell is made up of thin ribbons of silicon. Amorphous silicon panels are the lowest electricity producing type of panel out there since they use a thin film of silicon applied over a layer of metal instead of using a true silicon crystal. When cost is a major factor, these are among the cheapest, but least efficient. WHAT ARE YOUR GOALS? You can easily power a good sized grow room with its associated lights by installing a roof full of solar panels no doubt about it. But your goal might be mobility in case of a survival situation, so you need to consider up front what your goals are. The biggest, most powerful commercial roof panels are upwards of 8 feet long and weight hundreds of pounds or more. Sure, they put out lots of power, but they aren t exactly going anywhere. So power requirements aside, consider your intended usage before you make a purchase. Additionally, solar panels are purchased by how much power they put out in watts. It s implicit in this statement that you need to calculate how much power your grow lights need, and how many of them you intend to use. Again, if you want to be mobile, you re going to have to comprise in the amount of grow lights you intend to use. Before you start calculating the size of panel you need for a given application, you need to look at the way a solar system actually powers something. If you thought you were going to hook your grow lights up directly to your solar panels, then you need to read this next section. PUTTING IT ALL TOGETHER

5 If you glance at the above schematic, you will see a solar panel system in its most basic form. There are several important points to be made with this system: In theory, your grow lights and pump are powered by the battery, not the solar panels! This is an important distinction. Why not just power the whole thing off the solar panels? Because the amount of light that hits the solar panels varies throughout the day, and thus varying degrees of voltage will be produced. Your grow lights and motors need a constant voltage to operate most efficiently. The primary purpose of the solar panels is to recharge the main battery rather than power anything directly. Switch # 1 s function is to disconnect the solar panels from the battery. In hot, sunny climates, you might conceivably overcharge the battery. You can eliminate this switch if you use a smart charge controller (discussed later) Switch #2 s function is to simply shut off the grow lights and pump motor whenever you need to. Another thing that is implicit in the above diagram is that the circuit, for the sake of simplicity, is kept in the direct current, or DC configuration. You may have heard of solar systems in which an inverter is connected to the system in order to produce AC power. An inverter is a device that converts DC power the type of power that solar panels produce into AC power, so that you can run plug-in style household appliances. For some installations, an inverter is essential, but it comes at a cost. Converting DC to

6 AC is simple, but involves some loss of power and efficiency. In the case of solar panels to power your grow lights, however, most if not all the components in the system will run off DC power! The benefit here is to keep the whole system as a native DC system. It will be simpler, more efficient, and have less power loss. Keep in mind that if you already have a grow light system, and you are confused by the fact that your current lights plug into the wall (therefore are AC), take a close look at the system. Do the grow lights have a black box in their power cable? Is the wall plug a power cube? If the answer is yes, to any of these, the lights are DC lights. The black box and the power cube are simply AC/DC converters which convert the power inline. All of these boxes are marked with two important pieces of information: 1) input voltage this will usually be 110V, which is an AC voltage (wall plug), and 2) output voltage this will almost always be 12 volts DC. Sometimes, it might be a little less (i.e. 8 volts, 5.2 volts, etc), but in any case will usually be 12 volts or less. Most devices that you think are AC devices, such as cell phone chargers, laptop power cords, etc, are really native DC devices. Even if your current setup has no inline converter or wall cube, it is still most likely a native DC system with the box mounted inside the light s enclosure. Check with your manufacturer for details. The pump for your hydroponics circulation is most likely a native DC devices as well. THE BATTERY YOUR MAIN POWER SOURCE As previously stated, it s the battery (or batteries) that actually will be powering your grow lights and water pumps, although the battery system will be recharged by the solar panels. A common mistake is skimping out on the batteries and getting big solar panels the net result is that you ll have far too much fluctuation in the system, and you ll sometimes see things like overly dim or overly bright grow lights, and fast and slow turning pumps simply because the voltage from the panels varies too much. You need a constant and reliable source of power for these items. Before you start sizing the battery for your needs, you need to select the right type of battery.

7 Irrespective of the size of the battery, what you really want is a deep cycle battery. A deep cycle battery is essentially a special purpose DC battery that outwardly looks like your typical car battery, except it is designed to discharge between 50-80% of its capacity and still recover. The makeup of the plates and paste material is very different from that of a car battery, which is designed to produces short, quick bursts of power to turn your engine. While you can run grow lights off a car battery, the battery you use won t last very long compared to a deep cycle battery. FIGURING IT ALL OUT In order to figure out a sample solar power and battery system, we need to know the size of the grow light system we re anticipating. For the purposes of our sample system, we ll assume the following: 3 15 watt LED grow light panels. A typical 15 watt panel is approximately 12 square and contains approximately 225 LED lights. Using three of these panels would provide sufficient area for a typical grow closet that would provide enough food crop to sustain a single person, once up and running. 1 hydroponics pump. A 12 volt unit that consumes about 2 amps of power and can transfer approximately 100 gallons per hour of volume. The system above is relatively rudimentary and small, but it provides a good combination of lighting power and mobility, which is important in a survival system. You ll note that there are three different measurements bandied about in the above paragraph; amps, volts, and watts. They are intimately related, but inherently different units of measure. Without getting too deep into the science of why these things are so, consider that: Watts = Volts X Amps First, let s calculate the total wattage of your system to keep everything in the same measurement; watts: Total System Wattage 3 grow panels, 15 watts each, = 45 watts 1 hydroponics pump 2 amps. Watts= volts x amps, so watts = 12x2 = 24 watts Total wattage: = 69 watts

8 While 69 watts might represent the actual number of watts being used by the system, it s always a good idea to put in a fudge factor because nothing is 100% efficient. In this case, a 20% reserve is not a bad idea. This gives us 83 watts. Great. 83 watts. But how long will those watts be running? What you need to do at this point is to calculate your watt hours, which is nothing more than the time you will be using the grow system. In this case, let s assume we will be running both our grow lights and pumping system for 14 hours per day. The calculation is therefore: 14 hours x 83 watts = 1162 watt hours All this means is that within 14 hours, you ll consume 1162 watts. This is an extremely important measurement because you will need a method of both storing those watts (batteries), and replenishing them (solar panels). SELECTING THE RIGHT BATTERY Okay, so you need a battery that can store 1162 watt hours. The problem here is that batteries are bought and sold in amp hours. No big deal, we just do a quick Watts = amps x volts calculation: 1162= amps x 12 Total = 97 amp hours Ok great, go buy a battery with a capacity of 100 amp hours and then call it a day! Wrong answer that would entail discharging the battery to zero percent! This rate of discharge would permanently kill the battery. You can t count on more than a 50% discharge if you want to get good life out of your batteries. Therefore, multiply by two, and round up. The battery you need, therefore, is a 200 amp hour, 12 volt, deep cycle battery. These are relatively inexpensive, costing about $100. SELECTING THE SOLAR PANEL

9 Now it gets a little tricky, because much of the solar panel s efficiency is going to be tied to how much sunlight your location gets. Different parts of the country get different amount of sunlight at different parts of the year you know this because you are a hydroponics gardener! First, you need to ask yourself how many direct sunlight hours your panel will get every day. For the purposes of our system, we ll say 5 hours. That will be relatively achievable for most places in the lower 48 United States. Even still, we assume what s called a worst weather multiplier, a factor of sunlight hours divided by 1.55 Worst case sunlight: 3.87 direct hours per day If you live somewhere sunny, feel free to bump up the amount of direct sunlight hours accordingly, but always factor in the worst weather multiplier. Next, you need to select your panel size. Solar panels usually come in increments of 100 watts, although many small ones are available. The crux here is essentially how much mobility you want, if any. Realize that you can get a 1000 watt panel, but it will be large and heavy. A 100 watt panel, for example, is approximately 48 x 21 x 1.5 in dimension and weighs 18 pounds. While bulky, it is certainly able to be transported easily and isn t too large. Assume for the next calculation, that we will be using 100 watt panels. Okay, so we re using 100 watt panels, and we estimate that they will be running 3.87 hours per day. So how much can one 100 watt panel put out during that time? Here is the calculation: 100 watt panel x 3.87 hours per day = 387 watt hours 387 x.85 = 329 watt hours

10 What s the.85 factor in there for? Simple nothing is 100% efficient. Okay, so we know that a single 100 watt panel can put out 329 watt hours. So how many panels will we need in total? 1162 watt hours divided by 329 watt hours = 3.5 panels Round up to 4 panels And there you have it. If you want to run the grow lights and the pump as specified for 14 hours per day, you will need one 200Ah battery and four 100 watt solar panels to do it. If you get more sunlight, you will require fewer panels. Also, you may not want to use 100 watt panels you may want to use a single 400 watt panel, and that would fulfill your needs perfectly. WHAT ELSE DO I NEED? Besides the battery and the panels, you will need a charge controller (shown on main schematic). Basically, what this device does is control the rate of power going to the batteries. When the sun is shining overhead, the panel puts out tons of power and this can cause the batteries to charge improperly. This controller basically protects your batteries and makes sure it gets the right charge. Hooking this system up is a breeze, but will depend primarily in what manner you want to accomplish this i.e. a permanent or temporary installation. If you wanted to be mobile, you d really need not much more than a spool of wire, the components as described herein, and an hour, which would be more than enough time to hook the whole system up. Positive wires go to positive terminals, according to the schematic there is really no wrong way to assemble this thing. Running your grow lights from solar panels is a remarkably easy endeavor, and would completely free you from the power grid, allowing you to grow all of your own food,

11 essentially for free. While the individual components require investment, they will rapidly pay for themselves after each subsequent harvest.

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