Showing posts with label chargers. Show all posts
Showing posts with label chargers. Show all posts

Wednesday, 16 October 2019

Responding to Collapse, Part 13: Keeping the Lights on When the Grid Goes Down Forever

I'm doing something new this time, which is to publish a post that is almost entirely the work on one of my regular readers and commenters, Joe Clarkson, who lives off-grid on the Big Island of Hawaii. My knowledge of solar electric systems is entirely theoretical and I have always found that in the process of actually building something like this, one learns a great deal that isn't covered in the books. So I am pleased to present this material from someone who can speak with a much greater degree of practical experience than me.

I do have a few comments to make, but I'll save those for the end of the post.


Keeping the Lights on When the Grid Goes Down Forever

by Joe Clarkson

As someone who has lived most of my adult life in an off-grid home, I have had a lot of experience in managing the equipment needed to replicate the round-the-clock availability of electricity provided by the grid. That experience has been marked by a few failures but over the long haul our electrical supply has been more reliable than most utilities. That there is far more support available now than there was when I was setting up my first off-grid system back in 1975 (small hydro/diesel) makes living off-grid even easier. And since the rural neighborhood surrounding my home has homes that are all off-grid, I rarely hear the questions that many people asked me in years past, “Why do you live off the grid?” and What’s it like?”

The first question I answered by explaining that land without public utilities, like power and water, is almost always far less expensive than land with them. This is true, but I almost never went on to explain that I didn’t like the feeling of insecurity that came with being dependent on the grid. I have long felt that the grid is vulnerable to any number of disruptions, some of them likely to be permanent, and I wanted to live in a situation where I had more control over my electrical supply. Most people still think that attitude must also come with wearing a tin-foil hat.

The answer to the second question was that living off the grid was mostly like living on it. This is even more true now that solar panels have gotten so inexpensive that it is easy to have an ample supply of electricity. My current house is a sort of “legacy” off-grid home. It started out in 1986 with very little solar capacity (under 800 W), so everything was geared to minimizing the use of electricity. Thirty years ago, our electrical consumption was about 2 kWh per day at most. Now that I have 4 kW of solar PV capacity, we have become more profligate, even with the kids gone, and we use 4-5 kWh per day. A solar installer recently told me that he typically designs off-grid homes for a capacity of 20 kWh per day, just as much as the typical grid-connected home around here uses.

I have lived without electricity during two years serving in the Peace Corps and found it easy to do, albeit on a tropical atoll. This experience gave me a deeper understanding of the place electricity has in the modern world. I won’t be discussing that place here, although that is something that everyone should consider thoroughly before making plans for adapting to collapse. Instead, I will describe my way of replicating a modern household electrical system without the grid and my preparations for keeping it going as long as I can.

I know that if the grid goes down forever and business-as-usual becomes ever-accelerating collapse, it will be impossible to maintain an independent electrical system for the long term. But I would like to keep it going as long as possible, if only to ease the transition from a modern, high-energy life to one that will look a lot like life was here in Hawai‘i before contact with outsiders changed everything. These old bones are not ready for a life of subsistence agriculture and hunting-gathering in service to a feudal lord. That life will eventually come, if not for my wife and me, then for our children and their children, but I hope to make the transition as gradual as possible for all of us. If collapse is rapid, it also just might be the difference between life and death.

Our Home Power System Details

So, what kind of system do we have and how do we intend to keep it going during collapse? Our electrical supply is old-school and typical of many off-grid systems:

  • 4 kW of solar supply (Sixteen 250 W modules with an output of 24 V DC nominal but wired in series-parallel to about 140 V).
  • Two 80-amp MPPT solar charge controllers convert the solar output to 24 VDC for the battery.
  • 900 amp-hour lead-acid battery (12 cells at 2V each)
  • 4 kW inverter (2 Outback FX2024 operating in parallel at 120/240 VAC output)
  • 6 kW Northern Lights diesel generator

Inverters with solar charge controllers to the right

One half of 4 kW solar PV array.
The other half is on the roof of another building but looks identical.

Battery box 
(with concrete block to keep a visiting 4-year-old grandchild out), 
6kW genset, diesel supply in 55-gallon drum.

24 V battery
(12 Hawker flooded lead-acid cells, each 900 Ah)

24 VDC water pump inside concrete block enclosure

Solar hot water system with TV and Ham antennas behind.
80-gallon hot water tank is stainless steel.

240 VAC wood splitter runs off the solar electric system.

38,000-gallon water tank.
24 feet in diameter X 12 feet high.
Half the tank is underground.

The average solar incidence here in up-country Hamakua is low, only about 2.5 peak sun-hours per day. But with 4 kW of solar array, this is enough to average about 10 kWh per day, more than twice as much as we actually use. This means that we rarely need to use the back-up diesel to charge the batteries. Our average annual use of the generator is about 30-40 hours a year at a maximum charging rate of 2 kW. My estimate is that we use about 10 gallons of diesel a year in the generator.

The appliances serving the home are pretty typical except for refrigeration and water pumping. We have a washer and propane heated dryer, a propane range, propane back up water heater (rarely used since we also have ample solar water heating) the usual compliment of LED lighting and an assortment of communications and entertainment equipment (flat screen TV, a couple of computers, CD player and receiver), clothes iron, vacuum cleaner, bathroom appliances like hair dryer and toothbrushes, all being used at rates that would be typical in a grid connected house. We do power everything from power bars so that we can turn off equipment completely so as to avoid “ghost loads”.

Our refrigeration and water pumping are DC. This was originally for efficiency and power demand reasons, but over the years we have kept these appliances operating directly off the battery as a precaution against inverter failure. If the inverters fail, we can still have water and keep our refrigerator and freezer powered up. We would need to run the generator in the evenings two to three hours for light and for other electrical appliances, but it would save us from having to run the generator more often to keep the fridge cool and to pump water. Now that DC LED light bulbs are available, we may switch back to DC lighting, which would not be too difficult as the lighting load center is separate from the load center for the outlets (our lighting was originally DC).

Our water system is based on two corrugated steel tanks (including metal roofs) with heavy polyethylene liners. A 40,000-gallon main tank is filled with water from our roof and that water is pumped up to a 2,000-gallon tank about 100 feet higher than the house with a 24 VDC Shurflo pump. The little Shurflo pump only moves a couple of gallons per minute, but we only need to turn it on about once or twice a week for a few hours. (We have another piped water system with non-potable water for agriculture and livestock, but a description of that system is outside the scope of this post).

How much of these systems can we keep operating while adapting to collapse? In a collapse situation propane will be impossible to get. The clothes dryer can be abandoned totally to line drying (what we mostly do now), the back-up water heater can be shut down, and the range can be nursed along for a few months to a few years depending on the state of the 125-gallon propane tank at the time of propane delivery failure. For the longer term we have a wood cooking range on a covered lanai. This range would also be a source of hot water once I get the auxiliary water tank installation off my “to do” list.

So, the long-term energy sources for the house and farm are slated to be solar electricity and wood, with solar hot water for as long as the solar hot water modules last (perhaps 15 to 20 years). We have plenty of wood on the property and even have an electric wood splitter powered from the solar system. The wood range has a probable life measured in decades. We have a wood heater for those cool winter days (low 60s), but how to keep the solar system going?

The short answer for most of the power conversion equipment is to have plenty of spares. The inverters can be completely rebuilt with three circuit boards and a cooling fan for each inverter. Those parts are on the shelf. The inverters have been in continuous operation since 2006, so I expect them to need rebuilding in the next few years. The solar charge controllers have an estimated 15 to 20-year life and they are only about 7 years old, so with a spare for each the charge control system can last another 30-35 years. My current crop of solar panels is only about 5 years old, so they should last for a long time yet and I already have their replacements handy, since I bought another set for a second home that probably won’t get built after all. If we do finally build the second home, it will have a duplicate electrical system that can be intertied with our existing system, thereby increasing redundancy.

Here is a table summarizing the power system and the appliances operating from it:

Item

Estimated Life Span (Years)

Method of Repair

If Failure is Unavoidable

Solar PV modules

25-30

Replace with spares

Remove bad modules, rewire and use less electricity

Charge controllers

15-20

Replace with spares

Reconfigure PV to battery charging voltage and manually switch modules on and off (works only with flooded cell batteries)

Inverters

15-20

Rebuild with spare boards

Use DC appliances only or replace with legacy spare inverter (I have a couple of old Trace 2024 inverters in storage)

Battery

Wide variation

Replace with spares? Pick the battery with the longest possible life?

Use no electric equipment except any that can be operated directly off the solar array (DC motors, heaters)
Diesel generator

30

Have plenty of maintenance spares (belts, filters, etc.)

Greatly reduce electricity consumption in cloudy weather

Water pump

10

Replace with spares or rebuild with still-good parts from failed pumps

Haul water with buckets or install eave-level tank or install catchment roof at upper tank.

Corrugated water tanks

30-50

Reinforce weak areas with cables

Use any available vessel for water storage and hand carry water in buckets

Refrigerator

30

None

Evaporative cooling? Night radiation cooling?

Freezer

30

None

No frozen food

Washer

25

None

Hand wash with plunger. Have manual wringer on hand.

Propane dryer

30

None

Line dry everything all the time

Propane range

40

None

Substitute wood and wood range

Solar hot water modules

20

Substitute modules with spares?

Water heating loop in wood range

Stainless steel solar hot water tank

50

Move to wood range location

Batch heat water on stove

Household wiring

50+

Repair with spares

Live without electricity


Battery Considerations

Without an industrial civilization as backstop, the biggest hurdle to keeping a solar system going is the short life of the battery bank. My batteries have been well maintained, but they were three years old when I purchased them 8 years ago. They are nearing the end of their cycle life.

If it cannot be replaced by going to the nearest battery store, the main attribute a battery will need to have is the ability to operate over a large number of daily charge-discharge cycles. There are numerous comparisons of battery cost and cycle life on line. Most of those comparisons result in lithium-ion batteries being the best choice, especially if cost is not a determining factor, just because of their superior cycle life.

Many lithium-ion batteries are touted as having up to 10,000 cycles, even with 80% daily discharge. That would result in a life expectancy of 27 years even though they are typically guaranteed for only 10 years. Even though the cell chemistry could last as long as 27 years, my worry is that the sophisticated electronics that manage the charging of each cell in a lithium-ion battery will probably have a life expectancy of less than that.

I have not yet decided on a final battery replacement strategy. Here are some pros and cons for the best main choices (excluding price):

  • Lithium ion: proven long cycle life but delicate to charge and requires sophisticated electronic charge management system.
  • Lead-acid: Very forgiving if well maintained but have the shortest cycle life. It may be possible to store “dry charged” cells for many years before putting them in service.
  • Nickel-iron: Reputed to have a very long life and very forgiving of a simple charging system (similar to lead-acid). Very hard to damage except by using poor water for electrolyte replenishment. I am still not certain that the lifespan of this battery matches its reputation. Manufacturer literature suggests a cycle life between that of a good lead-acid battery and a lithium ion battery.

I am leaning toward lithium ion. I need to confirm the life expectancy of the typical battery management system and any needed protection from a solar charge controller failure.

I am also keeping an eye on the market for flow batteries for the home. These are quite new and have a limited track record, but should have very long life with easily replaceable pumps.

I am also tempted to see if I can craft build a pure-lead-plate battery from roofing lead sheet.

Conclusion

This post has covered a lot of expensive equipment, much of which my wife and I have acquired over many years. We feel very fortunate to have been able to do so. When one adds up the cost of a small parcel of decent farmland, a home and the outbuildings and equipment a small farm requires, including the equipment needed to provide electricity, water and heat for the home (including in-ground piping and electrical circuits) and other costs like livestock, fencing, roads, ponds, and land leveling, it becomes obvious that it takes a lot of money to prepare to eventually live without money.

I do know that the one thing that will always have value when adapting to collapse will be the skills it takes to help manage a small off-grid farm. Any person that has the ability to grow and hunt for food, manage livestock, operate energy and water systems and knows which end of a screwdriver to grab, is likely to find a place in a post-industrial-civilization world, even without a lot of money for preparation. I am still learning these skills and I started a long time ago. It’s past time to get started, so I recommend a crash course in practical trade skills to anyone that has few of them. Good luck to us all!


Wind and Hydro Power

Anticipating questions from our readers, I asked Joe about wind and water power. Here is what he had to say, which makes good sense to me. —Irv

I have had a small wind turbine as part of my array of battery charging sources and found it to be more trouble than it was worth. It was a Whisper 1000 and it really needed strong winds to produce much power. It also had a continuing series of mechanical problems, but I kept it going for a couple of years and then threw it away.

I have also had a lot of experience with the larger Bergey 10 kilowatt wind turbine on village power projects. It worked a little better than the Whisper but also required a lot of maintenance. Constant changes of blade leading edge protection tape, furling cable that broke and very high noise levels made it a pain to use. Now that solar modules are so inexpensive, I strongly advise against wind turbines except for large, grid-tied machines for commercial power producers.

Small hydro is another story. If a small stream with a reasonable head is available, small hydro can be a great charging source. I recommend going with a DC alternator to charge batteries and use an inverter for AC power. The small hydro system just substitutes for solar panels as a battery charging source.

If a larger stream is available, enough to generate the maximum power required at the site, then an all AC system can be installed. A load diversion governor is a lot cheaper than a variable geometry turbine. With a load diversion governor, the AC alternator is kept loaded at full output at all times and any unneeded power is electronically shunted to a waste load, typically a water heater element inserted in the penstock or a spa basin.

Small hydro is extremely reliable. The only difficult part is getting clean water into the penstock, which means that a lot of attention has to be paid to the intake structure and subsequent settling and screening equipment. Flood conditions put a great deal of force on the intake, so everything in the stream bed has to be very robust. The best small hydro sources are hillside springs, which avoid a lot of the issues with stream sources. Year around streams and springs are relatively rare, but if you have one they are great sources of energy. With enough head, it takes very little water to produce enough energy to power a homestead.

Irv again, with thanks to Joe. And now, just a few comments from me.

I agree very strongly with what Joe said in his conclusion about learning practical skills. If your work has you sitting in front of a computer pushing little bits of information around on the screen, and what you do for fun in you off hours never sees you touching a tool, it is time to start learning some of the skills that will be needed when BAU(Business as Usual) is no longer functioning.

Now back to the specifics of off-grid power systems:

One important thing to be clear about is that batteries don't like to be "cycled", that is, to be charged and discharged. Joe touched briefly on this, but I think it is important to emphasize.

Every time a battery is discharged and charged back up (cycled), it wears out a little bit and its capacity to store energy is reduced. The backup batteries that I maintained as an electrician in the power system were kept fully charged and only discharged during outages, and even then not too deeply discharged. They usually lasted for about 15 to 20 years.

In an off grid solar electric system, batteries are cycled fairly deeply on a daily basis. Joe estimates his current batteries will have a lifetime of around 11 years, which sounds about right to me.

The temperature where Joe lives ranges from the 50s to the 70s, Fahrenheit. This is, to say the least, less extreme than the temperatures we experience here in Southern Ontario ( -30° F to around 90° F.) And there are many places not that far north of here that get even colder in the winter. Precipitation around here also comes in various nasty forms in a addition to rain. Such as hail, freezing rain, sleet and snow.

This has some negative effects on solar panels, which are inevitably exposed to the weather, causing them to fail sooner. And of course their output is limited when they are covered in ice or snow.

Batteries function best when their temperature is in the 70s Fahrenheit. That means they need to be in a heated space in the winter. Lead acid and nickel iron batteries also need a well ventilated space due to the hydrogen created during charging and discharging. You probably wouldn't want them in your house due to the fire hazard. Lithium batteries don't given off hydrogen and can withstand more charge/discharge cycles, which is a major plus. But they are more expensive and required more complex charging controls.

I would appreciate hearing from any readers who are running solar electric systems with lead acid or nickel iron batteries in climates with cold winters.

I have some experience repairing battery chargers at the component level, but that equipment was built in the 1960s and 70s, used single layer, single sided circuit boards and discreet components rather than integrated circuits. It almost seemed as if it was designed with repair in mind.

Joe tells me that more modern equipment is less maintainable at the component level—about the best you can do is change out a whole board or module.

Acknowledging that, it still seems to me that there are quite a few people around who I would call tinkers, but who are currently referred to as "makers", at least some of whom have the knowledge, skills and equipment to salvage and refurbish/repurpose defective equipment when that becomes the only alternative. I think in some cases they will succeed in getting some extra life, maybe a few more decades, out of systems like Joe's. A way to make storage batteries using salvaged materials and a fairly low level of technology would be very helpful.

Finally, as Joe says, a system like his does not come cheap, and I suspect many of my readers will find themselves lacking the financial resources to set up anything close. And yet I've devoted this whole post to the idea, and I would recommend that those who can afford it should go ahead and set up such a system. Why so?

First of all, electricity is very useful and if you could extend it's availability by a few decades, it would be worth quite a bit to do so. In one's own domestic situation electric lighting, refrigeration and water pumping would be worth a lot, along with communications and entertainment.

Secondly, in the years after the grid finally fails us, I would like to think an attempt will be made to switch over to sustainable, "village level" technology and to utilize local energy sources to generate electricity. This transition would be greatly facilitated by off grid power systems of the type Joe describes.

A closer look at this transition and the positive legacies of the industrial world will be the subject of my next post.


Links to the rest of this series of posts, Preparing for (Responding to) Collapse:

Posted by at 10 comments:
Labels: , , , , , , , , , , ,
Subscribe to: Posts (Atom)