The set up in Solar Disc is unusual for an IGT slot game - for starters, there are 6 reels instead of the standard 5. Those reels are set against a sun-kissed desert backdrop and include a selection of primitive objects and animals. You’ll see coins, keys, totem masks and a gem-encrusted chalice. The most valuable symbols are the bear and the big cat which pay 5 times your stake if you land 6 on the same payline.
Central to the action is the ornately designed solar disc symbol. When this lands, it will reveal a standard symbol. All instances of that symbol on the reels will then turn wild. Better still is if you’re lucky enough to see more than 1 solar disc on the same spin. This can turn multiple symbols wild with potentially spectacular results. This is known as the Solar Disc feature.
Hope to see the Bonus symbol on reel 1 and a solar disc on any other reel on the same spin as this triggers the Free Spins Bonus feature - you can then look forward to 10 free spins. You’re guaranteed to land at least 1 solar disc symbol on each of them so expect to see plenty of wilds throughout the round.
Solar flares and CMEs are the most powerful explosions in our solar system. This animation shows how coronal mass ejections can blow out from the Sun, interfere with Earth’s magnetic fields (the curved purple lines), and cause auroras (the blue rings of light circling the North and South poles). The warmth of the sun’s rays shine down upon you, gifting luminous rewards and magical adventure in Solar Disc online slot by IGT!This majestic game has 6-reels and 30-lines of slots action.
Solar Disc is a simple game but a rather innovative one. The transforming solar discs deliver plenty of action in both the base game and the Free Spins Bonus feature. Land multiple discs on the same free spin you could set off a wild explosion with payouts to match.
You might expect a slot game called Solar Disc to be red hot as far as volatility goes. That’s not quite the case here though. The variance is in the medium range and offers a balance between frequency and size of payouts – in fact, you can win 500 times your stake on every spin.
We’ve sometimes been a bit underwhelmed by what IGT has to offer. With its unusual extras, Solar Disc is certainly one of their better slot games. Get lucky with those transforming wilds and you’ll be beaming. If you want something more volatile, the mesmerising Electric Tiger should be played.
To get the most from solar panels, you need to point them in the direction that captures the most sun. But there are a number of variables in figuring out the best direction. This page is designed to help you find the best placement for your solar panels in your situation.
This advice applies to any type of panel that gets energy from the sun; photovoltaic, solar hot water, etc. We assume that the panel is fixed, or has a tilt that can be adjusted seasonally. (Panels that track the movement of the sun throughout the day can receive 10% (in winter) to 40% (in summer) more energy than fixed panels. This page doesn’t discuss tracking panels.)
Solar panels should always face true south if you are in the northern hemisphere, or true north if you are in the southern hemisphere. True north is not the same as magnetic north. If you are using a compass to orient your panels, you need to correct for the difference, which varies from place to place. Search the web for “magnetic declination” to find the correction for your location.
The next question is, at what angle from horizontal should the panels be tilted? Books and articles on solar energy often give the advice that the tilt should be equal to your latitude, plus 15 degrees in winter, or minus 15 degrees in summer. It turns out that you can do better than this - about 4% better.
It is simplest to mount your solar panels at a fixed tilt and just leave them there. But because the sun is higher in the summer and lower in the winter, you can capture more energy during the whole year by adjusting the tilt of the panels according to the season. The following table shows the effect of adjusting the angle, using a system at 40° latitude as an example. (The comparison would be a little different for different latitudes.) Each option is compared with the energy received by the best possible tracker that always keeps the panel pointed directly at the sun.
Fixed | Adj. 2 seasons | Adj. 4 seasons | 2-axis tracker | |
% of optimum | 71.1% | 75.2% | 75.7% | 100% |
In short, adjusting the tilt twice a year gives you a meaningful boost in energy. Adjusting four times a year produces only a little more, but could be important if you need to optimize production in spring and fall. You can jump to the section on the best fixed tilt angle, or skip to the sections on two-season or four-season adjusting.
The graph below shows the effect of adjusting the tilt. The turquoise line shows the amount of solar energy you would get each day if the panel is fixed at the full year angle. The red line shows how much you would get by adjusting the tilt four times a year as described below. For comparison, the green line shows the energy you would get from two-axis tracking, which always points the panel directly at the sun. (The violet line is the solar energy per day if the panel is fixed at the winter angle, discussed below.) These figures are calculated for 40° latitude.
If your solar panels will have a fixed tilt angle, and you want to get the most energy over the whole year, then this section is for you. A fixed angle is convenient, but note that there are some disadvantages. As mentioned above, you’ll get less power than if you adjusted the angle. Also, if you live where there is snow, adjusting the panels to a steeper angle in winter makes it more likely that they will shed snow. A panel covered in snow produces little or no power.
Use one of these formulas to find the best angle from the horizontal at which the panel should be tilted:
This table gives some examples for different latitudes. It also shows the average insolation on the panel over the year (in kWh/m2 per day), and the energy received compared to the best possible tracker.
Latitude | Full year angle | Avg. insolation on panel | % of optimum |
0° (Quito) | 0.0 | 6.5 | 72% |
5° (Bogotá) | 4.4 | 6.5 | 72% |
10° (Caracas) | 8.7 | 6.5 | 72% |
15° (Dakar) | 13.1 | 6.4 | 72% |
20° (Mérida) | 17.4 | 6.3 | 72% |
25° (Key West, Taipei) | 22.1 | 6.2 | 72% |
30° (Houston, Cairo) | 25.9 | 6.1 | 71% |
35° (Albuquerque, Tokyo) | 29.7 | 6.0 | 71% |
40° (Denver, Madrid) | 33.5 | 5.7 | 71% |
45° (Minneapolis, Milano) | 37.3 | 5.4 | 71% |
50° (Winnipeg, Prague) | 41.1 | 5.1 | 70% |
If you are going to adjust the tilt of your solar panels twice a year, and you want to get the most energy over the whole year, then this section is for you.
The following table gives the best dates on which to adjust:
Northern hemisphere | Southern hemisphere | |
Adjust to summer angle on | March 30 | September 29 |
Adjust to winter angle on | September 10 | March 12 |
If your latitude is between 25° and 50°, then the best tilt angle for summer is the latitude, times 0.93, minus 21 degrees. The best tilt angle for winter is the latitude, times 0.875, plus 19.2 degrees. If your latitude is outside this range, see Other Situations below. This table gives some examples:
Latitude | Summer angle | Winter angle | Avg. insolation on panel | % of optimum |
25° | 2.3 | 41.1 | 6.6 | 76% |
30° | 6.9 | 45.5 | 6.4 | 76% |
35° | 11.6 | 49.8 | 6.2 | 76% |
40° | 16.2 | 54.2 | 6.0 | 75% |
45° | 20.9 | 58.6 | 5.7 | 75% |
50° | 25.5 | 63.0 | 5.3 | 74% |
If you are going to adjust the tilt of your solar panels four times a year, and you want to get the most energy over the whole year, then this section is for you. This would be your situation if you are connected to the grid and can use or sell all the power you produce.
The following table gives the best dates on which to adjust:
Northern hemisphere | Southern hemisphere | |
Adjust to summer angle on | April 18 | October 18 |
Adjust to autumn angle on | August 22 | February 21 |
Adjust to winter angle on | October 5 | April 6 |
Adjust to spring angle on | March 5 | September 4 |
If your latitude is between 25° and 50°, then the best tilt angles are:
If your latitude is outside this range, see Other Situations below.
If you want to adjust the tilt of your panels four times a year, you can use these figures to keep capturing the most energy year-round. This table gives some examples:
Latitude | Summer angle | Spring/autumn angle | Winter angle |
25° | -1.3 | 22.2 | 46.3 |
30° | 3.3 | 27.1 | 50.7 |
35° | 7.9 | 32.0 | 55.2 |
40° | 12.5 | 36.9 | 59.6 |
45° | 17.1 | 41.8 | 64.1 |
50° | 21.7 | 46.7 | 68.5 |
In winter, a panel fixed at the winter angle will be relatively efficient, capturing 81 to 88 percent of the energy compared to optimum tracking. In the spring, summer, and autumn, the efficiency is lower (74-75% in spring/autumn, and 68-74% in summer), because in these seasons the sun travels a larger area of the sky, and a fixed panel can’t capture as much of it. These are the seasons in which tracking systems give the most benefit.
Note that the winter angle is about 5° steeper than what has been commonly recommended. The reason is that in the winter, most of the solar energy comes at midday, so the panel should be pointed almost directly at the sun at noon. The angle is fine-tuned to gather the most total energy throughout the day.
The summer angles are about 12 degrees flatter than is usually recommended. In fact, at 25° latitude in summer, the panel should actually be tilted slightly away from the equator.
If your need for energy is highest in the winter, or the same throughout the year, you may want to just leave the tilt at the winter setting. This could be the case if, for instance, you are using passive solar to heat a greenhouse. Although you could get more energy during other seasons by adjusting the tilt, you will get enough energy without making any adjustment. The following tables assume that the tilt is set at the winter optimum all year long. They show the amount of insolation (in kWh/m2) on the panel each day, averaged over the season.
Season | Insolation on panel | % of winter insolation |
Winter | 5.6 | 100% |
Spring, Autumn | 6.0 | 107% |
Summer | 5.1 | 91% |
Season | Insolation on panel | % of winter insolation |
Winter | 4.7 | 100% |
Spring, Autumn | 5.8 | 123% |
Summer | 5.1 | 109% |
Season | Insolation on panel | % of winter insolation |
Winter | 3.4 | 100% |
Spring, Autumn | 5.4 | 158% |
Summer | 5.1 | 150% |
Perhaps your panels are on a roof that is not oriented exactly to the south. Or you are at a latitude outside the range for which these formulas work. These situations are more complex than can be handled by a simple formula.
I can do calculations for your custom situation for a consulting fee. See my rates.You may need to make adjustments for your situation. For example, if you have trees to the east but not the west, it may be better for you to aim your solar panels slightly to the west. Or if you often have clouds in the afternoon but not the morning, you might aim your panels slightly to the east.
The calculations also assume that you are near sea level. At very high altitude, the optimum angle could be a little different.
If you are estimating energy output, remember that temperature affects the efficiency of photovoltaic panels. They produce less power at higher temperatures. Panels vary so you will need to contact your panel manufacturer for their specifications.
Don’t obsess about the exact angles just because I’ve calculated them to the tenth of a degree. A difference of a few degrees will make very little difference in the energy you gather.
The recommended angles can seem counterintuitive. For example, consider summer at 40° latitude. At noon on the solstice, the sun is 40° - 23.5° which is 16.5° from directly overhead. To capture the most sun at that time you would tilt the panel 16.5° to point it directly at the sun. On other days of the summer it is a bit lower in the sky, so you would want to tilt the panel a bit more. Yet we say to tilt it only 12.5°. The sun is never that high. How can that be right?
The answer is that we are considering the whole day, not just noon. In the morning and evening, the sun moves lower in the sky and also further north (if you are in the northern hemisphere). It is necessary to tilt less to the south (or more to the north) to collect that sunlight.
intensity in kw/m2 = 1.35 * (1.00/1.35) sec(angle of sun from zenith)
This formula assumes that the earth is flat, so a factor was applied to account for the curvature of the earth (and therefore the earth’s atmosphere). These factors, and the angle of the sun with respect to the panel, then determine the insolation on the panel. An iterative method then determined the angles that give the maximum total insolation during each season. Given those angles, the beginning and ending dates of the season were then adjusted to the optimum, then the angles recalculated, until the process converged. After the optimum dates and angles were calculated, it was determined that a linear formula closely approximates the optimum. The formulas are only accurate within the specified range.
Other published articles on tilt angles have used less accurate calculations. For example, Richard Perez and Sam Coleman, in “PV Module Angles”, Home Power n.34 p.14-16, 1993, recommend an angle that puts the panel perpendicular to the sun’s rays at noon. That is indeed the best angle at noon on that day, but it does not take into account the best angle for capturing solar energy at other times of the day. That article also leaves it to the reader to estimate the best angle over the period until the next time the tilt is adjusted.
Percentages may not be exact due to rounding.
This page was last updated on 18 March 2017.
Written by Charles R. Landau. Copyright © 2001, 2002, 2008, 2010-2012, 2014-2015, 2017. All rights reserved.