Off Grid: How to do solar/wind

How to do solar/wind

I've always looked at ways to reduce our cargo when going out to the land.  A big issue is needing a generator with enough fuel.    The noise is also a problem during hunting seasons.  For that reason, I learned about solar and wind.  I will explain the concept of building a system to give you an idea of what's involved and cost.  You should consult with a professional about installing a solar/wind system.

Solar?  Wind?  Battery?  How much power do we need?   This requires some knowledge of electricity and basic math.  I would need to power the RV that is on our hunting land.  My average usage is about 2A (amp) with spikes up to 5A while running the air conditioner.   

It's best to know your actual power needs which can be measured in many ways.  My generator displays the usage but it could also be done with hand held meters.  You can also look at the specifications on the appliances you need to run.   Everything lists the power requirements from the manufacturer.  Your power consumption is the single most important information you need when designing a system.   If you are not familiar with electricity then you should consult with a professional.

To make the calculations we have to put everything in the same terms.  It is best to use watts as the common term.    Watts (w) can be calculated by multiplying the volts (v) with the amps (a).  When the RV is connected to a generator or utility it uses 120V AC with a max of 30A.  For this example, I will use the numbers for the max of the RV which is 30A.

The RV has a maximum of 3,600w. (120 x 30)   Kilo-watt hours (kwh) is just the amount of power used over time.  If I used 3,600w every hour then my consumption would be 3.6 kwh.   This is probably more what you use in your home.

Solar/wind come in many voltage configurations 12v, 24v, and 48v.  (There could be others but there aren't common and I haven't see such kits available.)   How do you know which you should use?     It's mainly a question of the size of wire you use.    Wire must be of a certain size to handle the amps.   Electricity traveling through a wire generates heat.  An undersized wire will melt or catch fire if the rating is exceeded.  The reason why fuses and breakers are used in circuits is to prevent wires from exceeding their limits.

A 12V system would have 300A.     This is calculated by the Watts divided by the volts.   (3600 / 12 = 300)    In addition to wire size, your batteries and charge controller must be rated for the amps.   300 is too big.   Increasing the volts will reduce the amps.   In this case, I would select a 48V system.   (3600w / 48v = 75a).      

At 75a, I will need 3 gauge wire to connect the system.   Check the specifications on batteries and controller for their max.   We can also put in fuses/circuit breakers for 75A.    The higher voltage systems are usually more expensive.

Batteries

The sun doesn't always shine nor does the wind always blow.    We need batteries to keep the lights on during times when power can't be generated.    First, we must decide how capacity we need.     Batteries are rated by voltage and amp hours (ah).   If you had a single 100ah 48V battery then you have 4,800W (100 * 48)    This means that one battery would discharge in l hour 20 minutes from the 3600w consumption.     

Keep in mind, that I'm describing the capacity and not a real world application.     First, the battery would need to be able to handle a constant 75a draw and batteries can't be drained completely.    For example, some lithium batteries can only use 50% of their capacity.    It depends on the type of battery you're using.   You must pay close attention to the specifications of the batteries.   The best type of battery is beyond the scope of what I want to cover here.

If you had 10 batteries (48v 100ah) then they will provide about 13 hours running capacity.

48 x 100 = 48,000

48,000 / 3,600 = 13.33

If your batteries can be drained by 50% then your usable capacity is 24,000w or 6.67 hours at maximum load.    If you can't find batteries that can handle a 50% drain then you will adjust the number of batteries to compensate.

If you can't find a 48v battery then you can buy two 24v batteries and wire in series.   This means the negative post of one battery is connected to the positive of the next battery (then connected to the controller).    This increases the voltage of the battery but keeps the capacity the same.  Two 24v 100ah batteries wired in series will produce 48v at 100ah.

You can increase the capacity by wiring batteries in parallel.   This means the positive post is wired to the positive of the next battery.     Two 48v 100ah batteries wired in parallel will produce 48v at 200ah.

A more detailed explanation can be found here.  Series Vs Parallel https://lithiumhub.com/series-vs-parallel/

Other Considerations

Everything connected to your circuit will consume power.    All wires have power loss due to resistance (resulting in heat).   All inverters, transformers, and controllers will consume power.  All the usage should be considered in your calculations.  There are no freebies.

Recharge

We must recharge once the batteries are drained.    If we have a total capacity of 24,000 watts then the watts of the power source will determine how long it takes to recharge the battery bank.    The voltage should match your system.  We would need a source that outputs 48v.    

The charging is handled by a controller.    The controller must match your voltage and amps.   This is usually expressed as watts with ranges for the volts and amps.   The controller also must be compatible with the type of batteries you are using.    The type of output is also important.   I need 120v to power my RV.   However, if I want to provide power to the water well then I need two phase 240v.

Wind

Wind power is probably the most expensive and least reliable.   It requires a turbine and compatible controller. They will be rated in volts and watts.   An 800W 48v turbine will take 30 hours to completely recharge your battery bank.  (24000 / 800 = 30)  Wind speeds vary based on altitude with the slower speeds being at the surface.   

Turbines have wind speed operating ranges.   There's a minimum, max generation, and safe operating speeds. The 800w unit needs 6mph to generate some power but 9mph to make the full 800w.  High wind could damage the turbine above 12mph.  Most turbines have an automatic shutdown when the wind is not with an acceptable range.  Your local conditions must be taken into account.  A turbine will be useless if you average is 3 mph.

The minimum height needed is at least above any trees.   At my location, the minimum is 30 feet tall above the tree canopy. You can find the average wind in your area on weather maps (eg: https://www.ncei.noaa.gov) or hand held measuring devices.   I would need the turbine to be at least 50 ft above the ground get the minimum (6 mph) in my area.   I would need to go a high as 100ft to regularly get the full 9 mph needed.    If you live in a high altitude then you may need to go higher for faster wind because air density is a factor.

The higher the tower is, the harder it will be to perform regular maintenance like greasing and replacing worn parts.  A cheap turbine may require more maintenance and may not produce enough power for your needs.  If freezing rain is an issue in your area the a turbine maybe unusable for days until it thaws.

The wind will not be constant even at the optimal height for a location.    You may only get 2 hours a day of usable wind.  For most people, wind power impractical.

Solar

Solar panels are cheaper and easier to maintain when compared to wind.   The only requirement is a clear sky view.  The amount of power they generate is dependent on the angle to the sun which first means pointing in the direction of the equator.   (northern hemisphere would point south)

The panels should be at the optimum angle to the horizon.   Sites like https://footprinthero.com/solar-panel-tilt-angle-calculator provide a calculator based on your location.  The angle changes with the season but you can set your panels at a median.   Mounts that automatically adjust the angel are available.   They follow the sun to maintain the best angel. They are expensive and consume power.   In my opinion, they aren't worth any extra power you might get.

Panels don't generate every minute the sun is out.  Cloud cover, sun setting, and sun rising will change the power generation.  The usable hours are easy to determine. There are many websites that will show the peak sun hours.   The amount of hours will be lower the farther away from the equator you are.  This represents the average amount of usable sun per day. This is just a guide.  Lets assume that it's 5 for the example.

This means a 200w panel (48v) will generate a maximum of 1000w per day.  (200 * 5 = 1000)    It would take 24 days to charge your batteries with one panel.    24000 / 1000 = 24       1,000 is the total watts generated per panel per day.    If you wanted to recharge the battery bank in a single day then you would need 24 panels.   This doesn't include any power consumption while your batteries are charging.    

The watts vary by panel.  Panels are no different than batteries and can be wired in series or parallel to achieve the voltage of your system.  The point to remember is that if you wire in series to increase the voltage then you need more panels for amps. It's possible to buy panels with the correct voltage.   They achieve it my internal wiring.

Panels need to be regularly cleaned. Dirt or leaves will reduce the efficiency.  Panels are limited to how much sun they can convert to electricity.  This is due to the materials use described by the Shockley–Queisser limit.   The efficiency limit is about 33.7% for most panels currently available.  This means only 33% of the sun's energy is converted to electricity.   The best panels (and most expensive) available are about 21% efficient. There are some panels available that claim higher levels.   They achieve this by multiple layers not improvements on the cell. 

Panel will lose efficiency each year (about .5%) which quickly adds up since the efficiency is low to start with.  You can expect the panels to last at least 15 years before needing to be replaced.   This will vary depending on the quality of the panels.

In the real world

In the example, I used the max 3,600w for the calculations.   This might be typical usage for a house connected to the utility grid. I expect the usage to be less in an off gird application.  The RV can use propane for most of the appliances and can operate on 12v.  120v would be nice to charge the phone or satellite. 

In the beginning, I measured my average need as 2a.  I would need 240w per hour which means the battery bank in the example will last a little over 4 days. 8 panels could charge the battery bank in about 5 days while still using 240w during 12 hours in day.

The good news is that at 240w system has a max of 20a at 12v which means you could use a 12v system and save money.

Land: Clearing things up

We went back to the land at the beginning of June.  I rented a CAT D5 and 299 Skid Steer with a mulcher.  We arrived just before noon on Saturday. It was good to see the RV was still there in good shape.  The biggest issue was the water pump was singing it's death knell and a small bird had created a nest on top of the propane tank. I don't know what kind of bird it was.   They were small mostly brown in color.   I counted at least 3 nestlings.

 

The plan was to expand the RV area and food plot.  I also wanted to create a couple ponds and a new food plot on the west side.    We arrived just in time to meet the equipment delivery driver to lead him in.    There was a new locked gate just off the county road.  No one had cell service and turning around would be nearly impossible. Thankfully, the delivery guy was able to radio his boss and get the combination from the phone number written on the gate.

The number was for the operations manager of the gas company running the wells in the area.   He said the land owners on the north end of the road suffered large losses from thieves recently.   The gate was built to discourage random people from entering.   This is the first time we've heard of wide spread thefts. He said the oil company regularly has parts missing.   They run their equipment on solar panels because there's no electricity.   He said they tried to make the batteries and panels harder to steal but the thieves would just tear up more to get what they wanted.    They usually just accepted the occasional loss.    He said the road is technically owned by the oil company and if I catch someone trespassing to let him know and the oil company would file charges as well.   

He also said that a quarry company owns the land to our south and might provide access to the main highway.  I couldn't find a company that owned any land to the south.  The only one I know of is a Mike who owns the land to the north.  I've already talked to him and he doesn't know of any alternative routes.

I also discovered the Texans who bought a plot of land last year is an elderly gentleman named Chuck.    He was also using a lock on the gate.   I had a great conversation with Chuck. He said he has been staying the winter months there September till February.  He keeps an eye on things while he is there thus earned the nickname "sheriff".

The water was below the bridge which indicates it had not rained for several weeks although the roads showed there was a lot of rain since November.  The erosion channels were deeper and many new deep pot holes.

Some of the pot holes were very deep and I scraped the ground with the trailer jack.  The jack doesn't work anymore and will have to be replaced.   I think the biggest factor was there was 200 gallons of water in the back which caused the truck to ride low.  I hope the new gate will keep the four-wheelers out too.    They like to joy ride through the area ripping up the roads and drinking beer.    One of the worse spots on the road near a cattle guard was created this way.    A year ago we noticed new tracks where someone left deep ruts which the water now uses as a path eroding it deeper.  I doubt they got stuck there and the tracks were too narrow to be a truck.

We got to the well pad and unloaded the tractor.    We started moving equipment down to the RV when we encountered a deep erosion channel on our road.    It's the same spot that was there last year.  There are two major spots in the road we've had problems with.    One at the top of the road eroded a foot deep and wide.    It was bad enough I couldn't get the tractor over it let alone a truck and trailer.    We had to turn around and bring the dozer to correct the road again.     

The trouble spots were fixed last year when we rented the dozer, but it's not a simple case of the correcting the slope.     I believe when it rains hard enough to raise the water table there are two locations on the road that drain.    We have located several places all over the property located mostly in creeks where water seemingly comes out of rocks.   They run for weeks after a heavy rain and in the road it slowly erodes exposing the bed rock.

The first spot is just north of our property half way down a steep slope which drops elevation 20 FT through a couple benches.  The second is past the RV on a steep slope where the elevation drops over a hundred feet in a short distance.  

We have a few options which is to locate a new path further to the west or fill these spots with gravel.  The second erosion area can be avoided if we fix the alternate path created by the previous owner.    It turns before the trouble spot crossing a wet weather creek.    This area is mostly stone so it doesn't erode.    The problem is the creek bed is full of pits and sharp rocks.   This where we lost a tire the first trip as owners.  We tried to fill the holes with rocks from the area but a heavy rain had washed them away.  We need to fill the deep spots with concrete to make it easier on the tires.   We don't plan to bring the truck over this often, but we need at least one trip to remove the old camper and trash.

By the end of the first day, I fixed and widened the road.   It's now about 10 feet wide.   The gyroscope of the dozer was broken so I had to level everything manually.  This was a challenge since it's only the second time I've driven a dozer.  By the end of the night my son put rocks in a 5 feet circle and we settled in to enjoyed the night with beer and BBQ.

We were awaken by thunderstorms early in the morning.   It rained until after noon dumping a total of 2.5 inches.  The sky was clear the rest of the day which made the heat and humidity almost unbearable.  The ground is mostly clay and became a soup.  Thankfully, the road didn't wash out but there was a spot where run off was starting to erode again.  We waited until the afternoon to start work.    I was able to fix the run off area by putting a slope in the road.  It was difficult due to the slimy mud.    The biggest problem while it was wet is the ground cuts off like a slab of cold butter.    This made it impossible to level out the land with the dozer.  

We cleared some of the trees around the RV.   I pushed the trees over with the dozer then tried to fill the holes which didn't compact.  We had to get the chainsaw to cut up the down trees often then move the logs and brush to piles.   It was interesting the trees seem to collect rocks out of the soil and pull them close to the trunk.    Many of the trees had a large collection of stones of all sizes in their roots.

The hope was we would have enough sky to get a cell phone signal if we could clear a path from the RV to where the elevation begins to drop.   I was hopeful because my son was starting to get notifications around the RV.

At then end of the day we moved the trucks up to the well pad.  The forecast indicated rain the next day.   The amount of rain is always an uncertainty.   A forecast of "scattered light showers" could mean trace to heavy down pours.  The road looked solid after drying all day but the fresh soil had become like peanut butter.   There was a lot of slippage making four inch ruts but we managed to get to the top.

We didn't get much done due to a late start.   It was so wet that we couldn't even get a fire going.  Every stick of wood was soaked.  We went inside the RV and just watched a movie until bed time.

The next morning the same weather pattern repeated giving another inch of rain. The forecast expected the same every day until Friday.  It hadn't rained enough to get the creeks running but the constant showers would ensure the dirt would not dry out.

We were only able to work a couple hours each day.   What work could get done was slowed by the mud.  We decided to go home after a couple days even though we planned to stay the entire week.    The weather forecast had been accurate so far and there was no way we would use the forty hours equipment rental. CAT was willing to just charge for the eight hours we used instead of the forty hours we scheduled.

I got stuck on the way out on the main road.    There was a channel about a foot deep and six inches wide that one side slipped into.  I always assumed the possibility of getting stuck on the quarter mile leading down to our property but not on the main road.   It was almost inevitable because I was pulling the tractor grossing about 14K pounds and the oil company hasn't been maintaining the road since we bought the property.   I walked down to the dozer and used it to pull the truck out.   

The plan had been to improve the land with ponds and extra food plots then prepare for hunting.   We didn't get anything completed due to the rain.  It seems the biggest priority will be improvements to the road.   Ideally, we would come out for weekend get-a-ways and hunting.   A washed out road or getting stuck in mud would be difficult problem with the closest person being a forty minute drive.  The thought of having to walk that distance in freezing temperatures is not pleasant.  Usually, we bring the jeep with us thinking it would be able to get the truck out if there was a problem.    I want at least another option.   I scheduled to get a 16,000lbs winch with a new bumper installed on the truck next week which will allow the truck to pull itself out.  

I think the best option to improve the road is a layer of gravel. I estimate it will take 200 tons of gravel to fill in bad spots and cover the road to our property.   The road is a little over a quarter of mile (.27) from the well pad to the RV.   It's about ten feet wide and a depth of three inches.    This is over 3,500 cubic feet of gravel.    It would take 188 tons of gravel at 19 cubic feet per ton. 

The total price for the gravel will be around $7,000 including delivery. It also means we won't get the tree work done or be ready for hunting season this year.  We will have to make a trip out there before winter to prepare the RV and perhaps have a load of gravel delivered to fill in the bad areas.  It will be worth the delay for a little more peace of mind.

Land: A Place to Lay Your Head

Previous: A New Start
 

It's mid summer and there's no way to build a cabin before hunting season.  Our general rule is to stop all major changes to the land at least two months before hunting season so the deer will establish a pattern.    I believe the improvements will be worth it in the long term, but I they will most likely have a new pattern this year.  

On a typical trip, we stay in a hotel and go out to the property to work from morning to dark. We did this because being in town was convenient and comforts of the hotel.   We need to reduce the cost from  the hotel and gas not to mention losing time due to the extra driving.    We only stay in the camper when we are there to hunt and neither of us are excited about spending another night in the old camper.

Travel Trailer (RV)

We decided to buy a used RV to put where we cleared trees for the cabin.  Technically it's a "travel trailer" but RV just sounds better.   RV are self contained living quarters and can provide all the comforts including showers and toilets.   We searched around Facebook and ended up buying a used one from a local dealership after dealing with a few shady individuals on Facebook.    The first Facebook seller we talked to wanted a deposit because we it was the weekend and the bank was closed.   He called the next day and told us that he could no longer sell it to us.     It took a full day of chasing him around the city to get out deposit back.

We spent a couple weeks replacing roof vents and the external lights.     We cleaned it up and stocked it.  We didn't have any issues on the highway except we lost the furnace cover.    The truck's transmission didn't like pulling it up the mountain and over heated.     It was a huge relief to get it to the well pad where we would spend a couple of nights until the road and site could be finished.

The Last Mile

Initially, we thought we could transport the concrete from the truck to the build site via a dump trailer.   However, pulling the RV down to the location proved that would not work.   The road is only about 10 feet wide which is about the same as the trailer.   One of us had to drive the truck while the other guided to avoid major obstacles.  We will need to widen the road to at least 12 Feet and the turns to 16ft. The truck alone has a turn radius of 50FT so we will have to clear more area at the site to allow for the truck/trailer to maneuver.    If we transport concrete down to the site then we must be able to move as quickly as possible.

The RV was damaged while moving it due to narrow roads and debris in the road.  I was unable to avoid major pot holes on the oil/gas road and our road was barely wider than the RV.     The grey water tank is leaking somewhere and one of the stairs was destroyed.   We will have to fix these on one of the next trips.   

We place cinder blocks as stairs as a temporary solution.   I don't know where the grey tank is leaking from.    I think it may have been damaged coming down the oil/gas road when I hit a large pot hole.   It's possible it was just worn out and the bump pushed it over the edge.  It was slightly leaking when we had it at our house.  I will have to check it and get replacement parts for the last trip before hunting season.

The bath tub has a crack.   It appears the RV did not have enough support under the tub and flex of the plastic eventually caused it to crack.     The previous owner patched the hole with duct tape.    I believe I can fix it by filling underneath with foam and an epoxy patch.

Moving in

Once the RV was at it's new home we made a trip down to the old camper to pick up all out stuff.   The RV has a lot more space available than the old camper.    We also have a lot of stuff that we won't need any longer.     The portable toilet is a good back up in case the RV breaks.     We probably won't need to use the small 1lbs propane bottles anymore since the RV has two 30 lbs bottles.    For now, the extra stuff will stay in the old camper.   At some point I want to remove the old camper and let that area go back to nature.

What's in the Box

The RV is 30FT long and includes a full kitchen, queen size bed, shower and toilet.  This is a 5 star hotel compared to the nights we stayed in the old camper.    RVs run a duel power system at 12V (Battery and towing vehicle) and 120V system supplied by an external utility plug.   Everything runs off the 12V except for the air conditioner, outlets, and microwave.    The water heater, refrigerator, and furnace will run off 120V if it's available but they can also use propane and the 12V system.

Water

This RV has a 40 gallon fresh water tank with a utility connection.    The grey water has a 40 gallon tank which is where the water from all the drains go except for the toilet.    The black water is also 40 gallons and stores water directly from the toilet. The waste water is easy to dispose of.   Portable tanks are available for draining the tanks and transported to a disposal location.  

The next problem is a fresh water supply.     The onboard tank only holds 40 gallons and conservatively we could keep our usage to 10 gallons per day.     However, we would still need a way to bring water out there until we have a water well drilled.

 

We found a food-grade water totes on Facebook for $150. We filled the tote with water, soap,and bleach then let it soak for a day to clean it out.  These versatile tanks have many options available.    I got an 2" adapter to a garden hose.  It's better to use an adapter with a metal connector since the soft plastic of the other stripped easily.  I attached a water pump for RVs from the tank to the RV.     The RV water pump is a 12V pump that has a pressure cut-off switch built in.    It will run off the RV's battery and keep the pressure from the tank at 45 psi.   The tank can hold a 275 gallons of water but our trucks aren't able to carry that kind of weight.   Water weights about 8.3 lbs per gallon which means we could only hold 175 gallons in a 3/4 ton truck.       In our initial trip we filled the tank to 125 gallons which is probably the max we could do and safely navigate the roads in the area.    We could fill the tank completely using the trailer since a full tank will weight as much as the tractor.    However, this will mean bringing two trucks again.

We spent a week there while moving the RV in and working with the dozer.   After four days we used the 40 gallons and needed to use the tote to refill the tank and provide water for our shower.  I missed an adapter and ended up with two male ends of the hoses.   I manage to connect the two hoses with a generous application of duct tape so we could get by until we could get a proper adapter the next morning.

Electricity

The 12v system runs off a marine battery with 75 amp hours.    I expanded the capacity by wiring another battery in parallel which doubled the Amp hours available to 175ah.    In the summer months we can bring in a generator to keep the battery charged and power the air conditioner.   

However, when we come out for hunting I worry that running a generator will be too noisy although we couldn't hear the generator 200 feet away.    This is probably due to the topography of the land.   The land drops 150 ft in elevation a few hundred feet from the north border.    We couldn't hear the generator at the bottom of the hill.  The deer didn't seem to mind either.    We noticed several in the area even thought the generator was running and we were moving around and talking.

The generator has 4500 running watts with a five gallon tank that ran for 12 hours.   The RV needs a minimum of 3600 watts to power the RV.  (120V X 30 AMP)   It's not cost effective for us to have the electric utility installed due to the minimum cost of $30,000 to run 1.25 miles to the nearest poles.     The only option for us would be to install an inverter on the battery to run the 120v system.    A combination of solar and wind could keep the batteries charged.    The problem is solar/wind is an unreliable power source.     During the week most days had little to no wind with the average temperature around 95F and 65% humidity.   The sun was available half the time due to clouds which means we would have drained the batteries in the first day.

It would be unlikely that the solar/wind would supply enough power during the summer time.   However, during the winter the furnace runs on the 12v system and doesn't draw as much power as the air conditioner. 

Stability

I think we will need to put the RV on more permanent footing.    It normally sits on duel axles with jacks to level and stabilize it.    This wasn't meant to be permanent.   The tires will degrade over time and eventually lose air.    The jacks aren't meant to carry the weight of the RV so a flat tire will cause the RV to shift.    The frame is a H pattern and I think we can raise the RV to place cinder blocks at the corners and middle.   To set a mobile homes they will raise and lower the tongue like a sea-saw to place blocks in the lifted area.    

We already have a lot to do next year

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