The Hack My Solar Podcast

January 2018

As we sit here in the dead of winter dreaming of spring but also enjoying the reduced pace of the winter on the homestead, I thought it would be a good time to give an update as to where we are with our projects around the homestead as we build towards a more self sufficient lifestyle. One of the nice things about winter for me is that I can more easily control the climate within the house. Obviously during the summers with a house that doesn’t have central AC and is limited to the energy that can be produced by the sun, and with the understanding that solar thermal is much more efficient than solar photovoltaics, it can be a struggle to keep the house comfortable during the day. Cooling the rooms we are in only, combined with strategic shading and plenty of personal level fans for moving, ends up being a good strategy. However in the winter, where we heat almost exclusively with wood, utilize proper clothing and nice comfy thick blankets on the beds, it is much easier to dial in exactly the climate we want.

The kitchen remodel has progressed to the point where the kitchen is completely functional again, albeit not completely finished. It turns out going from standing tree to kitchen counters and cabinets isn’t as easy as it doesn’t sound! Now that it is really too cold to work full time outside in the cold, I’ve decided to table this project until next Fall.

Another nice thing about the winter is that we are no longer using irrigation water, so we are definitely catching more rain than we are using, and this will likely stay that way until the dead of summer.

The combination of no cooling, less water pump use, and less power tool use leads to a nice capability of only having to run the generator when we are equalizing the batteries, which can be once a month. Even in the winter where we get less battery capacity, we rarely if ever need to run the generator to add capacity. Clothes washing and dish washing is still done in the middle of the day when the sun is full on the solar panels, but we do end up taking things to the laundomat in town to dry sometimes.

We did lose our chickens over Christmas while we were out of town, not sure what but something got into the chicken pen and wiped them out. I’m thinking about putting another enclosed area up near the house and perhaps moving them up there in the winter because we have no need to walk down to the garden in winter other than the chickens and bringing them closer to the house will bring them closer to human and dog smell, as wlel as providing an opportunity for us to beef up that enclosure to help protect them.

We did decide to liquidate our quail flock, which ended up in a great graduation ceremony for the birds and very nice BBQ to follow. We did find these birds were a bit more tough than the ones we had graduated right around 7 or 8 weeks. That being said the flavor was very good, but I may alter the preparation method the next time we process mature birds. Im thinking a long and low smoke with a nice purpose made rub.

We’re starting plans to erect a 10’ uncovered extension to our existing back deck, and enclose the covered portion of the deck, specifically to provide a nice place to be outside in the winter but out of the elements.

We did lose our hot water heater, and I’m hoping it is an easily fixable electrical issue, as the fuses were blown when I took the cover off, but if not we will need to replace the hot water heater, yay! That will be a project for next week, but luckily we do have a backup water heater in the bathroom that allows us to take showers with a 20 lb propane tank, but we can also wash dishes in the tub, and put the dish drainer in there as well. Its not ideal for either weater efficiency or back pain, but it works.

We also have some extra dish strainers and some plastic tables so setting up an outdoor dish station to run through a big batch of dishes is al...

The long and short of it is that it wont.  Join us today as we discuss how the momentum in the solar industry has already reached a point where it will continue to build.  Solar Jobs were 2nd in the energy sector behind oil jobs, and demand is only going up as worn out coal fired plants come offline, utilities respond to the public sentiment, and people take advantage of federal, state,and utility level incentives.  I discuss how I think China is competing with us on the R&D side and that we could lose our leadership on this front during the current administration.  The reality is that coal jobs aren't coming back.  Storage and Natural Gas technologies will fill the off peak generation gap and as they become cheaper the switch becomes even easier.

Battery Maintenance

Today we will discuss battery maintenance.  It is one of the big differences between a grid tied and an off grid system.  A grid tied system just sits there and generates electricity either for your home use or to be fed back onto the grid.  The battery bank in an off grid system adds a whole new level of complexity.  We have previously discussed the types of batteries but for the purpose of this conversation I am going to focus on lead acid batteries.  Here are the primary topics for discussion:

The Chemistry behind discharging and recharging batteries

Standard Maintenance

Charging Cycles

How to measure Specific Gravity and Equalization(overcharging)

After listening to the podcast if you have questions please email them to me at [email protected] or add them to the comment section of the blog.  Additionally you can go to our Facebook page to get more information or to ask questions.

 

Today we are going to discuss Inverters and the balance of system components.   Inverters are the component that takes the DC(Direct Current) Provided by the solar array and stored in the battery bank, and converts it to AC(Alternating Current) for your home use.  Alternating current means that the current alternates its direction over and over again(every 8 milliseconds) to create a nice wave pattern.  It goes up, rounds off, goes down, rounds off, and repeats.  

You want to match your inverter to your battery bank, so if you have a 24V battery bank you don't want to buy a 12v solar inverter.  Once you have cut out or reduced usage of all the devices that you can, you need to do an analysis of the devices you still have and how often they are used to understand what the demands of your inverter are going to be.  You need to look at both the peak or startup loads as well as the running loads.  For example a refrigerator compressor may draw 5 times its running amps for half a second while starting up.  There are many tools on the internet that can help you with this as well, my favorite is over at the Alt-E Store.  Once you have your total Watt-Hours per day and your peak loads you can decide on an inverter.  

Here are a few things you need to consider while evaluating solar inverter choices.  

Pure Sine Wave vs. Modified Sine Wave - these are the two main classes of solar inverters you will be looking at.  Sine waves are that nice up and down curve I spoke about before with rounded peaks and valleys.  Pure or True Sine wave Inverters create AC electricity that is just like the grid power.  Everything in your house was designed to run on true sine wave.  But that doesnt mean that it can run on Modified Sine Wave.  MSW is more blocky than TSW.  MSW goes up to peak for a few milliseconds, goes to zero for a few milliseconds, and goes down for a fe milliseconds and then repeats.  High tech and sensitive electronics may have problems with Modified Sine Wave.  Personally, with the price difference not being that much anymore, I would go with the TSW to ensure that I wasnt going to have problems.  ANother option would be to have a MSW inverter for normal loads and a seperate smaller TSW inverter for finisky loads.

Inverter/Charger or not - An inverter/charger is a combination of an inverter, battery charger and transfer switch into one device. When a generator is on an hooked up, or you are hooked to the grid, the inverter recharges the battery bank. It also allows any surplus AC power to pass through and power houseAC loads, such as a television. When AC power is disconnected, the unit inverts DC battery power into AC electricity.  I would advise using this because it makes adding a generator to the system plug and play.

 Future expand-ability - Some solar inverters play well with others and can be wired in parallel to expand the system and others cant.  If you are building out your system slowly this may be a consideration you should make.

 

Balance of System - The balance of system is simply the other components you need to complete your system.  These include wiring and combining the solar panels, fuses, safety switches, battery cables, disconnects, monitors and controllers or data displays, and mounting systems.

Batteries for Solar Off Grid or Hybrid System

OK everyone, we have covered solar panels, a solar array, and charge controllers, so the logical next step is for us to discuss batteries.  Over the lifetime of your system, Batteries will be the most expensive part because the ones that are cost effective when starting a system don't last very long and the ones that last a relatively long time are prohibitively expensive.   Batteries are the center cog of any system because they store the excess energy produces by your source(solar array, generator, or even the grid) and then distribute that energy when generation falls below need.

Here are a few things to remember when considering a battery bank:

How many days of autonomy do you want?  So if your panels stop producing, how long do you want your battery bank to be able to provide energy to the house?

What climate will the batteries be stored in?  Batteries are rated for about 80 degrees, if they are stored at below freezing conditions, you may need 50% more capacity to meet your needs.  A cruel fact is that when its cold you normally have less sunlight as well.

What voltage will your battery bank be?  12v systems are easy but when you start drawing a lot of current it makes sense to step up to 24v or even 48v to reduce the wire size and reduce the number of parallel strings.

 How committed to maintenance will you be?  If you want plug and play batteries that you rarely need to visit, expect to pay more than for minimalist flooded lead acid batteries that require regular measurement and maintenance.

We are going to discuss the main categories that batteries fall into and how to use them.

Flooded Lead Acid Batteries for Solar such as golf cart batteries are the most common off grid battery bank component.  They are the lowest cost option, last between 4 and 7 years depending on how well they are cared for and what depth of discharge you normally take them to, and will work pretty well even if you dont religiously equalize and fill them.

Sealed Batteries for offer some advantages over Flooded Lead Acid because they are relatively maintenance free.  They only require a regular full charge.  They dont spill or leak fluid, they can be installed in any orientation because you dont need to get to the tops to fill the electrolyte.  They are expected to last around 8 years when protected from overcharging.

Lithium Ion Batteries are the wave of the future, offering 2x the average lifespan of a lead acid battery with higher Depth of Discharge, smaller space and about half as heavy per kWh of storage.  The problem with them is that the current charge technology in the market hasn't caught up with Lithium Ion and they are very picky when it comes to overcharging.  Currently I would not recommend Lithium Ion batteries for solar until more research and development is done.  The Powerwall may be a solution for grid connected hybrid systems but that's a specific niche that would require its own article.

Nickel Iron Batteries are the most expensive but also the most bulletproof batteries for solar systems on the market.  They can take 11000 cycles at 80% depth of discharge, with a wide range of operating temperatures and resistance to both over and under-charge conditions.  Unfortunately they are very expensive.  If you are looking for a battery that will last as long as your solar array, with low maintenance and have the financial means to utilize Nickel Iron this is the battery choice for you.

Well i hope you learned something today, bear with me as I continue to convert the blog to a podcast.  I am self teaching as I go and watching a ton of youtube videos and reading a bunch of articles, but implementation will be hit or miss.

Charge Controllers, what are they?

OK so we have covered what solar panels are, and how to design a solar array,  but what happens once your panels are generating power?  Well you obviously want to get them into your battery bank, but other than some very specific situations, you will charge your batteries through a charge controller.  So what is a charge controller...in essence, it is the device that regulates the amount of energy, both in terms of voltage and amperage, that goes from your solar array to your battery bank.

Charge controllers come in two primary modes, Pulse width modulation(PWM) and Maximum Power Point Tracking(MPPT).  Pulse Width Modulation Solar Charge Controllers reduce the amount of voltage applied to the batteries in an inverse relationship to the charge level of the batteries.  So as the state of charge goes up, the voltage is reduced so as not to damage the batteries.  MPPT Solar Charge Controllers match the incoming power from the PV array to the most efficient use of that power in terms of charging the battery.  This allows the array and the battery bank to be vastly different voltages.  The ability to step up the voltage and therefore reduce amps(because watts always equals amps x volts), especially if the array is sited a long distance from the charge controller, can allow a person to pay for the charge controller in wire savings.  This is because higher voltage/low amp power can run through thinner wires from the PV array to the Charge Controller.  To give you an example, using 6 gauge wire vs. using 2/0 gauge wire can save you nearly 70% in wiring costs.

We will dig into MPPT chargers in more depth at a later date.  Feel free to ask questions in the comment section below.

Sizing a Solar Array

A Solar Array is just a fancy term for your solar panels, which themselves are combinations of solar cells, combined into a single system.  Today we discuss "sizing a solar array." The first step is determining what your needs are.  It is always good to eliminate or reduce some parts of your usage before determining the size of your solar array.  For example at our house we got rid of our drip coffee maker and began buying roasted beans, hand grinding them, heating water on a propane stove, and using a french press.  The amount of electricity we need to make our morning coffee is now zero.  Switching to LED lighting, putting appliances on surge protectors that we turn off when not using, and drying our clothes on the line rather than in an electric dryer were some other adjustments we made before going off grid.

If you are currently on grid, you have a very easy meter to determine your usage in your monthly electric bill.  Depending on your climate, you may see higher usage during certain times of the year.  For example in TN, we saw summer months where we were cooling with electricity as our major power need.  One hard rule we have living off grid is that we don't use electricity to generate heat.  No electric furnaces, space heaters, microwaves, hot plates, crock pots, or electric water heaters for us.  So my suggestion would be to reduce your consumption as much as possible, then review your bill to see how much electricity you are using.  In the US, the average utility customer uses 901 kWh per month of electricity. Your bill will be denoted in kWh which means kilowatt-hour,  Or 1000 watts for 60 minutes.  For the sake of this example, lets assume that you have dropped your consumption to 450 kWh per month(half the average household).  So on average you are using 15 kWh per day.  Once we have this information we need to look at an insolation map, which will show you the average daily hours of sun you receive in your location. Here is a map of the us provided by the NREL.

Armed with the insolation data you have for your  location, back to sizing a solar array.  You need to divide  your daily use by the number of hours you get.  The NREL posts maps for each month so you could break this down month by month and use the worst case scenario if you like.  Where I live in TN we average 4.5 sun hours per day.  This means over the course of an average day, we get the equivalent of 4.5 hours of full sun.  So using our above number of 15 kWh per day and 4.5 average hours of sun, the total array size that I need is 3333.33 watts.  You will notice I went ahead and made the conversion from kWh to watts.  Now you can figure how many panels you need in your array to meet your needs.  You may decide you want to replace 50% of your needs, or you may go all out and decide to take out all 3333 1/3 watts.  Lets take the latter and assume we are going to get a great deal on 10 or more 310 watt panels.  We divide the wattage of the panels into the watts needed, so 3333.33/310, which gives us 10.75 panels.  My suggestion is to increase this number by 25% to account for losses at different points in the system(which we will discuss later).  Doing this gives us 13.44 Panels, which we will round up to 14.  If you followed along, you now now exactly what your usage is, how much you want to replace with solar, and how many panels you need at a specified wattage to meet your needs.  We hope this post on "Sizing a Solar Array" was helpful.  Shot us an email on our Contact Page if you have any questions we would be happy to help!

How do Solar Panels work?

Solar, or Photovoltaic, Panels work by converting light energy from the sun, or photons, into electricity through the "Photovotaic effect."  Interestingly, a French physicist built the first ever photovoltaic cell at 19 years old, in 1839.  The first practical photovoltaic cell was demonstrated by Bell Laboratories in 1954 and early on they were primarily used in space.

A Solar Panel is a collection of solar cells that are made up of semiconductors.  Semiconductors absorb the photons--through a process I wont describe in detail--and cause electrons to be excited and break free to be converted into usable DC electricity.  Solar cells are arrangements of silicon "sandwiches" where one layer is activated with boron and the other activated with phosphorus.  This helps the charge to be created and directs the free electrons to the wiring that leads to your charge controller.  

The key to remember here is that its the light energy that is converted to usable electricity, so when siting a group of solar panels, also known as an array, you should do an insolation analysis, which is a fancy phrase for looking at whether or not you are going to have full sun hitting the panels or if there will be shadows cast from structures or vegetation.  A part of this analysis will also be determining how much full sun you get in your area and using that information to determine how many panels you need to charge your battery bank.

This post is about "how do solar panels work" but now that you have a basic understanding, here are a few things to remember that can reduce to the amount of energy your panels can produce:  dust/pollen/leaves, temperature, and wire resistance.  If you let your panels get dirty or accumulate leaves or snow, it should be quite obvious that the light cannot reach the covered up cells, which will logically result in less energy production.  When your panels heat up, they also become less efficient.  Remember above when I discussed the electron becoming excited and breaking free?  Well the hotter the cell gets, the less potential there is between the different electrons because the ones that are at rest are already a little "excited" because they are hot.  As a matter of fact when sunlight shines in through your window and heats the air in your house, this is specifically due to excited particles, and its no different with a solar panel.  We will discuss wire sizing in more detail in another post, but remember that current is measured in amps, and wire resistance simply means that smaller wires cannot handle high amps.  This is why we use ideas such as stepping up voltage the reduce the number of amps required to move the same amount of energy.   Amps x Volts always equals Watts so increasing one number always decreases the other.

 

Types of solar installations

 

There are a variety of ways to harness the power of the sun. Today we are going to define the ways and discuss them:

 

Grid Tied

Off Grid

Hybrid

PV Direct

Solar Thermal

Photosynthesis

 

Grid tied

Grid tied systems are solar installations that are implemented on a property that uses utility energy from the grid.  These systems reduce the amount of energy purchased from the utility company and the amount of energy not purchased is used to offset the cost of the installation.  These systems must have safety switches that cut the connection off when the grid goes down so that you are not feeding solar energy onto the grid while linesmen are trying to make repairs.

Off Grid

Off Grid systems are solar installations that generate and store electricity in batteries for use when the power needed is greater than the power being produced, such as at night or on cloudy days.  These systems are not tied to the grid and do not have safety cutoffs.  Many people install off grid systems to provide power only during power outages, and only to power certain appliance such as refrigerators to avoid spoilage.  Others have full off grid systems on hunting cabins or remote properties where there is no access to utility power.  Many times off grid systems will include a Generator to keep batteries charged up during period of prolonged low generation or high usage. 

hybrid

Hybrid systems are grid tied systems with battery backup.  They add a layer of complexity because not only do you need to keep your system disconnected from the grid when utility goes down, but you need to switch over to battery power, and for most people drastically reduce your energy consumption.  The typical battery bank cannot support the typical household usage for very long.  These systems sometimes add yet another layer with a whole house generator.

PV DIRECT

PV Direct is the most simple way to implement a solar electric system.  This system utilizes a PV panel wired directly to a load such as a solar powered water pump.  This is a great way to utilize water as a battery, as in pumping water to a higher elevation and then letting gravity distribute it. Another option would be to use a solar panel wired to a fan that circulates hot air out of your attic to assist with colling your home, or even blowing air on yourself.

SOLAR THERMAL

Solar thermal is probably the second most efficient way to utilize the power of the sun and it is quite simply to use the radiant heat from the sun to reduce energy needs for heating.  This could be heating water using a solar water heater, heating air, or heating a thermal mass such as when passive solar is used to heat a house or greenhouse by storing heat and releasing it over time when the temp drops.

PHOTOSYNTHESIS

Photosynthesis is the most efficient way to utilize the power of the sun as we combine that power with nutrients in the air and soil to allow plants to produce food, shade, and building materials for us.  We would be remiss to create a solar site without acknowledging the power of photosynthesis and developing ways to leverage it to our own benefit.

 

Energy vs. power

This short series is to help build some foundational knowledge that will help you understand the building blocks of Solar.

energy

Energy is the capacity to do work.  Measurements for energy include calories, BTUs, Joules, and Watt-Hours.  We would use the term energy when discussing how much capacity you have in your battery bank.  If you are on grid you will get a utility bill from the power company and that will normally provide you with the number of kWh or Kilowatt-Hours you used last month.  A Kilowatt is 100 watts and a watt hour is one watt being used for one hour.

POwer

Power is the rate of consuming or producing energy.  Watt is the unit of measure we use do discuss power.  A watt is defined as amps multiplied by volts.  A solar panel rated for 100 watts can produce 100 watts ofpower at any given time under perfect conditions.  If it produced those 100 watts for 1 hour it would store 100 watt hours of energy. Understanding that a watt is always equal to one volt multiplied by one amp will be very important as we continue this series.  

 

Two considerations when sizing solar systems are how many watt-hours of storage do you have(ENERGY) and how much power can the system deliver at any moment(POWER)