Simple solar power for outbuilding lights and pumping water

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In this post, we’ll show you the simple steps we took to setup our goat barn with solar-powered lighting and running water.

Note: Though titled as ‘simple’, some will no doubt find this complex. Understandable, however, nothing beyond grade-school math or a calculator is necessary for figuring this out. Take your time and try to understand it, ask questions in the comments if you don’t understand.

Our goal

Our goat barn is over 1000′ from our home, and the thought of running power to it gives us heartburn. Not only would that be tremendously labor-intensive, but also expensive and disruptive. We needed power to light the goat barn when we needed to be in there in the dark, and also to support having running water. We don’t spend more than one hour per day in the goat barn, so the true amount of time we would need to light it or run water was small.

Calculating the loads

To determine what we needed was fairly simple. First, we located the 12v LED lights we wished to use. We wanted something simple and common and found these on Amazon. They had good reviews and only consumed 7w while running. We knew we wanted to install four light fixtures but typically would only have two on most of the time the lights would be on. The maximum “load” of these bulbs (the watts times the hours to get Wh) would be about 28 Wh/day, or .028 kWh.

Next, we knew we needed to pump water from our rain tanks into the barn and out through a faucet and utility sink. This too was easily accomplished by using a 12v Shurflow RV water pump, also available on Amazon. This pump has an internal pressure switch which will turn the pump on when the pressure is low (ie, when a faucet is opened). However, we had an old pressure tank laying around and wanted to run the pump less often than every time we opened the faucet, so we hooked up the pump to fill the pressure tank. When the tank reaches pressure, it triggers the pump to turn off and also has plenty of pressure at the faucet. The maximum load of this pump we calculated at about an hour per day (which is very conservative since it runs more like 10 minutes a day). The amp draw is about 6 amps, so we calculated 12 Volts x 6 Amps = 72 Watts for one hour a day equals 72 Wh or .072 kWh.

So far, we need to support less about 1 kWh per day. No problem!

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Batteries

Now, we’d not typically recommend using deep cycle marine batteries for solar applications, because they’re really not designed for multiple cycles of deep discharging – something you regularly do with solar applications, but we had two on-hand, and let’s be reasonable – we needed to support some pretty small loads. So we wired these together in parallel, which keeps the voltage at 12 V but combines their amps. We did this to be sure that we’d never discharge the batteries below a very very small margin of their capacity, which helps them last a long time.

To help understand how this works, picture this… treat your batteries like a bank account. Treat your loads like withdrawals and your solar input like deposits. If you withdrawal more than you can put back in, you have a deficit (a dead battery). You need to size all your components so that the ratio of withdrawals and deposits keeps the battery happy.

Our system would take about 100 watts per day from the batteries. We need to put at least that much back in. Now.. to figure out what kind of solar panel to get, we needed to know about how many hours of sun we could expect on average. This is called “solar insolation”. There are many useful maps online that show what average hours are for any area. Ours is approximately 5.5 hours. This means that the average amount of usable sun hours per day, across all days of the year and average weather – would be 5.5.

Though we get 5.5 hours of sun a day on average, we can still go a week or so of no meaningful sun in our part of the world. We want to make sure our stuff works when this happens so we might need to support up to 5-7 day withdrawing  100 Watts of power, but with no deposits (no solar). These 5-6 days are called “Days of Autonomy” (DOA), or how many non-sun days we want to run without recharging.We also had to keep in mind that our batteries had to be adequately sized so that we could

We also had to keep in mind that our batteries had to be adequately sized so that we could withdraw 500-700 watts of power from the batteries without significantly discharging the batteries. This is why we used two because the amount taken out of each would be small. With something like a deep cycle battery, you shouldn’t really discharge them more than maybe 20% or you risk killing the batteries. Some solar batteries support much deeper discharges, but not these. The gist is that you need to make sure that after taking all you plan to take from your batteries, you still need to have the right amount of energy remaining. The percentage of how much of the battery energy you can safely take is called the “Depth of Discharge” or “DoD”. Our DoD would be 20%.

If we had been buying new batteries, we would have needed to buy batteries where 20% of their capacity was enough to supply 500-700 Watts. Solar batteries are measured by Amp hours. We have watts. How does that work? Well… take your watts, divide by the voltage of your system and you have the Amps.

100 W per day x 7 DOA = 700 W
700 W / 12 Volts = 58 Amps

Now multiply the Amps by the hours you need them. This is where it gets tricky because we don’t need our energy all at once. The most we will ever need at once is about8.33 Amps. How did I know that? Because, our total wattage, while everything is running is 72 Amps for the water pump plus 28 Watts for the bulbs or 100 watts total. Our system voltage is 12V (the voltage of the batteries, the soon to be solar panel, etc). 100 / 12 = 8.333.

If we ran all our loads for one hour, we would withdrawal the power at a rate of about 8.3 Amps per hour (8.3 AH). Assuming we need that for seven days, we’d need a battery that could support 8.3 AH for 7 days with a total of 58.1 AH.

Now… remember, we can only take 20% or so, so we actually need a battery that has a capacity 5x as much to get what we need out of 20%. 58.1 * 5 = 290.5 AH. Most solar batteries are measured in AH at 20 hours. Forget about what that means for now, but that is the number you want to compare when looking at your total AH needs vs the battery capacity. So, to summarize, to support 58.1 AH of need, we need a 290.5 AH battery. That gives us all the storage we will need to support 7 days of 1-hour per day usage and still not kill our battery.

Solar Panel

We needed a panel that provided as much resupply of watts to our depleted batteries as we’re taking out, plus a little room for margin. We were going to be taking out about 700/week, so we need to make sure we could at least put that much back in. So, we have 5.5h of sun per day on average, and 7 days to collect the sun during that week, that means we had about 38.5 sun hours per week to harvest about 700 W of power.  You shouldn’t just divide 100 w by 5.5 hours because there are a few more elements to consider. Namely, how many days we’d want to be able to run without any sun. We can get a week or so of no meaningful sun in our part of the world. We want to make sure our stuff works when this happens, so we might need to have 5-7 days of withdrawing 100 Watts of power, but with no deposits.

Since that represents best-case scenario and the weather and sun isn’t constant, we didn’t want to just divide 700 W by 38.5 sun hours and figure on an 18 W solar panel. It might work but would more often than not be insufficient. We decided on a 100 W solar panel from the great folks at Alt-E Store. They’re super-helpful, have a great YouTube channel, and are eager to help.

With a 100W panel operating at let’s say, 85% efficiency, we could potentially collect 3,272.5 Watts of power in seven days, or 467.50 Watts per day. Since we only should use 100 watts per day, this left us plenty of buffer and room to grow a little. We added this mount to a schedule 40 iron pipe placed 3′ into the ground and were ready to go.

Charge controller

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A charge controller is an important piece of the puzzle. Some try to be cheap and avoid them to their potential peril. A charge contoller manages the incoming solar power and charges the battery until the battery is “full”, at which time it prevents over-charging of the battery. They also often have a ‘blocking diode’ of sorts that prevents the energy in the battery from flowing into the solar panels when there is no sun (i.e. at night). We purchased this charge controller for that use. It is important to note that you need to have a charge controller that can support the charging amps you’ll be putting into it. Those charging Amps are a measure of the panel watts divided by the panel voltage (100 W / 12 V = 8.3 A). Your charge controller should be support slightly higher than your maximum charging Amps. Ours is 10.5 so we’re good.

Miscellaneous

To add some additional security and also to make things more organized, we purchased a marine battery terminal block on Amazon. We landed all our circuits positive wires to this block and all the negatives to the negative block it came with. This also gave us the ability to add fuse protection to all the circuits using auto fuses.

From there we simply wired everything together and turned it all on!

Using this for rainwater collection and pumping

We collect rainwater from our goat barn into IBC totes, some 3″ PVC pipe, a Rain Harvesting First Flush Downspout Water Diverter Kit, and a few misc pieces such as the Leaf Eater Advanced Rain Head and a stainless steel filter. We then use the RV (Shurflow) water pump mentioned above and pump the water through a standard household water filter and into a surplus pressure tank that we had on-hand. The pressure tank can be turned on/off with a valve

We then use the RV (Shurflow) water pump mentioned above and pump the water through a standard household water spin-down filter and a carbonb filter into a surplus pressure tank that we had on-hand. Oh… and we also have found that a 1/2″ PEX/SharkBite check valve is essential to make this work well – prevening the water from draining back into the tanks and keeping the pump primed.

The pressure tank can be turned on/off with a valve in-case we don’t want to bother with it. It can help the motor run less often by storing pressurized water. The pump has to run for longer periods of time, but less often. This can be handy for say… filling the pressure tank during peak sun hours then using the pressurized water during non/low sun hours.

Here are a few pictures:IMG_0238

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Homestead Tech: Drones

The multiple ways in which drones can be used for the small homestead.

We typically like to keep things pretty low-tech. We don’t have an aversion to technology, we just want to do things by means which are easily repeatable by anyone. Nevertheless, there are a few modern technologies that can be really helpful at times. Drones are a good example.

We have found the use of a drone to be time-saving or generally helpful in several ways.

Site Planning: Gardening

Planning gardens can be complex when trying to get an idea of the overall “fit” of the garden(s) into the surrounding landscape, even more so if those gardens are landscape-oriented. Aerial photos of the surroundings can serve as a nice backdrop for planning.

We send the drone up to take photos from different angles. We then import or paste those photos into a word processor (Pages for Mac in our case) and then adjust the opacity to about half. We then crop the photos, print them out and then use these to make sketches of our garden beds, landscaping, etc. Drones allow us to get photos from nearly any perspective which allows us to sketch out ideas from nearly any perspective.

Site Planning: Solar

Drones can also provide helpful aerial perspectives of shadows of the area under consideration. Simply launch the drone to the same altitude/location once per hour of the time you anticipate solar exposure. Do this for each season and you can get a rough idea of the shading of the area throughout the day and seasons. This can be helpful in determining solar panel placement.

Of course, an easier way to do this is with a Solar Pathfinder ( an excellent tool for homesteaders).

Inspecting…

There are numerous forms of inspections where we’ve found a drone to be a helpful addition.

One summer, while doing some light excavating, one of us had the unfortunate experience of scraping the lid off of a very large, underground Yellowjacket colony with our tractor. Fortunately, we were able to turn off the tractor and run away without getting stung. Those kinds of scenarios can be fatal you know!

A couple hours later, rather than risk walking into an angry swarm of homeless Yellowjackets, we were able to send the drone into the area and see where the actual nests were, determine the swarm activity and decide when it was safe to be in the area again. This also helped us determine where to make our “tactical” “surgical” strikes with Black Flag later on 🙂

Similarly, as beekeepers, there have been times where sending the drone over to the beehives has been more expedient for our needs than suiting up in bee suits, firing up the smoker, etc. Likewise, a drone can be used to get some perspectives on swarms or atypical behaviors. Note: We don’t like to annoy our bees (or any bees), and would advise keeping drone activity near a hive to a minimum.

… solar panels

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We have roof-mounted solar panels. We can’t see them from the ground due to the shallow pitch of the roof. A drone has come in handy numerous times to check the health and status of the solar panels. This is most helpful in the winter to check for snow and ice build up. After all, who wants to climb on a roof in snow and ice?!

… roof and gutters

A quick drone flight can spare us the need to get out a ladder and climb on a roof. The detail level of a drone cannot match a visual inspection, but it can determine if such attention is necessary. It’s much safer than climbing a ladder! It can also be helpful in determining if out-of-reach gutters need to be cleaned.

… fences

A drone isn’t going to be able to replace a human when checking fences but could help small landowners with quickly evaluating the condition of pastures and such. Walking is, of course, better, but not always practical within time constraints. A drone can be treated like a virtual teenager – sent out to do a job 🙂

… animals

Similar to fences, Wayward Bernese Mountain Dogmaking brief checks on small animal herds is also a helpful way to use drones. If you want to check on the location or general well-being of some animals, or perhaps help locate a stray animal, a drone can be a useful companion in such a task.

Oh… and drones are also useful for quick aerial scans for wayward Bernese Mountain Dogs :-/

 

Monitoring property boundaries

Trespassing is an unfortunate, but very possible and common issue for landowners. In our neck of the woods, this is often in the form of unauthorized hunting, and bored young people with nothing better to do than exploring and destroying other people’s (private) property. Rather than risk confrontation with persons of unknown character and intent, a drone can provide a means of monitoring and

Rather than risk confrontation with persons of unknown character and intent, a drone can provide a means of monitoring and recording of trespassers (in daylight at least) and provide photographic/video evidence if a legal need to do so becomes necessary.

Historical Records

It used to be that you had to pay companies to get aerial photos of the family home and farm. These days, you can buy a drone for a fraction of that cost. Furthermore, you can get aerial photos and videos of your property annually, serving as a nice record of the changes over time. These photos and videos will be important to the generations that come after you.

Real Estate

If the time comes to sell your homestead, aerial photos and videos of your homestead provide a unique perspective on your property to the prospective buyer.