Thinking Lean with Small Systems Solar





PART 1: The Big Picture
Introduction: Thinking Lean With Small Systems Solar

The Sample Area: Nations Geographic Center

The Horizon: How Sun Power Looks Through All seasons
The Instagram: Illustrating How Solar Systems Work
PART 2: What Matters
Thinking Lean: In System Design/Upgrades (Minimizing Waste)
The Way: Applying Lean Framework To Optimize Your Solar Vision
Value Stream
Continuous Improvement
The Real: Lets Water-Down present day assumptions

Core Values: Defining Waste In A Small Scale Core (Main) System

PART 3: Making It Happen
The Keys: solar system metrics, and their inter-relationships
Finding Your Path: Determining what You need from Your Main System





I believe what most people are looking for in a simple off grid electric power solution, such as for a minimalist tiny home or van dwelling, isn’t addressed often enough.  Often what you see is a scaled down version of a middle of the road mobile design. Most Small Systems Solar users are looking for something ultra-simple and modest, yet flexible and scalable.

My goal with this blog is to twofold – first to present a showcase of a practical example using Lean principals outside of business environment, secondly to provide a “Lean Principals” framework of thinking around solar design concepts to help in creating custom solutions to individualistic needs.

People looking for a guideline to small scale would be happy to discover a method/system of having just enough power to be self-sufficient in autonomously running electrical components/devices for which their daily lifestyle depends on, in the most efficient way, in the least amount of space, and at the lowest cost possible for dependable operation, for as much time as they see as practically possible. (100% self-reliance isn’t often practical for most people having very modest needs, and means).

The road to achieve this happiness isn't as straight forward as one might be lead to believe, because a single solution doesn’t exist today. The reality is that it is a balancing of trade-offs, and how to balance them is unique to each individual application.

Lean Principals are a practiced mindset that can help in working with that balancing act, in the best ways possible.

Defining "Small Scale Solar"

In practical terms, imagine powering a van or tiny home, having an off grid capability that is considered minimalist, BUT also – as self-sustaining as is practical, year round, using solar power as one piece of many to meet that end.

A simple multi-system approach of a base system that will power a minimal set of “just the essentials”, and small peripheral systems for specialized power use. The base system is only for items powered all day or a big part of everyday – mini- refrigerator over warm months, or fossil fuel heater fan during cold months (not both at once), a DC air circulating fan (essential for small spaces), perhaps including minimal use LED lighting (primary lighting being powered by separate sources, such as replaceable batteries), and maybe charging a couple of small devices once overnight (phone, small tablet).

This is needed through all four seasons, with recommended maximums at 330Ah of power used daily, having a daily battery discharge of no more than 30%, with an average main battery bank space taking up less than 1/2 (.46) cubic foot, and solar panel inputs not exceeding 400W. Cost budgeted to no more than $750 on main components (maximum pricing sample - batteries $280, solar panels $330, charge controller $125)

If your power use, space available, and budget falls below the above parameters, this Lean framework of thinking may help you design a more optimized system compared to generic system recommendations. Something smaller and more cost efficient than a cookie cutter approach to solar power systems. (Note: cost efficient and cheap are not the same things). At the least, a “data driven” knowledge base of Lean, leads to reduced trial and error costs in designing or modifying solar systems as it applies to small scale applications, and leads to more informed system module selections, as well as refined system performance expectations.

It’s also good to understand the risks in designing any solar system. A few of the risks could be the design itself which can easily be outdated with new technology or revised best practice techniques. Information based on layman’s knowledge could omit key factors that professionals in the field have insight to. Power consumption estimates can easily change fast, based on unforeseeable events.

The Sample Area: Nations Geographic Center

Since we need to baseline the data from somewhere, the data chosen for this blog is based on is in reference to what is considered the nations geographic center, Lebanon KS. Much of it comes from publicly available information offered by the National Renewable Energy Laboratory (NREL).

The areas solar efficiency in January and December is about 40ish percent of what is received from the sun in July.

The Horizon: How Sun Power Looks through all seasons

Too often, I see solar system designs displaying their performance in the year’s peak solar periods. If truth were known, many of these designs would fail to provide power completely during Late-Fall - Winter months.

This snapshot above depicts the start of each season showing the collected Watts of a 100W solar panel (left scale) and the Solar Hours per day (right scale). Again, we see a 40% (or more) reduction of solar availability in the cold months.

The below illustration is a very important one. It depicts how solar energy is used over a day, and over all four seasons. You can clearly see a comparison of the Summer and Winter solar window, how it affects charging time, and – how solar energy systems can overproduce in the peak sun seasons.

Overproduction of solar isn’t a concern in residential/commercial systems. They funnel this excess power to the grid and receive energy credit on their grid electric bill. Mobile solar users not concerned with space or cost aren’t concerned about solar overproduction either.

For a mobile user whose goal is to create a small optimized modest system, if solar overproduction is excessive and not somehow used in real time, it costs too much in money, space, and time to be practical. It's money overspent on components, it’s space lost for the extra size of those components, and it eats more time to bring your storage system (batteries) to a full charge. Many mid-range to large mobile solar users justify the energy overage as a hedge against a stretch of bad solar weather days. But, that’s only rational to those that have extra money, space and time.

In the Lean framework of thinking, it’s good to ask questions. Here, we want to know how much this excess energy actually is. The questions help us right-size our custom design. The numbers tell us in a modest solar system setup; it is a range between 20%-100% of the battery storage size, with 60% being the average. During peak solar, of a 10 hour sun day, overproduction can be six of those hours (60%).

In a generic (non-modest) system, overproduction can easily be over 150% of battery capacity. That’s one and a half times over what your battery needs on a good solar day! Lean principals paint that amount of overage as waste. Especially in light that the extra components return very little power on bad weather days. Less than 20% of a solar panels max output. A bad solar day is a bad solar day, no matter how much a person has over-invested into a system.

The Instagram: Illustrating simply how solar systems work

Imagine sun power as water flow. The solar panel collects it, a controller funnels it, and your storage system (battery) both stores and disperses it as needed. But the battery bucket only holds so much. As the solar input keeps coming after the battery is full, the overflow then must be used on the fly or wasted. As we’ve seen in the earlier paragraph, this overflow can amount to quite a bit of power. So, in Lean framed small solar system design, a consideration is minimizing this waste.



Lean methodology follows this five step process:

What matters most is identifying value. Lean defines value as simply thiswhat you or I are willing to pay for. Just as important is knowing what, about a Small Systems Solar plan, we are not willing to pay for. When you visualize both, you have a great start in understanding how a Lean framework of thinking can help design a custom system optimized for an individual’s needs.

Below, we identify and map “value added”, and “non-value added” pieces of a Small Systems Solar plan:

For the most part, this looks like most solar designs. The exceptions are that it includes 1) overproduction and 2) excessive time to charge, as non-value added criteria

Creating Flow could be seen as exceptions to generic solar design that open the possibility of creating alternatives to the "one big system" mentality with having multiple smaller systems. So is a system that could scale according to seasonal sun power availability.

Establishing Pull could be reinterpreted as “focusing on now”. Only planning your system for known power needs today, and not worrying about having more down the road for imaginary future power demands. In other words, plan only for what you know you’ll need today. If that changes, like say you buy a drone a year from now, you can create a separate solar charging system just for the drone. If you don’t get a drone, you haven’t over-sized your base system today based on a “maybe”. (Another term associated with Pull, is “Just In Time”.)

Seeking Perfection is an easy and obvious one. It simply means designing a Small Systems Solar solution isn’t a once and done thing. Continually improving on both the system itself, and maybe much more importantly - the way you use it, should always be in the back of your mind.

The Real: Let’s water-down a few present day assumptions

 To embellish the parts of Flow and Pull, allow me to offer some examples in a fun way that brainstorm ways to add value, or reduce waste. I’ll do this with {drumroll} …

Solar Reality Theories:

This segment title "Solar Reality Theories" is meant to be a mildly comical contradiction. It's my attempt to come up with something other than "thinking out of the box", which has become so overused, it's a modern day cliché.

It does though, aptly describe trying to wrap your head around solar, because in so many ways, what works for one person, may not be a best solution for anyone else.  One person’s reality then, can truthfully incorporate theoretical dilemma for someone else’s individual solar design scenario. Especially so when a minimalist system is the goal.

So let’s break out ideas that are departures from conventional thinking, and challenge the status quo! Your rebel side may find this an eyebrow raiser.

A Myth?: Designing a solar system uses one or a chained bank of solar panels, and one or a chained bank of storage batteries.

The Reality Theory: In small minimalist systems, I think I'd be better served using multiple solutions, as opposed to a single big system that serves power for everything. I envision a smallish base system to serve devices or appliances that run around the clock or at least a big part of everyday. Then use peripheral systems for powering everything else. Envision a solar panel and battery to run a mini fridge and/or a diesel heater fan-controller and roof vent. Then off to the side, a smallish solar panel/battery system to power the PC. Perhaps another small system dedicated to charge the cameras and drones in your life. Imagine a bad weather day that calls off picture taking or drone flying - add that solar panel to the base system for the extra input it will need. What if you’re doing extra-long drone flights one day? Well, since you can’t use your computer and fly at the same time, that gives you the opportunity to double up solar panels for drone charging. If one system goes down, it’s not all or nothing in having usable power. Multiple systems can all charge during the peak solar window of the day, greatly reducing the charge time one large system would need. Your small peripheral systems can go with you when you are away from the main system. You wait less, you waste less time, and you have flexibility and options that one large system can't provide. The risks of a single system are mitigated. Basing my needs on multiple systems may add some cost to having power for everything, but if one system goes down, I'm not dead in the water on everything. If I want to be as self-reliant on power as is practically possible, the added cost of having backups and scalability is a value-added cost in my book.

A Myth?: Solar systems aren’t scalable to seasonal sun variations.

The Reality Theory: No, one big solar system design to power everything isn't. But, as brought out in the earlier topic, scalability is possible with a multiple system approach. I'll just add here, that not only scaling up is a consideration. So is scaling down. Imagine a main base system not getting enough sun for a full battery charge in mid-Winter. Would it be better to partially charge your battery bank for long periods, and risk sulfating your batteries to an early death, or, simply designing your base battery bank with two or more smaller batteries, so you can disconnect one, and keep the one battery brought to full charge? (You’d need to rotate them both frequently, and you will need to compensate your power use for having only half the power available, using one battery only until the sun comes back out)

A Myth?: There is no such thing as too little in solar panel capacity

Or, you can never have too much in solar panels

The Reality Theory: There is a point at which, if I generate more power than I use, it is wasteful of my money spent, the space I need for it and the time to fully charge it. Also, there’s going to be a point in every system where the battery discharge is not practically recoverable by solar alone. My thinking of practically recoverable is the longest time I'd care to wait, to get back to having a full charge, while charging the battery at its optimum charge rate.  I don’t like waiting, and waiting can be wasteful. (My personal goal is to have a full battery charge within one day). Fast charging with too much solar input is battery damaging. (The excessive heat generated).Within that framework of thought, an alternate/backup charging method trumps installing more solar panels than I use on average. Or, in other words, buying more solar panels than I would normally need isn’t something I see as a good hedge against overcast skies ... so what if I need to plug into the grid somewhere for a day, or power up a generator on rare occasion, or change my plans to get me on the road charging with an alternator sooner than originally anticipated. I am more flexible than my budget and space. I can deal with it, without the overboard solar panel install.

So, there you have a three-some sample of thinking differently from the masses (in the context of Flow and Pull) about solar design to create something custom to your needs. Copy-catting someone else’s design for yourself will likely work, but you may find yourself working around the system , rather than having a system that OPTIMALLY works FOR you, and WITH you.

Core Values: Defining Waste In A Small Scale Core (Main) System

The core values in a Lean inspired Small Systems Solar design are simple. They are to reduce waste, and put the focus on value added things. Value added things are optimizing cost, time, and space. And you’ll be glad to know, that the Lean tool bag also identifies these 8 waste fighters.

Here are the 8 with a few samples of how they might apply to a Small systems Solar design:

1) Transportation

Not utilizing alternator charging while driving {Lost opportunity}

Roof mounted panel aerodynamics {Taking a fuel economy hit}

2) Inventory

Components that are not right-sized {Over/Under process potential}

Components of poor quality (i.e.: low efficiency panels)              Component under-performance

3) Motion

Portable solar system setup daily setup {Cost in time/effort}

Not easily accessible system monitoring {Cost in time/effort}

4) Waiting

Prolonged "Time To Charge" {Cost in time}

5) Overproduction

Not capturing excess solar after batteries have charged {Lost opportunity}

Having more battery capacity than can be charged within one day's solar window {early battery failure}

6) Over processing

Unnecessary converter conversions {Cost of wasted power}

Poorly designed wire runs (inefficient gage or length) {Cost of wasted power}

Use of AC devices in place of comparable DC devices {Cost of wasted power}

7) Defects

Sunlight or ground cover obstructions (Shadows, Dirt) {Cost of wasted power}

Single power source system reliability (all or nothing approach, no backup plan)     {Catastrophic system failure}

System design inflexible to variable environmental parameters (i.e.: reducing battery bank size in bad weather / adding solar panels from peripheral systems in winter to maintain full charge capability)       {Lost potential or early battery failure}

Not factoring co-dependencies: {Over/Under process potential}

Co-dependencies are:

  • Food Supply
  • Black/Grey water disposal
  • Grid power availability
  • Water supply
  • Fuel supply
  • Trash accumulation
  • 8) Unused Skills

8) Having a Once & Done approach vs Continuous Improvement (always tweaking)

Of these, I’ll make an added note on factoring co-dependencies. This is a great example of using Flow and Pull. This is thinking of a Small Systems Solar design as a part of a greater whole, so everything flows like it’s dancing, and the timing of everything is like clockwork. It makes no sense to design a system to serve your power needs from solar alone for 4 days bad weather, if you only store 3 days’ worth of food, or need to dump waste tanks every 2 days.



Co-dependencies aside for now (only you know what your are) …

The Keys: solar system metrics

The key measures are:

First and foremost – the amount of power you know your 24 hour devices/appliances will use. Like a mini-fridge, heater fan, and roof vent. The idea is to size your main system just for the basics (later creating separate peripheral solar for other things, like a laptop, camera gear, etc.). There are numerous methods of calculating your power needs online. They’ll ask you to estimate how long you will use devices, or take device power estimates off of the device tags. Estimating time is guesswork, and those device tags are often inaccurate. A better method is simply recording actual use. Record at least a week of days, and use that to tell what is really happening in power consumption. No guesswork there. (watts or amps).

The other key metrics are the battery rating at 20 hours (C20), estimated solar input, charge time, battery size, battery life, and maximum overcharge. Here’s a quick look at how these main measures could inter-relate with one another. An increase or decrease in one area has a ripple effect on other areas:

Finding Your Path: Determining what You need from Your Main System

You factor in for yourself, the co-dependencies, and what amount of power you’ll consume.

The table below will help you with a starting place for which battery and solar panel combinations, based on your power use or battery discharge preference. It also will guide you to a solution that will make the least amount of over production of solar that meets your needs. The table was created incorporating real data downloaded from NREL, for our sample site of Lebanon, KS.

The first four columns describe battery size. The % column is the % of battery power used. The Wh and Ah columns are the daily power you use and your main guide to other fields in the table. The Solar Panel column is the panel rated output, the last two columns are Max and Min of power overproduction.

Let’s do a sample.

Let’s put daily power use at 228Wh, and also include 233Wh as the next higher number, in columns Wh or Ah. You’ll be looking at these choices:

Next, look at how much that power use will deplete the battery in the % column. Say you prefer not to use over 40% of battery charge and you do have room for a Group 27 size battery. You’ll then be using 20% of the battery capacity. Let’s assume you will not use any extra power over production, so find the lowest Max number. It is 25%. On the same row, you will see 250W of solar panel will do the trick.

In summary, you have a 95Ah battery of which you’ll only draw down 20% every day, a 250W solar panel putting in 13.75 amps, and your only overproducing 25% of battery capacity during the peak solar months. (This is a pretty big difference in cost, space, and charge time, from the most suggested solar setup – two 6 volt batteries at 220Ah, and 300W of solar, likely overproducing in the Summer like crazy).

As an option you could get close to the same results with three U1 batteries, which then offer an option of disconnecting one of those two during a really bad stretch of weather. It’s better to have two fully charged batteries, than three U1 that are meagerly charged.

So, that’s how you may determine a baseline solution that is worth exploring further for designing a Small Systems Solar plan for your needs. These table recommendations will charge your system in good weather all year long, and on bad solar days, you can use alternate power charging from an alternator, generator, or grid power. Your system is sized to work for you all year long, without waste in cost, space, or charge time. (all these recommendations will charge a battery to full on a good day in Winter, or at least enough to fully recover within a second day.)

And your other power needs aside from your 24 hour base power users, can have a system of their own – which gives you flexibility and options on how you use your system as a whole, while reducing risk should any one of them fail.

I hope this brief example of applying a Lean framework of thinking to creating a Small systems Solar Design has been a benefit on your journey to simplify and optimize solar or numerous other things as well.

(A note on this chart, since two Group 31 or two 6v Golf Cart batteries are common in generic systems, they are included here only for comparison.)

Following is a link to a downloadable spreadsheet file:


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