My grid-tied solar power system and back up

My solar power system is grid intertied.  This means that I have no battery backup and the solar inverters shut down to prevent back feeding power into the grid in an outage.  This could harm line workers as they restore power and is a federally mandated safety system built into all grid connected solar equipment.

So I have 2 meters.  One that records incoming energy from the utility (the use meter), and the other records surplus energy that I export to the grid (generation).  My solar power offsets my usage, and in the summer and fall I generate more than I use so the utility credits me for the power I put into the grid.  The credits accumulate and I use them up in the late fall to cover a month or 2 of bills.

A lot of people assume that because I have solar I have power during an outage.  I don't.  I had 2 options when I built my system in 2009 - battery backup or an automatic standby generator.  The cost and maintenance of a battery bank would be prohibitive and it would not work well with the micro-inverters that I used.  Back then the only option was lead-acid batteries that were either flooded (filled with liquid acid) that require constant maintenance, or more expensive sealed batteries know as AGM (absorbed glass mat) batteries.  Nowadays lithium batteries are more common - like the Tesla Powerwall.  But that is also pricey and does not provide as much storage as I would like.

So I elected to install a Generac Guardian automatic backup generator powered by propane.  This unit starts within 15 seconds of an outage and is pretty reliable, as long as I do basic maintenance.  I already had a propane backup boiler for my solar heating system, so I had a propane storage tank right near my utility room.  I got mine from Home Depot for $2500 and installed it myself.  It cost less than half the cost of a modest battery bank that would be sufficient for my needs.  With a full tank (actually 2 tanks) of propane I can run for over 2 weeks on the generator and often need it for days at a time when we get big winter storms.  The generator does not power everything on my property, just the essential loads, so it can't charge my electric car and I can't run my table saw or wood lathe - both are big 240V machines!

 

I installed an hour meter for my generator in a box with 2 lights that indicate where my power is coming from and use this to record how long each outage is.

This last winter was brutal with 11 outages ranging from an hour to over 2 days.  We had a lot of hard wind storms with gusts topping out at over 45MPH as recorded on my weather station.  Yesterday (May 9, 2020) was a typical windy day that knocked power out for 10.5 hours.  You can see that the wind gusts went off the chart at 50MPH!  You can see where the power dropped out where the blue line goes flat at around 7:30pm.

 Click on the image to see my live weather station.

Here's a list showing generator run times per outage we had over the winter and spring:

 

So clearly it's a Faustian bargain for me.  Most of the time I'm using free and clean energy from the sun to power my home, workshop and Chevy Volt.  But then I have to deal with dirty, expensive propane when the utility power drops out.  I still think it's more cost effective than batteries.  But someday I'd love to install more solar and battery power to go fully off the grid.

 

UV Germicidal Sanitizing lamps and scams - the science and technology

UVC Germicidal Lamps - a tutorial

During the Covid-19 pandemic a large number of sellers on the internet are touting "UV Germicidal Sanitizing" lamp products.  Most of them are fake and do not produce useful UV light.  In the first week of May 2020 I noticed that Amazon has clamped down on these scam products and removed them, but they remain widely available on eBay and other sites.

So I though I would offer some guidance on how to distinguish real from fake products.  I'll start with the science behind UV, then talk about technologies that produce UV (ultraviolet) light and finally talk about what types of products are real, practical and usable.  Be advised that genuine germicidal UV lights produce dangerous light that can harm your eyes, burn your skin and product harmful amounts of ozone (O3).

ULTRAVIOLET LIGHT
UV light is broken into 3 categories, so first lets put it into context.

UV light is beyond the human visible spectrum - although parts are visible.  For instance long wave "black lights" are used to light posters and fluorescent minerals are UVA and are perceived as deep purple.  UVB light is used in bug lights and is seen as a pale lilac/white color.  These 2 types are commonly available in small fluorescent tubes and do not produce harmful UV although prolonged exposure to UVB (like those use in tanning parlors) can give you sunburn.  UVA penetrates glass and clear plastic while B and C do not.

UVC however is much more hazardous, but fortunately the ozone layer in our atmosphere blocks most of it.  It is UVC that has the germicidal and sterilizing properties.  This wavelength from 100 nanometers (nm) to 280nm breaks the molecular bonds in DNA preventing viruses and microorganisms from replicating.  UVC is harmful to humans and can give you skin burns quite quickly and if you look at this type of light your eyes can be harmed.  Welding arcs produce UV that welders sometimes see without safety goggles and the result is known as "arc burn".  Basically your eyes will feel like there is sand in them for hours and it can be quite painful.

UVC produces what is called ionizing radiation that directly disrupts the molecular bonds of oxygen (O2) and the free molecules join up to create ozone (O3 or 3 oxygen atoms) in the surrounding air.  Ozone is that "fresh air" smell you get from lightning in a thunder storm.  The lightning itself produces a lot of ozone.  In moderate amounts ozone is not bad for you, but too much will harm or inflame your lungs.

UV LIGHT TECHNOLOGY
There are basically 2 ways to produce UV light, gas discharge tubes (like fluorescent tubes) - and LEDs (Light Emitting Diodes).  Here's a typical UVC tube:

It is made from quartz glass and filled with a low pressure gas such as argon and a tiny amount of mercury.  It is the incandescent mercury vapor that produces the UVC light when high voltage is applied to the tube.  This image represents what you see - a pale light blue glow. The glass must be quartz because regular glass or plastic will block up to 90% of UV light.  

The other way to make UV light is with LEDs these are solid state devices that can produce UVA (black light) and UVC.  Black light LEDs are used in discos and you see CSI techs on TV waving them around to detect blood etc.  But UVC LEDs are very expensive to make.  They typically cost from $3 to $150 each!  Here's what they look like:

This component is about 1/4" (5mm) square.  They are made from metal or ceramic with a quartz glass window.  They are quite efficient electrically so some battery powered UVC products are available that use these LEDs.  But here is where the scam comes in.  There are also a lot of LEDs that create light that has a strong white/blue cast that looks like UV but isn't.  Those parts look like this:

As you can see this is made from white plastic which - if it did produce UVC - would degrade quickly.  Not to mention that the plastic window would block most of the UVC light.

REAL vs FAKE GERMICIDAL LAMPS

Lets start with the fake products.  Here are some pictures of various ones that I found on the web:

As you can see these are constructed with dozens of white plastic LEDs that cannot be UVC emitting devices.  Some do emit UVA "black light" however. One give-away is that these products retail for under $50.  If they used genuine UVC emitting LEDs they would cost HUNDREDS of dollars!

And there are small battery powered "UV sanitizing" wands too:

In these pictures they have colored the image to make it look like the light is purple when in fact it looks white with a blue cast.  (Although some may be using inexpensive "black light" purple LEDs that produce UVA light).  Many of these fake products will lure you in with the bold keywords of: "Germicidal", "Sanitizing", and most egregious: "UVC".  They are flat out lying!  While there may be one or two products that do use genuine UVC LEDs, I would generally advise against risking a purchase unless they sell for well over $100.  But the best option is to get the real deal which are actually quite affordable.

GENUINE GERMICIDAL LAMPS
Products that do produce UVC will look like this:

The one on the right correctly states "with ozone".   These lamps do not produce dangerous amounts of ozone unless used in a small space. There are also portable UVC sterilizing wands like these:

If you look closely, you can see the quartz glass tube inside - as opposed to the LED dots in the wands above.  These units are fine for sterilizing small items like breathing masks or light switches, and can accomplish good results if used for several minutes.

Larger, more powerful tubes are wall powered and are more effective and do produce the distinct odor of ozone when operating.  Here's a good example of an 11 Watt lamp:

This type of lamp is encased in a quartz glass tube and can be rated up to 30 Watts.  Some however use a regular glass tube that blocks the ionizing radiation that produces ozone.  Some some will feature "ionizing" and some will say "non-ionizing" if they are ethical.

Hospitals use much larger UVC lamps in operating rooms and to sterilize patient rooms and they need to air out the room to remove excess ozone before it can be used after being sterilized.

There are no clear-cut guidelines for use of UVC lights but generally speaking using small (under 20W) units for several minutes to sterilize small items should work.  If you want to sterilize a room of more than 100 square feet you would need a big lamp rated at over 30 Watts and leave it on in the the room for over an hour.

This article from NPR suggests that there really is no clear "dosage" or exposure duration.  And small lamps will not illuminate every part of an object of room

Some lamps come with timers that allow you to walk away and let them work unattended.  Some even have a start button you press, and there will be a delay before they come on so you can leave the area before it lights.  All these lamps advise that the room needs to be aired out after use to reduce exposure to unhealthy levels of ozone.

UVC HAZARDS
Be advised that UVC sterilizing lamps are dangerous and should not be left in the hands of the inexperienced or children.  If you are sterilizing a room it should be closed and locked and then aired out afterward.  NEVER look directly at these lamps with the naked eye!  The lenses in most prescription glasses do block UVC but don't trust that as a safe practice.  Never expose your skin for more than a few seconds!  Keep in mind the inverse square law that states that as your distance doubles the amount of light diminishes dramatically, so touching or looking at these lamps up close is dangerous, but is somewhat safer as you get farther from it.


If you want to shop for these lamps, try this link to get started - and just ignore anything that looks like it uses LEDs.  As of this writing (May 10, 2020) they are hard to get from US suppliers.  But Chinese suppliers will ship them by air post to arrive in 4 to 6 weeks.

I hope this is helpful and useful for those of you who may be considering the purchase of a sterilizing light.  Please leave comments if you have questions, corrections or experiences to share.

Another M190 Microinverter failure

I was an early adopter of the first M190 microinverters made by Enphase back in 2009.  They came with a 15 year warranty that is running out in 4 years and I'm getting anxious.  These first generation units are beginning to fail often - the 8th one to fail was this week.  This is out of a total of 29 devices of that generation.  I have installed some newer ones since, and replaced the failed ones with the newer models under warranty.  Fortunately they make it easy as an installer to order a replacement via their web portal.

Latest failed microinverter as of 3/2020

This one is on the top row, so my friend and I can access it from the roof ridge and from a ladder.  It takes us less than an hour once I get the replacement part, but it's a chore that is getting old.   The price I am paying for being an enthusiastic early adopter!

8 failures so far

 For more info about my solar installation - see my very detailed blog:
http://www.arttec.net/SolarPower/index.htm

Electric room heater failed - not repairable

This afternoon I went to turn on the electric heater I use for supplemental heat in my office when it gets really cold outside.  It didn't come on and beeped sadly and the display did not light.  I really liked this heater because it had a digital thermostat that I could set, and also a timer so it would shut off after a preset number of hours.  So I tore it apart and spend 1/2 hour testing the electronics.  I could not find the failure even though it was all quite well designed.  (As a product designer, I should know!).  So sadly I had to trash it.  I just saved a few components that I could use.

The new Lasko ceramic heater I got came packed in sustainable/recyclable materials which is a plus.  (Click here to buy one - as an Amazon Associate I earn from qualifying purchases.)  Also it is very quiet so I may move it to my bedroom where I can control it from my Nest thermostat, replacing a noisier heater.  (See the post about how I built an interface to control a room heater for my Nest here.)

I hate disposing products, but if I can't fix it - nobody can!

Filling the solar collectors for my workshop solar heating system

 

 

 NOTE! I removed this system and replaced the collectors with 6 320W solar panels that will offset the 2 heat pumps I installed myself.  See this post

 

Every fall as the temperatures start dropping down to freezing I fill the collectors for my solar heating system with antifreeze solution, and in the spring I drain them.  I don't need the heat in the spring and summer.  If the antifreeze fluid gets too hot it will cause an over pressure in the collectors and also the fluid will turn acidic and begin to corrode the copper plumbing.

I mix a 50% solution of antifreeze and water and pump it from a 5 gallon bucket into the collectors and then run the pump long enough to purge air from the system.  Air bubbles can stall the pump and that is a big problem that can cause over heating.

Each year I note when I fill and drain the system on the wall of my 80 gallon storage tank (which is a regular water heater used just as a holding tank for solar heated water).  And yes we have a 7 to 8 month heating season in Maine!

Today it is cloudy and I don't expect any sun.  My system controller (that I manufacture - click here to learn more) shows 83F at the collectors and 121F at the top of the tank.  The tank temperature is high due to the propane backup that maintains the tank at 110 to 120F.  The collectors can heat the tank up to well over 180F on a good day and that is the free solar heat that I use to warm my workshop and office.

You can see a detailed blog about the design and construction of my solar heating system here. 

Here's a system diagram - click here or on the image to see live performance data.

Failing 1st generation microinverters

10 years ago when I began installing my solar power system, I was one of the first to use the new technology of microinverters made by Enphase.  (Details of my installation here).  These are small devices that convert DC solar power to 240VAC in a small box mounted behind each panel.  Original model shown above, and new one shown below.

I was a very early adopter, mine was the 1239th system commissioned back in 2009.  Now there are millions of systems, and they are up to 6th generation technology. The devices come with a 15 year warranty and I'm at the 10 year mark and have just replaced the 7th failed unit out of a total of 32.  I am able to see which ones failed from the web interface that reports performance in near real time.

It is a chore to climb up on the roof with a friend and 2 long ladders.  We have to remove the 30lb solar panel, set it aside, remove the failed microinverter and replace it, then replace the solar panel.  It takes up to an hour to do this safely and carefully.

What I really like about this system is the granularity.  I can see the performance of the system on a per-panel basis and failures are easy to spot.  And I can scroll through the recent day or week to see how the system is performing.  Below is overall power for the last week with peaks at around 4kW.

I'm hoping that Enphase will continue to replace them if units fail after the 15 year warranty.  Despite these setbacks, the system is performing very well and I am powering my home, workshop and Chevy Volt for free for up to 7 months of the year.

The pattern of failures is interesting, they seem to propagate over time:

Cordless yard tools

Someone who does not know me well asked me by email if I could repair the engine in her weed wacker.  I bit my tongue and politely replied that I don't use gasoline powered yard tools and would not choose to repair one even if I could.  I urged her to see this as an opportunity to go cordless and reduce pollution and emissions.  

The EPA says that: "A conventional lawn mower pollutes as much in an hour as 40 late model cars for an hour."  Plus I don't like the stink of gasoline or the awful noise.  Cordless yard tools are now in their prime and very affordable.  You can buy them at almost any hardware store.

Shown above are my Black & Decker 20 Volt cordless hedge trimmer, weed wacker and my home made monster lawn mower.  The hedge trimmer I refer to as a "Light Saber" - I can just wave it near anything less than 1/4" and it cuts right through without slowing down a bit and can chew through up to 1/2" branches.  The weed wacker is also very powerful.  Both tools last over 20 minutes on a charge which is plenty for home use.

Back in 2005 when I built my cordless lawn mower, there weren't many options for cordless lawn mowers, but they are common now thanks to advancing lithium battery technology that has driven the costs down dramatically. 

If you are a curious/nerdy person, you can read about my electric lawn mower construction in my detailed blog: http://www.arttec.net/Solar_Mower/index.html  It was featured in Popular Science Magazine in July 2008 and I inspired several people to do similar conversions of lawn mowers.  Mine is very powerful and can charge through tall grass with impunity!  It has a 22" cutting path while cordless models range from 14" to 21".
 
Popular Mechanics recently reviewed 6 best cordless lawn mowers for around $500.  Read the full review here.  Or this excerpt:
 "The benefits of a battery mower are obvious from the moment you engage the operator lever: They’re incredibly quiet. Gas-engine mowers succeed because they produce so much power that they can afford to waste most of their output as noise, heat, and friction. With battery mowers, that output occurs at the power plant, not in your yard. These mowers are also mechanically simple. There’s no electric start or recoil start, either—just push a button to power it up. Like any electric machine, basically it’s on or its off. There’s no engine oil, spark plug or air filter to change. Keep the battery charged and sharpen the blade. That’s all there is to it. As with cordless power tools, you charge a battery separately from the tool or machine, which allows you to simply swap out the battery when it’s dead and to keep on working."

Water heater maintenence - drain bottom and check anode rod

There are 2 things you can do to extend the life of your basic tank style water heater.  One is to periodically connect a hose to the drain valve and flush out the sediment at the bottom of the tank for a few minutes - or 4 to 5 gallons.  This prevents the sediment from building up and potentially damaging the heating elements or blocking the drain valve.  Here's a video that explains exactly what to do.  https://youtu.be/TCFCwldQHAs

The other thing is to check the anode rod.  This is a sacrificial magnesium electrode inside the tank that slowly dissolves to prevent the tank lining from rusting.  It looks like a long metal rod made of aluminum or magnesium.  Replacements cost from $17 to $45 depending on type and size.  Here's a link to get one from Amazon (as an Amazon Affiliate, I earn from qualifying purchases.)   I check my rod every year.  This process will likely require 2 strong people and a 1/2" ratchet wrench with a 1 1/16" socket.  Here's a video on how do do this: https://youtu.be/wzecqGyCllU

I used a long piece of pipe over the end of my ratchet wrench to get enough leverage to break it loose.  

Here's what my rod looks like after 2 years:

I took it outside to hose off the gunk before I replaced it.  I think it is good for another year or two, but I will check it every year. These simple maintenance chores can more than double the life of your water heater and save you a lot of money!  And from a sustainability perspective you are keeping the water heater out of the landfill.  If everyone did this there would be a lot less old tanks being disposed of.

 

Update: November 2023

Today - 4 years later I checked the rod and found that it had  rusted through to the steel which is very concerning since the tank can start rusting out at this point.  Shown below is the old and new flexible rod which is easier to install in a low ceiling basement:

 

 

Basement Watchdog water leak alarm

If your tank springs a leak - you need to know about it right away!  After my first tank failure I installed this Basement Watchdog in the drip pan under the heater.  (You DO have a drip pan right!?).  If the electrodes get wet a LOUD alarm goes off.

I got this one on Amazon, here's a link. (As an Amazon Affiliate, I earn from qualifying purchases.)

I installed the alarm on the wall outside the utility closet, and the sensing electrode in the drip pan:

Alarm on the wall

View of the electrodes

View of electrodes in place

 

Solar fountain

 

I had been considering putting out a bird bath for a while when I came across this solar fountain on Amazon for under $20.  (Click here to purchase on Amazon - As an Amazon Associate I earn from qualifying purchases.)  It was irresistible!  A fountain water feature for my lawn and it runs on it's own solar panels!  I got a plant tub and filled it with water from my rain barrel - and top it up every few days.  The sound of water tinkling is delightful.

I installed toothpicks into the foam edge to keep the fountain centered so the water does not get thrown over the edge.

It comes with different nozzles for various spray shapes and just floats perfectly on the water.  When there is little sun due to clouds or time of day, it pulses in little squirts, but in full sun the fountain goes up over 12".