Slashdot Mirror
You're Doing It All Wrong: Solar Panels Should Face West, Not South
HughPickens.com writes In the U.S., a new solar project is installed every 3.2 minutes and the number of cumulative installations now stands at more than 500,000. For years, homeowners who bought solar panels were advised to mount them on the roof facing south to capture the most solar energy over the course of the day. Now Matthew L. Wald writes in the NYT that panels should be pointed west so that peak power comes in the afternoon when the electricity is more valuable. In late afternoon, homeowners are more likely to watch TV, turn on the lights or run the dishwasher. Electricity prices are also higher at that period of peak demand. "The predominance of south-facing panels may reflect a severe misalignment in energy supply and demand," say the authors of the study, Barry Fischer and Ben Harack. Pointing panels to the west means that in the hour beginning at 5 p.m., they produce 55 percent of their peak output. But point them to the south to maximize total output, and when the electric grid needs it most, they are producing only 15 percent of peak.
While some solar panel owners are paid time-of-use rates and are compensated by the utility in proportion to prices on the wholesale electric grid, many panel owners cannot take advantage of the higher value of electricity at peak hours because they are paid a flat rate, so the payment system creates an incentive for the homeowner to do the wrong thing. The California Energy Commission recently announced a bonus of up to $500 for new installations that point west. "We are hoping to squeeze more energy out of the afternoon daylight hours when electricity demand is highest," says David Hochschild, lead commissioner for the agency's renewable energy division, which will be administering the program. "By encouraging west-facing solar systems, we can better match our renewable supply with energy demand."
Obviously the panels should be motorized so that they are always facing the most optimal direction. A system that moves the panels shouldn't add that much to the cost and will probably pay for itself very quickly with the extra energy collected.
Obviously the article covers this...
Solar panels do not have to be pointed in just one direction; a homeowner can buy a device called a tracker that will pivot them, over the course of the day, like a sunflower, so they always face the sun. A tracker can raise the output of a panel by 45 percent. But adding trackers can cost hundreds or thousands of dollars, and a cheaper way to get the same number of kilowatt-hours may be simply to buy a few extra panels.
The point is, while he may be a special little snowflake, so is everyone else. What TFA really says is "Those who run the electrical grid get the most out of solar panels that are pointed west in California, as this has them pointing directly at the sun during peak electrical grid demand." That's significantly different than "Solar panels should face west."
If you're off-grid, you'll do best with pointing to the optimal location (there are charts available for this -- it's rarely south OR west) and storing the energy harvested for use when you need it. If you're just pumping it into the local grid, optimizing for high demand periods makes more sense (and the charts aren't tuned for that [yet]). However, this assumes that the electrical service you're using allows you to contribute back to the grid, and has a variable pricing scheme. If they don't, what real incentive do you have to optimize your energy collection to when THEY need it most? You'd have more incentive to tune for peak efficiency and sell it back to them when you don't need it -- and then buy back at the same rate when you DO need it.
So this whole thing's kind of a non-issue. Of course, what works best, as long as you're generating a decent amount of electricity, is to just track the sun from sunrise to sunset, assuming you'll offset the costs of the sensors and motors.
An important aspect the author overlooks is that many residential customers prefer aesthetics over optimization, and therefore the panels are often mounted as closely in parallel with the plane of the roof as practical. It is one of the reasons residential based solar, on average, will always trail centrally based, larger scale solar in capacity factor. Centrally based solar installations are optimized for their location. (OTOH, residential power delivery suffers lower transmission/distribution line loss factors than centrally located, but that is a bit off topic)
/. before. Existing incentives drive installations that are optimal from a total MWH generation standpoint over those that lengthen the generation window. These incentives pretty much take tracking mechanisms out of play in favor of adding more panels for the same cost.
The point regarding the incentives simply being for total production & not considering time is true, its one I’ve made here on
If the goal is clean air generation per $ invested, then generating less just to lengthen the window doesn’t make much sense. It is an energy cost increase on an already costly energy source. This guy is proposing that the government spend even more on incentives for installations that will produce less power overall. Given the existing infrastructure and the fact that other sources will continue to fill in the demand profile when renewables can’t, the proposed changes don’t seem to accomplish much other that increase cost.
hedge your bets and go 50/50 south and west. Maybe 50% southwest, 25% west, 25% south and setup a water wheel and perhaps an agrarian society.
Lattitude matters too. Where I live, it's dark at 5PM. West-pointing would be a bit silly. Of course, it's a different story in Summer. A home fission plant sounds much more reliable to me! It'll really reduce my lighting costs when I glow in the dark.
Socialism: a lie told by totalitarians and believed by fools.
I just purchased a solar panel system for our home, and I've been learning a lot about all of this stuff during the process.
The problem with the author's suggestion is that he's concerned about a problem that, by and large, we haven't quite come to yet. Solar adoption is still such a small percentage of the total number of electric consumers that the "saturation point" hasn't usually been reached yet. The entire "net metering" model for solar isn't really sustainable if you get more than a single digit percentage of homeowners in a given area going solar. I think that will hold true EVEN if you could convince all the new solar installations to use west-facing panels to time shift their power production hours.
Right now, practically everything about PV solar adoption centers around government regulations creating an "artificial" incentive for it. For example, in my home state of Maryland and a number of others, they have an SREC program in place (solar reclamation credits). How does it work? Basically, they made a rule that the state's utility companies have to obtain a certain percentage of their electricity generation via "Green" sources like wind or solar. If they fail to hit that target, they must purchase these SREC certificates in a sufficient quantity to offset it. (In reality, they're always going to pay for the SRECs rather than adopt more alternative energy generation themselves -- because for them, it's still the more cost-effective and sensible option. They don't want to spend a bunch on new infrastructure and land to place it on, just to meet those percentage targets.) For every megawatt of solar power your home solar panel setup produces, you earn an SREC which you can turn around and resell to the power company (directly, or via one of several auction web sites designed for the purpose). There's even one offering to buy 10 or 20 years' worth of your SRECs in advance, at some discounted price, giving you more "up front" cash to pay off your system's initial installation cost - should you find that the best option.
Don't forget the Federal tax credit of 30% of whatever you spent to buy the solar panel system, and states like mine who kick in another $1,000 or so. This stuff just doesn't make the same financial sense with all of these constructs removed from the equation.
The real elephant in the room that everyone's ignoring is the fact that power DISTRIBUTION is the limiting factor for the power companies. As soon as too many people start putting power from solar back onto the grid at one time, in one area? They can't really do anything with it, so it gets wasted. Yet the "net metering" rules require that pay you back for it anyway, at full retail prices. For a SHORT time, you might be able to postpone this by switching more panels to face west instead of south, but soon enough - it will become a problem again.
Honestly, I predict that what we'll see playing out is government withdrawing all of the tax breaks, followed by the value of your SRECs dropping to very little as they ease up on the requirements the utilities must meet. This will put the brakes on solar adoption, making it one of those things that only paid off for the people who got in on it early - or who have a situation where it STILL pays off (due to especially high power costs). In Hawaii or parts of California, for example, I believe the utilities sometimes bill as high as 90-some cents per kilowatt-hour used. In Maryland, by contrast? I pay closer to 11 cents.
hedge your bets and go 50/50 south and west. Maybe 50% southwest, 25% west, 25% south and setup a water wheel and perhaps an agrarian society.
The direction you point it depends on where in the world you are. Further north you are the more you want it pointed south rather than west. In any case, while the $/watt calculation may be higher for capturing the western sun you'll lose a LOT of watts by pointing west (esp further north).
What most people don't know about solar panels is that their efficiency goes up the cooler they are. We make more money in winter on our solar projects despite the reduction in hours/intensity of the sun simply because it's usually -10C or lower where we have our installations.
One option that might be financially viable is to point south but store it in small salt-water geo-sinks to pump into the grid during peak times. Otherwise, I can guarantee that you'll be further ahead pointing south rather than west unless you're in Texas or some other hot/southern climate.
Any time you move the panels out of close contact with the roof, you're accepting large wind loads. That means the supporting structure -- especially if it's movable -- has to be substantially sturdier.
The optimal position of solar panels depends on several factors:
Tracking mechanisms work, but they are mechanical and can fail, and they cost money. It may be cheaper to add panels than to add trackers. For seasonal adjustment, some mounting hardware allows relatively easy manual adjustment of the slope.You don't have to change this but a few times a year.
I have been off the grid at home for ten years, depending mostly on solar but with a little wind. Our panels are pointed in three directions: Southeast to get power in the early morning when the batteries are lowest, south for use during peak sun, and southwest to end the daylight hours with fully charged batteries. We have home-made mounting, and it was cheaper to add a few extra panels than to add tracking hardware.
I'm installing solar neutrino panels, and facing them down. That way I can get power at night when I really need it.
Obviously the article covers this...
What article?
That is not how trackers work. Most trackers simply operate by relative gas expansion. The sun heats one side of the horitontal tube/bag more than the other due to position, and that causes the tracker to push the panel in the right direction. No motor, no eye, almost no moving parts. Not at all over engineered
hedge your bets and go 50/50 south and west. Maybe 50% southwest, 25% west, 25% south and setup a water wheel and perhaps an agrarian society.
You're talking nonsense, obviously. Most people watch tv in the night, when the sun is on the other side of the planet, so the panels should actually face down. I would have thought that was obvious.