Energy 101, we've been talking about the natural resources that we have to drive
our energy system and we've been, been talking essentially about fossil fuels,
coal, natural gas, oil and, so let's, let's look at some renewables like solar.
Today we're going to want to look at solar energy resources.
it's a new ball game when you start talking about solar and wind and, as
renewable resources because with coal and oil and gas and that kind of fossil fuel
is very convenient, you can just fire up your, your plant, whatever you're fueling
with those. Fuels.
And crank 'em up and run 'em wide open. You control the throttle, so to speak.
You can run 'em wide open, you can let 'em idle.
You can, just like your car. And you have total control.
That's what we call dispatchable in the electric utility industry.
But in, whether it's your, your home furnace, you can turn Turn it up and down
and keep your home just the right temperature, but when you have solar and
wind, the sun doesn't shine so brightly all the time, and the wind doesn't blow
strongly all the time. So it's, we have to make sure that our,
the way we use these renewable energy systems can accommodate that up and down
resource. And that it comes and goes.
In the case of solar, of course, it The sun only shines on the average of about
12 dollars a day. And doesn't shine any at night.
So that's the problem right there. and then you have clouds.
But the, how much solar energy is there available? We're looking at it as a
resource here. That the striking the Earth.
That we can figure out, so we can figure out how much there is.
And then we can determine. How to use that energy to strike in the
earth. But, there's about 300, at noon on a
clear day, so if you've got no clouds, it's a nice bright shiny day.
And at noon, and the reason it has to be at noon is because that's When the
distance that the sun has to travel through the earth's atmosphere is the
shortest, you can imagine when it's over at an angle, in ea, early morning or
late, it's shining at an angle ,uh, on you through a longer distance of
atmosphere gases. And, that attenuates the sun somewhat so
it's always brightest at noon, assuming there no clouds, because that's when the
Path link through the, the, the atmosphere is the shortest.
So, we, at noon and on a clear day with no clouds and low, low water moisture, if
you look directly at the sun and point a surface.
Direct one square foot pointed directly at the surface, so that it's
perpendicular to the surface, to the sun rays.
You'll get about 300 BTUs per hour falling on that one square foot.
Or in metric units, is one kilowatt per square meter.
And they're about 10 square feet in a square meter.
So there's about a tenth of a kilowatt per square foot.
If you want in kilowatt units or 300 BTU's per hour.
Falling on 1 square foot. So that's, that's the best you can do at,
at noon on a clear day. But now it's decreased by clouds and the
angle from early morning to late afternoon.
So life gets complicated whereas when we're trying to calculate even how much
solar energy is available as a resource. But the good thing is it's free.
We don't have to pay anybody for it. Like we do, fossil fuels in particular.
Affordable tax is, really come on the forefront with, dropping costs in the
last couple of years. And this is just showing 1 installation
on a house roof fairly that's fairly typical on a house.
When I say typical, it's a typical good one.
The house is obviously, and, looks like design 4.
the collectors, the house was oriented so it's facing south.
And, and the angle of the roof was such that it collects the most energy
sunlight, over a year. so, the, thee, this, the best angle.
The tilt, because the sun, and, depending on the time of year, is either high in
the sky, or low in the southerly direction, if you're in the Northern
Hemisphere. But the, ee, for the best annual solar
resource falling on your collectors, you want to face the collectors due south,
and you want to tilt them up from the horizontal Of, a, the, the, number
degrees equal to your latitude. In Atlanta, where I am, the, our latitude
is 35 degrees, so to get the most solar energy falling on a flat fixed surface,
we tilt the, the collectors in the southernly direction.
35 degrees, of course on the equator a horizontal collector will collect the
most sunlight over a year, and this is on an annual basis.
If you're trying to optimize it for January and you don't care about the
summertime, then the angles are different.
If you wanted. Optimize in July, then the angles are
different. But over the annual average, the latitude
and the geometry that shows that, the geom, the best geometry is to have it
tilted from the horizontal in the southerly direction.
And, of course, the other limitation. You can't have any trees.
Here in Atlanta, most of our residential areas were blessed with a lot of trees in
one way. But then, you get a lot of shading.
And, so, how, where you can use solar energy depends on the site, the location,
and the orient, the orientation of the house.
another way we utilize solar energy is what we call solar power tower.
There's several ways. I'm just pointing out the two big ones
that we'll talk about now that's expanding commercially and fairly
rapidly. And in this case You've got thousands of
mirrors that you see down there. This is made from an airplane looking
down on this circle that's probably 1/4 to 1/2 a mile in diamater.
So it's a large large installation and it produces electricity and of course the
photovoltaic cell produces electricity. The sun shines directly on them and the
solid state device has wires running to it, it produces electricity from that.
in this case, the sun is reflected by these mirrors.
That each 1 of these little dots are mirror's, on the surface of the earth.
And they track, they have 2 access tracking we call them.
You can orient them in any direction you want to.
So a computer program makes those mir, mirrors track, so the sun light falling
on their mirror, Is reflected off of that mirror on to the top of this tower.
And on the top of this tower there's a boiler, a steam boiler, just like in a
steam power plant fueled by coal there's, a boiler and a hot Fire oil sustained in
this case all the sunlight that is reflected onto this boiler heats the
boiler up to very high temperatures and boils the steam.
So this is one that you've seen built and several of them being built right now as
a matter of fact out in California in the Mojave desert and Arizona and those
places. The first ones were built back in the
80's. Technology has been around for a while.
So for large scale solar, this is a pretty cost effective way to produce
electric power. But again, it produces electric power
from a conventional steam power plant cycle.
But it's using The sun to heat up and boil the steam that's reflected from
these thousands of mirrors rather than a fire that's burning fossil fuels.
so, how much, how can we calculate how much energy strikes a solar collector
surface? Well, as I mentioned, it varies, varies by day of the year because that's
dependent on where the sun is in the sky. And but let's look at the annual average.
Energy per day falling on a fixed collector tilted south.
Now this includes weather situations cloudy days, rainy days, night of course.
And so it's the average and it varies by geographical location.
And it also varies by your solar collector orientation and your tracking
mat, method. if you have Two Axis Tracking, where it's
always looking directly at the sun, well, that's the best.
if you have a Fixed Plate Tilted South At the Latitude, which we've just been
discussing, that's another option, or you can, sometimes you may only have a Flat
Horizontal surface or you want to put them on the side of a building, and it's
only a vertical surface. [UNKNOWN] In our, energy building, the
carbon neutral energy solutions building that we just built here at Georgia Tech,
it has some constant, some photovoltaic collectors on the horizontal awning
surface as well as on the vertical surface as well as on the roof tilted
south so it's got collectors mounted on one new building with 3 different
orientations. But, so, how much energy Solar energy
falls on a square foot or a square meter on an average day throughout the year is,
can be calculated, and it depends on where you are, in the U.S.
You can see here, that, over here in Arizona and New Mexico, you get the, the
maximum. Solar energy falling.
And over in [INAUDIBLE] in Florida and in the northwest, you get less solar energy
falling. And,
So, that's a, Excuse me.
yeah. And.
There's a scale here, the maximum we get is about 7 kilowatt hours per day on
average for the year, 7 kilowatt hours per year out here in, Arizona,
California, New Mexico. and when you move to the lighter yellow
areas Then it goes down to the minimum in the US.
Like, up here in the north, you get about 4.
So, there's almost a factor of 2 difference in the amount of solar energy
falling on these collectors. depending on where you are in the US.
And notice, it says at the top. This is, annual in the right, upper right
hand corner. So that's the annual average.
It's also the. Flat plate, tilted south at the latitude.
So it's not tracking, it's fixed. But it's as majority of the collectors
and the solar system installations are mounted in exactly this manner, tilted to
the south at the latitude they're fixed. Well, how might we calculated.
We can actually calculate this for your, your, or, your location.
and by going to a US Department of Energy National Renewable Energy Laboratory
called NREL. out in Golden, Colorado, and, it's a
laboratory of the US Department of Energy, and they've got an interactive
on-line map. So let's go to this, interactive on-line
map The web address is as you see on the, on the, in the blue here.
http it's a long, long one. Hopefully you can click on it and it will
take you there. You can copy and paste it into your
browser. So I have my browser up here.
At that location, and this is the first page.
U.S. Solar Radiation Resource Maps.
So you probably want to stop your video and pull this page up at this point, and
then come back. And we'll walk through how to use this to
calculate, whatever situation and orientation and geographical location you
might be. Be interested in.
The first thing you can do is you can, select the data type.
You can select average, which is noted there right now.
You can, select the minimum or you can select the maximum, for the day.
The maximum for the day or minimum for the day on, on the average.
You can, you can look at the The, selected by the month.
You can pick one month, January through December, or you can pick the annual
average. You notice for this chart that I had up
and the previous slide. I had selected, as I mentioned to you,
the average, annual average, and I picked, and, and, and I wanted to see the
annual and not the minimum or maximum for a particular day.
and now you can select the orientations, they have a lot of orientations, more
than I mentioned to you. you have single axis tracking
concentrator. This is just tracking one axis rather
than two axis, which of course is cheaper but is more, than two axis.
More expensive than a fixed collector. And so, there, there's several Single
Axis Tracking options here, and you got two Axis Tracking Flat Plate right here,
that always will make the collector look at the sun, but of course, it's got to be
mounted on a, on a tracking device. It's got electric motors that's
controlled by computers, that always keeps it looking flat, straight at the
sun. And, you can do the 1 that I, that most,
most installations are using. A flat plate [INAUDIBLE] tilted south at
the latitude. And that's the 1 that I had selected to
generate the map that I just showed you before.
you can pick the horizontal flat plate down here.
Horizontal flat plate that if you've got a horizontal surface and that's all you
got and it's the cheapest way to install them, then you could look and see the
penalty for mounting them horizontally versus tilting them southern, south at
the latitude angle. Of course, if the equator, the horizontal
is also the optimum. you can look at the south facing vertical
plate, flat plate, on the south facing wall.
north south access tracking they got alot of options here.
I won't bother to go through them. But if you look at the horizontal flat
plate I'll pick something different. On this one, and the map that I showed
you earlier, and you go down here then and you just make those three selections
and click view map and now you, you get this map and you get a
as you see there. And, you get the kill it down here, you
get the kilowatt hours per day. It, it runs from 10 to 14 kWh/m^2/day.
The color was none of this on there, all the way down to the darker blue, which is
0 to 2. And of course, again, the Southwest,
which is where you see a lot of installations is the best, and then as
you move north in this situation, they, you're getting further away from the
equator where the horizontal is optimum and you collect less and less energy or
you, less of the, the solar energy strikes the surface So that's a, that's a
nice interactive web site so you can look at your situation and look at any kind of
tracking option or mounting option that you might be interested in.
Thank you.