Discover Discover the energy the energy of hydrogen of hydrogen

(1)

Discover Discover the energy the energy of hydrogen of hydrogen

Measuring the solar constant

Krzysztof Rochowicz, Grzegorz Karwasz,

Toruń, Poland

(2)

This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (JU) under grant agreement No 826246.

The JU receives support from the European Union’s Horizon 2020 research and innovation programme and Italy, Denmark, Poland, Germany, Switzerland.

Sun is the main source of energy on Earth

https://solarscience.msfc.nasa.gov/images/Yohkoh_920508.jpg

Sun shines from 4.5 bln yrs* (and before in its place was some proto-Sun).

The geothermic flux from the interior of Earth is solely 65 mW/m

²

while the solar constant (i.e.

the energy for 1m

²

outside Earth atmosphere) is as much as 1367 W/m

²

.

This constant flux allowed the evolution of life on Earth.

And Sun should shine for some next 9 bln yrs.

*Recent geological studies estimate the age of the Solar system as 4.567 bln years.

(3)

This constant energy flux assures a rather stable climate on Earth

Tiny changes (0.1%) of the solar constant are related to 11yrs cycles of Sun actvitiy. Maxima of solar activity are related to the increased number of dark spots. Why 11 yrs? – we do not know.

Galileo was furst who with his telescope noticed Sun spots (and became blind due to excessive observations).

.

(4)

Lowered energy flux from Sun causes disasters for life

English painter, Wiliam Turner documented presence of volcanic dust in atmosphere. Credit: National Gallery

Reduced solar flux energy can be caused by volcanic eruptions or meteorites explosions.

These were causes of dinosauri extinction (65 mln yrs ago) or famine in Ireland

^*

(1816).

*https://en.wikipedia.org/wiki/Year_Without_a_Summer

(5)

Measuring solar constant

The value 1367 W/m

²

of the total solar radiation flux to Earth is measured outside atmosphere.

Out of this 10% falls into ultraviolet, 50% into visible (380-760 nm wavelength) and 40% into infrared. But this is outside atmosphere.

UV (the most energetic part) is cut in the upper atmosphere and in stratosphere (by ozone). IR is absorbed by molecules like CO

₂

and H

₂

O. Haze, dust, clouds reduce the flux further.

How much of the solar energy does it arrive to the ground?

We will measure it.

(6)

Measuring the solar constant

Scheme of the experimental setup

http://sciencenetlinks.com/media/filer/2011/10/07/measure_actsheet1.pdf

Try and compare:

•different bottles

•different colours

•different weather

•different season

Material needed:

- a glass bottle (can be also in green glass), possible flat-sided, with ½ l capacity

- a cork, fitting the bottle, with a hole drilled for the termometer

- a termometer: any type, even that ofr the medical use; remember during the experiment to stop it before the termometer reaches the end of its scale

- books or boxes to position the bottle - dark ink, for example from jet-ink printers

(7)

Measurement sequence

Procedures:

1. Prepare the collector bottle by filling it with a known amount of water. Add a few drops of the ink to make the water dark, and place the thermometer through the hole in the cork.

2. Place the collector in shade so that it stabilizes to the mean air temperature:

leave it for 10 minutes or until the temperature does not change any more.

3. Move the collector to sunlight. Make sure the unit is shaded while moving. Set the collector down so that the flat surface is as perpendicular to the incoming

sunlight as possible. Use books or boxes to get a perpendicular orientation. Do not uncover the bottle yet.

4. Begin the experiment by uncovering the collector: sign the exact time. Read the temperature every 2 minutes.

5. Allow the collector to absorb sunlight for 20 minutes or at least enough time to get at least a 3–4 ˚C temperature rise.

6. Measure the amount of the bottle’s surface that is exposed to the Sun and record the area in square meters on the Data Table.

7. With the help of next page calculate the power (in J) absorbed by the bottle,

(8)

Data and calculations

Volume of water used:………..liters

Mass of water used:………..kilograms Exposed surface area:………..m²

Initial temperature………..°C Final temperature………...°C Temperature change ΔT………....°C Elapsed time………..s The specific heat of water: 4186 J / kg °C The Energy absorbed by your water:

4186 × your mass × temperature change =

………..J

Uncorrected solar irradiation for the earth’s surface:

Energy / time / your collection area = ………….J / s m²

This is uncorrected solar irradiation for the earth’s surface.

You can multiply it by 2 to correct for the glass and also by 1.4

to correct it for the atmosphere; compare it to the accepted value.

http://sciencenetlinks.com/media/filer/2011/10/07/measure_actsheet1.pdf