May 24th:
17 Applications and Implications
Useful Links
Final Project Planning and Projections slides
History of Solar Energy
This weeks task is accertain and propose a final project that integrates the range of units covered, to plan for the finalisation and resolution of our main project goals. Our project needs to show individual mastery of the range of skills covered during the course and where possible, you should make rather than buy the parts of your project:
What will it do?
My aim is to design and build a tracking system, which will automatically position itself to face the sun at a perpendicular 90° angle throughout the day and the year.
Thereby maximising the amount of potential usable energy collected at the receiver. The efficiency of an active tracking based system, despite the inherrent power requirements to move the motors, is generally between 30% - 35% gain when compared with static fixed panels.
Who's done what beforehand?
Solar Trackers are not by any means new technology, with examples of sun-collecting and focusing devices going back into our distant history. In 1839 French scientist Edmond Becquerel discovers the photovoltaic effect while experimenting with an electrolytic cell made up of two metal electrodes placed in an electricity-conducting solution, and the electricity-generation increased when exposed to light.
Technologies involved have since vastly improved, we can now gain a substantial amount of useful electrical energy directly from the sun's light source. And the efficiency and price of solar panels has come a long way in recent years. There are many designs and types of solar-tracker out there, and lots of ideas and examples to draw inspiration from and help with completion of my design. A solar tracking system will usually encorporate either single, or a dual axis active movement. In order to maximise the collector angle throughout the year as well as daily a dual-axis system is used.
In addition to the well known common PV type solar panels, other technologies and applications that also require sunlight tracking systems include: Heliostat type - mirrored arrays, parabolic reflectors or troughs, fresnel lenses, solar ovens, furnaces and sintering. Stirling engines, heat pipes and transfer systems ranging anywhere from simple heated water systems to advanced hot salt heat exchangers that power steam turbines to generate power.
Solar power generating system - Core elements:
- Battery storage bank - deep cycle
- AC/DC invertor
- Charge controller and regulator
- Panels for solar reciever
- Main mounting frame and Tracking system
- Motors and mechanical fixtures
- Connections wiring and junction box
- Electronics Housing for control IC board, motors and
- the light sensor module
For my project I am focussing on the mounting and tracking mechanism, with the aim of developing a cost efficient functioning dual axis system, with automated functionality via micro processor control and light sensing unit.
Materials and components required?
- Two Main drive motors, one for each axis. For now I am using Nema 17 stepper motors, but would like to acquire and test a linear actuator D.C. motors for the tilt movement.
- Gearing and Drive train - As of yet this is undecided and undergoing testing prototyping and more research. Options include:- Belt and pulley, Chain and gear, Wire wound or counterweighted tension systems, versus having a more direct drive with a potential planetary or worm gear, drive reduction system.
- For the main IC Control Board - until now I have been mainly using the arduino board with Pololu DVR8825 motor driver carriers to power the nema 17 motors, and also servo motors. However I will be adapting and developing my own control board using the ATtiny 84 or mega 328 to have at least four analogue inputs and four digital pwm output pins.
- Sensors - I have been testing standard photoresistors but will develop and produce a light sensor module as a break out board that will utilise four phototransistors with a wiring block, resistors, and a disconnectable connection cable.
- Cables, wiring, solder, resistors and capacitors, connector blocks.
- Main frame structure - the main material I intend to use for the frame is aluminium extruded profile tube. And angles. 3d printed brackets and fittings, and motor electronics housing.
Most of the materials for this project I intend to source and fabricate directly in the lab or from locally sourced materials and stock. Some of the electronics particularly the motors and any specialised metal frame parts or fixtures may have to be bought from online suppliers.
How much will it cost?
I would calculate or foresee that the base cost for my system in terms of materials and parts, will be in the range of £80-£250 depending on the level and specification of motors or actuators I use, and the quantity and quality of the alluminium parts used for the frame structure.
Systems - project breakdown
- Input - The Sun’s light source and its inherent position at different times throughout the day - the horizontal azimuth - pan axis, and throughout the year - the vertical altitude - tilt axis.
- Light sensor Module with four phototransistors, resistors connector block and cable.
- Control - We read the sensor values and use an algorithm to give the direction of movement required in order to balance and fix position aligned to the barrycenter of the sun. Then programming the output to the motors on each axis of the frame.
- Output - A motor on each axis of the machines' structure mechanically moves and positions the receiver to align facing the panel at 90° to the angle of the lightsource with a reasonable degree of accuracy. - 1-2°
- Mechanical Structure - The design will have two axis of movement;
150-180° daily - azimuth - horizontal axis.
57° + for yearly positioning - altitude - vertical axis.
- It must support a solar panel, electronics, motors and actuators. Be stable enough to withstand weather and environmental conditions, and be relatively cheap and easy to construct and assemble.
What processes will be used?
I will be using cutting tools such as the horizontal pneumatic band saw to cut my frame sections to size. I intend to fabricate my own hinge blocks and plates needed to fix the frame. although I am also considering purchasing cast metal parts for their overall strength and intergrity.
I will be testing the validity and strenght of 3D printed fixtures, fittings and hinge sections to assemble the frame parts of the structure.
I have experimented with both 3D printing and laser cutting to test gears and drive mechanisms, although time restraints and the complexities in the design of these parts has resulted in my choosing to use strong actuator motors with integrated reduction gearing.
Tasks to be completed?
- Design main IC control board - Eagle - Mill and Stuff board with components. Adapt an existing arduino style board for my purposes.
- Make the light sensor module cabling and connectors, as my Input.
- Make/Test drive and gear train, selecting the most valid option; fitting a Nema 17 motor - with Pulley/Chain/Worm/Planetary...or buying pre-fabricated motor with gearbox built in, or a linear actuator sealed servo type motor unit.
- Make the frame in two or more sections, the panel mount the base mount and hinges and linkages.
- Test mechanical motion add motors and electronics, Program - Test and Document.
- Design weather proof custom housing.
- Stylise and personalise - branding and impact.
- Add an Interface for control and monitoring.
- Add network capability to send and receive data and design application for control and monitoring interface.
- Make final presentation - Include both a project slide board and a video presentation. Feedback and draw conclusions.
What questions need to be answered?
- Which type of motors to select, buy - and integrate into my design
- How to make a decent high torque low speed gear reduction integrating a planetary or worm drive (or using a chain or pulley)
- Which material to use for frame construction
- Scaling and size according to above components and the intended panel size and overal budget restrictions.
What is the schedule?
We now have approximately two weeks construction time in the lab, and a further week before our final assesment. I will be concentrating first on my electronics and also the choice and specification of mechanical systems for my design, and then move forward with fabrication of the frame and testing of the mechanical motion and the programming and control of my electrical parts. Finally if there is time I will think about extra options such as adding networking and interfacing tools, or even remote control features.
How will it be evaluated?
The project will principally be evaluated on our resolving a final design, and building a prototype that actually works. The documentation provided throughout the pages of this website will reflect the different stages and processes involved, how I came to the conclusions that I did and what I have learned along the way. We will also include a movie and slideshow showing the development and presentation of our final project. All supporting material, and original files are included for reference
