Space Apps Challenge 2018

OUR 3D DEMO SYSTEM DESIGN ( JUST DEMO ^^): https://grabcad.com/library/pv-ft-csp-solarwings-1

I/ INTRODUCTION

-The depletion of energy resources is no longer a warning in the distant future. In fact, it is calculated by the specific figures and events happening quickly.

- Mankind has gradually exploited the other clean and lasting energy sources. This project will focus on Solar Energy.

- The sun is considered as an inexhaustible source of green energy (at least 5 billion years later). Solar radiation sends to Earth about 174 petawatts, approximately 30% is reflected back to the space while the rest is absorbed by clouds, oceans and land, about 122 petawatts. Therefore, solar energy is being exploited and used in many countries around the world. The most important application of it is the solar power industry.

- There are 2 typical kinds of system that can exploit energy from Sun until now:

+ Photovoltaics (PV): applying the conversion of light into electricity by using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry.

+ Concentrated solar power (CSP): producing solar power by using mirrors or lenses to focus a large area of sunlight, or solar thermal energy onto a small area. Electricity is generated when the focused light is converted to heat and heat engine is (usually a steam turbine) connected to an electrical power generator or has a thermochemical reaction.

- These systems all have the advantages and disadvantages that affect the efficiency.Therefore, there are many problems which we have to solve.

II/ THE PROBLEMS WE FOUND

1/ PHOTOVOLIC (PV):

- The position of the Sun (compared to the ground) is not the same at the different times of a day and month. Meanwhile, solar energy is at the fully-absorbing when the parallel light rays from the Sun is perpendicular to the surface of the solar cells. In order to fully exploit this kind of energy, we have to build some trackers for the solar panels which can locate the sun position to obtain the highest solar energy.

- There are many kinds of solars tracker in the world but they all have some disadvantages (table below).

1 Axis Tracker	Multi-axes tracker
Included 1 axis, rotate panels in the direction from the East, to the zenith, then to the West to follow relatively the Sun.	Included multi-axes, usually 2 axes. One axis rotates to adjust azimuth and another one adjusts altitude.
Advantages Simple More effective if the system is in area near the Equator Reduce the possibility of damages. Saving cost	Advantages Always perpendicular to the radiation from Sun. not depend on the latitude Effective, high efficiency
Disadvantages Not exactly perpendicular to Sun, leads to energy wastage The higher latitude, the more energy wastage	Disadvantages Complex Increase the number of engine Increase the possibility of damages Expensive

- Solar panel efficiency is affected negatively by temperature increases. Photovoltaic modules are tested at a temperature of 25 degrees C – about 77 degrees F, and depending on their installed location. For example if the temperature coefficient of a particular type of panel is -0.5%, then for every 1˚C rise, the panels maximum power will reduce by 0.5%. Heat can reduce output efficiency by 10-40%.The system will be not affective if we don’t reduce the temperature of solar cells.

- Photovoltaics energy storage system is extremely difficult because we use so much energy, you need to store a lot of energy in a system with lots of inefficiencies to convert useable energy into a stable, storable form and back again at will. This problem is more terrible at night when electricity need is highest.

- In general, all solar power system use a modest amount of water (approximately 20-40 gallons per megawatt hour, or gal/MWh ) for cleaning while the systems are usually set up in dry place where water is needed most.
2/ CONCENTRATED SOLAR POWER (CSP):
- Cost for CSP is still at a high level, lots of factors such as technology, investment mechanism, DNI resources may affect the final cost, indicating the great potential for further cost reduction.CSP costs could fall to between 8 US cents per kilowatt hour (kWh) and 12 cents per kWh depending on the location and solar resource quality.

- The process of operational CSP water usage is summarized below:
Water washing of the mirrors requires 20–40 gallons/MWh. Makeup water for the steam cycle process water requires 30–60 gallons/MWh. Cooling system water requirements for the steam cycle process range from 0–900 gallons/MWh, depending on CSP technology and cooling system: A wet-cooled system can require between 750 and 900 gallons/MWh. Cooling requirements for auxiliary systems (if separate from steam cycle cooling) also depends on CSP technology and cooling system. A dry-cooled system adds no additional water consumption. A hybrid-cooled system adds an amount somewhere between wet-cooled and drycooled values that is dependent on the frequency of usage of the wet cooling. CSP technology is still complex and it needs more time to develop. The capacity of CSP is also expanding, though with less deployment.
III/ PROJECT OVERVIEW
1/ ABSTRACT:
- We developed a new system which is not only improve the previous drawbacks but also develop lots of benefit:
Our system combines Photovoltaics system (PV) and Concentrated solar power system (CSP) support each other to work better.
- According to The equatorial system, our tracker system can save thousands of engines compared to nomal tracker systems.
- Simplify the structure compared to Multi-axes tracker.
- Reduce the possibility of damages.
- Increase efficiency up to 30% compared to Fixed system and up to 5% compared to other trackers designs.
- Our design uses fluid flow that helps the system to considerably reduce heat in Photovoltaic cells, in other word, efficiency of the PV system will go up about 20%.
- Prolong the system’s longevity of PV cells.
- Saving cost.
- The fluid flow supplies a huge energy for Concentrated solar power ( trillions Joule per day) to vaporize water esier and reduce the use of thermal storage (molten salt).
- Save up to hundreds of thousands gallons of washing water per day, especially in dry place where water is needed most.
- Reduce storage problems of Photovoltaics system.
- Photovoltaic solar power system will promote to work with high performance with our solusions during daytime while Concentrated solar power system will decrease the output capacity to save more thermal storage energy at night when electricity need is highest.
- Photovoltaics system technology improvements and expanding markets force the cost dropping down to a low level which can compete against traditional power. Currently, the cost for CSP seems to be much higher than PV but it has many prospects. With our solutions, we can provide energy even day or night, use the nice cost of PV system also expand and develop CSP’s capacity, cooling system, technology, market… for CSP’s brighter future.

2/ SUMMARY OF PRINCIPLES:

• New kind of solar panel tracker is designed based on Equatorial coordinate system to maximize efficiency, simplify structure, save thousands of engines, reduce cost…
• The circulation of a very thin water layer ( from outside source) by using a flattened network tube ( high thermal conductivity material) contact the bottom surface of Photovoltaic cells to reduce the heat, increase efficiency, prolong the system’s longevity… After flowing through Photovoltaic system, water is saved in a tank, will be use for adding makeup water and thermal energy to steam cycle system to optimzize evaporation process. It’s also use for cleaning the total system to generate electricity efficiently and cost-effectively.

IV/ OUR DESIGN:

1/ THE EQUATORIAL PHOTOVOLTAIC PANEL TRACKER:

i/ PRINCIPLE:

The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects. It may be implemented in spherical or rectangular coordinates, both defined by an origin at the centre of Earth, a fundamental plane consisting of the projection of Earth's equator onto the celestial sphere (forming the celestial equator), a primary direction towards the vernal equinox, and a right-handed convention.

Our tracker design is based on The equatorial coordinate system, so it’s included four levels constitude:

- Azimuth (Az): We will set up the system to North-South direction (Center of Earth to Polaris).

- Altitude (Alt): Elevate one side of panel system higher than another side along to North-South direction. This angle is equal to the latitude where we establish the system. Altitude axis is use to adjust the angle of Right Ascension axis compare to the ground.

For example: if we set up this system at latitude 10˚, this angle will be 10˚.

- Right Ascension axis (RA): ) Analogous to terrestrial longitude, right ascension is usually measured in sidereal hours, minutes and seconds instead of degrees, a result of the method of measuring right ascensions by timing the passage of objects across the meridian as the Earth rotates.This axis is also called Pole Axis (parallel with Earth rotation axis), spin with angular velocity equal to Earth rotation angular velocity in the opposite direction.

- Declination axis (DEC): Declination is analogous to terrestrial latitude. This axis is perpendicular to the RA axis, it adjusts the solar panels declination to follow the motion of Sun on ecliptic.

A ‘’deep-sky object’’ declination seems fixed for a very long time. However, the Sun is not considered as a deep-sky object, Sun’s declination changes slowly during a year from -23.5˚ to 23.5˚ and turn back.

However, this angle changes very slow during a day, a few arcseconds , so it will not affect to PV efficiency. So declination axis as fixed in a very long time and can adjusted a few in each period of the year to follow Sun’s declination.

In reality, the Azimuth axis and Altitude axis is fixed when we establish the system at a specific location. So these axes are not neccessry to build, we just need to set up the system with fixed corresponding angles. We just remain Right Ascension axis and Declination axis.

As a result, we just need to use a few air engines with pipe network to control thousands of system declination. In addition, one of our tracker system controls many solar panels, the number of engines for RA axis is reduce too and it also saves material cost and simplifies the structure.

We just focus on the mechanical structure of tracker system, not on the programs, light sensor, control system… because the world already has those things.

ii/ CACULATION

We suppose to establish the tracker system at latitude 20˚.

Conventions:

- Angle of Sun radiation compare to solar panel along to East-West direction: a.

- Angle of Sun radiation compare to solar panel along to North-South direction: b.

- Radiation that is perpendicular to the solar panel instantaneous: R.

We calculate that:

-Equinox points are intersection points of Equator and Ecliptic. At these points, Sun declination is equal to zero, and it reach the average altitude in Horizontal coordinate system of the year.

- Average angle of radiation compare to fixed solar panel that is parallel to the ground along to North-South direction of the year:

90˚-20˚= 70˚

- The radiation comes to that fixed solar panel:

A= sin(b) x ∑Rsin(a)= sin(70) x ½ x (πR²) = 1.476 x R²

- The radiation comes to one axis solar tracker panel:

B= sin(b) x 2R² = 1.878 x R²

- The radiation comes to Multi-axis solar tracker panel and Our system:

C= 2R²

However, each Multi-axis solar tracker uses 2 engines as a same time so it consumes more energy while Our tracker design uses a lot less number of engines.

*If energy absorbtion by Fixed system is 1, then we have:

- One-axis solar tracker system: ~ 1.272

- Multi-axes solar tracker system: ~ 1.355

*Angle comparision between Multi-axes solar tracker and Our tracker design:

- Rotation of Right Ascension axis and Azimuth axis: Same.

- Rotation of Altitude axis ( Multi-axes tracker):

70˚ x 365 = 25550˚

- Rotation of Declination axis ( Our tracker design):

23.5˚ x 2 x 2 = 94˚

It is clear to see that the 2rd axis in Our tracker design rotates less than Multi-axes tracker about 272 times. Althout it is not much meaning in energy saving, it leads to many good effect like saving thousands engines, minimalism of structure, reducing cost…

iii/ VALUES:

a/ Advantages:

- Simple.

- Updating exactly the coordinate on the axis.

- H design can lifting well the panels up. It is suitable for large fields and does not depend on the panel size.

- Just using one motor for each system, so the energy of the remaining axes is almost toward 0.

- Using well at every latitude.

- Saving motors, building materials as well as time and effort.

- Simple structure, easy to build and apply.

Therefore, we can take full advantage of sunlight, greatly reducing the cost compared to 2-axis rotation.

Compared to the old systems, we can see the advantages of the new system. To give a clear example, we consider at a point which has latitude from medium to high (large radiation angle enter). At a averagely low latitude place like latitude 20°N, we choose the energy absorption of the fixed system is 1. According to our calculations, the energy absorption of other systems, including the new system that we are introducing, is as follows:

	FIXED SYSTEM	OLD SINGLE AXIS SYSTEM	MULTI-AXES (OLD) SYSTEM	NEW SYSTEM
Structure	Horizontally fixed system	Turning from The East to the West	2 axes, the azimuth axis and the altitude axis
Efficiency	The more latitude, the less efficiency		Optimum performance at every latitude by tracking perpendicularly the sun
Movement	No movements	Only in 1 axis	Multi - axes, multi - engines	Only in 1 axis
Energy rate (compare with Fixed system)	1	1.272	1.355	1.355

	MULTI – AXES SYSTEM (OLD)	NEW SYSTEM
Applicability	Limited in size of solar cells. The larger and longer solar cells are, the harder the system works	Bigger size of solar cells. Suitable for an industrial application
Energy losses	Because of many engines, operation lost more energy and reduce energy efficiency	Operating a motor for both axes so it can save more energy
Reliability	Increasing damage rate because of complex system	Reducing damage rate because the system is simple
Assembling	Complex, costly	Simple, cost saving
Energy rate (compared to the permanent)	1.355	Up to 1.355

b/ Disadvantages:

- More complex than Single axis system.

- Have to monthly adjust declination axis.

2/THE MULTIASKING WATER FLOW:

i/REDUCING TEMPERATURE OF PHOTOVOLTAICS CELLS:

a/ IDEAS:

Our idea is the circulation of a very thin water layer by using a flattened network tube

( high thermal conductivity material) contact the bottom surface of Photovoltaic cells:

- It may reduce the heat from Photovoltaics cells significantly, leads to the increase of cells efficiency (about 0.5%/ ˚C).
- It must be in the bottom surface of solar cells because it will not reduce the radiation from Sun to solar cells.
- The top surface inside the flattened tube should be rough because it will increase the area of contact between water and tube material. It will increase more effective of heat exchange.
- Because it is a very thin system so its weight and the water inside are trivial. If we calculate in a solar tracker system, it will not affect to the rotation of engine.
- With this design, we just need to use one or a few water pumps to run the system totally.
- Inlet water from outside source, also be use for other functions of the system, so with the same amount of water, we can use it for many purposes.
- The high temperature water after using in Photovoltaic system is also used to maximize the evaporation process of Concentrated solar power system.
Water after using will be pumped into a tank to serve the following processes.

b/ CACULATION:

We suppose to establish a 75 Megawatts Solar field with 250000 300W Solar Panel with 1.960m x 0.992m in size each panel and the thickness of each flattened tube is 0.5mm:

- Volume of each flattened tube:

Vt= 1.96 x 0.922 x 0.0005= 9.0356 x 10^-4 (m³)
- Volume of all tubes:

V= Vt x 250000= 225.9 (m³)
- Heat water absorbs to increase 1˚C in a process:

Qa= 225.9 x 1000 x 4180 x 1 ~ 943 million Joule
- Heat water absorbs to increase X˚C in a process:

Qx= X x Qa
- The heat water absorbs per day can reach Tens of Trillions Joule.
- Specific heat of solar cell is more less than specific heat of water so each 1˚C increase of water temperature, solar cell decrease more times than that. So the flow rate could be very slow.
The flow rate depends on further researchs and experiments in reality.

ii/ MAXIMIZING VAPORIZATION PROCCESS FOR STEAM TURBINE:

a/ IDEAS:

Water after using for reducing heat of solar cells will be pumped into a tank. From this tank, high temperature water will be pumped into the makeup water pipeline of CSP’s steam cycle system instead of lower temperature from outside source. Makeup water for the steam cycle process water requires 30–60 gallons/MWh:

- It will maximize vaporization process for steam turbine.
- Save trillions Joule of heat for easier vaporization.
- Save a huge energy of CSP’s thermal molten salt storage.

b/ CACULATION:

We suppose to establish a 392 Megawatts Concentrated solar power system ( like Ivanpah Solar Power Facility). It performs about 1781 Megawatt hour per day.

- Makeup water for the steam cycle process water requires in a day: ~0.227 x 1781 = 404.5 (m³)
- Thermal energy save a day: 404.5 x 1000 x 4180 x X˚C ~ 1.7 billion Joule x X˚C
- The more heat water absorbs from Photovoltaic cells, the more thermal energy save for Concentrated solar power system.

iii/ CLEANING WATER FOR BOTH SYSTEM:

a/ IDEAS:

Some utility-scale solar power plant technologies, specifically parabolic trough and power tower, need water to generate electricity efficiently and cost-effectively. All solar power system use a modest amount of water (approximately 40 gallons per megawatt hour, or gal/MWh ) for cleaning. Water after using to reduce heat from Photovoltaic cells is also used for cleaning both system. It can save a lot of water while the systems are usually set up in dry place where water is needed most.

b/ CACULATION:

Photovolic system is supposed to perform 450 Megawatt hour per day, then:

Water requires for cleaning Photovolic system a day: 450 x 0.151= 68 (m³)
Water requires for cleaning Concentrated solar power system a day: 1781 x 0.151 = 268.9 (m³)
Water requires for cleaning both system a day: 68 + 268.9 = 336.9 (m³)

3/ TOGETHER IS BETTER:

- When the sun falls, electricity demand increases to a high level but PV outputs fade. PV must be combined with storage system which can produce stable output but it is extremely difficult and expensive.
- The largest advantage of CSP is that it could provide dispatchable power as well as the huge heat storage capacity. Molten salt is widely used for storing heat because it is cheap, safe and easily accessible. From technical point of view, storing thermal heat is much easier and cheaper than storing electricity. Armed with thermal storage, CSP plant is quite friendly to power grid, it can offer high quality electricity even during nighttime.
- The combination of both systems will solve this problem partially. Two systems will work together, in addition, our design will make Photovolic system reach high performance at day time while Concentrated solar power system will decrease the output capacity to save more thermal storage energy at night when electricity need is highest, decrease the burden of storage energy problem of Photovolic system.

V/ CONCLUSION:

Photovoltaic solar power system has a long history, its market is expanded around the world. Not only that, nowadays there are more and more modern teachnology which are applied for this solar power system and it is clear that Photovoltaic solar power system’s cost is cheaper and more popular than other solar power systems. Meanwhile, Concerntrated solar power system is not applied popularly although it is a potential system. Our design is a balance between two kind of solar power system. It not only produces a great energy source for the world but also takes full advantages of previous market to creates the next step to develop Concentrated solar power systems.

VI/ SOURCES:

• https://www.seia.org/initiatives/water-use-management - water use management.
• https://www.nrel.gov/docs/fy15osti/61376.pdf - Concentrating Solar Power and Water Issues in the U.S. Southwest.
• http://helioscsp.com/the-future-looks-bright-for-concentrated-solar-power/ - The future looks bright for Concentrated Solar Power.
• https://www.civicsolar.com/support/installer/articles/how-does-heat-affect-solar-panel-efficiencies - How Does Heat Affect Solar Panel Efficiencies?
• https://en.wikipedia.org/wiki/Ivanpah_Solar_Power_Facility - Ivanpah Solar Power Facility.
• https://en.wikipedia.org/wiki/Photovoltaic_power_station - Photovoltaic power station.
• https://en.wikipedia.org/wiki/Solar_power - Solar power.
• https://en.wikipedia.org/wiki/Equatorial_coordinate_system - Equatorial coordinate system.
• https://en.wikipedia.org/wiki/Equatorial_mount - Equatorial mount.
• https://en.wikipedia.org/wiki/Solar_tracker - Solar tracker.
• http://www.lth.se/fileadmin/ht/Kurser/MVK160/2009_reports/Gonzalo_calero.pdf.pdf - Heat transfers in photovoltaic panel.
• https://en.wikipedia.org/wiki/Concentrated_solar_power - Concentrated solar power.
• https://www.stage-ste.eu/documents/General%209%20RE_Technologies_Cost_Analysis-CSP.pdf – Concentrated solar power.
• https://www.sciencedirect.com/science/article/pii/S1359431111006247 - Evaluation of cooling technologies of concentrated solar power plants and their combination with desalination in the mediterranean area.
• https://en.wikipedia.org/wiki/Vaporization - Vaporization.
• https://www.quora.com/Does-the-rising-in-temperature-drowns-the-efficiency-of-a-photovoltaic-solar-cell - Does the rising in temperature drowns the efficiency of a photovoltaic solar cell?
• http://solarcellcentral.com/csp_page.html - Concentrated solar power.
• http://helioscsp.com/pv-or-concentrated-solar-powe... - PV or Concentrated Solar Power, which solar power technology will you choose?
• https://en.wikipedia.org/wiki/Injector - Injector.
• https://solarcalculator.com.au/solar-battery-stora... - Solar baterry storage.
• https://grist.org/article/2011-01-31-los-angeles-r... - Los Angeles residential solar PV less costly than any concentrating solar power plant.