[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.51,0:00:09.32,Default,,0000,0000,0000,,We have some good reasons to completely
Dialogue: 0,0:00:09.32,0:00:11.24,Default,,0000,0000,0000,,switch over to solar power.
Dialogue: 0,0:00:11.24,0:00:12.86,Default,,0000,0000,0000,,It's cheaper in many cases,
Dialogue: 0,0:00:12.86,0:00:14.81,Default,,0000,0000,0000,,and definitely more sustainable
Dialogue: 0,0:00:14.81,0:00:17.21,Default,,0000,0000,0000,,than our dependance on traditional power plants
Dialogue: 0,0:00:17.21,0:00:18.91,Default,,0000,0000,0000,,that use resources like coal,
Dialogue: 0,0:00:18.91,0:00:20.95,Default,,0000,0000,0000,,which will eventually run out.
Dialogue: 0,0:00:20.95,0:00:22.04,Default,,0000,0000,0000,,So why don't we replace these
Dialogue: 0,0:00:22.04,0:00:24.57,Default,,0000,0000,0000,,traditional plants with solar energy?
Dialogue: 0,0:00:24.57,0:00:26.03,Default,,0000,0000,0000,,Because there's one factor that makes
Dialogue: 0,0:00:26.03,0:00:28.48,Default,,0000,0000,0000,,solar power very unpredictable:
Dialogue: 0,0:00:28.48,0:00:30.05,Default,,0000,0000,0000,,cloud cover.
Dialogue: 0,0:00:30.05,0:00:32.22,Default,,0000,0000,0000,,As the sun's rays move towards Earth,
Dialogue: 0,0:00:32.22,0:00:34.65,Default,,0000,0000,0000,,some get absorbed by the Earth's atmosphere,
Dialogue: 0,0:00:34.65,0:00:36.76,Default,,0000,0000,0000,,some are reflected back into outer space,
Dialogue: 0,0:00:36.76,0:00:39.89,Default,,0000,0000,0000,,but the rest make it to the Earth's surface.
Dialogue: 0,0:00:39.89,0:00:41.44,Default,,0000,0000,0000,,The ones that aren't deviated
Dialogue: 0,0:00:41.44,0:00:43.52,Default,,0000,0000,0000,,are called direct irradiance.
Dialogue: 0,0:00:43.52,0:00:45.36,Default,,0000,0000,0000,,The ones that are deflected by clouds
Dialogue: 0,0:00:45.36,0:00:47.66,Default,,0000,0000,0000,,are called diffuse irradiance.
Dialogue: 0,0:00:47.66,0:00:50.51,Default,,0000,0000,0000,,And those rays that first get reflected by a surface,
Dialogue: 0,0:00:50.51,0:00:51.78,Default,,0000,0000,0000,,like a nearby building,
Dialogue: 0,0:00:51.78,0:00:54.38,Default,,0000,0000,0000,,before reaching the solar energy system
Dialogue: 0,0:00:54.38,0:00:56.61,Default,,0000,0000,0000,,are called reflected irradiance.
Dialogue: 0,0:00:56.61,0:00:58.26,Default,,0000,0000,0000,,But before we can examine how clouds
Dialogue: 0,0:00:58.26,0:01:01.28,Default,,0000,0000,0000,,affect the sun's rays and electricity production,
Dialogue: 0,0:01:01.28,0:01:04.50,Default,,0000,0000,0000,,let's see how these solar energy systems work.
Dialogue: 0,0:01:04.50,0:01:06.87,Default,,0000,0000,0000,,First up, we have solar towers.
Dialogue: 0,0:01:06.87,0:01:08.41,Default,,0000,0000,0000,,These are made up of a central tower
Dialogue: 0,0:01:08.41,0:01:11.12,Default,,0000,0000,0000,,surrounded by a huge field of mirrors
Dialogue: 0,0:01:11.12,0:01:13.03,Default,,0000,0000,0000,,that track the sun's path and focus
Dialogue: 0,0:01:13.03,0:01:16.65,Default,,0000,0000,0000,,only the direct rays onto a single point on the tower,
Dialogue: 0,0:01:16.65,0:01:19.43,Default,,0000,0000,0000,,kind of like an eager beachgoer.
Dialogue: 0,0:01:19.43,0:01:21.13,Default,,0000,0000,0000,,The heat generated by these rays
Dialogue: 0,0:01:21.13,0:01:24.71,Default,,0000,0000,0000,,is so immense that it can be used to boil water
Dialogue: 0,0:01:24.71,0:01:27.72,Default,,0000,0000,0000,,producing steam that drives a traditional turbine,
Dialogue: 0,0:01:27.72,0:01:29.54,Default,,0000,0000,0000,,which makes electricity.
Dialogue: 0,0:01:29.54,0:01:31.52,Default,,0000,0000,0000,,But when we say solar energy systems,
Dialogue: 0,0:01:31.52,0:01:34.25,Default,,0000,0000,0000,,we're usually talking about photovoltaics,
Dialogue: 0,0:01:34.25,0:01:35.70,Default,,0000,0000,0000,,or solar panels,
Dialogue: 0,0:01:35.70,0:01:37.32,Default,,0000,0000,0000,,which are the systems most commonly used
Dialogue: 0,0:01:37.32,0:01:38.94,Default,,0000,0000,0000,,to generate solar power.
Dialogue: 0,0:01:38.94,0:01:39.92,Default,,0000,0000,0000,,In solar panels,
Dialogue: 0,0:01:39.92,0:01:42.80,Default,,0000,0000,0000,,photons from the sun's rays hit the surface of a panel,
Dialogue: 0,0:01:42.80,0:01:44.46,Default,,0000,0000,0000,,and electrons are released
Dialogue: 0,0:01:44.46,0:01:46.82,Default,,0000,0000,0000,,to get an electric current going.
Dialogue: 0,0:01:46.82,0:01:49.82,Default,,0000,0000,0000,,Solar panels can use all types of irradiance,
Dialogue: 0,0:01:49.82,0:01:53.56,Default,,0000,0000,0000,,while solar towers can only use direct irradiance,
Dialogue: 0,0:01:53.56,0:01:56.22,Default,,0000,0000,0000,,and this is where clouds become important
Dialogue: 0,0:01:56.22,0:01:58.29,Default,,0000,0000,0000,,because depending on their type and location
Dialogue: 0,0:01:58.29,0:01:59.54,Default,,0000,0000,0000,,relative to the sun,
Dialogue: 0,0:01:59.54,0:02:01.64,Default,,0000,0000,0000,,they can either increase or decrease
Dialogue: 0,0:02:01.64,0:02:04.12,Default,,0000,0000,0000,,the amount of electricity produced.
Dialogue: 0,0:02:04.12,0:02:06.24,Default,,0000,0000,0000,,For instance, even a few cumulus clouds
Dialogue: 0,0:02:06.24,0:02:07.69,Default,,0000,0000,0000,,in front of the sun can reduce
Dialogue: 0,0:02:07.69,0:02:10.04,Default,,0000,0000,0000,,the electricity production in solar towers
Dialogue: 0,0:02:10.04,0:02:14.46,Default,,0000,0000,0000,,to almost zero because of this dependence on direct rays.
Dialogue: 0,0:02:14.46,0:02:16.69,Default,,0000,0000,0000,,In solar panels, those clouds would decrease
Dialogue: 0,0:02:16.69,0:02:18.20,Default,,0000,0000,0000,,energy output as well,
Dialogue: 0,0:02:18.20,0:02:19.44,Default,,0000,0000,0000,,though not as much
Dialogue: 0,0:02:19.44,0:02:22.71,Default,,0000,0000,0000,,because solar panels can use all types of irradiance.
Dialogue: 0,0:02:22.71,0:02:26.16,Default,,0000,0000,0000,,However, all this depends on the clouds exact positioning.
Dialogue: 0,0:02:26.16,0:02:28.47,Default,,0000,0000,0000,,Due to reflection, or a particular phenomeon
Dialogue: 0,0:02:28.47,0:02:30.34,Default,,0000,0000,0000,,called Mie scattering,
Dialogue: 0,0:02:30.34,0:02:33.12,Default,,0000,0000,0000,,the sun's rays can actually be focused forward
Dialogue: 0,0:02:33.12,0:02:36.57,Default,,0000,0000,0000,,by clouds to create a more than 50% increase
Dialogue: 0,0:02:36.57,0:02:39.68,Default,,0000,0000,0000,,in the solar irradiance reaching a solar panel.
Dialogue: 0,0:02:39.68,0:02:42.23,Default,,0000,0000,0000,,If this potential increase isn't accounted for,
Dialogue: 0,0:02:42.23,0:02:44.78,Default,,0000,0000,0000,,it could damage the solar panel.
Dialogue: 0,0:02:44.78,0:02:45.90,Default,,0000,0000,0000,,Why does this matter?
Dialogue: 0,0:02:45.90,0:02:47.73,Default,,0000,0000,0000,,Well, you wouldn't want this lesson to stop
Dialogue: 0,0:02:47.73,0:02:51.13,Default,,0000,0000,0000,,just because a cloud passed over the panel on your roof.
Dialogue: 0,0:02:51.13,0:02:54.43,Default,,0000,0000,0000,,In solar towers, huge tanks of molten salt or oil
Dialogue: 0,0:02:54.43,0:02:56.81,Default,,0000,0000,0000,,can be used to store any excess heat
Dialogue: 0,0:02:56.81,0:02:58.29,Default,,0000,0000,0000,,and use it when needed,
Dialogue: 0,0:02:58.29,0:02:59.74,Default,,0000,0000,0000,,so that's how they manage the problem
Dialogue: 0,0:02:59.74,0:03:02.52,Default,,0000,0000,0000,,of fluctuating solar irradiance to smooth out
Dialogue: 0,0:03:02.52,0:03:03.100,Default,,0000,0000,0000,,electricity production.
Dialogue: 0,0:03:03.100,0:03:05.34,Default,,0000,0000,0000,,But in the case of solar panels,
Dialogue: 0,0:03:05.34,0:03:07.90,Default,,0000,0000,0000,,there currently isn't any way to affordably
Dialogue: 0,0:03:07.90,0:03:09.73,Default,,0000,0000,0000,,store extra energy.
Dialogue: 0,0:03:09.73,0:03:11.72,Default,,0000,0000,0000,,That's where traditional power plants come in
Dialogue: 0,0:03:11.72,0:03:13.84,Default,,0000,0000,0000,,because to correct for any fluctuations
Dialogue: 0,0:03:13.84,0:03:15.82,Default,,0000,0000,0000,,in these solar powered plants,
Dialogue: 0,0:03:15.82,0:03:18.15,Default,,0000,0000,0000,,extra electricity from traditional sources
Dialogue: 0,0:03:18.15,0:03:20.43,Default,,0000,0000,0000,,always needs to be available.
Dialogue: 0,0:03:20.43,0:03:22.87,Default,,0000,0000,0000,,But then why aren't these tradtional power plants
Dialogue: 0,0:03:22.87,0:03:24.34,Default,,0000,0000,0000,,just used as a backup,
Dialogue: 0,0:03:24.34,0:03:26.08,Default,,0000,0000,0000,,instead of us humans depending on them
Dialogue: 0,0:03:26.08,0:03:28.30,Default,,0000,0000,0000,,as our main sources of energy?
Dialogue: 0,0:03:28.30,0:03:30.11,Default,,0000,0000,0000,,Because it's impossible for an employee
Dialogue: 0,0:03:30.11,0:03:32.25,Default,,0000,0000,0000,,at a coal fired or a nuclear plant
Dialogue: 0,0:03:32.25,0:03:33.51,Default,,0000,0000,0000,,to turn a knob to produce
Dialogue: 0,0:03:33.51,0:03:35.43,Default,,0000,0000,0000,,more or less electricity depending
Dialogue: 0,0:03:35.43,0:03:37.83,Default,,0000,0000,0000,,on how many clouds there are in the sky.
Dialogue: 0,0:03:37.83,0:03:40.52,Default,,0000,0000,0000,,The response time would simply be too slow.
Dialogue: 0,0:03:40.52,0:03:42.82,Default,,0000,0000,0000,,Instead, to accommodate these fluctuations,
Dialogue: 0,0:03:42.82,0:03:45.72,Default,,0000,0000,0000,,some extra electricity from traditional power plants
Dialogue: 0,0:03:45.72,0:03:48.04,Default,,0000,0000,0000,,is always being produced.
Dialogue: 0,0:03:48.04,0:03:49.50,Default,,0000,0000,0000,,On clear sky days,
Dialogue: 0,0:03:49.50,0:03:51.58,Default,,0000,0000,0000,,that extra electricity might be wasted,
Dialogue: 0,0:03:51.58,0:03:53.56,Default,,0000,0000,0000,,but when cloudy skies prevail,
Dialogue: 0,0:03:53.56,0:03:55.47,Default,,0000,0000,0000,,it's what fills the gap.
Dialogue: 0,0:03:55.47,0:03:56.93,Default,,0000,0000,0000,,This is what we currently depend on
Dialogue: 0,0:03:56.93,0:03:58.86,Default,,0000,0000,0000,,for a constant supply of energy.
Dialogue: 0,0:03:58.86,0:04:00.19,Default,,0000,0000,0000,,For this reason, a lot of researchers
Dialogue: 0,0:04:00.19,0:04:02.63,Default,,0000,0000,0000,,are interested in forcasting the motion
Dialogue: 0,0:04:02.63,0:04:05.84,Default,,0000,0000,0000,,and formation of clouds through satellite images
Dialogue: 0,0:04:05.84,0:04:07.88,Default,,0000,0000,0000,,or cameras that look up at the sky
Dialogue: 0,0:04:07.88,0:04:10.76,Default,,0000,0000,0000,,to maximize the energy from solar power plants
Dialogue: 0,0:04:10.76,0:04:13.04,Default,,0000,0000,0000,,and minimize energy waste.
Dialogue: 0,0:04:13.04,0:04:14.36,Default,,0000,0000,0000,,If we could accomplish that,
Dialogue: 0,0:04:14.36,0:04:16.48,Default,,0000,0000,0000,,you'd be able to enjoy this video
Dialogue: 0,0:04:16.48,0:04:18.49,Default,,0000,0000,0000,,powered solely by the sun's rays,
Dialogue: 0,0:04:18.49,0:04:20.07,Default,,0000,0000,0000,,no matter what the weather,
Dialogue: 0,0:04:20.07,0:04:21.84,Default,,0000,0000,0000,,although if the sun is shining,
Dialogue: 0,0:04:21.84,0:04:24.07,Default,,0000,0000,0000,,you may be tempted to venture outside
Dialogue: 0,0:04:24.07,0:04:27.03,Default,,0000,0000,0000,,to go and do a different kind of cloud gazing.