Last edited: 16 May 2018
Solar box cookers and solar panel cookers normally do not need to be turned to follow the sun unless you are cooking beans or an especially large amount of food, or if you are cooking on a day where sunlight is not optimal. They may need to be turned once over a three- or four-hour cooking period. However, parabolic solar cookers require reorientation with the sun much more often. If tracking the sun is necessary, some of the ideas below will serve this purpose.
When designing tracking systems, it can useful to determine the annual movement of the sun for various locations. Besides annual range, this useful tool also gives real-time sun information for a specific location. Suncalc.org
The 2016 Edition of the Solar Electricity Handbook also offers a convenient visual tool to calculate the sun's position in virtually all cities around the globe. It can be found at: Solar Angle Calculator
- May 2018: Dr. Paul Sallis Senior Lecturer in Environmental Engineering reports: Concentrating Solar Power (CSP) devices such as solar cookers benefit greatly from accurate solar tracking, but this feature is usually too costly to apply commercially. This is because active solar trackers often employ optical sensors, microprocessors, and electromechanical devices to enable accurate alignment of the collector with the sun throughout the day. Simpler systems are possible whereby thermally responsive materials such as shape memory alloys (SMA) provide the mechanical force to drive the tracking movement, however, these materials are still costly and are not sustainable in many countries. Research at Newcastle University has shown that responsive materials such as hygromorphic composites (HC) can generate significant useful mechanical force that can be utilised in a passive actuator to achieve mechanical tracking of simple solar cookers or other CSP. These HC materials give predictable and consistent time-dependent responses which means they act as mechanical clocks and need no feedback control from sensors to achieve accurate solar tracking, the required rotation of 15 degrees per hour simply being achieved by an adjustable mechanical linkage to the rotation axis of the solar collector (e.g. solar cooker). There is considerable scope for this research to be developed further, with a partner from the solar cooking industry, into a low-cost high-performance solar cooker for conventional applications. However, it would also open up new opportunities to use such a device for household-level disinfection of drinking water (boiling). This is particularly relevant in low and middle-income countries where simple sustainable technologies are needed to deal with waterborne pathogens in untreated drinking water.
- September 2017: Another approach to stay oriented to the sun - Researchers working at the Instituto de Energías Renovables in Mexico have developed a version of a solar box cooker offering an increased solar tracking positioning capability. This feature decreases the number of times the cooker needs to be reoriented to maintain maximum exposure to the sun. More information... - (English version)
Mechanical tracking systems
Simply Solar provides explanation of their various tracking systems at Scheffler tracking systems. The mechanical system incorporates a clockwork mechanism, and often uses recycled bicycle parts. It is run by a weight and controlled by a pendulum. Resetting the reflector back from the evening position to the morning position is done by hand. They also offer photovoltaic options as well.
Programmable tracking systems
Still in its infancy, programmable tracking systems are being developed with software to not only rotate the reflector to maintain maximum exposure to the sun, but also to control cooking time and desired temperatures. One example of an auto tracking and monitoring system is the SolarCue system. Another is the Raspberry Pi: Solrmatic, but there are a range of such programmable sun trackers.
Photovoltaic tracking systems
A clever system has been developed by several designers, which uses two photovoltaic panels configured to maintain an even balance of power to a small electrical turntable motor. Typically, the required photovoltaic panels are fairly small and are placed side by side, but at slightly different angles to face the sun. As the sun moves across the sky, one panel will begin to receive less direct sunlight.
The resulting electrical imbalance causes the dominant panel to engage the motor. The turntable will rotate until both photovoltaic panels face the sun equally and the motor disengages. The simple system can be fairly lightweight for rotating a box or panel cooker. However, a larger parabolic solar cooker, which will benefit the most from a good tracking system, will require a stronger motor and larger panels to rotate the cooker.
More information about the system can be found at DIY solar tracking system
Tracking for the HotPot solar cooker
Most are familiar with the HotPot, a fine quality cooker. It does an excellent job of representing a solar cooker as a desirable appliance. However, the original design was created for use in tropical or semi-tropical areas bounded by the Tropic of Cancer (23.5° N) and the Tropic of Capricorn (23.5° S). The reflectors have been oriented for a more overhead sun position, which limits the cooking time in temperate locations to a 2- to 4-hour window. The following article talks more about this issue. The author has been working on a tilting base mechanism to allow the reflectors to pick up early and late day sun. However, it may be a better idea to supplement the HotPot reflectors with a windshield shade tipped forward and wrapped behind the cooker to catch the early and late day sun, as the pot and glass enclosure are really not suited for non-level conditions. Details on this tracking design here.
The Solrmatic is a programmable turntable system intended to provide more control over when and how often a solar cooker needs to be reoriented with the sun. It can work with many existing manufactured or homemade solar box cookers and solar panel cookers when they are placed on the turntable.
The Solrmatic features thermostats, time delay, timed cooking, and web monitoring, allowing you to cook almost everything you normally cook in a traditional oven. The Solrmatic has cooked leg of lamb, brisket, veggies, bread, cookies, bacon, and even dehydrated apples.
Articles in the media
- January 2017: The solar cooker that seeks its own place in the sun - The Guardian
- November 2015: Advances in getting solar onto the grid, and into the home - eNCA
- January 2018: Beam Steering Lens Arrays for Solar Cooking (Slides, Paper) - Håkon J Dugstad Johnsen, et al
Audio and video
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Low-tech solar tracking
- Façade Solar Concentrator
- Ideas for low-tech solar tracking
- Nichols Tracking Solar Cooker
- Solar and thermal calculations
- Sun Switch
- Super Solar Tracker for Solar Ovens
- Tracking Solar Accumulating Barbecue
- Low Cost LM339 DIY Solar Tracker Circuit
- Build Your Own Solar Oven With Automatic Sun Tracking - Treehugger
- Study and simulation of concentrating irradiance in box solar cooker with tracking reflectors - F. Yettou, B. Azoui, A. Malek, and A. Gama
- Simple solar tracker on Instructibles.com
- Redirecting Sunlight with Polar Tracking in Developing Countries… and Elsewhere - Pete Schwartz
- Cuisson Solaire Innovante: Mécanisme suivi de trajectoire solaire permettant le guidage d’une parabole - (English version)
- DIY photovoltaic solar tracking system
- Solar Water Boiler with Tracking System - Yousif Abakr
- Scheffler tracking systems
- A parabolic solar cooker with automatic two axes sun tracking system
- Solar Tracking With A Box-Style Cooker - Jim Thomasson
- Readymade Solar Oven Trackers available for purchase at: www.solaroventrackers.com
- Solar Oven Trackers - Small Power Systems
- French: Pisteurs pour four solaire
- Appropedia heliostats article
- LightManufacturing Systems heliostats (commercial) and Solar Manufacturing systems
- ↑ Prinsloo, Gerro; Dobson Robert. (2015). Solar Tracking: High precision solar position algorithms, programs, software and source-code for computing the solar vector, solar coordinates & sun angles in Microprocessor, PLC, Arduino, PIC and PC-based sun tracking devices or dynamic sun following hardware (3rd ed.) South Africa. ISBN 978-0-620-61576-1. Retrieved 14 March 2015.