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10 tips for cooking with a solar cooker

If you are looking to make changes in order to live a more sustainable lifestyle, harnessing the power of the sun for cooking is a fun idea. Zoë Williams has experimented with a range of solar cookers and techniques. We approached her for some of her top tips.

Solar cooking uses heat from the sun to cook food. Mirrors reflect sunbeams to the cooking area, to get enough heat in one place. Some of the benefits include zero cooking emissions (because no fuel or electricity is needed), and being able to cook on a hot day without heating up the house. Solar cooking could help to reduce deforestation in places where people rely on firewood for cooking. 

There are four main types of cooker. Box and panel cookers can be used to cook any type of food that a slow cooker can handle. Slow cooking also has the advantage of retaining more nutrients. Typical temperatures on a sunny day in Britain might be 120°C in the centre of a box oven, and 100°C for a panel cooker (although it depends on various factors such as the size of the reflectors, and the volume of food). Zoë says "The highest  we've recorded at the top of our box oven was 160°C!"

Panel cookers, made from reflective cardboard, are simple and cheap (from £10). Their performance will depend especially on the cooking vessel used. 

Evacuated tube cookers will get hotter (they can reach around 240°C), and they retain the heat better due to good insulation. They're well suited to the varying British weather, as they will stay hot for a while if there's a cloudy spell. The volume of my tube cooker is small though, compared to the solar box oven.

Parabolic cookers get so hot that you can fry with them. A disadvantage with this type is that they cool quickly when the sun goes in.

Whichever method you choose, it is great fun cooking with energy directly from the sun.

For the best results, try Zoë's top tips:

  1. Use a black pot, as black absorbs heat from the sun more effectively.
  2. If using a panel cooker, put the pot inside a clear heat-resistant plastic bag which will provide insulation like a greenhouse. Or search online for instructions on making a jar-in-jar heat trap.
  3. If using a pot, use a lid to keep the heat in. This is also a good energy saving tip when cooking with a hob.
  4. Resist checking the food too frequently as it takes about ten minutes to heat up again when disturbed.
  5. It is important not to put frozen food into an evacuated tube cooker as this can cause it to crack. A box oven will be fine with frozen food, but it's better to give it time to thaw first.
  6. Keep an eye on the weather forecast to catch the best days for solar cooking. On days without full sunshine, there may still be spells with enough sun, especially if you have an evacuated tube cooker. It's even possible to cook on a clear winter's day. We heated up a meal on the shortest day of the year.  
  7. For maximum temperatures, reposition the cooker every half an hour or so to follow the sun. If you prefer ease of use, you can position the cooker slightly ahead of the sun, or even set it up in the morning, positioned for midday.
  8. Chop food into smaller pieces for faster cooking.
  9. If you like making things, you can even build a solar cooker from scratch. There are many designs online – search for 'solar cooker plans'. The simplest only take about an hour to make.
  10. As with any cooking, don't forget about safety. Many people are surprised that pots get hot enough to burn. Wear oven gloves and explain the dangers to children. If you want to cook meat or poultry, make sure you reach safe minimum temperatures in the centre of the food  – don't expect meat to be cooked on a cloudy day.

Zoë Williams will be hosting a free open home event in Faringdon on Sat 24 Sep where solar cooking equipment will be on display.

The Williams family's home is one of some 50 refurbished Victorian, Edwardian and post-war properties that will open across the UK this September as part of SuperHome Open Days. SuperHomes are older homes refurbished by their owners for greater comfort, lower bills and fewer carbon emissions – at least 60% less!

Zoë Williams (left) demonstrating an evacuated tube cooker

Baking with a box solar cooker  


Cooking peppers with a box solar cooker

Various solar cookers in Portugal, showing a panel cooker on the right, with jar-in-jar heat traps

Photos: SuperHomes, image of cookers in Portugal courtesy of Bernhard Müller

More information about Energy Saving and Renewable Energy on YouGen.

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