Hot Spot Concentrating Dish
A Better Focus Company
The Hot Spot Concentrating Dish is an aluminium plate that catches solar energy and concentrates it to a spot of highly concentrated energy that can be easily directed onto any cooking surface.
The Hot Spot Concentrating Dish is a 114 cm (45 in) diameter of highly-reflective aluminium plate that catches sun’s radiant energy and concentrates it to a 10 cm (4 in) to 15 cm (6 in) diameter spot of highly concentrated energy. This energy is easily directed onto any cooking surface. It boils 1,36 litres (48 oz) of water in 15 minutes at 900 W/m2 sunlight intensity and up to 538 ºC (1000 ºF) temperatures are easily achievable on a sunny day.
The reflective film is deformed by applying a vacuum with a simple hand pump to the inside of the dish to achieve a concave shape. Slight adjustments of the dish position are required every 5 minutes so as to follow the sun’s position. The food needs to be elevated, and sunglasses are required when using the dish.
The Hot Spot Concentrating Dish is designed and manufactured by A Better Focus Company which is located in Massillon, Ohio, USA.
Internationally available by purchase online.
A Better Focus Co. The company is looking for qualifying NGOs and other organizations that promote the use of solar cooking in developing countries.
Only available in the A Better Focus co. webpage for 280 USD.
SolSource Solar Cooker from One Hearth Designs, SuniCook from SolSuffit, and GoSun Solar Cooker Sport from GoSun Solar/Applied Sunshine LLC.
Goal 7: Ensure access to affordable, reliable, sustainable and modern energy for all.
Households especially for roasting, boiling and baking.
The technology is suitable for mass production, but current sales volumes are still a few per month. Small communities with previous proper training could manufacture the technology as manufacturing complexity is low.Interview with manufacturer
Few Hot Spot Concentrating Dishes per month is the sales volume (exact number not specified), and most of are shipped to the US. Interview with manufacturer
Whether the stove is forced draft or passive
The power output of the cooker
The maximum temperature the stove can reach
The capacity of the pot the stove can accommodate
The volume of the oven
The pot type(s) the stove accommodates
The amount of time it takes to bring XL of water to a boil; Format: X mins per X L
Design specification includes the dish, a high-quality reflective film, hand pump vacuum (for evacuating the cavity formed between the reflective film and dish), a tripod with one telescoping leg (for elevation adjustment).
Mirror Diameter: 114 cm (45 in)
Reflective Surface: Aluminized Mylar Film
Reflective Area: 0,33 m3 (11.5 cubic ft.)
Weight: from 3.6 kg (8 lbs) to 4,5 kg (10 lbs);depending on configuration
A plastic lined cardboard film cover is provided to avoid punctures during handling, and also to prevent soiling of the reflective film.
Not available for protecting the product patent.Interview with manufacturer
The product comes along with instruction manual. View Frequently Asked Questions or contact the manufacturer.
The reflective film is replaceable, but may not be available in some regions as it requires special fixtures.Interview with manufacturer
This product has a 1-year warranty from date of shipment. With proper care, the product can last up to 10 years. The product is intended to be brought inside after use. Most users hang them up on a wall. A Better Focus co. is currently testing a new film suitable for continuous use outdoors within an estimated lifecycle of 10 years. This new film is, however, more expensive. Interview with manufacturer
Research is on-going for a larger focusing heliostat dish for power generation applications, with several prototype dishes constructed and tested. A 4-dish tracking system has been designed, and a 1/4 scale model constructed and tested. View performance data here. Research efforts have focused on these three areas:
1.Improving focusing accuracy: improved film characterization techniques have improved concentrations on the 1.2m (4 ft) diameter dishes from 130 suns to over 600 suns.
2.Developing a lightweight and cost-effective sun-tracking structure: operational for thermal testing purposes.
3.Weatherability and survival in high wind: the ¼ scale model has survived heavy snow events without damage.
For further information about the performance targets view “Pursuing Best Cost Concentration-Latest developments, including 1/4 scale model of dish-thermal system” in the events section.
The dish has been successfully tested to -6.7 ºC (20 ºF).
Point Focus Focal Length: Variable from 3 m (10 ft) to 6 m (20 ft)
Point Focus Minimum Focal Area: 10.16 cm (4 in)
Concentration: Equivalent of 130 suns
Time to Boil: 1.36 litres (48 oz.) of water in 15 minutes (at 900 W/m2 sunlight intensity)
Vacuum Hold Time: Minimum of 2 hours- always cover dish when not in use
Maximum Heat Flux: 454 ºC (850 ºF)
Testing only conducted by the manufacturer.Interview with the manufacturer
Safety notes: Always wear sunglasses when using the dish and do not stare at the hot spot for extended periods. Never leave the dish unattended to prevent accidental fires. Hot cooking surfaces can potentially burn. Replace cover or relieve the vacuum.
The dish cannot be stored outdoors. The product has one year warranty from date of shipment. Damage to the reflective film is not covered by the warranty.Interview with manufacturer
A Better Focus Company also sells cooking accessories as Tea Kettle for Pole Mount, 2 pegboard brackets for pole mount, insulated pan with heat diffuser plate, cast iron Omlette pan and inverted ovens (including temperature gage, internal food basket), inverted ovens pole mount, inverted oven mount to 2-dish tracker. An umbrella stand and pole for mounting food, an extra hand vacuum pump and additional sunglasses can also be ordered.
There is no academic research on this specific product, however, this paper presents a review of technologies for solar cooking:
Yettou, F., et al. Solar cooker realizations in actual use: An overview. Renewable and Sustainable Energy Reviews. Volume 37. Pages 288-306. Sept 2014.
No Interview with manufacturer
Three types of testing fixtures where used by A Better Focus co., to evaluate the technology:Interview with manufacturer
a) Concentration ratio: Divide the 114 cm (45 in) aperture of the reflective dish by the size of the concentrated spot 5-10 cm (2-4 in), yields a concentration ratio of between 11 and 22.
b) Maximum temperature test: An insulated 15 cm (6 in) diameter pot, with a copper target inside that has a type K thermocouple attached. Max. temperatures developed approach 700 ºC (1300 ºF).
c) Total power developed by heating water from ambient temperature to over 80 ºC (176 ºF). This test was developed by the American Society of Agricultural and Biological Engineers.
A Better Focus Company has organized and participated in several events to show their products. View more information here.
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