Interesting facts about solar power

[ERD50]

Here are some interesting facts about solar power. There is certainly a great opportunity here for a person of vision.

7 impressive solar energy facts (+ charts) - ABB Conversations

Well, they are interesting and impressive, but when you add context, I'm not sure where we go with this. What 'great opportunity' is so certain?

Some context: OK, so the earth receives many times more solar radiation power than other sources we have. I don't think they are factoring ~ 10% efficiency in capturing/converting, and of course it's absurd to even think about covering every square inch of land with solar collectors. So it's a rather meaningless number (but still impressive).

So for some perspective, let's get down to the personal level. I went to a solar panel site, entered my location (N IL) and household electrical usage (rounded to 1 MWh/month, 12/year), and asked to calculate how much panel space I would need to 100% replace my average annual consumption (average will be important later). It said 898 square feet of roof space, let's count on some future eff improvements and round down to 800, or about 20 feet by 40 feet. That's a fair amount of south-facing roof (I'll ignore the costs for now).

But that's only a portion of my energy usage, let's look at more if we are thinking solar can replace these other sources. So let's say I replace my cars with EVs. If I assume the average 12,000 miles on one car, and say 6,000 for a second vehicle per household, we need enough KWh for 18,000 miles. Assuming 300 watts per mile at the charger, that's another 5.4 MWh to add to the 12, getting up to ~ 1160 sq feet of panels (58' x 20').

OK, how about heating my house? Maybe thermal would be more efficient, but would I have room for thermal system that would be mostly used in the winter months, and enough for the PV also. So for simplicity, I assumed PV and a heat pump with a COP of 3.0, and converted my NG gas usage to therms to BTUs, etc.

That brought up another point - my peak energy usage is in winter. Even my electric bill is generally higher in Jan-Feb than in the summer (running lights more hours/day, running the furnace blower?), unless we get a real heat wave. So my peak energy usage is in a month with low solar energy available to me - a double whammy. I found month-month data for solar panels adjusted throughout the year versus a fixed 'optimal', and I would still need ~ 25% more panels for the same power in Jan-Feb as the average numbers they use in their calculations, assuming I adjusted the angle of my panels throughout the year (or maybe just optimized for winter, and 'wasted' energy the rest of the year?).

So when I factor that all in, I come up with over 1500 sq feet of south facing panels ( 75' x 20' ). The narrow side of my house faces south ( ~ 35' wide with overhangs?), so that would be some structure to get that many panels up there spaced out so they don't shade each other. It might start shading my neighbor's house?

And we haven't even talked about the businesses that I trade with. I imagine most businesses are more energy intensive than a home.

And that assumes we have storage technology. Heck, it isn't practical to store a day's worth of power overnight, or even a few hours. How would we store enough for a week or more of overcast days?

So that's part of the problem with most renewables - you either need massive storage on a huge scale (and even more energy sources since storage always involves losses), or we keep the entire infrastructure in place so we can handle an extended outage. And you can't ramp up a lot of those sources quickly, so you at least need enough storage to get you through the ramp up. All that makes it outrageously expensive - one or more days of storage plus a full infrastructure ready to roll.

It might sound impressive, but it gets complicated very quickly.

I just saw an article about how residential solar installation can hurt utility companies in a controversial way. ...

Yes, I've been seeing some of these articles also. I have not dug into them very deep yet, but it's easy to see some of the issues. A solar panel install that nets to zero gets the use of that grid for free (or close to it). I've read that as solar approaches 10% of the total power, it is causing problems for the grid operators, as they don't have control over the sun. As I pointed out above, you still need nearly all the base line and peaker power and grid capacity ready, in case a spike in demand occurs during a shady period.

Grid operators have to run a fine line between cutting back their baseline power (usually coal), and relying on their more expensive peaker plants to cover any drops in sun/wind. Cut too much base line and costs go up, and you risk brown-outs. Cut too little, and the sun/wind go to waste.

I still say conservation seems cheaper, more achievable and would provide more actual results than current attempts to hit some magic X% of renewables, with today's (or the next decade's) technology. I think other power sources will come on-line - when they are ready. If they are pushed before they are ready, we will likely have back-lashes and more problems.

-ERD50

 

[meierlde]

I just saw an article about how residential solar installation can hurt utility companies in a controversial way. It's when the utility companies are required to buy back or just to offset the residential power production via net metering. This complaint by utility companies makes sense when we consider that a KWHr is priced at the homeowner's meter, so that the cost includes delivery charges, meaning the maintenance of the grid. A homeowner selling power into the grid does not incur that cost, hence is subsidized by other homeowners.

I guess if the cost for grid connection were separated out from the KWhr consumption or production then the pricing would be fair. However, it is rarely done that way. By the way, at a recent utility commission hearing in AZ, a utility company claimed that the grid cost for each home is $1000/yr. That number seems high to me, but I am not knowledgeable about this matter.

The way you suggest is how electricity is priced in the de-vertically integrated (de-regulated) areas of the country. Everyone gets their electricity from the same distribution network, but you contract with a reseller to buy your electricity. The distribution network gets a fee. Now the change (that might require a change in the meters) would be to charge the distribution charge both ways, but net meter on the energy charge. (The bill is energy charge plus distribution charge plus customer fee)

 

[ERD50]

...

If I'm making any point, it would be that solar water-heating is "simple", inexpensive, generally effective and easy to engineer. Yet, we hear much more about PV systems which (while they do work) have many limitations and much higher costs of installation. Not saying PV isn't good - just making a case for pushing the "easy" fixes first and THEN adding PVs as time/money/improvements, etc. evolve. YMMV

Solar water heating is simple in areas where it does not freeze. I've also been amazed that it isn't more common in those places. It seems crazy to provide incentives for people in frost areas to put them in, if they aren't already being done w/o incentives where they make the most sense. One size does not fit all.

For me, PV might make more sense in that it is power I use all year round. In the summer, I only would use a thermal system for hot water, and that costs me < $30/month in NG. That has never been worth the cost of a system for me, and I've considered a complete DIY approach to save $. In this area, you need the full glycol system, insulated panels, heat ex-changers, storage tanks, etc. And a larger one would be underutilized 8 months of the year, making it a poor investment.

As much as I'd like to, I've never been able to make the numbers work. And I doubt a prospective buyer would want to deal with all the extra complexities. I don't think I'd ever get my money out of it.

-ERD50

 

[ERD50]

Another point to put into perspective - they talk up the drop in solar panel prices. That is tapering off, I don't expect such steep drops going forward (a search would probably come up with some estimates).

Bu more importantly, as solar panel prices have come down, they are a smaller percent of the overall cost. The mounting brackets, labor, and inverters are now a major component of the cost (more than the panels?), so dropping panel prices are just a subset of cost.

We can't expect labor to drop or metal brackets to drop, and inverters are very mature tech, not likely to drop fast.

-ERD50

 

[jimnjana]

The price of pv panels is likely to drop to under 40 cents a watt by 2017, at least according to
PV Module Costs To Decrease To $0.36/Watt By 2017

Our solar contractor has developed a hybrid solar hot water solution. Using any electric hot water heater, he is replacing one of the heating elements with an element that is supplied DC from a small array of 3 or 4 pv panels. This cuts electric used to make hot water by more than half.

I think solar has a way to go before it is viable without subsidy in most of the country. So far we are very happy with our nearly 10KW system.

 

[ERD50]

The price of pv panels is likely to drop to under 40 cents a watt by 2017, at least according to
PV Module Costs To Decrease To $0.36/Watt By 2017

Our solar contractor has developed a hybrid solar hot water solution. Using any electric hot water heater, he is replacing one of the heating elements with an element that is supplied DC from a small array of 3 or 4 pv panels. This cuts electric used to make hot water by more than half.

I think solar has a way to go before it is viable without subsidy in most of the country. So far we are very happy with our nearly 10KW system.

I think they are referring to the cost to manufacture the panels (and even that may be the lowest cost producers, not average. End users will pay more. And again, add in mounts, labor, inverters, wiring.

Interesting about the DC going straight to the water heater. Saves on inverter costs and losses, and the tank provides storage. Simpler than a thermal unit in freeze zones. Not really applicable if you have NG for water heating though, as that will likely be cheaper than selling/offsetting KWh to the utility.

-ERD50

 

[stargazer08]

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This is a pic of my horse barn. That is a $150 45watt PV panel kit on the roof from Harbor Freight that powers a few dc lights in my barn. The panel charges a marine battery.

That corrugated pipe catches the rain water and fills the water troughs that are linked with a wee bit of hose so the first overflows into the second. I have added a 3rd trough since this pic. Once I got this set up, I didn't have to haul water to the horses all summer. For the winter months, I have a passive solar heater for one trough. Basically it's a plywood box painted black that is insulated with a window in the front to help heat the trough. Works good for our mild southern Illinois winters.

I don't want to spend the $10,000 to run electric to the barn nor do I want to pay $30/month for water hook up. I also use solar electric fence chargers to partition off my pasture.

 

[daylatedollarshort]

Cool set up, stargazer08.

I have been surprised more houses in our neighborhood don't have solar Christmas lights up. Ours were cheap, they work great and we don't have to bother with timers or fuss with extension cords.

 

[samclem]

I'd say that residential solar is getting very close to be a viable investment w/o government subsidy in the next year or two, If the rate of decline in cost of installation continues.

US solar power costs fall 60% in just 18 months: pv-magazine

I was under the impression the decreased costs of PV were due to overproduction of PV panels in Asia. If that's right, then the cost per watt will increase once there's a shakeout in manufacturers/production capacity.
Are the decreases in costs sustainable? Are they even desireable (from the perspective of the industry)?

 

[samclem]

That [solar water heating] has never been worth the cost of a system for me, and I've considered a complete DIY approach to save $. In this area, you need the full glycol system, insulated panels, heat ex-changers, storage tanks, etc. And a larger one would be underutilized 8 months of the year, making it a poor investment.

As much as I'd like to, I've never been able to make the numbers work. And I doubt a prospective buyer would want to deal with all the extra complexities. I don't think I'd ever get my money out of it.

-ERD50

I've thought about something like this. It would be more of a fun DIY science project than anything practical. I've considered a small system just to raise the temp of incoming water 20-30 degrees F before it gets to the NG water heater (take the "easy" initial increment temp rise and also it would useful year-round). A simple well insulated barrel filled with water as a storage/exchange medium with a coil of PEX with the incoming water and another coil of PEX with the working fluid (nontoxic antifreeze solution), use one of the new cheap PC-on-a chip microcontrollers running a small pump to bring the fluid to a homebuilt collector panel located somewhere convenient. Run the pump only when the water from the collector would produce a temperature rise in the holding/exchange barrel. I've got space in the utility room for a barrel, and any small heat loss would heat the house (which is good 8 months of the year).

It could be done pretty cheaply, data collection (for analysis of cost/effectiveness) would be easy using the microcontroller (they have USB connectivity to PCs), and the whole thing might even be cost effective if a person built everything themselves and was using high-cost electricity for water heating. In an emergency, 10 gallons or so of hot-ish water in the PEX would be useful. But you are right--it would be a liability at resale time, best to get rid of it before showing the house.

 

[bld999]

Drainback systems work well for hot water, but pumping costs are high due to a non-pressurized loop. No glycol needed.

But if it competes with cheap fuel, it won't pencil. Horizontal drilling with resultant cheap gas kills most solar once you remove subsidies. You have to do it because you want to, or leave it be.

 

[Chuckanut]

Here is an interesting take on solar energy in the USA from a meteorologist. Check out the Friday, April 17, 2015 blog entry.

Cliff Mass Weather Blog

The southwest U.S. is the Saudi Arabia of solar energy, with the highest values stretching from western Texas to California. It is really better than Saudi Arabia, since there is huge population hungry for energy in the Southwest (e.g., Los Angeles, San Diego, Las Vegas, Phoenix, Tucson, etc.) Lots of sun during the day, exactly when folks need it for air conditioning and their daily lives.

If you don't live in the Southwest, don't give up hope:

It turns out the photovoltaic cells are sensitive to temperature, with efficiency greater at COOLER temperatures.

 

[ERD50]

Here is an interesting take on solar energy in the USA from a meteorologist. Check out the Friday, April 17, 2015 blog entry.

Cliff Mass Weather Blog



If you don't live in the Southwest, don't give up hope:

Interesting? Maybe, but in the wrong way, I would say. This is just solar fan-boy fluff. Notice the lack of actual numbers to back up the statements? Why is that?

But what about here in cloudy Seattle? ... One of the faculty members in my department installed a solar system two years ago. ... His estimated payback period is 7 years. Even without subsidies his solar array would make financial sense.

Really? Show me the numbers. What is the payback w/o subsidies, and considering the cost of the money?

But cooler temperatures makes our solar panels more efficient, partially leveling the playing field for us a bit.

How much? Notice the graph has no numbers on the axis, and the author offers nothing. And lower temps are during the winter, with shorter days, lower angles - so any added efficiency then gets a low overall annual weighting.

I looked for other output/temperature graphs for comparison, and even worse than not including numbers on the axis, the graph in this article doesn't even go to zero - and no indication of it. They are zooming in on the relatively small deltas. Pretty misleading.

When I see things like this, obvious bias, I always ask myself - if the story is so great, why can't you present it w/o bias? So I assume the story is not so great, and I'd bet that I'm right.

-ERD50

 

[daylatedollarshort]

Our utility's solar calculator gives us a 12.9 year payback period for tie into the grid solar power. I like the idea of solar power, but that is a pretty long payback period for us as we would probably downsize before then.

 

[Totoro]

Our utility's solar calculator gives us a 12.9 year payback period for tie into the grid solar power. I like the idea of solar power, but that is a pretty long payback period for us as we would probably downsize before then.

A 13 year payback is a 7.6% return on investment, so why not?

If you move out presumably your house has a bigger sale value then as well, since the new owners get a lower electricity bill.

 

[Totoro]

I looked for other output/temperature graphs for comparison, and even worse than not including numbers on the axis, the graph in this article doesn't even go to zero - and no indication of it. They are zooming in on the relatively small deltas. Pretty misleading.
-ERD50

Did a quick google search, this guy did an experiment.

Effect of Temperature on Solar Panels - Solar

30 degrees celsius vs. 75 degrees is a drop off of 40% in efficiency. So it depends on how hot the roof gets I guess.

It's more of an altitude factor though (high & sunny = still cool), not how close to the equator one is.

 

[Totoro]

This is an interesting interactive map:

Mapping Solar Grid Parity in the US : Greentech Media

Without subsidies it shows some states as having reached grid parity today. With the federal tax credit it's basically ok everywhere.

Even more interesting is what happens with further sliding costs five years out (a prediction of course).

[Edit} The application is outdated though. You need to put in current electricity prices (have they gone down?) and current system costs.

 

[ERD50]

This is an interesting interactive map:

Mapping Solar Grid Parity in the US : Greentech Media

Without subsidies it shows some states as having reached grid parity today. With the federal tax credit it's basically ok everywhere.

Even more interesting is what happens with further sliding costs five years out (a prediction of course).

[Edit} The application is outdated though. You need to put in current electricity prices (have they gone down?) and current system costs.

Do they show the calcs? Too many of these sights just say it.

I highly doubt that $3.46 installed cost per watt has a reasonable payback in IL. Show me a calculation that would indicate that to be the case.

-ERD50

 

[meierlde]

Looking at the map and noting that the article dates from 2013 the numbers the chart shows for 2015 seem high. (for example a nearly doubling of the capacity per year in Tx). Running the numbers for my house in the hill country, it seems the payout is in the 20 year range. (Of course that very much depends on the price of natural gas, which controls the price of regular electricity in Tx , let it go back up to $13+ in 2006 to the mid two dollar range today). (Of course this is what is really killing coal fired power as well)

 

[ERD50]

Did a quick google search, this guy did an experiment.

Effect of Temperature on Solar Panels - Solar

30 degrees celsius vs. 75 degrees is a drop off of 40% in efficiency. So it depends on how hot the roof gets I guess.

It's more of an altitude factor though (high & sunny = still cool), not how close to the equator one is.

Sorry, very poorly controlled and amateurish 'experiment'. Doesn't tell us much of anything useful. How does this relate to a panel on a roof? What temperatures will that panel see in various environments (very different from just pushing it to a temperature and taking a reading).

At any rate, it's academic. If the efficiency is so much better at low temperatures, than we would see that reflected in the actual production numbers of solar PV installations in cold areas (or conversely, in very bad numbers in warm areas). But like I said, with shorter days and lower angles during a cold season, those efficiencies won't have much weighting on the annual numbers.

And don't forget that cold weather is often accompanied by snow. I've monitored a local large solar install, and the production dropped to near zero for a week at a time after a snowfall.

So let's see, plenty of sun, cold weather, long days, no snow... should be ideal. Where is that?

-ERD50

 

[jimnjana]

Do they show the calcs? Too many of these sights just say it.

I highly doubt that $3.46 installed cost per watt has a reasonable payback in IL. Show me a calculation that would indicate that to be the case.

-ERD50

Is the installed cost per watt still over $3 in IL?

 

[ERD50]

Is the installed cost per watt still over $3 in IL?

A recent large installation was $3.57/watt.

All flat roof (two large school buildings at different locations in the same town), lots of economy of scale. Far more cost efficient than sighting a single home.


896 Total kW $3,200,000 Installed $

-ERD50

 

[daylatedollarshort]

A 13 year payback is a 7.6% return on investment, so why not?

If you move out presumably your house has a bigger sale value then as well, since the new owners get a lower electricity bill.

I am not sure they necessarily would add value. They might be like backyard swimming pools, some people might want them and some might not:

Solar systems may not add to resale value of home | Las Vegas Review-Journal

Actually I just updated the calculator again with the correct roof slope direction and the payback time increased a few more years. Plus I am not sure the calculator adds in any upkeep costs. We'd have to have the panels removed and put back on when we replace the roof at minimum, so maybe a new roof needs to be done first. We have some other higher ROI house project to do first, so maybe if we get our kw needs lower and the panel prices come down a bit more it will be a better investment for us a few years out. Our water bill will probably be more than our energy bill this year, so getting the lawns out is more of a priority.

 

[retirementguy1]

While this isn't practical yet I think it will be a game changer in ten years. Imagine large skyscrapers with clear solar windows.


A fully transparent solar cell that could make every window and screen a power source | ExtremeTech


Unfortunately my home state of Nevada has a 3% cap for solar power. It seems like this is a protection for NVEnergy (Berkshire Hathaway). Most utilities have a monopoly because they are so heavily regulated.


Sandoval, NV Energy mum on net metering after meetings with solar officials - Las Vegas Sun News

 

[ampeep]

At the time we built out house, we installed a solar hot water system. 4 years later we put in a PV system that reduced our electric bill from $80 - $120 down to $16 - $50, depending on the season.

The federal & state tax credits made the payback period 3 - 4 years, otherwise it would have taken over 25 years.