Solar Electric Assist--- NOT working

[meierlde]

Found a web site that shows preferred angles for solar panels: Optimum Tilt of Solar Panels
Note that at 40 degrees a fixed panel is recommended to be at 33.5 degrees for 71% of the max. The site also shows that with a summer winter angle change, it is 16.2 in the summer and 54.2 in the winter at 40 n. with 76% of optimum a small change for adding a lot of complexity. (However at 54.2 in the winter snow would likley not stick very long to the panels however. )

 

[ERD50]

....
In northern Il, and MN where I am, more energy is used in winter.
Maximizing efficiency for the system over a year makes sense financially.
Maximizing efficiency when you use the most energy (typically January) makes more sense if you want to use local energy. ...

I don't know about MN, but in N-IL there is definitely more kWh demand in summer. A/C is in use, and most people have NG heat.

Your next two statements do not make sense unless we were actually over-producing with solar in the summer. We are very far from that. If an individual is over-producing (compared to their own usage, not the grid) in summer, and they don't get any credit for that over-production, then it could make sense to angle closer to winter. But with lower total annual production, payback (both environmentally and financially) will be longer. In that case, it really doesn't make sense to size your panels larger than your consumption. Well, as I've talked about before (along with samclem), residential solar panels really don't make sense at all (unless you need to be off-grid). Commercial level installations, make far more sense in every way, and there should be opportunities to buy into a 'share' of that installation.

I think I read that Germany is getting to that point of over-production of solar on some days (in terms of time of day, not sure about the seasonal aspect of it), and new installations must be oriented east or west to stretch out the supply a few hours longer.

Even when maximizing for the whole year, one can maximize for the kWh, or for the $. My utility charges more for the kWh during the summer than in the winter.

So, for me I would maximize the kWh for the summer, which also means max $.

We have two-tier rates in summer only, to help motivate conservative use of A/C. They will offer a discount if you let them turn your A/C off during peaks (limited to something like 15 min/hour), and you can call and get an over-ride once or twice a month (makes sense, for the times you may have a big gathering on a hot day, but you would conserve other-wise). See below for more...

Found a web site that shows preferred angles for solar panels: Optimum Tilt of Solar Panels
Note that at 40 degrees a fixed panel is recommended to be at 33.5 degrees for 71% of the max. The site also shows that with a summer winter angle change, it is 16.2 in the summer and 54.2 in the winter at 40 n. with 76% of optimum a small change for adding a lot of complexity. (However at 54.2 in the winter snow would likley not stick very long to the panels however. )

Nice detailed site. I'll take another look, I don't recall whether the 20 degree number I mentioned (as opposed to the optimal 33.5 degree angle that site mentions) came from something I read, or it just looked that way to me. But it's also possible that their agreement with the local electric supplier called for optimizing for summer, since peak energy during hot summer usually sunny days is what costs the suppliers.

OK, here's their intro video, and a google map view. They sure don't look like anywhere near 30 degrees, and those are flat roofs:

Libertyville District 70

https://goo.gl/maps/W1J93YVcPD42

-ERD50

 

[meierlde]

Re Overproduction on sunny afternoons, Predictions show that the same situation will occur in California soon, it is called the duck curve when demand actually starts dropping when traditionally it increased. The peak demand is moved back to post sunset in this situation, which means power plants get throttled back in mid afternoon, and forward after sunset.
Note that if you build long distance HVDC lines, the east would not have the problem, as the best solar is on the high great plains (less clouds etc). That gives you an hour and a half of delay before the solar peak abates.

 

[NW-Bound]

Here in the Southwest, in the summer the solar power production tapers off in the afternoon, then is gone at sunset, while the power demand stays high way late into the evening. It is often still 100F at 10PM, yet in the early evening people get home and start to cook.

So, let's say we have homes A and B, each needs 5kW. Home owner A puts in a solar system that provides 7.5kW. Then, the utility only needs to produce 2.5kW during the day, but in the evening it has to crank out 10kW. That high-peak demand still requires them to have all the infrastructure in place, and that equipment is expensive to maintain, even if you do not run it 24/7.

My utility is a federal agency that also manages the watershed (hence the related hydraulic power generation). It has changed the pricing structure to get compensation for the peak that solar home owners use.

The solar savings is now less than it was, and existing solar home owners got grandfathered in. I do not know if the pricing structure is transferable if the home owner sells.

 

[ERD50]

...
So, let's say we have homes A and B, each needs 5kW. Home owner A puts in a solar system that provides 7.5kW. Then, the utility only needs to produce 2.5kW during the day, but in the evening it has to crank out 10kW. That high-peak demand still requires them to have all the infrastructure in place, and that equipment is expensive to maintain, even if you do not run it 24/7.

....

Yes, and it aggravates me to see these headlines from the 'green' sites that announce 'solar is now cheaper than fossil!'. They are talking about the lifetime cost, which is fair (initial cost for solar plus a little maintenance, versus initial cost for coal or NG plant, plus maintenance and fuel over their lifetime), but they 'forget' to mention, that solar plant still needs that backup infrastructure. That changes the numbers. A lot.

-ERD50

 

[RobbieB]

It doesn't make sense to oversize a residential system.

It makes sense to avoid paying 30 cents a kWh but it doesn't make sense to sell it for 4 cents which is what happens to the excess you generate in my area.

 

[NW-Bound]

I wonder how they define the "excess". Is it an average of power over a day, a month, or a year? If it is instantaneous, then it is not good nor fair to the home owner. An example follows.

Say, you have an AC that takes 5 kW, but it cycles on/off and it is on only 50% of the time. Your average power consumption is then 2.5 kW. So, you put in a 2.5kW system. That should cancel out your power usage, but only on the average.

During the time the AC is off, all of your 2.5 kW is "excess" and they get your energy too cheap. And then when your AC is on, you are still short 2.5 kW, and they charge you more. If they do not look at the average and only use the instantaneous numbers, you will lose, and I have to say it is not fair.

 

[RobbieB]

Here it's per year at your annual true up. If you generate more than you use (over 1 year) they write you a check. They pay you for the excess generation at the wholesale rate which is currently 4 cents a kWh.

Under that they have to pay you what they charge you, but over is at the wholesale rate.

 

[NW-Bound]

OK. In that case, it is not likely a home owner can produce more than he uses in a year. You would not make that much in the winter. And then, in the summer, your AC still has to run for a long time after sundown.

 

[meierlde]

I wonder how they define the "excess". Is it an average of power over a day, a month, or a year? If it is instantaneous, then it is not good nor fair to the home owner. An example follows.

Say, you have an AC that takes 5 kW, but it cycles on/off and it is on only 50% of the time. Your average power consumption is then 2.5 kW. So, you put in a 2.5kW system. That should cancel out your power usage, but only on the average.

During the time the AC is off, all of your 2.5 kW is "excess" and they get your energy too cheap. And then when your AC is on, you are still short 2.5 kW, and they charge you more. If they do not look at the average and only use the instantaneous numbers, you will lose, and I have to say it is not fair.

Once upon a time the reimbursement was at the retail rate but that put the bill on users who did not have solar. If you think about it if you are putting power back onto the grid you are just like a generator selling power at the substation to the distribution system. Thus getting paid the wholesale price for power you pay. It does change the economics somewhat. This has been a large part of the arguments in western states in the last couple of years. Which is why utility scale solar makes economic sense, not rooftop solar.

 

[Gumby]

Originally, I thought that one should angle the panels to achieve max efficiency when you need the most electricity. But upon further contemplation, I think the answer depends more on your area as a whole and not on your own electric needs.

Assuming that you are not totally self sufficient off grid and instead just sell to the grid when you have excess, it now seems to me that the optimum angle for your solar panels should be informed by whether your local utility is summer peaking or winter peaking, because you'll get the best price during the peak use season. So, if your utility is summer peaking, angle your panels from the horizontal at your latitude minus 15 deg. Winter peaking: latitude plus 15%.

Let assume for the sake of argument that the people in the OP use the most electricity in the winter, but that in general, the area is summer peaking as people use their air conditioners. In that situation, even though you personally need more electricity in the winter, you might be better off selling in the summer and buying in the winter.

 

[NW-Bound]

The new pricing structure from my utility, which again is a federal agency and not a commercial corporation, encourages people to maximize their summer solar power production towards the late afternoon, not around noon time. It's because of the thermal lag, which causes the AC to run harder after the home has been heat-soaked for a couple of hours.

The demand rate that I pay for non-solar homes has reflected the above fact ever since it was enacted perhaps 20 years ago. The high demand rate in the summer starts at 1PM, and ends after 8PM. Of course the solar production drops off after 5PM already, or maybe even earlier.

PS. It is not that home owners have much flexibility in mounting their panels to maximize to anything. You cannot reorient your house, before you can even talk of tilting them for better efficiency.

 

[skipro33]

I did not know this. But my utility page does not have anything on this either.

Their hour-by-hour display of my usage lags by only a day. They are showing the 24 hours of yesterday as I look. It's good enough, and I log in to check once every few months.

I guess if I had a solar system I would be inclined to monitor more closely to see the variation of power production.

My utility company is PG&E.
I googled PG&E zigbee smart meter and came up with this site of theirs;

https://www.pge.com/en_US/residenti.../reading-the-smartmeter/stream-your-data.page

Maybe you can google the same for your utility company.

 

[Zathras]

ERD, you are absolutely correct. Unless you are producing all your power from solar, or want the power at specific times or seasons (either as an individual or grid level) it doesn't matter.

In my case, we are net zero, and having as little impact on the grid is one of our priorities.
Low maintenance is another.

I'll try not letting my own priorities color this much.

If the schools do have panels at that low of an angle, they are loosing annual production. They are also loosing even more power if they are not clearing panels when snow covered.

If they have a reason to want to produce more power around June at the cost of power production August through April, they are perfectly aligned.

I don't know what their goals are, but if it was annual production, they missed.

 

[imoldernu]

Looks to me that this was simply a matter of bad planning. Just as we see huge cost overruns in federal government planning (as in the F35), a matter of rushing to develop a program,without putting the individual pieces together first.
Based on the many thoughtful posts above, it's easy to see that while the parts are known or discoverable, it was a matter of putting the cart ahead of the horse. A sad result that will put another bump on the road to viable solar energy.

BTW... a related subject. Smart meters. You should be aware of the pluses and minuses of this soon to be universal electric company project. The advantages that are touted on the introductory information media are not all quite as positive as they seem. Just sayin'.

 

[mpeirce]

Have any of you folks playing around with home solar electrical generation added in one of the Tesla battery packs for load balancing?

 

[Zathras]

Looks to me that this was simply a matter of bad planning. Just as we see huge cost overruns ...

I suspect that was it. However, it isn't THAT big of a deal. The difference is only about 4% in annual production, and as I said, there may have been other reasons for missing out on a couple of MegaWatts/year (out of 56-60MW total)

Have any of you folks playing around with home solar electrical generation added in one of the Tesla battery packs for load balancing?

We are on the waiting list and are hoping to have ours installed by the end of May. In our case, this is primarily for backup purposes, although we may use it a bit for load balancing at times.

 

[ERD50]

If they have a reason to want to produce more power around June at the cost of power production August through April, they are perfectly aligned.

I don't know what their goals are, but if it was annual production, they missed.

From those articles, and looking at the video, they do seem to have them optimized for summer. That article talked about an ~33 degree angle overall for summer (changing the panel angle only 2x or 4x a year). But at our ~ 42 latitude, minus summer high sun at a 23.5 degree shift would bring us to an
18.5 degree angle for the panel, which looks close to what they have. A little higher angle would get you optimized for July/Aug, the hottest months.

Again, I'm guessing this is what the power company contracted for. Summer rates are the highest here, due to A/C peaking, and the most likely time to be stressing the grid capacity. Between the summer ambient heat, and self heating from high currents through wires and transformers, there have been cases of these transformers blowing, or insulation breaking down on high demand hot summer days. So maximizing summer power, rather than annual average, makes sense for the power company. And they would need to make it financially advantageous to the school (though the higher summer rates alone may do that).

Tesla PowerWall:

... We are on the waiting list and are hoping to have ours installed by the end of May. In our case, this is primarily for backup purposes, although we may use it a bit for load balancing at times.

I was under the impression that there are two different units they sell - one for emergency backup, the other for load balancing. And that the emergency backup units could not handle the higher number of cycles for load balancing? Is that why you say "use it a bit"? What are the limits of using it this way?

-ERD50

 

[ERD50]

...

BTW... a related subject. Smart meters. You should be aware of the pluses and minuses of this soon to be universal electric company project. The advantages that are touted on the introductory information media are not all quite as positive as they seem. Just sayin'.

Please don't be so cryptic! What are these negatives you allude to?

-ERD50

 

[HFWR]

Which is why utility scale solar makes economic sense, not rooftop solar.

I understand why some want their own installation: reduced usage, lower bills, being "green", sticking it to "the man"...

Why do we never stick it to "the woman"? [emoji12]

Utility/commercial/industrial installations seem to make more sense, globally. Better site selection, better or adjustable panel orientation, economies of scale...

 

[jazz4cash]

Please don't be so cryptic! What are these negatives you allude to?

-ERD50

Agreed! I have my own experience to to share but would really like to hear imoldernu's opinion.

We've had them since 2012 and the only benefit I see is that the utility doesn't need to send meter readers out which lowers their cost.

• They don't appear to notify the utility of outages.
• The billing cycles still vary from 28-32 days for some reason and they are longer in winter which is a hardship for some people.
• They don't interface with the Zigbee device from what I can tell. The hourly usage data is available on a 24 hr delayed basis.
• They didn't detect a short condition at our meter that could've burned down our house.
• Initially they provided a projected monthly cost on their webpage but I guess they got too many complaints when the projections were not accurate so this feature was eliminated.

 

[imoldernu]

Please don't be so cryptic! What are these negatives you allude to?

-ERD50

Yeah...
So the long term effect is probably positive, but the benefits have gone directly to the power companies, while the cost has been borne by the consumer. In our Florida home, the new meters were installed three years ago, at the same time that the KWH cost was increased by 15%. (We were treated to a presentation by the company that we would reap savings by timing our power usage... yup! Just do the wash after 10 PM...
In Illinois, at our campground, Commonwealth Edison now charges $.14 KWH and has increased the base rate, while our Peru cost is still well under $.10 KWH.

This article favors the benefits, but doesn't get in to the details of charges to the customer, which, while probably being morally correct w/regard to the environment, comes at a cost to the homeowner with the power companies reaping the profits.

https://www.thebalance.com/pros-and-cons-of-smart-meters-1182648

 

[ERD50]

Yeah...
So the long term effect is probably positive, but the benefits have gone directly to the power companies, while the cost has been borne by the consumer. In our Florida home, the new meters were installed three years ago, at the same time that the KWH cost was increased by 15%. (We were treated to a presentation by the company that we would reap savings by timing our power usage... yup! Just do the wash after 10 PM...
In Illinois, at our campground, Commonwealth Edison now charges $.14 KWH and has increased the base rate, while our Peru cost is still well under $.10 KWH.

This article favors the benefits, but doesn't get in to the details of charges to the customer, which, while probably being morally correct w/regard to the environment, comes at a cost to the homeowner with the power companies reaping the profits.

https://www.thebalance.com/pros-and-cons-of-smart-meters-1182648

I think you are conflating "Time of Day" rates and billing, which require a smart meter (or at least 'smarter'), and the basics of a smart meter itself.

We got smart meters installed late last year. No rate changes, it's all the same, except now I can get by-the-hour usage (24 hour delayed). I think I have the option of going to TOD, have not looked into it. All I see are benefits.

Regarding the meter reader - I am amazed(*) that the gas & electric utilities here did not join forces and have the same person read both meters at the same time. It would cut the time/effort/cost (and exposure to dogs, wasps, etc) almost in half, they spend most of their time walking/driving through the neighborhood.

(*) - OK, maybe I should not be amazed, these are regulated monopolies, to paraphrase Tina Turner, "What's efficiency got to do with it, got to do with it?".

-ERD50