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System design, analysis and marketing

This is a long, but extremely important page to read if you are seriously considering purchasing an "Off Grid" Solar Power System and should be read right through to the end to avoid many of the pitfalls that are encountered by people. Quite frankly, there is some seriously flawed information on other websites, even though the claim is that the sizing and product selection is based on experience, testing etc. Most of the misinformation and misleading information relates to the battery type, size, longevity and the sizing of the solar array. While the pricing may seem quite good and appealing, they are not sized and configured properly.

One of the most important things that we have learned over the years is that even though climate data and manufacturer's specification can work well with grid interactive systems, they can be very misleading when looking at "Off Grid" Solar Power Systems. To properly size and design these systems, you really need to live with an "Off Grid" power system and watch its behavior and take note of weather patterns.

For this discussion, we are going to look at 2 of our systems, one from the Competitive series and one from the Full Service Properly sized and designed series. When you look at these 2 systems, they look fairly similar at first glance, but there is a significant difference. The pricing and components will change over time a bit, but the general comparison will continue to stand. First though let's have a look at this.

The Marketing Department.

The marketing department's job is to create materials to boost sales, therefore the focus is on the dollars that the company is going to make. Marketing department personnel know the following:

  • Most people are looking for the absolute cheapest ("most cost effective") product. (This is likely the main reason why it is so hard to get quality merchandise anymore and why so much manufacturing has moved off-shore).
  • People are turned away by "sticker shock", so try and make it look like people are getting a lot for as little as possible.
  • Packaging makes all the difference, so make sure it looks great.
  • People are generally impressed if you give data and reassurances that they are getting a top notch product based on the best scientific and engineered data available.
  • People like seeing the words discount, sale etc. to make them feel like they are getting a real deal. Frequently, a "regular" or "list" price is stated with a "Sale" price along with it.
  • If you make the purchase easy, i.e. pay with a credit card, financing options etc., people will be much more likely to buy. (rest assured that the costs for this are hidden somewhere. It costs the retailer several percent to accept a credit card and your local bank will likely give you a better rate than either the credit card company or the financing company, so check it out). They know that if the price is given as a monthly amount, people will be much more likely to buy or rent. This is becoming quite evident in many different areas, but do the calculations and see what it costs per year and what the total amount that you pay actually comes too.
  • If you include free things like shipping for example, people will be more likely to buy (again, these "free" items are just hidden in the pricing somewhere).

The Competitive series "Canadian" as portrayed by the marketing department.

The "Canadian" features an Outback Radian 8000 Watt Inverter/Charger with industry leading features such as Dual AC input for Generator and Grid interaction, 120/240 VAC output, advanced charging profiles for new battery technologies and a myriad of other innovative features. Outback Power is one of the most trusted names in the industry.

A quality 6000 Watt Hanwha Solar Array with a linear 25 Year output warranty is standard equipment.

The Midnite Classic 83 amp charge controllers incorporate leading MPPT technology along with Arc Fault protection and a myriad of features. The Classic is internet enabled and is able to send out operational data which is logged and displayed on the Midnite website for free! You can then look at the data that has been logged on the Website by simply logging into your free account. The Classic also incorporates a state of charge meter so you can monitor the batteries.

Two banks of quality Rolls S 480 batteries provide 960 Amp Hours (46KWH) of capacity.

The Outback Mate 3 controller is used to program and observe the system. It features an easy to read graphical and numerical display along with data logging capabilities. The Mate 3 is also Ethernet enabled to allow for remote supervision of the system.

An easy to read temperature compensated Hydrometer is included.

This system also includes integration Hardware, battery interconnects, inter-module wiring and combiner boxes.

Ground or roof top mounting system is included. The base for the ground mount system is to be customer supplied.

Installation and GST is not included.

Based on Natural Resources Canada RETScreen analysis, for the Calgary airport location, this system would generate 7907 KWH per year based on a 74% system efficiency. That would give you an average of 21.7 KWH per day! This is the amount of energy that an average Calgary home would use.

If you were paying an average of 20 cents per KWH with all the fees from your electricity provider, this would give you a savings of $31,628.00, and that is not even including the rate of inflation! This works out to $ 131.78 per month.

For only $ 116.25 per month, this system will save you money and you do not even have to pay for the installation of the electrical grid to your dream property.

The Facts of life:

Let's start with looking at what is true. The description of the product is true, the theoretical KWH per year is true as is the rate of electricity. So that is the problem then?

First of all, consider the basis of the calculations. The average consumption of a Calgary home is about 21 or 22 KWH per day averaged over the year. Now, usually there is a higher consumption in the winter because the heating system is running and the lights are on more. Not only that, people would tend to be home more in the winter, especially on bad weather days and therefore use more power at that time.

Next, for those of us who have lived for a while, we know that the weather is not average every day of the month. We get a few really sunny days, a number of sun and cloud days and stretches of bad weather. Not only that, consecutive years do not have the same patterns, nor is any particular year normally an average year. The weather data is an average over quite a few years, so expect some years to be better, some worse.

Furthermore, when we analyse the system, the battery bank is actually quite small for what it is supposed to do. We have L 16 size batteries with a rated capacity of 46 KWH. A battery should not be discharged more than 50%, so that leaves us with 23 KWH of stored energy. Next, the rating is the 100 hour rate based on a specific gravity of 1.280 as per industry standard. The batteries would have a 24 hour rating of 366 AH or about 35 KWH which would leave us with about 17.5 KWh of usable stored energy and we are likely consuming about 30 KWH per day in the winter. OOPS!

OK, then let's say we have cut our energy consumption and live more efficiently than the average Calgarian. So let's say we were able to cut back to 14 KWH per day in the winter. Now we have 17.5 KWH a day of storage. So what happens in winter then? Well, let's say we actually did have a good solar day and the batteries were totally charged, there is no sulfation and they are not at the beginning or latter part of their life. (By the way, based on experience, this does not normally happen and the actual capacity is less). The sun does not provide much power after about 4:00 PM and really does not start to charge the batteries again until about 10:00 AM, that is about 18 Hours of running without an input, so what happens? Well we have 17.5 KWH of available stored energy and we just used up 10 ½ of that overnight. Leaving us with 7 KWH to use. Yikes! If we have some bad weather that day, we only have 5 hours left before we hit the 50% mark. Better run the generator. Oh no! It won't start because of the cold and we are out of power in the battery bank to run the block heater. Not only that, we had a heavy dump of snow overnight and can't get out of our place for help. Now what?

OK, let's say the generator did start and we can charge the batteries, so now we are going to run the generator for several hours. The batteries will only accept so much charge, especially once you hit absorb voltage, so you are likely going to run the generator about 4 or 5 hours every time you do not have a sunny or at least moderately good day.

So what does this do to our battery life? Well, let's look at the chart below. If we were to have an average discharge of 40%, the number of cycles is about 1600, which means about 4 1/3 years (this is quite normal for an L 16 size of battery of any good brand). If we were to have an average DOD of only 15% to 20%, then these same batteries would last about 2250 cycles or 6 years. Realistically, if you run an L 16 size battery this hard, you will likely get about 3 years out of them because there will likely be sulfation since it is highly likely that the batteries will not be charged properly all the time. How often do you want to replace the batteries?

Another point is that typically, we get some good days in a row, a number of "mix of sun and cloud" days and at times 2 or 3 weeks of overcast weather. If there is not enough available storage capacity in the battery bank, you waste a lot of the good weather energy and need to run the generator every time there is bad weather.

Is that what you were expecting when you moved out to your dream home and wanted to be independent and green?

By the way, the "Canadian" is great for a battery backup grid tied system or if a properly sized industrial battery bank is used, it would also make a great Off Grid package for an average winter time consumption of about 12 KWH per day or less.

The good news!

Boyd Solar does not have a marketing department! Our focus is on what is best for our customers, not the company bank account.

So let's take a look at the Pioneer 6000 package from our "Full Service" packages line.

The basics of it are: (you can look at the details on the packages page)

7.2 KW Outback inverter system

6000 Watt Solar Array

86.8 KWH industrial battery bank

Suggested usage: 12 KWH per day in the winter

So, what makes this package different?

The most important aspect is the properly sized industrial battery bank. Being a higher capacity bank, it will have more relative capacity than one that is discharged faster, so here we would have 43.4 KWH of available capacity. In and of itself, this would give us just over 3 ½ days of autonomy.

Another factor now is that even on some bad weather days, we still get some input from the solar array, so practically speaking, we would have over 4 days of actual autonomy without needing to run the generator.

The larger battery bank now also allows us to store more of the energy from the sun on good days, which in turn then will reduce the generator run time and give us more actual usable power from the sun.

The Flexware series of Outback products has separate AC and DC breakers boxes which have a lot more room in them and are arranged a lot better than the sleek looking Radian series.

A really important point to note is that the sun is a lot better at charging the batteries than the generator. While a generator is technically able to charge them as good, the absorb stage of the charging process would see a lot of generator run time without a lot of energy actually being put into the batteries - not a very efficient or environmentally friendly way of charging batteries.

Additional advantages of the "Full Service" packages.

The industrial batteries are going to last a lot longer, typically in the 15 to 20 year range.

Have a look at the Life Cycle Cost analysis here for the batteries. Which are the most "cost effective" and which actually provide the best Value? More detailed information on the Battery page.

As it is obvious from the above charts, the industrial batteries are clearly the best choice. Look at how often you would be changing out the L 16 size batteries compared to the industrial batteries, especially when they are undersized and cycled to a greater DOD (depth of discharge)! L16 size batteries should not really be considered for a serious Off Grid Home.

Many people are not actually aware of the difference between batteries, so what is the difference between L16 size batteries and Industrial Batteries?

  • The main difference is the thickness of the plates, which translates into a much better lifespan for industrial batteries and also increased performance. For example, a Rolls 5000 series battery has a .260 thick positive plate, whereas a 4000 series battery has a .170 positive plate.
  • The 5000 series has a 3 mm separator whereas the series 4000 has a 2 mm series separator. The 3 mm separator provides for better electrolyte flow.
  • The 5000 series has a dual wall container for environmental protection and strength. The built in handles make it easier to move the batteries.
  • The 5000 series batteries come in higher capacity batteries to allow for single string sizing of battery banks, which again reduces the amount of wiring, maintenance and problems associated with multiple strings.
  • The 5000 series includes the battery cables.

There are more included items, for example, the battery safety disconnect, conduits and fittings, the required code diagrams, labels and placards, battery box ventilator and a battery care package. Some systems also include the battery box.

The Main Parameters for system sizing:

The 3 main components for a Solar System are the Solar Array, the Inverter and the battery bank. Each component is sized on different aspects of the installation.

  • The Solar Array size is based on the number of KWH per day in winter (December and January) and for South and Central Alberta or similar location should be a minimum of ½ the KWH per day. For example, if the projected usage is 12 KWH per day, the minimum size of Solar Array would be 6 KW tilted at 65 to 70 degrees.
  • The inverter size is based on the maximum load that could be on at any given point. For example, if the largest demand is going to be 3000 Watts, we would have a minimum inverter capacity of 4000 Watts. It is not a good idea to push this to the maximum, always allow some headroom. The inverter will last longer as electronics do not last as long if they operate at the max.
  • The battery bank is based on the daily usage and the number of days of autonomy. The days of autonomy should be a minimum of 3 days at 50% DOD. In this example then, we have a daily usage of 12 KWH which would require a battery bank sized as follows. 12 KWH X 3 X 2 = 72 KWH or 1500 AH at 48 Volts for a 3 day autonomy or 12 KWH X 5 X 2 = 120 KWH for a 5 day autonomy. We would then look up the rating and see what the closest battery is to that value. Always round up! A Rolls 5000 series 4 KS 25 PS would be a good choice at 86.8 KWH (1808 AH at 48 Volts). The Rolls 5000 series 2 KS 33 PS would be an even better choice at 113.6 KWH (2366 AH at 48 Volts).
  • The larger battery bank will allow for more storage of good weather energy and will last longer, since the DOD will be less.

When sizing a system it is important to look at what is truly the most "cost efficient" system. "Cost efficient" being defined not, as the cheapest up front price, but rather being defined as the best value. For example, in the above comparison, we have one system at $ 27,900.00 (at the time of this comparison in 2014) and the other at $ 42,800.00 (at the time of this comparison in 2014). Most people are going to look at this and say "that's an easy choice – the first one is a better value. In reality, though this is not true. The first system is going to waste more good weather energy, which will require more generator run time, fuel and maintenance. Just the fuel for the generator will likely be $ 8,000.00 or more over the 16 year lifespan of the batteries, and that is without allowing for the transportation of the fuel and the time to deal with the generator. The first system is going to cycle the batteries much more and the batteries are not rated for as many cycles. The L16 size batteries, when cycled this much are going to need to be replaced 3 times before the 5000 series battery will need to be replaced. The cost of those 3 replacement banks alone is going to be about $19500.00 not including installation or transportation costs. The second system also includes the safety disconnect, labels, diagrams and other items. When all these factors are considered, the second system actually provides better value and is more "cost efficient" over the life of the system and save you thousands of dollars and a lot of time servicing the system.

So why are L 16 size batteries used so much?

Primarily because they are cheap and look like a good deal at first glance. They are also readily available and, to a certain extent, a leftover from the time when Off Grid Solar systems were much smaller.

Let's also look at another item; the available and usable energy with an undersized battery bank and a properly sized battery bank. When a battery gets close to being fully charged (about the 80% mark), it starts resisting the current flow. This is called the "absorb" stage of the charging cycle and typically lasts about 2 hours. During this time, the batteries cannot receive all the available energy. Once the current is reduced to the point where the curve flattens out at the bottom, the batteries are fully charged.

The thing that we can see here is that after some bad weather, the larger battery can then store much more of the available Solar Energy, making it much more efficient and environmentally friendly.

Generators

Boyd Solar is a renewable energy dealer, not a generator dealer. A well designed renewable energy system will use a generator very sparingly, (should be less than about 35 to 50 hours a year). Systems that rely on a generator for more than 100 hours a year are more cycle charge or generator systems than Solar Systems.

Northern Lights diesel generators have a good name and can be purchased from Renown Industries Ltd.

Kubota generators are available from Frontier Power Products

Avoid cheap ("cost efficient") generators as they will just cause problems and not last. Some of our customers have had fairly good experiences with "inverter" type generators manufactured by reputable companies.

Generator Issues:

The main issues with generators have to do with starting and the output wave form. Even good generators sometimes have issues with starting, especially when they are needed the most and when the weather is miserable.

The issues that arise out of the waveform distortion, even with good generators can cause problems which range from heating, control systems and other items just plain not working or causing a light show with fluorescents or LED lights. With one customer we had to put in a second inverter strictly for charging the batteries as the generator caused too many problems with the heating and control systems to be able to use it to power the house directly.

This waveform shows the inverter waveform as produced by an Outback inverter. This is very close to a perfect sine wave and what we would expect to see. Everything works quite well with this waveform. (the grid power looks like this)

The next waveform is that of a good generator that is not loaded. It is a fairly good waveform with some distortions.

Now we take the same generator and load it down. See what happens to the waveform. In this case (with a relatively good generator and waveform) the distortion caused a light show with some of the LED lights with them going on and off. So with both of these situations, the RMS voltage was the same, the difference was the distortion in the waveform and the lower peak values. In other words the wave basically spread sideways with the top coming down, still giving the same amount of actual power but with a different waveform. I have seen generators with much worse waveforms than this one.

Please have a look at the rest of the website as well, as there is a lot of information to help in understanding Off Grid Solar systems and providing information to make appropriate choices for the type of system that you would like. We would suggest starting with going through the "Off Grid" pages starting with the Off Grid Solar Power Components page.

Off Grid Solar Power Components

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