north facing array

[geniusenergy]

Well, a little bit off the subject, but look what has just come up in the press for the Northern hemisphere:

http://rt.com/uk/176316-solar-panels-uk-wrong/ - that is not related to Genius Energy and is an independent link mods

Quite an interesting read and yes, you are right... it seems some people have taken advantage of those with insufficient spacing or direction, which is terrible.

[russ]

Well, a little bit off the subject, but look what has just come up in the press for the Northern hemisphere:

http://rt.com/uk/176316-solar-panels-uk-wrong/ - that is not related to Genius Energy and is an independent link mods

Quite an interesting read and yes, you are right... it seems some people have taken advantage of those with insufficient spacing or direction, which is terrible.

Cheap and easy government money make things like this attractive to the PV seller.

I remember one Coliseum in Taiwan that had a roof covered with PV panels - at any given time 90% were of little use. I also remember the fool architect won prizes for it and the greens were covering him with praise.

About the same time there were a couple of good sized merchant ships with PV panels - the panels wouldn't even provide adequate power to the ship in port - let alone underway.

[J.P.M.]

This topic has got me thinking and I would like to know if anyone has an azimuth derate formula. Lets say you take an array and install it in an area with zero obstructions between 60 and 300 degrees azimuth. Lets say it was installed with the tilt being at latitude. Does any one have a formula for how much or how little of an effect on yearly production moving that array to the east or west by a certain increments would make?

The short answer is yes. Something of what you describe but more involved is part and parcel of solar design with respect to resource assessment and performance estimation.

I'm not trying to be rude, but if you do what you say you do, I'm a bit surprised you'd ask that question. I'd respectfully suggest that if you want to keep your job, you not tell your boss you asked.

[J.P.M.]

Well, a little bit off the subject, but look what has just come up in the press for the Northern hemisphere:

http://rt.com/uk/176316-solar-panels-uk-wrong/ - that is not related to Genius Energy and is an independent link mods

Quite an interesting read and yes, you are right... it seems some people have taken advantage of those with insufficient spacing or direction, which is terrible.

I'd need to see some #'s before I put any value on this. I've used canned software and written a fair amount of code and spreadsheets to get a lot of predictions of output for many types of systems both PV and thermal, and a fair amount of passive solar. I've also verified a fair but smaller amount of data with site measurements. I believe this piece is a piece alright - of H.S.

[geniusenergy]

I'd need to see some #'s before I put any value on this. I've used canned software and written a fair amount of code and spreadsheets to get a lot of predictions of output for many types of systems both PV and thermal, and a fair amount of passive solar. I've also verified a fair but smaller amount of data with site measurements. I believe this piece is a piece alright - of H.S.

That's an eloquent way of phrasing it! Hehe!

Well, it is interesting nevertheless and has opened up debate - I don't doubt your coding and calculations (N.Hemisphere relevant), but it will be interesting to see how solar companies react to this.. But yes, more research is needed.

[Ian S]

I fully agree with J.P.M.

A standard practice is to sign and whine - sign without knowing and then whine when restrictions don't suit you.

If one does not like the restrictions of a HOA then why by into it?

Oh my! I am in full agreement with both Russ and J.P.M. at the same time!!! Maybe it's because I've served - and currently serve - on our HOA board. A big part of the problem is nobody generally wants the job. Ours is a small association without a management company so if there's a dispute, there's no manager to take the heat. We are pretty easy going but we have to enforce the CC&Rs else one or other homeowners will take us to task - we have been threatened in the past with such legal action when an owner thought we were not sufficiently diligent in enforcing our CC&Rs. We're pretty good about approving changes a homeowner wishes to make but there are certain fundamental architectural features that we simply insist on keeping intact. They are usually the ones that attract buyers in the first place.

BTW, Russ, I really like that "sign and whine" line.

[J.P.M.]

That's an eloquent way of phrasing it! Hehe!

Well, it is interesting nevertheless and has opened up debate - I don't doubt your coding and calculations (N.Hemisphere relevant), but it will be interesting to see how solar companies react to this.. But yes, more research is needed.

Similar to wit, one of the hallmarks of eloquence is brevity. I have neither of those attributes in any discernible measure. The piece is still, IMO, H.S.

A small point - Any such calculations we're writing about apply to either hemisphere to be of much use.

Solar companies, or anyone knowledgeable in the subject matter will see the referenced piece for the pile of road apples it is.

Research is always needed, but this portion of the solar knowledge database has been studied in the modern era for something like 150 yrs. or more. I think it's been pretty well mined out by now.

[J.P.M.]

Oh my! I am in full agreement with both Russ and J.P.M. at the same time!!! Maybe it's because I've served - and currently serve - on our HOA board. A big part of the problem is nobody generally wants the job. Ours is a small association without a management company so if there's a dispute, there's no manager to take the heat. We are pretty easy going but we have to enforce the CC&Rs else one or other homeowners will take us to task - we have been threatened in the past with such legal action when an owner thought we were not sufficiently diligent in enforcing our CC&Rs. We're pretty good about approving changes a homeowner wishes to make but there are certain fundamental architectural features that we simply insist on keeping intact. They are usually the ones that attract buyers in the first place.

BTW, Russ, I really like that "sign and whine" line.

See - progress is possible in spite of our collective efforts. I'm going to go buy a lottery ticket before the good luck wears off.

[njguy]

Assuming for a minute that this is a conversation about reducing an electric bill, not providing solar electric for its own sake:

1.) For residential use, solar is almost always the least cost effective because almost anything else a homeowner can do to save a kWhr. of electricity for domestic use is almost always less expensive than providing that same kWhr. of electricity with solar energy. It's cheaper to save a kWhr. with insulation or a low flow shower heads, etc. than solar panels. Added to that, any solar electric added after conservation is maxed out will be smaller as a result of all the conservation efforts as a bonus of sorts. This is something the solar peddlers do not talk about. They make money putting solar electric equipment on your house, not saving you money. That's your job.
No offense meant, but you could probably have the $20 or so cost of a book called "Solar Energy For Dummies" back 100 fold or more in oversizing and other mistakes you'd avoid by spending a couple hours perusing its pages.

As a grossly oversimplified example for illustration purposes only, and realizing NJ is not CA:

2.) The costs for a new, EV: Assuming 12,000 miles/yr. and, say, 3 miles/kWhr. for "mileage" = 4,000 kWhrs./yr. required. In my neighborhood, a pretty decent solar climate, each Kw of installed solar will produce something like 1,600kWhrs./yr. of electricity to recharge the vehicle. The 4,000 kWhrs will thus require a 2.5 kW solar electric system. At the approx. going rate around here of , say $3.50/Watt less 30% tax credit, that's $6,125.00 after tax credits. Systems that small cost more /Watt, but like I wrote, this is an illustration only.

Initially assuming the EV is not purchased out of necessity (if it was you'd likely have to buy two new vehicles - one EV for local, and one ICE for intercity/long distance.), it's cost and the cost of the charging equipment, less a trade in vehicle are added to the solar electric system.

I have no idea what EV's actually cost, but assuming it's not a $100K Tesla, I'll use 25K plus tax, net, including a charger and after old vehicle trade in and after $7,500 tax credit.

So, vehicle and equipment acquisition costs ~~ $25,000 + $6,125 = $31,125.

3.) This needs to be offset against the avoided ICE fuel and ICE associated maint. costs. Back to the back of the envelope: drive 12,000 miles a yr. in an ICE vehicle that gets 30 MPG = 400 gal./yr. @$4.00/gal. = ~ $1,600/yr. Throw in 2.5 oil changes at $50/pop and $250/yr. for stuff the ICE needs that an electric vehicle does not. Total = $1,975.00/yr., say $2K SWAG.

Given those #'s, I'll be driving the EV a long time before I can justify its cost on the basis of fuel savings alone.

Now, before anyone goes after my head, rips it off and craps down my neck, I understand not everyone would include the vehicle cost in the calcs. And I'd be and am the first to agree that some situations do not require and should not include vehicle cost. If my car is about to die or is in a wreck, then adjustments can and should be made. I have also not included any trade in of the E.V. However, I'd suggest that unless the situation is such that a new vehicle was NEEDED, rather than an E.V. WANTED, The vehicle acquisition cost or some portion of it should be included in the calculation. The slippery slope is in separating WANT, from NEED. That's a personal choice. I once had a job with a co. car. I pitched for a Buick as it helped my and the co.'s image. I got a Chevy. My opinion vs. my boss and the cost accountants. Opinions vary.

As for an E.V. with no solar, most of the savings in fuel cost comes from the usually smaller E.V. size to begin with, making it easier to push down the road. Otherwise, most of the savings, in energy anyway, come from the much greater efficiency of electric motors (~ 55-60% ) as opposed to ICE ( ~ 20% +/- a bit depending). An E.V. might get 3 miles/kWkr. Buying at E.V. rates from my POCO, ~$.17/kWhr. -->> ~ $.17/3 = $.057/mile, +/- some. My 30 MPG ICE above has a simple fuel cost of $.133/mile. So the FUEL savings amount to $.133-$.057 = $.076/mile or 12,000 X $.076 = $912.00/yr. Assuming a NEEDED new vehicle, the Net Present Value (NPV) of the $912 s how much more one can spend on an E.V. vs. and ICE fueled vehicle and justify the extra cost, or call savings.

More back of the envelope and maybe an interesting factoid: 1 gal. of gas has about 33 kWhrs. of energy making its cost about $.121/kWhr. at $4.00/gal. - less than the cost of POCO off peak power in my example.

BTW, If I charge at $.37/kWhr. peak rate (Don't do this at home kids) the E.V. $/mile rate goes to $.37/3 = $.123/mile, sort of close to the ICE rate.

As for cleaner energy options, they may be. However, the hype and emotion fueled half or less truths that are often no more than parroted verbal spoor originating at the extremes of both sides do not make the waters less muddy and are, IMO, less than helpful at getting to solutions.

As for what to do with $14K, that's a problem in something called life cycle costing, or comparison of alternatives. That amounts to in effect, making assumptions about the future directions of inflation, fuel costs, how long a time frame, alternative rates of return, the time value of money and as much other stuff as you deem pertinent. It's usually more than finding an investment that will return more than $14,000/6 yrs. = $2,333/yr.

Thanks for the education. This does really help. As someone already said on here, there are some great deals on EV's. Some, with the state, federal, dealer and manufac. incentives end up being priced nearly identical to their ICE counterpart. Ford Fusion is one example of that. For sure you have to look at more than just how much your investment will return over time and I like the life cycle costing idea. Makes perfect sense. In the end it really is a toss up but I'm leaning towards not doing anything just yet. If my neighbors tree was down I think I'd get an extra 1.5 to 2 hours of production out of the panels between 3:30pm and 5:30pm in the summer months.

Does anyone have a simple answer as to how much (say a 270KWH panel) will produce on a sunny day where you get all sun for 6 hours? If I had all sun for 8 hours what would the extra production be. If it's minimal then maybe it's not a big deal. So much to learn and I know I feel uneducated about the whole thing which is why I'm not moving on it just yet. Maybe the Solar for Dummies will help.

[J.P.M.]

Thanks for the education. This does really help. As someone already said on here, there are some great deals on EV's. Some, with the state, federal, dealer and manufac. incentives end up being priced nearly identical to their ICE counterpart. Ford Fusion is one example of that. For sure you have to look at more than just how much your investment will return over time and I like the life cycle costing idea. Makes perfect sense. In the end it really is a toss up but I'm leaning towards not doing anything just yet. If my neighbors tree was down I think I'd get an extra 1.5 to 2 hours of production out of the panels between 3:30pm and 5:30pm in the summer months.

Does anyone have a simple answer as to how much (say a 270KWH panel) will produce on a sunny day where you get all sun for 6 hours? If I had all sun for 8 hours what would the extra production be. If it's minimal then maybe it's not a big deal. So much to learn and I know I feel uneducated about the whole thing which is why I'm not moving on it just yet. Maybe the Solar for Dummies will help.

The short answer to you question is: Probably not with any accuracy.

The simplest way to get a reasonable first approx. for unshaded yearly array performance on a long term basis: PVWatts. Just take your time and read all the info/FAQ screens before you start. Then read them again, use a .84 derate factor, and rerun. An hr. or 2 spent doing this can be an education.

What you're asking is a valid question but not too meaningful in the quest to figure out if solar makes sense to and for you. Honest: my opinion is that the Solar for Dummies will probably help. IMO, it's definitely worth a sniff. as I alluded, $20 or so and a couple of hrs. or so spent to increase the probability of a better choice for the information gained is a bet I'd take.

Most folks start with their annual usage, usually by month, some idea of what their rate structure looks like, and how their POCO (POwer COmpany) charges them, and then sizes the solar electric according to what they feel they want and/or need. The smart money usually and often goes for the size system that results in the lowest "Levelized Cost Of Electricity (LCOE) as determined by a life cycle cost analysis. NREL has a few sites that give a thumb sketch dart throw on LCOE schemes.

As for life cycle costing and how it fits into LCOE and other financial and/or economic considerations, there are too not many rigid rules. By and large, a lot of it is really common sense, involving things like the time value of money and comparison of alternatives, among other things. Most situations are somewhat unique, but often with a lot of common traits. Such an analysis can be as simple or involved as the user deems necessary. Usually, the more variables considered, the more complicated the analysis. Also, because a lot of the analysis uses estimates and assumptions about a future not yet written, it does involve some uncertainty. Being a good guesser helps when you need to take your best shot. Sometimes, people are intimidated by the #'s, but patience can win out. There's a tome on the NREL website about process economics and solar energy and it's free for the download.

Take your time and be deliberate. The answers are there and here for the reading and asking.

[prhamilton]

From 4:00-6:00 I make about 12-15% of my total output. I won't expect to lose all of that production but it might derate your system by 6-10%.

When you go through the process they will do a site survey estimate shading from trees and give you better production estimates.

[njguy]

This is pretty cool

https://sam.nrel.gov/

I am just learning how to use it but I think it's a big help and provides a ton of info.

[J.P.M.]

This is pretty cool

https://sam.nrel.gov/

I am just learning how to use it but I think it's a big help and provides a ton of info.

I'm glad you found SAM. It's a real valuable tool. I understand, applaud and encourage your enthusiasm.

However, I'd very respectfully, but very strenuously suggest, as friendly advice, you do 2 things:

1.) Start with PVWatts before you attempt SAM. It will give you most everything you need initially. Learn to walk before you run.

2.) Before you tackle SAM, do yourself a favor and make sure you understand every term it uses and every calculation it does and how the various subsystems interact and impact one another.

If you jump into SAM too soon, it is somewhat analogous to someone who just got a learner's permit jumping into a formula one car and racing at Lemans and hitting the gas. I've been using SAM for 3+ yrs. or so. It still throws me for a loop once in a while. As I recall it took me about 30-40 hrs. before I got accustomed to it's power and also it's quirks and blind spots. It's worth it, and quite powerful, but it ain't an out of the box plug and play type of program by a longshot.

It takes more than a little prior knowledge of the technical, engineering and economic aspects of solar energy to use SAM as intended and get useful, accurate and correct info from it. Look at who it's targeted audience is as listed on the front page of your attachment. I am of the respectful opinion that you may not be at that point yet. At least understand what PVWatts is all about first. You won't be sorry.

[njguy]

J.P.M. Thanks for your wisdom and patients with my newbie questions. I will indeed learn PVwatts first (learn to walk before I run) and move into SAM. As a computer guy the program itself intrigued me but I definitely need to learn the terminology.

All that said, I still am not quite sure, are you a proponent of solar or not? It seems your not buy with your knowledge I thought you might be more for it then against it.

Anyway, you keep teaching and I'll keep learning. I will know more then the sales reps for these companies.

[shocknocka]

Are you new to business?

I am new to the business. I have only been working in solar for a few years. I am here to learn and to pick the brains of professionals who are more experienced and knowledgeable than myself. Do you have an answer to my question? I could really use a field formula that i can use when talking to our salesmen and customers about why certain facing arrays will not be as beneficial to them. I don't always have access to PV watts.
Thanks