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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A reasonable plan toward residential solar or other renewable energy

Solar Installed

Solar energy is expensive. It currently costs more than grid energy, leaving many people to conclude it isn’t worth it. If your motivation to choose alternative energy is mostly to save money – you won’t get that outcome with this information.

At present – establishing alternate energy at home has not yet reached financial parity with grid power. For most of the general public, an investment in your own private renewable energy infrastructure is going to be more expensive, or at best break even. There are exceptions – like those with exceptional wind or hydro capacity on their property, however, most people won’t be the exception.

So…. is saving money the only reason to pursue renewable energy? No! Here are some other solid reasons for doing so:

  • More energy independence
  • Emergency power
  • Energy reliability or performance
  • Earth stewardship (* this is a nuanced idea)

In our case, we work from home – one of us as a web technology consultant. Lost power = lost work = lost income. Rather than have to pack up and go to town every time the power goes out (which is often not possible due to weather), it made good sense to install solar for backing up the business.

For those just interested in living on the cheap – stop reading this now. Other than some tips that might help you save 10-15% on your current energy bill, you’re not going to find much else below.

Below is a plan for “baby steps” one can take toward obtaining and using renewable energy. This is a plan that requires on-going, incremental changes and investments rather than a large, all-up-front expenditure. This approach delays the more significant costs until they are the only remaining ‘next step’. Doing so helps avoid financing these steps and also allows one to learn along the way and revise the plan as necessary. This should ultimately make renewable energy less expensive to implement in the long run but still allows a family to benefit along the way.

The following steps will allow your household to accomplish energy reliability, security, and sustainability in increasing measures over a period of time. You could compress these steps into months, or stretch them out over years of decades. Anyone can follow this approach in a time-frame that meets their budget.

Step 1: Measure and Monitor Usage ($)

If you don’t know how much energy you consume, you cannot adequately determine what you will need from a renewable energy system.  Likewise, if you cannot adequately size an emergency backup generator system without knowing what you need. You could easily spend an unnecessary $1-2k on too large of a generator sheerly for not knowing the loads you will need to support.

Measuring consumption is uber important! Our first step doing so was to purchase a Kill-a-watt (~$40). This allowed us to see what individual appliances were consuming, find and remove “ghost loads” (things that consume power when not “on” or “in use”) and gain insights into our usage.

Next, we invested in a system called The Energy Detective (TED). TED allows us to measure all our energy use for the entire household, down to the second. We have a large and complex household electrical system, so we got the TED version that monitors up to 4 panels. Our cost was around~$500, but a typical cost would be between $150-$299. Though we’ve not tried it, Neurio, another home energy monitor looks promising.

Some may already be balking at such expenses. Let me encourage you with this: It is typical that when a household starts to monitor usage to see a resulting decrease in use of around 10%.  Awareness of use causes changes to behaviors and patterns. What is 10% of your electric bill and at what point is a $200-299 investment worthwhile to make such an investment?

Step 2: Reduce consumption (FREE to $)

With an awareness of how you are using energy comes an almost-automatic reduction in usage. When you begin to associate dollars and cents with things being on/off, you start to change your behavior. You also start to consider what can be done to reduce your usage.

Get this idea in your mind now… By reducing your consumption immediately, you are ultimately reducing the size (and therefore cost) of a renewable energy system. Make sense?

There are three main ways once reduces consumption:

  1. Changing behavior
  2. Managing use
  3. Replacing offenders

Changing behavior – These are mostly simple changes – like choosing to run your dryer less or at times that are less expensive. Or, even better, get a clothesline – one of the best and cheapest solar appliances ever invented! Changing behavior might also entail turning lights off when you leave a room, turning your computer off when you’re not using it. That sort of stuff. These changes are usually zero cost.

One idea we really like is taking one day a week to have an ‘energy sabbath’ of sorts. Turn off / unplug everything non-critical and focus on togetherness. You could stand to save 15% of your power bill, reduce pollution, and be better off for the time spent together.

Managing use – Similar to changing behavior, managing use includes establishing minimal devices that manage how and when power is consumed. An example might be power strips that turn off peripheral devices  (printer, DVD player, XBOX) when a related main device such as a tv or computer is turned off. These require minimal investment but reduce consumption.  Another great example is the addition of low-cost means of reducing electric energy consumption. This might entail installing (and using!) a clothesline (can you tell we’re fans of clotheslines?) or installing a wood stove to rely less on electric heat.

Replacing Offenders – Though not always necessary, sometimes the best investments one can make in their energy consumption can entail replacing appliances or devices that inefficiently use energy. Still using a fridge or freezer from twenty years ago? Upgrading those appliances to Energy Star, or otherwise, more efficient versions will offer your more payback in the long run than keeping them. The same can be true of water heaters, furnaces, etc. Again… remember that the lower your energy consumption now, the smaller the renewable energy system you will need, and you may potentially have more funds to dedicate to such from paying less for electricity.

Step 3: Isolate critical loads ($$)

You are going to quickly discourage yourself away from backup or renewable energy if you try to size either system based on your total electricity use. Forgeddaboudit! Instead, determine what are your “critical loads” and seek to first back them up (ie. with a generator) and secondly, later on, to run them from renewable energy. You’ll thank us that you took this approach if you do since you’ll have much better understanding of how things work.

This step involves auditing all your electrical circuits to determine which ones are critical or essential. For example, if you live in the country, this might include your well pump, septic pumps, etc. For most people, it will include a refrigerator and/or freezer. It should include some lights. Here’s a great way to determine this… Carefully consider what your “must haves” are in the event of a power outage of seven days and place every circuit in one of three columns: “Don’t need”, “Nice to have”, “Must have”. If you take our “energy sabbath” idea to heart and try this throughout the year, you should already have an idea what things you must have operational.

Once you’ve done this, you should begin to physically isolate those critical loads. This is often done in either a generator panel or a sub-panel that is wired into/alongside your main electric panel. The goal here is two-fold. 1) Separate the circuits and 2) provide switchable backup power to these circuits. This is work best done by professionals or very capable DIYers.

Our critical loads, isolated in their own sub-panel(s)

Our critical loads, isolated in their own sub-panel(s)

In the future, if/when you get to renewable energy, it will be far easier to do when your physical infrastructure has organized these critical loads into one place.

Furthermore, measuring your critical loads (ie. with a TED or other energy monitor) is also easier at this point. This point is worth emphasizing. When your loads are isolated – even if not yet backed-up, you can now measure them independently and begin to do so right away. Measure them for a few months, or a year or even better a full year. You will gain valuable information needed to accurately size a backup power solution and/or an alternative energy solution.

Why? Because you will gain information such as your persistent, average, and peak electrical loads on your critical circuits. With this information in hand, you can determine the exact size of a backup generator, solar panels, wind turbine, batteries, etc. You will also be able to determine what items from your “Nice to haves” might be able to be moved to your “critical loads”.

Take it to the next level: Energy consumption is meausured  (in North America) in kWh (killowatt hours). That is a measurement of “watts hours” (Wh) divided by 1000. A Watt Hour (Wh) is the measurement of watts consumed x the hours used. If you had a 100 w bulb on for 24 hours a day (100 W x 24h = 2400 Wh). To get the kWh, divide this by 1000 (2400 Wh / 1000 = 2.4 kWh). Add up the watt hours of all the appliances you want to support with solar, and you’ll get your total Watt Hours. Just don’t overlook that not all appliances run constantly, but at intervals throughout the day. A simple enery monitor such as a Kill-a-watt does all this work for you.

Watts is a measurement of  Amps x Volts. So if you have an appliance that uses 15 Amps and a voltage of 12oV it will use 1800 Watts. Now… if you then run thata 3 hours a day, what do you suppose the Wh might be? If you guessed 5400, you’re correct. And in kWh? Yes, 5.4 kWh!

These numbers are important for all conversations pertaining to sizing backup or renewable energy.

These steps require the help of a qualified professional and WILL cost money – perhaps several thousand dollars. However, they are a worthwhile investment into your future and will save you potentially thousands of dollars wasted on over-sized solutions later on.

Step 4: Backup Essentials ($$)

When you isolate your critical loads, it is now far easier to back them up. Usually, this is done with a generator, some sort of physical transfer switch, and a generator input receptacle. If you’ve done the steps above, especially monitoring, you will know what your critical/essential loads require and what size generator is necessary to meet those requirements.

Once again (unless combined with the previous step), the services of a qualified professional electrician are required here. The cost is not trivial, but not unbearable either. You will need to purchase a generator, transfer switch, and a means of connecting the generator to the transfer switch. Additionally, you will need to secure the services for connecting all these things together.

When you are done, you will have the means to run your critical electrical circuits on backup/emergency generator. You will also then have much of the infrastructure in place for eventually powering these same loads with renewable energy.

How we did it: When we were at such a phase, we used a simple double pole, double throw (DPDT) switch that had two inputs – one from our main service panel, the other from a generator outlet. When we needed to run the generator, we’d move the switch into the “generator” position, start the generator, and be on our way. When we were finished with the need, we’d shut down the generator, return the switch to the “Utility” power position, and resume normal life. This is not automatic but is also very affordable.

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Portable Generator outlet - just plug in the generator and flip the switch when needed.

Portable Generator outlet – just plug in the generator and flip the switch when needed.

Step 5: Add Batteries, Inverter, Charge Controller ($$$)

Now it’s time to determine how much energy you want to store. This is done by multiplying your critical loads by the number of hours you want to operate them by batteries, factoring in the percentage of the battery that can be used without reducing their longevity. For example, if your critical loads required 10 kWh/day, and you wanted two days, and you wanted to never draw down more than 20% of your batteries, you would need to have enough batteries so that 20% of their combined stored energy amounted to 10kWh per day for two days (or 20kWh).

In industry terms, the number of days you wish to be able to run without recharging your batteries is referred to as “Days of Autonomy” or “DOA”.

Here again, knowing your real needs/usage (through monitoring) is critically important. Otherwise, the best you can do is guess and your guess is likely to be way too large (expensive) or way too small (inadequate).

This may seem an odd step to some. Why install batteries before any sources are producing power?

Here are some reasons for doing so:

  1. They are the infrastructure for off-grid or grid-interactive solar or wind applications. If you never want to be able to use your renewable energy when the utility power is unavailable, you don’t need this step. However, what sense does it make to have potentially tens of thousands of dollars in renewable energy and not be able to use it when you need it most – in a utility outage? Believe it or not, most home solar installations in our country are what are called “grid-tie” systems and cannot operate, or operate at a greatly reduced capacity during a utility failure.
  2. With batteries and a generator in place, you can operate a generator only long enough to re-charge your batteries during an outage. For example, if it took two hours to charge your batteries but they could support your critical loads for 24 hours, you’d only need to run the generator for two hours every day vs the entire length of an outage. In short, batteries extend generator fuel.
  3. Optionally, using the right equipment, you can program your system to use grid power or battery power based on peaks and lows of cost. This can be done by re-charging batteries using grid power when rates are low and using generator power (in the case of automatic backup generators) when grid power is at peak rates.
Solar batteries can be heavy - this one is 2200lbs

Solar batteries can be heavy – this one is 2200lbs!

Step 6: Add Renewable Collectors ($$-$$$)

With all the above done and with the proper equipment, you can add in renewable energy products such as solar panels, wind turbines, or micro-hydro. It’s important to know how/what you intend to do at this step before purchasing the equipment from Step 5 because you need to ensure everything plays nicely together.

With renewable energy sources, you are probably not going to save a lot of money. In our case, we probably save $15-$20/month. That’s nice and all, but not even close to worth the investment if it were for financial gain. What you will gain is “fuel extension” and additional (redundant) source of energy.

Step 7: Learn, learn, learn

Owning and maintaining equipment such as above is NOT simple, hence one of the reasons we’ve avoided blogging about it 🙂 Nevertheless, it is doable! To get the most out of the experience, invest time into learning everything you can about these subjects.