Cold weather in Texas (and other states) - electricity availability and home solar panels

In My Humble Opinion (IMHO)
#41

We put in $60k of solar panels two years ago (tax and utility rebates cut that cost down by half). That functionally makes us neutral. We are in Minnesota, so we get very little output from the solar in the Winter between short days and snow - and there is no way I’m hoeing the snow off $60k of roof mounted panels on a three story house - scratching those panels will degrade the generation. We elected to put in no batteries - any useful batteries for the house would have cost another $10k (this is not a small house and at any given time, there are enough computers running to be a small data center, that would store enough power that if we turned everything off, we’d be able to run the fridge, freezer, lights etc for a day or two - turns out, you can live without power for a day or two) - we may revisit that if our grid gets flaky. Natural gas heat (and dryer and stove).

Now, I don’t think snow would be a long term issue in Texas - a few days of no generation - but those days are going to bring high usage and the Texas problem is the grid failed due to high usage.

#42

California, not Canada. .gov is US only.

#43

Thanks for that. Definitely wasn’t paying rapt attention :wink:

#44

The correct way to install panels is to be 90 degrees to the incoming sun rays. It the Earth didn’t have its 23 degree axial tilt that’d be easy.

On the equator panels would be dead horizontal because the sun would always be straight up. Here in Miami where the latitude is 26 degrees panels would be 26 degrees off horizontal. Up around Boston at latitude 42 degrees they’d be 42 degrees of horizontal, or about halfway between horizontal and vertical. At the Poles the panels would be vertical. In, say, Dallas they’d be 32 degrees off horizontal.

In the real world the Earth’s axial tile means the apparent altitude of the Sun alters +/- 23 degrees from your fixed latitude over the course of year. Because of shorter days in winter, panels are typically installed to be closer to 90 degrees to the weaker, lower angle, and shorter winter sun altitude than to the stronger, higher angle, and longer summer altitude. The net effect is to slope the panels several degrees more steeply than your latitude would suggest.

Bottom line: in serious snow country the panels are steeply sloped & snow can slide off with just a little help. Even in mid-latitude Dallas, there’s enough slope to help.

#45

A battery system tied to solar can allow you to have continuous power during blackout, but the amount of time you can run this way depends on your solar output and the size of your batteries. In the winter, solar production is far lower, your demand for electricity is higher, and snow cover on your array will make your output zero until the snow melts and slides off, or you clear your panels yourself (not recommended). So you only get hours to a few days of power with a Tesla Powerwall or similar system. Such a system can help you avoid utility charges if your state does not have “net metering” for solar.

We have a PV array that supplies 108% of our use. At time of installation in 2013 there weren’t lithium based battery backup systems, so we would have needed to devote space to a bunch of lead acid batteries. Because we had some concern about losing heat due to power outage in the winter, we just purchased a whole-house natural gas generator with a transfer switch. Now if the power goes out, we have 30 seconds or so of no power, then the generator spins up and runs the entire house.

The cost of the backup generator itself is only a fraction (about 1/3 in our case) of the total cost to plumb the gas, install and wire the transfer switch, and install the generator.

PS - we bought the quietest model (Kohler) we could find, but it still isn’t that quiet. Per warranty you have to run it 20 min per week, so that is a small annoyance to us and neighbors. The generator allows you to schedule day/time.

#46

I’m curious what was needed to “plumb the gas” in your case? We’re getting estimates this week to upgrade to a whole house generator, and we’re still deciding how to fuel it. Our neighborhood has no natural gas supplied, so we’re looking at various options for propane or diesel storage. We have the requisite transfer tanks to re-supply a diesel tank, but am trying to determine the overall cost and which would be best.

We had plenty of water/fuel/food/wood stored when the cold weather hit, but found that lugging and setting up our portable* backup generator was much more difficult in snow and ice. We periodically test-run power outage scenarios, but (admittedly) only did so in decent weather. Also we hadn’t planned around multiple failures at once as happened in Texas. We managed the snowpocalypse OK with no damage, but would prefer to make it less stressful in the future.

*As I age, this term is getting redefined.

#47

One time I looked into this and some solutions people have come up with is to run a generator to activate the grid tied inverter of the solar (with the appropriate interlock for line worker safety). The solar can sync to a generator, and this can extend the run time of the generator. However the problem stated with such a setup is what happens if the solar overproduces. It’s not the most stable set up and most likely risking pricy components, but it has been done.

Most likely a better but still DIY cheap way would be to have a small battery backup - perhaps even one deep cycle battery, have the solar panels charge them independently of the grid tied inverter but on a charger that regulated the charge (and won’t allow overcharging). Use those batteries or battery to power another inverter.

Which is somewhat similar to what I used to do during long power outages with a generator, deep cycle battery and a inverter. I would first use the battery/inverter till I needed to recharge that (and everything else like my laptop battery), run the generator to recharge everything a good deal, then shut down the generator and run off battery/inverter. Rinse and repeat. It greatly extended how far I could go on a tank of gas. I did think of hooking up a solar panel to recharge the battery directly however it didn’t seem that cost effective to do so and would only work when the sun was shining. But if the solar was already there, I would have done that.

#48

We had Natural Gas, so they just tapped into the supply line just after the meter and ran pipe outside for a short run along the foundation to the generator location.

#49

A post was split to a new topic: Four directors of ERCOT resigned

#50

I wouldn’t argue with anything you said.

But I did/do think it’s worth pointing out what @jdc said:

In the winter, solar production is far lower, your demand for electricity is higher, and snow cover on your array will make your output zero until the snow melts and slides off, or you clear your panels yourself (not recommended).

[bolding mine]

Which was part of my implication: snow and ice can reduce the output of panels, even perfectly mounted and aligned, and that isn’t always a given either. Roof shape, pitch, orientation of the house, budget, etc., can force mounting that is suboptimal.

So this part of your quoted text:

snow can slide off with just a little help

Is something that people should bear in mind. If the weather is bad enough to degrade the performance of my PV array, I’m probably not going up on my roof, and my wife definitely isn’t letting me* :wink:

Pretty good resource for mounting, angle, and orientation info:

*And the day that changes, I may have bigger problems :wink:

#51

@DavidNRockies
For most people electric demand is highest in the summer.

The part about zero output when snow covered is wrong. I already covered that.

Clearing panels varies by house. On a ranch it is pretty simple. On a 2 story building, I can agree with the not recommended.

Why do you feel the need to repeat incorrect information in contrast to someone that actually has 17 years of experience with panels? You don’t actually know, you’re not an expert and you have zero first hand experience.

It is tiresome to answer disinformation.

#52

On our 5/12 roof, I knew the angle of the panels would not be optimal for production but the PV vendor said that they do not pitch an array on a residential roof because then you create lift and then you would need to do structural improvements vs just getting engineer to approve the structure for the slight (< 3# psf) load of the panels, rack, wiring, and microinverters. So not worth the expense for the extra production.