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Microwave Transmission through Atmospheric Densities Maturaarbeit/Extended Essay

Author: Michael Krebs

Supervisor: Heinz Anklin Co-Reader:[DATUM] Lukas Kaufmann [FIRMENNAME] [Firmenadresse] Wettingen, 11th November 2019

Table of Contents Introduction ...... 2 Theory ...... 3 Concept of Transmission ...... 3 Propagation in the ...... 5 Barometric Formula ...... 7 Risk Assessment ...... 7 Experimental Method ...... 8 Sender ...... 9 Problems with the Sender ...... 12 Receiver ...... 13 Requirements for the Measurements ...... 14 Method of the Measurements ...... 14 Data Presentation ...... 15 Field ...... 15 Pressure Dependent Measurements ...... 16 Discussion...... 18 Data Interpretation ...... 18 Data Uncertainties ...... 20 Data Limitations ...... 21 Conclusion ...... 22 Evaluation ...... 23 Bibliography ...... 24 Appendix ...... 27 Risk Assessment ...... 27 Material List ...... 28 Raw Data ...... 28

1

Introduction

This essay is based on revising the concept of an orbital solar power station (OSPS) and therefore in- vestigating into the research question; “To what extent does the atmospheric density on influence the loss of ? “. The concept of such a station can be traced back to the year 1968.1 An OSPS would harvest the energy, produced by the , and convert it into electrical power. Due to atmospheric propagation the efficiency of collecting the sunlight outside earth’s atmos- phere is higher than on its surface. Out of the 1367 W/m2 which reaches earth’s atmosphere, only 1000 W/m2 actually make it through.2 Therefore it is interesting in the first place, to investigate for an alternative to exploit a greater amount of the ’s energy, before it penetrates the atmosphere. In this work, the focus lies on the advantages and disadvantages of energy transmission from the sta- tion to the earth’s surface using by conducting a simplified experiment with a sender and receiver at three locations differentiated by their altitude.

1 „Space Based Solar Power“, Wikipedia, https://en.wikipedia.org/wiki/Space-based_solar_power#target- Text=In%201941%2C%20science%20fiction%20writer,first%20described%20in%20November%201968, Last accessed 5 November 2019. 2 „The sun as a source of energy“, Itacanet, https://www.itacanet.org/the-sun-as-a-source-of-energy/part-2- solar-energy-reaching-the--surface/, Last accessed 5 November 2019. 2

Theory

Concept of Microwave Transmission The concept of microwave transmission has been around since World War II, when the need for data transmission and became more prominent. Many countries have invested time and money into researching the characteristics of microwave-based data links, which is one of the main applications nowadays. By cutting the complexity of the system down to a minimum, the ultimate idea revolves around a mi- crowave and a microwave receiver. The transmitter consists of a power source, connected to a magnetron, where begin to oscillate due to a produced around them. This oscillation results in the creation of an electromagnetic , which is the combined wave front, as shown in Figure 1, of several traveling away from the magnetron.

Figure 1; Illustration of an electromagnetic wave front

The emitted energy needs to be converted from wave into electricity, for the concept of an OSPS. This process can be achieved by capturing the electromagnetic waves using a rectenna. A rectenna consists of two elements, being a dipole and a (RF) .3 The distance between the endings of the depends on the frequency being used.

3 „Rectenna“, Wikipedia, https://en.wikipedia.org/wiki/Rectenna, Last accessed 5 November 2019. 3

The RF get emitted radially and therefore decrease in power density by the formula shown below. In order to increase this density, the RF can be guided. This guidance can be evoked by the different types of in the form of an antenna, or in the case of this paper, a physical guidance using the effect of reflection by specific materials.

푃푡 푃 = 4휋푟2

The radial power intensity decline of waves can be described by the formula above, which divides the

4 initial power (푃푡) by the quadratic distance (푟) times 4휋.

In the broad picture, microwave transmission serves as a dense and efficient energy transfer method between earth orbit and the ground, therefore cancelling the cosine-effect.5 This effect increases the amount of atmosphere the radiation has to penetrate through, depending on where on the the ground base is positioned. The origin of this effect is illustrated in Figure 2, which indicates the differ- ence between the area of plane B and plane C. Therefore, with increasing volume to be penetrated, the amount of propagation also increases. This leads to a greater loss of energy if a is located anywhere remote from the equator.

Figure 2; Illustration of the cosine-effect

4 Manning, Trevor, Microwave Radio Transmission Design Guide, Norwood: Artech House, 2009, p. 10. 5 M. Ewert & O. Fuentes, Modelling and simulation of a solar tower power plant, Achen: Achen University, p. 4. 4

Propagation in the Atmosphere The atmospheric propagation of electromagnetic waves plays a large role in microwave transmission. There are specifically three effects, which will be discussed due to their significance. Since any matter absorbs energy, the first effect in focus will be the absorption. As already mentioned, every atom absorbs waves. According to the Lambert-Beer law, every matter has its own absorption coefficient (α) which influences the initial energy intensity (퐼0) of a wave expo- nentially by the distance (푑) penetrated. This can be seen in the formula below, describing the Lam- bert-Beer law.

−α푑 퐼(푑) = 퐼0푒

Furthermore, the formula of the absorption coefficient itself can be described by the product of the molar coefficient (n′′) of a material, times the angular frequency (푤) divided by the speed of (푐).6

푤 α = 2n′′ 푐

This law therefore describes the exponential decline of the energy intensity of electromagnetic waves the further it gets penetrated. Looking at this law on the molecular basis, moisture in the atmosphere has a big effect. Though moisture only affects waves with a frequency higher than 11 GHz, it is nevertheless worth mentioning that this can have a great impact on energy loss through the atmosphere.7

Another important part of propagation which will affect the system, is the effect of upper atmospheric . This is a process occurring at an approximate altitude of 80 kilometres, where ionized gases in the diffract the electromagnetic waves travelling through. This diffraction causes the waves to bend into the shape of an arc and eventually returning the way they came. Even though the effect has its advantageous in data transmission on earth, by using diffraction to send signals around the world, there is the disadvantage in energy transmission for an OSPS, that the microwaves travers- ing the atmosphere get diffracted and sent back into space.8

6 „Absorptionskoeffizient“, Wikipedia, https://de.wikipedia.org/wiki/Absorptionskoeffizient##target- Text=Der%20Absorptionskoeffizient%2C%20auch%20D%C3%A4mpfungskonstante%20o- der,auf%20R%C3%B6ntgenstrahlung%20und%20Gammastrahlung%20verwendet, Last accessed 5 November 2019. 7 „ Fade“, Wikipedia, https://en.wikipedia.org/wiki/Rain_fade, Last accessed 5 November 2019. 8„Atmospheric Diffraction“, Wikipedia, https://en.wikipedia.org/wiki/Atmospheric_diffraction, Last accessed 5 November 2019. 5

A similar effect occurs in the lowest atmospheric layer, the troposphere. It is called the , which occurs at an altitude of 18 kilometres. The affected range around 2 GHz, which means that they are being influenced by the moisture in this layer of the atmosphere. Once more, this effect is being used to transmit data across the atmosphere, by emitting electromag- netic waves into the and receiving the scattered waves. In fact, only 1x10-12 times of the energy emitted reaches the receiver over a distance of 1000km. This number indicates, that the loss of energy due to tropospheric scattering is significantly small and therefore does influence the transmission but keeps it in an acceptable range.9

To summarize the three effects of propagation, the paper “ for Solar Power (SPS)” by N. Shinohara, provides data for the analysed frequencies (2.45GHz). Mr. Shinohara states that for this frequency, the interactions between the waves and the atmosphere are mostly based on the absorption by moisture and . Therefore, the greatest loss occurs due to absorption and the atmospheric scattering in the lower layers of the atmosphere. The loss of energy is being described as “approximately 0.007 dB/km” which, applied to the OSPS, would mean a decrease of 0.035 dB, which indicates the loss throughout the entire atmosphere.10

9 „Tropospheric Scatter“, Wikipedia, https://en.wikipedia.org/wiki/Tropospheric_scatter, Last accessed 5 November 2019. 10 N. Shinohara, Wireless Power transmission for Solar Power Satellite (SPS), p. 24. 6

Barometric Formula In order to define the loss of energy through the entire atmosphere, it is important to consider the fact, that the atmosphere consists of different layers with different thicknesses. To take this into account, the barometric formula can be used to define the pressure at different alti- tudes and therefore the loss of energy. Due to the reason of complexity and the lack of sufficient amounts of data points, this step of integrat- ing the formula will be left out in this paper, though its effects will still be taken into consideration in the conclusion.

푇 푔0푀 푏 푅∗퐿 푃 = 푃푏( ) 푏 푇푏 + 퐿푏(ℎ − ℎ푏)

The variables included in this formula are the following; Static pressure (푃푏), standard

(푃푏), standard temperature lapse rate (퐿푏), height above sea level (ℎ), height at bottom of layer (ℎ푏), ∗ 11 universal gas constant (푅 ), gravitational acceleration (𝑔0), molar mass of Earth’s air (푀).

Risk Assessment

Due to the fact that microwave radiation can be harmful for humans, an exceptional focus on safety had to be warranted at all time. Thus, thoughts on risks and safety had to be made beforehand and furthermore summarized into a “Risk Assessment” which can be found in the appendix.

11 „Barometric Formula“, Wikipedia, https://en.wikipedia.org/wiki/Barometric_formula, Last accessed 5 November 2019. 7

Experimental Method

Due to the fact, that the area to be studied is highly complicated and complex, the experimental setup had to be simplified. To simplify, a lot of research has been undertaken and with the help of Jon Wal- lace’s paper “Inexpensive Demonstrations Based on the IEEE Presentation by John Kraus”, the decision was made to pursue a similar method. The experiment has been cut down into a simple sender and receiver concept, where a regular house- hold microwave served as a sender and a homemade log-periodic antenna would be used as the re- ceiver. Though the receiver has been replaced with a commercially available component. All the equipment, needed for the experiment, was powered by electricity provided by a 5000W diesel generator.

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Sender The heart of the experiment was the microwave , after some research, the decision was made to proceed with the MWO 2088 from ohmexSwitzerland which has an output power of 700W. After run- ning a short functional check on the microwave itself, the device was being taken apart and all its components were laid out on a table as can be seen in Figure 3. While analysing, the control board underneath the propeller was discovered. At this point it became clear, that disposing the unnecessary parts of the , such as the and the ventilator, would create more problems than it would solve.

Figure 3; Components of the microwave laid out

Therefore the decision was made, to leave the components as they were and continue with the process. A sketch (Figure 4) of the wiring was created in order to avoid problems from occurring while assembling of the apparatus and additionally provide better understanding of the machine itself.

Figure 4; Sketch of the arrangement of all the components

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Subsequently, the components were ready to be assembled. The metal framing of the oven served as a shielding and the magnetron sits in the middle. Furthermore, the ventilator was mounted to the shielding for cooling.

Figure 5; Fully assembled apparatus (seen from the top)

Additionally, the lamp got attached to the outside of the metal frame, thus allowing for a physical signal in order to identify from far away if the apparatus is running or if a problem has occurred. Another mentionable feature is the safety , which are circled in Figure 5. The switches were bypassed by putting tape around, therefore activating the . By bypassing the safety fea- tures of the oven, a risk has been created, which is acceptable, due to the additional measures that have been taken into account.

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In order to guide the emitted microwaves, a horn was created, using cardboard and aluminium foil serving as reflection material. The horn itself was two long, with a 35° opening at the end as seen in Figure 6 and 7. This design lets the waves travel through the horn and ultimately routs them into the desired direction.

Figure 6; Calculations and sketch of the horn (Version 1)

The effectiveness of the horn has quickly been confirmed by data from the household microwave measurement device. The values of the radiation field test were in the acceptable safe range (>1mW/cm2) behind the opening of the horn itself, therefore not causing any harm for the person conducting the experiment.

Figure 7; Finished apparatus with horn version 1 attached

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Problems with the Sender Several problems arose with the apparatus. Firstly, it was not working because some components of the device were not grounded, which prevented the microwaves to be produced. Additionally, the fuses inside the control board burned through because either too much current was pulled from the magnetron or lightning strikes had shot through the aluminium foil from the horn, as captured in Figure 8 A thick aluminium tube served as the adapter between the magnetron and the homemade horn, which is illustrated in Figure 9 and served as a solution for this problem. The thickness of the tube was essen- tial, since it is able to deal with more energy than a thin layer of aluminium foil. Due to the massive amount of running time during the measurement, the magnetron heated up really fast, which might have influenced its efficiency. This will be further reviewed in the discussion.

Figure 8; Lightning strikes through aluminium foil

Figure 9; Updated version of the apparatus

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Receiver The receiver consisted of two main components, which were provided by the company “ Controls AG”. 12 The first component is the one capturing the microwaves, it is a wideband antenna which was mounted on a tripod in order to position it directly towards the magnetron. The antenna detects frequencies between 680MHz and 10GHz, therefore it is suitable for this experiment. The underground between sender and receiver was similar at all three locations, it was mostly grass and therefore its effects can also be neglected. The second component is connected to the antenna and analyses its output. It is the ana- lyser, which displays the converted waves from the antenna into power intensity in dBm. The spectrum analyser is a highly complex device, which has been used as displayed by the people at Computer Con- trols. The analyser was programmed to hold the maximum amount of power at 2.45GHz and display it in order to writing it down.

Figure 10; Setup of the sender and receiver as viewed from behind the sender

Figure 11; Setup of the sender and receiver as viewed from behind the receiver

12 Link to the company’s website, “Computer Controls AG”, https://www.ccontrols.ch/, Last accessed 5 Novem- ber 2019. 13

Requirements for the Measurements In order to measure the loss of power during transmission in different densities of the atmosphere, measurements in different altitudes had to be conducted. This is due to the reason that the density of the atmosphere decreases, according to the barometric formula, by the increase in altitude. Schlatt, Andermatt and the Gotthard pass fulfilled all the criteria and were chosen to be the locations for measurements.13 These criteria were; • Accessible by car • Wide and open space (in order to minimize damage to nature and infrastructure) • Far away from humans (due to emissions from the generator and safety reasons)

Method of the Measurements The sender and receiver were placed at a distance of four meters from each other. A reference dis- tance, which was three meters, has been chosen for observing the reliability of the measurements. At each location, 10 measurements were taken. These measurements lasted 10 seconds at 700W of output power from the sender. The amount and time were chosen, because the quantity seemed ac- ceptable in order to perform a reasonable data evaluation with regards to errors. Furthermore, the intensity data displayed by the spectrum analyser, as part of the receiver, were noted for the frequency emitted by the microwave, which is 2.45GHz.

13 Coordinates of the places; Schlatt: 47.564436| 8.214296, Andermatt: 46.630013| 8.586998, Gotthard pass: 46.557304| 8.568000. 14

Data Presentation

Radiation Field The first measurement that was performed, was to clarify the areas of danger while conducting exper- iments. The area around the apparatus was therefore subdivided into different ranges according to their degree from the horn.

Figure 12; Radiation field evaluation

Figure 13; Legend for the amount of power in the radiation field (mW/cm2)

The data has been gathered by using the household microwave measuring device MWT-2G from Voltcraft. Its output was given in mW/cm2, which can be viewed in the appendix. The colours of the legend go from dark red (>10mW/cm2) to white, where (5mW/cm2) marks the range where the amount of power becomes dangerous to the human tissue, there- fore the colour changes from red to around this “safety value”. In the graphic shown in Figure 12, it is visible that there is no significant amount of radiation observable behind the apparatus itself. Additionally, at two meters, the field narrows itself to 30 degrees left and right. The accuracy of this chart is rather imprecise, due to the limitations of the instrument. Though it serves its purpose to confirm that the person conducting the experiment is save behind the apparatus and the microwave intensity is in a safe range from thirteen meters of distance.

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Pressure Dependent Measurements The pressure dependent measurements were performed on the 21st of September 2019, all three lo- cations have been visited on the same day. At each location power, atmospheric pressure and magnetron temperature were monitored and noted. All this data is visible in Figures 14, 15 and 16 below.

Figure 14; Table of measurements in Schlatt

Figure 15; Table of measurements in Andermatt

Figure 16; Table of measurements on the Gotthard Pass

The significant data is on the right and displayed as the average of its own column. Additionally, due to an unknown reason, the magnetron temperature of the first four measurements are non-existent. This is not a big problem, due to the secondary importance of these measurements.

The conversion of the power given by the instrument in decibel-milliwatts (dBm) into Watts, was per- formed with the following formula.

푃(푑퐵푚) 10 10 푃 (푊푎푡푡) = 1000

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The raw data from the tables were then combined and transformed into a chart. All three datapoints (pressure, power and magnetron temperature) are included and represented in a comprehensible way. These charts are shown in Figures 17, 18 and 19 and each one includes the elevation of the loca- tion (Meters above sea level – MASL).

Figure 17; Data of measurements in Schlatt

Figure 18; Data of mesasurements in Andermatt

Figure 19; Data of measurements on the Gotthard Pass

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Discussion

Data Interpretation The raw data from above has been summarized into a chart (Figure 20), which shows the average of the 30 measurements at the three locations, including the elevation and average atmospheric pressure data during the time of the experiment. The chart allows to analyse the dependence of microwave transmission on atmospheric density, which is being looked at here as pressure. It is apparent, that at lower atmospheric densities, the amount of power (W) received by the instru- ment is higher than at higher densities. Even though the amount of power is extremely small in com- parison to the output power of the magnetron (700W to 10nW), the chart still allows interpretations to be made and come to a conclusion, since even the error rate is in an acceptable range and doesn’t interfere with the surrounding data.

Figure 20; Power output comparison chart with pressure data

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Although there are some uncertainties, these measurements allow to display a correlation, between microwave transmission and the atmospheric density. From left to right in Figure 20, the elevation of the location rises and the atmospheric air density de- creases, while the amount of power increases accordingly. This increase of power can be repatriated to the ever-decreasing number atoms in the atmosphere, the higher altitude one goes. The emitted microwaves therefore will not propagate as often, as when they penetrate through a molecularly denser part of the atmosphere.

Average power output (W) in correlation with pressure (kPa) at 4 meters distance with ploted trendline 9E-08

8E-08

7E-08

6E-08

5E-08

4E-08 y = -8E-10x + 8E-08 Power (Watt) Power 3E-08

2E-08

1E-08

0 0 10 20 30 40 50 60 70 80 90 100 Pressure (kPa)

Figure 21; Data ploted for atmospheric analysis

In Figure 21, the received power relative to the pressure is being illustrated. The green dots stand for the locations, which would be from right to left; Schlatt, Andermatt, Gotthard. When plotting a trendline, assuming the decline is linear, the intersection point with the y-axis would indicate the amount of energy emitted at the beginning. Though, since the data output of the spectrum analyser might be in the wrong range, this is not possible.

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Therefore, there are only assumptions to be made. If the decline is linear and the output data from the receiver would be in an acceptable range, one could conclude the loss of energy by taking the differ- ence on the y-axis. This difference is compiled by the output power of the transmitter, subtracted by the intersection point of the function above with the y-axis.

Hence, the experiment proves the hypothesis by providing the decline shown in Figure 21. Additionally, apart from the size of the numbers, the data points are more or less linear and therefore lead to a satisfactory result.

Data Uncertainties The immense reduction of power to the nano area is highly thought provoking and leads to questioning its cause. The mistake, if there is one, might lie in the output of the measurement instrument, which might have been provided with inaccurate settings or even a male calibration at the beginning. This circumstance complicates the process in the end, of concluding the efficiency of the system adopted to an OSPS.

Throughout the entire process of gathering the data, anomalies occurred. These anomalies emerged in the output data of the receiver, which is visible in Figures 14, 15 and 16. Some data points deviated heavily from the others, which lead to immense differences and created uncertainties, if a useful set of data could emerge from these samples. Though the anomalies of dif- ferences between the datapoints of one location deviated much more at three meters, than they did at four. Therefore, it was decided to ignore the measurements conducted at three meters and focus on the ones from four meters. Another aspect worth mentioning is the temperature increase of the magnetron during the experi- ment itself. This might have had an influence on the emitted microwaves, though it is unclear to what extent it effected the waves and thus it gets neglected for this paper.

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Data Limitations There are several limitations accompanying this method of proving the effectiveness of an orbital solar power station using microwave transmission. A transmission through different types of atmosphere needed to be simulated. In order to do so, the decision was made to cut the atmosphere into multiple horizontal pieces. This allowed for a simpler way of collecting the data. This method is a limitation of the experiment, because in the case of an OSPS, the atmosphere would be penetrated vertically. Three locations have been chosen for measurements, these locations are all underneath 2100 meters above sea level, which is only a 50th of the entire atmosphere14. These three locations are the highest points reachable and therefore limit the experiment to the lowest atmospheric layer. Although these data points can be plotted into the barometric formula and adapted to the entire at- mosphere, it remains unclear how the waves react and get propagated in higher altitudes with less molecules. Another limitation is the assumption that the loss of intensity is linear, while the barometric formula is based on exponential growth. Additionally, a parameter which has not been observed but would have been interesting, would have been the humidity at the locations at the time of the experiment. This data was not available due to the lack of weather stations in the alps. Regarding the theory of propagation, this would be a valuable addition to a future experiment.

14 „Karman Line“, Wikipedia, https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line, Last accessed 5 November 2019. 21

Conclusion

Due to inexplicable errors of the receiver, the estimation of the amount of energy being lost by getting transmitted through the atmosphere cannot be performed, therefore the conclusion is based on the correlation between pressure and power received at different altitudes. In that sense, the experiment undertaken, was a success. In its simplicity, the method allowed to ana- lyse the power difference. First of all, it has been proven that the power intensity of microwaves with a frequency of 2.45GHz decreases radially the greater the distance between sender and receiver is. Furthermore, when defining the independent variable as atmospheric pressure, the density of atoms changes. This change in density effects the propagation of the electromagnetic waves and therefore provokes a decline in intensity the higher the pressure is. Even though the effects of atmospheric scattering and diffraction in the upper layers of the atmos- phere is still unclear, the self-made apparatus, was able to provide sustainable data for partially an- swering the research question.

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Evaluation

The simplicity of the experiment allows for a conclusion based on the few parameters given. If this would be a paper investigating the economic efficiency, the data provided would need to be far more detailed. Additionally, experiments would need to be conducted throughout the entire atmosphere until the least achievable pressure. This could have been done in a vacuum chamber, but since the resources were limited, this step could not be undertaken. Therefore, concluding that there is a high loss, lacks significance and the exact cause for this loss. It would have also been interesting investigating the influence of moisture in contrast to air molecules and ionized gases on electromagnetic waves. This method would allow to break up the atmosphere into the given layers and therefore make meaningful conclusions.

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Bibliography

Printed Sources Books Manning, Trevor, Microwave Radio Transmission Design Guide, Norwood: Artech House, 2009.

Papers M. Ewert & O. Fuentes, Modelling and simulation of a solar tower power plant, Achen University, http://www.mathcces.rwth-aachen.de/.

N. Shinohara, Wireless Power transmission for Solar Power Satellite (SPS), ResearchGate, https://www.researchgate.net/publication/241656164_Wireless_Power_Transmission_for_So- lar_Power_Satellite_SPS.

Wallace, Jon, Inexpensive Microwave Antenna Demonstrations Based on the IEEE Presentation by John Kraus, Society of Astronomers, http://www.radio-astronomy.org/node/238.

Digital Sources „Absorptionskoeffizient“, Wikipedia, https://de.wikipedia.org/wiki/Absorptionskoeffizient##target- Text=Der%20Absorptionskoeffizient%2C%20auch%20D%C3%A4mpfungskonstante%20o- der,auf%20R%C3%B6ntgenstrahlung%20und%20Gammastrahlung%20verwendet, Last accessed 5 November 2019.

„Atmospheric Diffraction“, Wikipedia, https://en.wikipedia.org/wiki/Atmospheric_diffraction, Last accessed 5 November 2019.

„Barometric Formula“, Wikipedia, https://en.wikipedia.org/wiki/Barometric_formula, Last accessed 5 November 2019.

“Computer Controls AG”, https://www.ccontrols.ch/, Last accessed 5 November 2019.

„Karman Line“, Wikipedia, https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line, Last accessed 5 November 2019.

„“, Wikipedia, https://en.wikipedia.org/wiki/Rain_fade, Last accessed 5 November 2019.

„Rectenna“, Wikipedia, https://en.wikipedia.org/wiki/Rectenna, Last accessed 5 November 2019.

„Space Based Solar Power“, Wikipedia, https://en.wikipedia.org/wiki/Space-based_solar_power#tar- getText=In%201941%2C%20science%20fiction%20writer,first%20described%20in%20Novem- ber%201968, Last accessed 5 November 2019.

„The sun as a source of energy“, Itacanet, https://www.itacanet.org/the-sun-as-a-source-of- energy/part-2-solar-energy-reaching-the-earths-surface/, Last accessed 5 November 2019.

„Tropospheric Scatter“, Wikipedia, https://en.wikipedia.org/wiki/Tropospheric_scatter, Last accessed 5 November 2019.

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Figure Index Title picture 1: „Horizon Over the North Atlantic”, NASA, https://www.nasa.gov/multimedia/imagegallery/im- age_feature_2212.html, Last accessed 5 November 2019.

Title picture 2: „Space-based solar power”, Wikipedia, https://en.wikipedia.org/wiki/Space-based_solar_power, Last accessed 5 November 2019.

Figure 1: Manning, Trevor, Microwave Radio Transmission Design Guide, Norwood: Artech House, 2009, p. 8.

Figure 2: „The sun as a source of energy”, Itacanet, https://www.itacanet.org/the-sun-as-a-source-of- energy/part-2-solar-energy-reaching-the-earths-surface/, Last accessed 5 Novmeber 2019.

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Figure 14: Created by the author using Microsoft Excel 2016.

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Appendix Risk Assessment

Since radiation is known to be harmful to human beings, it is extremely important to investigate in the effects of microwaves and the possibilities to protect oneself.

Due to extensive testing and researching in the area of electromagnetic waves with a frequency around 2.45 GHz (microwaves), a lot of data is available to make an analysis. Microwaves do not lie in the portion of ionized waves and therefore cannot bring along the required amount of energy for ionizing atoms. Hence, they are unable to change DNA and cause cancer. Though microwaves can still be harmful, as humans use these types of waves every day to warm up food, the waves can also provoke the heating effect in human tissue. An area especially vulnerable for micro- waves are the eyes, which cannot dissipate the heat due to insufficient blood flow. Additionally, the amount of microwave leakage from a microwave oven is regulated to be below 5mW/cm2, which indi- cates that the intensity below is still in the “safe-zone”. It can therefore be said, that an exposure to microwaves does not have a big impact on the human body other than heating the tissue, though it is still unclear what the long-term effect on the molecules will be and if the waves are able to even accelerate the growth of cancer cells.

Taking this information into consideration, some precautions actions have to be taken in order to pre- vent any harm done to neither the person conducting the experiment nor the people and living beings around the area of experimentation.

While conducting measurements, no one should be in front of the apparatus. In addition to prevent any unwanted microwave leakage from the device, every possible leak will be covered with layers of aluminium foil since the waves are not able to penetrate through the foil. Furthermore, while working on the device, safety glasses and gloves have to be worn, power will be removed and the area around the experiment secured.

If all these precautions are fulfilled, the risk of an unintended event occurring, decreases by a huge factor.15

15 Manning, Trevor, Microwave Radio Transmission Design Guide, Norwood: Artech House, 2009, p. 5.

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Material List Sender Microwave oven ohmexSwitzerland, MWO 2088 Celsimeter Spring, Model super -K- Generator KIPOR, KDE 6500 E3

Receiver Microwave measurement device Voltcraft, MWT-2G Multimeter Keysight, U1273A Spectrum Analyzer Keysight, N9322C Wideband Antenna Aaronia, HyperLOG 60100

Raw Data Raw data from measurements with a distance of three meters.

Figure 22; Raw data from measurements conducted on the 21st September in Schlatt

Figure 23; Raw data from measurements conducted on the 21st September in Andermatt

Figure 24; Raw data from measurements conducted on the 21st September on the Gotthard pass

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Raw data from measurements required to create the radiation field graphic.

Figure 25; Raw data from the radiation field measurements at a distance of 1.5 meters

Figure 26; Raw data from the radiation field measurements at a distance of 2 meters

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Figure 27; Raw data from the radiation field measurements at a distance of 3 meters

Figure 28; Raw data from the radiation field measurements at a distance of 4 meters

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Figure 29; Raw data from the radiation field measurements at a distance of 5 meters

Figure 30; Raw data from the radiation field measurements at a distance of 6 meters

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Figure 31; Raw data from the radiation field measurements at a distance of 7 to 13 meters

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